Lowering Miners' Exposure to Respirable Crystalline Silica and Improving Respiratory Protection

Published date13 July 2023
Record Number2023-14199
Citation88 FR 44852
CourtLabor Department,Mine Safety And Health Administration
SectionProposed rules
Federal Register, Volume 88 Issue 133 (Thursday, July 13, 2023)
[Federal Register Volume 88, Number 133 (Thursday, July 13, 2023)]
                [Proposed Rules]
                [Pages 44852-45019]
                From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
                [FR Doc No: 2023-14199]
                [[Page 44851]]
                Vol. 88
                Thursday,
                No. 133
                July 13, 2023
                Part IIDepartment of Labor-----------------------------------------------------------------------Mine Safety and Health Administration-----------------------------------------------------------------------30 CFR Parts 56, 57, 60, et al.Lowering Miners' Exposure to Respirable Crystalline Silica and
                Improving Respiratory Protection; Proposed Rule
                Federal Register / Vol. 88 , No. 133 / Thursday, July 13, 2023 /
                Proposed Rules
                [[Page 44852]]
                -----------------------------------------------------------------------
                DEPARTMENT OF LABOR
                Mine Safety and Health Administration
                30 CFR Parts 56, 57, 60, 70, 71, 72, 75, and 90
                [Docket No. MSHA-2023-0001]
                RIN 1219-AB36
                Lowering Miners' Exposure to Respirable Crystalline Silica and
                Improving Respiratory Protection
                AGENCY: Mine Safety and Health Administration (MSHA), Department of
                Labor.
                ACTION: Proposed rule; request for comments; notice of public hearings.
                -----------------------------------------------------------------------
                SUMMARY: The Mine Safety and Health Administration (MSHA) proposes to
                amend its existing standards to better protect miners against
                occupational exposure to respirable crystalline silica, a carcinogenic
                hazard, and to improve respiratory protection for all airborne hazards.
                MSHA has preliminarily determined that under the Agency's existing
                standards, miners at metal and nonmetal mines and coal mines face a
                risk of material impairment of health or functional capacity from
                exposure to respirable crystalline silica. MSHA proposes to set the
                permissible exposure limit of respirable crystalline silica at 50
                micrograms per cubic meter of air ([micro]g/m\3\) for a full shift
                exposure, calculated as an 8-hour time-weighted average, for all
                miners. MSHA's proposal would also include other requirements to
                protect miner health, such as exposure sampling, corrective actions to
                be taken when miner exposure exceeds the permissible exposure limit,
                and medical surveillance for metal and nonmetal miners. Furthermore,
                the proposal would replace existing requirements for respiratory
                protection and incorporate by reference ASTM F3387-19 Standard Practice
                for Respiratory Protection. The proposed uniform approach to respirable
                crystalline silica occupational exposure and improved respiratory
                protection for all airborne hazards would significantly improve health
                protections for all miners and lower the risk of material impairment of
                health or functional capacity.
                DATES: Written comments. Written comments, including comments on the
                information collection requirements described in this preamble, must be
                received or postmarked by midnight Eastern Time on August 28, 2023.
                 Public Hearings. MSHA will hold two public hearings on August 3,
                2023 in Arlington, Virginia and August 21, 2023 in Denver, Colorado.
                For more information on the public hearings, see SUPPLEMENTARY
                INFORMATION.
                ADDRESSES: All submissions must include RIN 1219-AB36 or Docket No.
                MSHA-2023-0001. You should not include personal or proprietary
                information that you do not wish to disclose publicly. If you mark
                parts of a comment as ``business confidential'' information, MSHA will
                not post those parts of the comment. Otherwise, MSHA will post all
                comments without change, including any personal information provided.
                MSHA cautions against submitting personal information.
                 You may submit comments and informational materials, clearly
                identified by RIN 1219-AB36 or Docket Id. No. MSHA-2023-0001, by any of
                the following methods:
                 Federal E-Rulemaking Portal: https://www.regulations.gov. Follow
                the online instructions for submitting comments.
                 Email: [email protected]. Include ``RIN 1219-AB36'' in the
                subject line of the message.
                 Regular Mail: MSHA, Office of Standards, Regulations, and
                Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia
                22202-5450.
                 Hand Delivery or Courier: MSHA, Office of Standards, Regulations,
                and Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia,
                between 9:00 a.m. and 5:00 p.m. Monday through Friday, except Federal
                holidays. Before visiting MSHA in person, call 202-693-9440 to make an
                appointment. Special health precautions may be required.
                 Facsimile: 202-693-9441. Include ``RIN 1219-AB36'' in the subject
                line of the message.
                 Information Collection Requirements. Comments concerning the
                information collection requirements of this proposed rule must be
                clearly identified with ``RIN 1219-AB36'' or ``Docket No. MSHA-2023-
                0001,'' and sent to MSHA by one of the methods previously explained.
                 Docket. For access to the docket to read comments and background
                documents, go to https://www.regulations.gov. The docket can also be
                reviewed in person at MSHA, Office of Standards, Regulations, and
                Variances, 201 12th Street South, Arlington, Virginia, between 9 a.m.
                and 5 p.m. Monday through Friday, except Federal holidays. Before
                visiting MSHA in person, call 202-693-9440 to make an appointment.
                Special health precautions may be required.
                 Email Notification. To subscribe to receive an email notification
                when MSHA publishes rulemaking documents in the Federal Register, go to
                https://public.govdelivery.com/accounts/USDOL/subscriber/new.
                FOR FURTHER INFORMATION CONTACT: S. Aromie Noe, Director, Office of
                Standards, Regulations, and Variances, MSHA, at:
                [email protected] (email); 202-693-9440 (voice); or 202-693-9441
                (facsimile). These are not toll-free numbers.
                SUPPLEMENTARY INFORMATION:
                 MSHA will hold two public hearings to provide industry, labor, and
                other interested parties with an opportunity to present oral
                statements, written comments, and other information on the proposed
                rule. The public hearings will begin at 9 a.m. local time and end after
                the last presenter speaks on the following dates:
                ------------------------------------------------------------------------
                 Date Location Contact number
                ------------------------------------------------------------------------
                August 3, 2023.............. Mine Safety and Health 202-693-9440
                 Administration, 201 12th
                 Street South, Room 7W202,
                 Arlington, VA 22202.
                August 21, 2023............. Denver Federal Center, 202-693-9440
                 Building 25 Lecture Hall,
                 West 6th Avenue and
                 Kipling Street, Denver,
                 CO 80225.
                ------------------------------------------------------------------------
                 The public hearings will begin with an opening statement from MSHA,
                followed by an opportunity for members of the public to make oral
                presentations. Speakers and other attendees may present information to
                MSHA for inclusion in the rulemaking record. The hearings will be
                conducted in an informal manner. Formal rules of evidence or cross
                examination will not apply.
                 A verbatim transcript of each of the proceedings will be prepared
                and made a part of the rulemaking record. Copies of the transcripts
                will be available to the public. MSHA will make the transcript of the
                hearings available at http://www.regulations.gov and on MSHA's website
                at https://arlweb.msha.gov/currentcomments.asp.
                 MSHA will accept post-hearing written comments and other
                appropriate information for the record from any interested party,
                including those not presenting oral statements, received by
                [[Page 44853]]
                midnight (Eastern Time) on August 28, 2023.
                 Pre-registration is not required to attend the hearings. Interested
                parties may attend the hearings virtually or in person. Interested
                parties who intend to present testimony at the hearings are asked to
                register in advance on MSHA's website (http://www.msha.gov). Speakers
                will be called in the order in which they signed up. Those who do not
                register in advance will have an opportunity to speak after all those
                who pre-registered have spoken. You may submit hearing testimony and
                documentary evidence, identified by docket number (MSHA-2023-0001), by
                any of the methods previously identified. Additional information on how
                to access the public hearings will be posted when available at https://www.msha.gov/regulations/rulemaking.
                 The preamble to the proposed standard follows this outline:
                I. Introduction
                II. Request for Comments
                III. Background
                IV. Existing Standards and Implementation
                V. Health Effects Summary
                VI. Preliminary Risk Analysis Summary
                VII. Section-by-Section Analysis
                VIII. Technological Feasibility
                IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory
                Alternatives
                X. Initial Regulatory Flexibility Analysis
                XI. Paperwork Reduction Act
                XII. Other Regulatory Considerations
                XIII. References Cited in the Preamble
                XIV. Appendix
                Acronyms and Abbreviations
                COPD chronic obstructive pulmonary disease
                ESRD end-stage renal disease
                FEV forced expiratory volume
                FVC forced vital capacity
                L/min liter per minute
                mg milligram
                mg/m\3\ milligrams per cubic meter
                mL milliliter
                [micro]g/m\3\ micrograms per cubic meter
                MNM metal and nonmetal
                NMRD nonmalignant respiratory disease
                PEL permissible exposure limit
                PMF progressive massive fibrosis
                RCMD respirable coal mine dust
                REL recommended exposure limit
                SiO2 silica
                TB tuberculosis
                TLV[supreg] Threshold Limit Value
                TWA time-weighted average
                I. Introduction
                 With the passage of the Federal Mine Safety and Health Act of 1977
                (Mine Act), Congress declared that ``the first priority and concern of
                all in the coal or other mining industry must be the health and safety
                of its most precious resource--the miner[.]'' 30 U.S.C. 801(a). In
                furtherance of that clear guiding principle, this proposed rule
                promotes MSHA's mission and statutory mandate to prevent death,
                illness, and injury from mining and promote safe and healthful
                workplaces for U.S. miners. This proposal provides the public with the
                opportunity to comment on the Agency's proposed uniform and streamlined
                regulatory approach to lowering miners' exposure to respirable
                crystalline silica and improving respiratory protection.
                 Exposure to silica dust causes adverse health effects, including
                silicosis (acute silicosis, accelerated silicosis, simple chronic
                silicosis, and progressive massive fibrosis (PMF)), nonmalignant
                respiratory diseases (NMRD) (e.g., emphysema and chronic bronchitis),
                lung cancer, and renal diseases. Each of these effects is chronic,
                irreversible, and potentially disabling or fatal. Silica dust is
                generated in most mining activities, including cutting, sanding,
                drilling, crushing, grinding, sawing, scraping, jackhammering,
                excavating, and hauling materials that contain silica, and is found in
                all mines--underground and surface metal and nonmetal (MNM) and coal
                mines. In a mining context, silica exposures may occur in respirable
                dust together with exposures to other airborne contaminants and
                combustion biproducts.
                 MSHA's existing standards, established in the early 1970s, help
                protect miners from the most dangerous levels of exposure to respirable
                crystalline silica. However, since their promulgation, scientific
                understanding of respirable crystalline silica toxicity has advanced,
                and the National Institute for Occupational Safety and Health (NIOSH)
                has recommended a respirable crystalline silica exposure level of 50
                [micro]g/m\3\ for workers. In 2016, the Occupational Safety and Health
                Administration (OSHA) established a permissible exposure limit (PEL) of
                50 [micro]g/m\3\ in many industry sectors that it regulates.
                 To provide miners with exposure limits consistent with workers in
                other industries and NIOSH's recommendation, and to improve miners'
                health, MSHA proposes to lower its existing exposure limits to 50
                [micro]g/m\3\ for respirable crystalline silica in MNM and coal mines.
                MSHA considered exposure limits below 50 [micro]g/m\3\. However, MSHA
                believes, based on a review of the Agency's available silica sample
                data, that an exposure limit of 25 [micro]g/m\3\ may not be achievable
                for all mines. The proposed PEL would be expressed as a full-shift
                exposure, calculated as an 8-hour time-weighted average (TWA).
                Importantly, a uniform proposed PEL for all mines would make compliance
                simpler--especially for coal mines by eliminating the existing
                respirable dust standard when quartz is present.
                 To meet the requirements of the proposed PEL, mine operators would
                have to implement engineering controls, followed by administrative
                controls if supplementary protection is needed. Engineering controls,
                which are most effective, are designed to remove or reduce the hazard
                at the source and could include the installation of proper ventilation
                systems, use of water sprays or wetting agents to suppress airborne
                contaminants, installation of machine-mounted dust collectors to
                capture respirable crystalline silica and other contaminants, and the
                installation of control booths or environmental cabs to enclose
                equipment operators. Administrative controls, which are often less
                effective than engineering controls, are designed to change the way
                miners work. One example would be ensuring that miners safely clean
                dust off their work clothes so that they are not exposed to respirable
                dust after their shift ends.
                 MSHA's proposed rule would further protect all miners by requiring
                exposure sampling and corrective actions when miners' exposures exceed
                the proposed PEL, as well as periodic sampling when miners' exposure
                levels meet or exceed the proposed action level. The proposed rule also
                includes medical surveillance requirements for MNM miners (medical
                surveillance requirements already exist for coal miners). Proposed
                medical examinations would include chest X-rays, spirometry, symptom
                assessment, and occupational history and would be provided at no cost
                to the miner.
                 Finally, the proposed rule would incorporate by reference an
                updated respiratory protection standard, ASTM F3387-19, ``Standard
                Practice for Respiratory Protection'' (ASTM F3387-19), for respirable
                crystalline silica and all other regulated airborne contaminants. This
                voluntary consensus standard represents up-to-date advancements in
                respiratory protection technologies, practices, and techniques,
                including proper selection, use, and maintenance of respirators. The
                proposed incorporation of ASTM F3387-19 by reference would better
                protect all miners from airborne hazards. However, respiratory
                protection should only be relied upon as an exposure control measure in
                limited situations and on a temporary basis, and to supplement
                engineering controls, followed by administrative controls.
                 Taken together, all elements of the proposed rule are
                technologically and economically feasible. MSHA's 2014
                [[Page 44854]]
                final rule, Lowering Miners' Exposure to Respirable Coal Mine Dust,
                Including Continuous Personal Dust Monitors (Coal Dust Rule) improved
                health protections for coal miners by lowering exposure limits to
                respirable coal mine dust and establishing sampling requirements that
                included the use of a Continuous Personal Dust Monitor (79 FR 24813,
                May 1, 2014). Coal mine operators have generally achieved compliance
                with the respirable dust standards primarily by implementing or
                adjusting existing engineering controls. Coal mine operators' sampling
                data and MSHA's compliance data show that operators have lowered coal
                miners' exposures to respirable coal mine dust and to respirable
                crystalline silica. Data show that average exposures in coal mines are
                below the proposed PEL of 50 [mu]g/m\3\, and therefore, corrective
                measures would often not be needed. Similarly, for MNM miners, MSHA
                data also show that most exposures to respirable crystalline silica are
                below the proposed PEL. However, at MNM and coal mines where elevated
                exposures are found, operators will be able to reduce exposures to the
                proposed PEL through some combination of properly maintaining existing
                engineering controls, implementing new engineering controls, and
                requiring safe work practices. Mines and laboratories will be able to
                meet exposure monitoring requirements with existing validated and
                widely used sampling and analytical methods. The proposed revision to
                the respiratory protection standard is technologically feasible because
                MSHA's existing respiratory protection requirements for selecting,
                fitting, using, and maintaining respiratory protection include similar
                requirements.
                 MSHA's Preliminary Risk Analysis (PRA) suggests that exposure
                consistent with a lower proposed PEL of 50 [micro]g/m\3\ would deliver
                many health benefits to miners who currently experience exposures above
                the proposed PEL by reducing the likelihood of respirable crystalline
                silica-related diseases. For those miners working only under the
                proposed PEL, MSHA estimates that the proposed rule would result in a
                total of 799 lifetime avoided deaths (63 in coal and 736 in MNM mines)
                and 2,809 lifetime avoided morbidity cases (244 in coal and 2,566 in
                MNM mines) over a 60-year period. MSHA expects full implementation and
                compliance to reduce lifetime mortality risk due specifically to silica
                exposures by 9.5 percent and to reduce silicosis morbidity risk by 41.9
                percent. The latter statistic is particularly important to coal miners
                given surveillance findings noted by the National Academies of
                Sciences, Engineering, and Medicine that severe pneumoconiosis where
                respirable crystalline silica is likely an important contributor is
                presenting in relatively young miners, sometimes in their late 30's and
                early 40's.
                 MSHA's economic analysis estimates that the proposed respirable
                crystalline silica rule would cost an average of $56.1 million per year
                in 2021 dollars at an undiscounted rate, $57.6 million at a 3 percent
                discount rate, and $59.9 million at a 7 percent discount rate. Based on
                the results of the Preliminary Regulatory Impact Analysis (PRIA), MSHA
                estimates that the proposed rule's benefits would exceed its costs,
                with or without discount rates. Monetized benefits are estimated from
                avoidance of 410 deaths related to NMRD, silicosis, ESRD, and lung
                cancer and 1,420 cases of silicosis associated with silica exposure
                over the first 60-year period after the promulgation of the final rule.
                The estimated annualized net benefit is approximately $212.8 million at
                an undiscounted rate, $118.2 million at a 3 percent discount rate, and
                $36.3 million at a 7 percent discount rate.
                 A rule is significant under Executive Order 12866 Section 3(f)(1),
                as amended by E.O. 14094, if it is likely to result in ``an annual
                effect on the economy of $200 million or more or . . . adversely affect
                in a material way the economy, a sector of the economy, productivity,
                competition, jobs, the environment, public health or safely, or State,
                local, or tribal governments or communities.'' The Office of Management
                and Budget has determined that the proposed rule is significant within
                the meaning of E.O. 12866 Section 3(f)(1).
                 The proposed rule would strengthen MSHA's existing regulatory
                framework. It would establish a uniform proposed PEL that provides all
                MNM and coal miners with the same exposure limits for respirable
                crystalline silica consistent with exposure limits that other U.S.
                workers currently receive in non-mining industries. It would update the
                existing respiratory protection standard to require mine operators to
                provide miners with NIOSH-approved respiratory equipment that has been
                fitted, selected, maintained, and used in accordance with recent
                consensus standards. The proposed rule would also include requirements
                for all MNM operators to provide medical surveillance in the form of a
                medical examination regime similar to what coal miners already receive.
                Cumulatively, the proposed provisions would lower miners' risk of
                developing chronic, irreversible, disabling, and potentially fatal
                health conditions, consistent with MSHA's mission and statutory mandate
                to prevent occupational diseases and protect U.S. miners from suffering
                material health impairments.
                II. Request for Comments
                 MSHA requests comments on the proposed rule and all relevant
                issues, including the review and conclusions of the health effects
                discussion, preliminary risk analysis, feasibility analysis,
                preliminary regulatory impact analysis and regulatory alternatives, and
                preliminary regulatory flexibility analysis. While MSHA invites
                comments on any aspect of its proposed rule and related documents, the
                Agency particularly seeks information and data in response to questions
                posed in this section and any other aspect of this proposed rule.
                Instructions for submitting and viewing comments are provided under the
                DATES heading. MSHA will consider all timely comments and may change
                the proposed rule based on such comments.
                 MSHA requests that commenters organize their comments, to the
                extent possible, around the following numbered questions. The Agency is
                interested in receiving responses to the listed questions and any
                information or data supporting the responses.
                Health Effects
                 1. In the standalone, background document entitled ``Health Effects
                of Respirable Crystalline Silica'' and as summarized in Section V.
                Health Effects Summary of this preamble, MSHA has made a preliminary
                determination that miners' exposure to respirable crystalline silica
                presents a risk of material health impairment due to the risk of
                developing silicosis, NMRD, lung cancer, and renal disease, based on
                its extensive review of the health effects literature. MSHA requests
                comments on this preliminary determination and its literature review,
                which draws heavily from the review conducted by OSHA for its 2016
                rulemaking. Are there additional adverse health effects that should be
                included or more recent literature that offers a different perspective?
                MSHA requests that commenters submit information, data, or additional
                studies or their citations. Please be specific regarding the basis for
                any recommendation to include additional adverse health effects.
                Preliminary Risk Analysis
                 2. In the standalone, background document entitled ``Preliminary
                Risk Analysis'' and as summarized in Section VI. Preliminary Risk
                Analysis Summary
                [[Page 44855]]
                of this preamble, MSHA relied on risk models that OSHA used in support
                of its 2016 respirable crystalline silica final rule. Does the context
                of the MSHA rule suggest that the model would benefit from changes? If
                so, please describe both the justification for those changes and the
                likely impact on the final risk estimates. Are there additional studies
                or sources of data that MSHA should consider? What is the rationale for
                recommending the use of these additional studies or data?
                 3. MSHA's risk analysis of lung cancer mortality uses the exposure-
                response model from Miller and MacCalman (2010) instead of Steenland et
                al. (2001a), on which OSHA's risk assessment of lung cancer mortality
                was based. MSHA uses Miller and MacCalman (2010) for several reasons.
                First, it covers coal mining-specific cohort large enough (with 45,000
                miners) to provide adequate statistical power to detect low levels of
                risk, and it covers an extended follow-up period (1959-2006). Second,
                the study provided data on cumulative exposure of cohort members and
                adjusted for or addressed confounders such as smoking and exposure to
                other carcinogens. Finally, it developed quantitative assessments of
                exposure-response relationships using appropriate statistical models or
                otherwise provided sufficient information that permitted MSHA to do so.
                The Agency is requesting comment on MSHA's reliance on the Miller and
                MacCalman (2010) study in assessing lung cancer mortality. Please
                provide any other studies or information that MSHA should take into
                account in determining the risk of lung cancer mortality among miners.
                Technological Feasibility of the Proposed Rule
                 4. As discussed in Section VIII. Technological Feasibility of this
                preamble, MSHA has preliminarily determined that it is technologically
                feasible for mine operators to conduct air sampling and analysis and to
                achieve the proposed PEL using commercially available samplers. MSHA
                has also determined that these technologically feasible samplers are
                widely available, and a number of commercial laboratories provide the
                service of analyzing dust containing respirable crystalline silica. In
                addition, MSHA has determined that technologically feasible engineering
                controls are readily available, can control crystalline silica-
                containing dust particles at the source, provide reliable and
                consistent protection to all miners who would otherwise be exposed to
                respirable dust, and can be monitored. MSHA has also determined that
                administrative controls, used to supplement engineering controls, can
                further reduce and maintain exposures at or below the proposed PEL.
                Moreover, MSHA has preliminarily determined the proposed respiratory
                protection practices for respirator use are technologically feasible
                for mine operators to implement. MSHA requests comments on these
                preliminary conclusions. What methods have you used that proved
                effective in reducing miners' exposure to respirable crystalline silica
                in mining operations? Please explain how those methods were effective
                in reducing miners' exposures. To what extent do existing controls that
                reduce exposure to other airborne hazards (e.g., coal dust, diesel
                particulate matter) already reduce exposures to respirable crystalline
                silica below the proposed PEL? To what extent does the proposed rule
                including the PEL facilitate MSHA's workplace health and safety goals?
                Please provide supporting information, such as quantitative data if
                available.
                 5. MSHA has determined that the proposed medical surveillance
                requirements for MNM are technologically feasible. MSHA requests
                comments on this preliminary conclusion. Please provide supporting
                information, such as quantitative data if available.
                Preliminary Regulatory Impact Analysis and Regulatory Alternatives
                 6. In the standalone background document entitled ``Preliminary
                Regulatory Impact Analysis'' and as summarized in Section IX. Summary
                of Preliminary Regulatory Impact Analysis and Regulatory Alternatives
                of this preamble, MSHA developed estimated costs of compliance with the
                proposed rule and estimated monetized benefits associated with averted
                cases of respirable crystalline silica-related diseases. MSHA requests
                comments on the methodologies, baseline, assumptions, and estimates
                presented in the Preliminary Regulatory Impact Analysis. Please provide
                any data or quantitative information that may be useful in evaluating
                the estimated costs and benefits associated with the proposed rule.
                 7. MSHA considered two regulatory alternatives in developing the
                proposed rule discussed in Section IX. Summary of Preliminary
                Regulatory Impact Analysis and Regulatory Alternatives. In the
                regulatory alternatives presented, MSHA discussed alternatives to the
                proposed PEL, action level, sampling requirements, and semi-annual
                evaluations. MSHA requests comments on these and other regulatory
                alternatives and information on any other alternatives that the Agency
                should consider, including different average working-life spans and
                different average shift lengths. Please provide supporting information
                about how these alternatives could affect miners' protection from
                respirable crystalline silica exposure and affect mine operators'
                costs.
                Initial Regulatory Flexibility Analysis
                 8. As summarized in Section X. Initial Regulatory Flexibility
                Analysis of this preamble, MSHA examined the impact of the proposed
                rule on small mines in accordance with the Regulatory Flexibility Act.
                MSHA estimated that small-entity controllers would be expected to
                incur, on average, additional regulatory costs equaling approximately
                0.122 percent of their revenues (or $1,220 for every $1 million in
                revenues). MSHA is interested in how the proposed rule would affect
                small mines, including their ability to comply with the proposed
                requirements. Please provide information and data that supports your
                response. If you operate a small mine, please provide any projected
                impacts of the proposal on your mine, including the specific rationale
                supporting your projections.
                Scope and Effective Date
                 9. MSHA is proposing a unified regulatory and enforcement framework
                for controlling miners' exposures to respirable crystalline silica for
                the mining industry. MSHA requests comments on this unified regulatory
                and enforcement framework. MSHA requests the views and recommendations
                of stakeholders regarding the scope of proposed part 60, which would
                include all surface and underground MNM and coal mines. MSHA requests
                comments on whether separate standards should be developed for the MNM
                mining industry and the coal mining industry. Please provide supporting
                information.
                 10. MSHA is proposing that the final rule would be effective 120
                days after its publication in the Federal Register. This period is
                intended to provide mine operators time to evaluate existing
                engineering and administrative controls, update their respiratory
                protection programs, and prepare to comply with other provisions of the
                rule including recordkeeping requirements. Please provide your views on
                the proposed effective date. In your response, please include the
                rationale for your position.
                [[Page 44856]]
                Definitions
                 11. MSHA requests comments on the proposed action level.
                Stakeholders should provide specific information and data in support of
                or against a proposed action level. Stakeholders should include a
                discussion of how the use of a proposed action level would impact their
                mines, including the cost of monitoring respirable crystalline silica
                above the proposed action level, and other relevant information. Please
                provide supporting information.
                 12. MSHA requests comments on the proposed definition for
                ``objective data.'' Is it appropriate to allow mine operators to use
                objective data instead of a second baseline sample? Please provide
                supporting information.
                Proposed Permissible Exposure Limit
                 13. MSHA is proposing a PEL for respirable crystalline silica of 50
                [mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA for
                MNM and coal miners. MSHA has made a preliminary determination that the
                proposed PEL would reduce miners' risk of suffering material impairment
                of health or functional capacity over their working lives. MSHA seeks
                the views and recommendations of stakeholders on the proposed PEL. MSHA
                solicits comments on the approach of having a standalone PEL and
                whether to eliminate the reduced standard for total respirable dust
                when quartz is present at coal mines. Please provide evidence to
                support your response.
                 14. MSHA is proposing a PEL of 50 ug/m\3\ and an action level of 25
                [mu]g/m\3\ for respirable crystalline silica exposure. Which proposed
                requirements should be triggered by exposure at, above, or below the
                proposed action level? Please provide supporting information.
                Methods of Compliance
                 15. MSHA requests comments on the proposed prohibition against
                rotation of miners as an administrative control. Please include a
                discussion of the potential effectiveness of this non-exposure approach
                and its impact on miners at specific mines. Please provide supporting
                information.
                 16. MSHA requests comments on the proposed requirement that mine
                operators must install, use, and maintain feasible engineering and
                administrative controls to keep miners' exposures to respirable
                crystalline silica below the proposed PEL. Please provide supporting
                information.
                Proposed Exposure Monitoring
                 17. MSHA requests comments and information from stakeholders
                concerning the proposed approaches to monitoring exposures, and other
                approaches to accurately monitor miner exposure to respirable
                crystalline silica in MNM and coal mines. Please provide supporting
                information and data.
                 18. MSHA proposes to require mine operators to collect a respirable
                crystalline silica sample for a miner's regular full shift during
                typical mining activities. Many potential sources of respirable
                crystalline silica are present only when the mine is operating under
                typical conditions. MSHA requests comments on this requirement and
                whether to specify environmental conditions under which samples should
                be taken to ensure that samples accurately reflect actual levels of
                respirable crystalline silica exposure. In MSHA's experience, for
                example, environmental conditions such as precipitation (e.g., rain or
                snow) or wind could affect the actual levels of respirable crystalline
                silica exposure at miners' normal or regular workplaces throughout
                their typical workday. Please provide supporting information and data.
                 19. MSHA recognizes that some mining facilities operate seasonally
                or intermittently and that cumulative exposures for miners at these
                facilities may be lower than that of miners working at year-round
                operations. MSHA requests comments on the exposure monitoring approach
                under proposed Sec. 60.12, including the frequency of exposure
                monitoring necessary to safeguard the health of miners at seasonal or
                intermittent operations. Please provide supporting information and
                data.
                 20. MSHA is proposing that each mine operator perform baseline
                sampling within 180 days after the rule becomes effective to assess the
                respirable crystalline silica exposure of each miner who is or may
                reasonably be expected to be exposed to respirable crystalline silica.
                MSHA requests comments on this proposed baseline sampling requirement.
                MSHA also requests comment on the ability of service providers used by
                mines such as industrial hygiene suppliers and consultants, and
                accredited laboratories that conduct respirable crystalline silica
                analysis, to meet the demand created by the baseline sampling
                requirements within the proposed timeline. Please include alternative
                approaches that might be equally protective of miners that should be
                implemented for assessing a miner's initial exposure to respirable
                crystalline silica.
                 21. MSHA is proposing a requirement that mine operators
                qualitatively evaluate every 6 months any changes in production,
                processes, engineering controls, personnel, administrative controls, or
                other factors, beginning 18 months after the effective date. MSHA
                requests comments on the timing of the proposed semi-annual evaluation
                requirements, and in particular, whether miners would possibly be
                exposed unnecessarily to respirable crystalline silica levels above the
                PEL due to the gap between the effective date and the proposed
                requirements. Please provide supporting information.
                 22. MSHA has determined that most occupations related to extraction
                and processing would meet the ``reasonably be expected'' threshold for
                baseline sampling. MSHA recognizes that some miners may work in areas
                or perform tasks where exposure is not reasonably expected, if at all.
                MSHA solicits comments on the assumption that most miners are exposed
                to at least some level of respirable crystalline silica, and on the
                proposed requirement that these miners should be subject to baseline
                sampling. Please provide supporting information.
                 23. MSHA is proposing that mine operators would not be required to
                conduct periodic sampling if the baseline sampling result, together
                with another sampling result or objective data, as defined in proposed
                Sec. 60.2, confirms miners' exposures are below the proposed action
                level. MSHA seeks comments on this proposal. Please provide supporting
                information and data.
                 24. MSHA is proposing that mine operators conduct periodic sampling
                within 3 months where the most recent sampling indicates miner
                exposures are at or above the proposed action level but at or below the
                proposed PEL and continue to sample within 3 months of the previous
                sampling until two consecutive samplings indicate that miner exposures
                are below the action level. MSHA solicits comments on the proposed
                frequency for periodic sampling, including whether the consecutive
                samples should be at least 7 days apart. Please provide supporting
                information and data.
                 25. MSHA is proposing that mine operators may discontinue periodic
                sampling when two consecutive samples indicate that miner exposures are
                below the proposed action level. MSHA requests comments on this
                proposal. Please provide supporting information and data.
                 26. MSHA is proposing that mine operators conduct semi-annual
                evaluations to evaluate whether any changes in production, processes,
                engineering controls, personnel, administrative controls, or other
                factors may reasonably be expected to result in
                [[Page 44857]]
                new or increased respirable crystalline silica exposures. Please
                provide comments on this proposal, as well as alternative approaches
                that would be appropriate for evaluating any potential new or increased
                respirable crystalline silica exposures. Please provide supporting
                information and data.
                 27. MSHA is proposing that miners' exposures are measured using
                personal breathing-zone air samples for MNM operations and occupational
                environmental samples collected in accordance with Sec. Sec.
                70.201(c), 71.201(b), or 90.201(b) for coal operations. MSHA requests
                comments on this proposal. Please provide supporting information and
                data.
                 28. MSHA is proposing the use of representative sampling. Where
                several miners perform the same task on the same shift and in the same
                work area, the mine operator may sample a representative fraction of
                miners to meet the proposed exposure monitoring requirements. MSHA
                seeks comments on the use of representative sampling. Please provide
                supporting information and data.
                 29. MSHA is proposing that mine operators use laboratories
                accredited to ISO/IEC 17025 ``General requirements for the competence
                of testing and calibration laboratories,'' where the accreditation has
                been issued by a body that is compliant with ISO/IEC 17011 ``Conformity
                assessment--requirements for accreditation bodies accrediting
                conformity assessment bodies.'' MSHA solicits comments on this
                proposal. Are there additional requirements that should be incorporated
                into this proposal to ensure accurate sample analysis methods? Please
                provide supporting information and data.
                 30. MSHA seeks comments on the proposal that mine operators ensure
                that laboratories evaluate all respirable crystalline silica samples
                using respirable crystalline silica analytical methods specified by
                MSHA, NIOSH, or OSHA. Are there additional requirements that should be
                incorporated into this proposal to ensure accurate sample analysis?
                Please provide supporting information and data.
                 31. MSHA seeks comments and information on mine operator and
                stakeholder experience using NIOSH's rapid field-based quartz
                monitoring (RQM) monitors for determining miners' exposures to
                respirable crystalline silica. Please provide any information and data.
                Proposed Medical Surveillance for Metal and Nonmetal Miners
                 32. MSHA is proposing to require medical surveillance for MNM
                miners. Medical surveillance is already required for coal miners under
                30 CFR 72.100 and has played an important role in tracking the burden
                of pneumoconiosis in coal miners but is not currently required for MNM
                miners. MSHA's proposal would require MNM mine operators to provide
                each miner new to the mining industry with an initial medical
                examination and a follow-up examination no later than 3 years after the
                initial examination, at no cost to the miner. It would also require MNM
                mine operators to provide examinations for all miners at least every 5
                years, which would be voluntary for miners. Is there an alternative
                strategy or schedule, such as voluntary initial or follow-up
                examinations, tying the medical surveillance requirement to miners
                reasonably expected to be exposed to any level of silica or to the
                action level that would be more appropriate for new MNM miners? Should
                the rule make each 5-year examination mandatory? Should the 5-year
                examination be mandatory for coal mine operators as well? Please
                provide data or cite references to support your position.
                 33. MSHA's proposed medical surveillance requirements for MNM
                miners do not include some requirements that are in MSHA's existing
                medical surveillance requirements for coal mine operators in 30 CFR
                72.100. For example, Sec. 72.100 requires coal mine operators to use
                NIOSH-approved facilities for medical examinations. Should MNM
                operators be required to use NIOSH-approved facilities for medical
                examinations? Coal mine operators also are required to submit for
                approval to NIOSH a plan for providing miners with the examinations
                specified. This is because NIOSH administers medical surveillance for
                coal miners with requirements for coal operators, but not MNM
                operators, in NIOSH standards (42 CFR part 37). Should the plan
                requirements be extended to MNM operators? However, the proposed
                requirements also include some requirements for MNM operators that are
                not included for coal operators. For example, the proposed provisions
                require operators of MNM mines to provide MNM miners with periodic
                medical examinations performed by physicians or other licensed health
                care professionals (PLHCP) or specialists including a history and
                physical examination focused on the respiratory system, a chest X-ray,
                and a spirometry test. The proposed rule also requires a written
                medical opinion be provided by the PLHCP or specialist to the mine
                operator regarding the miner's ability to wear a respirator. MSHA seeks
                comment on the differences between the medical surveillance
                requirements for MNM operators in this proposed rule and the existing
                medical surveillance requirements for coal mine operators in Sec.
                72.100. MSHA also seeks comment on how best to collect health
                surveillance data from PLHCPs and specialists to track MNM miners'
                health, for example how to know when pneumoconiosis cases occur. MSHA
                seeks comments on alternative approaches to scheduling periodic medical
                surveillance. MSHA proposes to require operators to keep medical
                surveillance information for the duration of a miner's employment plus
                6 months. The Agency seeks comments on this proposed requirement and on
                any alternative recordkeeping schedules that would be appropriate.
                Please provide supporting information.
                 34. MSHA's proposed medical surveillance requirements for MNM
                miners would require operators of MNM mines to provide miners with
                periodic medical examinations performed by PLHCP or specialists,
                including a history and physical examination focused on the respiratory
                system, a chest X-ray, and a spirometry test. MSHA seeks comment on
                whether use of any new diagnostic technology (e.g., high-resolution
                computed tomography) for the purposes of medical surveillance should be
                used.
                 35. MSHA's proposed medical surveillance requirements would require
                that the MNM mine operator provide a mandatory follow-up examination to
                the miner no later than 3 years after the miner's initial medical
                examination. If a miner's 3-year follow-up examination shows evidence
                of a respirable crystalline silica-related disease or decreased lung
                function, the operator would be required to provide the miner with
                another mandatory follow-up examination with a specialist within 2
                years. For examinations that show evidence of disease or decreased lung
                function, MSHA seeks comment on how, and to whom, test results should
                be communicated.
                 36. MSHA requests comments as to whether the proposed provisions
                should include a medical removal option for MNM miners who have
                developed evidence of silica-related disease that is equivalent to the
                transfer rights and exposure monitoring provided to coal miners in 30
                CFR part 90 (part 90). Under part 90, any coal miner who has evidence
                of the development of pneumoconiosis based on a chest X-ray or other
                medical examinations has the
                [[Page 44858]]
                option to work in an area of the mine where the average concentration
                of respirable dust in the mine atmosphere during each shift to which
                that miner is exposed is continuously maintained at or below the
                applicable standard. Under part 90, coal miners are entitled to
                retention of pay rate, future actual wage increases, and future work
                assignment, shift and respirable dust protection. MSHA seeks comment on
                whether this medical removal option should be provided to MNM miners.
                What would be the economic impact of providing MNM miners a medical
                removal option? Please provide supporting information and data.
                Proposed Respiratory Protection Standard
                 37. MSHA requests comments concerning the temporary, non-routine
                use of respirators and whether there are other instances or occupations
                in which the Agency should allow the use of respirators as a
                supplemental control. Please discuss any impacts on particular mines
                and mining conditions and the cost of air-purifying respirators, if
                applicable. MSHA also solicits comments on the proposed requirement
                that affected miners wear respiratory protection to maintain protection
                during temporary and non-routine use of respirators. Please provide
                supporting information.
                 38. MSHA is proposing to incorporate by reference ASTM F3387-19,
                published in 2019. Whenever respiratory protective equipment is needed,
                mine operators would be required to follow practices for program
                administration, standard operating procedures, medical evaluations,
                respirator selection, training, fit testing, and maintenance,
                inspection, and storage in accordance with the requirements of ASTM
                F3387-19. Beyond these elements, MSHA is proposing to provide operators
                the flexibility to select the elements in ASTM F3387-19 that are
                applicable to their practices of respirator use at their mines. Should
                mine operators have the flexibility to choose the ASTM F3387-19
                elements that are appropriate for their mine-specific hazards because
                the need for respirators may vary due to the variability of mining
                processes, activities, airborne hazards, and commodities mined? What,
                specifically, do you think should factor into the determination of what
                is applicable? MSHA seeks comments on its proposed approach and the
                impact it would have on mine operators and on miners' life and health.
                 39. ASTM F3387-19 identifies a variety of respiratory protection
                practice elements. MSHA proposes to require certain minimally
                acceptable program elements: program administration; standard operating
                procedures; medical evaluations; respirator selection; training; fit
                testing; and maintenance, inspection, and storage. Please comment on
                whether these are the appropriate elements to require, or if there are
                any other elements of ASTM F3387-19 that should be minimally included
                in any respiratory protection program. MSHA also welcomes comments on
                whether it would be appropriate to require the standard in its
                entirety. Please identify those elements that would ensure that
                approved respirators are selected, fitted, used, cleaned, and
                maintained so that the life and health of miners are safeguarded. MSHA
                also seeks data and information on the impact these changes would have
                on mine operators, especially smaller operators. What would be the
                economic impact if all or parts of ASTM F3387-19 were required
                respirator program elements? Please be specific with your response and
                provide details on respirator use at your mine to include information
                and data on mining processes and environmental conditions; level of
                exposures to airborne contaminants; frequency and duration of
                exposures; type and amount of work or physical labor, including
                frequency and duration; and medical evaluation on respirator use, if
                applicable.
                Recordkeeping Requirements
                 40. MSHA is proposing to require recordkeeping for records of
                evaluations, records of samplings, records of corrective actions, and
                written determination records received from a PLHCP. The proposed
                rule's recordkeeping requirements are discussed in the Section-by-
                Section Analysis section of this Preamble. MSHA seeks comment on the
                utility of these recordkeeping requirements as well as the costs of
                making and maintaining these records. Please provide supporting
                information.
                Training Requirements
                 41. MSHA requests the views and recommendations of stakeholders
                regarding whether training requirements for miners should be included
                in proposed part 60. Please provide supporting information and data.
                Conforming Changes
                 42. MSHA requests comments on the proposed conforming changes to
                remove the reduced coal dust standard from 30 CFR and the potential
                impact on coal mines and miners and on whether to retain the reduced
                standard for part 90 miners. Please provide supporting information.
                 43. MSHA is not proposing to adopt a similar approach as the OSHA
                Table 1 for the construction industry, where MSHA would prescribe
                specific exposure control methods for task-based work practices when
                working with materials containing respirable crystalline silica. See 29
                CFR 1926.1153(c)(1). MSHA requests comments on specific tasks and
                exposure control methods appropriate for a Table 1-approach for the
                mining industry that also would adequately protect miners from risk of
                exposure to respirable crystalline silica. Please provide specific
                rationale and supporting information, including data on how such an
                approach would be implemented.
                III. Background
                 The purpose of this proposed rule is to reduce miners' risk of
                developing occupational lung disease and other diseases caused by
                exposure to respirable crystalline silica and to better protect all
                miners from occupational exposure to airborne hazards. In promulgating
                mandatory standards dealing with toxic materials or harmful physical
                agents, MSHA is required to ``set standards which most adequately
                assure on the basis of the best available evidence that no miner will
                suffer material impairment of health or functional capacity . . .'' 30
                U.S.C. 811(a)(6)(A).
                A. Statutory Authority
                 The statutory authority for this proposal is provided by the Mine
                Act under sections 101(a), 103(h), and 508. 30 U.S.C. 811(a), 813(h),
                and 957. MSHA implements the provisions of the Mine Act to prevent
                death, illness, and injury from mining and promote safe and healthful
                workplaces for miners. The Mine Act requires the Secretary of Labor
                (Secretary) to develop and promulgate improved mandatory health or
                safety standards to prevent hazardous and unhealthy conditions and
                protect the health and safety of the nation's miners. 30 U.S.C. 811(a).
                 Congress passed the Mine Act to address these dangers, finding ``an
                urgent need to provide more effective means and measures for improving
                the working conditions and practices in the Nation's coal or other
                mines in order to prevent death and serious physical harm, and in order
                to prevent occupational diseases originating in such mines.'' 30 U.S.C.
                801(c). Congress concluded that ``the existence of unsafe and
                unhealthful conditions and practices in the Nation's coal or other
                [[Page 44859]]
                mines is a serious impediment to the future growth of the coal or other
                mining industry and cannot be tolerated.'' 30 U.S.C. 801(d).
                Accordingly, ``the Mine Act evinces a clear bias in favor of miner
                health and safety.'' Nat'l Mining Ass'n v. Sec'y, U.S. Dep't of Lab.,
                812 F.3d 843, 866 (11th Cir. 2016).
                 Section 101(a) of the Mine Act gives the Secretary the authority to
                develop, promulgate, and revise, as appropriate, mandatory health
                standards to address toxic materials or harmful physical agents. Under
                Section 101(a), standards must protect lives and prevent injuries in
                mines and be ``improved'' over any standard that it replaces or
                revises. Moreover, ``the Mine Act does not contain the `significant
                risk' threshold requirement . . . from the OSH Act.'' Nat'l Mining
                Ass'n v. United Steel Workers, 985 F.3d 1309, 1319 (11th Cir. 2021);
                see also Nat'l Min. Ass'n v. Mine Safety & Health Admin., 116 F.3d 520,
                527-28 (D.C. Cir. 1997) (contrasting the OSH Act at 29 U.S.C. 652 with
                the Mine Act at 30 U.S.C. 811(a) and noting that ``[a]rguably, this
                language does not mandate the same risk-finding requirement as OSHA''
                and holding that ``[a]t most, . . . . [MSHA] was required to identify a
                significant risk associated with having no oxygen standard at all''
                (emphasis in original)).
                 The Secretary must set standards to assure, based on the best
                available evidence, that no miners will suffer material impairment of
                health or functional capacity from exposure to toxic materials or
                harmful physical agents over their working lives. 30 U.S.C.
                811(a)(6)(A). In developing standards that attain the ``highest degree
                of health and safety protection for the miner,'' the Mine Act requires
                that the Secretary consider the latest available scientific data in the
                field, the feasibility of the standards, and experience gained under
                the Mine Act and other health and safety laws. Id. However, MSHA's
                ``duty to use the best evidence and to consider feasibility . . .
                cannot be wielded as counterweight to MSHA's overarching role to
                protect the life and health of workers in the mining industry.'' Nat'l
                Mining Ass'n, 812 F.3d at 866. Instead, ``when MSHA itself weighs the
                evidence before it, it does so in light of its congressional mandate.''
                Id.
                 Section 103(h) of the Mine Act gives the Secretary the authority to
                promulgate standards involving recordkeeping and reporting. 30 U.S.C.
                813(h). In general, section 103(h) requires that every mine operator
                establish and maintain records, make reports, and provide this
                information, if required by the Secretary. Id. Also, section 508 of the
                Mine Act gives the Secretary the authority to issue regulations to
                carry out any provision of the Mine Act. 30 U.S.C. 957.
                 MSHA's proposal to lower the exposure limits for respirable
                crystalline silica and adopt an integrated monitoring approach across
                all mining sectors and to update the existing respiratory protection
                requirements would fulfill Congress' direction by preventing miners
                from suffering material impairment of health or functional capacity
                caused by exposure to respirable crystalline silica and other airborne
                contaminants.
                B. Respirable Crystalline Silica Hazard and Mining
                 Silica is a common component of rock composed of silicon and oxygen
                (chemical formula SiO2), existing in amorphous and
                crystalline states. Silica in the crystalline state is the focus of
                this rulemaking. Respirable crystalline silica consists of small
                particles of crystalline silica that can be inhaled and reach the
                alveolar region of the lungs, where they can accumulate and cause
                disease. In crystalline silica, the silicon and oxygen atoms are
                arranged in a three-dimensional repeating pattern. The crystallization
                pattern varies depending on the circumstances of crystallization,
                resulting in a polymorphic state--several different structures with the
                same chemical composition. The most common form of crystalline silica
                found in nature is quartz, but cristobalite and tridymite may also be
                found in limited circumstances. Quartz accounts for the overwhelming
                majority of naturally occurring crystalline silica. In fact, quartz
                accounts for almost 12 percent of the earth's crust by volume. All
                soils contain at least trace amounts of quartz and it is present in
                varying amounts in almost every type of mineral. Quartz is also
                abundant in most rock types, including granites, sandstones, and shale.
                Moreover, quartz is commonly found in limestone formations, although
                limestone itself does not contain quartz. Because of its abundance,
                crystalline silica in the form of quartz is present in nearly all
                mining operations.
                 Cristobalite and tridymite are formed at very high temperatures and
                are associated with volcanic activity. Naturally occurring cristobalite
                and tridymite are rare, but they can be found in volcanic ash and in a
                relatively small number of rock types limited to specific geographic
                regions. Although rare, exposure to cristobalite occurs when volcanic
                deposits are mined. In addition, when other materials are mined, miners
                can potentially be exposed to cristobalite during certain processing
                steps (e.g., heating silica-containing materials) and contact with
                refractory materials (e.g., replacing fire bricks in mine processing
                facility furnaces). Tridymite is rarely found in nature and miner
                exposure to tridymite is much more infrequent.
                 Most mining activities generate silica dust because silica is often
                contained in the ore being mined or in the overburden (i.e., the soil
                and surface material surrounding the commodity being mined). Such
                activities include, but are not limited to, cutting, sanding, drilling,
                crushing, grinding, sawing, scraping, jackhammering, excavating, and
                hauling materials that contain silica. These activities can generate
                respirable crystalline silica and may therefore lead to miner exposure.
                 Inhaled small particles of silica dust can be deposited throughout
                the lungs. A large number of crystalline silica particles can reach and
                remain in the deep lung (i.e., alveolar region), although some small
                particles are cleared from the lungs. Because respirable crystalline
                silica particles are not water-soluble and do not undergo metabolism
                into less toxic compounds, those particles remaining in the lungs for
                prolonged periods result in a variety of cellular responses that may
                lead to pulmonary disease. The respirable crystalline silica particles
                that are cleared from the lungs can be distributed to lymph nodes,
                blood, liver, spleen, and kidneys, potentially accumulating in those
                other organ systems and causing renal disease and other adverse health
                effects.
                 In the U.S. in 2021, a total of 12,162 mines produced a variety of
                commodities. As shown in Table III-1, of those 12,162 total mines,
                11,231 mines were MNM mines and 931 mines were coal mines. MNM mines
                can be broadly divided into five commodity groups: metal, nonmetal,
                stone, crushed limestone, and sand and gravel. These broad categories
                encompass approximately 98 different commodities.\1\ Table III-1 shows
                that a majority of MNM mines produce sand and gravel, while the largest
                number of MNM miners work at metal mines (not
                [[Page 44860]]
                including MNM contract workers (i.e., independent contractors and
                employees of independent contractors who are engaged in mining
                operations)).
                ---------------------------------------------------------------------------
                 \1\ Commodities such as sand, gravel, silica, and/or stone for
                example are used in road building, concrete construction,
                manufacture of glass and ceramics, molds for metal castings in
                foundries, abrasive blasting operations, plastics, rubber, paint,
                soaps, scouring cleansers, filters, hydraulic fracturing, and
                various architectural applications. Some commodities naturally
                contain high levels of crystalline silica, such as high-quartz
                industrial and construction sands and granite dimension stone and
                gravel (both produced for the construction industry).
                [GRAPHIC] [TIFF OMITTED] TP13JY23.000
                 The 931 coal mines--underground and surface--produce bituminous,
                subbituminous, anthracite, and lignite coal. Coal mining activities
                generate mixed coal mine dust that contains respirable silicates such
                as kaolinite, oxides such as quartz, as well as other components (IARC,
                1997). These activities include the general mining activities
                previously mentioned (e.g., cutting, sanding, drilling, crushing, and
                hauling materials), as well as roof bolter operations, continuous
                mining machine operations, longwall mining, and other activities. Table
                III-1 shows that there are more surface coal mines than underground
                coal mines, but more miners are working in underground coal mines than
                surface coal mines (not including coal contract workers).
                IV. Existing Standards and Implementation
                 MSHA has maintained health standards to protect MNM and coal miners
                from excessive exposure to respirable crystalline silica for decades.
                MSHA's existing standards, established in the early 1970s, limit
                miners' exposures to respirable crystalline silica. These standards
                require mine operators to monitor occupational exposures to respirable
                crystalline silica and to use engineering controls as the primary means
                of suppressing, diluting, or diverting dust generated by mining
                activities. They also require mine operators to provide respiratory
                protection in limited situations and on a temporary basis. The existing
                standards for MNM and coal mines differ in some respects, including
                exposure limits and monitoring. This section describes MSHA's existing
                standards for respirable crystalline silica and presents respirable
                crystalline silica sampling data to show how MNM and coal mine
                operators have complied with them in recent years.
                A. Existing Standards--Metal and Nonmetal Mines
                 MSHA's existing standards for exposure to airborne contaminants,
                including respirable crystalline silica, in MNM mines are found in 30
                CFR part 56, subpart D (Air Quality and Physical Agents), and 30 CFR
                part 57, subpart D (Air Quality, Radiation, Physical Agents, and Diesel
                Particulate Matter). These standards include PELs for airborne
                contaminants (Sec. Sec. 56.5001 and 57.5001), exposure monitoring
                (Sec. Sec. 56.5002 and 57.5002), and control of exposure to airborne
                contaminants (Sec. Sec. 56.5005 and 57.5005).
                 Permissible Exposure Limits. The existing PELs for the three
                polymorphs of respirable crystalline silica are based on the
                TLVs[supreg] Threshold Limit Values for Chemical Substances in Workroom
                Air Adopted by the American Conference of Governmental Industrial
                Hygienists (ACGIH) for 1973, incorporated by reference in 30 CFR
                56.5001 and 57.5001 (ACGIH, 1974). The 1973 TLV[supreg] establishes
                limits for respirable dust containing 1 percent quartz or greater and
                is calculated in milligrams per cubic meter of air (mg/m\3\) for each
                respirable dust sample. The TLV[supreg] for quartz is calculated by
                dividing the percent of respirable quartz plus 2, into the number 10.
                The TLV[supreg] for cristobalite and the TLV[supreg] for tridymite,
                respectively, are calculated by multiplying the same mass formula by
                one-half using the percentages of either cristobalite or tridymite
                found in the sample. Thus, the resulting TLVs[supreg] for respirable
                dust containing 1 percent respirable crystalline silica or greater are
                designed to limit exposures to less than 0.1 mg/m\3\ or 100 [micro]g/
                m\3\ for quartz, to less than 0.05 mg/m\3\ or 50 [micro]g/m\3\ for
                cristobalite, and to less than 0.05 mg/m\3\ or 50 [micro]g/m\3\ for
                tridymite. Throughout the remainder of this preamble, the
                concentrations of respirable dust and respirable crystalline silica are
                expressed in [micro]g/m\3\.
                [[Page 44861]]
                 Exposure Monitoring. Under 30 CFR 56.5002 and 57.5002, MNM mine
                operators must conduct respirable dust ``surveys . . . as frequently as
                necessary to determine the adequacy of control measures.'' Mine
                operators can satisfy the survey requirement through various
                activities, such as respirable dust sampling and analysis, walk-through
                inspections, wipe sampling, examining dust control system and
                ventilation system maintenance, and reviewing information obtained from
                injury, illness, and accident reports.
                 MSHA encourages MNM mine operators to conduct sampling for airborne
                contaminants to ensure a healthy and safe work environment for miners
                because sampling provides more accurate information about miners'
                exposures to harmful airborne contaminants and the effectiveness of
                existing controls in reducing such exposures. When a mine operator's
                respirable dust survey indicates that miners have been overexposed to
                any airborne contaminant, including respirable crystalline silica, the
                operator is expected to adjust its control measures (e.g., exhaust
                ventilation) to reduce or eliminate the identified hazard. After doing
                so, the mine operator is expected to conduct additional surveys to
                determine whether these efforts were successful. Re-surveying should be
                done as frequently as necessary to ensure that the implemented control
                measures remain adequate. MSHA's determination of whether a mine
                operator has surveyed frequently enough is based on several factors,
                including whether sampling results comply with the permissible exposure
                limit, whether there have been changes in the mining operation or
                process, and whether controls such as local exhaust ventilation systems
                need routine or special maintenance.
                 Exposure Controls. MSHA's existing standards for controlling a
                miner's exposure to harmful airborne contaminants (Sec. Sec. 56.5005
                and 57.5005) require, if feasible, prevention of contamination, removal
                by exhaust ventilation, or dilution with uncontaminated air. The use of
                respiratory protective equipment is also allowed under specified
                circumstances such as when engineering controls are being developed or
                are not feasible. When respiratory protective equipment is used, the
                operator must have a respiratory protection program consistent with the
                requirements of American National Standards Practices for Respiratory
                Protection ANSI Z88.2-1969.
                 Consistent with widely accepted industrial hygiene principles and
                NIOSH's recommendations, MSHA requires the use of engineering controls,
                supplemented by administrative controls, in its enforcement for the
                control of occupational exposure to respirable crystalline silica and
                other airborne contaminants (NIOSH, 1974). Engineering controls
                designed to remove or reduce the hazard at the source are the most
                effective. Examples of engineering controls include the installation of
                proper ventilation systems, use of water sprays or wetting agents to
                suppress airborne contaminants, installation of machine-mounted dust
                collectors to capture respirable crystalline silica and other
                contaminants, and the installation of control booths or environmental
                cabs to enclose equipment operators.
                 Although considered a supplementary or secondary measure to
                engineering controls, mine operators may use administrative controls to
                further reduce miners' exposures to respirable crystalline silica and
                other airborne contaminants. In applying administrative controls, mine
                operators can direct miners to perform certain activities in specific
                manners. For instance, as an administrative control, operators can
                specify adequate housekeeping procedures for miners to clean spills or
                handle contaminated clothing which could reduce occupational exposure
                to airborne contaminants, including respirable crystalline silica.
                 In addition, respiratory protective equipment can be used in
                controlling miners' exposures to airborne contaminants, including
                respirable crystalline silica, on a temporary basis or under non-
                routine, limited conditions. The use of respiratory protection is,
                however, considered to be a supplement, not an alternative to any
                engineering or administrative control, in reducing or eliminating a
                miner's exposure to airborne contaminants including respirable
                crystalline silica.
                 Under the existing standards in Sec. Sec. 56.5005 and 57.5005, in
                circumstances where engineering controls are not yet developed or where
                it is necessary for miners to enter hazardous atmospheres to establish
                controls or to perform non-routine maintenance or investigation, a
                miner using appropriate respiratory protection ``may work for
                reasonable periods of time'' in concentrations of airborne contaminants
                which exceed exposure limits. Respirators approved by NIOSH and
                suitable for their intended purpose must be provided by mine operators
                at no cost to the miner and must be used by miners to protect
                themselves against the health and safety hazards of airborne
                contaminants. Whenever respiratory protection is used, MNM mine
                operators are required to have a respirator program consistent with the
                requirements specified in ANSI Z88.2-1969.
                B. Existing Standards--Coal Mines
                 Under existing standards, there is no separate standard for
                respirable crystalline silica for coal mines. MSHA's existing standards
                for exposure to respirable quartz in coal mines, found in 30 CFR 70.101
                and 71.101, establish a respirable dust standard when quartz is present
                for underground and surface coal mines, respectively. Under 30 CFR part
                90 (Mandatory Health Standards--Coal Miners Who Have Evidence of the
                Development of Pneumoconiosis), Sec. 90.101 also sets the respirable
                dust standard when quartz is present for coal miners. Under these
                respirable dust standards, coal miners' exposures to respirable quartz
                are indirectly regulated through reductions in the overall respirable
                dust standard.
                 Under its existing respirable coal mine dust standards, MSHA
                defines quartz as crystalline silicon dioxide (SiO2), which
                includes not only quartz but also two other polymorphs, cristobalite
                and tridymite.\2\ Therefore, quartz and respirable crystalline silica
                are used interchangeably in the discussions of MSHA's existing
                standards for controlling exposures to respirable crystalline silica in
                coal mines.
                ---------------------------------------------------------------------------
                 \2\ Quartz is defined in 30 CFR 70.2, 71.2, and 90.2 as
                crystalline silicon dioxide (SiO2) not chemically
                combined with other substances and having a distinctive physical
                structure. Crystalline silicon dioxide is most commonly found in
                nature as quartz but sometimes occurs as cristobalite or, rarely, as
                tridymite. Quartz accounts for the overwhelming majority of
                naturally occurring crystalline silica and is present in varying
                amounts in almost every type of mineral.
                ---------------------------------------------------------------------------
                 Exposure Limits. The exposure limit for respirable crystalline
                silica during a coal miner's shift is 100 [micro]g/m\3\, reported as an
                equivalent concentration as measured by the Mining Research
                Establishment (MRE) instrument. This equivalent concentration of
                respirable crystalline silica must not be exceeded during the miner's
                entire shift, regardless of duration. When the equivalent concentration
                of respirable quartz exceeds 100 [micro]g/m\3\, under Sec. Sec.
                70.101, 71.101, and 90.101, MSHA imposes a reduced respirable dust
                standard designed to ensure that respirable quartz will not exceed 100
                [micro]g/m\3\. The applicable dust standard, when the equivalent
                concentration of respirable crystalline silica exceeds 100 [micro]g/
                m\3\, is computed by dividing the percent of quartz into the number 10.
                [[Page 44862]]
                The result of this calculation becomes the exposure limit for
                respirable coal mine dust (RCMD), for the sections of the mine
                represented by the sample. Various sections within a mine may have
                different reduced RCMD exposure limits. Therefore, when a respirable
                dust sample collected by MSHA indicates that the average concentration
                of respirable quartz dust exceeds the exposure limit, the mine operator
                is required to comply with the applicable dust standard. By reducing
                the amount of respirable dust to which miners are exposed during their
                shifts, the miners' exposures to respirable crystalline silica are
                reduced to a level at or below the exposure limit of 100 [micro]g/m\3\.
                 Exposure Monitoring. Under Sec. Sec. 70.208, 70.209, 71.206, and
                90.207, coal mine operators are required to sample for respirable dust
                on a quarterly basis for specified occupations and work areas. The
                occupations and work areas specified in the existing coal standards are
                the occupations and work areas at a coal mine that are expected to have
                the highest concentrations of respirable dust--typically in locations
                where respirable dust is generated. In addition, respirable dust
                sampling must be representative of respirable dust exposures during a
                normal production shift. Also, sampling must occur while miners are
                performing routine, day-to-day activities. Part 90 miners must be
                sampled for the air they breathe while performing their normal work
                duties, from the start of their work day to the end of their work day,
                in their normal work locations.\3\
                ---------------------------------------------------------------------------
                 \3\ A ``Part 90 miner'' is defined in 30 CFR 90.3 as a miner
                employed at a coal mine who shows evidence of having contracted
                pneumoconiosis based on a chest X-ray or based on other medical
                examinations, and who is afforded the option to work in an area of a
                mine where the average concentration of respirable dust in the mine
                atmosphere during each shift to which that miner is exposed is
                continuously maintained at or below the applicable standard.
                ---------------------------------------------------------------------------
                 Exposure Controls. Under Sec. Sec. 70.208, 70.209, 71.206, and
                90.207, coal mine operators are required to use engineering or
                environmental controls as the primary means of complying with the
                respirable dust standards. Similar to the MNM standards, engineering
                and environmental controls include the use of dust collectors, water
                sprays, and ventilation controls. For many underground coal mines,
                providing adequate ventilation is the primary engineering control for
                respirable dust, ensuring that dust concentrations are continuously
                diluted with fresh air and exhausted away from miners.
                 When a respirable dust sample exceeds the exposure limit of 100
                [micro]g/m\3\ for respirable quartz, the operator must reduce the
                average concentration of RCMD to a level designed to maintain the
                quartz level at or below 100 [micro]g/m\3\. If operators exceed the
                reduced RCMD standard, they are required to take corrective action to
                reduce exposure and comply with the reduced standard. Corrective
                actions that lower respirable coal mine dust, thus lowering respirable
                quartz exposures, are selected after evaluating the cause or causes of
                the overexposure. Corrective actions can include increasing air flow,
                improving ventilation controls, repairing and maintaining existing dust
                suppression controls, adding water sprays or other controls, cleaning
                dust filters or collectors more frequently, or repositioning the miner
                away from the dust source.
                 When taking corrective actions to reduce the exposure to respirable
                dust, coal mine operators must make approved respiratory equipment
                available to miners under Sec. Sec. 70.208 and 71.206. Whenever
                respiratory protection is used, Sec. 72.700 requires coal mine
                operators to comply with requirements specified in ANSI Z88.2-1969.
                C. MSHA Inspection and Respirable Dust Sampling
                 MSHA collects respirable dust samples at mines and analyzes them
                for respirable crystalline silica to determine whether the respirable
                crystalline silica exposure limits are met and whether exposure
                controls are adequate. This section describes the respirable dust
                samples collected at MNM and coal mines in recent years and presents
                the results of the sample data analyses.
                1. Respirable Dust Sample Collection
                 This subsection offers a brief description of how MSHA samples for
                respirable crystalline silica under the existing standards. Upon their
                arrival at mines, MSHA inspectors determine which areas of the mine and
                which miners to select for respirable dust sampling. At MNM mines, the
                MSHA inspector often determines sampling locations based on sample
                results from previous inspections and on the inspector's onsite
                observations of work practices and work areas. At coal mines, the MSHA
                inspector conducts sampling among the occupations or from the work
                areas that are specified for operator sampling under 30 CFR parts 70,
                71, and 90. Generally speaking, MSHA inspectors collect respirable dust
                samples from the common occupations during typical and normal
                activities at the mine and from the positions that are commonly known
                to have the highest concentration of respirable dust.
                 After identifying which miners and which areas at the mine will be
                sampled for respirable dust, MSHA inspectors place gravimetric samplers
                on the selected miners or at the selected locations. Gravimetric
                samplers consist of a portable air-sampling pump connected to a
                particle-size separator (i.e., cyclone) and collection medium (i.e.,
                filter). MSHA inspectors use Dorr-Oliver 10-mm nylon cyclones operated
                at a 1.7 liters per minute (L/min) flow rate for MNM mine sampling and
                at a 2.0 L/min flow rate (reported as MRE-equivalent concentrations)
                for coal mine sampling.\4\ For the entire duration of the work shift,
                the gravimetric sampler captures air from the breathing zone of each
                selected miner or occupation and from each selected work area.
                ---------------------------------------------------------------------------
                 \4\ This type of sampling equipment was developed to separate
                the airborne particles by size in a manner similar to the size-
                selective deposition and retention characteristics of the human
                respiratory system. It is important to note that size-selective
                sampling does not measure the deposition of respirable particles in
                the lung. Rather, it provides a measure of the particulate mass
                available for deposition to the deep lung during breathing (Raabe
                and Stuart, 1999).
                ---------------------------------------------------------------------------
                 MSHA inspectors use the full-shift sampling approach. When miners
                work longer than an 8-hour shift, which is common, those miners are
                sampled continuously throughout the extended work shifts. Full-shift
                sampling is used to minimize errors associated with fluctuations in
                airborne contaminant concentrations during the miners' work shifts and
                to avoid any speculation about the miners' exposures during unsampled
                periods of the work shift. Once sampling is completed, the inspectors
                send the cassettes containing the full-shift respirable dust samples to
                the MSHA Laboratory for analysis.
                [[Page 44863]]
                2. Respirable Dust Sample Analysis
                 The MSHA Laboratory analyzes inspectors' respirable dust samples,
                following its standard operating procedures (SOPs) summarized below.\5\
                Any samples that are broken, torn, or visibly wet are voided and
                removed before analysis. Once weighing of the samples is completed,
                samples are again screened based on mass gain and examined for
                validity. All valid samples that meet the minimum mass gain criteria
                per the associated MSHA analytical method are then analyzed for
                respirable crystalline silica and for the compliance determination.\6\
                ---------------------------------------------------------------------------
                 \5\ The MSHA Laboratory has fulfilled the requirements of the
                AIHA Laboratory Accreditation Programs (AIHA-LAP), LLC accreditation
                to the ISO/IEC 17025:2017 international standard for industrial
                hygiene.
                 \6\ The minimum mass gain criteria used by the MSHA Laboratory
                for the different samples are:
                 MNM mine respirable dust samples: greater than or equal
                to 0.100 mg;
                 Underground coal mine respirable dust samples: greater
                than or equal to 0.100 mg; and
                 Surface coal mine respirable dust samples: greater than
                or equal to 0.200 mg.
                 Exception: For six surface occupations that have been deemed
                ``high risk,'' the laboratory uses a minimum mass gain criterion of
                greater than or equal to 0.100 mg.
                 If cristobalite analysis is requested for MNM mine respirable
                dust samples, filters having a mass gain of 0.05 mg or more are
                analyzed. In the rare instance when tridymite analysis is requested,
                a qualitative analysis for the presence of the polymorph is
                conducted concurrently with the cristobalite analysis.
                ---------------------------------------------------------------------------
                 The MSHA Laboratory uses two analytical methods to determine the
                concentration of quartz (and cristobalite and tridymite, if requested):
                X-ray diffraction (XRD) for respirable dust samples from MNM mines, and
                Fourier transform infrared spectroscopy (FTIR) for respirable coal mine
                dust samples.\7\ The XRD method uses X-rays to distinguish and measure
                the structure, composition, and physical properties of a sample. The
                FTIR method relies on the absorption of infrared light to determine the
                composition of a sample. The percentage of silica in the MNM mine dust
                sample is calculated using the mass of quartz or cristobalite
                determined from the XRD analysis and the measured mass of respirable
                dust. The percentage of silica is used to calculate MSHA's PELs for
                quartz and cristobalite, in accordance with Sec. Sec. 56.5001 and
                57.5001. Similarly, in the respirable coal mine dust sample, the
                percentage of quartz is calculated using the quartz mass determined
                from the FTIR analysis and the sample's mass of dust. Current FTIR
                methods, however, cannot quantify quartz and cristobalite, and/or
                tridymite, in the same sample. For coal mines, the percentage of quartz
                is used to calculate the reduced dust standard when the quartz
                concentration exceeds 100 [micro]g/m\3\ (MRE).
                ---------------------------------------------------------------------------
                 \7\ Details on MSHA's analytical procedures for respirable
                crystalline silica analysis can be found in ``MSHA P-2: X-Ray
                Diffraction Determination of Quartz and Cristobalite in Respirable
                Metal/Nonmetal Mine Dust'' and ``MSHA P-7: Determination of Quartz
                in Respirable Coal Mine Dust by Fourier Transform Infrared
                Spectroscopy.''
                 Department of Labor, Mine Safety and Health Administration,
                Pittsburgh Safety and Health Technology Center, X-Ray Diffraction
                Determination of Quartz and Cristobalite in Respirable Metal/
                Nonmetal Mine Dust. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P2.pdf. Department of Labor, Mine Safety and Health
                Administration, Pittsburgh Safety and Health Technology Center, MSHA
                P-7: Determination of Quartz in Respirable Coal Mine Dust By Fourier
                Transform Infrared Spectroscopy. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P7.pdf.
                ---------------------------------------------------------------------------
                 It is worth noting how MSHA calculates full-shift exposure to
                respirable crystalline silica (and other airborne contaminants). When a
                miner who works an 8-hour shift is sampled, the miner's 8-hour TWA
                exposure is calculated as follows:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.001
                 However, for work shifts that last longer than 8 hours, a coal
                miner's full-shift exposure is calculated differently than an MNM
                miner's full-shift exposure. In accordance with Sec. 70.2, the coal
                miner's extended full-shift exposure has, since 2014, been calculated
                in the following way:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.002
                 For the MNM miner, MSHA calculates extended full-shift exposure
                according to the following formula:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.003
                 For respirable dust samples from MNM mines, 480 minutes is used in
                the denominator regardless of the actual sampling time. Contaminants
                collected over extended shifts (e.g., 600-720 minutes) are calculated
                as if they had been collected over 480 minutes. MSHA has used this
                calculation approach (also known as ``shift-weighted average'') since
                the 1970s.
                 Under the shift-weighted average approach, exposures for work
                schedules greater than 8 hours are proportionately adjusted to allow
                direct comparison with the 8-hour PEL. The ACGIH TLVs[supreg] adopted
                by MSHA are based on exposure periods of no more than 8 hours per day
                and 40 hours per week, with 16 hours of recovery time between shifts.
                D. Respirable Crystalline Silica Sampling Results--Metal and Nonmetal
                Mines
                 This section presents the results of respirable dust samples that
                were collected by MSHA inspectors at MNM mines from 2005 to 2019. From
                January 1, 2005, to December 31, 2019, a total of 104,354 valid samples
                were collected. Of this total, 57,769 samples that met the minimum mass
                gain criteria were analyzed for respirable crystalline silica.
                [[Page 44864]]
                The vast majority of the 46,585 valid samples that were excluded from
                the analysis in this rulemaking did not meet the mass gain criteria
                described earlier and therefore the lab did not determine their silica
                concentration. Further information on the valid respirable dust samples
                that are excluded from the analysis in this rulemaking can be found in
                Appendix A of the preamble.
                 The respirable crystalline silica concentration is calculated using
                the measured mass of each of the polymorphs and the air sampling
                volume. As discussed above, the existing PEL for quartz in MNM mines is
                approximately equivalent to 100 [micro]g/m\3\ for a full-shift
                exposure, calculated as an 8-hour TWA, while the existing PELs for
                cristobalite and tridymite, respectively, are approximately equivalent
                to 50 [micro]g/m\3\ for a full-shift exposure, calculated as an 8-hour
                TWA.\8\
                ---------------------------------------------------------------------------
                 \8\ If more than one polymorph is present the equation used to
                calculate the TLV[supreg] for respirable dust containing quartz is
                modified per Appendix C of the 1973 ACGIH TLV[supreg] Handbook, and
                the equation is modified as follows: 10/[(% quartz + 2) + 2 (%
                cristobalite + 2)].
                ---------------------------------------------------------------------------
                1. Annual Results of MNM Respirable Crystalline Silica Samples
                 Table IV-1 below shows the variation between 2005 and 2019 in: (1)
                the numbers of MNM respirable dust samples analyzed for respirable
                crystalline silica; and (2) the number and percentage of samples that
                had concentrations of respirable crystalline silica greater than 100
                [micro]g/m\3\. Of the 57,769 MNM respirable dust samples analyzed for
                respirable crystalline silica over the 15-year period, about 6 percent
                (3,539 samples) had respirable crystalline silica concentrations
                exceeding the existing PEL of 100 [micro]g/m\3\. The average annual
                rates of overexposure ranged from a maximum of approximately 10 percent
                in 2006 (the second year) to a minimum of approximately 4 percent in
                2019 (the last year of the time series). Compared with the rates in
                2005-2008, overexposure rates were substantially lower in 2009-2017,
                with a further drop in 2018-19.
                BILLING CODE 4520-43-P
                [GRAPHIC] [TIFF OMITTED] TP13JY23.004
                [[Page 44865]]
                2. Analysis of MNM Respirable Crystalline Silica Samples by Commodity
                 Because the MNM mining industry produces commodities that contain
                varying degrees of respirable crystalline silica, it is important to
                examine each commodity separately. MNM mines can be grouped by five
                commodities: metal, sand and gravel, stone, crushed limestone, and
                nonmetal (where nonmetal includes all other materials that are not
                metals, besides sand, gravel, stone, and limestone). This grouping is
                based on the mine operator-reported mining products and the North
                American Industry Classification System (NAICS) codes. (Appendix B of
                the preamble provides a list of the NAICS codes relevant for MNM mining
                and how each code is assigned to one of the five commodities.)
                 Table IV-2 shows the distribution of the respirable dust samples
                analyzed for respirable crystalline silica by mine commodity. The
                percentage of samples with respirable crystalline silica concentrations
                greater than the existing exposure limit of 100 [micro]g/m\3\ varies
                across the different commodities. It is highest for the metal, sand and
                gravel, and stone commodities (at approximately 11, 7, and 7 percent,
                respectively), and lowest for the nonmetal and crushed limestone
                commodities (at approximately 4 and 3 percent, respectively).
                [GRAPHIC] [TIFF OMITTED] TP13JY23.005
                3. Analysis of MNM Respirable Crystalline Silica Samples by Occupation
                 To examine how miners who perform different tasks differ in
                occupational exposure to respirable crystalline silica, MSHA grouped
                MNM mining jobs into 11 occupational categories. These categories
                include jobs that are similar in terms of tasks performed, equipment
                used, and engineering or administrative controls used to control
                miners' exposure. For example, backhoe operators, bulldozer operators,
                and tractor operators were grouped into ``operators of large powered
                haulage equipment,'' whereas belt crew, belt cleaners, and belt
                vulcanizers were grouped into ``conveyer operators.'' The 121 MNM job
                codes used by MSHA inspectors were grouped into the following
                occupational categories: \9\
                ---------------------------------------------------------------------------
                 \9\ For a full crosswalk of job codes included in each of these
                11 Occupational Categories, please see Appendix C of the preamble.
                Also, note that the order of the presentation of the 11 Occupational
                Categories here follows the general sequence of mining activities:
                first development and production, then ore/mineral processing, then
                loading, hauling, and dumping, and finally all others.
                ---------------------------------------------------------------------------
                 (1) Drillers (e.g., Diamond Drill Operator, Wagon Drill Operator,
                and Drill Helper),
                 (2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting
                Machine Operator, and Cutting Machine Helper),
                 (3) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill Operator,
                Leaching Operator, and Pelletizer Operator),
                 (4) Crushing Equipment and Plant Operators (e.g., Crusher Operator/
                Worker, Scalper Screen Operator, and Dry Screen Plant Operator),
                 (5) Packaging Equipment Operators (e.g., Bagging Operator and
                Packaging Operations Worker),
                 (6) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt
                Vulcanizer),
                 (7) Truck Loading Station Tenders (e.g., Dump Operator and Truck
                Loader),
                 (8) Operators of Large Powered Haulage Equipment (e.g., Tractor
                Operators, Bulldozer Operator, and Backhoe Operators),
                 (9) Operators of Small Powered Haulage Equipment (e.g., Bobcat
                Operator, Scoop-Tram Operator, and Forklift Operator),
                 (10) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and
                Supervisors), and
                 (11) Miners in Other Occupations (e.g., Welder, Dragline Operator,
                Ventilation Crew and Dredge/Barge Operator).
                 Table IV-3 shows sample numbers and overexposure rates by MNM
                occupation. Operators of large powered haulage equipment accounted for
                the largest number of samples analyzed for silica (17,016 samples),
                whereas conveyor operators accounted for the fewest (215 samples).
                Table IV-3 also shows the number and percentage of the samples
                exceeding the existing respirable crystalline silica PEL of 100
                [micro]g/m\3\. In every occupational category, some MNM miners were
                exposed to respirable crystalline silica levels above the existing PEL.
                In 9 out of the 11 occupational categories, the percentage of samples
                exceeding the existing PEL is less than 10 percent, although two have
                [[Page 44866]]
                higher rates, ranging up to more than 19 percent (in the case of stone
                cutting operators).
                [GRAPHIC] [TIFF OMITTED] TP13JY23.006
                4. Conclusion
                 This analysis of MSHA inspector sampling data shows that MNM
                operators have generally met the existing standard. Of the 57,769
                respirable dust samples from MNM mines, approximately 6 percent
                exceeded the existing respirable crystalline silica PEL of 100
                [micro]g/m\3\, although there are several outliers with much higher
                overexposures. For 9 of the 11 occupational categories, less than 10
                percent of the respirable dust samples had concentrations over the
                existing PEL of 100 [micro]g/m\3\ for respirable crystalline silica. In
                addition, about 80 percent of samples taken from stone cutting
                operators did not exceed the existing PEL, which historically has had
                high exposures to respirable dust and respirable crystalline silica;
                \10\ nevertheless, this occupation continues to experience the highest
                overexposures relative to other MNM occupations. For the categories of
                drillers, miners in other occupations, and operators of large powered
                haulage equipment, approximately 5 percent or less of the respirable
                dust samples showed concentrations over the existing exposure limit.
                ---------------------------------------------------------------------------
                 \10\ Analysis of MSHA respirable dust samples from 2005 to 2010
                showed that stone and rock saw operators had approximately 20
                percent of the sampled exposures exceeding the PEL. Watts et al.
                (2012).
                ---------------------------------------------------------------------------
                 MSHA believes that improved technology, engineering controls, and
                better training contributed to the reductions in exposures for miners
                who work in occupations exposed to the highest levels of respirable
                crystalline silica. In summary, the analysis of MSHA inspector sampling
                data indicates that the controls that MNM mine operators are using,
                together with MSHA's enforcement, have generally been effective in
                keeping miners' exposure at or below the existing limit of 100
                [micro]g/m\3\.
                E. Respirable Crystalline Silica Sampling Results--Coal Mines
                 To examine coal mine operators' compliance with existing respirable
                crystalline silica standards, MSHA analyzed RCMD samples collected by
                MSHA inspectors from 2016 to 2021. (The data analyses for this
                rulemaking do not include any respirable dust samples collected by coal
                mine operators.) The analysis below is based on the samples collected
                by inspectors starting on August 1, 2016, when Phase III of MSHA's 2014
                Lowering Miners' Exposure to Respirable Coal Mine Dust, Including
                Continuous Personal Dust Monitors (Coal Dust Rule) (79 FR 24813, May 1,
                2014) went into effect. At that time, the exposure limits for RCMD
                [[Page 44867]]
                were lowered from 2.0 mg/m\3\ to 1.5 mg/m\3\ (MRE equivalent) at
                underground and surface coal mines, and from 1.0 mg/m\3\ to 0.5 mg/m\3\
                (MRE equivalent) for intake air at underground coal mines and for Part
                90 miners. From August 1, 2016, to July 31, 2021, MSHA inspectors
                collected a total of 113,607 valid RCMD samples. Of these valid
                samples, only those collected from the breathing zones of miners were
                used in the analysis for this rulemaking; no environmental dust samples
                were included.\11\ Of those samples, 63,127 samples that met the
                minimum mass gain criteria and had no other disqualifying issues were
                analyzed for respirable quartz and quartz concentrations were
                determined. The majority of the non-environmental valid samples
                excluded from this rulemaking analysis were excluded due to
                insufficient mass. Further information on the valid respirable dust
                samples that are not included in the rulemaking analysis can be found
                in Appendix A of the preamble.
                ---------------------------------------------------------------------------
                 \11\ Environmental samples were not included in the analysis to
                be consistent with the proposed sampling requirements to determine
                individual miner exposure.
                ---------------------------------------------------------------------------
                 Of the 63,127 valid samples analyzed for respirable crystalline
                silica and used for this analysis, about 1 percent (777 samples) were
                over the existing quartz exposure limit of 100 [micro]g/m\3\ (MRE
                equivalent) for a full shift, calculated as a TWA.\12\ Overexposure
                rates (the percent of samples above the exposure limit, on average
                across all coal mining occupations) decreased by nearly a quarter
                between the first half and the second half of the 2016-2021 period. As
                in MNM mines, different miner occupations had different overexposure
                rates. Using broader groupings, surface mines experienced higher rates
                of overexposure than underground mines (2.4 percent versus 1.0 percent,
                respectively).
                ---------------------------------------------------------------------------
                 \12\ The conversion between ISO values and MRE values uses the
                NIOSH conversion factor of 0.857. In the 1995b Criteria Document,
                NIOSH presented an empirically derived conversion factor of 0.857
                for comparing current (MRE) and recommended (ISO) respirable dust
                sampling criteria using the 10 mm Dorr-Oliver nylon cyclone operated
                at 2.0 and 1.7 L/min, respectively (i.e., 1.5 mg/m\3\ BMRC-MRE =
                1.29 mg/m\3\ ISO).
                ---------------------------------------------------------------------------
                1. Annual Results of Coal Respirable Crystalline Silica Samples
                 In examining trends from one year to the next, the discussion below
                focuses on the samples collected in the 6 calendar years from 2016 to
                2021. The number of samples per year was stable from 2017 to 2019
                before decreasing in 2020.\13\ The overexposure rate decreased across
                the entire 2016 to 2021 period, from 1.41 percent in 2016 to 0.95
                percent in 2021. As shown in Table IV-4, a review of the 6 calendar
                years reveals that the overexposure rate decreased by nearly a quarter
                from 2016-2018 (1.38 percent) to 2019-2021 (1.07 percent).
                ---------------------------------------------------------------------------
                 \13\ The coal samples for 2016 begin in August of that year and
                the coal samples for 2021 end in July of that year.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.007
                2. Analysis of Coal Respirable Crystalline Silica Samples by Location
                 Coal mining activities differ depending on the characteristics and
                locations of coal seams. When coal seams are several hundred feet below
                the surface, miners tunnel into the earth and use underground mining
                equipment to extract coal, whereas miners at surface coal mines remove
                topsoil and layers of rock to expose coal seams. Due to these
                differences, it is important to examine the respirable crystalline
                silica data by location to determine how underground and surface coal
                miners differ in occupational exposure to respirable crystalline
                silica.
                 Table IV-5, which presents the overexposure rate by type of mine
                where respirable coal mine dust samples were collected, shows that
                samples from surface coal mines reflected higher rates of overexposure
                than samples from underground mines.
                [[Page 44868]]
                Out of the 53,095 respirable coal mine dust samples from underground
                mines, 1 percent (537 samples) were over the existing exposure limit.
                By contrast, there were 10,032 samples from surface coal mines, and
                approximately 2.4 percent (240 samples) of those samples were over the
                existing exposure limit.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.008
                3. Analysis of Coal Respirable Crystalline Silica Samples by Occupation
                 To assess the exposure to respirable crystalline silica of miners
                in different occupations, MSHA has consolidated the 220 job codes for
                coal mines into 9 occupational categories (using a similar process to
                the one it used for the MNM mines, but with different job codes and
                categories). For the coal mine occupational categories,\14\ a
                distinction is made between occupations based on whether the job tasks
                are being performed at the surface of a mine or underground. For
                example, bulldozer operators are assigned to the operators of large
                powered haulage equipment grouping and then sorted into separate
                occupational categories based on whether they are working at the
                surface of a mine or underground.
                ---------------------------------------------------------------------------
                 \14\ For a full crosswalk of which job codes were included in
                each of these nine Occupational Categories, please see Appendix C of
                the preamble.
                ---------------------------------------------------------------------------
                 Of the nine occupational categories used for coal miners, the five
                underground categories are:
                 (1) Continuous Mining Machine Operators (e.g., Coal Drill Helper
                and Coal Drill Operator),
                 (2) Longwall Workers (e.g., Headgate Operator and Jack Setter
                (Longwall)),
                 (3) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper),
                 (4) Operators of Large Powered Haulage Equipment (e.g., Shuttle Car
                Operator, Tractor Operator/Motorman, Scoop Car Operator), and
                 (5) All Other Underground Miners (e.g., Electrician, Mechanic, Belt
                Cleaner and Laborer, etc.).
                 The four surface occupational categories are:
                 (1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and
                Auger Operator),
                 (2) Crusher Operators (e.g., Crusher Attendant, Washer Operator,
                and Scalper-Screen Operator),
                 (3) Operators of Large Powered Haulage Equipment (e.g., Backhoe
                Operator, Forklift Operator, and Bulldozer Operator), and
                 (4) Mobile Workers (e.g., Electrician, Mechanic, Blaster, Laborer,
                etc.).
                 The most sampled occupational category was operators of large
                powered haulage equipment (underground), representing approximately 34
                percent of the samples taken. The least sampled occupational category
                was crusher operators (surface), consisting of 1 percent of the samples
                taken. Table IV-6 displays the number and percent of respirable coal
                mine dust samples with quartz greater than the existing exposure limit
                for each occupational category.
                [[Page 44869]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.009
                 Looking at trends, every occupational category shows a decrease in
                overexposure rates over time. See Figure IV-1. Most of the nine
                categories had lower rates of overexposure in the 2019-2021 period than
                in the 2016-2018 period.
                [[Page 44870]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.010
                BILLING CODE 4520-43-C
                 In all occupational categories, coal miners were sometimes exposed
                to respirable crystalline silica levels above the existing exposure
                limit. But the sampling data showed that coal mine operators can
                generally comply with the existing exposure limit. For example,
                although mining tasks performed by the occupational category of roof
                bolters (underground) historically resulted in high levels of
                overexposure to quartz, the low levels of overexposure for that
                occupation in 2016-2021 (i.e., 1 percent) suggest that roof bolters now
                benefit from the improved respirable dust standard, improved
                technology, and better training.\15\ Over the 2016-2021 period, coal
                miners in the occupational category drillers (surface) were the most
                frequently overexposed, with approximately 6 percent of samples over
                the existing quartz limit; they were followed by longwall workers
                (underground) (about 4 percent), operators of large powered haulage
                equipment (surface) (about 3 percent), and continuous mining machine
                operators (underground) (about 2 percent). For all other occupational
                categories, the overexposure rate was less than 1 percent.
                ---------------------------------------------------------------------------
                 \15\ The drilling operation in the roof bolting process,
                especially in hard rock, generates excessive respirable coal and
                quartz dusts, which could expose the roof bolting operator to
                continued health risks (Jiang and Luo, 2021).
                ---------------------------------------------------------------------------
                4. Conclusion
                 This analysis of MSHA inspector sampling data shows that coal mine
                operators can generally comply with the existing standards related to
                quartz. Of the 63,127 valid respirable dust samples from coal mines
                over the most recent 5-year period, 1.2 percent had respirable quartz
                over the existing exposure limit of 100 [micro]g/m\3\ (MRE equivalent)
                for a full-shift exposure, calculated as a TWA. Seven of the nine
                occupational categories had overexposure rates of 2.5 percent or less.
                Roof bolters (underground), which historically have had high exposures
                to respirable dust and respirable crystalline silica, had overexposure
                rates of 1 percent over this recent period. The data demonstrates that
                the controls that coal mine operators are using, together with MSHA's
                enforcement, have generally been effective in keeping miners' exposure
                to respirable crystalline silica at or below the existing exposure
                limit.
                V. Health Effects Summary
                 This section summarizes the health effects from occupational
                exposure to respirable crystalline silica. MSHA's full analysis is
                contained in the standalone document, entitled Effects of Occupational
                Exposure to Respirable Crystalline Silica on the Health of Miners
                (Health Effects document), which has been placed in the rulemaking
                docket for the MSHA silica rulemaking (RIN 1219-AB36, Docket ID no.
                MSHA-2023-0001) and is available on MSHA's website.
                 The purpose of the Agency's scientific review is to present MSHA's
                preliminary findings on the nature of the hazards presented by exposure
                to respirable crystalline silica and to present the basis for the
                Preliminary
                [[Page 44871]]
                Risk Analysis (PRA) to follow. (A PRA summary is presented in Section
                VI of this preamble and a standalone document entitled Preliminary Risk
                Analysis has been placed in the rulemaking docket for the MSHA silica
                rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is
                available on MSHA's website.) MSHA reviewed a wide range of health
                research literature that included more than 600 studies exploring the
                relationship between respirable crystalline silica exposure and
                resultant health effects in miners and other workers across various
                industries. After discussing the toxicity of respirable crystalline
                silica, MSHA's review of the literature covers the following topics:
                 (1) Silicosis;
                 (2) NMRD, excluding silicosis;
                 (3) Lung cancer and cancer at other sites;
                 (4) Renal disease; and
                 (5) Autoimmune diseases.
                 To develop this literature review, MSHA expanded upon OSHA's
                (2013b) review of the health effects literature to support its final
                respirable crystalline silica rule (81 FR 16286, March 25, 2016). MSHA
                also drew upon numerous studies conducted by NIOSH, the International
                Agency for Research on Cancer (IARC), the National Toxicology Program
                (NTP), and other researchers. These studies provided epidemiological
                data, morbidity (having a disease or a symptom of disease) and
                mortality (disease resulting in death) analyses, progression and
                pathology evaluations, death certificate and autopsy reviews, medical
                surveillance data, health hazard assessments, in vivo (animal) and in
                vitro toxicity data, and other toxicological reviews. These sources are
                cited throughout this summary and are listed in the References section
                of the Health Effects document. Additionally, these sources appear in
                the rulemaking docket.
                 MSHA's literature review is based on a weight-of-evidence approach,
                in which studies are evaluated for their overall quality. Causal
                inferences are drawn based on a determination of whether there is
                substantial evidence that exposure increases the risk of a particular
                adverse health effect. Factors MSHA considered in this weight-of-
                evidence analysis include: size of the cohort studied and power of the
                study to detect a sufficiently low level of disease risk, duration of
                follow-up of the study population, potential for study bias (such as
                selection bias or healthy worker effects), and adequacy of underlying
                exposure information for examining exposure-response relationships. Of
                the studies examined in the Health Effects document, studies were
                deemed suitable for inclusion in the PRA if there was adequate
                quantitative information on exposure and disease risks and the study
                was judged to be of sufficiently high quality according to the above
                criteria.
                 The understanding of how respirable crystalline silica causes
                adverse health effects has evolved greatly in the more than 45 years
                since the Mine Act was passed in 1977. Based on its extensive review of
                health research literature, MSHA has preliminarily determined that
                occupational exposure to respirable crystalline silica causes silicosis
                (acute silicosis, accelerated silicosis, simple chronic silicosis, and
                PMF), NMRD (including COPD), and lung cancer, and it also causes end-
                stage renal disease (ESRD). In addition, MSHA believes that respirable
                crystalline silica exposure is causally related to the development of
                some autoimmune disorders through inflammation pathways. Each of these
                effects is exposure-dependent, chronic, irreversible, and potentially
                disabling or fatal. MSHA's review of the literature indicates that
                under the existing standards found in 30 CFR parts 56, 57, 70, 71, and
                90, miners are still developing preventable diseases that are material
                impairments of health and functional capacity. Based on the assessment
                of health effects of respirable crystalline silica, MSHA preliminarily
                concludes that the proposed rule, which would lower the exposure limits
                in MNM and coal mining to 50 [micro]g/m\3\ and establish an action
                level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as an
                8-hour TWA, would reduce the risk of miners developing silicosis, NMRD,
                lung cancer, and renal disease.
                A. Toxicity of Respirable Crystalline Silica
                 Respirable crystalline silica is released into the environment
                during mining or milling processes, thus creating an airborne hazard.
                The particles may be freshly generated or re-suspended from surfaces on
                which it is deposited in mines or mills. Respirable crystalline silica
                particles may be irregularly shaped and variable in size. Inhaled
                respirable crystalline silica can be deposited throughout the lungs.
                Some pulmonary clearance of particles deposited in the deep lung (i.e.,
                alveolar region) may occur, but a large number of particles can be
                retained and initiate or advance the disease process. The toxicity of
                these retained particles is amplified because the particles are not
                water-soluble and do not undergo metabolism into less toxic compounds.
                This is important biologically and physiologically, as insoluble dusts
                may remain in the lungs for prolonged periods, resulting in a variety
                of cellular responses that can lead to pulmonary disease (ATSDR, 2019).
                Respirable crystalline silica particles that are cleared from the lungs
                by the lymphatic system are distributed to the lymph nodes, blood,
                liver, spleen, and kidneys, potentially accumulating in these other
                organ systems and causing renal disease and other adverse health
                effects (ATSDR, 2019).
                 Physical characteristics relevant to the toxicity of respirable
                crystalline silica primarily relate to its size and surface
                characteristics. Researchers believe that the size and surface
                characteristics play important roles in how respirable crystalline
                silica causes tissue damage. Any factor that influences or modifies
                these physical characteristics may alter the toxicity of respirable
                crystalline silica by affecting the mechanistic processes (OSHA, 2013b;
                ATSDR, 2019).
                 Inflammation pathways affect disease development in various systems
                and tissues in the human body. For instance, it has been proposed that
                lung fibrosis caused by exposure to respirable crystalline silica
                results from a cycle of cell damage, oxidant generation, inflammation,
                scarring, and ultimately fibrosis. This has been reported by Nolan et
                al. (1981), Shi et al. (1989, 1998), Lapp and Castranova (1993), Brown
                and Donaldson (1996), Parker and Banks (1998), Castranova and
                Vallyathan (2000), Castranova (2004), Fubini et al. (2004), Hu et al.
                (2017), Benmerzoug et al. (2018), and Yu et al. (2020).
                 Respirable crystalline silica entering the lungs could cause damage
                by a variety of mechanisms, including direct damage to lung cells. In
                addition, activation or stimulation by respirable crystalline silica of
                alveolar macrophages (after phagocytosis) and/or alveolar epithelial
                cells may lead to: (1) release of cytotoxic enzymes, reactive oxygen
                species (ROS), reactive nitrogen species (RNS), inflammatory cytokines
                and chemokines, (2) eventual cell death with the release of respirable
                crystalline silica, and (3) recruitment and activation of
                polymorphonuclear leukocytes (PMNs) and additional alveolar
                macrophages. The elevated production of ROS/RNS would result in
                oxidative stress and lung injury that stimulates alveolar macrophages,
                ultimately resulting in fibroblast activation and pulmonary fibrosis.
                The prolonged recruitment of macrophages and PMN causes a persistent
                inflammation, regarded as a primary step in the development of
                silicosis.
                 The strong immune response in the lung following exposure to
                respirable
                [[Page 44872]]
                crystalline silica may also be linked to a variety of extra-pulmonary
                adverse effects such as hypergammaglobulinemia, production of
                rheumatoid factor, anti-nuclear antibodies, and release of other immune
                complexes (Parks et al., 1999, Haustein and Anderegg, 1988; Green and
                Vallyathan, 1996). Respirable crystalline silica exposure has also been
                associated with nonmalignant renal disease through the initiation of
                immunological injury to the glomerulus of the kidney (Calvert et al.,
                1997).
                 Proposed mechanisms involved in respirable crystalline silica-
                induced carcinogenesis have included: direct DNA damage, inhibition of
                the p53 tumor suppressor gene, loss of cell cycle regulation;
                stimulation of growth factors, and production on oncogenes (Brown and
                Donaldson, 1996; Castranova, 2004; Fubini et al., 2004; Nolan et al.,
                1981; Shi et al., 1989, 1998).
                B. Diseases
                1. Silicosis
                 Silicosis is a progressive occupational disease that has long been
                identified as a cause of lung disease in miners. Based on its review of
                the literature, MSHA has preliminarily determined that exposure to
                respirable crystalline silica causes silicosis (acute silicosis,
                accelerated silicosis, simple chronic silicosis, and PMF) in MNM and
                coal miners, which is a significant cause of serious morbidity and
                early mortality in this occupational cohort (Mazurek and Attfield,
                2008; Mazurek and Wood, 2008a, 2008b; Mazurek et al., 2015, 2018).
                 When respirable crystalline silica particles accumulate in the
                lungs, they cause an inflammatory reaction, leading to lung damage and
                scarring. Silicosis can continue to develop even after silica exposure
                has ceased. It is not reversible, and there is only symptomatic
                treatment, including bronchodilators to maintain open airways, oxygen
                therapy, and lung transplants in the most severe cases (Cochrane et
                al., 1956; Ng et al., 1987a; Lee et al., 2001; Mohebbi and Zubeyri,
                2007; Kimura et al., 2010; Laney et al., 2017; Almberg et al., 2020;
                Hall et al., 2022).
                 Respirable crystalline silica exposure in MNM miners can lead to
                all three forms of silicosis (acute, accelerated, and chronic). These
                forms differ in the rate of exposure, pathology (i.e., the structural
                and functional changes produced by the disease), and latency period
                from exposure to disease onset. Acute silicosis is an aggressive
                inflammatory process following intense exposure to respirable
                crystalline silica for ``periods measured in months rather than years''
                (Cowie and Becklake, 2016). It causes alveolar proteinosis
                (accumulation of lipoproteins in the alveoli of the lungs). This
                restructuring of the lungs leads to symptoms such as coughing and
                difficult or labored breathing, and it often progresses to profound
                disability and death due to respiratory failure or infectious
                complications. In addition, symptoms often advance even after exposure
                has stopped, primarily due to the massive amount of protein debris and
                fluid that collects in the alveoli, which can suffocate the patient.
                The radiographic (X-ray) appearance and results of microscopic
                examination of acute silicosis are like those of idiopathic pulmonary
                alveolar proteinosis.
                 Chronic silicosis is the most frequently observed form of silicosis
                in the United States today (Banks, 2005; OSHA, 2013b; Cowie and
                Becklake, 2016). It is also the most common form of silicosis diagnosed
                in miners. Chronic silicosis is a fibrotic process that typically
                follows less intense respirable crystalline silica exposure of 10 or
                more years (Becklake, 1994; Balaan and Banks, 1998; NIOSH, 2002b,
                Kambouchner and Bernaudin, 2015; Cowie and Becklake, 2016; Rosental,
                2017; ATSDR, 2019; Barnes et al., 2019; Hoy and Chambers, 2020). It is
                identified by the presence of the silicotic islet or nodule that is an
                agent-specific fibrotic lesion and is recognized by its pathology
                (Balaan and Banks, 1998). Chronic silicosis develops slowly and creates
                rounded whorls of scar tissue that progressively destroy the normal
                structure and function of the lungs. In addition, the scar tissue
                opacities become visible by chest X-ray or computerized tomography (CT)
                only after the disease is well established and the lesions become large
                enough to view. As a result, surveys based on chest X-ray films usually
                underestimate the true prevalence of silicosis (Craighead and
                Vallathol, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and
                Velho, 2002). However, the lesions eventually advance and result in
                lung restriction, reduced lung volumes, decreased pulmonary compliance,
                and reduction in the gas exchange capabilities of the lungs (Balaan and
                Banks, 1998). As the disease progresses, affected miners may have a
                chronic cough, sputum production, shortness of breath, and reduced
                pulmonary function.
                 Accelerated silicosis includes both inflammation and fibrosis and
                is associated with intense respirable crystalline silica exposure.
                Accelerated silicosis usually manifests over a period of 3 to 10 years
                (Cowie and Becklake, 2016), but it can develop in as little as 2 to 5
                years if exposure is sufficiently intense (Davis, 1996). Accelerated
                silicosis may have features of both chronic and acute silicosis (i.e.,
                alveolar proteinosis in addition to X-ray evidence of fibrosis).
                Although the symptoms are similar to those of chronic silicosis, the
                clinical and radiographic progression of accelerated silicosis evolves
                more rapidly, and often leads to PMF, severe respiratory impairment,
                and respiratory failure. Accelerated silicosis can progress with
                associated morbidity and mortality, even if exposure ceases.
                 Among coal miners, silicosis is usually found in conjunction with
                simple coal worker's pneumoconiosis (CWP) (Castranova and Vallyathan,
                2000) because of their exposures to RCMD that contains respirable
                crystalline silica. Coal miners also face an added risk of developing
                mixed-dust pneumoconiosis (MDP) (includes the presence of coal dust
                macules), mixed-dust fibrosis (MDF), and/or silicotic nodules (Honma et
                al., 2004, see Figure 2, Green 2019). The autopsy studies on coal
                miners that MSHA reviewed support a pathological relationship between
                mixed-RCMD or respirable crystalline silica exposures and PMF,
                silicosis, and CWP (Attfield et al., 1994; Cohen et al., 2016, 2019,
                2022; Davis et al., 1979; Douglas et al., 1986; Fernie and Ruckley,
                1987; Green et al., 1989, 1998b; Ruckley et al., 1981, 1984; Vallyathan
                et al., 2011). Autopsy studies in British coal miners indicated that
                the more advanced the disease, the more mixed coal mine dust components
                were retained in the lung tissue (Ruckley et al., 1984; Douglas et al.,
                1986). Green et al. (1998b) determined that of 4,115 coal miners with
                pneumoconiosis autopsied as part of the National Coal Workers' Autopsy
                Study (NCWAS), 39 percent had mixed dust nodules and 23 percent had
                silicotic nodules.
                 PMF or ``complicated silicosis'' has been diagnosed in both coal
                and MNM miners exposed to dusts containing respirable crystalline
                silica. Recent literature on the pathophysiology of PMF supports the
                importance of crystalline silica as a cause of PMF in silica-exposed
                workers such as coal miners from the United States (Cohen et al., 2016,
                2022), sandblasters (Abraham and Wiesenfeld, 1997; Hughes et al.,
                1982), industrial sand workers (Vacek et al., 2019), hard rock miners
                (Verma et al., 1982, 2008), and gold miners (Carneiro et al., 2006a;
                Tse et al., 2007b).
                [[Page 44873]]
                a. Classifying Radiographic Findings of Silicosis
                 Two classification methods used to characterize the radiographic
                findings of silicosis in chest X-rays are described in this literature
                review: the International Labour Office (ILO) Standardized System and
                the Chinese categorization system.\16\
                ---------------------------------------------------------------------------
                 \16\ The ``Radiological Diagnostic Criteria of Pneumoconiosis
                and Principles for Management of Pneumoconiosis'' (GB5906-86) (Chen
                et al., 2001; Yang et al., 2006).
                ---------------------------------------------------------------------------
                 To describe the presence and severity of pneumoconiosis from chest
                X-rays or digital radiographic images, the ILO developed a standardized
                system to classify the opacities identified (ILO, 1980, 2002, 2011,
                2022). The ILO system grades the size, shape, and profusion (frequency)
                of opacities in the lungs. The density of opacities is classified on a
                4-point major category scale (category 0, 1, 2, or 3), with each major
                category divided into three subcategories, giving a 12-point scale
                between 0/- and 3/+. Differences between ILO categories are subtle. For
                each subcategory, the top number indicates the major category that the
                profusion most closely resembles, and the bottom number indicates the
                major category that was given secondary consideration. For example,
                film readers may assign classifications such as 1/0, which means the
                reader classified it as category 1, but category 0 (normal) was also
                considered (ILO, 2022). Major category 0 indicates the absence of
                visible opacities and categories 1 to 3 reflect increasing profusion of
                opacities and a concomitant increase in severity of disease.
                 MSHA's analysis of silicosis studies uses NIOSH's surveillance case
                definition to determine the presence of silicosis. NIOSH defines the
                presence of silicosis in terms of the ILO system and considers a small
                opacity profusion score of 1/0 or greater to indicate pneumoconiosis
                (NIOSH, 2014b). This definition originated from testimony before
                Congress regarding the 1969 Coal Act where the Public Health Service
                recommended that miners be removed from dusty environments as soon as
                they showed ``minimal effects'' of dust exposure on a chest X-ray
                (i.e., pinpoint, dispersed micro-nodular lesions).\17\ MSHA interprets
                ``minimal effects'' to mean an X-ray ILO profusion score of category 1/
                0 or greater.
                ---------------------------------------------------------------------------
                 \17\ On March 26, 1969, Charles C. Johnson, Jr., Administrator,
                Consumer Protection and Environmental Health Service, PHS, U.S.
                Department of Health, Education, and Welfare, testified before the
                General Subcommittee on Labor and presented remarks of the Surgeon
                General. They are referenced in the 91st Congress House of
                Representatives Report, 1st Session No. 91-563, Federal Coal Mine
                Health and Safety Act, October 13, 1969 (https://arlweb.msha.gov/SOLICITOR/COALACT/69hous.htm).
                ---------------------------------------------------------------------------
                 However, some studies in MSHA's literature review use the Chinese
                categorization scheme, which includes four categories of silicosis: a
                suspected case (0+), stage I, stage II, or stage III. The four
                categories correspond to ILO profusion category 0/1, category 1,
                category 2, and category 3, respectively. A suspected case of silicosis
                (0+) in a dust-exposed worker refers to a dust response in the lung and
                its corresponding lymph nodes, or a scale and severity of small
                opacities that fall short of the level observed in a stage I case of
                silicosis (Chen et al., 2001; Yang et al., 2006). Under this scheme, a
                panel of three radiologists determines the presence and severity of
                radiographic changes consistent with pneumoconiosis.
                b. Progression and Associated Impairment
                 Progression of silicosis is shown when there are changes or
                worsening of the opacities in the lungs, and sequential chest
                radiographs are classified higher by one or more subcategories (e.g.,
                from 1/0 to 1/1) because of changes in the location, thickness, or
                extent of lung abnormalities and/or the presence of calcifications. The
                higher the category number, the more severe the disease. Due to the
                uncertainty in scoring films, some investigators count progression as
                advancing two or more subcategories, such as 1/0 to 1/2.
                 MSHA reviewed studies referenced by OSHA (2013b) that examined the
                relationship between exposure and progression, as well as between X-ray
                findings and pulmonary function. Additionally, MSHA considered more
                recent literature (Dumavibhat et al., 2013; Mohebbi and Zubeyri, 2007;
                Wade et al., 2011) not previously reviewed by OSHA (2013b).
                 Overall, the studies indicate that progression is more likely with
                continued exposure, especially high average levels of exposure.
                Progression is also more likely for miners with higher ILO profusion
                classifications. As discussed previously, progression of disease may
                continue after miners are no longer exposed to respirable crystalline
                silica (Almberg et al., 2020; Cochrane et al., 1956; Hall et al.,
                2020b; Hurley et al., 1987; Kimura et al., 2010; Maclaren et al.,
                1985). In addition, although lung function impairment is highly
                correlated with chest X-ray films indicating silicosis, researchers
                cautioned that respirable crystalline silica exposure could impair lung
                function before it is detected by X-ray.
                 Of the studies in which silicosis progression was documented in
                populations of workers, four included quantitative exposure data that
                were based on either existing exposure levels or historical
                measurements of respirable crystalline silica (Hessel et al., 1988
                study of gold miners; Miller and MacCalman, 2010 study of coal miners;
                Miller et al., 1998 study of coal miners; Ng et al., 1987a study of
                granite miners). In some studies, episodic exposures to high average
                concentrations were documented and considered in the analysis. These
                exposures were strong predictors of more rapid progression beyond that
                predicted by cumulative exposure alone. Otherwise, the variable most
                strongly associated in these studies with progression of silicosis was
                cumulative respirable crystalline silica exposure (i.e., the product of
                the concentration times duration of exposure, which is summed over
                time) (Hessel et al., 1988; Ng et al., 1987a; Miller and MacCalman,
                2010; Miller et al., 1998). In the absence of concentration
                measurements, duration of employment in specific occupations known to
                involve exposure to high levels of respirable dust has been used as a
                surrogate for cumulative exposure to respirable crystalline silica. It
                has also been found to be associated with the progression of silicosis
                (Ogawa et al., 2003a).
                 Miller et al. (1998) examined the impact of high quartz exposures
                on silicosis disease progression on 547 British coal miners from 1990
                to 1991 and evaluated chest X-ray changes after the mines closed in
                1981. The study reviewed chest X-rays taken during health surveys
                conducted between 1954 and 1978 and data from extensive exposure
                monitoring conducted between 1964 and 1978. For some occupations,
                exposure was high because miners had to dig through a sandstone stratum
                to reach the coal. For example, quarterly mean respirable crystalline
                silica (quartz) concentrations ranged from 1,000 to 3,000 [micro]g/m\3\
                (1-3 mg/m\3\), and for a brief period, concentrations exceeded 10,000
                [micro]g/m\3\ (10 mg/m\3\) for one job. Some of these high exposures
                were associated with accelerated disease progression.
                 Buchanan et al. (2003) reviewed the exposure history and chest X-
                ray progression of 371 retired miners and found that short-term
                exposures (i.e., ``a few months'') to high concentrations of respirable
                crystalline silica (e.g., >2,000 [mu]g/m\3\, >2 mg/m\3\) increased the
                silicosis risk by three-fold (compared to the risk of cumulative
                exposure alone) (see the
                [[Page 44874]]
                separate Preliminary Risk Analysis document).
                 The risks of increased rate of progression, predicted by Buchanan
                et al. (2003) have been seen in coal miners (e.g., Cohen et al., 2016;
                Laney et al., 2010, 2017; Miller et al., 1998), metal (Hessel et al.,
                1988; Hnizdo and Sluis-Cremer, 1993; Nelson, 2013), and nonmetal miners
                such as silica plant and ground silica mill workers, whetstone cutters,
                and silica flour packers (Mohebbi and Zubeyri, 2007; NIOSH 2000a,b;
                Ogawa et al., 2003a). Accordingly, it is important to limit higher
                exposures to respirable crystalline silica in order to minimize the
                risk of rapid progressive pneumoconiosis (RPP) in miners.
                 The results of many surveillance studies conducted by NIOSH as part
                of the Coal Workers' Health Surveillance Program indicate that the
                pathology of pneumoconiosis in coal miners has changed over time, in
                part due to increased exposure to respirable crystalline silica. The
                studies of Cohen et al. (2016, 2022) indicate that a RPP develops due
                to increased exposure to respirable crystalline silica among
                contemporary coal miners as compared to historical coal miners. Through
                the examination of pathologic materials from 23 contemporary (born in
                or after 1930) and 62 historical coal miners (born between 1910 and
                1930) with severe pneumoconiosis, who were autopsied as part of NCWAS,
                Cohen et al. (2022) found a significantly higher proportion of silica-
                type PMF among contemporary miners (57 percent vs. 18 percent, p
                1)
                percent predicted, 1.0 percent (95 percent CI, 0.6 percent-1.3 percent)
                forced vital capacity (FVC) percent predicted, and 0.6 percent (95
                percent CI, 0.4 percent-0.8 FEV1/FVC).
                 Overall, MSHA preliminarily agrees with OSHA's conclusion that
                substantial evidence suggests that occupational exposure to respirable
                crystalline silica increases the risk of silicosis. MSHA also
                preliminarily concludes that respirable crystalline silica exposure
                increases the risk of silicosis morbidity and early mortality among
                miners.
                d. Surveillance Data
                 In addition to occupation-based epidemiological studies, MSHA
                reviewed surveillance studies, which provide and interpret data to
                facilitate the prevention and control of disease, and preliminarily
                finds that the prevalence of silicosis generally increases with
                duration of exposure (work tenure). However, the available statistics
                may underestimate silicosis-related morbidity and mortality in miners.
                For example, the following have been reported: (1) misclassification of
                causes of death (e.g., as TB, chronic bronchitis, emphysema, or cor
                pulmonale); (2) errors in recording occupation on death certificates;
                and (3) misdiagnosis of disease (Windau et al., 1991; Goodwin et al.,
                2003; Rosenman et al., 2003, Blackley et al., 2017). Furthermore, chest
                X-ray findings may lead to missed silicosis cases when fibrotic changes
                in the lung are not yet visible on chest X-rays. In other words,
                silicosis may be present but not yet detectable by chest X-ray, or may
                be more severe than indicated by the assigned profusion score
                (Craighead and Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al.,
                1997).
                e. Pulmonary Tuberculosis
                 Finally, in addition to the relationship between silica exposure
                and silicosis, studies indicate a relationship between silica exposure,
                silicosis, and pulmonary TB. OSHA reviewed these and concluded that
                silica exposure and silicosis increase the risk of pulmonary TB (Cowie,
                1994; Hnizdo and Murray, 1998; teWaterNaude et al., 2006). MSHA agrees
                with this conclusion.
                 Although early descriptions of dust diseases of the lung did not
                distinguish between TB and silicosis and most fatal cases described in
                the first half of the 20th century were likely a combination of
                silicosis and TB (Castranova et al., 1996), more recent findings have
                demonstrated that respirable crystalline silica exposure, even without
                silicosis, increases the risk of infectious (i.e., active) pulmonary TB
                (Sherson and
                [[Page 44875]]
                Lander, 1990; Cowie, 1994; Hnizdo and Murray, 1998; teWaterNaude et
                al., 2006). These co-morbid conditions hasten the development of
                respiratory impairment and increased mortality risk even beyond the
                risk in unexposed persons with active TB (Banks, 2005).
                 Ng and Chan (1991) hypothesized that silicosis and TB ``act
                synergistically'' (i.e., are more than additive) to increase fibrotic
                scar tissue (leading to massive fibrosis) or to enhance susceptibility
                to active mycobacterial infection. The authors found that lung fibrosis
                is common to both diseases, and that both diseases decrease the ability
                of alveolar macrophages to aid in the clearance of dust or infectious
                particles.
                 These findings are also supported by new studies (Ndlovu et al.,
                2019; Oni and Ehrlich, 2015) published since OSHA's review (2013b). Oni
                and Ehrlich (2015) reviewed a case of silico-TB in a former gold miner
                with ILO category 2/2 silicosis. Ndlovu et al. (2019) found that in a
                study sample of South African gold miners who had died from causes
                other than silicosis between 2005 and 2015, 33 percent of men (n = 254)
                and 43 percent of women (n = 29) at autopsy were found to have TB,
                whereas 7 percent of men (n = 54) and 3 percent of women (n = 4) were
                found to have pulmonary silicosis.
                 Overall, MSHA agrees with OSHA's conclusion that silica exposure
                increases the risk of pulmonary TB and that pulmonary TB is a
                complication of chronic silicosis.
                2. Nonmalignant Respiratory Disease (Excluding Silicosis)
                 In addition to causing silicosis (acute silicosis, accelerated
                silicosis, simple chronic silicosis, and PMF), exposure to respirable
                crystalline silica causes other NMRD. NMRD includes emphysema and
                chronic bronchitis, which are both diagnoses within the category of
                COPD. Patients with COPD may have chronic bronchitis, emphysema, or
                both (ATS, 2010a).
                 Based on its review of the literature, MSHA preliminarily concludes
                that exposure to respirable crystalline silica increases the risk for
                mortality from NMRD. The following summarizes MSHA's review of the
                literature.
                a. Emphysema
                 Emphysema involves the destruction of lung architecture in the
                alveolar region, causing airway obstruction and impaired gas exchange.
                In its literature review, OSHA (2013b) concluded that exposure to
                respirable crystalline silica can increase the risk of emphysema,
                regardless of whether silicosis is present. OSHA also concluded that
                this is the case for smokers and that smoking amplifies the effects of
                respirable crystalline silica exposure, increasing the risk of
                emphysema. MSHA reviewed the studies cited by OSHA and agrees with its
                conclusion. The studies reviewed are summarized below.
                 Becklake et al. (1987) determined that a miner who had worked in a
                high dust environment for 20 years had a greater chance of developing
                emphysema than a miner who had never worked in a high dust environment.
                In a retrospective cohort study, Hnizdo et al. (1991a) used autopsy
                lung specimens from 1,553 white gold miners to investigate the types of
                emphysema caused by respirable crystalline silica and found that the
                occurrence of emphysema was related to both smoking and dust exposure.
                This study also found a significant association between emphysema (both
                panacinar and centriacinar emphysema types) and length of employment
                for miners working in high dust occupations. A separate study by Hnizdo
                et al. (1994) on life-long non-smoking South African gold miners found
                that the degree of emphysema was significantly associated with the
                degree of hilar gland nodules, which the authors suggested might serve
                as a surrogate for respirable crystalline silica exposure. While Hnizdo
                et al. (2000) conversely found that emphysema prevalence was decreased
                in relation to dust exposure, the authors suggested that selection bias
                was responsible for this finding.
                 The findings of several cross-sectional and case-control studies
                discussed in the OSHA (2013b) Health Effects Literature were more
                mixed. For example, de Beer et al. (1992) found an increased risk for
                emphysema; however, the reported odds ratio (OR) was smaller than
                previously reported by Becklake et al. (1987).
                 The OSHA (2013b) Health Effects Literature also recognized that
                several of the referenced studies (Becklake et al., 1987 Hnizdo et al.,
                1994) found that emphysema might occur in respirable crystalline
                silica-exposed workers who did not have silicosis and suggested a
                causal relationship between respirable crystalline silica exposure and
                emphysema. Experimental (animal) studies found that emphysema occurred
                at lower respirable crystalline silica exposure concentrations than
                fibrosis in the airways or the appearance of early silicotic nodules
                (Wright et al., 1988). These findings tended to support human studies
                that respirable crystalline silica-induced emphysema can occur absent
                signs of silicosis.
                 Green and Vallyathan (1996) reviewed several studies of emphysema
                in workers exposed to silica and found an association between
                cumulative dust exposure and death from emphysema. The IARC (1997) also
                reviewed several studies and concluded that exposure to respirable
                crystalline silica increases the risk of emphysema. Finally, NIOSH
                (2002b) concluded in its Hazard Review that occupational exposure to
                respirable crystalline silica is associated with emphysema. However,
                some epidemiological studies suggested that this effect might be less
                frequent or absent in non-smokers.
                 Overall, MSHA agrees with OSHA that exposure to respirable
                crystalline silica causes emphysema even in the absence of silicosis.
                b. Chronic Bronchitis
                 Chronic bronchitis is long-term inflammation of the bronchi,
                increasing the risk of lung infections. This condition develops slowly
                by small increments and ``exists'' when it reaches a certain stage
                (i.e., the presence of a productive cough sputum production for at
                least 3 months of the year for at least 2 consecutive years) (ATS,
                2010b).
                 OSHA considered many studies that examined the association between
                respirable crystalline silica exposure and chronic bronchitis,
                concluding the following: (1) exposure to respirable crystalline silica
                causes chronic bronchitis regardless of whether silicosis is present;
                (2) an exposure-response relationship may exist; and (3) smokers may be
                at an increased risk of chronic bronchitis compared to non-smokers.
                MSHA has reviewed the literature and agrees with OSHA's conclusions.
                 Miller et al. (1997) reported a 20 percent increased risk of
                chronic bronchitis in a British mining cohort compared to the disease
                occurrence in the general population. Using British pneumoconiosis
                field research data, Hurley et al. (2002) calculated estimates of
                mixed-RCMD-related disease in British coal miners at exposure levels
                that were common in the late 1980s and related their lung function and
                development of chronic bronchitis with their cumulative dust exposure.
                The authors estimated that by the age of 58, 5.8 percent of these men
                would report breathlessness for every 100 gram-hour/m\3\ dust exposure.
                The authors also estimated the prevalence of chronic bronchitis at age
                58 would be 4 percent per 100 gram-hour/m\3\ of dust exposure. These
                miners averaged over 35 years of tenure in mining and a cumulative
                respirable dust exposure of 132 gram-hour/m\3\.
                 Cowie and Mabena (1991) found that chronic bronchitis was present
                in 742 of
                [[Page 44876]]
                1,197 (62 percent) black South African gold miners, and Ng et al.
                (1992b) found a higher prevalence of respiratory symptoms, independent
                of smoking and age, in Singaporean granite quarry workers exposed to
                high levels of dust (rock drilling and crushing) compared to those
                exposed to low levels of dust (maintenance and transport workers).
                However, Irwig and Rocks (1978) compared symptoms of chronic bronchitis
                in silicotic and non-silicotic South African gold miners and did not
                find as clear a relationship as did the above studies, concluding that
                the symptoms were not statistically more prevalent in the silicotic
                miners, although prevalence was slightly higher.
                 Sluis-Cremer et al. (1967) found that dust-exposed male smokers had
                a higher prevalence of chronic bronchitis than non-dust exposed smokers
                in a gold mining town in South Africa. Similarly, Wiles and Faure
                (1977) found that the prevalence of chronic bronchitis rose
                significantly with increasing dust concentration and cumulative dust
                exposure in South African gold miners of smokers, nonsmokers, and ex-
                smokers. Rastogi et al. (1991) found that female grinders of agate
                stones in India had a significantly higher prevalence of acute
                bronchitis, but they had no increase in the prevalence of chronic
                bronchitis compared to controls matched by socioeconomic status, age,
                and smoking. However, the study noted that respirable crystalline
                silica exposure durations were very short, and control workers may also
                have been exposed to respirable crystalline silica.
                 Studies examining the effect of years of mining on chronic
                bronchitis risk were mixed. Samet et al. (1984) found that prevalence
                of symptoms of chronic bronchitis was not associated with years of
                mining in a population of underground uranium miners, even after
                adjusting for smoking. However, Holman et al. (1987) studied gold
                miners in West Australia and found that the prevalence of chronic
                bronchitis, as indicated by ORs (controlled for age and smoking), was
                significantly increased in those that had worked in the mines for over
                1 year, compared to lifetime non-miners. In addition, while other
                studies found no effect of years of mining on chronic bronchitis risk,
                those studies often qualified this result with possible confounding
                factors. For example, Kreiss et al. (1989) studied 281 hard-rock
                (molybdenum) miners and 108 non-miner residents of Leadville, Colorado.
                They did not find an association between the prevalence of chronic
                bronchitis and work in the mining industry (Kreiss et al., 1989);
                however, it is important to note that the mine had been temporarily
                closed for 5 months when the study began, so miners were not exposed at
                the time of the study.
                 The American Thoracic Society (ATS) (1997) published a review
                finding chronic bronchitis to be common among worker groups exposed to
                dusty environments contaminated with respirable crystalline silica.
                NIOSH (2002b) also published a review finding that occupational
                exposure to respirable crystalline silica has been associated with
                bronchitis; however, some epidemiological studies suggested this effect
                might be less frequent or absent in non-smokers.
                 Finally, Hnizdo et al. (1990) found an independent exposure-
                response relationship between respirable crystalline silica exposure
                and impaired lung function. For miners with less severe impairment, the
                effects of smoking and dust together were additive. However, for miners
                with the most severe impairment, the effects of smoking and dust were
                synergistic (i.e., more than additive).
                 Overall, MSHA agrees with OSHA's conclusion that exposure to
                respirable crystalline silica causes chronic bronchitis regardless of
                whether silicosis is present and that an exposure-response relationship
                may exist.
                c. Pulmonary Function Impairment
                 Pulmonary function impairment, generally defined as reduction below
                the lower limit of normal predicted by reference equations (and in
                older literature as less than 80 percent predicted) of diffusion
                capacity for carbon monoxide (DLCOcSB), total lung capacity (TLC), FVC,
                or FEV1 is also a common condition of NMRD. Based on its
                review of the evidence in numerous longitudinal and cross-sectional
                studies and reviews, OSHA concluded that there is an exposure-response
                relationship between respirable crystalline silica and the development
                of impaired lung function. OSHA also concluded that the effect of
                tobacco smoking on this relationship may be additive or synergistic,
                and workers who were exposed to respirable crystalline silica but did
                not show signs of silicosis may also have pulmonary function
                impairment. MSHA has reviewed the studies cited by OSHA and agrees with
                their conclusions.
                 OSHA reviewed several longitudinal studies regarding the
                relationship between respirable crystalline silica exposure and
                pulmonary function impairment. To evaluate whether exposure to silica
                affects pulmonary function in the absence of silicosis, the studies
                focused on workers who did not exhibit progressive silicosis.
                 Among both active and retired Vermont granite workers exposed to an
                average quartz dust exposure level of 60 [micro]g/m\3\, researchers
                found no exposure-related decreases in pulmonary function (Graham et
                al., 1981, 1994). However, Eisen et al. (1995) found significant
                pulmonary decrements among a subset of granite workers who left work
                and consequently did not voluntarily participate in the last of a
                series of annual pulmonary function tests (termed ``dropouts''). This
                group experienced steeper declines in lung function compared to the
                subset of workers who remained at work and participated in all tests
                (termed ``survivors''), and these declines were significantly related
                to dust exposure. Exposure-related changes in lung function were also
                reported in a 12-year study of granite workers (Malmberg et al., 1993),
                in two 5-year studies of South African miners (Hnizdo, 1992; Cowie,
                1998), and in a study of foundry workers whose lung function was
                assessed between 1978 and 1992 (Hertzberg et al., 2002). Similar
                reductions in FEV1 (indicating an airway obstruction) were
                linked to respirable crystalline silica exposure.
                 Each of these studies reported their findings in terms of rates of
                decline in any of several pulmonary function measures (e.g.,
                FEV1, FVC, FEV1/FVC). To put these declines in
                perspective, Eisen et al. (1995) reported that the rate of decline in
                FEV1 seen among the dropout subgroup of Vermont granite
                workers was 4 ml per 1,000 [micro]g/m\3\-year (4 ml per mg/m\3\-year)
                of exposure to respirable granite dust. By comparison, FEV1
                declines at a rate of 10 ml/year from smoking one pack of cigarettes
                daily. From their study of foundry workers, Hertzberg et al. (2002)
                reported a 1.1 ml/year decline in FEV1 and a 1.6 ml/year
                decline in FVC for each 1,000 [micro]g/m\3\-year (1 mg/m\3\-year) of
                respirable crystalline silica exposure after controlling for ethnicity
                and smoking. From these rates of decline, they estimated that exposure
                to 100 [micro]g/m\3\ of respirable crystalline silica for 40 years
                would result in a total loss of FEV1 and FVC that was less
                than, but still comparable to, smoking a pack of cigarettes daily for
                40 years. Hertzberg et al. (2002) also estimated that exposure to the
                existing MSHA standard (100 [micro]g/m\3\) for 40 years would increase
                the risk of developing abnormal FEV1 or FVC by factors of
                1.68 and 1.42, respectively.
                 OSHA reviewed cross-sectional studies that described relationships
                between lung function loss and respirable crystalline silica exposure
                or
                [[Page 44877]]
                exposure measurement surrogates (e.g., tenure). The results of these
                studies were similar to those longitudinal studies already discussed.
                In several studies, respirable crystalline silica exposure was found to
                reduce lung function of:
                 White South African gold miners (Hnizdo et al., 1990),
                 Black South African gold miners (Cowie and Mabena, 1991;
                Irwig and Rocks, 1978),
                 Respirable crystalline silica-exposed workers in Quebec
                (B[eacute]gin et al., 1995),
                 Rock drilling and crushing workers in Singapore (Ng et
                al., 1992b),
                 Granite shed workers in Vermont (Theriault et al., 1974a,
                1974b),
                 Aggregate quarry workers and coal miners in Spain (Montes
                et al., 2004a, 2004b),
                 Concrete workers in the Netherlands (Meijer et al., 2001),
                 Chinese refractory brick manufacturing workers in an iron-
                steel plant (Wang et al., 1997),
                 Chinese gemstone workers (Ng et al., 1987b),
                 Hard-rock miners in Manitoba, Canada (Manfreda et al.,
                1982) and in Colorado (Kreiss et al., 1989),
                 Pottery workers in France (Neukirch et al., 1994),
                 Potato sorters in the Netherlands (Jorna et al., 1994),
                 Slate workers in Norway (Suhr et al., 2003), and
                 Men in a Norwegian community with years of occupational
                exposure to respirable crystalline silica (quartz) (Humerfelt et al.,
                1998).
                 The OSHA (2013b) Health Effects Literature recognized that many of
                these studies found that pulmonary function impairment: (1) can occur
                in respirable crystalline silica-exposed workers without silicosis, (2)
                was still observable when controlling for silicosis in the analysis,
                and (3) was related to the magnitude and duration of respirable
                crystalline silica exposure, rather than to the presence or severity of
                silicosis. Many other studies in the OSHA (2013b) Health Effects
                Literature have also found a relationship between respirable
                crystalline silica exposure and lung function impairment, including
                IARC (1997), the ATS (1997), and Hnizdo and Vallyathan (2003).
                 MSHA reviewed the studies and agrees with OSHA's finding that there
                is an exposure-response relationship between respirable crystalline
                silica and the impairment of lung function. MSHA also agrees with
                OSHA's finding that the effect of tobacco smoking on this relationship
                may be additive or synergistic, and that workers who were exposed to
                respirable crystalline silica, but did not show signs of silicosis, may
                also have pulmonary function impairment.
                3. Carcinogenic Effects
                a. Lung Cancer
                 Lung cancer, an irreversible and usually fatal disease, is a type
                of cancer that forms in lung tissue. Agreeing with the conclusion of
                other government and public health organizations that respirable
                crystalline silica is a ``known human carcinogen,'' MSHA has
                preliminarily found that the scientific literature supports that
                respirable crystalline silica exposure significantly increases the risk
                of lung cancer mortality among miners. This determination is consistent
                with the conclusions of other government and public health
                organizations, including the IARC (1997b, 2012), the NTP (2000, 2016),
                NIOSH (2002b), the ATS (1997), and the American Conference of
                Governmental Industrial Hygienists (ACGIH[supreg], (2010)). The
                Agency's determination is supported by epidemiological literature,
                encompassing more than 85 studies of occupational cohorts from more
                than a dozen industrial sectors including: granite/stone quarrying and
                processing (Carta et al., 2001; Attfield and Costello, 2004; Costello
                et al., 1995; Gu[eacute]nel et al., 1989a,b), industrial sand
                (Sanderson et al., 2000; Hughes et al., 2001; McDonald et al., 2001,
                2005; Rando et al., 2001; Steenland and Sanderson, 2001), MNM mining
                (Steenland and Brown, 1995a; deKlerk and Musk, 1998; Roscoe et al.,
                1995; Hessel et al., 1986, 1990; Hnizdo and Sluis-Cremer, 1991; Reid
                and Sluis-Cremer, 1996; Hnizdo et al., 1997; Chen et al., 1992;
                McLaughlin et al., 1992; Chen and Chen, 2002; Chen et al., 2006;
                Schubauer-Berigan et al., 2009; Hua et al., 1994; Meijers et al., 1991;
                Finkelstein 1998; Chen et al., 2012; Liu et al., 2017a; Wang et al.,
                2020a,b; Wang et al., 2021), coal mining (Meijers et al., 1988; Miller
                et al., 2007; Miller and MacCalman, 2010; Miyazaki and Une, 2001;
                Graber et al., 2014a,b; Tomaskova et al., 2012, 2017, 2020, 2022; Kurth
                et al., 2020), pottery (Winter et al., 1990; McLaughlin et al., 1992;
                McDonald et al., 1995), ceramic industries (Starzynski et al., 1996),
                diatomaceous earth (Checkoway et al., 1993, 1996, 1997, 1999; Seixas et
                al., 1997; Rice et al., 2001), and refractory brick industries
                (cristobalite exposures) (Dong et al., 1995).
                 The strongest evidence comes from the worldwide cohort and case-
                control studies reporting excess lung cancer mortality among workers
                exposed to respirable crystalline silica in various industrial sectors,
                confirmed by the 10-cohort pooled case-control analysis by Steenland et
                al. (2001a), the more recent pooled case-control analysis of seven
                European countries by Cassidy et al. (2007), and two national death
                certificate registry studies (Calvert et al., 2003 in the United
                States; Pukkala et al., 2005 in Finland).
                 Recent studies examined lung cancer mortality among coal and non-
                coal miners (Meijers et al., 1988, 1991; Starzynski et al., 1996;
                Miyazaki and Une, 2001; Tomaskova et al., 2012, 2017, 2020, 2022;
                Attfield and Kuempel, 2008; Graber et al., 2014a, 2014b; Kurth et al.,
                2020; NIOSH, 2019a). These studies also discuss the associations
                between RCMD and respirable crystalline silica exposures with lung
                cancer in coal mining populations. Furthermore, these newer studies are
                consistent with the conclusion of OSHA's final Quantitative Risk
                Assessment (QRA) (2016a) that respirable crystalline silica is a human
                carcinogen. MSHA preliminarily concludes that miners, both MNM and coal
                miners, are at risk of developing lung cancer due to their occupational
                exposure to respirable crystalline silica.
                 In addition, based on its review of the literature, MSHA has
                preliminarily determined that radiographic silicosis is a marker for
                lung cancer risk. Reducing exposure to levels that lower the silicosis
                risk would reduce the lung cancer risk to exposed miners (Finkelstein,
                1995, 2000; Brown, 2009). MSHA has also found that, based on the
                available epidemiological and animal data, respirable crystalline
                silica causes lung cancer (IARC, 2012; RTECS, 2016; ATSDR, 2019).
                Miners who inhale respirable crystalline silica over time are at
                increased risk of developing silicosis and lung cancer (Greaves, 2000;
                Erren et al., 2009; Tomaskova et al., 2017, 2020, 2022).
                 Toxicity studies provide additional evidence of the carcinogenic
                potential of respirable crystalline silica. Studies using DNA exposed
                directly to freshly fractured respirable crystalline silica demonstrate
                the direct effect respirable crystalline silica had on DNA breakage.
                Cell culture research has investigated the processes by which
                respirable crystalline silica disrupt normal gene expression and
                replication. Studies have demonstrated that chronic inflammatory and
                fibrotic processes resulting in oxidative and cellular damage may lead
                to neoplastic changes in the lung (Goldsmith, 1997). In addition, the
                biologically damaging physical characteristics of respirable
                crystalline silica and its direct and indirect
                [[Page 44878]]
                genotoxicity (Schins et al., 2002; Borm and Driscoll, 1996) support
                MSHA's preliminary determination that respirable crystalline silica is
                an occupational carcinogen.
                b. Cancers of Other Sites
                 In addition to lung cancer, OSHA reviewed studies examining the
                relationship between silica exposure and cancers at other sites. MSHA
                notes that OSHA reviewed these mortality studies (e.g., cancer of the
                larynx and the digestive system, including the stomach and esophagus)
                and found that studies suggesting a dose-response relationship were too
                limited in terms of size, study design, or potential for confounding
                variables to be conclusive. OSHA also pointed to the NIOSH (2002b)
                silica (respirable crystalline silica) hazard review, which concluded
                that no association has been established between respirable crystalline
                silica exposure and excess mortality from cancer at other sites. MSHA
                has reviewed these studies and agrees with OSHA's conclusion. The
                following summarizes the studies reviewed with inconclusive findings.
                (1) Laryngeal Cancer
                 Three lung cancer studies (Checkoway et al., 1997; Davis et al.,
                1983; McDonald et al., 2001) included in OSHA's health literature
                review suggest an association between respirable crystalline silica
                exposure and increased mortality from laryngeal cancer. However, a
                small number of cases were reported and researchers were unable to
                determine a statistically significant effect. Therefore, there is
                little evidence of an association based on these studies.
                (2) Gastric (Stomach) Cancer
                 OSHA reviewed several studies in its 2013b health literature review
                to assess a potential relationship between respirable crystalline
                silica exposures and stomach cancers. OSHA's literature review noted
                observations made previously by Cocco et al. (1996) and in the NIOSH
                respirable crystalline silica hazard review (2002b), which found that
                most epidemiological studies of respirable crystalline silica and
                stomach cancer did not sufficiently adjust for the effects of
                confounding factors. In addition, some of these studies were not
                properly designed to assess a dose-response relationship (e.g.,
                Finkelstein and Verma, 2005; Moshammer and Neuberger, 2004; Selikoff,
                1978; Stern et al., 2001) or did not demonstrate a statistically
                significant dose-response relationship (e.g., Calvert et al., 2003;
                Tsuda et al., 2001). For these reasons, MSHA determined these studies
                were inconclusive in the context of this rulemaking.
                (3) Esophageal Cancer
                 OSHA considered several studies that examined the relationship
                between respirable crystalline silica exposures and esophageal cancer
                and found that the studies were limited in terms of size, study design,
                or potential for confounding variables. Three nested case-control
                studies of Chinese workers demonstrated a dose-response association
                between increased risk of esophageal cancer mortality and respirable
                crystalline silica exposure (Pan et al., 1999; Wernli et al., 2006; Yu
                et al., 2005). Other studies (Tsuda et al., 2001; Xu et al., 1996a)
                also indicated elevated rates of esophageal cancer mortality with
                respirable crystalline silica exposure. However, OSHA noted that
                confounding factors due to other occupational exposures was possible.
                Additionally, two large national mortality studies in Finland and the
                United States did not show a positive association between respirable
                crystalline silica exposure and esophageal cancer mortality (Calvert et
                al., 2003; Weiderpass et al., 2003). MSHA agrees with OSHA's conclusion
                that the literature does not support attributing increased esophageal
                cancer mortality to exposure to respirable crystalline silica.
                (4) Other Sites
                 NIOSH (2002b) conducted a health literature review of the health
                effects potentially associated with respirable crystalline silica
                exposure, which identified only infrequent reports of statistically
                significant excesses of deaths for other cancers. Cancer studies have
                been reported in the following organs/systems: salivary gland, liver,
                bone, pancreas, skin, lymphopoietic or hematopoietic, brain, and
                bladder (see NIOSH, 2002b for full bibliographic references). However,
                the findings were not observed consistently among epidemiological
                studies, and NIOSH (2002b) concluded that no association has been
                established between these cancers and respirable crystalline silica
                exposure. OSHA concurred with NIOSH that these isolated reports of
                excess cancer mortality were insufficient to determine the role of
                respirable crystalline silica exposure.
                 Overall, OSHA concluded that evidence of an association between
                silica exposure and cancer at sites other than the lungs is not
                sufficient. MSHA agrees with OSHA's conclusion.
                4. Renal Disease
                 Renal disease is characterized by the loss of kidney function, and
                in the case of ESRD, the need for a regular course of long-term
                dialysis or a kidney transplant. MSHA reviewed a wide variety of
                longitudinal and mortality epidemiological studies, including case
                series, case-control, and cohort studies, as well as case reports, and
                preliminarily concludes that respirable crystalline silica exposure
                increases the risk of morbidity and/or mortality related to ESRD.
                However, MSHA notes that the available literature on respirable
                crystalline silica exposures and renal disease in coal miners is less
                conclusive than the literature related to MNM miners.
                 Epidemiological studies have found statistically significant
                associations between occupational exposure to respirable crystalline
                silica and chronic renal disease (e.g., Calvert et al., 1997), sub-
                clinical renal changes, including proteinuria and elevated serum
                creatinine (e.g., Ng et al., 1992a; Hotz et al., 1995; Rosenman et al.,
                2000), ESRD morbidity (e.g., Steenland et al., 1990), ESRD mortality
                (Steenland et al., 2001b, 2002a), and Wegener's granulomatosis (Nuyts
                et al., 1995) (severe injury to the glomeruli that, if untreated,
                rapidly leads to renal failure). The pooled analysis conducted by
                Steenland et al. (2002a) is particularly convincing because it involved
                a large number of workers from three combined cohorts and had well-
                documented, validated job exposure matrices. Steenland et al. (2002a)
                found a positive and monotonic exposure-response trend for both
                multiple-cause mortality and underlying cause data. MSHA has
                preliminarily determined that the underlying data from Steenland et al.
                (2002a) are sufficient to provide useful estimates of risk.
                 Possible mechanisms suggested for respirable crystalline silica-
                induced renal disease include: (1) a direct toxic effect on the kidney,
                (2) a deposition in the kidney of immune complexes (e.g.,
                Immunoglobulin A (IgA), an antibody blood protein) in the kidney
                following respirable crystalline silica-related pulmonary inflammation,
                and (3) an autoimmune mechanism (Gregorini et al., 1993; Calvert et
                al., 1997). Steenland et al. (2002a) demonstrated a positive exposure-
                response relationship between respirable crystalline silica exposure
                and ESRD mortality.
                 Overall, MSHA preliminarily determines that respirable crystalline
                silica exposure in mining increases the risk of renal disease.
                [[Page 44879]]
                5. Autoimmune Disease
                 Autoimmune diseases occur when the immune system mistakenly attacks
                healthy tissues within the body, causing inflammation, swelling, pain,
                and tissue damage. Examples include rheumatoid arthritis (RA), systemic
                lupus erythematosus (SLE), scleroderma, and systemic sclerosis (SSc).
                Based on its literature review, MSHA preliminarily concludes that there
                is a causal association between occupational exposure to respirable
                crystalline silica and the development of systemic autoimmune diseases
                in miners. However, no studies are available to date that can be used
                to model respirable crystalline silica-exposure risk in a formal
                quantitative risk analysis.
                 Wallden et al. (2020) found that respirable crystalline silica
                exposure is correlated with an increased risk of developing ulcerative
                colitis, which increases with duration of exposure (work tenure) and
                the level of exposure. This effect was especially significant in men.
                Schmajuk et al. (2019) found that RA was significantly associated with
                coal mining and other non-coal occupations exposed to respirable
                crystalline silica. Finally, Vihlborg et al. (2017) found a significant
                increased risk of seropositive RA with high exposure (>0.048 mg/m\3\)
                to respirable crystalline silica dust when compared to individuals with
                no or lower exposure by examining detailed exposure-response
                relationships across four different respirable crystalline silica dose
                groups (quartiles): 48 [micro]g/m\3\. However, these researchers did
                not report the risk of sarcoidosis and seropositive RA in relation to
                respirable crystalline silica exposure using logistic regressions
                resulting in models that could be used in the risk assessment. In
                addition, the meta-analysis of 19 published case-control and cohort
                studies on scleroderma by Rubio-Rivas et al. (2017) found statistically
                significant risks among individuals exposed to respirable crystalline
                silica, solvents, silicone, breast implants, epoxy resins, pesticides,
                and welding fumes, but did not provide detailed quantitative exposure
                information.
                C. Conclusion
                 MSHA preliminarily concludes that occupational exposure to
                respirable crystalline silica causes silicosis (acute silicosis,
                accelerated silicosis, simple chronic silicosis, and PMF), NMRD
                (including COPD), lung cancer, and kidney disease. Each of these
                effects is exposure-dependent, chronic, irreversible, potentially
                disabling, and can be fatal. MSHA suspects that respirable crystalline
                silica exposure is also linked to the development of some autoimmune
                disorders through inflammation pathways.
                 The scientific literature (including peer-reviewed medical,
                toxicological, public health, and other related disciplinary
                publications) is robust and compelling. It shows that miners exposed to
                the existing respirable crystalline silica limit of 100 [mu]g/m\3\
                still have an unacceptable amount of excess risk for developing and
                dying from diseases related to occupational respirable crystalline
                silica exposures and still suffer material impairments of health or
                functional capacity.
                VI. Preliminary Risk Analysis Summary
                 MSHA's preliminary risk analysis (PRA) quantifies risks associated
                with five specific health outcomes identified in the separate,
                standalone Health Effects document: silicosis morbidity and mortality,
                and mortality from NMRD, lung cancer, and ESRD. The standalone
                document, entitled Preliminary Risk Analysis (PRA document), has been
                placed into the rulemaking docket for the MSHA respirable crystalline
                silica rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is
                available on MSHA's website.
                 MSHA developed a PRA to support the risk determinations required to
                set an exposure limit for a toxic substance under the Mine Act. MSHA's
                PRA quantifies the health risk to miners exposed to respirable
                crystalline silica under the existing exposure limits for MNM and coal
                miners, at the proposed PEL of 50 [mu]g/m\3\, and at the proposed
                action level of 25 [mu]g/m\3\.
                 This analysis addresses three questions related to the proposed
                rule:
                 (1) whether potential health effects associated with existing
                exposure conditions constitute material impairment to any miner's
                health or functional capacity;
                 (2) whether existing exposure conditions place miners at risk of
                incurring any material impairment if regularly exposed for the period
                of their working life; and
                 (3) whether the proposed rule would reduce those risks.
                 To answer these questions, MSHA relied on the large body of
                research on the health effects of respirable crystalline silica and
                several published, peer-reviewed, quantitative risk assessments that
                describe the risk of exposed workers to silicosis mortality and
                morbidity, NMRD mortality, lung cancer mortality, and ESRD mortality.
                These assessments are based on several studies of occupational cohorts
                in a variety of industrial sectors. The underlying studies are
                described in the Health Effects document and are summarized in Section
                V. Health Effects Summary of this preamble.
                 This summary highlights the main findings from the PRA, briefly
                describes how they were derived, and directs readers interested in more
                detailed information to corresponding sections of the standalone PRA
                document.
                A. Summary of MSHA's Preliminary Risk Analysis Process and Methods
                 MSHA evaluated the literature and selected an exposure-response
                model for each of the five health endpoints--silicosis morbidity,
                silicosis mortality, NMRD mortality, lung cancer mortality, and ESRD
                mortality. The selected exposure-response models were used to estimate
                lifetime excess risks and lifetime excess cases among the current
                population of MNM and coal miners based on real exposure conditions, as
                indicated by the samples in the compliance sampling datasets.
                 MSHA's PRA is largely based on the methodology and findings from a
                peer-reviewed January 2013 OSHA preliminary quantitative risk
                assessment (PQRA) and associated analysis of health effects in
                connection with OSHA's promulgation of a rule setting PELs for
                workplace exposure to respirable crystalline silica. OSHA's PQRA
                presented quantitative relationships between respirable crystalline
                silica exposure and multiple health endpoints. Following multiple legal
                challenges, the U.S. Court of Appeals for the D.C. Circuit rejected
                challenges to OSHA's risk assessment methodology and its findings on
                different health risks. N. Am.'s Bldg. Trades Unions v. OSHA, 878 F.3d
                271, 283-89 (D.C. Cir. 2017).
                 MSHA's PRA presents detailed quantitative analyses of health risks
                over a range of exposure concentrations that have been observed in MNM
                and coal mines. MSHA applied exposure-response models to estimate the
                respirable crystalline silica-related risk of material impairment of
                health or functional capacity of miners exposed to respirable
                crystalline silica at three levels--(1) the existing standards, (2) the
                proposed PEL, and (3) the proposed action level. As in past MSHA
                rulemakings, MSHA estimated and compared lifetime excess risks
                associated with exposures at the existing and proposed PEL (and at the
                proposed action level) over a miner's full working life of 45 years.
                [[Page 44880]]
                 MSHA's PRA is also based on a compilation of miner exposure data to
                respirable crystalline silica. For the MNM sector, MSHA evaluated
                57,769 valid respirable dust samples collected between January 2005 and
                December 2019; and for the coal sector, MSHA evaluated 63,127 valid
                respirable dust samples collected between August 2016 and July 2021.
                The compiled data set characterizes miners' exposures to respirable
                crystalline silica in various locations (e.g., underground, surface),
                occupations (e.g., drillers, underground miners, equipment operators),
                and commodities (e.g., metal, nonmetal, stone, crushed limestone, sand
                and gravel, and coal). MSHA enforcement sampling indicates a wide range
                of exposure concentrations. These include exposures from below the
                proposed action level (25 [mu]g/m\3\) to above the existing standards
                (100 [mu]g/m\3\ in MNM standards, 100 [mu]g/m\3\ MRE in coal standards,
                which is approximately 85.7 [mu]g/m\3\ ISO).\18\
                ---------------------------------------------------------------------------
                 \18\ As discussed in the PRA, the existing PEL for coal is 100
                [mu]g/m\3\ MRE, measured as a full-shift time-weighted average
                (TWA). To calculate risks consistently for both coal and MNM miners,
                the PRA converts the MRE full-shift TWA concentrations experienced
                by coal miners to ISO 8-hour TWA concentrations. (See Section 4 of
                the PRA document for a full explanation.) The equation used to
                convert MRE full-shift TWA concentrations into ISO 8-hour TWA
                concentrations is:
                 ISO 8-hour TWA concentration = (MRE TWA) x (original sampling
                time)/(480 minutes) x 0.857
                 Exposures at TWA 100 [mu]g/m\3\ MRE and SWA 85.7 [mu]g/m\3\ ISO
                are only equivalent when the sampling duration is 480 minutes (eight
                hours). However, for the sake of simplicity and for comparison
                purposes, the risk analysis approximates exposures at the existing
                coal exposure limit of 100 MRE [mu]g/m\3\ as 85.7 [mu]g/m\3\ ISO.
                Thus, ISO concentration values (measured as an 8-hour TWA) were used
                as the exposure metric when (a) calculating risk under the
                assumption of full compliance with the existing standards and (b)
                calculating risk under the assumption that no exposure exceeds the
                proposed PEL of 50 [mu]g/m\3\. To simulate compliance among coal
                miners at the existing exposure limit, exposures were capped at 85.7
                [mu]g/m\3\ measured as an ISO 8-hour TWA.
                ---------------------------------------------------------------------------
                 The primary results of the PRA are the calculated number of deaths
                and illnesses avoided assuming full compliance after implementation of
                MSHA's proposed rule. These calculations were performed for non-fatal
                silicosis illnesses (morbidity) and for deaths (mortality) due to
                silicosis, lung cancer, NMRD, and ESRD. For each health outcome, the
                reduced number of illnesses or deaths is calculated as the difference
                between (a) the number of illnesses and deaths currently occurring in
                the industry, assuming mines fully comply with the existing standards
                (100 [mu]g/m\3\ for MNM and 85.7 [mu]g/m\3\ ISO for coal) and (b) the
                number of deaths and illnesses expected to occur following
                implementation of the proposed rule, which includes a proposed PEL of
                50 [mu]g/m\3\ for a full shift exposure, calculated as an 8-hour TWA.
                 Risks and cases were estimated under two scenarios: (a) a Baseline
                scenario where all exposures were capped at 100 [mu]g/m \3\ for MNM
                miners and at 85.7 [mu]g/m \3\ for coal miners, and (b) a proposed 50
                [mu]g/m \3\ scenario where all risks were capped at the proposed PEL of
                50 [mu]g/m \3\ for both MNM and coal miners. The difference between the
                two scenarios yields the estimated reduction in lifetime excess risks
                and in lifetime excess cases due to the proposed PEL.
                 To calculate risks, MSHA grouped MNM miners into the following
                exposure intervals: 25 to 50 to 100 to 250 to 500 [mu]g/m \3\. MSHA grouped coal miners into the
                following exposure intervals: 25 to 50 to 85.7
                to 100 to 250 to 500 [mu]g/m \3\. MSHA
                calculated the median of all exposure samples in each exposure interval
                and assumed the population of miners is distributed across the exposure
                intervals in proportion to the number of exposure samples from the
                compliance dataset in each interval. Then, miners were assumed to
                encounter constant exposure at the median value of their assigned
                exposure interval. MSHA adjusted the annual cumulative exposure by a
                full-time equivalency (FTE) factor to account for the fact that miners
                may experience more or less than 2,000 hours of exposure per year. MSHA
                calculated the FTE adjustment factor as the weighted average of the
                production employee FTE ratio (0.99 for MNM and 1.14 for coal) and the
                contract miner FTE ratio (0.59 for MNM and 0.64 for coal), where the
                weights are the number of miners (150,928 for MNM production employees,
                60,275 for MNM contract miners, 51,573 for coal production employees,
                and 22,003 for coal contract miners). For example, the weighted average
                FTE ratio for MNM is (0.987 x 150,928 + 0.591 x 60,275)/(150,928 +
                60,275) = 0.87 and is (1.139 x 51,573 + 0.636 x 22,003)/(51,573 +
                22,003) = 0.99 for coal.
                 MSHA calculated excess risk, which refers to the additional risk of
                disease and death attributable to exposure to respirable crystalline
                silica. For silicosis morbidity, MSHA used an exposure-response model
                that directly yields the accumulated or lifetime excess risk of
                silicosis morbidity, assuming there is no background rate \19\ of
                silicosis in an unexposed (i.e., non-miner) group. For the four
                mortality endpoints (silicosis mortality, lung cancer mortality, NMRD
                mortality, and ESRD mortality), MSHA used cohort life tables to
                calculate excess risks, assuming all miners begin working at age 21,
                retire at the end of age 65, and do not live past age 80. From the life
                tables, MSHA acquired the lifetime mortality risk by summing the miner
                cohort's mortality risks in each year from age 21 through age 80. Life
                tables were also constructed for unexposed (i.e., non-miner) groups
                assumed to die from a given disease at typical rates for the U.S. male
                population. MSHA used 2018 data for all males in the U.S. (published by
                the National Center for Health Statistics, 2020b) to estimate (a) the
                disease-specific mortality rates among unexposed males and (b) the all-
                cause mortality rates among both groups (exposed miners and unexposed
                non-miners).
                ---------------------------------------------------------------------------
                 \19\ Here, the ``background'' risk (or rate) refers to the risk
                of disease that the exposed person would have experienced in the
                absence of exposure to respirable crystalline silica. These
                background morbidity and mortality rates are measured using the
                disease-specific rates among the general population, which is not
                exposed to respirable crystalline silica.
                ---------------------------------------------------------------------------
                 For a given scenario (either Baseline or Proposed 50 [mu]g/m\3\),
                MSHA constructed life tables in the manner described above, both for a
                miner cohort exposed to respirable crystalline silica and for an
                unexposed non-miner cohort. MSHA calculated excess risk of the disease
                as the difference between the two cohorts' disease-specific mortality
                risk (due to silicosis, lung cancer, NMRD, or ESRD). MSHA determined
                the lifetime excess cases by multiplying the lifetime excess risk by
                the number of exposed miner FTEs (including both production employee
                FTEs and contract miner FTEs). Risks and cases were calculated
                separately for each exposure interval listed above. Then, the lifetime
                excess cases were aggregated across all exposure intervals. MSHA
                calculated the final lifetime excess risks per 1,000 miners in the full
                population by dividing the total number of lifetime excess cases by the
                total number of miners in the population (exposed at any interval).
                Finally, to estimate the risk reductions and avoided cases of illness
                due to the proposed PEL, MSHA compared the lifetime excess risks and
                lifetime excess cases across the two scenarios (Baseline and Proposed
                50 [mu]g/m\3\).
                B. Overview of Epidemiologic Studies
                 MSHA reviewed extensive research on the health effects of
                respirable crystalline silica and several quantitative risk assessments
                published in the peer-reviewed scientific literature
                [[Page 44881]]
                regarding occupational exposure risks of illness and death from
                silicosis, NMRD, lung cancer, and ESRD. The Health Effects document
                describes the specific studies reviewed by MSHA. Of the many studies
                evaluated, MSHA believes that the 13 studies used by OSHA (2013b) to
                estimate risks provide reliable estimates of the disease risk posed by
                miners' exposure to respirable crystalline silica. These studies are
                summarized in Table VI-1.
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                 Of these 13 studies, OSHA selected one per health endpoint for
                final modeling and estimation of lifetime excess risk and cases.
                Combining the five selected studies with the observed exposure data
                yields estimates of actual lifetime excess risks and lifetime excess
                cases among worker populations based on real exposure conditions. Table
                VI-2 presents the 13 studies from OSHA's PQRA, which MSHA has also
                considered. MSHA evaluated the evidence of OSHA's analysis of the 13
                studies and the accompanying risks associated with exposure at 25, 50,
                100, 250, and 500 [mu]g/m\3\. Thorough evaluation has led MSHA to
                determine that the studies OSHA selected still provide the best
                available epidemiological models. However, MSHA utilized the Miller and
                MacCalman (2010) study to estimate risks. This study was published
                after OSHA completed much of its modeling for their 2013 PRA (OSHA,
                2013b). The study was included in OSHA's health effects assessment and
                its PQRA. The following lists the study used by MSHA for each health
                endpoint:
                 Silicosis morbidity: Buchanan et al. (2003);
                 Silicosis mortality: Mannetje et al. (2002b);
                 NMRD mortality: Park et al. (2002);
                 Lung cancer mortality: Miller and MacCalman (2010); and
                 ESRD mortality: Steenland et al. (2002a).
                 MSHA developed its risk estimates based on recent mortality data
                and using certain assumptions that differed from those used by OSHA, as
                explained in the standalone PRA document. Examples of these MSHA
                assumptions include a lifetime that ends at age 80, updated background
                mortality data and all-cause mortality, miner population sizes, and
                miner-specific full-time equivalents (FTEs).\20\
                ---------------------------------------------------------------------------
                 \20\ FTEs were used to adjust the cumulative exposure over a
                year based on the average number of hours that miners work.
                ---------------------------------------------------------------------------
                 MSHA's modeling has been done using life tables, in a manner
                consistent with OSHA's PQRA. In general, the life table is a technique
                that allows estimation of excess risk of disease-specific mortality
                while factoring in the probability of surviving to a particular age
                assuming no exposure to respirable crystalline silica. This analysis
                accounts for competing causes of death, background mortality rates of
                the disease, and the effect of the accumulation of risk due to elevated
                mortality rates in each year of a working life. For each cause of
                mortality, the selected study was used in the life table analysis to
                compute the increase in miners' disease-specific mortality rates
                attributable to respirable crystalline silica exposure.
                 MSHA uses cumulative exposure (i.e., cumulative dose) to
                characterize the total exposure over a 45-year working life. Cumulative
                exposure is defined as the product of exposure duration and exposure
                intensity (i.e., exposure level). Cumulative exposure is the predictor
                variable in the selected exposure-response models.
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                 For each health endpoint, MSHA generated two sets of risk
                estimates--one representing a scenario of full compliance with the
                existing standards (herein referred to as the ``Baseline'' scenario)
                and another representing a scenario wherein no samples exceed the
                proposed PEL (herein referred to as the ``Proposed 50 [mu]g/m\3\''
                scenario). In the Baseline scenario, MNM miners in the >100-250, >250-
                500, and >500 [mu]g/m\3\ groups were assigned exposure intensities of
                100 [mu]g/m\3\ ISO. Coal miners in the 85.7-100, >100-250, >250-500,
                and >500 [mu]g/m\3\ groups were assigned exposure intensities of 85.7
                [mu]g/m\3\ ISO, calculated as an 8-hour TWA. Exposure intensities were
                not changed for miners with lower exposure concentrations, because
                their exposures were considered compliant with the existing standards.
                A similar procedure was used for the Proposed 50 [mu]g/m\3\ scenario,
                except that each miner group whose exposure exceeded the proposed PEL
                was assigned a new exposure of 50 [mu]g/m\3\ ISO (for both MNM and
                coal). This process--of creating an exposure profile based on actual
                exposure data and modifying it based on the existing standards or the
                proposed PEL--allowed MSHA to estimate real exposure conditions that
                miners would encounter under each scenario, thereby enabling estimates
                of the actual excess risks the current population of miners would
                experience under each scenario (Baseline and Proposed 50 [mu]g/m\3\).
                 For purposes of calculating risk in the PRA, both for MNM and coal
                miners, MSHA estimated excess risks by using the concentration
                collected over the full shift and calculating it as a full-shift, 8-
                hour TWA expressed in ISO standards. This metric of exposure
                intensity--the 8-hour TWA concentration of respirable crystalline
                silica in ISO standards--was used consistently across all sets of
                estimates (both MNM and coal sectors, and both the Baseline and
                Proposed 50 [mu]g/m\3\ scenarios), thereby facilitating meaningful
                comparison. MSHA acknowledges that this metric does not correspond to
                the manner in which coal exposure concentrations are calculated for
                purposes of evaluating compliance under the existing standard.
                Nonetheless, MSHA believes that a full-shift, 8-hour TWA concentration
                accurately represents risks to miners and thus is the most appropriate
                cumulative exposure metric for computing risk given that FTEs were used
                to scale exposure durations relative to the assumption of 250 8-hour
                workdays per year.
                C. Summary of Studies Selected for Modeling
                1. Silicosis Morbidity
                 Due to the long latency periods associated with chronic silicosis,
                OSHA's respirable crystalline silica standard relied on the subset of
                studies that were able to contact and evaluate many workers through
                retirement. MSHA agrees that relying on studies that included retired
                workers comes closest to characterizing lifetime risk of silicosis
                morbidity.
                 The health endpoint of interest in these studies was the appearance
                of opacities on chest radiographs indicative of pulmonary
                pneumoconiosis (a group of lung diseases caused by the lung's reaction
                to inhaled dusts). The most reliable estimates of silicosis morbidity,
                as detected by chest X-rays, come from the studies that evaluated those
                X-rays over time, included radiographic evaluation of workers after
                they left employment, and derived cumulative or lifetime estimates of
                silicosis disease risk.
                 To describe the presence and severity of pneumoconiosis, including
                silicosis, the International Labour Organization (ILO) developed a
                standardized system to classify lung opacities identified on chest
                radiographs (X-rays) (ILO, 1980, 2002, 2011, 2022). The ILO system
                [[Page 44886]]
                grades the size, shape, and profusion of opacities. Although silicosis
                is defined and categorized based on chest X-ray, the X-ray is an
                imprecise tool for detecting pulmonary pneumoconiosis (Craighead and
                Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and
                Velho, 2002). Hnizdo et al. (1993) recommended that an ILO category 0/1
                (or greater) should be considered indicative of silicosis among workers
                exposed to high respirable crystalline silica concentrations. They
                noted that the sensitivity of the chest X-ray as a screening test
                increases with disease severity and to maintain high specificity,
                category 1/0 (or 1/1) chest X-rays should be considered as a positive
                diagnosis of silicosis for miners who work in low dust occupations
                (Hnizdo et al., 1993). MSHA, consistent with NIOSH's use of chest X-
                rays in their occupational respiratory disease surveillance program
                (NIOSH 2014b), agrees that a small opacity profusion score of 1/0 is
                consistent with chronic silicosis stage 1. Most of the studies reviewed
                by MSHA considered a finding consistent with an ILO category of 1/1 or
                greater to be a positive diagnosis of silicosis, although some also
                considered an X-ray classification of 1/0 or 0/1 to be positive. The
                low sensitivity of chest radiography to detect minimal silicosis
                suggests that risk estimates derived from radiographic evidence likely
                underestimate the true risk of this disease (Craighead and Vallyathan,
                1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and Velho,
                2002).
                 OSHA summarized the Miller et al. (1995, 1998) and Buchanan et al.
                (2003) papers in their final respirable crystalline silica standard in
                2016 (OSHA 2016a, 81 FR 16286, 16316). These researchers reported on a
                1991 follow-up study of 547 survivors of a 1,416-member cohort of
                Scottish coal workers from a single mine. These men had all worked in
                the mine during the period between early 1971 and mid-1976, during
                which time they had experienced ``unusually high concentrations of
                freshly cut quartz in mixed coal mine dust.'' The population's
                exposures to quartz dust had been measured in unique detail for a
                considerable proportion of the men's working lives (OSHA 2013b, page
                333).
                 The 1,416 men had previous chest X-rays dating from before, during,
                or just after this high respirable crystalline silica exposure period.
                Of these 1,416 men, 384 were identified as having died by 1990/1991. Of
                the 1,032 remaining men, 156 were untraced, and, of the 876 who were
                traced and replied, 711 agreed to participate in the study. Of these,
                the total number of miners who were surveyed was 551. Four of these
                were omitted, two because of a lack of an available chest X-ray. The
                547 surviving miners (age range: 29-85 years, average = 59 years) were
                interviewed and received their follow-up chest X-rays between November
                1990 and April 1991. The interviews consisted of questions on current
                and past smoking habits and occupational history since leaving the coal
                mine, which closed in 1981. They were also asked about respiratory
                symptoms and were given a spirometry test (OSHA 2013b, pages 333-334).
                 Exposure characterization was based on extensive respirable dust
                sampling; samples were analyzed for quartz content by IR spectroscopy.
                Between 1969 and 1977, two coal seams were mined. One had produced
                quarterly average concentrations of respirable crystalline silica much
                less than 1,000 [mu]g/m\3\ (only 10 percent exceeded 300 [mu]g/m\3\).
                The other more unusual seam (mined between 1971 and 1976) lay in
                sandstone strata and generated respirable crystalline silica levels
                such that quarterly average exposures exceeded 1,000 [mu]g/m\3\ (10
                percent of the quarterly measurements were over 10,000 [mu]g/m\3\).
                Thus, this cohort study allowed evaluation of the effects of both
                higher and lower respirable crystalline silica concentrations and
                exposure-rate effects on the development of silicosis (OSHA 2013b, page
                334).
                 Three physicians read each chest film taken during the current
                survey as well as films from the surveys conducted in 1974 and 1978.
                Films from an earlier 1970 survey were read only if no films were
                available from the subsequent two surveys. Silicosis cases were
                identified if the median classification of the three readers indicated
                an ILO category of 1/1 or greater (Miller et al, 1995, page 24), plus a
                progression from the earlier reading. Of the 547 men, 203 (38 percent)
                showed progression of at least 1 ILO category from the 1970s' surveys
                to the 1990-91 survey; in 128 of these (24 percent) there was
                progression of 2 or more ILO categories. In the 1970s' surveys, 504 men
                had normal chest X-rays; of these 120 (24 percent) acquired an abnormal
                X-ray consistent with ILO category 1/0 or greater at the follow-up. Of
                the 36 men whose X-rays were consistent with ILO category 1/0 or
                greater in the 1970s' surveys, 27 (75 percent) exhibited further
                progression at the 1990/1991 follow-up. Only one subject showed a
                regression from any earlier reading, and that was slight, from 1/0 to
                0/1. The earlier Miller et al. (1995) report presented results for
                cases classified as having X-ray films consistent with either 1/0+ and
                2/1+ degree of profusion; the Miller et al. (1998) analysis and the
                Buchanan et al. (2003) re-analyses emphasized the results from cases
                having X-rays classified as 2/1+ (OSHA 2013b, page 334).
                 MSHA modeled the exposure-response relationship by using cumulative
                exposure expressed as gram/m\3\-hours, assuming 2,000 work hours per
                year and a 45-year working life (after adjusting for full-time
                equivalents, including production employees and contract workers). MSHA
                estimated risk at the existing standard assuming cumulative exposure to
                100 [micro]g/m\3\ ISO for MNM miners and 85.7 [micro]g/m\3\ ISO (100
                [micro]g/m\3\ MRE) for coal miners. Respirable crystalline silica
                exposures were calculated by commodity, and median exposure values were
                used within a variety of exposure intervals. Risks were computed using
                a life table methodology which iteratively updated the survival, risk,
                and mortality rates each year based on the results of the preceding
                year. Covariates in the regression included smoking, age, amount of
                coal dust, and percent of quartz in the coal dust during various
                previous survey periods.
                 Both Miller et al. papers (1995, 1998) presented the results of
                numerous regression models, and they compared the results of the
                partial regression coefficients using Z statistics of the coefficient
                divided by the standard error. Also presented were the residual
                deviances of the models and the residual degrees of freedom. In the
                introduction to the results section, Miller et al. (1995) stated that,
                ``in none of the models fitted was there a significant effect of
                smoking habit (current, ex-smoker, and never smoker), nor was there any
                evidence of any difference between smoking groups in their relationship
                of response with age.'' They therefore presented the results of the
                regression analyses without terms for smoking effects (i.e., without
                including smoking effects as a variable in the final regression
                analysis, because they found that smoking did not affect the modeling
                results). The logistic regression models developed by Miller et al.
                (1995) included terms for cumulative exposure and age. In their later
                publication, Miller et al. (1998) presented models similar to their
                1995 report, but without the age variable. Their logistic regression
                model A from Table 7 of their report (page 56) included only an
                intercept (-4.32) and the respirable crystalline silica (quartz)
                cumulative exposure variable (0.416). They estimated that respirable
                crystalline silica exposure at an average
                [[Page 44887]]
                concentration of 100 [micro]g/m\3\ for 15 years (2.6 gram/m\3\-hr
                assuming 1,750 hours worked per year) would result in an increased risk
                of silicosis (ILO > 2/1) of 5 percent (OSHA 2013b, page 334).
                 OSHA had a high degree of confidence in the estimates of silicosis
                morbidity risk from this Scotland coal mine study. This was mainly
                because of highly detailed and extensive exposure measurements,
                radiographic records, and detailed analyses of high exposure-rate
                effects. However, in another paper, Soutar et al. (2004) noted that:
                ``If the effects of silica vary according to the conditions of
                exposure, these risks are probably towards the high end of the risk
                spectrum, since the silica was freshly fractured from massive
                sandstone, and not derived from dirt bands where the quartz grains are
                aged and accompanied by clay minerals'' (OSHA 2013b, page 336). MSHA
                has reviewed and agrees with OSHA's conclusion.
                 Buchanan et al. (2003) provided an analysis and risk estimates only
                for cases having X-ray films consistent with ILO category 2/1+ extent
                of profusion of opacities, after adjusting for the disproportionately
                severe effect of exposure to high respirable crystalline silica
                concentrations. Estimating the risk of 1/0+ profusions from the
                Buchanan et al. (2003) or the earlier Miller et al. (1995, 1998)
                publications can only be roughly approximated because of the summary
                information included. Table 4 of Miller et al. (1998) (page 55)
                presents a cross-tabulation of radiograph progression, using the 12-
                point ILO scale, from the last baseline exam to the 1990/1991 follow-up
                visit for the 547 men at the Scottish coal mine. From this table, among
                miners having both early X-ray films and follow-up films, 44 men had
                progressed to 2/1+ by the last follow-up and an additional 105 men had
                experienced the onset of silicosis (i.e., X-ray films were classified
                as 1/0, 1/1, or 1/2). Thus, by the time of the follow-up, there were
                three times more miners with silicosis consistent with ILO category 1
                than there were miners with a category 2+ level of severity ((105 +
                44)/44 = 3.38). This suggests that the Buchanan et al. (2003) model,
                which reflects the risk of progressing to ILO category 2+,
                underestimates the risk of acquiring radiological silicosis by about
                three-fold in this population (OSHA 2013b, page 336). This type of
                analysis shows that the risk of developing silicosis estimated from the
                Buchanan et al. (2003) and Miller et al. (1998) studies is of the same
                magnitude as the risks reported by Hnizdo and Sluis-Cremer (1993b)
                (OSHA 2013b, page 338).
                 MSHA estimated silicosis risk by using the Buchanan et al. (2003)
                model that predicted the lifetime probability of developing silicosis
                at the 2/1+ category based on cumulative respirable crystalline silica
                exposures. As discussed previously, MSHA applied the Buchanan et al.
                (2003) model, assuming that miners are exposed for 45 years of working
                life extending from age 21 through age 65, using a life table approach.
                Buchanan et al. provides an exposure-response model using cumulative
                exposure in mg/m\3\-hours as the predictor variable and lifetime risk
                of silicosis as the outcome variable. MSHA assumed 45 years of
                exposure, each such year having a duration of 2,000 work hours, scaled
                by a weighted average FTE ratio that accounts for the average annual
                hours worked by production employees and contract miners.
                2. Accelerated Silicosis and Rapidly Progressive Pneumoconiosis (RPP)
                Study
                 OSHA concluded in their risk assessment, and MSHA agrees, that
                there is little evidence of a dose-rate effect at respirable
                crystalline silica concentrations in the exposure range of 25 [micro]g/
                m\3\ to 500 [micro]g/m\3\ (81 FR 16286, 16396). OSHA noted that the
                risk estimates derived from the Buchanan et al. (2003) study were not
                appreciably different from those derived from the other studies of
                silicosis morbidity (see OSHA 2016a, 81 FR 16286, 16386; Table VI-1.
                Summary of Lifetime or Cumulative Risk Estimates for Crystalline
                Silica). However, OSHA also concluded that some uncertainty related to
                dose-rate effects exists at concentrations far higher than the exposure
                range of interest. OSHA stated that it is possible for such a dose-rate
                effect to impact the results if not properly addressed in study
                populations with high concentration exposures. OSHA used the model from
                the Buchanan et al. (2003) study in its silicosis morbidity risk
                assessment to account for possible dose-rate effects at high average
                concentrations (OSHA 2016a, 81 FR 16286, 16396 OSHA 2013b, pages 335-
                342). MSHA has reviewed and agrees with OSHA's conclusions.
                 NIOSH stated in its post-hearing brief to OSHA, that a ``detailed
                examination of dose rate would require extensive and real time exposure
                history which does not exist for silica (or almost any other agent)''
                (81 FR 16285, 16375). Similarly, Dr. Kenneth Crump, a researcher from
                Louisiana Tech University Foundation who served on OSHA's peer review
                panel for the Review of Health Effects Literature and Preliminary
                Quantitative Risk Assessment, wrote to OSHA that, ``[h]aving noted that
                there is evidence for a dose rate effect for silicosis, it may be
                difficult to account for it quantitatively. The data are likely to be
                limited by uncertainty in exposures at earlier times, which were likely
                to be higher'' (OSHA 2016a, 81 FR 16286, 16375). OSHA agreed with the
                conclusions of NIOSH and Dr. Crump. OSHA believed that it used the best
                available evidence to estimate risks of silicosis morbidity and
                sufficiently accounted for any dose rate effect at high silica average
                concentrations by using the Buchanan et al. (2003) study as part of
                their final Quantitative Risk Analysis (QRA) (OSHA 2016a, 81 FR 16286,
                16396). MSHA has reviewed and agrees with OSHA's conclusions.
                 MSHA is using the Buchanan et al. (2003) study to explain, in part,
                the observed cases of progressive lung disease in miners, known as RPP
                in coal miners (Laney and Attfield, 2010; Wade et al., 2010; Laney et
                al., 2012b; 2017; Blackley et al., 2016b, 2018b; Reynolds et al.,
                2018b; Halldin et al., 2019; Halldin et al., 2020; Almberg et al.,
                2018a; Cohen et al., 2022) and accelerated silicosis in MNM miners
                (Dumavibhat et al., 2013; Hessel et al., 1988; Mohebbi and Zubeyri
                2007). The inclusion of this discussion in the risk analysis is to
                describe research that explains, in part, the progressive disease
                observed in shorter-tenured miners. MSHA believes that the risks
                estimated by the Buchanan et al. model can be applied to all mining
                populations that have similar respirable crystalline silica exposure
                exceedances. MSHA estimated the increase of silicosis risk in miners
                exposed to extreme respirable crystalline silica exposures for varying
                periods of time ranging from 0 hours to 348 hours per year (i.e., 0.0
                percent to 20.0 percent of time at extreme exposures). This information
                is important because MSHA data indicate that many miners' respirable
                crystalline silica exposure samples over the years have exceeded the
                existing exposure limit(s) of 100 [micro]g/m\3\. MSHA data also
                indicate that a smaller number of MSHA samples showed respirable
                crystalline silica concentrations well above the existing MSHA standard
                of 100 [micro]g/m\3\. Over the last 15 years of MNM compliance data,
                188 samples (0.3 percent) were over 500 [micro]g/m\3\; the upper range
                of exposure was 4,289 [micro]g/m\3\ ISO (see PRA Table 4 of the PRA
                document). Over the last 5 years of coal compliance data, eight samples
                (2 is the probability of profusion category 2/1 or
                higher (2/1+) at follow-up and E is the cumulative exposure.
                 In this model, both the cumulative exposure concentration variables
                were ``highly statistically significant in the presence of the other''
                (Buchanan et al., 2003, page 162). Since these variables were in the
                same units, mg/m\3\-hr, the authors noted that the coefficient for
                exposure concentrations >2,000 [mu]g/m\3\ (>2.0 mg/m\3\) was three
                times that for the concentrations 2,000 [mu]g/m\3\ (>2.0 mg/m\3\) quartz concentrations.
                OSHA chose to use this model to estimate the risk of radiological
                silicosis consistent with an ILO category 2/1+ chest X-ray for several
                exposure scenarios. They assumed 45 years of exposure, 2,000 hours/year
                of exposure, and no exposure above a concentration of 2,000 [mu]g/m\3\
                (2.0 mg/m\3\) (OSHA 2013b, page 336).
                 Buchanan et al. (2003) used these models to estimate the combined
                effect on the predicted risk of low quartz exposures (e.g., 100 [mu]g/
                m\3\, equal to 0.1 mg/m\3\) and short-term exposures to high quartz
                concentrations (e.g., 2,000 [mu]g/m\3\, equal to 2 mg/m\3\). Predicted
                risks were estimated for miners who progressed to silicosis level 2/1+
                15 years after exposure ended. This analysis showed the increase in
                predicted risk with relatively short periods of quartz exceedance
                exposures, over 4, 8, and 12 months. Buchanan et al. predicted a risk
                of 2.5 percent for 15 years quartz exposure to 100 [mu]g/m\3\ (0.1 mg/
                m\3\). This risk increased to 10.6 percent with the addition of only 4
                months of exposure at the higher concentration. The risk increased
                further to 72 percent with 12 months at the higher exposure of 2,000
                [mu]g/m\3\ (2.0 mg/m\3\).
                 The results indicate miners exposed to exceedances above MSHA's
                existing standard could develop progression of silicosis at an
                exaggerated rate. The results of Buchanan et al. also indicated that
                miners' exposure to exceedances at MSHA's proposed standard will also
                suffer increased risk of developing progressive disease, though at a
                reduced rate (see Buchanan et al. (2003), Table 4, page 163).
                 MSHA used a life table approach to estimate the lifetime excess
                silicosis morbidity from age 21 to age 80, assuming exposure from age
                21 through age 65 (45 years of working life) and an additional 15 years
                of potential illness progress thereafter. MSHA used the Buchanan et al.
                (2003) model to estimate the effect of respirable crystalline silica
                exposure exceedances as seen in MSHA's compliance data on miners'
                silicosis risk at the existing and proposed standard. The model
                predicted the probability of developing silicosis at the 2/1+ category
                based on cumulative respirable crystalline silica exposures. Age-
                specific cumulative risk was estimated as 1/(1 + EXP(-(-4.83 + 0.443 *
                cumulative exposure))). The model determined that even at 17.4 hours on
                average per year at an exposure of 1,500 [mu]g/m\3\ (1.50 mg/m\3\),
                miners' risk of developing 2/1+ silicosis increased from a baseline of
                24.8/1,000 to 29.0/1,000 at the existing standard and 14/1,000 to 16.6/
                1,000 at the proposed standard. Of course, the more hours exposed to
                these levels of respirable crystalline silica resulted in even higher
                increased risk. It is important to note that NIOSH's X-ray
                classification of the lowest case of pneumoconiosis is 1/0 profusion of
                small opacities (NIOSH 2008c, page A-2). Using a case definition of
                level 2/1+, the miners studied by Buchanan et al. (2003) would be more
                likely to show clinical signs of disease. MSHA emphasizes the
                importance of maintaining miner exposure to respirable crystalline
                silica at or below the proposed standard to minimize these health risks
                as much as possible.
                3. Silicosis and NMRD Mortality
                 Silicosis mortality was ascertained in the studies included in the
                pooled analysis by Mannetje et al. (2002b). These studies included
                cohorts of U.S. diatomaceous earth workers (Checkoway et al., 1997),
                Finnish granite workers (Koskela et al., 1994), U.S. granite workers
                (Costello and Graham, 1988), U.S. industrial sand workers (Steenland
                and Sanderson, 2001), U.S. gold miners (Steenland and Brown (1995a),
                and Australian gold miners (de Klerk et al., 1998). The researchers
                analyzed death certificates across all cohorts for cause of death. OSHA
                relied upon the published, peer-reviewed, pooled analysis of six
                epidemiological studies first published by Mannetje et al. (2002b) and
                a sensitivity analysis of the data conducted by ToxaChemica,
                International, Inc. (2004). OSHA used the model described by Mannetje
                et al.
                [[Page 44889]]
                (2002b) and the rate ratios that were estimated from the ToxaChemica,
                International Inc. sensitivity analysis to estimate the risks of
                silicosis mortality. This process better controlled for age and
                exposure measurement uncertainty (OSHA 2013b, page 295). MSHA has
                reviewed and agrees with OSHA's conclusions. These studies are
                summarized below, including detailed discussion and analysis of
                uncertainty in the studies and associated risk estimates.
                 OSHA found that the estimates from Mannetje et al. (2002b) and
                ToxaChemica Inc. probably understated the actual risk because silicosis
                is underreported as a cause of death since there is no nationwide
                system for collecting silicosis morbidity case data (OSHA 2016a, 81 FR
                16286, 16325). To help address this uncertainty, OSHA also included an
                exposure-response analysis of diatomaceous earth workers (Park et al.,
                2002). This analysis better recognized the totality of respirable
                crystalline silica-related respiratory disease than the datasets of
                Mannetje et al. (2002b) and ToxaChemica International Inc. (2004).
                Information from the Park et al. (2002) study (described in the next
                subsection) was used to quantify the relationship between cristobalite
                exposure and mortality caused by NMRD, which includes silicosis,
                pneumoconiosis, emphysema, and chronic bronchitis. The category of NMRD
                captures much of the silicosis misclassification that results in
                underestimation of the disease. NMRD also includes risks from other
                lung diseases associated with respirable crystalline silica exposures.
                OSHA found the risk estimates derived from Park et al. (2002) were
                important to include in their range of estimates of the risk of death
                from respirable crystalline silica-related respiratory diseases,
                including silicosis (OSHA 2013b, pages 297-298). OSHA concluded that
                the ToxaChemica International Inc. (2004) re-analysis of Mannetje et
                al.'s (2002b) silicosis mortality data and Park et al.'s (2002) study
                of NMRD mortality provided a credible range of estimates of mortality
                risk from silicosis and NMRD across many workplaces. The upper end of
                this range, based on the Park et al. (2002) study, is less likely to
                underestimate risk because of underreporting of silicosis mortality.
                However, risk estimates from studies focusing on cohorts of workers
                from different industries cannot be directly compared (OSHA 2016a, 81
                FR 16286, 16397).
                a. Silicosis Mortality: Mannetje et al. (2002b); ToxaChemica,
                International, Inc. (2004)
                 Mannetje et al. (2002b) relied upon the epidemiological studies
                contained within the Steenland et al. (2001a) pooled analysis of lung
                cancer mortality that also included extensive data on silicosis. The
                six cohorts included:
                 (1) U.S. diatomaceous earth workers (Checkoway et al., 1997),
                 (2) Finnish granite workers (Koskela et al., 1994),
                 (3) U.S. granite workers (Costello and Graham, 1988),
                 (4) U.S. industrial sand workers (Steenland and Sanderson, 2001),
                 (5) U.S. gold miners (Steenland and Brown, 1995b), and
                 (6) Australian gold miners (de Klerk and Musk, 1998).
                 These six cohorts contained 18,364 workers and 170 silicosis
                deaths, where silicosis mortality was defined as death from silicosis
                (ICD-9 502, n = 150) or from unspecified pneumoconiosis (ICD-9 505, n =
                20). Table VI-3 provides information on each cohort, including size,
                time period studied, overall number of deaths, and number of deaths
                identified as silicosis for the pooled analysis conducted by Mannetje
                et al. (2002b). The authors believed this definition to err on the side
                of caution in that some cases of death from silicosis in the cohorts
                may have been misclassified as other causes (e.g., tuberculosis or COPD
                without mention of pneumoconiosis). Four cohorts were not included in
                the silicosis mortality study. The three Chinese studies did not use
                the ICD to code cause of death. In the South African gold miner study,
                silicosis was not generally recognized as an underlying cause of death.
                Thus, it did not appear on death certificates (OSHA 2013b, page 292).
                [GRAPHIC] [TIFF OMITTED] TP13JY23.018
                [[Page 44890]]
                 Mannetje et al. (2002a) described the exposure assessments
                developed for the pooled analysis. Exposure information from each of
                the 10 cohort studies varied and included dust measurements
                representing particle counts, mass of total dust, and respirable dust
                mass. Measurement methods also changed over time for each of the cohort
                studies. Generally, sampling was performed using impingers in earlier
                decades, and gravimetric techniques later. Exposure data based on
                analysis for respirable crystalline silica by XRD (the current method
                of choice) were available only from the study of U.S. industrial sand
                workers. To develop cumulative exposure estimates for all cohort
                members and to pool the cohort data, all exposure data were converted
                to units of [mu]g/m\3\ (mg/m\3\) respirable crystalline silica. Cohort-
                specific conversion factors were generated based on the silica content
                of the dust to which workers were exposed. In some instances, results
                of side-by-side comparison sampling were available. Within each cohort,
                available job- or process-specific information on the silica
                composition or nature of the dust was used to reconstruct respirable
                crystalline silica exposures. Most of the studies did not have exposure
                measurements prior to the 1950s. Exposures occurring prior to that time
                were estimated either by assuming such exposures were the same as the
                earliest recorded for the cohort or by modeling that accounted for
                documented changes in dust control measures.
                 To evaluate the reasonableness of the exposure assessment for the
                lung cancer pooled study, Mannetje et al. (2002a) investigated the
                relationship between silicosis mortality and cumulative exposure. They
                performed a nested case-control analysis for silicosis or unspecified
                pneumoconiosis using conditional logistic regression. Since exposure to
                respirable crystalline silica is the sole cause of silicosis, any
                finding for which cumulative exposure was unrelated to silicosis
                mortality risk would suggest that serious misclassification of the
                exposures assigned to cohort members occurred. Cases and controls were
                matched for race, sex, age (within 5 years), and 100 controls were
                matched to each case. Each cohort was stratified into quartiles by
                cumulative exposure. Standardized rate ratios (SRRs) were calculated
                using the lowest-exposure quartile as the baseline. Odds ratios (ORs)
                were also calculated for the pooled data set overall, which was
                stratified into quintiles based on cumulative exposure. For the pooled
                data set, the relationship between the ORs for silicosis mortality and
                cumulative exposure, along with each of the 95 percent confidence
                intervals (95% CI), were as follows:
                 (1) 4,450 [mu]g/m\3\-years (4.45 mg/m\3\-years), OR=3.1 (95% CI:
                2.5-4.0);
                 (2) 9,080 [mu]g/m\3\-years (9.08 mg/m\3\-years), OR=4.6 (95% CI:
                3.6-5.9);
                 (3) 16,260 [mu]g/m\3\-years (16.26 mg/m\3\-years), OR=4.5 (95% CI:
                3.5-5.8); and
                 (4) 42,330 [mu]g/m\3\-years (42.33 mg/m\3\-years), OR=4.8 (95% CI:
                3.7-6.2).
                 In addition, in seven of the cohorts, there was a statistically
                significant trend between silicosis mortality and cumulative exposure.
                For two of the cohorts (U.S. granite workers and U.S. gold miners), the
                trend test was not statistically significant (p=0.10). An analysis
                could not be performed on the South African gold miner cohort because
                silicosis was never coded as an underlying cause of death, apparently
                due to coding practices in that country.
                 Based on this analysis, Mannetje et al. (2002a) concluded that the
                exposure-response relationship for the pooled data set was ``positive
                and reasonably monotonic.'' That is, the response increased with
                increasing exposure. The results also indicated that the exposure
                assessments provided reasonable estimates of cumulative exposures. In
                addition, despite some large differences in the range of cumulative
                exposures between cohorts, a clear positive exposure-response trend was
                evident in seven of the cohorts (OSHA 2013b, page 271).
                 Furthermore, in their pooled analysis of silicosis mortality for
                six of the cohorts, Mannetje et al. (2002b) found a clear and
                consistently positive response with increasing decile of cumulative
                exposure, although there was an anomaly in the 9th decile. Overall,
                these data supported a monotonic exposure-response relationship for
                silicosis. Thus, although some exposure misclassification almost
                certainly existed in the pooled data set, the authors concluded that
                exposure estimates did not appear to have been sufficiently
                misclassified to obscure an exposure-response relationship (OSHA 2013b,
                page 271).
                 As part of an uncertainty analysis conducted for OSHA, Drs.
                Steenland and Bartell (ToxaChemica International, Inc. 2004) examined
                the quality of the original data set and analysis to identify and
                correct any data entry, programming, or reporting errors (ToxaChemica
                International, Inc. 2004). This quality assurance process revealed a
                small number of errors in exposure calculations for the originally
                reported results. Primarily, these errors resulted from rounding of job
                class exposures when converting the original data file for use with a
                different statistical program. Although the corrections affected some
                of the exposure-response models for individual cohorts, ToxaChemica
                International, Inc. (2004) reported that models based on the pooled
                dataset were not impacted by the correction of these errors (OSHA
                2013b, pages 271-272).
                 Silicosis mortality was evaluated using standard life table
                analysis in Mannetje et al. (2002b). Poisson regression, using 10
                categories of cumulative exposure and adjusting for age, calendar time,
                and cohort, was conducted to derive silicosis mortality rate ratios
                using the lowest exposure group of 0-100 [mu]g/m\3\-years (0-0.1 mg/
                m\3\-year) as the referent group. More detailed exploration of the
                exposure-response relationship using a variety of exposure metrics,
                including cumulative exposure, duration of exposure, average exposure
                (calculated as cumulative exposure/duration), and the log
                transformations of these variables, was conducted via nested case-
                control analyses (conditional logistic regression). Each case was
                matched to 100 controls selected from among those who had survived to
                at least the age of the case, with additional matching on cohort, race,
                sex, and date of birth within 5 years. The authors explored lags of 0,
                5, 10, 15, and 20 years, noting that there is no a priori reason to
                apply an exposure lag, as silicosis can develop within a short period
                after exposure. However, a lag could potentially improve the model, as
                there is often a considerable delay in the development of silicosis
                following exposure. In addition to the parametric conditional logistic
                regression models, the authors performed some analyses using a cubic-
                spline model, with knots at 5, 25, 50, 75, and 95 percent of the
                distribution of exposure. Models with cohort-exposure interaction terms
                were fit to assess heterogeneity between cohorts (OSHA 2013b, page
                294).
                 The categorical analysis found a nearly monotonic increase in
                silicosis rates with cumulative exposure, from 4.7 per 100,000 person-
                years in the lowest exposure category (0-990 [mu]g/m\3\-years [0-0.99
                mg/m\3\-years]) to 299 per 100,000 person-years in the highest exposure
                category (>28,000 [mu]g/m\3\-years [>28 mg/m\3\-years]). Nested case-
                control analyses showed a significant association between silicosis
                mortality and cumulative exposure, average exposure, and duration of
                exposure. The best-fitting conditional logistic regression model used
                log-transformed cumulative exposure with no exposure lag, with a model
                [chi]\2\ of 73.2 versus [chi]\2\
                [[Page 44891]]
                values ranging from 19.9 to 30.9 for average exposure, duration of
                exposure, and untransformed cumulative exposure (1 degree of freedom).
                No significant heterogeneity was found between individual cohorts for
                the model based on log-cumulative exposure. The cubic-spline model did
                not improve the model fit for the parametric logistic regression model
                using the log-cumulative exposure (OSHA 2013b, page 294).
                 Mannetje et al. (2002b) developed estimates of silicosis mortality
                risk through age 65 for two levels of exposure (50 and 100 [mu]g/m\3\
                respirable crystalline silica), assuming a working life of occupational
                exposure from age 20 to 65. Risk estimates were calculated based on the
                silicosis mortality rate ratios derived from the categorical analysis
                described above. The period of time over which workers' exposures and
                risks were calculated (age 20 to 65) was divided into one-year
                intervals. The mortality rate used to calculate risk in any given
                interval was dependent on the worker's cumulative exposure at that
                time. The equation used to calculate risk is as follows:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.019
                Where timei is equal to one for every age i, and ratei is the age-,
                calendar time-, and cohort adjusted silicosis mortality rate associated
                with the level of cumulative exposure acquired at age i, as presented
                in Mannetje et al. (2002b, Table 2, page 725). The calculated absolute
                risks equal the excess risks since there is no background rate of
                silicosis in the exposed population. Mannetje et al. (2002b) estimated
                the lifetime risk of death from silicosis, assuming 45 years of
                exposure to 100 [mu]g/m\3\, to be 13 deaths per 1,000 workers; at an
                exposure of 50 [mu]g/m\3\, the estimated lifetime risk was 6 per 1,000.
                Confidence intervals (CIs) were not reported (OSHA 2013b, page 295).
                 In summary, OSHA's estimates of silicosis morbidity risks were
                based on studies of active and retired workers for which exposure
                histories could be constructed and chest X-ray films could be evaluated
                for signs of silicosis. There is evidence in the record that chest X-
                ray films are relatively insensitive to detecting lung fibrosis (OSHA
                2016a, 81 FR 16286, 16397). MSHA agrees with OSHA's estimate of
                silicosis morbidity risks.
                 Hnizdo et al. (1993a) found chest X-ray films to have low
                sensitivity for detecting lung fibrosis related to initial cases of
                silicosis, compared to pathological examination at autopsy. To address
                the low sensitivity of chest X-rays for detecting silicosis, Hnizdo et
                al. (1993a) recommended that radiographs consistent with an ILO
                category of 0/1 or greater be considered indicative of silicosis among
                workers exposed to a high concentration of respirable crystalline
                silica-containing dust. In like manner, to maintain high specificity,
                chest X-rays classified as category 1/0 or 1/1 should be considered as
                a positive diagnosis of silicosis in miners who work in low dust (0.2
                mg/m\3\) occupations. The studies on which OSHA relied in its risk
                assessment typically used an ILO category of 1/0 or greater to identify
                cases of silicosis. According to Hnizdo et al. (1993), they were
                unlikely to have included many false positives (i.e., assumed diagnosis
                of silicosis in a miner without the disease), but may have included
                false negatives (i.e., failure to identify cases of silicosis). Thus,
                in OSHA's risk assessment, the use of chest X-rays to ascertain
                silicosis cases in the morbidity studies may have underestimated risk
                given the X-rays' low sensitivity to detect disease. MSHA agrees with
                OSHA's assessment.
                 To estimate the risk of silicosis mortality at the existing and
                proposed exposure limits, OSHA used the categorical model described by
                Mannetje et al. (2002b) but did not rely upon the Poisson regression in
                their study. Instead, OSHA used rate ratios estimated from a nested
                case-control design implemented as part of a sensitivity analysis
                (ToxaChemica, International, Inc. 2004). The case-control design was
                selected because it was expected to better control for age. In
                addition, the rate ratios derived from the case control study were
                derived from a Monte Carlo analysis to reflect exposure measurement
                uncertainty (See ToxaChemica, International, Inc. (2004), Table 7, page
                40). The rate ratio for each interval of cumulative exposure was
                multiplied by the annual silicosis rate assumed to be associated with
                the lowest exposure interval, 4.7 per 100,000 for exposures of 990
                [mu]g/m\3\-years (0.99 mg/m\3\-years), to estimate the silicosis rate
                for each interval of exposure. The lifetime silicosis mortality risk is
                the sum of the silicosis rate for each year of life through age 85 and
                assuming exposure from age 20 to 65. From this analysis, OSHA estimated
                the silicosis mortality risk for exposure to the then existing general
                industry exposure limit (100 [mu]g/m\3\) and proposed exposure limit
                (50 [mu]g/m\3\) to be 11 (95% CI 5-37) and 7 (95% CI 3-21) deaths per
                1,000 workers, respectively. For exposure to 250[mu]g/m\3\ (0.25 mg/
                m\3\) and 500 [mu]g/m\3\ (0.5 mg/m\3\), the range approximating the
                then existing construction/shipyard exposure limit, OSHA estimated the
                risk to range from 17 (95% CI 5-66) to 22 (95% CI 6-85) deaths per
                1,000 workers (OSHA 2013b, page 294-295).
                 In view of the foregoing discussion, MSHA agrees with OSHA's
                analysis, and MSHA also selected the Mannetje et al. (2002b) study for
                estimating silicosis mortality risks and cases. MSHA used a life table
                analysis to estimate the lifetime excess silicosis mortality through
                age 80. To estimate the age-specific risk of silicosis mortality at the
                existing standards, the proposed PEL, and the proposed action level,
                MSHA used the same categorical model that OSHA used in their PQRA (as
                described above from Mannetje et al., 2002b; ToxaChemica International,
                Inc. 2004) to estimate lifetime risk following cumulative exposure of
                45 years. MSHA used the 2018 all-cause mortality rates (NCHS,
                Underlying Cause of Death, 2018 on CDC WONDER Online Database, released
                in 2020b) as all-cause mortality rates. As stated previously, the
                general (unexposed) population is assumed to have silicosis mortality
                rates equal to zero.
                b. NMRD Mortality: Park et al. (2002)
                 In addition to causing silicosis, exposure to respirable
                crystalline silica causes increased risks of other NMRD. These include
                chronic obstructive pulmonary disease (COPD), which includes chronic
                bronchitis, emphysema, and combinations of the two and is a cause of
                chronic airways obstruction. COPD is characterized by airflow
                limitation that is usually progressive and not fully reversible. OSHA
                reviewed several studies of NMRD morbidity and used a study by Park et
                al. (2002) to assess NMRD risk. Checkoway et al. (1997) originally
                studied a California diatomaceous earth
                [[Page 44892]]
                cohort for which Park et al. (2002) then analyzed the effect of
                respirable crystalline silica exposures on the development of NMRD. The
                authors quantified the relationship between exposure to cristobalite
                and mortality from NMRD (OSHA 2013b, page 295).
                 The California diatomaceous earth cohort consisted of 2,570
                diatomaceous earth workers employed for 12 months or more from 1942 to
                1994. As noted above, Park et al. (2002) was interested in the
                relationship between cristobalite exposure and mortality from chronic
                lung disease other than cancer (LDOC). LDOC included chronic diseases
                such as pneumoconiosis (which included silicosis), chronic bronchitis,
                and emphysema, but excluded pneumonia and other infectious diseases.
                The investigators selected LDOC as the health endpoint for three
                reasons. First, increased mortality from LDOC had been documented among
                respirable crystalline silica-exposed workers in several industry
                sectors, including gold mining, pottery, granite, and foundry
                industries. Second, the authors pointed to the likelihood that
                silicosis as a cause of death is often misclassified as emphysema or
                chronic bronchitis. Third, the number of deaths from the diatomaceous
                earth worker cohort that were attributed to silicosis was too small
                (10) for analysis. Industrial hygiene data for the cohort were
                available from the employer for total dust, respirable crystalline
                silica (mostly cristobalite), and asbestos. Smoking information was
                available for about 50 percent of the cohort and for 22 of the 67 LDOC
                deaths available for analysis, permitting Park et al. (2002) to
                partially adjust for smoking (OSHA 2013b, pages 295-296).
                 Park et al. (2002) used the exposure assessment previously reported
                by Seixas et al. (1997) and used by Rice et al. (2001) to estimate
                cumulative respirable crystalline silica exposures for each worker in
                the cohort based on detailed work history files. The average respirable
                crystalline silica concentration for the cohort was 290 [micro]g/m\3\
                (0.29 mg/m\3\) over the period of employment (Seixas et al., 1997). The
                total respirable dust concentration in the diatomaceous earth plant was
                3,550 [micro]g/m\3\ (3.55 mg/m\3\) before 1949 and declined by more
                than 10-fold after 1973, to 290 [micro]g/m\3\ (0.29 mg/m\3\) (Seixas et
                al., 1997). The concentration of respirable crystalline silica in the
                dust ranged from one to 25 percent and was dependent on the location
                within the worksite. It was lowest at the mine and greatest in the
                plant where the raw ore was calcined into final product. The average
                cumulative exposure values for total respirable dust and respirable
                crystalline silica were 7,310 [micro]g/m\3\-year (7.31 mg/m\3\-year)
                and 2,160 [micro]g/m\3\-year (2.16 mg/m\3\-year), respectively. The
                authors also estimated cumulative exposure to asbestos (OSHA 2013b,
                page 296).
                 Using Poisson regression models and Cox's proportional hazards
                models, the authors fit the same series of relative rate exposure-
                response models that were evaluated by Rice et al. (2001) for lung
                cancer (i.e., log-linear, log-square root, log-quadratic, linear
                relative rate, a power function, and a shape function). In general
                form, the relative rate model was:
                Rate = exp(a0) x f(E),
                where exp(a0) is the background rate and E is the cumulative
                respirable crystalline silica exposure. Park et al. (2002) also
                employed an additive excess rate model of the form:
                Rate = exp(a0) + exp(aE).
                 Relative or excess rates were modeled using internal controls and
                adjusting for age, calendar time, ethnicity, and time since first entry
                into the cohort. In addition, relative rate models were evaluated using
                age- and calendar time-adjusted external standardization to U.S.
                population mortality rates for 1940 to 1994 (OSHA 2013b, page 296).
                 There were no LDOC deaths recorded among workers having cumulative
                exposures above 32,000 [micro]g/m\3\-years (32 mg/m\3\-years), causing
                the response to level off or decline in the highest exposure range. The
                authors believed the most likely explanation for this observation
                (which was also observed in their analysis of silicosis morbidity in
                this cohort) was some form of survivor selection, possibly smokers or
                others with compromised respiratory function leaving work involving
                extremely high dust concentrations. These authors suggested several
                alternative explanations. First, there may have been a greater
                depletion of susceptible populations in high dust areas. Second, there
                may have been greater misclassification of exposures in the earlier
                years where exposure data were lacking (and when exposures were
                presumably the highest) (OSHA 2013b, pages 296-297).
                 Therefore, Park et al. (2002) performed exposure-response analyses
                that restricted the dataset to observations where cumulative exposures
                were below 10,000 [micro]g/m\3\-years (10 mg/m\3\-years). This is a
                level more than four times higher than that resulting from 45 years of
                exposure to the former OSHA PEL for cristobalite (which was 50
                [micro]g/m\3\ (0.05 mg/m\3\) when cristobalite was the only polymorph
                present). These investigators also conducted analyses using the full
                dataset (OSHA 2013b, page 297).
                 Model fit was assessed by evaluating the decrease in deviance
                resulting from addition of the exposure term, and cubic-spline models
                were used to test for smooth departures from each of the model forms
                described. Park et al. (2002) found that both lagged and unlagged
                models fit well, but unlagged models provided a better fit. In
                addition, they believed that unlagged models were biologically
                plausible in that recent exposure could contribute to LDOC mortality.
                The Cox proportional hazards models yielded results that were similar
                to those from the Poisson analysis. Consequently, only the results from
                the Poisson analysis were reported. In general, the use of external
                adjustments for age and calendar time yielded considerably improved fit
                over models using internal adjustments. The additive excess rate model
                also proved to be clearly inferior compared to the relative rate
                models. With one exception, the use of cumulative exposure as the
                exposure metric consistently provided better fits to the data than did
                intensity of exposure (i.e., cumulative exposure divided by duration of
                exposure). As to the exception, when the highest-exposure cohort
                members were included in the analysis, the log-linear model produced a
                significantly improved fit with exposure intensity as the exposure
                metric, but a poor fit with cumulative exposure as the metric (OSHA
                2013b, page 297).
                 Among the models based on the restricted dataset (excluding
                observations with cumulative exposures greater than 10,000 [micro]g/
                m\3\-years (10 mg/m\3\-years)), the best-fitting model with a single
                exposure term was the linear relative rate model using external
                adjustment. Most of the other single-term models using external
                adjustment fit almost as well. Of the models with more than one
                exposure term, the shape model provided no improvement in fit compared
                with the linear relative rate model. The log-quadratic model fit
                slightly better than the linear relative rate model, but Park et al.
                (2002) did not consider the gain in fit sufficient to justify an
                additional exposure term in the model (OSHA 2013b, page 297).
                 Based on its superior fit to the cohort data, Park et al. (2002)
                selected the linear relative rate model with external adjustment and
                use of cumulative exposure as the basis for estimating LDOC mortality
                risks among exposed workers. Competing mortality was accounted for
                using U.S. death rates published by the National Center for
                [[Page 44893]]
                Health Statistics (1996). The authors estimated the lifetime excess
                risk for white men exposed to respirable crystalline silica (mainly
                cristobalite) for 45 years at 50 [micro]g/m\3\ (0.05 mg/m\3\) to be 54
                deaths per 1,000 workers (95% CI: 17-150) using the restricted dataset,
                and 50 deaths per 1,000 using the full dataset. For exposure to 100
                [micro]g/m\3\ (0.1 mg/m\3\), they estimated 100 deaths per 1,000 using
                the restricted dataset, and 86 deaths per 1,000 using the full dataset.
                The CIs were not reported (OSHA 2013b, page 297).
                 The estimates of Park et al. (2002) were about eight to nine times
                higher than those that were calculated for the pooled analysis of
                silicosis mortality (Mannetje et al., 2002b). Also, these estimates are
                not directly comparable to those from Mannetje et al. (2002b) because
                the mortality endpoint for the Park et al. (2002) analysis was death
                from all non-cancer lung diseases beyond silicosis (including
                pneumoconiosis, emphysema, and chronic bronchitis). In the pooled
                analysis by Mannetje et al. (2002b), only deaths coded as silicosis or
                other pneumoconiosis were included (OSHA 2013b, pages 297-298).
                 Less than 25 percent of the LDOC deaths in the Park et al. (2002)
                analysis were coded as silicosis or other pneumoconiosis (15 of 67). As
                noted by Park et al. (2002), it is likely that silicosis as a cause of
                death is often misclassified as emphysema or chronic bronchitis
                (although COPD is part of the spectrum of disease caused by respirable
                crystalline silica exposure and can occur in the absence of silicosis).
                Thus, the selection of deaths by Mannetje et al. (2002b) may have
                underestimated the true risk of silicosis mortality. The analysis by
                Park et al. (2002) would have more fairly captured the total
                respiratory mortality risk from all non-malignant causes, including
                silicosis and chronic obstructive pulmonary disease. Furthermore, Park
                et al. (2002) used untransformed cumulative exposure in a linear model
                compared to the log-transformed cumulative exposure metric used by
                Mannetje et al. (2002b). This would have caused the exposure-response
                relationship to flatten in the higher exposure ranges (OSHA 2013b, page
                298).
                 It is also possible that some of the difference between Mannetje et
                al.'s (2002b) and Park et al.'s (2002) risk estimates reflected factors
                specific to the nature of exposure among diatomaceous earth workers
                (e.g., exposure to cristobalite vs. quartz). However, neither the
                cancer risk assessments nor assessments of silicosis morbidity
                supported the hypothesis that cristobalite is more hazardous than
                quartz (OSHA 2013b, page 298).
                 Based on the available risk assessments for silicosis mortality,
                OSHA believed that the estimates from the pooled study by Mannetje et
                al.'s (2002b) represented those least likely to overestimate mortality
                risk. It was unlikely to have overstated silicosis mortality risks
                given that the estimates reflected only those deaths where silicosis
                was specifically identified on death certificates. Therefore, there was
                most likely an underestimate of the true silicosis mortality risk. In
                contrast, the risk estimates provided by Park et al. (2002) for the
                diatomaceous earth cohort would have captured some of this
                misclassification and included risks from other lung diseases (e.g.,
                emphysema, chronic bronchitis) that have been associated with
                respirable crystalline silica exposure. Therefore, OSHA believed that
                the Park et al. (2002) study provided a better basis for estimating the
                respirable crystalline silica-related risk of NMRD mortality, including
                that from silicosis. Based on Park et al.'s (2002) linear relative rate
                model [RR = 1 + [beta]x, where [beta] = 0.5469 (no standard error
                reported) and x = cumulative exposure], OSHA used a life table analysis
                to estimate the lifetime excess NMRD mortality through age 85. For this
                analysis, OSHA used all-cause and cause-specific background mortality
                rates for all males (National Center for Health Statistics, 2009).
                Background rates for NMRD mortality were based on rates for ICD-10
                codes J40-J47 (chronic lower respiratory disease) and J60-J66
                (pneumoconiosis). OSHA believed that these corresponded closely to the
                ICD-9 disease classes (ICD 490-519) used by the original investigators.
                According to CDC (2001), background rates for chronic lower respiratory
                diseases were increased by less than five percent because of the
                reclassification to ICD-10. From the life table analysis, OSHA
                estimated that the excess NMRD risk due to respirable crystalline
                silica exposure at the former general industry PEL (100 [micro]g/m\3\)
                and at OSHA's final PEL (50 [micro]g/m\3\) for 45 years are 83 and 43
                deaths per 1,000, respectively. For exposure at the former
                construction/shipyard exposure limit, OSHA estimated that the excess
                NMRD risk ranged from 188 to 321 deaths per 1,000 (OSHA 2013b, page
                298).
                 Following its own independent review, MSHA agrees with and has
                followed the rationale presented by OSHA in its selection of the Park
                et al. (2002) model to estimate NMRD mortality risk in miners. Coal
                miners were not included in the NMRD mortality analysis because the
                endpoint was included in the Quantitative Risk Assessment in Support of
                the Final Respirable Coal Mine Dust Rule (Dec. 2013).
                 MSHA used a life table analysis to estimate the lifetime excess
                NMRD mortality through age 80. MSHA used the Park et al. (2002) model
                to estimate age-specific NMRD mortality risk as 1 + 0.5469 * cumulative
                exposure. MSHA used all-cause and cause-specific background mortality
                rates for all males for 2018 (National Center for Health Statistics,
                Underlying Cause of Death 2018 on CDC WONDER Online Database, released
                in 2020b). Background rates for NMRD mortality were based on rates for
                ICD-10 codes J40-J47 (chronic lower respiratory disease) and J60-J66
                (pneumoconiosis).
                4. Lung Cancer Mortality
                 Since the publication of OSHA's final rule in 2016, NIOSH has
                published two documents concerning occupational carcinogens, Chemical
                Carcinogen Policy (2017b) and Practices in Occupational Risk Assessment
                (2019a). NIOSH will no longer set recommended exposure levels for
                occupational carcinogens. Instead, NIOSH intends to develop risk
                management limits for carcinogens (RML-Cas) to acknowledge that, for
                most carcinogens, there is no known safe level of exposure. An RML-CA
                is a reasonable starting place for controlling exposures. An RML-CA
                limit is based on a daily maximum 8-hour TWA concentration of a
                carcinogen above which a worker should not be exposed (NIOSH 2017b,
                page vi). RML-Cas for occupational carcinogens are established at the
                estimated 95% lower confidence limit on the concentration (e.g., dose)
                corresponding to 1 in 10,000 (10-4) lifetime excess risk
                (when analytically possible to measure) (NIOSH 2019a). NIOSH stated
                that in order to incrementally move toward a level of exposure to
                occupational chemical carcinogens that is closer to background, NIOSH
                will begin issuing recommendations for RML-Cas that would advise
                employers to take additional action to control chemical carcinogens
                when workplace exposures result in excess risks greater than
                10-4 (NIOSH 2017b, page vi).
                 MSHA used the Miller et al. (2007) and Miller and MacCalman (2010)
                studies to estimate lung cancer mortality risk in miners. In British
                coal miners, excess lung cancer mortality was studied through the end
                of 2005 in a cohort of 17,800 miners (Miller et al., 2007; Miller and
                MacCalman, 2010). By that time, the cohort had accumulated
                [[Page 44894]]
                516,431 person-years of observation (an average of 29 years per miner),
                with 10,698 deaths from all causes. Overall lung cancer mortality was
                elevated (Standard Mortality Ratio (SMR) = 115.7, 95% CI: 104.8-127.7),
                and a positive exposure-response relationship with respirable
                crystalline silica exposure was determined from Cox regression after
                adjusting for smoking history. Three strengths of this study were: 1)
                the detailed time-exposure measurements of quartz and total mine dust,
                2) detailed individual work histories, and 3) individual smoking
                histories. For lung cancer, analyses based on Cox regression provided
                strong evidence that, for these coal miners, although quartz exposures
                were associated with increased lung cancer risk, simultaneous exposures
                to coal dust did not cause increased lung cancer risk (OSHA 2016a, 81
                FR 16286, 16308).
                 Miller et al. (2007) and Miller and MacCalman (2010) conducted a
                follow-up study of cohort mortality, begun in 1970. Their previous
                report on mortality presented a follow-up analysis on 18,166 coal
                miners from 10 British coal mines followed through the end of 1992
                (Miller et al., 1997). The two reports from 2007 and 2010 analyzed the
                mortality experience of 17,800 of these miners (18,166 minus 346 men
                whose vital status could not be determined) and extended the analysis
                through the end of 2005. Causes of deaths that were of particular
                interest included pneumoconiosis, other NMRD, lung cancer, stomach
                cancer, and tuberculosis. The researchers noted that no additional
                exposure measurements were included in the updated analysis, since all
                the mines had closed by the mid-1980s. However, some of these men might
                have had additional exposure at other mines or facilities not reported
                in this study (OSHA 2013b, page 287).
                 This cohort mortality study included analyses using both external
                and internal controls. The external controls used British
                administrative regional age-, time-, and cause-specific mortality rates
                from which to calculate SMRs. The internal controls from the mines used
                Cox proportional hazards regression methods, which considered each
                miner's age, smoking status, and detailed dust and respirable
                crystalline silica (quartz) time-dependent exposure measurements. Cox
                regression analyses were done in stages, with the initial analyses used
                to establish what factors were required for baseline adjustment (OSHA
                2013b, page 287).
                 For the analysis using external mortality rates, the all-cause
                mortality SMR from 1959 through 2005 was 100.9 (95% CI: 99.0-102.8),
                based on all 10,698 deaths. However, these SMRs were not uniform over
                time. For the period from 1990-2005, the SMR was 109.6 (95% CI:106.5-
                112.8), while the ratios for previous periods were less than 100. This
                pattern of increasing SMRs in the recent past was also seen for cause-
                specific deaths from chronic bronchitis, SMR = 330.0 (95% CI:268.1-
                406.2); tuberculosis, SMR = 193.4 (95% CI: 86.9-430.5); cardiovascular
                disease, SMR = 106.6 (95% CI: 102.0-111.5); all cancers, SMR = 107.1
                (95% CI:101.3-113.2); and lung cancer, SMR = 115.7 (95% CI: 104.8-
                127.7). The SMR for NMRD was 142.1 (95% CI: 132.9-152.0) in this recent
                period and remained highly statistically significant. In their previous
                analysis on mortality from lung cancer, reflecting follow-up through
                1995, Miller et al. (1997) had not found any increase in the risk of
                lung cancer mortality (OSHA 2013b, page 287).
                 OSHA reported that Miller and MacCalman (2010) used these analyses
                to estimate relative risks for a lifetime exposure of 5 gram-hours/m\3\
                (ghm-3) to quartz (OSHA 2013b, page 288). This is equivalent
                to approximately 55 [micro]g/m\3\ (0.055 mg/m\3\) for 45 years,
                assuming 2,000 hours per year of exposure and/or 100 ghm-3
                total dust. The authors estimated relative risks (see Miller and
                MacCalman (2010), Table 4, page 9) for various causes of death
                including pneumoconiosis, COPD, ischemic heart disease, lung cancer,
                and stomach cancer. Their results were based on models with single
                exposures to dust or respirable crystalline silica (quartz) or
                simultaneous exposures to both, with and without 15-year lag periods.
                Generally, the risk estimates were slightly greater using a 15-year lag
                period.
                 For the models using only quartz exposures with a 15-year lag,
                pneumoconiosis, RR = 1.21 (95% CI: 1.12-1.31); COPD, RR = 1.11 (95% CI:
                1.05-1.16); and lung cancer, RR = 1.07 (95% CI: 1.01-1.13) showed
                statistically significant increased risks.
                 For lung cancer, analyses based on these Cox regression methods
                provided strong evidence that, for these coal miners, quartz exposures
                were associated with increased lung cancer risk, but simultaneous
                exposures to coal dust were not associated with increased lung cancer
                risk. The relative risk (RR) estimate for lung cancer deaths using coal
                dust with a 15-year lag in the single exposure model was 1.03 (95% CI:
                0.96 to 1.10). In the model using both quartz and coal mine dust
                exposures, the RR based on coal dust decreased to 0.91, while that for
                quartz exposure remained statistically significant, increasing to a RR
                = 1.14 (95% CI: 1.04 to 1.25). According to Miller and MacCalman
                (2010), other analyses have shown that exposure to radon or diesel
                fumes was not associated with an increased cancer risk among British
                coal miners (OSHA 2013b, page 288).
                 The RRs in the Miller and MacCalman (2010) report were used to
                estimate excess lung cancer risk for OSHA's purposes. Life table
                analyses were done as in the other studies above. Based on the RR of
                1.14 (95% CI: 1.04-1.25) for a cumulative exposure of 5
                ghm10-3, the regression slope was recalculated as [beta] =
                0.0524 per 1,000 [micro]g-years (per mg/m\3\-years) and used in the
                life table program. Similarly, the 95-percent CI on the slope was
                0.0157-0.08926. From this study, the lifetime (to age 85) risk
                estimates for 45 years of exposure to 50 [micro]g/m\3\ (0.05 mg/m\3\)
                and 100 [micro]g/m\3\ (0.100 mg/m\3\) respirable crystalline silica
                were 6 and 13 excess lung cancer deaths per 1,000 workers,
                respectively. These lung cancer risk estimates were less by about 2- to
                4-fold than those estimated from the other cohort studies described
                above.
                 However, three factors might explain these differences. First,
                these estimates were adjusted for individual smoking histories so any
                smoking-related lung cancer risk (or smoking-respirable crystalline
                silica interaction) that might possibly be attributed to respirable
                crystalline silica exposure in the other studies were not reflected in
                the risk estimates derived from the study of these coal miners. Second,
                these coal miners had significantly increased risks of death from other
                lung diseases, which may have decreased the lung cancer-susceptible
                population. Of note, for example, were the higher increased SMRs for
                NMRD during the years 1959-2005 for this cohort (Miller and MacCalman,
                2010, Table 2, Page 7). Third, the difference in risk seen in these
                coal miners may have been the result of differences in the toxicity of
                quartz present in the coal mines as compared to the work environments
                of the other cohorts. One Scottish mine (Miller et al., 1998) in this
                10-mine study had been cited as having presented ``unusually high
                exposures to [freshly fractured] quartz.'' However, this was also
                described as an atypical exposure among miners working in the 10 mines.
                Miller and MacCalman (2010) stated that increased quartz-related lung
                cancer risk in their cohort was not confined to that Scottish mine
                alone. They also stated, ``The general nature of some quartz exposures
                in later years . . . may have been different from earlier periods when
                coal extraction was
                [[Page 44895]]
                largely manual . . .'' (OSHA 2013b, page 288).
                 All these factors in this mortality analysis for the British coal
                miner cohort could have combined to yield lower lung cancer risk
                estimates. However, OSHA believed that these coal miner-derived
                estimates were credible because of the quality of several study factors
                relating to both study design and conduct. In terms of design, the
                cohort was based on union rolls with very good participation rates and
                good reporting. The study group also included over 17,000 miners, with
                an average of nearly 30 years of follow-up, and about 60 percent of the
                cohort had died. Just as important was the high quality and detail of
                the exposure measurements, both of total dust and quartz. However, one
                exposure factor that may have biased the estimates upward was the lack
                of exposure information available for the cohort after the mines closed
                in the mid-1980s. Since the death ratio for lung cancer was higher
                during the last study period, 1990-2005, this period contributed to the
                increased lung cancer risk. It is possible that any quartz exposure
                experienced by the cohort after the mines had closed could have
                accelerated either death or malignant tumor (lung cancer) growth. By
                not accounting for this exposure, if there were any, the risk estimates
                would have been biased upwards. Although the 15-year lag period for
                quartz exposure used in the analyses provided slightly higher risk
                estimates than use of no lag period, the better fit seen with the lag
                may have been artificial. This may have occurred since there appeared
                to have been no exposures during the recent period when risks were seen
                to have increased (OSHA 2013b, page 289).
                 OSHA believed, as does MSHA, that this study of a large British
                coal mining cohort provided convincing evidence of the carcinogenicity
                of respirable crystalline silica. This large cohort study, with almost
                30 years of follow-up, demonstrated a positive exposure-response after
                adjusting for smoking histories. Additionally, the authors state that
                there was no evidence that exposure to potential confounders such as
                radon and diesel exhaust were associated with excess lung cancer risk
                (Miller and MacCalman (2010), page 270). MSHA is relying on the British
                studies conducted by Miller et al. (2007) as well as Miller and
                MacCalman (2010) to estimate the lung cancer risk in all miners.
                 MSHA found these two studies suitable for use in the quantitative
                characterization of health risks to exposed miners for several reasons.
                First, their study populations were of sufficient size to provide
                adequate statistical power to detect low levels of risk. Second,
                sufficient quantitative exposure data were available over a sufficient
                span of time to characterize cumulative respirable crystalline silica
                exposures of cohort members. Third, the studies either adjusted for or
                otherwise adequately addressed confounders such as smoking and exposure
                to other carcinogens. Finally, these investigators developed
                quantitative assessments of exposure-response relationships using
                appropriate statistical models or otherwise provided sufficient
                information that permits MSHA to do so.
                 MSHA implemented the risk model in its life table analysis so that
                the use of background rates of lung cancer and assumptions regarding
                length of exposure and lifetime were consistent across models. Thus,
                MSHA was able to estimate lung cancer risks associated with exposure to
                specific levels of respirable crystalline silica of interest to the
                Agency. MSHA used the Miller et al. (2007) and Miller and MacCalman
                (2010) model to estimate age-specific cumulative lung cancer mortality
                risk as EXP(0.0524 * cumulative exposure), lagged 15 years.
                 MSHA's PRA uses risk estimates derived from 10 coal mines in the
                U.K. (Miller et al., 2007; Miller and MacCalman, 2010). These
                investigators developed regression analyses for time-dependent
                estimates of individual exposures to respirable dust. Their analyses
                were based on the detailed individual exposure estimates of the PFR
                programme. To estimate mortality risk for lung cancer from the pooled
                cohort analysis, MSHA used the same life table approach as OSHA.
                However, for this life table analysis, MSHA used 2018 mortality rates
                for U.S. males (i.e., all-cause and background lung cancer). The 2018
                lung cancer death rates were based on the ICD-10 classification of
                diseases, C34.0, C34.2, C34.1, C34.3, C34.8, and C34.9. Lifetime risk
                estimates reflected excess risk through age 80. To estimate lung cancer
                risks, MSHA used the log-linear relative risk model, exp(0.0524 x
                cumulative exposure), lagged 15 years. The coefficient for this model
                was 0.0524 (OSHA 2013b, page 290).
                5. ESRD Mortality
                 Several epidemiological studies have found statistically
                significant associations between occupational exposure to respirable
                crystalline silica and renal disease, although others have failed to
                find a statistically significant association. These studies are
                discussed in the Health Effects document. Possible mechanisms suggested
                for respirable crystalline silica-induced renal disease included a
                direct toxic effect on the kidney, deposition of immune complexes (IgA)
                in the kidney following respirable crystalline silica-related pulmonary
                inflammation, and an autoimmune mechanism (Gregorini et al., 1993;
                Calvert et al., 1997; Parks et al., 1999; Steenland 2005b) (OSHA 2016a,
                81 FR 16286, 16310).
                 MSHA, like OSHA, chose the Steenland et al. (2002a) study to
                include in the PRA. In a pooled cohort analysis, Steenland et al.
                (2002a) combined the industrial sand cohort from Steenland et al.
                (2001b), the gold mining cohort from Steenland and Brown (1995a), and
                the Vermont granite cohort studies by Costello and Graham (1988). All
                three were included in portions of OSHA's PQRA for other health
                endpoints: under lung cancer mortality in Steenland et al. (2001a) and
                under silicosis mortality in the related work of Mannetje et al.
                (2002b). In all, the combined cohort consisted of 13,382 workers with
                exposure information available for 12,783. The analysis demonstrated
                statistically significant exposure-response trends for acute and
                chronic renal disease mortality with quartiles of cumulative respirable
                crystalline silica exposure (OSHA 2016a, 81 FR 16286, 16310).
                 The average duration of exposure, cumulative exposure, and
                concentration of respirable crystalline silica for the pooled cohort
                were 13.6 years, 1,200 [micro]g/m\3\-years (1.2 mg/m\3\-years), and 70
                [micro]g/m\3\ (0.07 mg/m\3\), respectively. Renal disease risk was most
                prevalent among workers with cumulative exposures of 500 [micro]g/m\3\
                or more (Steenland et al., 2002a). SMRs (compared to the U.S.
                population) for renal disease (acute and chronic glomerulonephritis,
                nephrotic syndrome, acute and chronic renal failure, renal sclerosis,
                and nephritis/nephropathy) were statistically significant and elevated
                based on multiple cause of death data (SMR 1.28, 95% CI: 1.10-1.47, 194
                deaths) and underlying cause of death data (SMR 1.41, 95% CI: 1.05-
                1.85, 51 observed deaths) (OSHA 2013b, page 315).
                 A nested case-control analysis was also performed which allowed for
                more detailed examination of exposure-response. This analysis included
                95 percent of the cohort for which there were adequate work history and
                quartz exposure data. This analysis included 50 cases for underlying
                cause mortality and 194 cases for multiple-cause mortality. Each case
                was matched by race, sex, and age within 5 years to 100 controls from
                the cohort. Exposure-response trends were examined in a
                [[Page 44896]]
                categorical analysis where renal disease mortality of the cohort
                divided by exposure quartile was compared to U.S. rates (OSHA 2013b,
                page 315).
                 In this analysis, statistically significant exposure-response
                trends for SMRs were observed for multiple-cause (p < 0.000001) and
                underlying cause (p = 0.0007) mortality (Steenland et al., 2002a; Table
                1; Page 7).
                 With the lowest exposure quartile group serving as a referent, the
                case-control analysis showed monotonic trends in mortality with
                increasing cumulative exposure. Conditional regression models using
                log-cumulative exposure fit the data better than cumulative exposure
                (with or without a 15-year lag) or average exposure. Odds ratios by
                quartile of cumulative exposure were 1.00, 1.24, 1.77, and 2.86 (p =
                0.0002) for multiple cause analyses and 1.00, 1.99, 1.96, and 3.93 for
                underlying cause analyses (p = 0.03) (Steenland et al., 2002a; Table 2;
                Page 7). For multiple-cause mortality, the exposure-response trend was
                statistically significant for cumulative exposure (p = 0.004) and log-
                cumulative exposure (p = 0.0002), whereas for underlying cause
                mortality, the trend was statistically significant only for log-
                cumulative exposure (p = 0.03). The exposure-response trend was
                homogeneous across the three cohorts and interaction terms did not
                improve model fit (OSHA 2013b, pages 216, 315).
                 Based on the exposure-response coefficient for the model with the
                log of cumulative exposure, Steenland (2005) estimated lifetime excess
                risks of death (age 75) over a working life (age 20 to 65). At 100
                [micro]g/m\3\ (0.1 mg/m\3\) respirable crystalline silica, this risk
                was 5.1 percent (95% CI 3.3-7.3) for ESRD based on 23 cases (Steenland
                et al., 2001b). It was 1.8 percent (95% CI 0.8-9.7) for kidney disease
                mortality (underlying), based on 51 deaths (Steenland et al., 2002a)
                above a background risk of 0.3 percent (OSHA 2013b, page 216).
                 MSHA notes that these studies added to the evidence that renal
                disease is associated with respirable crystalline silica exposure.
                Statistically significant increases in odds ratios and SMRs were seen
                primarily for cumulative exposures of >500 [micro]g/m\3\-years (0.5 mg/
                m\3\-years). Steenland (2005b) noted that this could have occurred from
                working for 5 years at an exposure level of 100 [micro]g/m\3\ (0.1 mg/
                m\3\) or 10 years at 50 [micro]g/m\3\ (0.05 mg/m\3\).
                 OSHA had a large body of evidence, particularly from the three-
                cohort pooled analysis (Steenland et al., 2002a), on which to conclude
                that respirable crystalline silica exposure increased the risk of renal
                disease mortality and morbidity. The pooled analysis by Steenland et
                al. (2002a) involved a large number of workers from three cohorts with
                well-documented, validated job-exposure matrices. These investigators
                found a positive, monotonic increase in renal disease risk with
                increasing exposure for underlying and multiple cause data. Thus, the
                exposure and work history data were unlikely to have been seriously
                misclassified. However, there are considerably less data available for
                renal disease than there are for silicosis mortality and lung cancer
                mortality. Nevertheless, OSHA concluded that the underlying data were
                sufficient to provide useful estimates of risk and included the
                Steenland et al. (2002a) analysis in its PQRA (OSHA 2013b, pages 229,
                316).
                 To estimate renal disease mortality risk from the pooled cohort
                analysis, OSHA implemented the same life table approach as was done for
                the assessments on lung cancer and NMRD. However, for this life table
                analysis, OSHA used 1998 all-cause and background renal mortality rates
                for U.S. males, rather than the 2006 rates used for lung cancer and
                NMRD. The 1998 rates were based on the ICD-9 classification of
                diseases, which was the same as used by Steenland et al. (2002a) to
                ascertain the cause of death of workers in their study. However, U.S.
                cause-of-death data from 1999 to present are based on the ICD-10, in
                which there were considerable changes in the classification system for
                renal diseases. According to CDC (2001), the change in the
                classification from ICD-9 to ICD-10 increased death rates for
                nephritis, nephritic syndrome, and nephrosis by 23 percent, in large
                part due to reclassifying ESRD. The change from ICD-9 to ICD-10 did not
                materially affect background rates for those diseases grouped as lung
                cancer or NMRD. Consequently, OSHA conducted its analysis of excess
                renal disease mortality associated with respirable crystalline silica
                exposure using background mortality rates for 1998. As before, lifetime
                risk estimates reflected excess risk through age 85. To estimate renal
                mortality risks, OSHA used the log-linear model with log-cumulative
                exposure that provided the best fit to the pooled cohort data
                (Steenland et al., 2002a). The coefficient for this model was 0.269 (SE
                = 0.120) (OSHA 2013b, page 316). Based on the life table analysis, OSHA
                estimated that exposure to the former general industry exposure limit
                of 100 [micro]g/m\3\ and to the final exposure limit of 50 [micro]g/
                m\3\ over a working life would result in a lifetime excess renal
                disease risk of 39 (95% CI: 2-200) and 32 (95% CI: 1.7-147) deaths per
                1,000, respectively. OSHA also estimated lifetime risks associated with
                the former construction and shipyard exposure limits of 250 and 500
                [micro]g/m\3\. These lifetime excess risks ranged from 52 (95% CI 2.2-
                289) to 63 (95% CI 2.5-368) deaths per 1,000 workers (OSHA 2013b, page
                316).
                 MSHA concludes that the evidence supporting causality regarding
                renal risk outweighs the evidence casting doubt on that conclusion.
                However, MSHA acknowledges the uncertainty associated with the
                divergent findings in the renal disease literature. To estimate renal
                disease mortality risk from the pooled cohort analysis, MSHA
                implemented the same life table approach as OSHA. However, MSHA's life
                table analysis used 2018 all-cause and 1998 background renal mortality
                rates for U.S. males. The 1998 renal death rates were based on the ICD-
                9 classification of diseases, 580-589. This is the same classification
                used by Steenland et al. (2002a) to ascertain the cause of death of
                workers in their study. Consequently, MSHA conducted its analysis of
                excess ESRD mortality associated with exposure to respirable
                crystalline silica using background mortality rates for 1998. The U.S.
                cause-of-death data from 2018 were used as well. Lifetime risk
                estimates reflect excess risk through age 85. To estimate ESRD
                mortality risks, MSHA used the log-linear model with log-cumulative
                exposure that provided the best fit to the pooled cohort data
                (Steenland et al., 2002a), as EXP(0.269 * ln (cumulative exposure)).
                The coefficient for this model was 0.269 (SE = 0.120) (OSHA 2013b, page
                316).
                6. Coal Workers' Pneumoconiosis (CWP)
                 Exposure to respirable coal mine dust causes lung diseases
                including CWP, emphysema, silicosis, and chronic bronchitis, known
                collectively as ``black lung.'' These diseases are debilitating,
                incurable, and can result in disability and premature death. There are
                no specific treatments to cure CWP or COPD. These chronic effects may
                progress even after miners are no longer exposed to coal dust.
                 MSHA's 2014 coal dust rule quantified benefits among coal miners
                related to reduced cases of CWP due to lower exposure limits for
                respirable coal mine dust. In this PRA, MSHA has not quantified the
                reduction in risk associated with CWP among coal miners. Nonetheless,
                MSHA believes that the proposed rule would reduce the excess risk of
                this disease. Many coal
                [[Page 44897]]
                miners work extended shifts, thus increasing their potential exposure
                to respirable crystalline silica. The result of calculating exposures
                based on a full-shift 8-hour TWA would be more protective. Thus, the
                proposed rule is expected to provide additional reductions in CWP risk
                beyond those ascribed in the 2014 coal dust rule. However, exposure-
                response relationships based on respirable crystalline silica exposure
                are not available for CWP, so the reductions in this disease due to
                reductions in silica exposure cannot be quantified.
                D. Overview of Results
                 Table VI-4 summarizes the PRA's main results: once it is fully
                effective (and all miners have been exposed only under the proposed
                PEL), the proposed rule is expected to result in at least 799 avoided
                deaths and 2,809 avoided cases of silicosis morbidity among the working
                miner population. These numbers represent the lifetime health outcomes
                expected to occur after both 45 years of employment under the proposed
                PEL (from 21 through 65 years of age) and 15 years of retirement (up to
                80 years of age). These estimates of the avoided lifetime excess
                mortality and morbidity represent the final calculations based on the 5
                selected models and the observed exposure data. The first group of
                miners that would experience the avoided lifetime fatalities and
                illnesses shown in Table VI-4 is the population living 60 years after
                promulgation of the proposed rule. In other words, this group would
                only contain miners exposed under the proposed rule. To calculate
                benefits associated with the proposed rulemaking, the economic analysis
                monetizes avoided deaths and illnesses while accounting for the fact
                that, during the first 60 years following promulgation, miners would
                have fewer avoided lifetime fatalities and illnesses because they would
                be exposed under both the existing standards and the proposed PEL.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.020
                 Table VI-5 summarizes miners' expected percentage reductions in
                lifetime excess risk of developing or dying from certain diseases due
                to their reduced respirable crystalline silica exposure expected to
                result from implementation of the proposed rule. The lifetime excess
                risk reflects the probability of developing or dying from diseases over
                a maximum lifetime of 45 years of exposure during employment and 15
                years of retirement. The excess risk reduction compares (a) miners'
                excess health risks associated with respirable crystalline silica
                exposure at the limits included in MSHA's existing standards to (b)
                miners' excess health risks associated with exposure at this standard's
                proposed PEL. MSHA expects full-scale implementation to reduce lifetime
                excess mortality risk by 9.5 percent and to reduce lifetime excess
                silicosis morbidity risk by 41.9 percent. Excess mortality risk
                includes the excess risk of death due to silicosis, NMRD, lung cancer,
                and ESRD.
                [[Page 44898]]
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                BILLING CODE 4520-43-P
                 Table VI-6 presents MSHA's estimates of lifetime excess risk per
                1,000 miners at exposure levels equal to the existing standards, the
                proposed PEL, and the proposed action level. These estimates are
                adjusted for FTE ratios and thus utilize cumulative exposures that more
                closely reflect the average hours worked per year.\21\ For an MNM miner
                who is presently exposed at the existing PEL of 100 [mu]g/m\3\ (and
                given the weighted average FTE ratio of 0.87), implementing the
                proposed PEL would lower the miner's lifetime excess risk of death by
                58.8 percent for silicosis, 45.6 percent for NMRD (not including
                silicosis), 52.0 percent for lung cancer, and 19.9 percent for ESRD.
                The MNM miner's risk of acquiring a non-fatal case of silicosis (would
                decrease by 80.4 percent).
                ---------------------------------------------------------------------------
                 \21\ The FTE ratios used in these calculations are a weighted
                average of the FTE ratio for production employees and the FTE ratio
                for contract miners.
                ---------------------------------------------------------------------------
                 For a coal miner who is currently exposed at the existing exposure
                limit of 85.7 [mu]g/m\3\ (and given the weighted average FTE ratio of
                0.99), implementing the proposed PEL would lower the miner's lifetime
                excess risk of death by 42.3 percent for silicosis mortality, 40.2
                percent for NMRD mortality (not including silicosis), 43.5 percent for
                lung cancer mortality, and 15.8 percent for ESRD mortality. The coal
                miner's lifetime excess risk of acquiring non-fatal silicosis would
                decrease by 73.8 percent. While even greater reductions would be
                achieved at exposures equal to the proposed action level (25 [mu]g/
                m\3\), some residual risks do remain at exposures of 25 [mu]g/m\3\.
                Notably, at the proposed action level, ESRD risk is still 20.7 per
                1,000 MNM miners and 21.6 per 1,000 coal miners. At the proposed action
                level, risk of non-fatal silicosis is 16.3 per 1,000 MNM miners and
                16.9 per 1,000 coal miners.
                [[Page 44899]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.022
                BILLING CODE 4520-43-C
                E. Healthy Worker Bias
                 MSHA accounted for ``healthy worker survivor bias'' in estimating
                the risks for coal and MNM miners. The healthy worker survivor bias
                causes epidemiological studies to underestimate excess risks associated
                with occupational exposures. As with most worker populations, miners
                are composed of heterogeneous groups that possess varying levels of
                background health. Over the course of miners' careers, illness tends to
                remove the most at-risk workers from the workforce prematurely, thus
                causing the highest cumulative exposures to be experienced by the
                healthiest workers who are most immune to risk. Failing to account for
                this imbalance of cumulative exposure across workers negatively biases
                risk estimates, thereby underestimating true risks in the population.
                Keil et al. (2018) analyzed a type of healthy worker bias referred to
                as the healthy worker survivor bias in the context of OSHA's 2016 life
                table estimates for risk associated with respirable crystalline silica
                exposure. After analyzing data from 65,999 workers pooled across
                multiple countries and industries, Keil et al. found that the ``healthy
                worker survivor bias results in a 28% underestimate of risk for lung
                cancer and a 50% underestimate for other causes of death,'' with risk
                being defined as ``cumulative incidence of mortality [at age 80].''
                 Given that MSHA has calculated risks using the same underlying
                epidemiological studies OSHA used in 2016, the healthy worker survivor
                bias is likely impacting the estimates in Table VI-6 of lifetime excess
                risk and lifetime excess cases avoided. Accordingly, as part of a
                sensitivity analysis, MSHA re-estimated risks for MNM and coal miners
                to account for the healthy worker survivor bias. MSHA adjusted for this
                effect by increasing the risk estimates of lung cancer risk by 28
                percent and increasing the risk of each other disease by 50 percent.
                This produced larger estimates of lifetime excess risk reductions and
                lifetime excess cases avoided, which are presented in PRA Table 23
                through PRA Table 26 of the PRA document. As these tables show, when
                adjusting for the healthy worker survivor bias, the proposed PEL would
                decrease lifetime silicosis morbidity risk by 20.8 cases per 1,000 MNM
                miners (compared to the unadjusted estimate of 13.9 cases per 1,000 MNM
                miners, see PRA Table 15 of the PRA document) and 5.0 cases per 1,000
                coal miners (compared to 3.3 cases per 1,000 coal miners, see PRA Table
                16 of the PRA document). Still accounting for the healthy worker
                survivor bias, the proposed PEL would decrease total morbidity by 3,848
                lifetime cases among MNM miners (compared to 2,566 cases, see PRA Table
                17 of the PRA document) and by 366
                [[Page 44900]]
                lifetime cases among coal miners (compared to 244 cases, see PRA Table
                18 of the PRA document). Among the current MNM and coal mining
                populations, implementation of the proposed PEL during their full lives
                would have prevented 1,091 deaths and 94 deaths, respectively, over
                their lifetimes (compared to unadjusted estimates of 736 deaths and 63
                deaths, respectively).
                 MSHA believes adjusted estimates for the healthy worker survivor
                bias are more reliable than unadjusted estimates. However, given that
                the literature does not support specific scaling factors for each of
                the health endpoints analyzed, these adjustments for the healthy worker
                survivor bias have not been incorporated into the final lifetime excess
                risk estimates that served as the basis for monetizing benefits.
                Because the monetized benefits do not account for the healthy worker
                bias, MSHA believes the reductions in lifetime excess risks and
                lifetime excess cases, as well as the monetized benefits, likely
                underestimate the true reductions and benefits attributable to the
                proposed rule.
                F. Uncertainty Analysis
                 MSHA conducted extensive uncertainty analyses to assess the impact
                on risk estimates of factors including treatment of data in excess of
                the proposed PEL, sampling error, and use of average rather than median
                point estimates for risk. The impact of excluding insufficient mass
                (weight) samples was also examined.
                1. Alternate Treatment of Exposure Samples in Excess of the Proposed
                Exposure Limit
                 To estimate excess risks and excess cases under the proposed PEL,
                MSHA assumed that no exposures would exceed the proposed limit, which
                effectively reduced any exposures exceeding 50 [mu]g/m\3\ to 50 [mu]g/
                m\3\. However, if mines implement controls with the goal of reducing
                exposures to 50 [mu]g/m\3\ on every shift, then some exposure currently
                in excess of 50 [mu]g/m\3\ would likely decrease below the proposed
                PEL. For this reason, the estimation method of capping all exposure
                data at 50 [mu]g/m\3\ represents a ``lowball'' estimate of risk
                reductions due to the proposed PEL. In this section, MSHA presents
                estimates using an alternate ``highball'' method wherein exposures
                exceeding 50 [mu]g/m\3\ are set equal to the median exposure value for
                the 25-50 [mu]g/m\3\ exposure group. Because this highball method
                attributes larger reductions in exposure to the proposed PEL, it
                estimates higher lifetime excess risk reductions and more avoided
                lifetime excess cases.
                 As with lifetime excess risks, the highball method also yields
                larger reductions in lifetime excess cases. Using the highball method,
                MNM miners are expected to experience 3,111 fewer cases of non-fatal
                silicosis and coal miners are expected to experience 344 fewer cases of
                non-fatal silicosis over their lifetimes. MNM miners would experience
                1,137 fewer deaths and coal miners would experience 123 fewer deaths
                over their lifetimes. Compared to the lowball method--which estimates
                that the proposed PEL would prevent a total of 2,809 lifetime cases of
                non-fatal silicosis and 799 lifetime excess deaths (among both MNM and
                coal miners)--the highball method estimates totals of 3,445 avoided
                lifetime cases of non-fatal silicosis and 1,260 avoided lifetime excess
                deaths.
                2. Sampling Error in Exposure Data
                 To quantify the impact of sampling uncertainty on the risk
                estimates, 1,000 bootstrap resamples of the original exposure data were
                generated (sampling with replacement). The resamples were stratified by
                commodity to preserve the relative sampling frequencies of coal, metal,
                non-metal, sand and gravel, crushed limestone, and stone observations
                in the original dataset. Risk calculations were repeated on each of the
                1,000 bootstrap samples, thereby generating empirical distributions for
                all risk estimates. From these empirical distributions, 95 percent
                confidence intervals were calculated. These confidence intervals
                characterize the uncertainty in the risk estimates arising from
                sampling error in the exposure data. All lifetime excess risk estimates
                had narrow confidence intervals, indicating that the estimates of
                lifetime excess morbidity and mortality risks have a high degree of
                precision.
                 In regard to use of average, rather than median, point estimates of
                risk, the estimates acquired from average exposures are similar to the
                estimates from median exposures, with 95 percent confidence intervals
                having similar widths. However, the 95 percent confidence intervals are
                not always overlapping, and average exposures tended to yield higher
                estimates of reduced morbidity and mortality. Among MNM miners, MSHA
                expects the proposed PEL to produce lifetime risk reductions of
                silicosis morbidity of 2,546-2,777 using average exposures (see PRA
                Table 41 of the PRA document), compared to 2,453-2,683 using median
                exposures (see PRA Table 37 of the PRA document). Among coal miners,
                this reduction is expected to be 246-279 using average exposures (see
                PRA Table 42 of the PRA document), compared to 229-265 using median
                exposures (see PRA Table 38 of the PRA document). The proposed PEL is
                estimated to reduce lifetime excess mortality by 735-791 MNM miner
                deaths and 65-73 coal miner deaths using average exposures (see PRA
                Tables 41 and 42 of the PRA document), compared to 708-764 MNM miner
                deaths and 60-69 coal miner deaths using median exposures (see PRA
                Tables 37 and 38 of the PRA document).
                3. Samples With Insufficient Mass
                 The MNM exposure data gathered by enforcement from January 1, 2005,
                through December 31, 2019, contain samples that were analyzed using the
                P-2 method. As discussed, the P-2 method specifies that filters are
                only analyzed for quartz if they achieve a net mass gain of 0.100 mg or
                more. If cristobalite is requested, a mass gain of 0.050 mg or more is
                required for a filter to be analyzed (MSHA 2022a). During the 15-year
                sample period for MNM exposure data, 40,618 MNM samples were not
                analyzed because the filter failed to meet the P-2 minimum net mass
                (weight) gain requirements.
                 Similarly, the coal exposure data gathered by enforcement from
                August 1, 2016, through July 31, 2021, contains samples that were
                analyzed using the P-7 method. The P-7 method requires a minimum sample
                mass of 0.100 mg \22\ of dust for the sample to be analyzed for quartz.
                During the five-year sample period for coal exposure data, 63,127 coal
                samples were not analyzed because the P-7 method's minimum mass
                requirement was not met.
                ---------------------------------------------------------------------------
                 \22\ Often the threshold for analyzing Coal samples is >=0.1 mg.
                There are, however, some exceptions based on Sample Type and
                Occupation Code. For samples with Sample Type 4 or 8, if the
                sample's Occupation Code is not 307, 368, 382, 383, 384, or 386,
                then the threshold is >=0.2 mg.
                ---------------------------------------------------------------------------
                 For samples that do not meet a minimum threshold for total
                respirable dust mass, the MSHA lab does not analyze these samples for
                respirable crystalline silica. These samples were excluded from the
                risk analysis because their concentrations of respirable crystalline
                silica are not known. Nonetheless, the unanalyzed samples all had very
                low total respirable dust mass, making it unlikely that many would have
                exceeded the existing standards or the proposed PEL. Excluding these
                unanalyzed samples from the exposure datasets thus may introduce bias,
                potentially causing the Agency to overestimate the proportion of high-
                intensity exposure values.
                [[Page 44901]]
                 As a sensitivity analysis, MSHA used imputation techniques to
                estimate the respirable crystalline silica mass for each sample based
                on the sample weight and the median percent silica content for each
                commodity and occupation. All the unanalyzed samples with imputed
                concentrations were estimated to be https://www.cdc.gov/niosh/topics/noms/default.html. The NOMS database provides detailed
                mortality data for the 11-year period from 1999, 2003 to 2004, and
                2007 to 2014. https://;wwwn.cdc.gov/niosh-noms/industry2.aspx;
                accessed November 7, 2022.
                ---------------------------------------------------------------------------
                 In the case of coal mines, the proposed rule would establish a
                separate PEL for respirable crystalline silica. Under the existing
                standard, miners' exposure to quartz is tied to exposure to respirable
                coal mine dust, making it more difficult to monitor coal miners'
                exposure to respirable crystalline silica. The proposed separate
                standard would be more transparent and make compliance easier to track,
                allowing more effective control of respirable crystalline silica.
                 The proposed PEL of 50 [mu]g/m\3\ applies to a miner's full-shift
                exposure, calculated as an 8-hour TWA. Under this proposal, a miner's
                work shift exposure would be calculated as follows:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.023
                 Regardless of a miner's actual working hours (full shift), 480
                minutes would be used in the denominator. This means that the
                respirable crystalline silica collected over an extended period (e.g.,
                a 12-hour shift) would be calculated (or normalized) as if it were
                collected over 8 hours (480 minutes). For example, if a miner was
                sampled for 12 hours and 55 [mu]g of respirable crystalline silica was
                collected on the sample, the miner's respirable crystalline silica 8-
                hour TWA exposure would be 67.4 [mu]g/m\3\, calculated as follows:
                [GRAPHIC] [TIFF OMITTED] TP13JY23.024
                [[Page 44904]]
                 This proposed calculation method is the one that MSHA uses to
                calculate MNM miner exposures to respirable crystalline silica and
                other airborne contaminants; it differs from the existing method of
                calculating a coal miner's exposure to respirable coal mine dust. For
                coal miners, the existing calculation method uses the entire duration
                of a miner's work shift in both the denominator and numerator,
                resulting in the total mass of respirable coal mine dust collected over
                an entire work shift scaled by the sample's air volume over the same
                period.
                 MSHA's proposal to apply the existing method of calculating MNM
                miner exposure to all miners has two main advantages. First, the
                proposal would improve protection for coal miners who work longer
                shifts. The goal of the proposed respirable crystalline silica PEL is
                to prevent miners from suffering a body burden high enough to cause
                adverse health effects. If a miner works longer than 8 hours, the
                miner's body (lungs, in particular) may not have sufficient time to
                eliminate the respirable crystalline silica that enters the lungs or to
                reduce the body burden.\28\ Coal miners commonly work extended shifts,
                with many working 10-hour or longer shifts.\29\ In such cases, a coal
                miner's recovery time would be reduced from 16 hours to 12 to 14 hours.
                To account for this increased risk, the proposed calculation (like the
                current MNM calculation method) normalizes to an 8-hour TWA. The
                concept of adjusting occupational exposure limits for ``extended
                shifts'' has been addressed by researchers (Brief and Scala, 1986;
                Elias, 2013).
                ---------------------------------------------------------------------------
                 \28\ The pulmonary uptake and clearance of respirable
                crystalline silica are dependent upon many factors, including a
                miner's breathing patterns, exposure duration, concentration (dose),
                particle size, and durability or bio-persistence of the particle.
                These factors will also affect the time to clear particles, even
                after exposure ceases. Of principal concern is the possibility that
                a continuous dust exposure over an extended period of time (or high
                dust level exposure during a short exposure period may excessively
                tax lung defense mechanisms (Industrial Minerals Association-North
                America and Mine Safety and Health Administration, 2008).
                 The ACGIH (2022), while not specifically addressing silica, has
                stated, ``numerous mathematical models to adjust for unusual work
                schedules have been described. In terms of toxicologic principles,
                their general objective is to identify a dose that ensures that the
                daily peak body burden or weekly peak body burden does not exceed
                that which occurs during a normal 8-hours/day, 5-day/week shift.''
                There are associated concerns with the body burden from an ``unusual
                work schedule'' such as a 10- or a 12- hour shift. As Elias (2013)
                stated, ``if the length of the workday is increased, there is more
                time for the chemical to accumulate, and less time for it to be
                eliminated. It is assumed that the time away from work will be
                contamination free. The aim is to keep the chemical concentrations
                in the target organs from exceeding the levels determined by the
                TLVs[supreg] (8-hour day, 5-day week) regardless of the shift
                length. Ideally, the concentration of material remaining in the body
                should be zero at the start of the next day's work.''
                 \29\ Sampling hours of coal mine dust samples approximate the
                working hours of coal miners who were sampled. According to the coal
                mine dust samples for a 5-year period (August 2016-July 2021), 90
                percent of the samples by MSHA inspectors were from miners working 8
                hours or longer and about 43 percent of the samples from miners
                working 10 hours or longer. The dust samples by coal mine operators
                show that over 98 percent of them were from miners working 8 hours
                or longer and over 26 percent from the miners working 10 hours or
                longer. The coal mine dust samples are available at Mine Data
                Retrieval System [verbar] Mine Safety and Health Administration
                (MSHA).
                ---------------------------------------------------------------------------
                 Second, applying the proposed calculation method for all miners
                would be more straightforward and easier to understand for mine
                operators, miners, and other stakeholders. The current calculation
                method for coal miners requires first determining the percentage of
                quartz in the sample of collected respirable dust, then dividing the
                result into the number 10 to calculate an exposure limit for respirable
                dust. The proposed calculation method requires only measuring the total
                mass of respirable crystalline silica collected and dividing it by the
                air volume over 480 minutes.
                 This proposal would establish a lower PEL and apply it to all
                miners using a consistent method for calculating exposures. These
                changes would improve the health and safety of miners while making
                compliance more straightforward and transparent. The 8-hour TWA is the
                ``gold standard'' for exposure assessments, except in scenarios
                involving chemical substances that are predominantly fast-acting (i.e.,
                those evoking acute effects). NIOSH has also supported the use of the
                TWA and discussed this term since the publication of the NIOSH Pocket
                Guide to Chemical Hazards (First Edition, 1973) (the ``White Book'').
                4. Section 60.11--Methods of Compliance
                 This proposed section would require mine operators to install, use,
                and maintain feasible engineering and administrative controls to keep
                each miner's exposure to respirable crystalline silica at or below the
                proposed PEL. Mine operators would be required to use feasible
                engineering controls as the primary means of controlling respirable
                crystalline silica; administrative controls would be used, when
                necessary, as a supplementary control. However, under the proposal,
                rotation of miners--that is, assigning more than one miner to a high-
                exposure task or location, and rotating them to keep each miner's
                exposure below the PEL--would be prohibited. Under the proposal,
                respiratory protection equipment could be used in specific and limited
                situations, as discussed in Sec. 60.14--Respiratory Protection, but
                the use of respiratory protection equipment would not be acceptable as
                a method of compliance.
                 This proposed approach to controlling miners' exposures is
                consistent with MSHA's existing standards, NIOSH's recommendations, and
                generally accepted industrial hygiene principles. The proposal is
                consistent with MSHA's existing respirable dust standards, which
                require engineering controls as the primary means to protect miners.
                MSHA's experience and data show that engineering controls provide
                improved, more consistent, and more reliable protection for miners than
                administrative controls or respirators. In its recommendations, NIOSH
                also stressed the importance of using engineering controls to control
                miners' exposure to respirable crystalline silica. In 1995, NIOSH
                recommended that the dust standard state that ``the mine operator shall
                use engineering controls and work practices [administrative controls]
                to keep worker exposures at or below the REL [recommended exposure
                limit]. . .'' (NIOSH 1995a). In its public response to MSHA's 2019
                Request for Information for Respirable Silica (Quartz) (84 FR 45452,
                Aug. 29, 2019), NIOSH also supported the use of engineering controls as
                the primary means of protecting miners from exposure to respirable
                crystalline silica, stating that ``[r]espirators should only be used
                when engineering control systems are not feasible. Engineering control
                systems, such as adequate ventilation or scrubbing of contaminants, are
                the preferred control methods for reducing worker exposures.'' \30\
                ---------------------------------------------------------------------------
                 \30\ Comment from Paul Schulte, NIOSH (Oct. 23, 2019) to Docket
                No. MSHA 2016-0013.
                ---------------------------------------------------------------------------
                 As discussed in the technological feasibility and preliminary
                regulatory impact analysis sections of the preamble, MSHA has
                preliminarily determined that engineering and administrative controls
                are technologically and economically feasible, and the use of these
                controls would be sufficient to achieve compliance with the proposed
                PEL. After reviewing the effectiveness of various exposure reduction
                controls which are currently available and have been successfully
                adopted in various combinations in mines, MSHA has concluded that all
                mine operators can ensure miners' exposures are below the proposed PEL
                through implementing some combination of enhanced
                [[Page 44905]]
                maintenance of existing engineering controls, new engineering controls,
                and improved administrative controls/work practices.
                a. Engineering Controls
                 Proposed paragraph (a) would require mine operators to use feasible
                engineering controls as the primary means of controlling respirable
                crystalline silica; administrative controls would be used, when
                necessary, as a supplementary control.
                 This proposed paragraph would require engineering controls to be
                used as the primary means of controlling respirable crystalline silica.
                Engineering controls can include ventilation systems (i.e., main,
                auxiliary, local exhaust), dust suppression devices (i.e., wet dust
                suppression and airborne capture), and enclosed cabs or control booths
                with filtered breathing air, as well as changes in materials handling,
                equipment used in a process, ventilation, and dust capture mechanisms.
                Engineering controls generally suppress (e.g., using water sprays,
                wetting agents, foams, water infusion), dilute (e.g., ventilation),
                divert (e.g., water sprays, passive barriers, ventilation), or capture
                dust (e.g., dust collectors) to minimize the exposure of miners working
                in the surrounding areas. The use of automated ore-processing equipment
                and use of video cameras for remote scanning and monitoring can also
                help to reduce or eliminate miners' exposures to respirable crystalline
                silica.
                 Engineering controls are the most effective means of controlling
                the amount of dust to which miners are exposed. They have the advantage
                of addressing dust at its source, thus ensuring that all miners in an
                area are adequately protected from overexposure to respirable
                crystalline silica. Engineering controls provide more consistent and
                more reliable protection to miners than other interventions because the
                controls are not dependent on an individual's performance, supervision,
                or intervention to function as intended. In contrast to other controls
                and other interventions, engineering controls can also be continually
                evaluated and monitored relatively easily, allowing their effectiveness
                to be assessed regularly.
                b. Administrative Controls
                 Under the proposed rule, mine operators would be permitted to
                supplement engineering controls with administrative controls as a means
                of controlling exposure to respirable crystalline silica.
                Administrative controls include practices that change the way tasks are
                performed to reduce a miner's exposure. These practices would include
                housekeeping procedures; proper work positions of miners; cleaning of
                spills; and measures to prevent or minimize contamination of clothing
                to help decrease miners' exposure to respirable crystalline silica.
                 Administrative controls require significant effort by mine
                operators to ensure that miners understand and follow the controls. If
                not properly implemented, understood, or followed, or if persons
                responsible for administrative controls do not properly supervise their
                implementation, they would not be effective in controlling miners'
                overexposure to respirable crystalline silica. Therefore,
                administrative controls would be permitted only as supplementary
                measures, with engineering controls required as the primary means of
                protection.
                 Proposed paragraph (b) would prohibit mine operators from using
                rotation of miners--that is, assigning more than one miner to a high-
                exposure task or location, and rotating them to keep each miner's
                exposure below the PEL--as an acceptable method of compliance. MSHA
                does not believe that rotation of miners is consistent with the
                Agency's regulatory framework or its mandate under the Mine Act. Based
                on MSHA's experience, rotation of miners may, if permitted, reduce the
                amount of time each miner is exposed to the hazard by rotating miners
                out of the task faster. However, it would increase the number of miners
                working in high-exposure tasks or areas and would lead to increased
                material impairment of health or functional capacity for the additional
                miners.
                 The concept of miner rotation, which may be an appropriate control
                to minimize musculoskeletal stress, is not acceptable for work
                involving carcinogens. Based on NIOSH's publication entitled ``Current
                Intelligence Bulletin 68: NIOSH Chemical Carcinogen Policy,'' MSHA
                believes that the primary way to prevent occupational cancer is to
                reduce worker exposure to chemical carcinogens as much as possible
                through elimination or substitution at the source and through
                engineering controls (NIOSH 2017b).
                5. Section 60.12--Exposure Monitoring
                 The proposed section addresses exposure monitoring, sampling
                method, and sample analysis methods. MSHA is proposing two types of
                exposure monitoring: quantitative, through sampling the air that miners
                breathe, and qualitative, through semi-annual evaluations of how
                changes in mining processes, production activities, and dust control
                systems affect exposures. For the quantitative monitoring, MSHA is
                proposing four types of sampling--baseline, periodic, corrective
                actions, and post-evaluation--together with methods for sampling and
                analyzing the samples.
                 The proposed exposure monitoring requirements, which include
                sampling miners' exposures, would facilitate operator compliance with
                the proposed PEL, harmonize MSHA's approach to monitoring and
                evaluating respirable crystalline silica exposures in both MNM and coal
                mines, and lead to better protection of miners' health. Monitoring
                miner exposures to airborne contaminants is an effective risk
                management tool. The sampling and evaluation requirements of proposed
                Sec. 60.12 are designed to ensure maximum protection for miners and
                prevent them from suffering material impairment of health or functional
                capacity, while providing operators flexibility to tailor their
                sampling program to the miners' risk of exposure to respirable
                crystalline silica at their mines.
                 The first type of exposure monitoring under the proposed rule is
                quantitative sampling for miners' exposures to respirable crystalline
                silica. This sampling would help mine operators determine the extent
                and degree of exposures, identify sources of exposure and potential
                overexposure, maintain updated and accurate records of exposures,
                select the most appropriate control methods, and evaluate the
                effectiveness of those controls. The proposal would require operators
                to conduct sampling for a miner's regular full shift during typical
                mining activities. The second type of exposure monitoring under the
                proposed rule would be qualitative evaluations, which would help
                operators identify changes in mining conditions and processes that
                affect the exposure risk to miners.
                a. Section 60.12(a)--Baseline Sampling
                 The first action mine operators would take to assess miners'
                exposures under the proposed rule would be to conduct baseline
                sampling. Baseline sampling would provide an initial measurement of
                respirable crystalline silica exposures that would be compared to the
                proposed action level and the proposed PEL to determine the
                effectiveness of existing controls and the need for additional
                controls.
                 Proposed paragraph (a)(1) would require mine operators to perform
                baseline sampling to assess the full-shift, 8-hour TWA exposure of
                respirable crystalline silica for each
                [[Page 44906]]
                miner who is or may reasonably be expected to be exposed to respirable
                crystalline silica at any level. MSHA assumes that most mining
                occupations related to extraction and processing would meet the
                ``reasonably be expected'' threshold; however, MSHA recognizes that
                some miners may work in areas or perform tasks where exposures are not
                reasonably likely, and some miners may work in silica-free
                environments. Based on the Agency's experience, both MNM and coal mine
                operators generally know from their existing sampling data and MSHA's
                sampling data the occupations, work areas, and work activities where
                respirable crystalline silica exposures occur. The mine operator would
                be required to sample only those miners the operator knows or
                reasonably expects to be exposed to respirable crystalline silica.
                 The proposed provisions would require that, within the first 180
                days after the effective date of the final rule, the mine operator
                perform the baseline sampling. During this 180-day period, mine
                operators would acquire necessary sampling devices or sampling
                services, sample occupations or areas of known or reasonably expected
                exposures, identify appropriate laboratories, and arrange for analysis
                of samples. Given that the mining industry has experience with sampling
                programs for other airborne contaminants, as well as respirable
                crystalline silica, MSHA anticipates that the proposed 180 days would
                provide sufficient time for mine operators to comply with the proposed
                standard.
                 Under this proposed standard, mine operators would need to
                accurately characterize the exposure of each miner who is or may
                reasonably be expected to be exposed to respirable crystalline silica.
                As discussed later in detail, mine operators would be permitted to use
                representative sampling whenever sampling is required. In some cases,
                however, operators may have to sample all miners to obtain an accurate
                assessment of exposures.
                 This proposed requirement would ensure that mine operators have the
                quantitative information needed to evaluate miners' exposure risks,
                determine the adequacy of existing engineering and administrative
                controls, and make necessary changes to ensure miners are not
                overexposed. In addition, the results of the baseline sampling would
                determine further operator obligations for periodic sampling. A
                baseline sample result at or above the proposed action level but at or
                below the proposed PEL, would require operators to conduct periodic
                sampling under proposed Sec. 60.12(b). However, if the baseline sample
                indicated that exposures were below the proposed action level and
                operators can confirm those results, mine operators would not be
                required to conduct periodic sampling. The results can be confirmed in
                three ways: (1) sample data, collected by the operator or the Secretary
                in the 12 months preceding the baseline sampling, that also shows
                exposures below the proposed action level; (2) objective data (as
                defined in the proposal) confirming that a miner's exposure to
                respirable crystalline silica would remain below the proposed action
                level; or (3) another sample taken within 3 months showing exposure
                below the proposed action level.
                 Proposed paragraph (a)(2) would allow mine operators to use
                objective data to confirm the baseline sample result. Under this
                proposal, objective data must demonstrate that respirable crystalline
                silica would not be released in airborne concentrations at or above the
                action level under any expected conditions. Objective data, as defined
                in proposed Sec. 60.2, would include air monitoring data from
                industry-wide surveys that demonstrate miners' exposure to respirable
                crystalline silica associated with a particular product or material or
                a specific process, task, or activity. Objective data must reflect
                mining conditions that closely resemble the processes, material,
                control methods, work practices, and environmental conditions in the
                mine operator's current operations. The mine operator would have the
                burden of showing that the objective data characterizes miner exposures
                to respirable crystalline silica with sufficient accuracy.
                 Also, proposed paragraph (a)(2) would permit mine operators to use
                sampling conducted by the Secretary or mine operator within the
                preceding 12 months of baseline sampling to confirm miner exposures
                below the proposed action level. The proposed rule would require mine
                operator sampling that was conducted in accordance with sampling
                requirements in paragraph (f) and analyzed according to paragraph (g)
                of this section. Under proposed paragraph (a)(2), any subsequent
                sampling conducted by the operator or by the Secretary, collected
                within 3 months of the baseline sample, could also be used to confirm a
                baseline sample result.
                 MSHA believes that before sampling is discontinued for miners
                previously determined to be exposed at or above the proposed action
                level, it is necessary to confirm any sample result that indicates
                miner exposures are below the proposed action level. When such a result
                is confirmed by a second measurement, an operator could reasonably
                expect exposures to remain below the action level if mining conditions
                and practices do not change. However, as discussed later, under
                proposed paragraph (d), if there is any change in conditions or
                practices that could be reasonably expected to result in exposures at
                or above the action level, sampling to assess these exposures would be
                required.
                b. Section 60.12(b)--Periodic Sampling
                 Periodic sampling under the proposed rule would provide mine
                operators and miners with regular information about miners' exposures.
                Changes in exposure levels can be caused by changes in the mine
                environment, inadequate engineering controls, or other changes in
                mining processes or procedures. Periodic sampling would inform mine
                operators about increases in exposures in a timely manner so they can
                prevent potential overexposures. In addition, periodic sampling alerts
                operators and miners of the continued need to protect against the
                hazards associated with exposure to respirable crystalline silica. If a
                mine operator installs new engineering controls and/or starts new
                administrative control practices, periodic sampling would show whether
                those controls are working properly to achieve the anticipated health
                results and would document their effectiveness.
                 Proposed Sec. 60.12(b) would require periodic sampling of miners'
                exposures to respirable crystalline silica whenever the most recent
                sampling indicates that exposures are at or above the proposed action
                level but at or below the proposed PEL. Whether a mine operator would
                have to conduct periodic sampling under the proposal would depend on
                the results of the most recent sample, which could include a baseline
                sample, a corrective actions sample, or a post-evaluation sample, as
                well as samples taken by MSHA during its inspections. If operators are
                required to conduct periodic sampling, and periodic sampling results
                indicate that miner exposures are below the action level, a mine
                operator would be permitted to discontinue periodic sampling for those
                miners whose exposures are represented by these samples. If the most
                recent sample shows exposures at or above the action level but at or
                below the proposed PEL, periodic sampling every 3 months would continue
                until two consecutive sample analyses showed miners' exposures below
                the action level. MSHA believes that two consecutive sample analyses
                showing exposures below the
                [[Page 44907]]
                action level would indicate a low probability that prevailing mining
                conditions would result in overexposures.
                 MSHA believes that the proposed frequency for periodic sampling--
                repeating the sampling within 3 months--is practical for mine operators
                and protective of the health and safety of miners. MSHA has
                preliminarily concluded that the health risks caused by respirable
                crystalline silica overexposure warrant more regular sampling when
                exposure levels approach the proposed PEL, because this periodic
                sampling would provide a higher level of confidence that miners would
                not be overexposed. Due to the unique conditions of mining
                environments, where conditions change quickly and exposures to
                respirable crystalline silica can vary frequently, MSHA is proposing a
                three-month periodic sampling schedule (NIOSH, 2014e). This three-month
                schedule would provide a meaningful degree of confidence that mine
                operators would recognize quickly when exposures are increasing and
                approaching the proposed PEL and would respond by implementing
                additional controls to prevent overexposure. Periodic sampling data
                would also provide information that operators could use to select,
                implement, and maintain controls. MSHA has structured the proposal to
                balance the costs of periodic sampling requirements, including when
                sampling can be stopped, and the benefits of additional health
                protection for miners. Taking these factors into consideration, MSHA
                has preliminarily determined that the proposed frequency of periodic
                sampling is both economically and technologically feasible for mine
                operators. (See Section VIII. Technological Feasibility and Section IX.
                Summary of Preliminary Regulatory Impact Analysis.)
                 As with the baseline sampling in proposed paragraph (a), in meeting
                the requirements of this paragraph, mine operators would be allowed to
                sample a representative fraction of at least two miners. The exposure
                result would be attributed to the remaining miners represented by this
                sample, as discussed in more detail below. When miners are not
                performing the same job under the same working conditions, a
                representative sample would not accurately characterize actual
                exposures, and individual samples would be necessary.
                c. Section 60.12(c)--Corrective Actions Sampling
                 Under the proposed rule, MSHA would require mine operators to take
                corrective actions when any sampling shows exposures above the proposed
                PEL. After such corrective actions, proposed Sec. 60.12(c) would
                require mine operators to conduct corrective actions sampling to
                determine whether the control measures taken under proposed Sec. 60.13
                have reduced miner exposures to respirable crystalline silica to at or
                below the proposed PEL. If not, the mine operator would be required to
                take additional or new corrective actions until subsequent corrective
                actions sampling indicates miner exposures are at or below the proposed
                PEL.
                 Once corrective actions sampling indicates that miner exposures
                have been lowered to levels at or below the proposed PEL, one of two
                scenarios could occur. First, if corrective actions sampling taken
                under proposed Sec. 60.12(c) indicate that miner exposures are at or
                below the proposed PEL, but at or above the proposed action level, the
                mine operator would be required to conduct periodic sampling as
                described in proposed Sec. 60.12(b). The periodic sampling
                requirements would require mine operators to continue to conduct
                sampling every three months until two consecutive sampling results
                indicate miners' exposures are below the action level. Second, if
                corrective actions sampling taken under proposed Sec. 60.12(c)
                indicate that miner exposures are below the proposed action level, the
                mine operator would be required to conduct a subsequent sample within 3
                months as described in proposed Sec. 60.12(b); if those results show
                miners' exposures are below the action level, the mine operator could
                discontinue periodic sampling.
                 Sampling after corrective actions would provide operators with
                specific information regarding the effectiveness of the corrective
                actions for the mine environment and provide additional data for use in
                making decisions about updating or improving controls. It would also
                provide mine operators with an updated profile of miners' exposures
                against which future samples could be compared.
                d. Section 60.12(d) and (e)--Semi-Annual Evaluation and Post-Evaluation
                Sampling
                 Historically, MSHA has recognized the importance of qualitatively
                evaluating changes in mining conditions and processes and assessing the
                effect of those changes on exposure risk. Operators have general
                experience with these types of evaluations. The proposed rule would
                require mine operators to qualitatively evaluate any changes in
                production, processes, engineering controls, personnel, administrative
                controls, or other factors including geological characteristics that
                might result in new or increased respirable crystalline silica
                exposures, beginning 18 months after the effective date and every 6
                months thereafter. Such evaluations could identify changes in miners'
                exposures to respirable crystalline silica.
                 The proposed semi-annual evaluation, and post-evaluation sampling,
                as appropriate, would help confirm that the results of baseline and
                periodic sampling continue to accurately represent current exposure
                conditions. These proposed semi-annual evaluation and sampling
                requirements would also enable mine operators to take appropriate
                actions to protect exposed miners, such as implementing new or
                additional engineering controls, and would provide information to
                miners and their representatives, as necessary. An evaluation could
                identify a change in operation processes or control measures that might
                lead to increased exposures to respirable crystalline silica which need
                to be corrected. Under proposed paragraph (d)(1), the mine operator
                would be required to make a record of the evaluation, including the
                date of the evaluation. Under proposed paragraph (d)(2), the mine
                operator would be required to post the record on the mine bulletin
                board, and, if applicable, make the evaluation available
                electronically, for the next 31 days.
                 Once the evaluation is complete, a mine operator would be required
                to conduct post-evaluation sampling under proposed Sec. 60.12(e) when
                the results of the evaluation show that miners may be exposed at or
                above the action level. Post-evaluation sampling would provide
                operators with information on whether existing controls are effective,
                whether additional control measures are needed, and whether respiratory
                protection is appropriate. When post-evaluation samples indicate that
                miner exposures are at or above the proposed action level, the mine
                operator would be required to conduct periodic sampling as described in
                proposed paragraph (b). Post-evaluation sampling, however, would not be
                required if the mine operator determines that mining conditions would
                not reasonably be expected to result in exposures at or above the
                action level.
                e. Section 60.12(f)--Sampling Requirements
                 Knowledge of typical respirable dust exposure levels is critical to
                protect the health of miners. The proposed rule includes certain
                sampling requirements that would ensure mine operators'
                [[Page 44908]]
                respirable crystalline silica monitoring is representative of miners'
                actual exposures.
                (1) Typical Mining Activities and Sampling Device Placement
                 Proposed paragraph (f)(1) would require mine operators to collect a
                respirable dust sample for the duration of a miner's regular full shift
                and during typical mining activities. Many potential sources of
                respirable crystalline silica are present only when the mine is
                operating under typical conditions. If a sample is not taken during
                typical mining activities, the actual risk to the miner may not be
                known. This proposed requirement would ensure that respirable
                crystalline silica exposure data accurately reflect actual levels of
                respirable crystalline silica exposure at miners' normal or regular
                workplaces throughout their typical workday, even if there are
                fluctuations in airborne contaminant concentrations during a work
                shift. As discussed in other sections of this preamble, the sample
                results from the full shift would be calculated as an 8-hour TWA
                concentration for comparison with the proposed action level and PEL and
                for compliance determinations.
                 This proposed provision is consistent with existing standards and
                with generally accepted industrial hygiene principles, which recommend
                taking into consideration the entire duration of time a miner is
                exposed to an airborne contaminant, even if it exceeds 8 hours. Based
                on Agency data and experience, MSHA anticipates that operators would
                not have major challenges in meeting these sampling requirements.
                 This proposal would continue existing procedures for sampling
                device placement during sampling. Under proposed Sec. 60.12(f)(2)(i),
                for MNM miners the regular full-shift, 8-hour TWA exposure would be
                based on personal breathing-zone air samples. A breathing zone sample
                is an individual sample that characterizes a miner's exposure to
                respirable crystalline silica during an entire work shift. More
                specifically, the sampler remains with the miner for the entire shift,
                regardless of the task or occupation performed.
                 For coal miners, under proposed Sec. 60.12(f)(2)(ii), the regular
                full-shift, 8-hour TWA exposure would be based on an occupational
                environmental sample collected in compliance with existing standards
                found in Sec. Sec. 70.201(c), 71.201(b), and 90.201(b). Under the
                existing standards, the sampling device would be worn or carried
                ``portal-to-portal,'' meaning from the time the miner enters the mine
                until the miner exits the mine. The sampling device would remain with
                the miner during the entire shift. For shifts that exceed 12 hours, the
                operator would be required to switch the sampling pump prior to the
                13th-hour of operation. However, except in the case of Part 90 miners,
                if a miner who is being sampled changes positions or duties, the
                sampling device would remain with the position or duty chosen for
                sampling (rather than the miner). For Part 90 miners, the sampling
                device would be operated portal-to-portal and would remain operational
                with the miner throughout the Part 90 miner's entire shift, which would
                include the time spent performing normal work duties and the time spent
                traveling to and from the assigned work location.
                (2) Representative Sampling
                 Under the proposed rule, mine operators must accurately
                characterize miners' exposure to respirable crystalline silica. In some
                cases, this would require sampling all exposed miners. In other cases,
                as proposed in paragraph (f)(3), sampling a ``representative'' fraction
                of miners would be sufficient. Where several miners perform the same
                tasks on the same shift and in the same work area, the mine operator
                could sample a representative fraction of miners. Under this proposed
                rule, a representative fraction of miners would consist of two or more
                miners performing the same tasks on the same shift and in the same work
                area and who are expected to have the highest exposures of all the
                miners in an area. For example, sampling a representative fraction may
                involve monitoring the exposure of those miners who are closest to the
                dust source. The sampling results for these miners would then be
                attributed to the remaining miners in the group. When miners are not
                performing the same job under the same working conditions, a
                representative sample would not be sufficient to characterize actual
                exposures, and therefore individual samples would be necessary.
                 MSHA has determined that requiring operators to sample at least two
                miners as representative, where they perform the same tasks on the same
                shift and in the same work area as the remaining miners, would be
                sufficient to ensure that exposures are accurately characterized and
                health protections are provided. This representative sampling provision
                of the proposal is similar to the approach that OSHA uses for both
                general industry (29 CFR 1910.1053(d)(3)) and construction (29 CFR
                1926.1153(d)(2)) under the scheduled sampling options.
                (3) Sampling Devices
                 Respirable dust sampling assesses the ambient air quality in mines
                and evaluates miners' exposure to airborne contaminants. Respirable
                dust comprises particles small enough that, when inhaled, can reach the
                gas exchange region of the lung. Measurement of respirable dust
                exposure is based on the collection efficiency of the human respiratory
                system and the separation of airborne particles by size to assess their
                respirable fraction. Proposed paragraph (f)(4) would require mine
                operators to use sampling devices designed to meet the characteristics
                for respirable-particle-size-selective samplers that conform to the ISO
                7708:1995, ``Air Quality--Particle Size Fraction Definitions for
                Health-Related Sampling,'' Edition 1, 1995-04 to determine compliance
                with the proposed respirable crystalline silica action level and PEL.
                MSHA proposes to incorporate by reference ISO 7708:1995, which is the
                international consensus standard that defines sampling conventions for
                particle size fractions used in assessing possible health effects of
                airborne particles in the workplace and ambient environment. Mine
                operators could use any type of sampling device they wish for
                respirable crystalline silica sampling, as long as it is designed to
                meet the characteristics for respirable-particle-size-selective
                samplers that conform to the ISO 7708:1995 standard and, where
                appropriate, meets MSHA permissibility requirements.\31\
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                 \31\ MSHA's permissibility requirements are specified in 30 CFR
                parts 18 and 74. Part 18, Electric Motor-Driven Mine Equipment and
                Accessories, specifies the procedures and requirements for obtaining
                MSHA approval, certification, extension, or acceptance of electrical
                equipment intended for use in gassy mines. Part 74, Coal Mine Dust
                Sampling Devices, specifies the requirements for evaluation and
                testing for permissibility of coal mine dust sampling devices.
                ---------------------------------------------------------------------------
                 Sampling devices, such as cyclones \32\ and elutriators,\33\ can
                separate the
                [[Page 44909]]
                respirable fraction of airborne dust from the non-respirable fraction
                in a manner that simulates the size-selective characteristics of the
                human respiratory tract and that meets the ISO standard. These devices
                enable collection of dust samples that contain only particles small
                enough to penetrate deep into the lungs. Size-selective cyclone
                sampling devices are typically used in the U.S. mining industry. These
                samplers generally consist of a pump, a cyclone, and a membrane filter.
                The cyclone uses a rapid vortical flow of air inside a cylindrical or
                conical chamber to separate airborne particles according to their
                aerodynamic diameter (i.e., particle size). As air enters the cyclone,
                the larger particles are centrifugally separated and fall into a grit
                pot, while smaller particles pass into a sampling cassette where they
                are captured by a filter membrane that is later analyzed in a
                laboratory to determine the mass of the respirable dust collected. The
                pump creates and regulates the flow rate of incoming air. As the flow
                rate of air increases, a greater percentage of larger and higher-mass
                particles are removed from the airstream, and smaller particles are
                collected with greater efficiency. Adjustment of the flow rate changes
                the particle collection characteristics of the sampler and allows
                calibration to a specified respirable particle size sampling
                definition, such as the ISO criterion.
                ---------------------------------------------------------------------------
                 \32\ A cyclone is a centrifugal device used for extracting
                particulates from carrier gases (e.g., air). It consists of a
                conically shaped vessel. The particulate-containing gas is drawn
                tangentially into the base of the cone, takes a helical route toward
                the apex, where the gas turns sharply back along the axis, and is
                withdrawn axially through the base. The device is a classifier in
                which only dust with terminal velocity less than a given value can
                pass through the formed vortex and out with the gas. The particle
                cut-off diameter is calculable for given conditions.
                 \33\ An elutriator is a device that separates particles based on
                their size, shape, and density, using a stream of gas or liquid
                flowing in a direction usually opposite to the direction of
                sedimentation. The smaller or lighter particles rise to the top
                (overflow) because their terminal sedimentation velocities are lower
                than the velocity of the rising fluid.
                ---------------------------------------------------------------------------
                 MSHA and many mine operators use cyclone samplers. A cyclone
                sampler calibrated to operate at the manufacturer's specified air flow
                rate that conforms to the ISO standard can be used to collect
                respirable crystalline silica samples under this proposed rule. MSHA
                reviewed OSHA's feasibility analysis for its 2016 silica final rule and
                agrees with OSHA that there are commercially available cyclone samplers
                that conform to the ISO standard and allow for the accurate and precise
                measurement of respirable crystalline silica at concentrations below
                both the proposed action level and PEL (OSHA 2016a) Such cyclone
                samplers include the Dorr-Oliver 10-mm nylon cyclone used by MSHA and
                many mine operators, as well as the Higgins-Dewell, GK2.69, SIMPEDS,
                and SKC aluminum cyclone. Each of these cyclones has different
                operating specifications, including flow rates, and performance
                criteria, but all are compliant with the ISO criteria for respirable
                dust with an acceptable level of measurement bias. MSHA's preliminary
                determination is that cyclone samplers, when used at the appropriate
                flow rates, can collect a sufficient mass of respirable crystalline
                silica to quantify atmospheric concentrations lower than the proposed
                action level and would meet MSHA's crystalline silica sample analysis
                specifications for samples collected at MNM and coal mines.
                 MNM mine operators who currently use a Dorr-Oliver 10 mm nylon
                cyclone could continue to use these samplers at a flow rate of 1.7 L/
                min, which conforms to the ISO standard, to comply with the proposed
                requirements. For coal mine operators, the gravimetric samplers
                previously used to sample RCMD (i.e., coal mine dust personal sampling
                units (CMDPSUs)) were operated at a 2.0 L/min flow rate. Those CMDPSUs
                could be adjusted to operate at a flow rate of 1.7 L/min to conform to
                the ISO standard.
                 NIOSH's rapid field-based quartz monitoring (RQM) approach is an
                emerging technology. It provides a field-based method for providing
                respirable crystalline silica exposure measurements at the end of a
                miner's shift. With such an end-of-shift analysis, mine operators can
                identify overexposures and mitigate hazards more quickly. NIOSH
                Information Circular 9533, ``Direct-on-filter Analysis for Respirable
                Crystalline Silica Using a Portable FTIR Instrument'' provides detailed
                guidance on how to implement a field-based end-of-shift respirable
                crystalline silica monitoring program.\34\ The current RQM monitor,
                however, was designed as an engineering tool; it is not currently
                designed as a compliance tool with tamper-proof components and is
                susceptible to interferences which can affect its accuracy. This means
                that the integrity of the sample cannot be guaranteed, and therefore
                the monitor cannot be used as a compliance tool. MSHA continues to
                support NIOSH efforts to develop the RQM monitor for use in mines.
                ---------------------------------------------------------------------------
                 \34\ National Institute for Occupational Safety and Health
                (NIOSH). Direct-on-filter analysis for respirable crystalline silica
                using a portable FTIR instrument. By Chubb LG, Cauda EG. Pittsburgh
                PA: U.S. Department of Health and Human Services, Centers for
                Disease Control and Prevention, National Institute for Occupational
                Safety and Health, DHHS (NIOSH) Publication No. 2022-108, IC 9533.
                https://doi.org/10.26616/NIOSHPUB2022108. The document is intended
                for industrial hygienists and other health and safety mining
                professionals who are familiar with respirable crystalline silica
                exposure assessment techniques, but who are not necessarily trained
                in analytical techniques. It gives general instructions for setting
                up the field-based monitoring equipment and software. It also
                provides case studies and examples of different types of samplers
                that can be used for respirable crystalline silica monitoring.
                Guidance on the use, storage, and maintenance of portable IR
                instruments is also provided in the document.
                ---------------------------------------------------------------------------
                f. Section 60.12 (g)--Methods of Sample Analysis.
                 Proposed paragraph (g) specifies the methods to be used for
                analysis of respirable crystalline silica samples, including details
                regarding the specific analytical methods to be used and the
                qualifications of the laboratories where the samples are analyzed.
                Proposed paragraph (g)(1) would require mine operators to use
                laboratories that are accredited to the International Organization for
                Standardization (ISO) or International Electrotechnical Commission
                (IEC) (ISO/IEC) 17025, ``General requirements for the competence of
                testing and calibration laboratories'' with respect to respirable
                crystalline silica analyses, where the accreditation has been issued by
                a body that is compliant with ISO/IEC 17011 ``Conformity assessment--
                Requirements for accreditation bodies accrediting conformity assessment
                bodies.'' Accredited laboratories are held to internationally
                recognized laboratory standards and must participate in quarterly
                proficiency testing for all analyses within the scope of the
                accreditation.
                 The ISO/IEC 17025 standard is a consensus standard developed by the
                International Organization for Standardization and the International
                Electrotechnical Commission (ISO/IEC) and approved by ASTM
                International (formerly the American Society for Testing and
                Materials). This standard establishes criteria by which laboratories
                can demonstrate proficiency in conducting laboratory analysis through
                the implementation of quality control measures. To demonstrate
                competence, laboratories must implement a quality control program that
                evaluates analytical uncertainty and provides estimates of sampling and
                analytical error when reporting samples. The ISO/IEC 17011 standard
                establishes criteria for organizations that accredit laboratories under
                the ISO/IEC 17025 standard. For example, the American Industrial
                Hygiene Association (AIHA) accredits laboratories for proficiency in
                the analysis of respirable crystalline silica using criteria based on
                the ISO 17025 and other criteria appropriate for the scope of the
                accreditation.
                 Many MNM mine operators currently use third-party laboratories to
                perform respirable crystalline silica sample analyses, and under the
                proposed standard, MSHA anticipates that they would continue to use
                third-party laboratories.
                 For most coal mine operators, using a third-party accredited
                laboratory to
                [[Page 44910]]
                analyze respirable crystalline silica samples would be a new
                requirement because respirable coal mine dust samples are currently
                analyzed only by MSHA. Under the proposed standard, all mine operators
                would have to use third-party laboratories accredited to ISO/IEC 17025
                to have respirable dust samples analyzed for respirable crystalline
                silica. By requiring all mines to use third-party laboratories,
                proposed paragraph (g)(1) would ensure that sample analysis
                requirements and MSHA enforcement efforts are consistent across all
                mines.
                 Proposed paragraph (g)(2) would require mine operators to ensure
                that laboratories evaluate all samples using analytical methods for
                respirable crystalline silica that are specified by MSHA, NIOSH, or
                OSHA. These are validated methods currently being cited by third party
                accredited labs for measuring respirable crystalline silica in mine
                dust matrices. MSHA and NIOSH have specific FTIR methods for analyzing
                quartz in coal mine dust. The NIOSH 7603 method is based on the MSHA P-
                7 method which was collaboratively tested and specifically addresses
                the interference from kaolinite clay. All three methods, MSHA P-2,
                NIOSH 7500, and OSHA ID-142 for analyzing respirable crystalline silica
                using X-ray diffraction (XRD) have similar procedures for measuring
                respirable crystalline silica and are capable of distinguishing between
                the three silica polymorphs. Additional steps such as acid treatment
                can be taken to remove respirable crystalline silica interferences from
                other minerals that can be found in mine dust sample matrices.
                Consistent with MSHA's current practices for the analysis of respirable
                crystalline silica samples, analytical techniques used for samples from
                MNM mines and coal mines would generally be different due to potential
                sources of interference and cost considerations. Under the proposed
                rule, as discussed below, MSHA expects that samples collected in MNM
                mines would continue to be analyzed by X-ray diffraction (XRD) and
                samples collected for coal mines would continue to be analyzed by
                Fourier transform infrared spectroscopy (FTIR).
                 Coal mine samples are currently analyzed using the FTIR method
                because it is cheaper, faster, and better suited for the coal mining
                sector, where samples contain little or no minerals that could
                interfere or confound respirable crystalline silica analysis results.
                Current FTIR methods, however, cannot quantify quartz if either of the
                other two forms of crystalline silica (cristobalite and tridymite) are
                present in the sample. Unlike coal dust samples, MNM samples may have a
                variety of minerals present, which could cause interference with
                respirable crystalline silica measurements if FTIR were used. Thus, MNM
                samples are currently analyzed by XRD because the XRD method can
                distinguish and isolate respirable crystalline silica for measurement,
                thereby avoiding interference or confounding of respirable crystalline
                silica analysis results. The XRD method could be used for both MNM and
                coal samples but using the XRD method is more time consuming and more
                costly, with no additional benefit for coal mine sample analysis. For
                this reason, MSHA does not expect the use of XRD on samples from coal
                mines.
                 For MNM samples, the methods used for respirable crystalline silica
                sample analysis using XRD include MSHA P-2, NIOSH 7500, and OSHA ID-
                142. For coal samples, the methods used for respirable crystalline
                silica sample analysis using FTIR include MSHA P-7, NIOSH 7602, and
                NIOSH 7603. (OSHA does not currently have an established FTIR method
                for analysis of respirable crystalline silica.)
                g. Section 60.12 (h)--Sampling Records
                 Proposed paragraph (h) would establish requirements for sampling
                records, including what mine operators would be required to do after
                receiving the analytical reports from laboratories. For each sample
                taken, this proposed paragraph would require mine operators to create a
                record that includes the sample date, the sampled occupations, and the
                reported concentrations of both respirable dust and respirable
                crystalline silica. After making such a record, the mine operator would
                be required to post the record, together with the laboratory report, on
                the mine bulletin board and, if applicable, make the record and the
                laboratory report available electronically, for the next 31 days upon
                receipt.
                 When electronic means are available, mine operators would be
                required to use those electronics means such as electronic bulletin
                boards or newsletters, in addition to physically posting the sampling
                record and laboratory report on the mine bulletin board. MSHA believes
                that most mines have the ability to display this information
                electronically. For any mines where electronic means are not available,
                mine operators would only be required to physically post the sampling
                record and laboratory report on the mine bulletin board. Also, as
                required in proposed Sec. 60.16(b), the sampling records created under
                this section may be requested at any time by, and must promptly be made
                available to, miners, authorized representatives of miners, or an
                authorized representative of the Secretary.
                 MSHA believes that the posted information including sampling
                results and methodology and other relevant information would inform
                miners of the sampled exposures and would encourage them to have
                heightened awareness of potential health hazards that could impact not
                only them but other miners. It would also provide them with knowledge
                to take proactive actions to protect themselves and fellow miners
                through better and safer work practices and more active participation
                in health and safety programs. This is consistent with the Mine Act
                which states that mine operators, with the assistance of miners, have
                the responsibility to prevent the existence of unsafe and unhealthful
                conditions and practices in mines. 30 U.S.C. 801(e). Making miners
                aware that respirable crystalline silica exposures below the PEL may
                still pose a health risk could encourage them to take steps to manage
                their health risks.
                6. Section 60.13--Corrective Actions
                 This proposed section includes several actions a mine operator
                would be required to take to protect miners' health and safety when any
                sampling result indicates that a miner's exposure to respirable
                crystalline silica exceeds the proposed PEL. Proposed paragraph (a)(1)
                would require the mine operator to make NIOSH-approved respirators
                available to affected miners before the start of the next work shift.
                Proposed paragraph (a)(2) would require mine operators to ensure that
                affected miners wear respirators for the full shift or during the
                period of overexposure to protect miners until miner exposures are at
                or below the PEL.
                 Proposed paragraph (a)(3) would require operators to take immediate
                corrective actions to lower the concentration of respirable crystalline
                silica to levels at or below the PEL. Some examples of corrective
                actions include increasing air ventilation and/or water flow rates,
                adding more water sprays, and improving maintenance of the existing
                engineering controls.
                 Once corrective actions have been taken, proposed paragraph
                (a)(4)(i) would require the operator to conduct sampling in accordance
                with Sec. 60.12(c) to determine if the corrective actions have been
                successful in lowering exposures to at or below the PEL. If sampling
                indicates that the corrective actions did not reduce miner exposures to
                at or below the PEL, proposed
                [[Page 44911]]
                paragraph (a)(4)(ii) would require the operator to implement additional
                or new corrective actions until sampling indicates miner exposures are
                at or below the PEL.
                 Proposed Sec. 60.13(b) would require the mine operator to make a
                record of corrective actions required under proposed paragraph (a) of
                this section and the dates of those actions. These records would help
                the operator and MSHA identify whether existing controls are effective,
                or whether maintenance or additional control measures are needed.
                7. Section 60.14--Respiratory Protection
                 This proposed provision addresses the use of respiratory protection
                equipment. As noted earlier, the use of respiratory protection
                equipment, including powered air-purifying respirators (PAPRs), would
                not be permitted as a control to achieve compliance with the proposed
                PEL because engineering controls are more effective than respirators in
                protecting miners. However, temporary non-routine use of respirators
                would be allowed under limited circumstances.
                 Proposed paragraph (a) would require the mine operator to provide
                respirators to miners as a temporary measure in accordance with
                proposed paragraph (c) of this section, when miners are working in
                concentrations of respirable crystalline silica above the PEL under
                specific, limited circumstances. Proposed paragraph (a)(1) would
                require the temporary use of respirators when miners' exposures exceed
                the proposed PEL during the development and implementation of
                engineering controls.
                 Proposed paragraph (a)(2) would require the use of respirators for
                temporary, nonroutine work to prevent miners' exposures at levels above
                the proposed PEL. Examples include when a miner is mixing cement to
                build a stopping to separate a main intake from return airways or is
                engaged in an unplanned entry into an atmosphere with excessive
                respirable crystalline silica concentrations to perform a repair or
                investigation that must occur before feasible engineering or
                administrative controls can be implemented.
                 The proposal is consistent with NIOSH's recommendation in the 1995
                Criteria Document (NIOSH 1995a) and is similar to the existing
                standards for MNM and coal mines. NIOSH (1995a) recommended the use of
                respirators as an interim measure when engineering controls and work
                practices are not effective in maintaining worker exposures for
                respirable crystalline silica at or below the proposed PEL.
                 MSHA's existing MNM standards in parts 56 and 57 permit mine
                operators to allow miners to work for reasonable periods of time
                protected by appropriate respiratory protection in locations where
                concentrations of contaminants (including respirable crystalline
                silica) exceed permissible levels and where feasible engineering
                control measures have not been developed or where necessary by the
                nature of the work involved (e.g., occasional entry into hazardous
                atmospheres to perform maintenance or investigation). MSHA's existing
                standards for respirable coal mine dust require the mine operator to
                make respiratory protection equipment available while the operator
                evaluates and implements engineering control measures when a valid
                sample meets or exceeds the applicable standard during operator
                exposure monitoring. (30 CFR 70.208(e)(1); 30 CFR 71.206(h)(1); 30 CFR
                72.700-72.701; 30 CFR 90.207(c)(1)).
                 Proposed paragraph (b) addresses situations where miners are not
                able to wear a respirator while working. Proposed paragraph (b) would
                require the mine operator, upon written notification by a PLHCP, to
                transfer an affected miner who is unable to wear a respirator to work
                in another area of the same mine, or to another occupation at the same
                mine, where respiratory protection is not required.
                 The operator must ensure that the occupation and the area of the
                mine to which the miner is temporarily transferred do not expose the
                miner to respirable crystalline silica above the proposed PEL. Proposed
                paragraph (b)(1) would require the mine operator to continue to
                compensate the affected miner at no less than the regular rate of pay
                in the occupation held by that miner immediately prior to the transfer.
                Under proposed paragraph (b)(2), the miner may be transferred back to
                the initial work area or occupation when the temporary, non-routine use
                of respirators is no longer required.
                 MSHA believes that this proposed provision is consistent with the
                mandate in the Mine Act to provide the maximum health protection for
                miners. Also, any effect on miners by this provision should be
                temporary since the concentration of respirable crystalline silica to
                which the miner would be exposed must be controlled through feasible
                engineering and administrative controls on a long-term basis.
                 Proposed paragraph (c) includes the respiratory protection
                requirements that an operator must address when providing respirators
                to miners. Proposed paragraph (c)(1), like the existing standards in
                parts 56, 57, and 72, would require mine operators to provide
                respiratory protection equipment approved by NIOSH under 42 CFR part
                84. Whenever respirators are used by miners, proposed paragraph (c)(1)
                would require the mine operator to provide miners with NIOSH-approved
                atmosphere-supplying respirators or air-purifying respirators.
                Atmosphere-supplying respirators provide clean breathing air from a
                separate source (e.g., a self-contained air tank), whereas air-
                purifying respirators use filters, cartridges, or canisters to remove
                contaminants from the air.
                 In mines, commonly used types of air-purifying respirators include
                elastomeric respirators, filtering facepiece respirators (FFRs), and
                PAPRs. Elastomeric respirators, such as half-facepiece or full-
                facepiece tight-fitting respirators, are made of synthetic or natural
                rubber material and can be cleaned, disinfected, stored, and repeatedly
                re-used. FFRs (i.e., dust masks), designed to cover areas of the
                wearer's face from the bridge of the nose to the chin, are disposable
                respirators composed of a weave of electrostatically charged synthetic
                filter fibers and an elastic head strap. PAPRs utilize a blower to move
                ambient air through an air-purifying filter that removes particulates
                and delivers clean air to the wearer. When air-purifying respirators
                (elastomeric respirators, FFRs, and PAPRs) are used, under proposed
                paragraph (c)(1), the mine operator would be required to select only
                high-efficiency NIOSH-certified particulate protection (i.e., 100
                series or HE filters) for respirable crystalline silica protection. A
                100 series and high efficiency filter means that the filter must
                demonstrate a minimum efficiency level of 99.97 percent (i.e., the
                filter is at least 99.97 percent efficient in removing particles of 0.3
                [micro]m aerodynamic mass median diameter).
                 Under proposed paragraphs (c)(1)(i) through (c)(1)(ii), air-
                purifying respirators would be required to be equipped with one of the
                following three particulate protection types: (1) particulate
                protection defined as a 100 series under 42 CFR part 84; or (2)
                particulate protection defined as High Efficiency ``HE'' under 42 CFR
                part 84. MSHA believes that air-purifying respirators with the highest
                efficiency NIOSH classifications for particulate protection are most
                suitable in protecting miners from occupational exposure to a
                carcinogen such as respirable crystalline silica.
                 Proposed paragraph (c)(2) would require mine operators to follow
                the provisions, as applicable, of ASTM F3387-19, ``Standard Practice
                for
                [[Page 44912]]
                Respiratory Protection,'' when respiratory protection equipment is
                needed. Under the proposal, MSHA would require that the respiratory
                program would be in writing and would include the following minimally
                acceptable program elements: program administration; standard operating
                procedures; medical evaluations; respirator selection; training; fit
                testing; and maintenance, inspection, and storage. Beyond the minimally
                acceptable program elements, mine operators would be allowed to comply
                with the provisions of the 2019 ASTM standard that they deem
                applicable. The need for temporary non-routine use of respirators may
                vary, given the variability of mining processes, activities, and
                commodities that are mined. MSHA believes that flexibility afforded to
                mine operators under this paragraph may lead mine operators to focus
                more appropriately on those provisions that are relevant to their mine-
                specific situations, allowing them to comply more efficiently and
                effectively.
                 ASTM F3387-19 is a voluntary consensus standard published by ASTM
                International and was approved in 2019. MSHA proposes to incorporate by
                reference this consensus standard for two reasons.
                 First, adopting this voluntary consensus standard is consistent
                with OMB Circular A-119, which encourages Federal agencies to
                ``minimize reliance on government-unique standards where an existing
                standard would meet the Federal government's objective.'' ASTM F3387-19
                comprehensively addresses all aspects of establishing, implementing,
                and evaluating respiratory protection programs, and describes
                respiratory protection program elements which include: program
                administration; standard operating procedures; medical evaluation;
                respirator selection; training; fit testing; and respirator
                maintenance, inspection, and storage.
                 Second, ASTM F3387-19 reflects current respirator technology and an
                up-to-date understanding of effective respiratory protection. For
                example, ASTM F3387-19 provides detailed information on respirator
                selection that are based on NIOSH's long-standing experience of testing
                and approving respirators for occupational use and OSHA's research and
                rulemaking on respiratory protection.
                 More detailed discussion on ASTM F3387-19 is provided later in C.
                Updating MSHA Respiratory Protection Standards: Proposed Incorporation
                of ASTM F3387-19 by Reference.
                8. Section 60.15--Medical Surveillance for Metal and Nonmetal Miners
                 This proposed provision would require MNM mine operators to provide
                mandatory medical examinations to miners who begin in the mining
                industry after the effective date of the rule and offer voluntary
                periodic examinations to all other miners. These medical examinations
                would be provided by a PLHCP or specialist. The proposed requirements
                in this section are consistent with the Mine Act's mandate to provide
                maximum health protection for miners and provide MNM miners with
                information needed for early detection of respirable crystalline
                silica-related disease, resulting in prevention of disabling disease.
                 The proposed requirements for MNM mine operators are also generally
                consistent with existing medical surveillance requirements for coal
                mine operators under 30 CFR 72.100 although the requirements differ in
                some respects. For example, the proposed provision specifies that
                medical examinations must be provided by a PLHCP or specialist, while
                the existing medical surveillance requirements for coal miners in Sec.
                72.100 coordinate with the surveillance system managed by NIOSH's Coal
                Workers' Health Surveillance Program (CWHSP) which works with coal mine
                operators under NIOSH regulations to provide medical surveillance.
                Proposed paragraph 60.15(a) would require that each MNM mine operator
                make medical examinations available to each MNM miner, at no cost to
                the miner, regardless of whether miners are reasonably expected to be
                exposed to any level of respirable crystalline silica. This proposed
                requirement is consistent with section 101(a)(7) of the Mine Act.
                 Proposed paragraph 60.15(a) would also require medical examinations
                to be performed by a PLHCP or specialist. A PLHCP is an individual
                whose legally permitted scope of practice (i.e., license, registration,
                or certification) allows that individual to independently provide or be
                delegated the responsibility to provide some or all of the required
                health services (i.e., chest X-rays, spirometry, symptom assessment,
                and occupational history). A specialist, as defined in proposed Sec.
                60.2, refers to an American Board-certified specialist in pulmonary
                disease or occupational medicine. The Agency believes it is appropriate
                to allow not only a physician, but also any State-licensed health care
                professional, to perform the required medical examinations. This would
                provide operators with the flexibility needed to use professionals with
                necessary medical skills and minimize cost and compliance burdens.
                 Proposed paragraph (a)(1) requires periodic examinations to be
                offered to all MNM miners at the frequencies specified in this section.
                Proposed paragraph (a)(2) specifies the types of medical examinations
                and is consistent with the existing requirements for coal mine
                operators under existing Sec. 72.100.
                 Proposed paragraphs (a)(2)(i) and (ii) would require MNM operators
                to provide each miner with a medical examination that includes a review
                of the miner's medical and work history and a physical examination. The
                medical and work history would cover a miner's present and past work
                exposures, illnesses, and any symptoms indicating respirable
                crystalline silica-related diseases and compromised lung function. The
                medical and work history should focus not only on any history of
                tuberculosis, smoking, or exposure to respirable crystalline silica,
                but also on any diagnoses and symptoms of respiratory system
                dysfunction, including shortness of breath, coughing, or wheezing. The
                physical examination under (a)(2)(ii) would be focused on the
                respiratory tract. For the reasons stated above, these proposed
                requirements differ from the existing requirements for coal miners. The
                existing medical surveillance requirements for coal miners in 42 CFR 37
                specify standardized data collection elements for occupational
                histories and respiratory symptom assessment while proposed paragraphs
                (a)(2)(i) and (ii) specify a respiratory-focused history and physical
                examination by a clinician.
                 Under proposed paragraph (a)(2)(iii), MSHA would require all
                medical examinations to include a chest X-ray. The required chest X-ray
                is a posterior/anterior view no less than 14 x 17 inches and no more
                than 16 x 17 inches at full inspiration, recorded on either film or
                digital radiography systems. The chest X-ray must be classified by a
                NIOSH-certified B Reader, in accordance with the Guidelines for the Use
                of the International Labour Office (ILO) International Classification
                of Radiographs of Pneumoconioses. The ILO recently made additional
                standard digital radiographic images available and has published
                guidelines on the classification of digital radiographic images (ILO
                2022). This is a standard practice in pneumoconiosis surveillance
                programs and can potentially detect other respirable crystalline
                silica-related conditions, including lung cancer (Industrial Minerals
                Association-North America and Mine Safety and Health Administration,
                2008). The test would provide data that can be used to assess
                [[Page 44913]]
                for progression of silicosis and for other respirable crystalline
                silica-related conditions in MNM miners.
                 MSHA preliminarily concludes that the number of B readers in the
                U.S. is adequate to classify chest X-rays conducted as part of the
                respirable crystalline silica rule (OSHA 2016a, 81 FR 16286, 16821). As
                discussed in OSHA's 2016 final silica rule, the number of B Readers is
                driven by supply and demand created by a free market, and many
                physicians choose to become B readers based on demands for such
                services (OSHA 2016a, 81 FR 16286, 16822). NIOSH is also able to train
                enough B readers to handle any potential increase in demand, providing
                several pathways for physicians to become B readers, such as free self-
                study materials by mail or download and free B reader examinations
                (OSHA 2016a, 81 FR 16286, 16822). In addition, courses and examinations
                for certification are periodically offered for a fee through the
                American College of Radiology (OSHA 2016a, 81 FR 16286, 16822). Even if
                B readers are scarce in certain geographical locations, digital X-rays
                can be easily transmitted electronically to B readers located anywhere
                in the U.S. (OSHA 2016a, 81 FR 16286, 16822).
                 Under proposed paragraph (a)(2)(iv), MSHA would require that
                pulmonary function testing (including spirometry) be part of every
                medical examination. The pulmonary function test must be administered
                by a spirometry technician with a current certificate from a NIOSH-
                approved Spirometry Training Sponsorship. The purpose of spirometry is
                to measure baseline lung function followed by periodic tests to detect
                early impairment patterns, such as obstruction of air flow and
                restriction caused by underlying respiratory disease. This measurement
                can provide critical information for the primary, secondary, and
                tertiary prevention of workplace-related lung diseases, including
                respirable crystalline silica-related diseases. The use of spirometry
                is consistent with recommendations of the Dust Advisory Committee (U.S.
                DOL, 1996) and the NIOSH Criteria Document (1974). Indeed, NIOSH
                (2014a) notes that properly conducted spirometry should be part of a
                comprehensive workplace respiratory health program. Spirometry and
                chest X-rays are complementary examinations for detecting adverse
                health effects from respirable crystalline silica exposures.
                 In order to maintain a certificate from a NIOSH-approved course,
                technicians must complete an initial training and then refresher
                training every five years (OSHA 2016a, 81 FR 16286, 16825). As
                discussed in OSHA's 2016 silica final rule, course sponsors are located
                throughout the U.S. and some sponsors will travel to a requested site
                to teach a course (OSHA 2016a, 81 FR 16286, 16825). One NIOSH-approved
                sponsor offers instructor-led live virtual initial training. Several
                live virtual and web-based refresher training options are also
                available. Because the required training is not too frequent and course
                sponsors appear to be widely available throughout the U.S., MSHA
                preliminarily concludes that the requirement that technicians maintain
                a certificate from a NIOSH-approved course will not impose substantial
                burdens on providers of spirometry testing.
                 MSHA believes that the proposed medical examinations consisting of
                a medical and work history, a physical examination, a chest X-ray, and
                a spirometry test would help medical professionals identify early
                symptoms of respirable crystalline silica-related diseases, assist MNM
                miners in protecting their health, and lower the risk that MNM miners
                become materially impaired due to occupational exposure to respirable
                crystalline silica.
                 Under proposed paragraph (b), MSHA would require MNM mine operators
                to provide every miner employed at MNM mines with the opportunity to
                have periodic medical examinations. Miner participation would be
                voluntary, as in the case of the examination requirement for coal
                miners in 30 CFR 72.100(b). Starting on the proposed effective date,
                mine operators must provide the opportunity for an examination to MNM
                miners no later than 5 years after the date of their last medical
                surveillance examination, and in addition, during a 6-month period that
                begins no less than 3.5 years and not more than 4.5 years from the end
                of the last 6-month period for medical examinations. Periodic
                examinations would allow for comparisons with a miner's prior
                examination results, help detect respirable crystalline silica-related
                disease including silicosis, and address further progression of
                existing respiratory disease. If a miner has a positive chest X-ray
                (ILO category of 1/0+), it is important to intervene as promptly as
                possible for maximum health protection. In addition, an interval of 5
                years or less between each miner's periodic examinations can ensure
                detection of declines in a miner's lung function due to potential
                occupational exposure. MSHA believes that the proposed schedule, which
                is consistent with the periodic examination for coal miners required
                under Sec. 72.100(b), would provide MNM mine operators with
                flexibility in offering examinations to miners.
                 Proposed paragraph (c) would require MNM mine operators to provide
                a mandatory initial medical examination for each MNM miner who is new
                to the mining industry. Consequently, if a miner had previous mining
                experience (such as working in a coal mine) and subsequently came to
                work in an MNM mine, MSHA would not require that the MNM mine operator
                provide the miner with an initial examination after the miner begins
                employment. Mandatory initial examinations would be conducted when
                miners are first hired in the mining industry and would provide an
                individual baseline of each miner's health status. This initial
                examination would assist in the early detection of respirable
                crystalline silica-related illnesses and conditions that may make the
                miner more susceptible to the toxic effects of respirable crystalline
                silica. The individual baseline would also be valuable in assessing any
                future health changes in each miner. Overall, the initial examination
                results would enable miners to respond appropriately to information
                about their health status.
                 Proposed paragraph (c)(1) would require that the mandatory initial
                medical examination occur no later than 30 days after a miner new to
                the industry begins employment. Proposed paragraphs (c)(2) and (3)
                would require MNM mine operators to provide mandatory follow-up
                examinations to new miners who were eligible for an initial mandatory
                medical examination under proposed paragraph (c). MSHA believes follow-
                up examinations are important for assessments of any changes in a new
                miner's health status and for future diagnoses.
                 Under proposed paragraph (c)(2), MSHA would require that the mine
                operator provide a mandatory follow-up examination to the miner no
                later than 3 years after the miner's initial medical examination. Under
                proposed paragraph (c)(3), if a miner's 3-year follow-up examination
                shows evidence of a respirable crystalline silica-related disease or
                decreased lung function, the operator would be required to provide the
                miner with another mandatory follow-up examination with a specialist,
                as defined in proposed Sec. 60.2, within 2 years. This proposed
                requirement is intended to ensure that any miner whose follow-up
                medical examination shows evidence of silicosis or evidence of
                decreased lung function, as determined by the PLHCP or specialist, is
                seen by a professional with expertise in respiratory disease. This
                would ensure that miners would benefit from not only expert medical
                judgment but
                [[Page 44914]]
                also counseling regarding work practices and personal habits that could
                affect the miners' health. For the reasons stated above, this proposed
                requirement differs from the existing requirements for coal miners,
                which provides for follow up surveillance testing but does not include
                interaction with a PLHCP or specialist.
                 Proposed paragraph (d) would require that the results of any
                medical examination performed under this section be kept confidential
                and provided only to the miner. The miner is also entitled to request
                that the medical examination results be provided to the miner's
                designated physician. Based on MSHA's experience with coal miners'
                medical surveillance, the Agency believes that confidentiality
                regarding medical conditions is essential and that it encourages miners
                to take advantage of the opportunity to detect early adverse health
                effects due to respirable crystalline silica. See 79 FR 24813, at
                24928, May 1, 2014.
                 Under proposed paragraph (e), MNM mine operators would be required
                to obtain a written medical opinion from a PLHCP or specialist within
                30 days of the medical examination that includes only the date of a
                miner's medical examination, a statement that the examination has met
                the requirements of this section, and any recommended limitations on
                the miner's use of respirators. This would allow the mine operator to
                verify the examination has occurred and would provide the mine operator
                with information on miners' ability to use respirators. Proposed
                paragraph (f) would require the mine operator to maintain a record of
                the written medical opinions obtained from the PLHCP or specialist
                under proposed paragraph (e).
                9. Section 60.16--Recordkeeping Requirements.
                 Section 60.16 lists all the proposed recordkeeping requirements
                under this proposed part. To ensure that mine operators track actual or
                potential exposures, risks, and controls and keep miners, miners'
                representatives, and other stakeholders informed about them, the
                proposed part 60 establishes five recordkeeping requirements.
                Discussion of these requirements follow and are summarized in table 1
                to paragraph (a) in Sec. 60.16 of the rule text.
                 First, this section would require that, once mine operators
                complete the sampling or semi-annual evaluations required under
                proposed Sec. 60.12, the operators retain the associated exposure
                monitoring records for at least 2 years. Examples of exposure
                monitoring records include the date of sampling or evaluation, names
                and occupations of miners who were sampled, description of sampling or
                evaluation method, and laboratory reports of sampling analysis. The 2-
                year period would give mine operators sufficient exposure monitoring
                data to evaluate the effectiveness of their engineering and
                administrative controls over different mining and weather conditions.
                 Second, mine operators would also be required to retain records of
                corrective actions made under proposed Sec. 60.13(b) for at least 2
                years from the date when each corrective action was taken. This
                proposed requirement is similar to the recordkeeping requirements
                related to other corrective-action requirements under parts 56 and 57
                (for MNM mines) and parts 70, 71, and 90 (for coal mines).
                 Third, this proposed section would require mine operators to
                maintain any written determination records that they receive from a
                PLHCP or specialist. When a PLHCP or specialist certifies in writing
                that a miner cannot wear a respirator, including a PAPR, that miner
                must be temporarily transferred to a different work area or task where
                respiratory protection is not required (or needed). In such cases, mine
                operators would be required to retain the written determinations by a
                PLHCP or specialist for the duration of the miner's employment plus 6
                months.
                 Fourth, under this section, MNM mine operators would be required to
                maintain written medical opinion records that they obtain from a PLHCP
                or specialist who conducts medical examinations of their miners under
                proposed Sec. 60.15. This proposed recordkeeping requirement would
                apply only to MNM mine operators. Under proposed Sec. 60.15, after the
                examination has taken place, the MNM mine operator would receive from
                the PLHCP or specialist a written medical opinion that contains the
                date of the medical examination, a statement that the examination has
                met the requirements under this proposed rule, and any recommended
                limitations on the miner's use of respirators. Upon receipt, the mine
                operator would retain the medical opinion for the duration of the
                miner's employment plus 6 months.
                 Proposed paragraph (b) would ensure that all the listed records
                would be made available promptly upon request to miners, authorized
                representatives of miner(s), and authorized representatives of the
                Secretary of Labor.
                10. Section 60.17--Severability
                 The severability clause under proposed Sec. 60.17 serves two
                purposes. First, it expresses MSHA's intent that if any section or
                provision of the Lowering Miners' Exposure to Respirable Crystalline
                Silica and Improving Respiratory Protection rule--including its
                conforming amendments in sections of 30 CFR parts 56, 57, 70, 71, 72,
                75, and 90 that address respirable crystalline silica or respiratory
                protection--is held invalid or unenforceable or is stayed or enjoined
                by any court of competent jurisdiction, the remaining sections or
                provisions should remain effective and operative. Second, the
                severability clause expresses MSHA's judgment, based on its technical
                and scientific expertise, that each individual section and provision of
                the rule can remain effective and operative if some sections or
                provisions are invalidated, stayed, or enjoined. Accordingly, MSHA's
                inclusion of this severability clause addresses the twin concerns of
                Federal courts when determining the propriety of severability:
                identifying agency intent and clarifying that any severance will not
                undercut the structure or function of the rule more broadly. Am. Fuel &
                Petrochem. Mfrrs. v. Env't Prot. Agency, 3 F.4th 373, 384 (D.C. Cir.
                2021) (``Severability `depends on the issuing agency's intent,' and
                severance `is improper if there is substantial doubt that the agency
                would have adopted the severed portion on its own' '') (quoting North
                Carolina v. FERC, 730 F.2d 790, 796 (D.C. Cir. 1984) and New Jersey v.
                Env't Prot. Agency, 517 F.3d 574, 584 (D.C. Cir. 2008)).
                 Under the principle of severability, a reviewing court will
                generally presume that an offending provision of a regulation is
                severable from the remainder of the regulation, so long as that outcome
                appears consistent with the issuing agency's intent, and the remainder
                of the regulation can function independently without the offending
                provision. See K Mart Corp. v. Cartier, Inc., 486 U.S. 281, 294 (1988)
                (invalidating and severing subsection of a regulation where it would
                not impair the function of the statute as a whole and there was no
                indication the regulation would not have been passed but for inclusion
                of the invalidated subsection). Consequently, in the event that a court
                of competent jurisdiction stays, enjoins, or invalidates any provision,
                section, or application of this rule, the remainder of the rule should
                be allowed to take effect.
                B. Conforming Amendments
                 The proposed rule would require conforming amendments in 30 CFR
                parts 56, 57, 70, 71, 72, 75, and 90 based on the proposed new part 60.
                [[Page 44915]]
                1. Part 56--Safety and Health Standards--Surface Metal and Nonmetal
                Mines
                a. Section 56.5001--Exposure Limits for Airborne Contaminants
                 For respirable crystalline silica, proposed part 60 would establish
                exposure limits and other related requirements for all mines. Existing
                paragraph (a) of Sec. 56.5001 governs exposure limits for airborne
                contaminants, except asbestos, for surface MNM mines. MSHA is proposing
                to amend paragraph (a) of Sec. 56.5001 to add respirable crystalline
                silica as an exception. The amended paragraph (a) of Sec. 56.5001
                would govern exposure limits for airborne contaminants other than
                respirable crystalline silica and asbestos for surface MNM mines.
                2. Part 57--Safety and Health Standards--Underground Metal and Nonmetal
                Mines
                a. Section 57.5001--Exposure Limits for Airborne Contaminants
                 Existing paragraph (a) of Sec. 57.5001 governs exposure limits for
                airborne contaminants, except asbestos, for underground MNM mines.
                Similar to the proposed changes discussed above for Sec. 56.5001, MSHA
                is proposing to amend paragraph (a) of Sec. 57.5001 to add respirable
                crystalline silica as an exception. The amended paragraph (a) of Sec.
                57.5001 would govern exposure limits for airborne contaminants other
                than respirable crystalline silica and asbestos for underground MNM
                mines.
                3. Part 70--Mandatory Health Standards--Underground Coal Mines
                a. Section 70.2--Definitions.
                 MSHA proposes to remove the Quartz definition in Sec. 70.2. With
                the adoption of an independent respirable crystalline silica standard
                in proposed part 60, the Agency is proposing to remove RCMD when quartz
                is present in Sec. 70.101 and the term quartz would no longer appear
                in part 70.
                b. Section 70.101--Respirable Dust Standard When Quartz Is Present
                 MSHA is proposing to remove the entire section and reserve the
                section number. The RCMD when quartz is present in Sec. 70.101 would
                no longer be needed because MSHA is proposing an independent respirable
                crystalline silica standard in proposed part 60.
                 MSHA's proposed independent standard for respirable crystalline
                silica would result in miners' exposure to respirable crystalline
                silica no longer being controlled indirectly by reducing respirable
                dust. NIOSH, the Secretary of Labor's Advisory Committee on the
                Elimination of Pneumoconiosis Among Coal Mine Workers (Dust Advisory
                Committee), and the Department of Labor's Inspector General \35\ have
                each recommended the adoption of an independent standard for respirable
                quartz exposure in coal mines. NIOSH evaluated the effectiveness of the
                existing standard and found the approach of controlling miners'
                exposures to respirable crystalline silica indirectly through the
                control of respirable dust did not protect miners from excessive
                exposure to respirable quartz in all cases (Joy GJ 2012). The study
                concluded that a separate respirable quartz standard, as described by
                the 1995 NIOSH Criteria Document, could reduce miners' risk of
                overexposures to respirable quartz and, by extension, their risk of
                developing silicosis. The adoption of a separate standard would hold
                operators accountable, at risk of a citation and monetary penalty, when
                overexposures of the respirable crystalline silica PEL occur and
                enhance its sampling program to increase the frequency of operator
                sampling.
                ---------------------------------------------------------------------------
                 \35\ Office of Inspector General Audit 05-21-001-06-001, MSHA
                Needs to Improve Efforts to Protect Coal Miners from Respirable
                Crystalline Silica (Nov. 12, 2020). The Inspector General
                recommended that MSHA:
                 1. Adopt a lower legal exposure limit for silica in coal mines
                based on recent scientific evidence.
                 2. Establish a separate standard for silica that allows MSHA to
                issue a citation and monetary penalty when violations of its silica
                exposure limit occur.
                 3. Enhance its sampling program to increase the frequency of
                inspector samples where needed (e.g., by implementing a risk-based
                approach).
                ---------------------------------------------------------------------------
                c. Section 70.205--Approved Sampling Devices; Operation; Air Flowrate
                 MSHA is proposing to amend paragraph (c) of Sec. 70.205 to remove
                the reference to the reduced RCMD standard. References to the RCMD
                exposure limit specified in Sec. 70.100 would replace references to
                the applicable standard. The rest of the section would remain
                unchanged.
                d. Section 70.206--Bimonthly Sampling; Mechanized Mining Units
                 MSHA is proposing to amend subpart C, Sampling Procedures, by
                removing Sec. 70.206 and reserving the section number. Section 70.206
                included requirements for bimonthly sampling of mechanized mining units
                which were in effect until January 31, 2016, and are no longer needed.
                e. Section 70.207--Bimonthly Sampling; Designated Areas
                 MSHA is proposing to amend subpart C, Sampling Procedures, by
                removing Sec. 70.207 and reserving the section number. Section 70.207
                included requirements for bimonthly sampling of designated areas that
                were in effect until January 31, 2016, and are no longer needed.
                f. Section 70.208--Quarterly Sampling; Mechanized Mining Units
                 MSHA is proposing to amend Sec. 70.208 to remove references to a
                reduced RCMD standard. Paragraph (c) in Sec. 70.208 would be removed
                and the paragraph designation reserved. References to the respirable
                dust standard specified in Sec. 70.100 would replace references to the
                applicable standard throughout the section.
                 A new table 1 to Sec. 70.208 would be added. The table contains
                the Excessive Concentration Values (ECV) for the section based on a
                single sample, 3 samples, or the average of 5 or 15 full-shift coal
                mine dust personal sampler unit (CMDPSU) or continuous personal dust
                monitor (CPDM) concentration measurements. This table contains the
                remaining ECV after the removal of the reduced standard in Sec.
                70.101. It was generated from data contained in existing Tables 70-1
                and 70-2 to subpart C of part 70. Conforming changes are made to
                paragraphs (e) and (f)(1) and (2) to update the name of the table to
                table 1 to Sec. 70.208.
                g. Section 70.209--Quarterly Sampling; Designated Areas
                 Similar to the proposed changes discussed above for Sec. 70.208,
                MSHA is proposing to amend Sec. 70.209 to remove references to a
                reduced RCMD standard. Paragraph (b) in Sec. 70.209 would be removed
                and the paragraph designation reserved. References to the RCMD exposure
                limit specified in Sec. 70.100 would replace references to the
                applicable standard.
                 A new table 1 to Sec. 70.209 would be added. The table contains
                the ECVs for the section based on a single sample, 2 or more samples,
                or the average of 5 or 15 full-shift CMDPSU/CPDM concentration
                measurements. This table contains the remaining ECV after the removal
                of the reduced RCMD standard in Sec. 70.101. It was generated from
                data contained in existing Tables 70-1 and 70-2 to subpart C of part
                70. Conforming changes are made to paragraphs (c) and (d)(1) and (2) to
                update the name of the table to table 1 to Sec. 70.209.
                [[Page 44916]]
                h. Subpart C--Table 70-1 and Table 70-2
                 MSHA is proposing to amend subpart C, Sampling Procedures, by
                removing Table 70-1 Excessive Concentration Values (ECV) Based on
                Single, Full-Shift CMDPSU/CPDM Concentration Measurements and Table 70-
                2 Excessive Concentration Values (ECV) Based on the Average of 5 or 15
                Full-Shift CMDPSU/CPDM Concentration Measurements because Sec. 70.101
                would be removed. These tables would be replaced with new tables added
                to Sec. Sec. 70.208 and 70.209.
                4. Part 71--Mandatory Health Standards--Surface Coal Mines and Surface
                Work Areas of Underground Coal Mines
                a. Section 71.2--Definitions
                 As discussed in the analysis of conforming amendments for Sec.
                70.2, MSHA also proposes to remove the Quartz definition in Sec. 71.2
                because the Agency is proposing to remove the respirable dust standard
                when quartz is present in Sec. 71.101. The term quartz would no longer
                appear in part 71.
                b. Section 71.101--Respirable Dust Standard When Quartz Is Present
                 MSHA is proposing to remove the entire section of Sec. 71.101 and
                reserve the section number. Similar to the proposed conforming
                amendments for Sec. 70.101, the respirable coal mine dust standard
                when quartz is present in Sec. 71.101 would no longer be needed
                because MSHA is proposing an independent respirable crystalline silica
                standard in part 60.
                 MSHA's proposal to adopt an independent standard for respirable
                crystalline silica would replace the existing method of indirectly
                controlling miners' exposure to silica by reducing respirable coal
                dust. As stated previously, NIOSH evaluated the effectiveness of the
                existing standard and found the existing approach of controlling
                miners' exposures to respirable crystalline silica indirectly through
                the control of respirable dust did not protect miners from excessive
                exposure to respirable crystalline silica in all cases. The study
                concluded that a separate respirable crystalline silica standard, as
                described by the 1995 NIOSH Criteria Document, could reduce miners'
                risk of overexposures to respirable crystalline silica and, by
                extension, their risk of developing silicosis. The adoption of a
                separate standard would allow MSHA to issue a citation and monetary
                penalty when overexposures of the respirable crystalline silica PEL
                occur and enhance its sampling program to increase the frequency of
                inspector sampling.
                c. Section 71.205--Approved Sampling Devices; Operation; Air Flowrate
                 MSHA is proposing to amend paragraph (c) of Sec. 71.205 to remove
                the reference to the reduced RCMD standard. References to the
                respirable dust standard specified in Sec. 71.100 would replace the
                reference to the applicable standard. The rest of the section would
                remain unchanged.
                d. Section 71.206--Quarterly Sampling; Designated Work Positions
                 Similar to the analysis of conforming amendments for Sec. Sec.
                70.208 and 70.209, MSHA is proposing to amend Sec. 71.206 to remove
                references to the reduced RCMD standard. Paragraph (b) in Sec. 71.206
                would be removed and the paragraph designation reserved. Other
                conforming changes for Sec. 71.206 would remove references to the
                applicable standard and replace them, where needed, with references to
                the respirable dust standard specified in Sec. 71.100 throughout the
                section.
                 MSHA is also proposing to amend paragraph (l) by removing Table 71-
                1 Excessive Concentration Values (ECV) Based on Single, Full-Shift
                CMDPSU/CPDM Concentration Measurements and Table 71-2 Excessive
                Concentration Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/
                CPDM Concentration Measurements since reference to a reduced RCMD
                standard in Sec. 71.101 would be removed. They would be replaced with
                a new table added to Sec. 71.206.
                 Existing paragraph (m) would be modified by removing the language,
                ``in effect at the time the sample is taken, or a concentration of
                respirable dust exceeding 50 percent of the standard established in
                accordance with Sec. 71.101,'' because the reduced standard in Sec.
                71.101 would be removed, as discussed above, which removes the
                reference to the reduced standard and replaces it with a reference to
                the respirable dust standard specified in Sec. 71.100.
                 A new table 1 to Sec. 71.206 would be added. This table contains
                the ECV for the section based on a single sample, two or more samples,
                or the average of five full-shift CMDPSU/CPDM concentration
                measurements. This table contains the remaining ECV after the removal
                of the reduced standard in Sec. 71.101. It was generated from data
                contained in existing Tables 71-1 and 71-2 to subpart C of part 71.
                Conforming changes are made to paragraphs (h) and (i)(1) and (2) to
                update the name of the table to table 1 to Sec. 71.206.
                e. Section 71.300--Respirable Dust Control Plan; Filing Requirements
                 MSHA is proposing to amend Sec. 71.300 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                71.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                f. Section 71.301--Respirable Dust Control Plan; Approval by District
                Manager and Posting
                 MSHA is proposing to amend Sec. 71.301 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                71.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                5. Part 72--Health Standards for Coal Mines
                a. Section 72.800--Single, Full-Shift Measurement of Respirable Coal
                Mine Dust
                 MSHA is proposing to amend Sec. 72.800 in subpart E,
                Miscellaneous, and remove references to the reduced RCMD standard. The
                proposed section would also replace references to Tables 70-1, 71-1,
                and 90-1 with references to tables in Sec. Sec. 70.208, 70.209,
                71.206, and 90.207.
                6. Part 75--Mandatory Safety Standards--Underground Coal Mines
                a. Section 75.350(b)(3)(i) and (ii)--Belt Air Course Ventilation
                 MSHA is proposing to update Sec. 75.350 by revising paragraph
                (b)(3)(i) and removing paragraphs (b)(3)(i)(A) and (B) and (b)(3)(ii).
                 Paragraph (b)(3)(i)(A) would be removed because its provision has
                not been in effect since August 1, 2016. Paragraph (b)(3)(i)(B) would
                be removed because the proposed revised language in paragraph (b)(3)(i)
                would be simplified by stating that ``[t]he average concentration of
                respirable dust in the belt air course, when used as a section intake
                air course, shall be maintained at or below 0.5 mg/m\3\.'' This would
                ensure that miners would be protected from coal dust overexposures,
                including respirable crystalline silica overexposures, by maintaining
                the RCMD PEL in the belt air course at 50 [micro]g/m\3\. Therefore,
                paragraph (b)(3)(i)(B) which sets the PEL for belt course air at 0.5
                mg/m\3\ would be redundant.
                 Existing paragraph (b)(3)(ii) would be removed since it refers to a
                reduced RCMD standard under Sec. 70.101 that would also be removed.
                Existing
                [[Page 44917]]
                paragraph (b)(3)(iii) would be redesignated to (b)(3)(ii).
                7. Part 90--Mandatory Health Standards--Coal Miners Who Have Evidence
                of the Development of Pneumoconiosis
                a. Section 90.2--Definitions
                 Similar to the proposed changes for Sec. Sec. 70.2 and 71.2, MSHA
                proposes to remove the Quartz definition in Sec. 90.2 because the
                Agency proposes to remove the respirable dust standard when quartz is
                present in Sec. 90.101. The term quartz would no longer appear in part
                90.
                 In addition, MSHA is revising the definition of Part 90 miner to
                remove references to the reduced RCMD standard. The respirable dust
                standard specified in Sec. 90.100 would replace the reference to the
                applicable standard. The definition of Part 90 miner would also be
                updated to define Part 90 miners as miners who have exercised the
                option to work in an area of a mine where the average concentration of
                respirable dust in the mine atmosphere during each shift to which that
                miner is exposed is continuously maintained at or below the respirable
                dust standard specified in Sec. 90.100.
                b. Section 90.3--Part 90 Option; Notice of Eligibility; Exercise of
                Option
                 MSHA is proposing to revise paragraph (a) in Sec. 90.3 to require
                that miners diagnosed with pneumoconiosis must be afforded the option
                to work in an area of a mine where the average concentration of
                respirable dust is continuously maintained below the respirable dust
                standard specified in Sec. 90.100 rather than at or below the
                applicable standard. The rest of the section would remain unchanged.
                c. Section 90.101--Respirable Dust Standard When Quartz Is Present
                 MSHA is proposing to remove the entire section and reserve the
                section number. The respirable coal mine dust standard when quartz is
                present in Sec. 90.101 would no longer be needed because MSHA is
                proposing an independent respirable crystalline silica standard in
                proposed part 60.
                 MSHA's proposal to adopt an independent standard for respirable
                crystalline silica would replace the existing method of indirectly
                controlling miners' exposure to respirable crystalline silica by
                reducing respirable coal dust. As stated previously, NIOSH evaluated
                the effectiveness of the existing standard and found the existing
                approach of controlling miners' exposures to respirable crystalline
                silica indirectly through the control of respirable dust did not
                protect miners from excessive exposure to respirable quartz in all
                cases. The study concluded that a separate respirable quartz standard,
                as described by the 1995 NIOSH Criteria Document, could reduce miners'
                risk of overexposures to respirable quartz and, by extension, their
                risk of developing silicosis.
                d. Section 90.102--Transfer; Notice
                 MSHA is proposing to amend Sec. 90.102 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                90.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                e. Section 90.104--Waiver of Rights; Re-Exercise of Option
                 MSHA is proposing to amend Sec. 90.104 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                90.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                f. Section 90.205--Approved Sampling Devices; Operation; Air Flowrate
                 MSHA is proposing to amend Sec. 90.205 to remove the reference to
                the reduced RCMD standard. The respirable dust standard specified in
                Sec. 90.100 would replace the reference to the applicable standard.
                The rest of the section would remain unchanged.
                g. Section 90.206--Exercise of Option or Transfer Sampling
                 MSHA is proposing to amend Sec. 90.206 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                90.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                h. Section 90.207--Quarterly Sampling
                 Similar to the analysis of conforming amendments for Sec. Sec.
                70.208, 70.209, and 71.206, MSHA is proposing to amend Sec. 90.207 to
                remove references to the reduced RCMD standard. Paragraph (b) in Sec.
                90.207 would be removed and the paragraph designation reserved. The
                respirable dust standard specified in Sec. 90.100 would replace
                references to the applicable standard. The rest of the section would
                remain unchanged.
                 MSHA is proposing to amend paragraph (g) by removing the Table 90-1
                Excessive Concentration Values (ECV) Based on Single, Full-Shift
                CMDPSU/CPDM Concentration Measurements and Table 90-2 Excessive
                Concentration Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/
                CPDM Concentration Measurements because Sec. 90.101 would be removed.
                 A new table 1 to Sec. 90.207 would be added to replace the tables
                removed in paragraph (g). The table contains the ECV for the section
                based on a single sample, two or more samples, or the average of 5
                full-shift CMDPSU/CPDM concentration measurements. This table contains
                the remaining ECV after the removal of the reduced standard in Sec.
                90.101. It was generated from data contained in existing Tables 90-1
                and 90-2 to subpart C of part 90. Conforming changes are made to
                paragraphs (c) and (d)(1) and (2) to update the name of the table to
                table 1 to Sec. 90.207.
                i. Section 90.300--Respirable Dust Control Plan; Filing Requirements
                 MSHA is proposing to amend Sec. 90.300 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                90.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                j. Section 90.301--Respirable Dust Control Plan; Approval by District
                Manager; Copy to Part 90 Miner
                 MSHA is proposing to amend Sec. 90.301 to remove references to the
                reduced RCMD standard. The respirable dust standard specified in Sec.
                90.100 would replace references to the applicable standard. The rest of
                the section would remain unchanged.
                C. Updating MSHA Respiratory Protection Standards: Proposed
                Incorporation of ASTM F3387-19 by Reference
                 MSHA is proposing to update the Agency's existing respiratory
                protection standard to help safeguard the life and health of all miners
                exposed to respirable airborne hazards at MNM and coal mines. The
                proposed rule would incorporate by reference ASTM F3387-19, ``Standard
                Practice for Respiratory Protection'' (ASTM F3387-19), as applicable,
                in existing Sec. Sec. 56.5005, 57.5005, and 72.710, as well as in
                proposed Sec. 60.14(c)(2). The ASTM F3387-19 standard includes
                provisions for selection, fitting, use, and care of respirators used to
                remove airborne contaminants from the air using filters, cartridges, or
                canisters, as well as respirators that protect in oxygen-deficient or
                immediately dangerous to life or health (IDLH) atmospheres. ASTM F3387-
                19 is based on the most recent consensus standards recognized by
                experts in government and professional associations on the selection,
                use, and maintenance for
                [[Page 44918]]
                respiratory equipment. The ASTM Standard would replace American
                National Standards Institute's ANSI Z88.2-1969, ``Practices for
                Respiratory Protection'' (ANSI Z88.2-1969), which is incorporated in
                the existing standards.
                 Incorporating this voluntary consensus standard complies with the
                Federal mandate--as set forth in the National Technology Transfer and
                Advancement Act of 1995 and OMB Circular A119--that agencies use
                voluntary consensus standards in their regulatory activities unless
                doing so would be legally impermissible or impractical. This standard
                proposed for incorporation would also improve clarity because it is a
                consensus standard developed by stakeholders.
                 Under existing standards, whenever respiratory protective equipment
                is used, mine operators are required to have a respiratory protection
                program that is consistent with the provisions of ANSI Z88.2-1969. At
                the time of its publication, ANSI Z88.2-1969 reflected a consensus of
                accepted practices for respiratory protection.
                 Respirator technology and knowledge on respiratory protection have
                since advanced and as a result, changes in respiratory protection
                standards have occurred. For example, in 2006, OSHA revised its
                respiratory protection standard to add definitions and requirements for
                Assigned Protection Factors (APF) and Maximum Use Concentrations (MUCs)
                (71 FR 50121, 50122, Aug. 24, 2006). In addition to this rulemaking,
                OSHA updated Appendix A to Sec. 1910.134: Fit Testing Procedures (69
                FR 46986, 46993, Aug. 4, 2004).
                 After withdrawing the 1992 version of Z-88.2 in 2002, ANSI
                published the American National Standard, ANSI/AIHA Z88.10-2010,
                ``Respirator Fit Testing Methods,'' approved in 2010. These rules and
                standards addressed the topics of APFs and fit testing. APFs provide
                employers with critical information to use when selecting respirators
                for employees exposed to atmospheric contaminants found in industry.
                Finally, in 2015, ANSI published ANSI/ASSE Z88.2-2015, ``Practices for
                Respiratory Protection,'' which referenced OSHA regulations. These
                updates included requirements for classification of considerations for
                selection and use of respirators, establishment of cartridge/canister
                change schedules, use of fit factor value for respirator fit testing,
                calculation of effective protection factors, and compliance with
                compressed air dew requirements, compressed breathing air equipment,
                and systems and designation of positive pressure respirators. In July
                2017, ANSI/ASSE transferred the responsibilities for developing
                respiratory consensus standards to ASTM International.
                 ASTM F3387-19 is based on the most recent consensus standards
                recognized by experts in government and professional associations on
                the selection, use, and maintenance for respiratory protection
                equipment. The standard contains detailed guidance and provisions on
                respirator selection that are based on NIOSH's long-standing experience
                of testing and approving respirators for occupational use and OSHA's
                research and rulemaking on respiratory protection. ASTM F3387-19 also
                addresses all aspects of establishing, implementing, and evaluating
                respiratory protection programs and establishes minimum acceptable
                respiratory protection program elements in the areas of program
                administration, standard operating procedures, medical evaluation,
                respirator selection, training, fit testing, respirator maintenance,
                inspection, and storage. ASTM F3387-19 comprehensively covers numerous
                aspects of respiratory protection and provides the most up-to-date
                provisions for current respirator technology and effective respiratory
                protection. Therefore, MSHA believes that ASTM F3387-19 would provide
                mine operators with information and guidance on the proper selection,
                use, and maintenance of respirators, which would protect the health and
                safety of miners.
                 Under this proposed rule, MSHA would require that operators
                establish a respiratory protection program in writing, that includes
                minimally acceptable program elements: program administration; standard
                operating procedures; medical evaluations; respirator selection;
                training; fit testing; and maintenance, inspection, and storage.
                 Beyond the minimally acceptable program elements, MSHA proposes to
                provide mine operators with flexibility to select the provisions in
                ASTM F3387-19 that are applicable to the conditions of their mines and
                respirator use by their miners. In MSHA's experience, the need for and
                actual use of respirators varies among mines for different reasons,
                including the type of commodity mined or processed and the mining
                method and controls used. At some mines, miners may not use or may only
                rarely use respirators. At other mines, miners may use respirators more
                frequently. Recognizing these differences, MSHA would allow mine
                operators to comply with the provisions in ASTM F3387-19 that they deem
                are relevant and appropriate for their mining operations and
                conditions.
                 MSHA has observed that many operators, in particular larger mine
                operators, have already implemented in their respiratory programs many
                OSHA requirements, which are substantially similar to many requirements
                in ASTM F3387-19. Indeed, ASTM F3387-19 refers to OSHA's regulations on
                respiratory protection programs, APFs and MUCs, and fit testing. MSHA
                believes that the mining industry is already familiar with many
                provisions in ASTM F3387-19. MSHA anticipates that for many large mine
                operators, few changes to their respiratory protection program may be
                warranted, whereas small mines, or mines that use respirators
                intermittently, may need to revise their respiratory practices in
                accordance with the requirements, as applicable, in ASTM F3387-19.
                1. Respiratory Program Elements
                 Under the proposed rule, MSHA would require that the respiratory
                protection program be in writing and that it include the following
                minimally acceptable program elements: program administration; standard
                operating procedures; medical evaluations; respirator selection;
                training; fit testing; and maintenance, inspection, and storage.
                a. Program Administration
                 ASTM F3387-19 specifies several practices related to respiratory
                protection program administration, including the qualifications and
                responsibilities of a program administrator. For example, ASTM F3387-19
                provides that responsibility and authority for the respirator program
                be assigned to a single qualified person with sufficient knowledge of
                respiratory protection. Qualifications could be gained through training
                or experience; however, the qualifications of a program administrator
                must be commensurate with the respiratory hazards present at a
                worksite.
                 This individual should have access to and direct communication with
                the site manager about matters impacting worker safety and health. ASTM
                F3387-19 notes a preference that the administrator be in the company's
                industrial hygiene, environmental, health physics, or safety
                engineering department; however, a third-party entity meeting the
                provisions may also provide this service. ASTM F3387-19 outlines the
                respiratory program administrator's responsibilities, specifying that
                they should include: measuring, estimating, or reviewing
                [[Page 44919]]
                information on the concentration of airborne contaminants; ensuring
                that medical evaluations, training, and fit testing are performed;
                selecting the appropriate type or class of respirator that will provide
                adequate protection for each contaminant; maintaining records;
                evaluating the respirator program's effectiveness; and revising the
                program, as necessary.
                b. Standard Operating Procedures (SOP)
                 SOPs are written policies and procedures available for all wearers
                of respirators to read and are established by the employer. ASTM F3387-
                19 states that written SOPs for respirator programs are necessary when
                respirators are used routinely or sporadically. Written SOPs should
                cover hazard assessment; respirator selection; medical evaluation;
                training; fit testing; issuance, maintenance, inspection, and storage
                of respirators; schedule of air-purifying elements; hazard re-
                evaluation; employer policies; and program evaluation and audit. ASTM
                F3387-19 also provides that wearers of respirators be provided with
                copies of the SOP and that written SOPs include special consideration
                for respirators used for emergency situations. The procedures are
                reviewed in conjunction with the annual respirator program audit and
                are revised by the program administrator, as necessary.
                c. Medical Evaluation
                 Medical evaluations determine whether an employee has any medical
                conditions that would preclude the use of respirators, limitation on
                use, or other restrictions. ASTM F3387-19 provides that a program
                administrator advise the PLHCP of the following conditions to aid in
                determining the need for a medical evaluation: type and weight of the
                respirator to be used; duration and frequency of respirator use
                (including use for rescue and escape); typical work activities;
                environmental conditions (e.g., temperature); hazards for which the
                respirator will be worn, including potential exposure to reduced-oxygen
                environments; and additional protective clothing and equipment to be
                worn. ASTM F3387-19 also incorporates ANSI Z88.6 Respiratory
                Protection--Respirator Use--Physical Qualifications for Personnel.
                d. Respirator Selection
                 Proper respirator selection is an important component of an
                effective respiratory protection program. ASTM F3387-19 provides that
                proper respirator selection consider the following: the nature of the
                hazard, worker activity and workplace factors, respirator use duration,
                respirator limitations, and use of approved respirators. ASTM F3387-19
                states that respirator selection for both routine and emergency use
                include hazard assessment, selection of respirator type or class that
                can offer adequate protection, and maintenance of written records of
                hazard assessment and respirator selection.
                 ASTM F3387-19 provides specific steps to establish the nature of
                inhalation hazards, including determining the following: the types of
                contaminants present in the workplace; the physical state and chemical
                properties of all airborne contaminants; the likely airborne
                concentration of the contaminants (by measurement or by estimation);
                potential for an oxygen-deficient environment; an occupational exposure
                limit for each contaminant; existence of an IDLH atmosphere; and
                compliance with applicable health standards for the contaminants.
                 ASTM F3387-19 includes other information to support the respirator
                selection process, including information on operational
                characteristics, capabilities, and performance limitations of various
                types of respirators. These limitations must be considered during the
                selection process. ASTM F3387-19 also describes types of respirators
                and consideration for their use, including service life, worker
                mobility, compatibility with other protective equipment, durability,
                comfort factors, compatibility with the environment, and compatibility
                with job and workforce performance. Finally, ASTM F3387-19 provides
                other essential information regarding respirator selection such as
                oxygen deficiency, ambient noise, and need for communication.
                e. Training
                 Employee training is essential for correct respirator use. ASTM
                F3387-19 provides that all users be trained in their area of
                responsibility by a qualified person to ensure the proper use of
                respirators. A respirator trainer must be knowledgeable in the
                application and use of the respirators and must understand the site's
                work practices, respirator program, and applicable regulations.
                Employees who receive training include the workplace supervisor, the
                person issuing and maintaining respirators, respirator wearers, and
                emergency teams. To ensure the proper and safe use of a respirator,
                ASTM F3387-19 also provides that the minimum training for each
                respirator wearer includes: the need for respiratory protection; the
                nature, extent, and effects of respiratory hazards in the workplace;
                reasons for particular respirator selections; reasons for engineering
                controls not being applied or reasons why they are not adequate; types
                of efforts made to reduce or eliminate the need for respirators;
                operation, capabilities, and limitations of the respirators selected;
                instructions for inspecting, donning, and doffing the respirator; the
                importance of proper respirator fit and use; and maintenance and
                storage of respirators. The standard provides for each respirator
                wearer to receive initial and annual training. Workplace supervisors
                and persons issuing respirators are retrained as determined by the
                program administrator. Training records for each respirator wearer are
                maintained and include the date, type of training received, performance
                results (as appropriate), and instructor's name.
                f. Respirator Fit Testing
                 A serious hazard may occur if a respirator, even though properly
                selected, is not properly fitted. For example, if a proper face seal is
                not achieved, the respirator would provide a lower level of protection
                than it is designed to provide because the respirator could allow
                contaminants to leak into the breathing area. Proper fit testing
                verifies that the selected make, model, and size of a respirator
                adequately fits and ensures that the expected level of protection is
                provided. ASTM F3387-19 includes provisions for qualitative and
                quantitative fit testing to determine the ability of a respirator
                wearer to obtain a satisfactory fit with a tight-fitting respirator and
                incorporates ANSI/AIHA Z88.10, Respirator Fit Testing Methods, for
                guidance on how to conduct fit testing of tight-fitting respirators and
                appropriate methods to be used. ASTM F3387-19 also provides information
                on conducting quantitative and qualitative fits test to determine how
                well a tight-fitting respirator fits a wearer. This includes
                information on the application of fit factors and assigned protection
                factors, and how these factors are used to ensure that a wearer is
                receiving the necessary protection. ASTM F3387-19 provides for each
                respirator wearer to be fit tested before being assigned a respirator
                (currently at least once every 12 months or repeated when a wearer
                expresses concern about respirator fit or comfort or has a condition
                that may interfere with the face piece seal).
                g. Maintenance, Inspection, and Storage
                 Proper maintenance and storage of respirators are important in a
                respiratory protection program. ASTM F3387-19 includes specific
                provisions for
                [[Page 44920]]
                decontaminating, cleaning, and sanitizing respirators, inspecting
                respirators, replacing, and repairing parts, and storing and disposing
                of respirators. For example, the decontamination provisions state that
                respirators are decontaminated after each use and cleaned and sanitized
                regularly per manufacturer instructions. Following cleaning and
                disinfection, reassembled respirators are inspected to verify proper
                working condition. ASTM F3387-19 states that employers consult
                manufacturer instructions to determine component expiration dates or
                end-of-service life, inspect the rubber or other elastomeric components
                of respirators for signs of deterioration that would affect respirator
                performance, and repair or replace respirators failing inspection. ASTM
                F3387-19 also provides that respirators are stored according to
                manufacturer recommendations and in a manner that will protect against
                hazards (i.e., physical, biological, chemical, vibration, shock,
                temperature extremes, moisture, etc.). It also provides that
                respirators are stored to prevent distortion of rubber or other parts.
                2. Section-by-Section Analysis of Incorporation by Reference--ASTM
                F3387-19
                a. Part 56--Safety and Health Standards--Surface Metal and Nonmetal
                Mines--Section 56.5005--Control of Exposure to Airborne Contaminants
                 Existing Sec. 56.5005 provides that whenever respiratory
                protective equipment is used, a program for selection, maintenance,
                training, fitting, supervision, cleaning, and use shall meet the
                requirements of paragraph (b). Paragraph (b) requires that mine
                operators implement a respirator program consistent with the
                requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph
                (b) to remove the incorporation by reference to ANSI Z88.2-1969 and
                incorporate by reference ASTM F3387-19.
                 MSHA is proposing to revise paragraph (b) to state that approved
                respirators must be selected, fitted, cleaned, used, and maintained in
                accordance with the requirements of ASTM F3387-19 ``as applicable.''
                Under the proposal, MSHA would require that the respiratory program be
                in writing and that it include the following minimally acceptable
                program elements: program administration; standard operating
                procedures; medical evaluations; respirator selection; training; fit
                testing; and maintenance, inspection, and storage.
                 Also, MSHA is proposing to change paragraph (c) to require the
                presence of at least one other person with backup equipment and rescue
                capability when respiratory protection is used in atmospheres that are
                IDLH. This change is needed to conform to language in the proposed
                incorporation by reference of ASTM F3387-19, which defines IDLH as
                ``any atmosphere that poses an immediate hazard to life or immediate
                irreversible debilitating effects on health'' (ASTM International
                2019).
                b. Part 57--Safety and Health Standards--Underground Metal and Nonmetal
                Mines--Section 57.5005--Control of Exposure to Airborne Contaminants
                 Existing Sec. 57.5005 provides that whenever respiratory
                protective equipment is used, a program for selection, maintenance,
                training, fitting, supervision, cleaning, and use shall meet the
                requirements of paragraph (b). Paragraph (b) requires that mine
                operators implement a respirator program consistent with the
                requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph
                (b) to remove the incorporation by reference to ANSI Z88.2-1969 and
                incorporate by reference ASTM F3387-19.
                 MSHA is proposing to revise paragraph (b) to state that approved
                respirators must be selected, fitted, cleaned, used, and maintained in
                accordance with the requirements of ASTM F3387-19 ``as applicable.''
                Under the proposal, MSHA would require that the respiratory program be
                in writing and that it include the following minimally acceptable
                program elements: program administration; standard operating
                procedures; medical evaluations; respirator selection; training; fit
                testing; and maintenance, inspection, and storage.
                 Also, MSHA is proposing to change paragraph (c) to require the
                presence of at least one other person with backup equipment and rescue
                capability when respiratory protection is used in atmospheres that are
                IDLH. This change is needed to conform to language in the proposed
                incorporation by reference of ASTM F3387-19, which defines the term
                IDLH as ``any atmosphere that poses an immediate hazard to life or
                immediate irreversible debilitating effects on health'' (ASTM
                International 2019).
                c. Part 72--Health Standards for Coal Mines--Section 72.710--Selection,
                Fit, Use, and Maintenance of Approved Respirators
                 Existing Sec. 72.710 requires approved respirators be selected,
                fitted, used, and maintained in accordance with the provisions of ANSI
                Z88.2-1969, which was incorporated by reference into coal standards in
                1995 (60 FR 30398, June 8, 1995). MSHA is proposing to revise Sec.
                72.710 by removing the requirement in the first sentence that coal mine
                operators must ensure that the maximum amount of respiratory protection
                is made available to miners when respirators are used. MSHA believes
                that the use of approved respirators and the proposed incorporation by
                reference of ASTM F3387-19 would ensure that coal miners' health is
                protected. Under the proposal, MSHA would require that the respiratory
                program be in writing and that it include the following minimally
                acceptable program elements: program administration; standard operating
                procedures; medical evaluations; respirator selection; training; fit
                testing; and maintenance, inspection, and storage.
                VIII. Technological Feasibility
                 This technological feasibility analysis considers whether currently
                available technologies, used alone or in combination with each other,
                can be used by operators to comply with the proposed standard.
                 MSHA is required to set standards to assure, based on the best
                available evidence, that no miner will suffer material impairment of
                health or functional capacity from exposure to toxic materials or
                harmful physical agents over his working life. 30 U.S.C. 811(a)(6)(A).
                The Mine Act also instructs MSHA to set health standards to attain
                ``the highest degree of health and safety protection for the miner''
                while considering ``the latest available scientific data in the field,
                the feasibility of the standards, and experience gained under this and
                other health and safety laws.'' 30 U.S.C. 811(a)(6)(A). But the health
                and safety of the miner is always the paramount consideration: ``[T]he
                Mine Act evinces a clear bias in favor of miner health and safety,''
                and ``[t]he duty to use the best evidence and to consider feasibility
                are appropriately viewed through this lens and cannot be wielded as
                counterweight to MSHA's overarching role to protect the life and health
                of workers in the mining industry.'' Nat'l Min. Ass'n v. Sec'y, U.S.
                Dep't of Lab., 812 F.3d 843, 866 (11th Cir. 2016); 30 U.S.C. 801(a).
                [[Page 44921]]
                 The D.C. Circuit clarified the Agency's obligation to demonstrate
                the technological feasibility of reducing occupational exposure to a
                hazardous substance. MSHA ``must only demonstrate a `reasonable
                possibility' that a `typical firm' can meet the permissible exposure
                limits in `most of its operations.'' Kennecott Greens Creek Min. Co. v.
                Mine Safety & Health Admin., 476 F.3d 946, 958 (D.C. Cir. 2007)
                (quoting American Iron & Steel Inst. v. OSHA, 939 F.2d 975, 980 (D.C.
                Cir. 1991)).
                 This section presents technological feasibility findings that
                guided MSHA's selection of the proposed PEL. MSHA's technological
                feasibility findings are organized into two main sections covering: (1)
                the technological feasibility of proposed part 60; and (2) the
                technological feasibility of the proposed revision to existing
                respiratory protection standards. Based on the analyses presented in
                the two sections, MSHA preliminarily concludes that the Agency's
                proposal is technologically feasible. MSHA's feasibility determinations
                in this rulemaking are supported by its findings that the majority of
                the industry is already using technology that would be sufficient to
                comply with the proposed rule.
                 First, MSHA has preliminarily determined that proposed part 60 is
                technologically feasible. Many mine operators already maintain
                respirable crystalline silica exposures at or below the proposed PEL of
                50 [mu]g/m\3\, and at mines where there are elevated exposures,
                operators would be able to reduce exposures to at or below the proposed
                PEL by properly maintaining existing engineering controls and/or by
                implementing new engineering and administrative controls that are
                currently available. In addition, mines would be able to satisfy the
                exposure monitoring requirements of proposed part 60 with existing,
                validated, and widely used sampling technologies and analytical
                methods.
                 Second, the analysis shows that the proposed update to MSHA's
                respiratory protection requirements is also technologically feasible.
                The mining industry's existing respiratory protection practices for
                selecting, fitting, using, and maintaining respiratory protection
                include program elements that are similar to those of ASTM F3387-19,
                ``Standard Practice for Respiratory Protection'' (ASTM F3387-19), which
                MSHA is proposing to incorporate by reference.
                A. Technological Feasibility of Sampling and Analytical Methods
                1. Sampling Methods
                 MSHA's proposed rule would require mine operators in both MNM and
                coal mines to conduct sampling for respirable crystalline silica using
                respirable particle size-selective samplers that conform to the
                ``International Organization for Standardization (ISO) 7708:1995: Air
                Quality--Particle Size Fraction Definitions for Health-Related
                Sampling'' standard. The ISO convention defines respirable particulates
                as having a 4 micrometer ([mu]m) aerodynamic diameter median cut-point
                (i.e., 4 [mu]m-sized particles are collected with 50 percent
                efficiency), which approximates the size distribution of particles that
                when inhaled can reach the alveolar region of the lungs. For this
                reason, the ISO convention is widely considered biologically relevant
                for respirable particulates and provides appropriate criteria for
                equipment used to sample respirable crystalline silica. MSHA's current
                sampling method for MNM mines meets the ISO criteria by using a 10 mm
                Dorr-Oliver cyclone and a sampling pump operated at a flow rate of 1.7
                liter per minute (L/min), and MNM mine operators also already use this
                type of sampler for MNM sampling under existing standards. MSHA's
                current sampling method for RCMD, including respirable crystalline
                silica, uses a 10 mm Dorr-Oliver cyclone but operated at 2.0 L/min to
                approximate the British Mining Research Establishment (MRE) sampling
                criteria, and thus does not meet the ISO criteria. Although, the
                existing sampling pumps can be adjusted to operate at a flow rate of
                1.7 L/min flow rate to meet the ISO criteria. To comply with this
                proposed requirement, coal mine operators that currently use coal mine
                dust personal sampler units (CMDPSU) would need to adjust their
                samplers to the flow rate specified by the manufacturer for complying
                with the ISO.
                 There are a variety of size-selective samplers on the market that
                meet the ISO respirable-particle-size selection criteria. Examples
                include Dorr-Oliver cyclone currently used by MSHA and OSHA, operated
                at 1.7 L/min; SKC aluminum cyclone (2.5 L/min); HD cyclone (2.2 L/min);
                SKC GS-3 multi-inlet cyclone (2.75 L/min); and BGI GK 2.69 (4.2 L/min).
                Each cyclone has different operating specifications and performance
                criteria, but they all are compliant with the ISO criteria for
                respirable dust with an acceptable level of measurement bias.
                Manufacturers of size-selective samplers specify the flow rates that
                are necessary to conform to the particle size collection criteria of
                the ISO standard. Samplers used in both MNM and coal mines can be used
                to perform the proposed sampling, and because other commercially
                available (already on the market) samplers conform to the ISO standard,
                MSHA preliminarily finds that sampling in accordance with the ISO
                standard is technologically feasible.
                2. Analytical Methods and Feasibility of Measuring Below the Proposed
                PEL and Action Level
                 After a respirable dust sample is collected and submitted to a
                laboratory, it must be analyzed to quantify the mass of respirable
                crystalline silica present. The laboratory method must be sensitive
                enough to detect and quantify respirable crystalline silica at levels
                below the applicable concentration. The analytical limit of detection
                (LOD) and/or limit of quantification (LOQ), together with the sample
                volume, determine the airborne concentration LOD and/or LOQ for a given
                air sample. MSHA proposes a PEL for respirable crystalline silica of 50
                [mu]g/m\3\ as a full shift, 8-hour TWA for both MNM and coal mines.
                Several analytical methods are available for measuring respirable
                crystalline silica at levels well below the proposed PEL of 50 [mu]g/
                m\3\ and action level of 25 [mu]g/m\3\.
                 MSHA uses two main analytical methods (1) P-2: X-Ray Diffraction
                Determination Of Quartz And Cristobalite In Respirable Metal/Nonmetal
                Mine Dust (analysis by X-ray diffraction, XRD) for MNM mines and (2) P-
                7: Determination Of Quartz In Respirable Coal Mine Dust By Fourier
                Transform Infrared Spectroscopy (analysis by infrared spectroscopy,
                FTIR or IR) for coal mines.\36\ The MSHA P-2 and P-7 methods, reliably
                analyze compliance samples collected by MSHA inspectors, including 15
                years of MNM compliance samples and 5 years of coal industry compliance
                samples MSHA used for the exposure profile portion of this
                technological feasibility analysis. These methods are capable of
                measuring respirable crystalline silica exposures at levels below the
                proposed PEL and action level.
                ---------------------------------------------------------------------------
                 \36\ Other similar XRD methods include NIOSH-7500 and OSHA ID-
                142. XRD methods are able to distinguish between the different
                polymorphs--quartz, cristobalite and tridymite. Other IR methods
                include NIOSH 7602 and 7603. IR methods are efficient, but they are
                more prone to interferences and should only be used for samples with
                a well-characterized matrix (e.g., coal dust).
                ---------------------------------------------------------------------------
                 For an analytical method to have acceptable sensitivity for
                determining
                [[Page 44922]]
                exposures at the proposed PEL of 50 [mu]g/m\3\ and action level of 25
                [mu]g/m\3\, the LOQ must be at or below the amount of analyte (e.g.,
                quartz) that would be collected in an air sample where the
                concentration of analyte is equivalent to the proposed PEL or action
                level. To determine the minimum airborne concentration that can be
                quantified, the LOQ mass is divided by the sample air volume, which is
                determined by the sampling flow rate and duration. Table VIII-1
                presents minimum quantifiable quartz concentrations, for various
                cyclones and established analytical methods.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.025
                 Based on this discussion, MSHA preliminarily finds that current
                analytical methods are sufficiently sensitive to meet the proposed PEL
                and action level.
                3. Laboratory Capacity
                 MSHA's proposed standard would require that mines conduct baseline
                sampling, periodic sampling, corrective actions sampling, and post-
                evaluation sampling with analyses conducted by laboratories that meet
                ISO 17025, General Requirements for the Competence of Testing and
                Calibration Laboratories (ISO 17025). The majority of U.S. industrial
                hygiene laboratories that perform respirable crystalline silica
                analysis are accredited to ISO 17025 by the American Industrial Hygiene
                Association (AIHA) Laboratory Accreditation Program (LAP). The AIHA LAP
                lists 23 accredited commercial laboratories nationwide that, as of
                April 2022, perform respirable crystalline silica analysis using an
                MSHA, NIOSH or OSHA method.
                 MSHA interviewed a sample of three laboratories (one small-capacity
                laboratory,\37\ one medium-capacity laboratory,\38\ and one large-
                capacity laboratory) \39\ to estimate their sample-processing capacity.
                Insights from these interviews suggest that laboratories have the
                ability to provide surge capacity as the proposed rule is phased in.
                Collectively, these three laboratories could process approximately
                33,240 samples by XRD (suitable for MNM mines) and 1,752 samples by
                FTIR or IR (suitable for coal mines) within a 6-month period.
                Extrapolating this across all laboratories that can analyze respirable
                crystalline silica samples, MSHA estimates that 232,680 samples for MNM
                mines and 12,250 samples for coal mines could be processed in the
                phase-in 6-month period. Over the first 12 months after the standard
                goes into effect, analysis would be available for 465,360 samples for
                MNM mines and 24,500 samples for coal mines.
                ---------------------------------------------------------------------------
                 \37\ The small capacity laboratory has a maximum respirable
                crystalline silica sample analysis capacity of 300 samples per month
                (280 additional samples per month above the current number of
                samples analyzed), a level which the laboratory could sustain for
                two months.
                 \38\ The medium capacity laboratory has a maximum respirable
                crystalline silica sample analysis capacity of 2,025 samples per
                month. Surge from the mining industry is considered to replace,
                rather than be in addition to the current number of samples
                analyzed.
                 \39\ The large capacity laboratory has a maximum respirable
                crystalline silica sample analysis capacity of 4,500 samples per
                month (3,700 additional samples per month above the current number
                of samples analyzed).
                ---------------------------------------------------------------------------
                 Based on exposure profiles for the MNM and coal mining industries
                and MSHA's experience and knowledge of the mining industry, MSHA
                estimates that within this first 12-month period, mines would seek
                analysis for a total of 172,907 respirable crystalline silica samples
                (including 58,126 samples for MNM mines and 12,373 samples for coal
                mines associated with the 6-month baseline sampling period). In the
                subsequent 12-month period, mines would require analysis for 102,409
                samples (includes process/control measure evaluation samples and
                periodic samples associated with the
                [[Page 44923]]
                proposed action level), a number that will decline over years 1 through
                6 as the mine operators reduce some miner exposures below the proposed
                action level.\40\ Comparing these figures with the surge capacity
                estimates previously noted above, MSHA believes that there would be
                sufficient processing capacity to meet the sampling analysis schedule
                envisioned in the proposed rule.
                ---------------------------------------------------------------------------
                 \40\ MSHA anticipates that in the initial six-month baseline
                period mine operators will collect 70,498 baseline samples, of which
                12,373 will be coal mine samples. In the 12 months beginning after
                the initial baseline period, mines will collect 88,281 samples for
                miners who are exposed at or above the proposed action level (25
                [micro]g/m\3\), but at or below the proposed PEL, plus 14,128
                samples to evaluate corrective action and process change (i.e.,
                processes which must be analyzed to determine whether newly
                implemented dust control measures are successful and processes newly
                identified during periodic walk-through evaluations), for a total of
                102,409 samples per year (including 25,152 coal mine samples).
                Estimates are as of December 2022.
                ---------------------------------------------------------------------------
                a. Baseline Sampling
                 MSHA's proposal would require baseline sampling for each miner who
                is or may reasonably be expected to be exposed to respirable
                crystalline silica within 180 days (6 months) of the standard's
                effective date.\41\ This would require an initial increase in
                analytical laboratory capacity of approximately 70,498 sample analyses
                over 6 months. MSHA expects that with months of lead time during the
                proposed rule and final rule stages of the rulemaking, laboratories
                would anticipate the initial baseline period increase in demand and
                would respond by increasing their analytical capacity. For example,
                laboratories could acquire additional instrumentation, train additional
                analysts, or add a second or third operating shift. This is
                particularly likely given that demand would be based on a regulatory
                requirement and during the rulemaking process MSHA would conduct
                outreach to make all relevant stakeholders aware of the rule's
                provisions. MSHA is specifically soliciting comments on the
                technological feasibility of laboratory capability to conduct baseline
                sampling. At this point in the rulemaking, MSHA believes that the
                proposed rule is technologically feasible for laboratories to conduct
                baseline sampling analyses.
                ---------------------------------------------------------------------------
                 \41\ Where several miners perform similar activities on the same
                shift, only a representative fraction of miners (minimum of two
                miners) would need to be sampled, including those expected to have
                the highest exposures.
                ---------------------------------------------------------------------------
                b. Periodic, Corrective Actions, and Post-Evaluation Sampling
                 Under proposed Sec. 60.12 (b)-(e), three conditions would require
                mine operators to conduct additional sampling after the initial 6-month
                baseline period. First, when the most recent sampling indicates that
                miner exposures are at or above the proposed action level (25 [micro]g/
                m\3\) but at or below the proposed PEL (50 [micro]g/m\3\), the mine
                operator would be required to sample within 3 months of that sampling
                and continue to sample within 3 months of the previous sampling until
                two consecutive samplings indicate that miner exposures are below the
                action level. Second, where the most recent sampling indicates that
                miner exposures are above the PEL, the mine operator would be required
                to sample after corrective actions are taken to reduce overexposures,
                until sampling results indicate miner exposures are at or below the
                PEL. Third, if the mine operator determines, as a result of the semi-
                annual evaluation, that miners may be exposed to respirable crystalline
                silica at or above the action level, the mine operator would be
                required to perform sampling to assess the full-shift, 8-hour TWA
                exposure of respirable crystalline silica for each miner who is or may
                reasonably be expected to be at or above the action level.
                 MSHA estimates that the total number of analyses (489,860) that
                laboratories will be able to perform per year is more than 2.5 times
                the total estimated number of samples for which mines will seek
                analyses in the first year (172,907). Based on the estimated surplus
                analyses available beyond baseline sampling (419,362), MSHA
                preliminarily finds that periodic, corrective actions, and post-
                evaluation sampling would also be technologically feasible both in the
                first year and in subsequent years.\42\
                ---------------------------------------------------------------------------
                 \42\ 489,860 total annual laboratory analyses divided by 172,907
                mine samples to be analyzed, equals 2.83 percent surplus sample
                analyses. 489,860 total analyses-70,498 baseline analyses = a
                surplus of 419,362 analyses available for the 102,409 periodic,
                corrective actions, and process change sampling.
                ---------------------------------------------------------------------------
                B. Technological Feasibility of the Proposed PEL
                1. Methodology
                 The technological feasibility analysis for the proposed PEL relies
                primarily on information from three key sources:
                 MSHA's Standardized Information System (MSIS) respirable
                crystalline silica exposure data, which includes 57,769 MNM and 63,127
                coal mine compliance samples collected by MSHA inspectors; these
                samples were of sufficient mass to be analyzed for respirable
                crystalline silica by MSHA's analytical laboratory.\43\
                ---------------------------------------------------------------------------
                 \43\ These respirable crystalline silica exposure data consist
                of 15 years of MNM mine samples (January 1, 2005, through December
                31, 2019) and five years of coal mine samples (August 1, 2016,
                through July 31, 2021). These MSHA compliance samples represent the
                conditions identified by MSHA inspectors as having the greatest
                potential for respirable crystalline silica exposure during the
                periodic inspection when sampling occurred. While MSHA's laboratory
                also analyzes mine operators' respirable coal mine dust samples
                containing respirable crystalline silica, those samples are not
                included in the data used for this analysis.
                ---------------------------------------------------------------------------
                 The National Institute for Occupational Safety and Health
                (NIOSH) series on reducing respirable dust in mines, including: ``Dust
                Control Handbook for Industrial Minerals Mining and Processing, Second
                Edition'' (NIOSH, 2019b) and ``Best Practices for Dust Control in Coal
                Mining, Second Edition'' (NIOSH, 2021a).\44\ With cooperation from the
                MNM and coal mining industries, NIOSH has extensively researched and
                documented engineering and administrative controls for respirable
                crystalline silica in mines.
                ---------------------------------------------------------------------------
                 \44\ Together, these two recent reports provide more than 500
                pages of detailed descriptions, discussion, and illustrations of
                dust control technologies currently used in mines.
                ---------------------------------------------------------------------------
                 MSHA's knowledge of the mining industry. MSHA has over
                four decades of experience inspecting surface mines at least twice per
                year and underground mines at least four times per year and in
                assisting mine operators and miners with technological issues,
                including control of respirable dust (including respirable crystalline
                silica) exposure. MSHA offers informational programs, training,
                publications, onsite evaluations, and investigations that document
                conditions in mines and help mines operate in a safe and healthy
                manner.\45\
                ---------------------------------------------------------------------------
                 \45\ MSHA also analyzes RCMD samples collected by mine
                operators, including those containing respirable crystalline silica,
                in addition to the compliance samples collected by MSHA inspectors
                (mentioned in the first bullet of this series).
                ---------------------------------------------------------------------------
                 MSHA also consulted other published reports, scientific journal
                articles, and information from equipment manufacturers and mining
                industry suppliers.\46\
                ---------------------------------------------------------------------------
                 \46\ Project personnel reviewed 104,365 samples collected and
                analyzed by MSHA for respirable crystalline silica, plus another
                103,745 samples collected but not analyzed due to insufficient
                respirable dust collected in the sample. They examined over 200
                published reports, proceedings, case studies, analytical methods,
                and journal articles, in addition to inspecting more than 200 web
                page, product brochures, user manuals, service/maintenance manuals
                and descriptive literature for dust control products, mining
                equipment, and related services.
                ---------------------------------------------------------------------------
                2. The Technological Feasibility Analysis Process
                a. Mining Commodity Categories and Activity Groups
                 As described in the Preliminary Regulatory Impact Analysis (PRIA),
                MSHA categorized mine types into six MNM ``commodity categories''
                (using
                [[Page 44924]]
                the method of Watts et al., 2012) based on similarities in exposure
                characteristics. MNM mine categories include metal, nonmetal, stone,
                crushed limestone, and sand and gravel. All coal mines are categorized
                together as one commodity category.
                 Within each commodity, MSHA further separated mining operations
                into the four activity groups widely used by the industry: (1)
                development and production miners (drillers, stone cutters); (2) ore/
                mineral processing miners (crushing/screening equipment operators and
                kiln, mill, and concentrator workers in mine facilities); (3) miners
                engaged in load/haul/dump activities (conveyor, loader, and large
                haulage vehicle operators, such as dump truck drivers); and (4) miners
                in all other occupations (mobile and utility workers, such as
                surveyors, mechanics, cleanup crews, laborers, and operators of compact
                tractors and utility trucks).
                 Before determining the feasibility of reducing miners' exposure to
                respirable crystalline silica, MSHA gathered and analyzed information
                to understand current miner exposures by creating an ``exposure
                profile,'' identified the existing (i.e., baseline) conditions and the
                exposure levels associated with those conditions, and determined
                whether mines would need additional control methods, and if so, whether
                those methods were available.
                b. Exposure Profiles
                 MSHA classified all valid respirable crystalline silica samples in
                the Agency's MSIS data,\47\ grouping the data by commodity category,
                followed by activity group.\48\ MSHA created an exposure profile to
                better examine the sample data for each commodity category. These
                profiles include basic summary statistics, such as sample count, mean,
                median, and maximum values, presented as ISO 8-hour TWA values. They
                also show the sample distribution within the following exposure ranges:
                25 [mu]g/m\3\ to 50 [mu]g/m\3\ to
                100 [mu]g/m\3\ to 250 [mu]g/m\3\ to 500 [mu]g/m\3\.\49\
                ---------------------------------------------------------------------------
                 \47\ MSHA removed duplicate samples, samples missing critical
                information, and those identified as invalid by the mine inspector,
                for example because of a ``fault'' (failure) of the air sampling
                pump during the sampling period.
                 \48\ MSHA MSIS respirable crystalline silica data for the MNM
                industry, January 1, 2005, through December 31, 2019 (version
                20220812); MSHA MSIS respirable crystalline silica data for the Coal
                Industry, August 1, 2016, through July 31, 2021 (version 20220617).
                All samples were collected by mine inspectors and were of sufficient
                mass to be analyzed for respirable crystalline silica by MSHA's
                laboratory.
                 \49\ MSHA selected these ranges based on the proposed PELs under
                consideration, then multiples of 100 [mu]g/m\3\ to show how data are
                distributed in the higher ranges. Table VIII-5 also presents
                additional exposure ranges corresponding to the 85.7 [mu]g/m\3\
                concentration for coal samples.
                ---------------------------------------------------------------------------
                 In Table VIII-2, the respirable crystalline silica exposure data
                for MNM miners are summarized by commodity and for the MNM industry as
                a whole, while Table VIII-3 presents the exposure profile as the
                percentage of samples in each exposure range. Overall, approximately 82
                percent of the 57,769 MNM compliance samples were at or below the
                proposed PEL (50 [mu]g/m\3\). The exposure profile shows variability
                between the commodity categories: approximately 73 percent of metal
                miner exposures at or below the proposed PEL (50 [mu]g/m\3\) (the
                lowest among all MNM mines), compared with approximately 90 percent of
                the crushed limestone miner exposures (the highest among all MNM
                mines).
                 Table VIII-4 and Table VIII-5 present the corresponding respirable
                crystalline silica exposure information for coal miners by location
                (underground or surface). Overall, approximately 93 percent of the
                63,127 samples obtained by MSHA inspectors for coal miners were at or
                below the proposed PEL (50 [mu]g/m\3\). There was little variation
                between samples for underground miners and surface miners (with
                approximately 93 and 92 percent of the samples at or below 50 [mu]g/
                m\3\, respectively). Exposure values from the coal industry are
                expressed as ISO 8-hour TWAs, compatible with the proposed PEL.
                BILLING CODE 4520-43-P
                [[Page 44925]]
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                [[Page 44926]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.027
                [[Page 44927]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.028
                [[Page 44928]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.029
                c. Existing Dust Controls in Mines (Baseline Conditions)
                 MNM and coal mines are controlling dust containing respirable
                crystalline silica in various ways. As shown in Tables VIII-2 through
                VIII-5, respirable crystalline silica exposures exceeded the proposed
                PEL of 50 [mu]g/m\3\ in about 18 percent of all MNM samples collected.
                Of all coal samples, exposure levels exceeded the proposed PEL in about
                seven percent of the samples. Overall, metal mines and sand and gravel
                mines had higher exposure levels than other commodity mines.
                 Despite the extensive dust control methods available, dust control
                measures have been implemented in some commodity categories to a
                greater degree than in others. This is partly because some commodity
                categories tend to have larger mines. MSHA has found that the larger
                the amount (tonnage) of material a mine moves (including overburden and
                other waste rock), the faster the mine tends to operate its equipment
                (i.e., closer to the equipment capacity), creating more air turbulence
                and therefore generating more respirable crystalline silica. The amount
                of material moved also influences the number of miners employed at a
                mine, and therefore, the number of miners can be indirectly correlated
                to the amount of dust generated. MSHA has observed that in large mines,
                dusty conditions typically prompt more control efforts, usually in the
                form of added engineering controls.
                 MSHA has also found that metal mines, which are typically large
                operations with higher numbers of miners, tend to have available
                engineering controls for dust management. On the other hand, sand and
                gravel mines, which generally employ fewer miners and handle modest
                amounts of material, have very limited, if any, dust control measures.
                This is because most of the mined material is a commodity that only
                requires washing and screening into various sizes of product
                stockpiles, generating little waste material. Nonmetal, stone, and
                crushed limestone mines occupy the middle range in terms of employment,
                existing engineering controls, and maintenance practices.
                 Over the years, staff from multiple MSHA program areas have worked
                alongside miners and mine operators to improve safety and health by
                inspecting, evaluating, and researching mine conditions, equipment, and
                operations. These key programs, each of which has an onsite presence,
                include (but are not limited to) Mine Safety and Health Enforcement;
                Directorate of Educational Policy and Development which includes the
                National Mine Health and Safety Academy and the Educational Field and
                Small Mine Services; and the Directorate of Technical Support, which is
                comprised of the Approval and Certification Center and the Pittsburgh
                Safety and Health Technology Center (including its Health Field
                Division, National Air and Dust Laboratory, Ventilation Division, and
                other specialized divisions). Table VIII-6 reflects the collective
                observations of these MSHA programs, presented in terms of existing
                dust control (baseline conditions) and the classes of additional
                control measures that would provide those mines with the greatest
                benefit to reduce exposures below the proposed PEL and action level.
                 Table VIII-6 shows MSHA's assessment of existing dust controls in
                mines (baseline conditions) and additional controls needed to meet the
                proposed PEL for each commodity category, including the need for
                frequent scheduled maintenance. By conducting frequent scheduled
                maintenance, mine operators can reduce the concentration of respirable
                crystalline silica. Table VIII-6 shows that metal mines have adopted
                extensive dust controls, while sand and gravel mines tend to have
                minimal engineering controls, if any.
                [[Page 44929]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.030
                BILLING CODE 4520-43-C
                 Based on MSHA's experience, NIOSH research, and effective
                respirable dust controls currently available and in use in the mining
                industry, MSHA preliminarily finds that the baseline conditions include
                various combinations of existing engineering controls selected and
                installed by individual mines to address respirable crystalline silica
                generated during mining operations.
                d. Respirable Crystalline Silica Exposure Controls Available to Mines
                 Under the proposal, the mine operator must install, use, and
                maintain feasible engineering controls, supplemented by administrative
                controls, when necessary, to keep each miner's exposure at or below the
                proposed PEL. Engineering controls reduce or prevent miners' exposure
                to hazards.\50\ Administrative controls establish work practices that
                reduce the duration, frequency, or intensity of miners' exposures
                (although rotation of miners would be prohibited under the proposed
                rule).
                ---------------------------------------------------------------------------
                 \50\ Control measures that reduce respirable crystalline silica
                can also reduce exposures to other hazardous particulates, such as
                RCMD, metals, asbestos, and diesel exhaust. Operator enclosures and
                process enclosures also reduce hazardous levels of noise by creating
                a barrier between the operator and the noise source.
                ---------------------------------------------------------------------------
                 MSHA data and experience show that mine operators already have
                numerous engineering and administrative control options to control
                miners' exposures to respirable crystalline silica. These control
                options are widely recognized and used throughout the mining industry.
                NIOSH has extensively researched and documented engineering and
                administrative controls for respirable crystalline silica in mines. As
                noted previously, NIOSH has published a series on reducing respirable
                dust in mines (NIOSH, 2019b; NIOSH, 2021a).
                (1) Engineering controls
                 Examples of existing engineering controls used at mines and
                commercially available engineering controls that MSHA considered
                include:
                 Wetting or water sprays that prevent, capture, or redirect
                dust;
                 Ventilation systems that capture dust at its source and
                transport it to a dust collection device (e.g., filter or bag house),
                dilute dust already in the air, or ``scrub'' (cleanse) dust from the
                air in the work area;
                 Process enclosures that restrict dust from migrating
                outside of the enclosed area, sometimes used with an attached
                ventilation system to improve effectiveness (e.g., crushing equipment
                and associated dump hopper enclosure, with curtains and mechanical
                ventilation to keep dust inside);
                 Operator enclosures, such as mobile equipment cabs or
                control booths, which provide an environment with clean air for an
                equipment operator to work safely;
                 Protective features on mining process equipment to help
                prevent process failures and associated dust releases (e.g.,
                skirtboards on conveyors, which protect the conveyor system from damage
                and prevent material on the conveyor from falling off, which generates
                airborne dust);
                 Preventive maintenance conducted on engineering controls
                and mining equipment that can influence dust levels at a mine, to keep
                them functioning optimally; and
                 Instrumentation and other equipment to assist mine
                operators and miners in evaluating engineering control
                [[Page 44930]]
                effectiveness and recognizing control failures or other conditions that
                need corrective action.\51\
                ---------------------------------------------------------------------------
                 \51\ These instruments include dust monitors; water, air, and
                differential air pressure gauges; pitot tubes and air velocity
                meters; and video camera (NIOSH recommends software that pairs video
                with a dust monitor to track conditions that could lead to elevated
                exposures if not corrected). These instruments are discussed in
                NIOSH's best practices guides and dust control handbooks.
                ---------------------------------------------------------------------------
                (2) Administrative controls
                 Administrative controls include practices that change the way tasks
                are performed to reduce a miner's exposure. Administrative controls can
                be very effective and can even prevent exposure entirely. MSHA has
                preliminarily determined that various administrative controls are
                readily available to provide supplementary support to engineering
                controls. Examples of administrative controls would include
                housekeeping procedures; proper work positions of miners; walking
                around the outside of a dusty process area rather than walking through
                it; cleaning of spills; and measures to prevent or minimize
                contamination of clothing to help decrease miners' exposure to
                respirable crystalline silica. However, these control methods depend on
                human behavior and intervention and are less reliable than properly
                designed, installed, and maintained engineering controls. Therefore,
                administrative controls would be permitted only as supplementary
                measures, with engineering controls required as the primary means of
                protection. Nevertheless, administrative controls play an important
                role in reducing miners' exposure to respirable crystalline silica.\52\
                ---------------------------------------------------------------------------
                 \52\ Proposed paragraph 60.11(b) prohibits the use of rotation
                of miners as an administrative control used for compliance with this
                part.
                ---------------------------------------------------------------------------
                (3) Combinations of Controls
                 Various control options can also be used in combinations. NIOSH has
                documented in detail most control methods and has confirmed that they
                are currently used in mines, both individually and in combination with
                each other (2019b, 2021a).
                e. Maintenance
                 MSHA preliminarily finds that a strong and feasible preventive
                maintenance program plays an important role in achieving consistently
                lower respirable crystalline silica exposure levels. MSHA has observed
                that when engineering controls are installed and maintained in working
                condition, respirable dust exposures tend to be below the existing
                exposure limits. When engineering controls are not maintained, dust
                control efficiency declines and exposure levels rise. When engineering
                controls fail due to a lack of proper maintenance, a marked rise in
                exposures can occur, resulting in noncompliance with MSHA's existing
                exposure limits. Some examples of the impact that proper maintenance
                can have on respirable dust levels include:
                 Water spray maintenance: An experiment using water spray
                bars that could be turned on or off showed that dust reduction was less
                effective each time additional spray nozzles were deactivated. A 10
                percent decrease occurred when three of 21 sprays were shut off, but a
                50 percent decrease occurred when 12 out of the 21 sprays were shut
                off. Decreased total water spray volume and gaps in the spray pattern
                (due to deactivated nozzles) were both partially responsible for the
                decreased dust control (Seaman et al., 2020).
                 Water added to drill bailing air: When introduced into the
                drill hole (with the bailing air through a hollow drill bit), water
                mixes with and moistens the drill dust ejected from the hole and can
                reduce respirable dust by more than 90% (NIOSH 2021a, 2019b). NIOSH
                reports that this same control measure, and others, are similarly
                effective for MNM and surface coal mine drills preparing the blasting
                holes used to expose the material below (whether ore or coal).
                 Ventilation system maintenance: The amount of air cleaned
                by an air scrubber is decreased by up to one-third (33 percent) after
                one continuous mining machine cut. Cleaning the scrubber screens
                restores scrubber efficacy, but this maintenance must be performed
                after every cut. Spare scrubber screens make frequent cleaning
                practical without slowing production (NIOSH, 2021a).
                 Operator enclosure maintenance: Tests with mining
                equipment showed that maintenance activities including repairing
                weather stripping and replacing clogged and missing cab ventilation
                system filters (intake, recirculation, final filters) increased miner
                protection, by up to 95 percent (NIOSH 2019b, 2021a).
                 Filter selection during maintenance: Airflow is as
                important as filtration and pressurization in operator enclosures;
                during maintenance, filter selection can influence all three factors.
                Performing serial end-shift testing of enclosed cabs (on a face drill
                and a roof/rock bolter) at an underground crushed limestone mine, NIOSH
                compared installed HEPA filters and an alternative (MERV 16 filters).
                The latter provided an equal level of filtration and better overall
                miner protection by allowing greater airflow and cab pressurization. As
                an added advantage, NIOSH showed that these filters cost less and
                required less-frequent replacement, reducing maintenance expenses in
                this mining environment (Cecala et al., 2016; NIOSH 2021a,
                2019b).53 54
                ---------------------------------------------------------------------------
                 \53\ NIOSH believes this study, like many of its other mining
                studies on operator enclosures and surface drill dust controls, is
                relevant to both MNM mining and coal mining. NIOSH reports on this
                study, conducted at an underground limestone mine, in detail in both
                its Dust control handbook for industrial minerals mining and
                processing (second edition) (2019b) and its best practices for dust
                control in coal mining (second edition) (2021a).
                 \54\ Acronyms: High efficiency particulate air (HEPA). Minimum
                efficiency reporting value (MERV).
                ---------------------------------------------------------------------------
                 Proper design and installation--foundation for effective
                maintenance: A new replacement equipment operator enclosure (control
                booth) installed adjacent to the primary crusher at a granite stone
                quarry initially provided 50 to 96 percent respirable dust reduction,
                even with inadequate pressurization. The protection it offered miners
                tripled after the booth's second pressurization/filtration unit was
                activated (Organiscak et al., 2016).
                 MSHA has observed that when engineering controls are properly
                maintained, exposure levels decrease or stay low. Metal mines, which
                typically have substantial controls already installed, primarily need
                reliable preventive maintenance programs to achieve the proposed PEL.
                It is also important to repair equipment damage that contributes to
                dust exposure (for example, damage to conveyor skirtboards that protect
                the conveyor system from damage and prevent spillage which generates
                airborne dust). Maintenance and repair programs must ensure that dust
                control equipment is functioning properly.
                3. Feasibility Determination of Control Technologies
                 MSHA is proposing a PEL of 50 [mu]g/m\3\ for MNM and coal mines. As
                NIOSH has documented, the mining industry has a wide range of options
                for controlling dust exposure that are already in various
                configurations in mines (2019b; 2021a). NIOSH has carefully evaluated
                most of the dust controls used in the mining industry and found that
                many of the controls may be used in combinations with other control
                options. NIOSH has documented protective factors and exposure
                reductions of 30 to 90 percent or higher for many engineering and
                administrative controls.
                [[Page 44931]]
                 MSHA also preliminarily finds that maintaining (including
                adjusting) or repairing existing controls would help achieve exposures
                at or below 50 [mu]g/m\3\. For example, NIOSH found that performing
                maintenance on an operator enclosure can restore enclosure
                pressurization and reduce the respirable dust exposure of a miner by 90
                to 98.9 percent (e.g., by maintaining weather stripping, reseating or
                replacing leaking or clogged filters, and upgrading filtration) (NIOSH,
                2019b). When an equipment operator remains inside a well-maintained
                enclosure for a portion of a shift (for example 75 percent of an 8-hour
                shift), the cab can reduce the exposure of the operator proportionally,
                to a level of 50 [mu]g/m\3\ (or lower). This point is demonstrated by
                the following example involving a bulk loading equipment operator in a
                poorly maintained booth, exposed to respirable crystalline silica near
                the existing exposure limit (in the MNM sectors, 100 [mu]g/m\3\, as ISO
                8-hour TWA value; in the Coal sector, 85.7 [mu]g/m\3\ ISO, calculated
                as an 8-hour TWA). During the 25 percent of their shift (two hours of
                an eight-hour shift) that the operator was working in the poorly
                maintained enclosure, their exposure would continue to be 100 [mu]g/
                m\3\, while for the other six hours (operating mobile equipment with a
                fully refurbished protective cab), the exposure level would be 90
                percent lower, or 10 [mu]g/m\3\, resulting in an 8-hour TWA exposure of
                33 [mu]g/m\3\ for that miner's shift.\55\ Greater exposure reductions
                could also be achieved by repairing or replacing the poorly maintained
                enclosure, or modifying the miner's schedule so that the miner works
                seven hours, rather than six, inside of the well-maintained enclosure.
                ---------------------------------------------------------------------------
                 \55\ Calculating the exposure for the shift: 8-hour TWA = [(10
                [mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x 2 hours)]/8 hours = 33
                [mu]g/m\3\.
                ---------------------------------------------------------------------------
                 Other engineering controls (e.g., process enclosure, water dust
                suppression, dust suppression hopper, ventilation systems) could reduce
                dust concentrations in the area surrounding the poorly maintained
                enclosure, which would reduce the exposure of the operator inside. For
                example, if the poorly maintained enclosure was an open-air control
                booth (windows do not close) at a truck loading station, adding a dust
                suppression hopper (which reduces respirable dust exposure by 39 to 88
                percent during bulk loading) (NIOSH, 2019b), would lead to lower
                exposure during the two hours the miner was inside the open-air booth.
                The calculated respirable crystalline silica 8-hour TWA exposure of
                that miner could be reduced from 33 [mu]g/m\3\ (with improved operator
                enclosure alone) to 23 [mu]g/m\3\ (improved operator enclosure plus
                dust suppression hopper).\56\ As an added benefit, any helper or
                utility worker in the truck loading area would also experience reduced
                exposure.
                ---------------------------------------------------------------------------
                 \56\ Calculating the exposure with both the well-maintained
                operator enclosure (6 hours) and dust suppression hopper, assuming
                only the minimum documented respirable dust concentration reduction
                (39 percent): [(10 [mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x (1-
                0.39) x 2 hours)]/8 hours = 23 [mu]g/m\3\.
                ---------------------------------------------------------------------------
                 Similarly, considering an example for a coal miner helper who
                spends 90 minutes (1.5 hours) per 8-hour shift assisting a drilling rig
                operator (in a protective operator's cab) drilling blast holes. The
                combination of controls used to control drilling dust (including water
                added to the bailing air, which can reduce airborne respirable dust
                emissions by up to 96 percent) usually maintain the helper's respirable
                crystalline silica exposure in the range of 35 [mu]g/m\3\ (ISO) as an
                8-hour TWA. If, however, the drill's on-board water tank runs dry due
                to poor maintenance, the respirable crystalline silica concentration
                near the drill will rise by 95 percent, meaning that the concentration
                is 20 times greater than the usual level (NIOSH 2021a). If the drill
                operator idles the drill and calls for water resupply, the helper will
                not experience an elevated exposure. If instead the drill is operated
                dry for another 30 minutes until water resupply arrives, the helper
                will experience a respirable crystalline silica exposure of 77 [mu]g/
                m\3\ (ISO) as an 8-hour TWA. If dry drilling continued for 1.5 hours,
                the helper would have an exposure of 160 [mu]g/m\3\ ISO as an 8-hour
                TWA.\57\ After water is delivered, drill respirable dust emissions will
                return to their normal level once water is again introduced into the
                drill bailing air.
                ---------------------------------------------------------------------------
                 \57\ The 8-hour TWA exposure level of the helper, including the
                30-minute period of elevated exposure, is calculated as: [(35 [mu]g/
                m\3\ x 7.5 hours) + (35 [mu]g/m\3\ x 20 x 0.5 hours)]/8 hours = 77
                [mu]g/m\3\. Drill bits designed for use with water may need to be
                replaced sooner if used dry.
                ---------------------------------------------------------------------------
                 Based on these examples and the wide range of effective exposure
                control options available to the mining industry, MSHA preliminarily
                finds that control technologies capable of reducing miners' respirable
                crystalline silica exposures are available, proven, effective, and
                transferable between mining commodities; however, they must be well-
                designed and consistently used and maintained.
                a. Feasibility Findings for the Proposed PEL
                 Based on the exposure profiles in Table VIII-2 and Table VIII-3 for
                MNM mines, and in Table VIII-4 and VIII-5 for coal mines, and the
                examples in the previous section that demonstrate the beneficial effect
                of combined controls, MSHA preliminarily finds that the proposed PEL of
                50 [mu]g/m\3\ is technologically feasible for all mines.
                 Table VIII-7 summarizes the technological feasibility of control
                technologies available to the mining industry, by commodity. MSHA
                preliminarily finds that control technologies are technologically
                feasible for all six commodities and their respective activity groups.
                Under baseline conditions, mines in each commodity category have
                already achieved respirable crystalline silica exposures at or below 50
                [mu]g/m\3\ for most of the miners represented by MSHA's 57,769 samples
                for MNM miners and 63,127 samples for coal miners.
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                b. Feasibility Findings for the Proposed Action Level
                 MSHA believes that mine operators can achieve exposure levels at or
                below the proposed action level of 25 [mu]g/m\3\, for most miners by
                implementing additional engineering controls and more flexible and
                innovative administrative controls, in addition to the existing control
                methods already discussed in this technological feasibility analysis.
                MSHA notes that the exposure profiles in Table VIII-2 and Table VIII-3
                for MNM mines, and Table VIII-4 and VIII-5 for coal mines indicate that
                mine operators have already achieved the proposed action level for at
                least half of the miners who MSHA has sampled in each commodity
                category. However, to do so reliably for all miners, operators would
                need to upgrade equipment and facility designs, particularly in mines
                with higher respirable crystalline silica concentrations, that may be
                due to an elevated silica content in materials.
                 One control option would be increased automation, such as expanding
                the use of existing autonomous or remote-controlled drilling rigs, roof
                bolters, stone cutting equipment, and packaging/bagging equipment. This
                type of automation can reduce exposures by increasing the distance
                between the equipment operator and the dust source. Other options
                include completely enclosing most processes and ventilating the
                enclosures with dust extraction equipment or controlling the speed of
                mining equipment (e.g., longwall shearers, conveyors, dump truck
                emptying) and process equipment (e.g., crushers, mills) to reduce
                turbulence that increases dust concentrations in air. Additionally,
                where compatible with the material, exposure levels can be reduced by
                increased wetting to constantly maintain the material, equipment, and
                mine facility surfaces damp through added water sprays and frequent
                housekeeping (i.e., hosing down surfaces as often as necessary). In
                addition, vacuuming will minimize the amount of dust that becomes
                airborne and prevent dust that does settle on a surface from being
                resuspended in air.
                 Mines that only occasionally work with higher-silica-content
                materials may not be equipped with the controls required to achieve the
                proposed action level of 25 [mu]g/m\3\, or they may not currently have
                procedures to ensure miners are protected when they do work with these
                materials. Examples of these activities include cutting roof or floor
                rock with a continuous mining machine in underground coal mines;
                packaging operations that involve materials from an unfamiliar
                supplier, including another mine; and rebuilding or repairing kilns. To
                address these activities, under the proposed rule, mine operators would
                have to add engineering controls to address any foreseeable respirable
                crystalline silica overexposures. Examples of additional controls
                include pre-testing batches of new raw materials; improving hazard
                communication when batches of incoming raw materials contain higher
                concentrations of crystalline silica, and
                [[Page 44933]]
                augmenting enclosure and ventilation (e.g., adding ventilation to all
                crushing and screening equipment, increasing mine facility ventilation
                to 30 air changes per hour, and fully enclosing and ventilating all
                conveyor transfer locations). NIOSH (2019b, 2021a) describes all of the
                dust control methods described in this section, which are already used
                in mines, although to a less rigorous extent than would be necessary to
                reliably achieve exposure levels of 25 [mu]g/m\3\ or lower for all
                miners.
                 MSHA preliminarily finds that the proposed action level of 25
                [mu]g/m\3\ is technologically feasible for most mines. This finding is
                based on the exposure profiles, presented in Table VIII-2 and Table
                VIII-3 for MNM mines, and Table VIII-4 and VIII-5 for coal mines, which
                shows that within each commodity category, the exposure levels are at
                or below 25 [mu]g/m\3\ for at least half of the miners sampled. MSHA's
                finding is also based on the extensive control options documented by
                NIOSH, which can be used in combinations to achieve additional control
                of respirable crystalline silica. Although most mines would need to
                adopt and rigorously implement a number of the control options
                mentioned in this section, the technology exists to achieve this level
                and is already in use in mines.
                C. Technological Feasibility of Respiratory Protection (Within Proposed
                Part 60)
                 Under the proposed rule, respiratory protection would only be
                allowed for temporary, non-routine use. MSHA has preliminarily
                determined that it is technologically feasible to limit respirator use
                to temporary, non-routine activities based on the Agency's knowledge of
                and experience with the mining industry, evidence presented by NIOSH
                (2019b, 2020a), and Tables VIII-2 through VIII-5 (exposure profiles for
                MNM and coal mines). These tables indicate that the proposed PEL (50
                [mu]g/m\3\) has already been achieved for approximately 82 percent of
                the MNM miners and approximately 93 percent of the coal miners sampled
                by MSHA.
                 Proposed Sec. 60.14(b) requires that any miner unable to wear a
                respirator must receive a temporary job transfer to an area or to an
                occupation at the same mine where respiratory protection is not
                required. The proposed paragraph would also require that an affected
                miner continue to receive compensation at no less than the regular rate
                of pay in the occupation held by that miner immediately prior to the
                transfer. MNM mine operations have complied with the job transfer
                provisions under the existing standard in Sec. 57.5060(d)(7) that
                states miners unable to wear a respirator must be transferred to work
                in an existing position in an area of the mine where respiratory
                protection is not required. Proposed Sec. 60.14(b) is similar to these
                existing requirements. MSHA anticipates that mine operators would have
                a similar experience implementing the job transfer provisions of
                proposed Sec. 60.14(b). Therefore, MSHA preliminarily finds that the
                proposed requirement in Sec. 60.14(b) is technologically feasible.
                 For miners who would need to wear respiratory protection on a
                temporary and non-routine basis, proposed Sec. 60.14(c)(1) would
                require the mine operator to provide NIOSH-approved atmosphere-
                supplying respirators or NIOSH-approved air-purifying respirators
                equipped with high-efficiency particulate filters in one of the
                following NIOSH classifications under 42 CFR part 84: 100 series or
                High Efficiency (HE). As previously discussed, MSHA preliminarily finds
                that particulate respirators meeting these criteria would offer the
                best filtration efficiency (99.97 percent) and protection for miners
                exposed to respirable crystalline silica and are widely available and
                used by most industries. This finding is based on the suitability of
                the three particulate classifications for respirable size particle
                filtration and the broad commercial availability of these NIOSH-
                approved particulate respirators.\58\ NIOSH publishes a list of
                approved respirator models along with manufacturer/supplier
                information. In November 2022, the NIOSH-approved list contained 221
                records on atmosphere-supplying respirator models, 160 records on
                elastomeric respirators with P-100 classification, and 23 records on
                filtering facepiece respirators with P-100 classification (NIOSH, 2022
                list P-100 elastomeric, P-100 filtering facepiece, and atmosphere-
                supplying respirator models).\59\ Based on this information, MSHA
                preliminarily finds that proposed Sec. 60.14(c)(1) is technologically
                feasible.
                ---------------------------------------------------------------------------
                 \58\ Class 100 particulate respirators (currently the most
                widely used respirator filter specification in the U.S.) are
                available from numerous sources including respirator manufacturers,
                online safety supply companies, mine equipment suppliers, and local
                retail hardware stores.
                 \59\ The NIOSH list of approved models does not guarantee that
                each model is currently manufactured. However, the list does not
                include obsolete models, and the more popular models are widely
                available, including in bulk quantities.
                ---------------------------------------------------------------------------
                 Proposed Sec. 60.14(c)(2) would incorporate the ASTM F3387-19
                ``Standard Practice for Respiratory Protection'' to ensure that the
                most current and protective respiratory protection practices would be
                implemented by operators who temporarily use respiratory protection to
                control miners' exposures to respirable crystalline silica. The Agency
                is also incorporating this respiratory protection consensus standard
                under Sec. Sec. 56.5005, 57.5005, and 72.710. This proposed update is
                also addressed in the next section (see Technological feasibility of
                updated respiratory protection standards). Based on the information
                contained in that section, MSHA preliminarily finds that the proposed
                Sec. 60.14(c)(2) is technologically feasible.
                 Based on information contained in this section, MSHA preliminarily
                finds that proposed Sec. 60.14 is technologically feasible.
                D. Technological Feasibility of Updated Respiratory Protection
                Standards (Amendments to 30 CFR Parts 56, 57, and 72)
                1. Incorporation by Reference
                 Respirators are commonly used by miners as a means of protection
                against a multitude of respiratory hazards, including particulates,
                gases, and vapors. Respirators are needed in immediately life-
                threatening (i.e., IDLH) situations as well as operations where
                engineering controls and administrative controls do not provide
                sufficient protection against respiratory hazards. Where respirators
                are used, they must seal and isolate the miner's respiratory system
                from the contaminated environment. The risk that a miner will
                experience an adverse health effect from a contaminant when relying on
                respiratory protection is a function of the toxicity or hazardous
                nature of the air contaminants present, the concentrations of the
                contaminants in the air, the duration of exposure, and the degree of
                protection provided by the respirator. When respirators fail to provide
                the proper protection, there is an increased risk of adverse health
                effects. Therefore, it is critical that respirators perform as they are
                designed.
                 Accordingly, MSHA is proposing to incorporate by reference ASTM
                F3387-19 under 30 CFR 56.5005, 30 CFR 57.5005, and 30 CFR 72.710. With
                this action, the Agency intends to assist mine operators in developing
                effective respiratory protection practices and programs that meet
                current industry standards. This proposed revision would better protect
                miners who temporarily wear respiratory protection.
                 The American National Standards Practices for Respiratory
                Protection ANSI Z88.2-1969 is currently incorporated by reference in 30
                CFR 56.5005, 30 CFR 57.5005, and 30 CFR
                [[Page 44934]]
                72.710.\60\ Since MSHA issued these standards, respirator technology
                and knowledge on respirator protection have advanced and as a result,
                changes in respiratory protection standard practices have occurred.
                ASTM F3387-19 is based on the most recent consensus standard and
                provides more comprehensive and detailed guidance. MSHA believes that
                most mines that use respiratory protection are already following
                current respiratory protection practices and standards such as ANSI/
                ASSE Z88.2--2015 ``Practices for Respiratory Protection'' standard, its
                similar ASTM replacement (the F3387-19 standard), or OSHA 29 CFR
                1910.134--Respiratory protection. ASTM F3387-19 standard practices are
                substantially similar to the standard practices included in ANSI/ASSE
                Z88.2-2015 or OSHA's respiratory standards.
                ---------------------------------------------------------------------------
                 \60\ ASTM 3387-19 is the revised version of ANSI/ASSE Z88.2-
                2015. In 2017, the Z88 respirator standards were transferred from
                ANSI/ASSE to ASTM International (source: F3387-19, Appendix XI).
                ---------------------------------------------------------------------------
                2. Availability of Respirators
                 The updated respiratory protection standard reflects current
                practice at many mines that currently use respiratory protection and
                does not require the use of new technology. Thus, MSHA preliminarily
                finds that the proposed update is technologically feasible for affected
                mines of all sizes.
                3. Respiratory Protection Practices
                 By incorporating the updated respiratory protection consensus
                standard (ASTM F3387-19), MSHA intends that mine operators would
                develop effective respiratory protection practices that meet the
                updated consensus standard and that would better protect miners from
                respirable hazards not yet controlled by other methods.
                 MSHA presumes that most mines with respiratory protection programs,
                and particularly those MNM mines that have operations under both MSHA
                and OSHA jurisdiction, are already following either the ANSI/ASSE
                Z88.2--2015 standard, the ASTM F3387-19 standard, or OSHA 1910.134. The
                respiratory protection program elements under ASTM F3387-19 are largely
                similar to those in the existing standard.
                 MSHA expects that some operators may need to adjust their current
                respiratory protection practices and standard operating procedures to
                reflect ASTM F3387-19 standard practices. Examples of adjustments
                include formalizing fit testing and respirator training annually;
                updating the training qualifications of respirator trainers, managers,
                supervisors, and others responsible for the respiratory protection
                program; reviewing the information exchanged with the physician or
                other licensed health care professional (PLHCP); and formalizing
                internal and external respiratory protection program reviews or audits.
                 Overall, MSHA preliminarily finds that the proposed amendments to
                existing parts 56, 57, and 72 are technologically feasible because the
                requirements of ASTM F3378-19 are already implemented at some mines.
                E. Technological Feasibility of Medical Surveillance (Within Proposed
                Part 60)
                 Under the proposed rule, mine operators would be required to
                provide periodic medical examinations for each MNM miner, at no cost to
                the miner. The proposed medical surveillance standards would extend to
                MNM miners similar protections available to coal miners under 30 CFR
                72.100. The requirements in proposed Sec. 60.15 are consistent with
                the Mine Act's mandate to provide maximum health protection for miners.
                 Under the proposed standards, MNM miners new to the mining industry
                would receive an initial examination, within 30 days. If they are not
                new to mining, they are categorized as belonging to a group of workers
                who are eligible for an examination every 5 years. Workers who are new
                to mining, after they have their initial examination, would be provided
                another follow-up examination within 3 years. If the 3-year follow-up
                examination indicates any medical concerns associated with chest X-ray
                findings or decreased lung function, these miners are eligible to have
                another follow-up exam in 2 years. After this additional 2-year follow-
                up exam, or if the 3-year follow-up examination indicates no medical
                concerns associated with chest X-ray findings or decreased lung
                function, these miners will enter the category of miners eligible for
                periodic 5-year exams.
                 MSHA is proposing that medical examinations would be performed by a
                PLHCP or specialist. A medical examination would include a review of
                the miner's medical and work history and physical examination. The
                medical and work history would cover a miner's present and past work
                exposures, illnesses, and any symptoms indicating respirable
                crystalline silica-related diseases and compromised lung function. The
                medical examination would include a chest X-ray. The required chest X-
                ray would be required to be classified by a NIOSH-certified B Reader,
                in accordance with the Guidelines for the Use of the International
                Labour Office (ILO) International Classification of Radiographs of
                Pneumoconioses. The ILO recently made additional standard digital
                radiographic images available and has published guidelines on the
                classification of digital radiographic images (ILO 2022). These
                guidelines provide standard practices for detecting changes of
                pneumoconiosis, including silicosis, in chest X-rays. The proposed rule
                would also require spirometry test be part of the medical examination.
                 MSHA has preliminarily determined that it is technologically
                feasible for MNM mine operators to provide periodic examinations. The
                procedures required for initial and periodic medical examination are
                commonly conducted in the general population (i.e., medical history,
                physical examination, chest X-ray, spirometry test) by a wide range of
                practitioners with varying medical backgrounds. Because the proposed
                medical examinations consist of procedures conducted in the general
                population and because MSHA would be giving MNM mine operators maximum
                flexibility in selecting a PLHCP who would be able to offer these
                services, MSHA anticipates that operators would not experience
                difficulty in finding PLHCPs who are licensed to provide these
                services.
                 In addition, in the case of classifying chest X-rays, MSHA has
                preliminarily determined that the availability of digital X-ray
                technology allows for electronic submission to remotely located B
                Readers for interpretation; therefore, MSHA anticipates that the
                limited number of B Readers in certain geographic locations would not
                be an obstacle for MNM operators. Overall, MSHA preliminarily finds
                that the proposed medical surveillance provisions are technologically
                feasible.
                F. Conclusions
                 Based on MSHA's technological feasibility analysis, MSHA has
                determined that all elements of the proposed rule on Lowering Miners'
                Exposure to Respirable Crystalline Silica and Improving Respiratory
                Protection are technologically feasible.
                IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory
                Alternatives
                A. Introduction
                 Executive Orders (E.O.s) 12866 and 13563 direct agencies to assess
                all costs and benefits of available regulatory alternatives and, if
                regulation is
                [[Page 44935]]
                necessary, to select regulatory approaches that maximize net benefits
                (including potential economic, environmental, public health and safety
                effects, distributive impacts, and equity). E.O. 13563 emphasizes the
                importance of quantifying both costs and benefits, of reducing costs,
                of harmonizing rules, and of promoting flexibility. E.O.s 12866 and
                13563 require that regulatory agencies assess both the costs and
                benefits of regulations.
                 A regulatory action is considered ``significant'' if it is likely
                to ``have an annual effect on the economy of $200 million or more . .
                .'' under E.O. 12866 Section 3(f)(1), as amended by E.O. 14094. The
                proposed rule ``Lowering Miners' Exposure to Respirable Crystalline
                Silica and Improving Respiratory Protection'' is a significant rule. To
                comply with E.O.s 12866 and 13563, MSHA has prepared a standalone PRIA
                for this proposed rule. A summary of the PRIA is presented below. The
                standalone PRIA contains detailed supporting data and explanation for
                the summary materials presented here, including the mining industry,
                costs and benefits, and economic feasibility. The standalone PRIA can
                be accessed electronically at http://www.msha.gov and has been placed
                in the rulemaking docket at www.regulations.gov, docket number MSHA-
                2023-0001. MSHA requests comments on all estimates of costs and
                benefits presented in this PRIA and on the data, assumptions, and
                methodologies the Agency used to develop the cost and benefit
                estimates.
                B. Miners and Mining Industry
                 The proposed rule would affect mine operators and miners. This
                section provides information on the structure of the Metal/Nonmetal
                (MNM) and coal mining industries, including the revenue, number,
                employment by commodity and size; economic characteristics of MNM and
                coal mines; and the respirable crystalline silica exposure profiles for
                miners across different occupations in the MNM and coal industry. The
                data come from the U.S. Department of the Interior (DOI), U.S.
                Geological Survey (USGS); U.S. Department of Labor (DOL), Mine Safety
                and Health Administration (MSHA), Educational Policy and Development
                and Program Evaluation and Information Resources; the Statistics of US
                Businesses (SUSB); and the Energy Information Administration (EIA).
                1. Structure of the Mining Industry
                 The mining industry can be divided into two major sectors based on
                commodity: (1) Metal/Nonmetal mines (hereafter referred to as MNM
                mines) and (2) coal mines with further distinction made regarding type
                of operation (e.g., underground coal mines or surface coal mines). The
                MNM mining sector is made up of metal mines (copper, iron ore, gold,
                silver, etc.) and nonmetal mines. Nonmetal mines can be categorized
                into four commodity groups: (1) nonmetal (mineral) materials such as
                clays, potash, soda ash, salt, talc, and pyrophyllite; (2) sand and
                gravel, including industrial sand; (3) stone including granite,
                limestone, dolomite, sandstone, slate, and marble; and (4) crushed
                limestone.
                 MSHA categorizes mines by size based on employment. For purposes of
                this industry profile, MSHA has categorized mines into the following
                four groups for analytical purposes \61\--mines that employ: (1) 1-20
                miners (Emp https://www.msha.gov/sites/default/files/Support_Resources/Forms/7000-2_0.pdf.
                ---------------------------------------------------------------------------
                 MSHA tracks mine characteristics and maintains a database
                containing the number of mines by commodity and size, number of
                employees, and employee hours worked. MSHA also collects data on the
                number of mining contractors, their employees, and employee hours.
                While contractors are issued a unique MSHA contractor identification
                number, they may work at any mine.
                 Table IX-1 presents an overview of the mining industry, including
                the number of MNM and coal mines, their employment, excluding
                contractors, and revenues by commodity and size. All data are current
                in reference to the year 2019. In 2019, the MNM mining sector of 11,525
                mines employed 169,070 individuals, of which 150,928 were miners and
                18,142 were office workers. There were 1,106 coal mines that reported
                production and that employed 52,966 individuals, of which 51,573 were
                miners and 1,393 were office workers.
                BILLING CODE 4520-43-P
                [[Page 44936]]
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                BILLING CODE 4520-43-C
                a. Metal Mining
                 There are 24 groups of metal commodities mined in the U.S. Metal
                mines, which represent about 2.4 percent (280 out of 11,525) of all MNM
                mines and employ roughly 24.5 percent of all MNM miners. Of these 280
                mines, 157 employ 20 or fewer miners and 22 employ greater than 500
                miners. Additionally, the 2019 MSHA data show that there are a total of
                13,792 contract miners in the metal mining industry.
                b. Non-Metal (Mineral) Mining
                 Thirty-five non-metal commodities are mined in the U.S., not
                including stone, and sand and gravel. Non-metal mines represent about
                7.8 percent of all MNM mines and employ roughly 15 percent of all MNM
                miners. The majority of non-metal mines (71.9 percent) employ fewer
                than 20 miners and less than 1 percent employ more than 500 employees.
                In 2019, there were 11,346 contract miners in the non-metal mining
                industry.
                c. Stone Mining
                 The stone mining subsector includes eight different stone
                commodities. Seven of the eight are further classified as either
                dimension stone or crushed and broken stone. Stone mines make up 20.9
                percent of all MNM mines and employ 23.4 percent of all MNM miners. The
                majority of these mines (83.1 percent) employ less than 20 miners. In
                2019, there were 18,559 contract miners in the stone mining industry.
                [[Page 44937]]
                d. Crushed Limestone
                 Crushed limestone mines make up 16.2 percent of all MNM mines and
                employ about the same percentage (16.0 percent) of all MNM miners. Of
                the 1,862 crushed limestone mines, 83.5 percent employ fewer than 20
                miners, and there are no crushed limestone mines that employ over 500
                miners. In 2019, there were 9,605 contract miners in the crushed
                limestone mining industry.
                e. Sand and Gravel Mining
                 Sand and gravel mines account for 52.7 percent of all MNM mines and
                employ 21.1 percent of all MNM miners. Nearly all (96.7 percent) of
                these mines employ fewer than 20 employees. In 2019, MSHA data show
                that there were 7,512 contract miners in the sand and gravel mining
                industry.
                f. Coal
                 In the coal sector, 707 mines (63.9 percent) employed fewer than 20
                miners. Overall, coal mine employment in 2019 was 52,966, of which
                51,573 were miners and the remaining 1,393 were office workers.
                Additionally, there were a total of 22,003 contract miners in the coal
                mining industry in 2019.
                2. Economic Characteristics of the Metal/Non-Metal Mining Industry
                 The value of all MNM mining output in 2019 was estimated at $83.8
                billion (U.S. Department of Interior, 2019). Metal mines, which include
                iron, gold, copper, silver, nickel, lead, zinc, uranium, radium, and
                vanadium mines, contributed $26.9 billion. In the USGS Mineral
                Commodity Summaries, nonmetals, stone, sand and gravel, and crushed
                limestone are combined in to one commodity group called industrial
                minerals. MSHA estimated the production value of each individual
                commodity by applying the proportion of revenues represented by each
                among all commodities in the SUSB and applying that proportion to the
                2019 production value for all industrial minerals reported by USGS.
                This approach yielded the following estimates: metal production was
                valued at $26.9 billion, non-metal production at $22.3 billion, stone
                mining at $12.85 billion, sand and gravel at $9.0 billion, and crushed
                limestone at $12.7 billion.
                 Production in the U.S. coal sector amounted to 706.1 million tons
                in 2019.\62\ To estimate coal revenues in 2019, MSHA combined
                production estimates with prices per ton. Mine production data was
                taken from MSHA quarterly data and the coal price per ton was taken
                from the 2019 EIA Annual Coal Report. As shown in Table IX-1, total
                coal revenues in 2019 equaled $25.6 billion.
                ---------------------------------------------------------------------------
                 \62\ Source: MSHA MSIS Data (reported on MSHA Form 7000-2).
                ---------------------------------------------------------------------------
                 The U.S. coal mining sector produces three major types of coal:
                bituminous, lignite, and anthracite. According to MSHA data, bituminous
                operations account for approximately 92.1 percent of total coal
                production in short tons, and 91.9 percent of all coal miners. Lignite
                operations account for roughly 7.5 percent of total coal production and
                6.2 percent of coal miners. Anthracite operations account for 0.4
                percent of coal production and 1.9 percent of coal miners.
                C. Cost-Benefit Analysis
                 The PRIA is based on MSHA's Preliminary Risk Analysis and the
                Technological Feasibility analysis. The PRIA presents estimated
                benefits and costs of the proposed rule for informational purposes
                only. Under the Mine Act, MSHA is not required to use estimated net
                benefits as the basis for its decision. MSHA requests comments on the
                methodologies, baseline, assumptions, and estimates presented in the
                PRIA and also asks for any data or quantitative information that may be
                useful in evaluating the estimated costs and benefits associated with
                the proposed rule. The PRIA assesses the costs and benefits in the MNM
                and coal industries of reducing miners' exposures to silica to 50
                [mu]g/m\3\ for a full shift, calculated as an 8-hour time weighted
                average (TWA) and of complying with the standard's ancillary
                requirements. The PRIA also assesses the costs and benefits from
                requiring medical surveillance of MNM miners. It also assesses the
                costs and benefits from revising the existing respiratory protection
                standards. MSHA is proposing to incorporate by reference ASTM F3387-19,
                ``Standard Practice for Respiratory Protection'' (ASTM F3387-19). ASTM
                F3387-19 would replace the 1969 American National Standards Institute
                (ANSI) ``Practices for Respiratory Protection.''
                 MSHA estimates the proposed rule would have an annualized cost of
                $57.6 million in 2021 dollars at a real discount rate of 3 percent. Of
                this cost, over 55 percent is attributable to exposure monitoring; 30
                percent to medical surveillance; 10 percent to engineering, improved
                maintenance and repair, and administrative controls; 2.4 percent
                related to the selection, use, and maintenance of approved respirators
                in accordance with ASTM F3387-19, respiratory protection practices; and
                1.8 percent to additional respiratory protection (e.g., when miners
                need temporary respiratory protection from exposure at the proposed PEL
                when it would not have been necessary at the existing PEL). MSHA
                further estimates that the MNM sector will incur $52.7 million (91
                percent), and the coal sector will incur $4.9 million (9 percent) in
                annualized compliance costs (see Table IX-2).
                BILLING CODE 4520-43-P
                [[Page 44938]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.033
                 In its analysis, MSHA annualizes all costs using 3 percent and 7
                percent discount rates as recommended by OMB. MSHA bases the
                annualization periods for expenditures on equipment life cycles and
                primarily uses a 10-year annualization period for one-time costs and
                20-year for medical surveillance. However, MSHA annualizes the benefits
                of the proposed rule over a 60-year period to reflect the time needed
                for benefits to reach the steady-state values projected in MSHA's PRA.
                Therefore, MSHA's complete analysis of this rule is 60 years (which
                corresponds to 45 years of working life and 15 years of retirement for
                the current miner population). MSHA holds the employment and production
                constant over this period for purposes of the analysis.\63\
                ---------------------------------------------------------------------------
                 \63\ This modeling strategy implicitly assumes that the ten-year
                cost annualization repeats five more times to cover the same 60-year
                analytic period as the benefits model. Thus, one-time costs incurred
                in the first year implicitly repeat in years 11, 21, 31, 41 and 51.
                This may introduce a tendency toward overestimation of compliance
                costs.
                ---------------------------------------------------------------------------
                 For both MNM and coal mines, the estimated costs to comply with the
                proposed PEL (50 [mu]g/m\3\), assumes that all mines are compliant with
                the existing PEL of 100 [mu]g/m\3\ for MNM mines (for a full shift,
                calculated as an 8-hour TWA) and 85.7 [mu]g/m\3\ for coal mines (for a
                full shift, calculated as an 8-hour TWA).
                 MSHA estimates that:
                 [ssquf] The proposed respirable crystalline silica rule will result
                in a total of 799 lifetime avoided deaths (63 in coal and 736 in MNM
                mines) and 2,809 lifetime avoided morbidity cases (244 in coal and
                2,566 in MNM mines) once it is fully effective (i.e., beginning 60
                years post rule promulgation through year 120 such that all miners,
                working and retired, have been exposed only under the proposed PEL)
                (see Table IX-3).
                 [ssquf] Over the first 60 years, annual cases avoided will increase
                gradually to the steady-state values (i.e., long-run per-year
                averages). Upon reaching the steady-state values, annual cases avoided
                will be constant from year 60 onward because all miner cohorts will
                have identical lifetime risks. From Table IX-4, in the first 60 years,
                the proposed rule would result in a total of 410 avoided deaths (377 in
                MNM and 33 in Coal) and 1,420 avoided morbidity cases (1,298 in MNM and
                122 in Coal), which are the benefits MSHA monetized in its benefits
                analysis.
                 [ssquf] The total benefits of the proposed respirable crystalline
                silica rule from these avoided deaths and morbidity cases are $175.7
                million per year in 2021 dollars.
                --The majority (60.7 percent) of these benefits ($108.0 million) are
                attributable to avoided mortality due to non-malignant respiratory
                disease (NMRD) ($52.8 million), silicosis ($28.1 million), and end-
                stage renal disease (ESRD) ($19.9 million), and lung cancer ($7.2
                million).
                --Benefits from avoided morbidity due to silicosis are $53.2 million
                per year: $48.7 million for MNM mines and $4.6 million for coal mines
                (see Table IX-5).
                --Benefits from avoided morbidity that precedes fatal cases associated
                with NMRD, silicosis, renal disease, and lung cancer, are $14.5
                million: $13.3 million for MNM mines and $1.2 million for coal mines
                (see Table IX-5).
                [[Page 44939]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.034
                [GRAPHIC] [TIFF OMITTED] TP13JY23.035
                [[Page 44940]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.036
                 MSHA acknowledges that its benefit estimates are influenced by the
                underlying assumptions and that the long-time frame of this analysis
                (first 60 years) is a source of uncertainty. The main assumptions
                underlying these estimates of avoided mortality and morbidity include
                the following:
                 [ssquf] Employment and production are held constant over the 60
                years--the analysis period of the proposed rule.\64\
                ---------------------------------------------------------------------------
                 \64\ MSHA recognizes that it is impossible to predict economic
                factors over such a long period. Given known information and
                forecast limitations, MSHA believes this is a reasonable assumption.
                ---------------------------------------------------------------------------
                 [ssquf] Any miners currently exposed above the existing PELs are
                exposed to levels of respirable crystalline silica at existing
                standards (100 [mu]g/m\3\ for a full-shift exposure, calculated as an
                8-hour TWA at MNM mines and 85.7 [mu]g/m\3\ for a full-shift exposure,
                calculated as an 8-hour TWA at coal mines).
                 [ssquf] The proposed rule will result in miners being exposed at or
                below the proposed PEL (50 [mu]g/m\3\).
                 [ssquf] Miners have identical employment and hence exposure tenures
                (45 years). The assumptions inherent in developing the exposure-
                response functions for the modeled health outcomes are reasonable
                throughout the exposure ranges relevant to this benefits analysis. In
                the final rule, the agency plans to augment the Regulatory Impact
                Analysis, for informational purposes, so as to incorporate different
                durations of working life based on exposure information, while
                continuing to also present calculations based on a 45-year working life
                assumption.
                 In addition to the above quantified health benefits of the lower
                PEL, MSHA projects that there would be additional benefits from
                requiring approved respirators be selected, used, and maintained in
                accordance with the requirements, as applicable, of ASTM F3387-19. The
                ASTM standard reflects developments in respiratory protection since
                MSHA issued its existing standards. These developments include OSHA's
                research and rulemaking on respiratory protection. Under the proposed
                rule, MSHA would require operators' respiratory protection plans to
                include minimally acceptable respiratory program elements: program
                administration; standard operating procedures (SOPs); medical
                evaluation; respirator selection; training; fit testing; and
                maintenance, inspection, and storage. Given the uncertainty about the
                current state of operator respiratory protection practices, MSHA did
                not quantify the benefits that would be realized by requiring approved
                respirators to be selected, used, and maintained in accordance with
                ASTM F3387-19.
                 MSHA believes the proposed rule would lower exposures to respirable
                crystalline silica and respirable coal mine dust. The available
                exposure-response models do not account for separate health effects
                from exposure to mixed dust that contains both respirable crystalline
                silica and coal mine dust. However, MSHA anticipates that there would
                be additional unquantified benefits provided by the proposed rule--
                reduced adverse health outcomes attributable to respirable coal mine
                dust exposure, such as CWP.\65\ The proposed rule does quantify the
                benefits of avoided deaths and illnesses from reducing coal miners'
                exposures to respirable crystalline silica. Among coal miners, MSHA
                estimates 35 lifetime avoided deaths and illnesses from NMRD (see Table
                IX-3).
                ---------------------------------------------------------------------------
                 \65\ The following references document miner exposures that
                could be simultaneously below the PEL for RCMD but exceed the PEL
                for silica: Rahimi, E., Shekarian, Y., Shekarian, N. et al.
                Investigation of respirable coal mine dust (RCMD) and respirable
                crystalline silica (RCS) in the U.S. underground and surface coal
                mines. Sci Rep 13, 1767 (2023). https://doi.org/10.1038/s41598-022-24745-x.
                 Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G,
                Laney AS. Respirable coal mine dust in underground mines, United
                States, 1982-2017. Am J Ind Med. 2019 Jun;62(6):478-485. doi:
                10.1002/ajim.22974. Epub 2019 Apr 29. PMID: 31033017; PMCID:
                PMC6800046.
                 Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G,
                Laney AS. Respirable coal mine dust at surface mines, United States,
                1982-2017. Am J Ind Med. 2020 Mar;63(3):232-239. doi: 10.1002/
                ajim.23074. Epub 2019 Dec 9. PMID: 31820465; PMCID: PMC7814307.
                ---------------------------------------------------------------------------
                 Finally, MSHA also expects that the proposed rule's medical
                surveillance provisions would reduce mortality and morbidity from
                respirable crystalline silica exposure among MNM miners. The initial
                mandatory examination that assesses a new miner's baseline pulmonary
                status, coupled with periodic examinations, would assist in the early
                detection of respirable crystalline silica related illnesses. Early
                detection of illness often leads to early intervention and treatment,
                which may slow disease progression and/or
                [[Page 44941]]
                improve health outcomes. However, as noted, MSHA lacks data to quantify
                these additional benefits.
                 The net benefits of the proposed rule are the differences between
                the estimated benefits and costs. Table IX-6 shows estimated net
                benefits using alternative discount rates of 0, 3, and 7 percent for
                benefits and costs. As is observed from the table, the choice of
                discount rate has a significant effect on annualized costs, benefits,
                and hence net benefits. While the net benefits of the proposed
                respirable crystalline silica rule vary considerably depending on the
                choice of discount rate used to annualize costs and benefits, total
                benefits exceed total costs under each discount rate considered. MSHA's
                estimate of the net annualized benefits of the proposed rule, using a
                uniform discount rate for both costs and benefits of 3 percent, is
                $118.2 million a year with the largest share ($108.8 million; 92.0
                percent) attributable to the MNM sector.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.037
                D. Economic Feasibility
                 To establish economic feasibility, MSHA uses a revenue screening
                test--whether the yearly costs of a rule are less than 1 percent of
                revenues, or are negative (i.e., provide net cost savings)--to
                presumptively establish that compliance with the regulation is
                economically feasible for the mining industry. The resulting ratio of
                annualized compliance costs to revenues from the screener analysis
                should be interpreted with care. If annualized compliance costs
                comprise less than 1 percent of revenue, the Department of Labor
                presumes that the affected entities can incur the compliance costs
                without significant economic impacts.
                 For the MNM and coal mining sectors, MSHA estimates the projected
                impacts of the rule by calculating the average annualized compliance
                costs for each sector as a percentage of total revenues. To be
                consistent with costs that are calculated in 2021 dollars, MSHA first
                inflated mine revenues expressed in 2019 to their 2021 equivalent using
                the GDP Implicit Price Deflator. Due to inflation, the nominal value of
                a dollar in 2021 is estimated to be about 5.4 percent higher than in
                2019.
                [[Page 44942]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.038
                 Table IX-8 presents the projected impacts of the proposed rule. The
                table compares aggregate annualized compliance costs for MNM and coal
                sectors at a 0 percent, 3 percent, and 7 percent real discount rate to
                total annual revenues. At a 3 percent real discount rate, total
                aggregate annualized compliance costs are projected to be $57.6 million
                (including both 30 CFR part 60 and 2019 ASTM Upgrade Costs), while
                aggregate revenues are estimated to be $115.3 billion in 2021 dollars.
                Thus, the mining industry is expected to incur compliance costs that
                comprise 0.05 percent of total revenues.
                 For the MNM sector, MSHA estimates that the annualized costs of the
                proposed rule (including ASTM update costs) would be $52.7 million at 3
                percent discount rate, which is approximately 0.06 percent of total
                annual revenue of $88.3 billion ($52.7 million/$88.3 billion) for MNM
                mine operators. For the coal sector, MSHA estimates that the annualized
                cost of the proposed rule would also be $4.9 million at 3 percent,
                which is approximately 0.02 percent of total annual revenue of $27.0
                billion ($4.9 million/$27.0 billion) for coal mine operators.
                 The ratios of screening analysis are well below the 1.0 percent
                threshold, and therefore, MSHA has concluded that the requirements of
                the proposed rule are economically feasible, and no sector of the
                industry will likely incur significant costs.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.039
                E. Regulatory Alternatives
                 The proposed rule presents a comprehensive approach for lowering
                miners' exposure to respirable crystalline silica. The proposal
                includes the following regulatory provisions: lowering miners'
                respirable crystalline silica exposure to a PEL of 50 [mu]g/m\3\ for a
                full-shift exposure, calculated as an 8-hour TWA; initial baseline
                sampling for miners who are reasonably expected to be exposed to
                respirable crystalline silica; periodic sampling for miners who are at
                or above the proposed action level of 25 [mu]g/m\3\ but at or below the
                proposed PEL of 50 [mu]g/m\3\; and semi-annual evaluation of changing
                mining processes that would reasonably be expected to result in new or
                increased exposures.
                 In developing the proposed rule, MSHA considered two regulatory
                alternatives. Both alternatives include less stringent monitoring
                provisions than the proposed monitoring provisions. One of the
                alternatives also combines less stringent monitoring with a more
                stringent PEL. MSHA discusses the regulatory options in the sections
                below, from least expensive to most expensive. Both alternatives would
                retain the respiratory protection updates and medical surveillance from
                the proposed rule.
                1. Regulatory Alternative #1: Changes in Sampling and Evaluation
                Requirements
                 Under this alternative, the proposed PEL would remain unchanged at
                50 [mu]g/m\3\ and the proposed action level would remain unchanged at
                25 [mu]g/m\3\. Further, mine operators would conduct: (1) baseline
                sampling for miners who may be exposed to respirable crystalline silica
                at or above the proposed action level of 25 [mu]g/m\3\, (2) periodic
                sampling twice per year for miners who are at or above the proposed
                action level of 25 [mu]g/m\3\ but at or below the proposed PEL of 50
                [mu]g/m\3\, and (3) annual evaluation of changing mining processes or
                conditions that would reasonably be
                [[Page 44943]]
                expected to result in new or increased exposures.
                 Mine operators would be required to undertake sampling under this
                regulatory alternative and would thus incur compliance costs. However,
                monitoring requirements under this alternative are less stringent than
                the requirements under the proposed rule because the number of miners
                to be sampled for baseline sampling would be smaller than in the
                proposed rule and the frequency of periodic sampling and evaluations of
                changing mining processes or conditions are set at half the frequency
                of the proposed monitoring requirements. Therefore, the cost of
                compliance will be lower under this alternative. MSHA estimates that
                annualized monitoring costs will total $17.3 million for this
                alternative (at a 3 percent discount rate), compared to $32.0 million
                for the proposed monitoring requirements, resulting in an estimated
                $14.7 million in lower costs per year (Table IX-9).
                 Although this alternative does not eliminate exposure monitoring,
                the requirements are minimal relative to the monitoring requirements
                under the proposed rule. However, MSHA believes it is necessary for
                mine operators to establish a solid baseline for any miner who is
                reasonably expected to be exposed to respirable crystalline silica. In
                addition, quarterly monitoring helps mine operators correlate mine
                conditions to miner exposure levels and see exposure trends more
                rapidly than would result from semi-annual or annual sampling. This
                would enable mine operators to take measures necessary to ensure
                continued compliance with the PEL. Further, more frequent monitoring
                would enable mine operators to ensure the adequacy of controls at their
                mines and better protect miners' health. These benefits cannot be
                quantified, but they are nevertheless material benefits that increase
                the likelihood of compliance.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.040
                 MSHA also believes that requiring more frequent periodic sampling
                would provide mine operators with greater confidence that they are in
                compliance with the proposed rule. Because of the variable nature of
                miner exposures to airborne concentrations of respirable crystalline
                silica, maintaining exposures below the proposed action level provides
                mine operators with reasonable assurance that miners would not be
                exposed to respirable crystalline silica at levels above the PEL on
                days when sampling is not conducted. MSHA believes that the benefits of
                the proposed sampling requirements justify the additional costs
                relative to Regulatory Alternative 1.
                2. Regulatory Alternative #2: Changes in Sampling and Evaluation
                Requirements and the Proposed PEL
                 Under this regulatory alternative, the proposed PEL would be set at
                25 [mu]g/m\3\; mine operators would install whatever controls are
                necessary to meet this PEL; and no action level would be proposed.
                Further, mine operators: (1) would not be required to conduct baseline
                sampling or periodic sampling; (2) would conduct semi-annual
                evaluations of changing conditions; and (3) would sample as frequently
                as necessary to determine the adequacy of controls.
                 Mine operators would not be required to undertake baseline or
                periodic sampling. However, mine operators would be required to perform
                semi-annual evaluations of changing mining processes or conditions.
                Further, mine operators would be required to perform post-evaluation
                sampling when the operators determine as a result of the semi-annual
                evaluation that miners may be exposed to respirable crystalline silica
                at or above proposed PEL at 25 [mu]g/m\3\. When estimating the cost of
                the proposed monitoring requirements, MSHA assumes that the number of
                samples for corrective action and semi-annual evaluation are relatively
                small (2.5 percent of miners) because samples from sampling to
                determine the adequacy of controls and from MSHA can both be used to
                meet the requirements. Since this alternative
                [[Page 44944]]
                does not require periodic sampling, MSHA increases samples after each
                evaluation to 10 percent of miners to ensure the monitoring
                requirements can be met.
                 This alternative also sets the proposed PEL at 25 [mu]g/m\3\. In
                addition to the estimated cost of compliance with a PEL of 50 [mu]g/
                m\3\, mine operators would incur additional engineering control costs
                to meet a PEL of 25 [mu]g/m\3\. To estimate these additional
                engineering control costs, MSHA largely uses the same methodology as
                for mines affected at the proposed PEL of 50 [mu]g/m\3\.
                a. Number of Mines Affected Under Regulatory Alternative 2
                 MSHA first estimated the number of mines expected to incur the cost
                of implementing engineering controls to reach the more stringent PEL.
                After excluding mines that are affected at the proposed PEL of 50
                [mu]g/m\3\ (to avoid double-counting), MSHA finds that 3,477 mines
                (2,991 MNM mines and 486 coal mines) operating in 2019 had at least one
                sample at or above 25 [mu]g/m\3\ but below 50 [mu]g/m\3\.\66\
                ---------------------------------------------------------------------------
                 \66\ About 8,053 of mines active in 2019 either did not have a
                sample > 25 [mu]g/m\3\ or did not have a sample in the last 5 years.
                ---------------------------------------------------------------------------
                 To this number, MSHA adds the 1,226 affected mines expected to
                incur costs to reach the proposed PEL of 50 [mu]g/m\3\. Based on its
                experience and knowledge, MSHA does not expect the mines that installed
                engineering controls to meet the PEL of 50 [mu]g/m\3\ will also be able
                to comply with a PEL of 25 [mu]g/m\3\. For example, to comply with the
                proposed PEL of 50 [mu]g/m\3\, a mine might need to add the engineering
                controls necessary to achieve an additional 10 air changes per hour
                over that achieved by existing controls, which are costed in the
                following section. However, such a mine facility would then need to add
                an additional 10 air changes per hour to meet the more stringent PEL of
                25 [mu]g/m\3\, which is not costed in the following section. Thus, MSHA
                expects that the 1,226 affected mines will incur additional costs to
                meet the PEL of 25 [mu]g/m\3\ specified under this alternative.
                 MSHA estimates a total of 4,703 mines will incur costs to purchase,
                install, and operate engineering controls to meet the PEL of 25 [mu]g/
                m\3\ under this alternative. MNM mines account for 4,087 (87 percent)
                and coal mines 616 (13 percent). Further, of the estimated 4,087 MNM
                mines and 616 coal mines, 1,096 MNM mines (27 percent) and 130 coal
                mines (21 percent) are also estimated to incur compliance costs to
                reach the proposed PEL of 50 [mu]g/m\3\.
                b. Estimated Engineering Control Costs Under Regulatory Alternative 2
                 MSHA identified potential engineering controls that would enable
                mines with respirable crystalline silica dust exposures at or above 25
                [mu]g/m\3\ but below 50 [mu]g/m\3\ categories to meet the PEL of 25
                [mu]g/m\3\ under consideration for this alternative. While MSHA assumes
                that mine operators will base such decisions on site-specific
                conditions such as mine layout and existing infrastructure, MSHA cannot
                make further assumptions about the specific controls that might be
                adopted and instead assumes the expected value of purchased
                technologies should equal the simple average of the technologies listed
                in each control category.
                 Where more precise information is unavailable, MSHA assumes
                operating and maintenance (O&M) costs to be 35 percent of initial
                capital expenditure and installation cost, when appropriate, will be
                equal to the initial capital expenditure (Table IX-10). MSHA also
                assumes the larger capital expenditure controls will have a 30-year
                service life. MSHA welcomes public comment concerning the engineering
                controls selected for this analysis and the assumptions used to
                estimate installation and O&M costs for these controls.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.041
                 However, the difficulty of meeting a PEL of 25 [mu]g/m\3\ is such
                that MSHA's experience suggests a single control from Table IX-10 will
                not be sufficient. For example, respirable crystalline silica dust
                exposure at such a stringent limit
                [[Page 44945]]
                as 25 [mu]g/m\3\ is likely to occur at more than one area of the mine;
                in addition to increasing ventilation to a crusher/grinder, enclosing
                and ventilating the conveyor belt mine would be necessary to reduce
                concentrations below the limit. Similarly, increasing facility
                ventilation from 20 to 30 air changes per hour may not be adequate to
                meet the limit; 40 air changes per hour might be necessary. Therefore,
                MSHA assumes mine operators will purchase and install at least two of
                the engineering controls listed in Table IX-10. This may be a
                conservative assumption.
                 Table IX-11 presents the average annualized engineering control
                costs per mine and total annualized engineering control costs by mine
                sector. Because the service life of nearly all components is expected
                to be 30 years, the costs of all engineering controls are annualized
                over 30 years. At a 3 percent real discount rate, the average
                annualized engineering control costs are about $94,300 per mine,
                resulting in an additional cost of $443.6 million if the PEL is set at
                25 [mu]g/m\3\ instead of 50 [mu]g/m\3\.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.042
                 Table IX-12 summarizes the estimated annualized cost of this
                alternative under consideration. At a 3 percent real discount rate,
                exposure monitoring costs less than the proposed rule; however, this
                lower cost is more than offset by the increased control costs
                necessitated by the requirement that mines maintain respirable
                crystalline silica exposure levels below 25 [mu]g/m\3\. At an estimated
                annualized cost of $491.2 million, this alternative would cost nearly
                eight times more than the proposed requirements.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.043
                [[Page 44946]]
                 This alternative requires exposure monitoring that is more
                stringent than Regulatory Alternative 1, but less stringent than the
                proposed requirements. In addition, Regulatory Alternative 2 increases
                miner protection by proposing to set the PEL at 25 [mu]g/m\3\,
                resulting in measurable avoided mortality and other health benefits.
                Table IX-13 presents the avoided morbidity and mortality cases over the
                60-year regulatory analysis time horizon under this alternative. Under
                this alternative, the avoided 60-year mortality is expected to be 981,
                which is 2.4 times higher than the expected avoided mortality of 410
                under a proposed PEL of 50 [mu]g/m\3\. The avoided 60-year morbidity
                under the regulatory alternative of 25 [mu]g/m\3\ is expected to be
                1,948, which is 1.4 times higher than the expected avoided 60-year
                morbidity of 1,420 under the proposed PEL of 50 [mu]g/m\3\.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.044
                 Table IX-14 presents the benefits associated with this avoided
                morbidity and mortality. The expected total benefits, discounted at 3
                percent, are $365.5 million, which is twice the expected total benefits
                of $175.7 million under the proposed PEL of 50 [mu]g/m\3\. Under this
                regulatory alternative, these benefits are made up of $258.0 million
                due to avoided mortality, $34.5 million due to morbidity preceding
                mortality, and $73.0 million due to morbidity not preceding mortality.
                However, when compared to the annualized costs, the net benefits of
                this alternative are negative at both a 3 percent and 7 percent real
                discount rate.
                [[Page 44947]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.045
                BILLING CODE 4520-43-C
                 MSHA solicits further comment on the extent to which these or other
                regulatory alternatives (including different ways of calculating
                respirable crystalline silica concentration) may change the effects of
                the proposed rule.
                X. Initial Regulatory Flexibility Analysis
                 The Regulatory Flexibility Act (RFA) of 1980, as amended by the
                Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996,
                requires preparation of an Initial Regulatory Flexibility Analysis
                (IRFA) for any rule that by law must be proposed for public comment,
                unless the agency certifies that the rule, if promulgated, will not
                have a significant economic impact on a substantial number of small
                entities. 5 U.S.C. 601- 612. Because MSHA's proposed rule on respirable
                crystalline silica, including the incorporation of ASTM F3387-19 by
                reference, would regulate the mining industry, the proposed rule falls
                within the purview of the RFA. MSHA has evaluated the impact of the
                proposed rule on small entities in this IRFA. MSHA's analysis is
                presented in the following.
                Description of the Reasons Why MSHA is Considering Regulatory Action
                 Based on its review of the health effects literature, MSHA has
                preliminarily determined that occupational exposure to respirable
                crystalline silica causes silicosis and other diseases. Based on its
                preliminary risk analysis, MSHA has also determined that under its
                existing standards, miners face a risk of material impairment of health
                or functional capacity from exposures to respirable crystalline silica.
                 Based on these preliminary determinations, MSHA proposes to amend
                its existing standards to better protect miners against occupational
                exposure to respirable crystalline silica, a carcinogen, and to improve
                respiratory protection for all airborne contaminants. The proposed rule
                would establish for mines of all sizes, a PEL of 50 [micro]g/m\3\ for a
                full shift, calculated as an 8-hour TWA, for all miners, and an action
                level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as 8-
                hour TWA. MSHA's proposal would also include other requirements to
                protect miner health, such as periodic exposure sampling and corrective
                actions to be taken when miners' exposures exceed the PEL. MSHA also
                proposes to replace existing requirements for respiratory protection
                and to incorporate by reference the ASTM F3387-19 Standard Practice for
                Respiratory Protection. MSHA believes that the proposed changes would
                significantly improve health protections for all miners over the course
                of their working lives.
                Objectives of, and Legal Basis for, the Proposed Rule
                 The proposed rule would fulfill MSHA's statutory obligation to
                ``promulgate improved mandatory health . . . standards to protect''
                miners' health under the Mine Act, as amended. 30 U.S.C. 801(g). The
                Mine Act requires the Secretary of Labor (Secretary) to develop and
                promulgate improved mandatory health or safety standards to prevent
                hazardous and unhealthy conditions and protect the health and safety of
                the nation's miners. 30 U.S.C. 811(a). The Secretary must set standards
                to assure, based on the best available evidence, that no miners will
                suffer material impairment of health or functional capacity from
                exposure to toxic materials or harmful physical agents over their
                working lives. 30 U.S.C. 811(a)(6)(A). Section 103(h) of the Mine Act
                gives the Secretary the authority to promulgate standards involving
                recordkeeping and reporting. 30 U.S.C. 813(h). Additionally, section
                508 of the Mine Act gives the Secretary the authority to issue
                regulations to carry out any provision of the Mine Act. 30 U.S.C. 957.
                [[Page 44948]]
                Description and Estimate of the Number of Small Entities to Which the
                Proposed Rule Would Apply
                 The proposed rule would affect MNM and coal mining operations. To
                determine the number of small entities subject to the proposed rule,
                MSHA reviewed the North American Industrial Classification System
                (NAICS), the standard used by Federal statistical agencies in
                classifying business establishments, as well as information from the
                Office of Advocacy of the Small Business Administration (SBA). MSHA
                used its data from the MSHA Standardized Information System (MSIS) to
                identify the responsible party for each mine. MSHA then combined that
                information with the size classification information.
                 First, MSHA determined that mining operations that fall into 25
                NAICS-based industry classifications may be subject to the proposed
                rule. These industry categories and their accompanying six-digit NAICS
                codes are shown in Table X-1.\67\
                ---------------------------------------------------------------------------
                 \67\ The NAICS classifications used in this analysis are drawn
                from a recent version of the NAICS (though, for reasons described
                below, not the latest version, which was published in January 2022).
                SBA established definitions of small entities for each of the
                categories in the earlier version, which were effective in August
                2019. This version of NAICS categories was needed for this analysis,
                in order for MSHA to cross-tabulate (or crosswalk) its data on mines
                and controllers with Bureau of Census data on revenues by NAICS
                codes, where these Census data were organized by the same NAICS
                codes that were in the earlier version. No comparable revenue data,
                at this writing, had yet been revised to the most recent NAICS
                categories, which prevented MSHA from using those categories. MSHA
                identified 25 NAICS categories (in the previous system) that
                accounted for all mining activities.
                ---------------------------------------------------------------------------
                 Second, MSHA matched the NAICS classifications with SBA small-
                entity size standards (based on number of employees) to determine the
                number of small entities within each of the respective NAICS codes. See
                Table X-1.
                 Third, MSHA counted the number of small-entity controllers in each
                NAICS code, after determining that a ``controller'' who owns and
                controls a mine as the appropriate unit of this IRFA analysis (based on
                SBA guidance) (Small Business Administration 2017). A controller is a
                parent company owning or controlling one or more mines. A controller
                can also be a firm, whereas a mine can be an establishment. Table X-1
                shows the count of all controllers and a count of small-entity
                controllers in each NAICS code. Some ``unique controllers'' are
                included in more than one NAICS code because they own or control
                multiple mines, each producing a different commodity. For this
                analysis, however, MSHA single-counted these unique controllers; for
                example, a controller who owns three mines in three different NAICS
                codes was only counted once.
                 Based on this methodology, MSHA estimated that in 2021, there were
                a total of 5,879 controllers, 5,007 of which were small-entity
                controllers. Many controllers owned one or two mines, while some
                controllers owned hundreds of mines nationwide (or worldwide). The
                5,007 small-entity controllers owned a total of 8,240 mines out of
                11,791 mines in operation in 2021.\68\
                ---------------------------------------------------------------------------
                 \68\ The number of controllers and mines examined in this
                regulatory flexibility analysis are those specifically known to
                operate in 2021. The year 2021 is the most current year for which
                complete information were available. Such information about
                controllers as parent companies might include, for example,
                knowledge of whether the parent company is a large, multinational
                corporation, which has bearing on this regulatory flexibility
                analysis. Because the benefit-cost analysis performed on the
                proposed rule did not need this kind of detailed information about
                controllers, it was able to have a broader scope to include data
                from other years besides 2021, which it did. As a result, the
                benefit cost analysis included a larger number of mines (and
                affected mines) and controllers. The key factor for this regulatory
                flexibility analysis is the estimated ratio of the regulatory cost
                per revenue for controllers, as reflected by the most current data.
                The estimation of this ratio is robustly addressed in MSHA's
                analysis of the 5,879 controllers in 2021 (which is not impacted by
                the exclusion of other years in this analyis).
                ---------------------------------------------------------------------------
                BILLING CODE 4520-43-P
                [[Page 44949]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.046
                BILLING CODE 4520-43-C
                [[Page 44950]]
                Description of the Projected Reporting, Recordkeeping, and Other
                Compliance Requirements for Small Entities
                 As explained earlier, the proposed rule would establish a PEL of 50
                [micro]g/m\3\ and an action level of 25 [micro]g/m\3\ for a full-shift
                exposure, calculated as 8-hour TWA. The proposed rule would also
                include other requirements. Examples include baseline, periodic, and
                corrective action sampling, semi-annual evaluations, medical
                surveillance, respiratory protection, and recordkeeping.
                 With regard to the paperwork burden on small entities, MSHA's
                proposed rule would create new information collection requests for the
                mining industry. As described in greater detail in Section XI below,
                these requirements include the collection of information involving: (1)
                exposure monitoring--samplings and semi-annual evaluations, (2)
                corrective actions taken, (3) miners unable to wear respirators, and
                (4) medical surveillance for MNM miners. Table XI-2 displays an annual
                estimate of information collection burden for the whole mining
                industry. Compliance costs on small entities that include recordkeeping
                costs are discussed below.
                Estimation of the Compliance Costs and Relative Burden to Small
                Entities
                 MSHA estimated the average annual regulatory cost per small-entity
                controller (based on a 3 percent discount rate), as well as the average
                annual revenue per small-entity controller. MSHA estimated, for each
                controller, the additional annual cost of the proposed regulation as a
                proportion of that controller's annual revenue. The average of these
                proportions (weighting controllers equally) was 0.122 percent, below a
                3 percent threshold used for significant impact. That is, for every $1
                million in revenue earned by a controller, the average regulatory cost
                was estimated to be $1,220.
                 Total Compliance Cost. MSHA estimated that the proposed rule would
                have an average cost of $60.23 million per year in 2021 dollars at a
                real discount rate of 3 percent. The estimated costs for the proposed
                rule would represent the additional costs necessary for mine operators
                to achieve full compliance with the proposed rule.
                 Compliance Costs by Small-Entity Controllers. Because mines (as
                well as controllers) vary in the scale of their operations, MSHA first
                estimated additional regulatory costs on a per-miner basis. MSHA
                anticipated that the additional regulatory costs per miner would vary
                across the six major commodity categories: coal, metal, nonmetal,
                stone, crushed limestone, and sand and gravel. MSHA analyzed employment
                data linked with controller data. By combining this information with
                compliance cost information, MSHA derived estimates of the regulatory
                costs for small-entity controllers. MSHA then estimated the regulatory
                cost for each of the 5,007 small-entity controllers identified in 2021.
                See the average annual regulatory cost per controller in Table X-2.
                 Revenues by Small-Entity Controllers. MSHA estimated revenues for
                each small-entity controller. The Agency estimated revenues per
                employee, by mine, and by controller, using data published by the U.S.
                Bureau of Census in their report, ``Statistics of U.S. Businesses''
                (SUSB).\69\ The SUSB data provided revenue estimates for enterprises in
                each NAICS code and for each ``size category'' (based on number of
                employees) within each NAICS code. The enterprise data considered
                controllers that had operations in more than one NAICS code. MSHA
                summed the estimated revenue for the establishments within the same
                NAICS code to create multiple enterprises with different NAICS codes
                and compare constructed enterprises with the SUSB data to estimate the
                revenue for each of these size-category-specific enterprises. This
                methodology was relevant for the ``largest'' of small-entity
                controllers, which controlled more than one mine, sometimes operating
                in different NAICS categories. Most small-entity controllers operated
                only one mine, meaning that no summation was required because only the
                number of employees in a single mine needed to be counted.
                ---------------------------------------------------------------------------
                 \69\ U.S. Census Bureau, ``Statistics of U.S. Businesses,''
                released May 2021. https://www.census.gov/data/tables/2017/econ/susb/2017-susb-annual.html. Data in the report were in reference to
                the year 2017, which MSHA adjusted to 2021 dollars. Data on revenues
                are presented in the report under the equivalent term ``receipts.''
                MSHA converted the 2017 revenues to 2021 dollars using the GDP
                Implicit Price Deflator published by the Bureau of Economic Analysis
                October 26, 2022, Table 1.1.9 Implicit Price Deflators for Gross
                Domestic Product, Series A191RD. https://apps.bea.gov/histdata/fileStructDisplay.cfm?HMI=7&DY=2022&DQ=Q3&DV=Advance&dNRD=October-28-2022. The index was 107.749 for 2017 and 118.895 for 2021,
                creating an adjustment factor (from 2017 to 2021 dollars) of
                118.895/107.749 or 1.103.
                ---------------------------------------------------------------------------
                 MSHA estimated revenues for each small-entity controller. Some
                small-entity controllers had mines belonging to different NAICS codes.
                This factor precluded MSHA from being able to precisely categorize
                small-entity controllers by NAICS code. MSHA estimated each small-
                entity controller's revenues.\70\
                ---------------------------------------------------------------------------
                 \70\ In a small number of cases (in terms of NAICS codes and
                size categories) the SUSB data were incomplete. In these cases, MSHA
                imputed revenue/employee ratios based on closely related data for
                comparable NAICS-size categories. MSHA then used these imputed
                revenue/employee ratios to estimate the revenues of some small-
                entity controllers, by the methodology just described.
                ---------------------------------------------------------------------------
                 Some of the small-entity controllers may also have operations in
                non-mining industries. If so, total revenues, including those from non-
                mining operations, would be higher than estimated here, and the ratios
                of regulatory costs to revenues shown in the summary table may be
                overestimated.
                 MSHA developed estimates of the number of miners for each small-
                entity controller, and for each NAICS category within each controller's
                activities. MSHA then combined these data with SUSB data on revenues by
                NAICS category and size category to generate estimated revenues for
                each small-entity controller. See the estimated average annual revenue
                per controller in Table X-2.
                 Ratio of Compliance Cost to Revenue. From the two sets of estimates
                described above--costs and revenues--for each small-entity controller,
                MSHA generated estimates of the ratios of regulatory cost to revenue,
                for each controller. Table X-2 shows the number of controllers, average
                annual regulatory costs, average annual revenue, and average cost as a
                percent of revenue.
                [[Page 44951]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.047
                Relevant Federal Rules Which May Duplicate, Overlap, or Conflict With
                the Proposed Rule
                 There are no Federal rules that may duplicate, overlap, or conflict
                with the proposed rule.
                Significant Alternatives and Their Impact on Small Entities
                 MSHA considered two alternatives in the proposed rule. Under
                Alternative 1, the proposed PEL would remain unchanged at 50 [mu]g/m\3\
                and the proposed action level would remain unchanged at 25 [mu]g/m\3\.
                Further, mine operators would conduct: (1) baseline sampling for miners
                who may be exposed to respirable crystalline silica at or above the
                proposed action level of 25 [mu]g/m\3\, (2) periodic sampling twice per
                year, and (3) annual evaluation of changing mining processes or
                conditions that would reasonably be expected to result in new or
                increased exposures. Under Alternative 2, the proposed PEL would be set
                at 25 [mu]g/m\3\; mine operators would install whatever controls are
                necessary to meet this PEL; and no action level would be proposed.
                Further, mine operators would: (1) not be required to conduct baseline
                sampling or periodic sampling, (2) conduct semi-annual evaluations of
                changing conditions, and (3) sample as frequently as necessary to
                determine the adequacy of controls. Additional detail on the two
                regulatory alternatives MSHA considered can be found in IX. Summary of
                Preliminary Regulatory Impact Analysis and Regulatory Alternatives and
                in the standalone PRIA document.
                 MSHA believes the proposed rule would provide improved health
                protections for miners and would be achievable for all mines. In
                developing the proposed rule, MSHA has included flexibilities for
                operators in the implementation of updated respiratory protection
                standard, which would reduce the burden on small entities. MSHA has
                made the following determinations regarding the two alternatives
                considered:
                 Alternative 1, ``Changes in Sampling and Evaluation
                Requirements,'' would reduce overall costs to the mining industry by
                26.2 percent, for costs calculated at both a 3 percent and 7 percent
                discount rate. These reduced costs would be proportionally experienced
                by small entities. The average costs as a percent of revenues for small
                entities would then be reduced (relative to the proposed rule) from
                0.12 percent to 0.09 percent.
                 Alternative 2, ``Changes in Sampling and Evaluation
                Requirements and the Proposed PEL,'' would increase overall costs to
                the mining industry by 701.9 percent, for costs calculated at a 3
                percent discount rate, and by 930.2 percent for costs calculated at a 7
                percent discount rate. The average costs as a percent of revenues for
                small entities would then rise (relative to the proposed rule) from
                0.12 percent to 0.98 percent, based on a 3 percent discount rate, and
                from 0.12 percent to 1.259 percent based on a 7 percent discount rate.
                 MSHA is seeking comments or additional information from
                stakeholders on whether there are alternatives the Agency should
                consider that would accomplish the objectives of this rulemaking while
                reducing the impact on small entities.
                Conclusion
                 MSHA estimated that small-entity controllers would be expected to
                incur, on average, additional regulatory costs equaling approximately
                0.122 percent of their revenues (or $1,220 for every $1 million in
                revenues).
                 As required under the RFA, MSHA is complying with its obligation to
                consult with the SBA's Chief Counsel for Advocacy on this proposed rule
                and on this initial regulatory flexibility analysis. Consistent with
                Agency's practice, notes of any meetings with the Chief Counsel for
                Advocacy's office on this proposed rule, or any written communications,
                will be placed in the rulemaking record.
                XI. Paperwork Reduction Act
                 The Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3521) provides
                for the Federal Government's collection, use,
                [[Page 44952]]
                and dissemination of information. The goals of the Paperwork Reduction
                Act include minimizing paperwork and reporting burdens and ensuring the
                maximum possible utility from the information that is collected under 5
                CFR part 1320. The Paperwork Reduction Act requires Federal agencies to
                obtain approval from the Office of Management and Budget (OMB) before
                requesting or requiring ``a collection of information'' from the
                public.
                 As part of the Paperwork Reduction Act process, agencies are
                generally required to provide a notice in the Federal Register
                concerning each proposed collection of information to solicit, among
                other things, comment on the necessity of the information collection
                and its estimated burden, as required in 44 U.S.C. 3506(c)(2)(A). To
                comply with this requirement, MSHA is publishing a notice of proposed
                collection of information in the proposed rule titled, Lowering Miners'
                Exposure to Respirable Crystalline Silica and Improving Respiratory
                Protection.
                 This rulemaking would require the creation of a new information
                collection as well as modification to the burdens for existing
                collections. As required by the Paperwork Reduction Act, the Department
                has submitted information collections, including a new information
                collection and revisions of two existing collections, to OMB for review
                to reflect new burdens and changes to existing burdens.
                I. New Information Collection Under Proposed Part 60, Respirable
                Crystalline Silica
                 Under proposed part 60 entitled ``Respirable Crystalline Silica,''
                some new burdens would apply to all mine operators, and other burdens
                would apply to only some mine operators. Below, the new information
                collection burden that would be created by proposed part 60 is
                discussed.
                 Proposed Sec. 60.16 lists all the recordkeeping requirements
                related to proposed part 60. Each of the requirements are discussed
                below:
                 Proposed Sec. 60.12 would require mine operators to make a record
                for each sampling and each evaluation conducted pursuant to this
                section. The sampling record would consist of the sample date, the
                occupations sampled, and the concentrations of respirable crystalline
                silica and respirable dust. The mine operator would also retain
                laboratory reports on sampling results. The semi-annual evaluation
                record would include the date of the evaluation and a record of the
                mine operator's evaluation of any changes in mining operations that may
                reasonably be expected to result in new or increased respirable
                crystalline silica exposures. In addition, the mine operator would be
                required to post the sampling and evaluation records and the laboratory
                report on the mine bulletin board and, if applicable, by electronic
                means, for the next 31 days, upon receipt. All records would be
                retained for at least 2 years from the date of each sampling or
                evaluation.
                 Proposed Sec. 60.13 would require mine operators to make a record
                of corrective actions and the dates of the corrective actions. The
                corrective action records would be retained for at least 2 years from
                the date of each corrective action.
                 Proposed Sec. 60.14 would require mine operators to retain a
                record of the written determination by a PLHCP that a miner who may be
                required to use a respirator is unable to wear a respirator. The
                written determination record would be retained for the duration of a
                miner's employment plus 6 months.
                 Proposed Sec. 60.15 would require MNM mine operators to obtain a
                written medical opinion from the PLHCP or specialist within 30 days of
                a miner's medical examination. The written medical opinion would
                contain the date of the medical examination, a statement that the
                examination has met the requirements of this proposed section, and any
                recommended limitations on the miner's use of respirators. The written
                medical opinion record would be retained for the duration of a miner's
                employment plus 6 months.
                II. Changes to Existing Information Collections
                 This proposed rulemaking would result in non-substantive changes to
                existing information collection packages. One change under OMB Control
                Number 1219-0011 is to occur after 1219-0NEW, Respirable Crystalline
                Silica Standard, is approved by OMB. The other change is the
                discontinuance of the existing information collection package under OMB
                Control Number 1219-0048 which is also to occur after OMB approval of
                1219-0NEW, Respirable Crystalline Silica Standard.
                 OMB Control Number 1219-0011, Respirable Coal Mine Dust Sampling,
                involves records for quarterly sampling of respirable dust in coal
                mines. The supporting statement references quartz and a reduced
                standard for respirable dust when quartz is present; however, there is
                no specific recordkeeping requirement that is associated with those
                references. Due to changes in the proposed rule, MSHA would make a non-
                substantive change to the supporting statement by removing such
                references. However, there would be no changes in paperwork burden and
                costs in this information collection.
                 OMB Control Number 1219-0048, Respirator Program Records, involves
                recordkeeping requirements under 30 CFR parts 56 and 57 for MNM mines
                when respiratory protection is used. MSHA is proposing to update the
                existing respiratory protection standard and permit mine operators to
                select the requirements of the standard that are applicable to their
                mines. This proposed change would eliminate the paperwork burden
                associated with respiratory protection resulting in the request to
                discontinue the existing information collection.
                A. Solicitation of Comments
                 Pursuant to the Paperwork Reduction Act, MSHA has prepared and
                submitted an information collection request (ICR) to OMB for the
                collection of information requirements identified in this proposed rule
                for OMB's review in accordance with 44 U.S.C. 3507(d). MSHA is
                soliciting comments concerning the proposed information collection
                related to respirable crystalline silica. MSHA is particularly
                interested in comments that:
                 Evaluate whether the proposed collection of information is
                necessary for the proper performance of the functions of the agency,
                including whether the information will have practical utility;
                 Evaluate the accuracy of the agency's estimate of the
                burden of the proposed collection of information, including the
                validity of the methodology and assumptions used;
                 Suggest methods to enhance the quality, utility, and
                clarity of the information to be collected; and
                 Minimize the burden of the collection of information on
                those who are to respond, including through the use of appropriate
                automated, electronic, mechanical, or other technological collection
                techniques or other forms of information technology (e.g., permitting
                electronic submission of responses).
                B. Proposed Information Collection Requirements
                 I. Type of Review: New Collection.
                 OMB Control Number: 1219-0NEW.
                 1. Title: Respirable Crystalline Silica Standard.
                 2. Description of the ICR: The proposed rule on respirable
                crystalline silica contains collection of information requirements that
                would assist miners and mine operators in identifying exposures to
                respirable crystalline silica
                [[Page 44953]]
                in order to track actual and potential occupational exposure and action
                taken to control such exposure.
                 There are provisions of this proposed rule that would take effect
                at different times after the implementation of this proposed rule, and
                there are provisions that would have different burden hours, burden
                costs, and responses each year. Therefore, MSHA shows the estimates of
                burden hours, burden costs, and responses in three separate years.
                 3. Summary of the Collection of Information: Highlighted below are
                the key assumptions, by provision, used in the burden estimates in
                Table XI-1:
                Proposed Sec. 60.12--Exposure Monitoring
                 ICR. Proposed Sec. 60.12 would require mine operators to make a
                record for each baseline sampling, corrective action sampling, periodic
                sampling, semi-annual evaluation, and post-evaluation sampling, as
                previously described.
                 Number of respondents. For proposed Sec. 60.12, the respondents
                would consist of all active mines because operators of active mines are
                assumed to perform baseline sampling and conduct semi-annual
                evaluations.
                 MSHA counts the number of active mines in 2019, defining an active
                mine as one that had at least 520 employment hours (equivalent to 1
                person working full time for a quarter) in at least one quarter of
                2019. Using this definition, MSHA estimates that a total of 12,631
                mines (11,525 MNM mines and 1,106 coal mines) would generate sampling
                and evaluation records.
                 Annual number of responses. The estimated average annual number of
                responses would be 142,408, including 24,439 for baseline sampling,
                9,237 for sampling after corrective actions, 64,116 for periodic
                sampling, 42,103 for semi-annual evaluation recording and posting, and
                2,513 for post-evaluation sampling.
                 MSHA assumes that all the active mines (12,631 mines) would conduct
                baseline sampling once in the first year. In succeeding years, about
                253 new mines would conduct baseline sampling with an average of 5.6
                samples per mine. The estimated number of periodic samplings is
                calculated based on the following factors: the number of miners with
                sampling results at or above the proposed action level (25 [mu]g/m\3\)
                but at or below the PEL (50 [mu]g/m\3\), the percent of miners needed
                for representative samples, and the number of quarters mines would be
                in operation. In year 1, MSHA expects the sampling to begin in the
                second half of the year, thereby decreasing the number of samples by
                half. As a result, MSHA estimates that an annual average of 64,116
                periodic samples would be conducted in the first three years.
                Furthermore, MSHA assumes that all 12,631 mines would record semi-
                annual evaluation results twice a year--except in year 1, when it would
                be done once--and then post those results on a mine bulletin board, or
                if applicable, by electronic means. MSHA estimates mines would conduct
                sampling as a result of their semi-annual evaluations and an average of
                four miners would be sampled, resulting in an annual average of 2,513
                samples.
                 MSHA estimates that about 22 percent of active mines (2,771 mines
                in total) would have at least one miner overexposed to respirable
                crystalline silica. MSHA further estimates that the 2,771 mines that
                would then conduct corrective action sampling for about four areas per
                mine. In year 1, they would sample in half as many areas.
                 Estimated annual burden. The estimated average annual burden would
                be 31,392 hours, including 6,110 hours for baseline sampling, 2,309 for
                corrective action sampling, 16,029 hours for periodic sampling, 6,316
                hours for semi-annual evaluation recording and posting, and 628 hours
                for post-evaluation sampling. MSHA estimates that it would take 15
                minutes to record the sampling results, 15 minutes to record the
                results of a semi-annual evaluation, and 3 minutes to post each of the
                evaluation results on the mine bulletin board, and, if applicable, by
                electronic means.
                Proposed Sec. 60.13--Corrective Actions
                 ICR. Proposed Sec. 60.13 would require mine operators to make a
                record of corrective actions, as previously described.
                 Number of respondents. For proposed Sec. 60.13, only those mines
                with at least one miner exposure above the proposed PEL are assumed to
                carry out the proposed requirement. MSHA estimates that about 22
                percent of active mines (2,771 mines in total) would have at least one
                miner overexposed to respirable crystalline silica.
                 Annual number of responses. The estimated average annual number of
                responses would be 14,922, including 9,237 for corrective action
                records, and 5,685 for miner respirator records. MSHA estimates that
                the 2,771 mines that will be required to conduct and record corrective
                actions will do so for about four mine areas, except in year 1, when it
                would be done in half as many mine areas. MSHA further estimates this
                will affect 6,822 miners per year--except in year 1, when half as many
                miners would be affected--with each miner requiring a record of the
                miner being given access to a respirator until the corrective action is
                taken.
                 Estimated annual burden. The estimated average annual burden would
                be 1,054 hours, including 769.7 for corrective action records and 284.3
                for miner respirator records. MSHA estimates that it takes five minutes
                to record a corrective action and the date. On average, it takes three
                minutes to note a miner's access to a respirator.
                Proposed Sec. 60.14--Respiratory Protection
                 ICR. Proposed Sec. 60.14 would require mine operators to retain a
                record of the determination by a PLHCP that a miner who may be required
                to use a respirator is unable to wear a respirator, as previously
                described.
                 Number of respondents. For proposed Sec. 60.14, MSHA assumes that
                33 percent of mine operators would have their miners use respiratory
                protection as a temporary measure and keep records of their miners'
                ability to wear respirators. The number of respondents would be, on
                average, 603 mines per year, with each mine assumed to have at least
                some miners wearing respirators.
                 Annual number of responses. The estimated annual number of
                responses would be 1,205, with an average of two miners for each of the
                603 mines.
                 Estimated annual burden. The estimated annual burden would be 603
                hours. MSHA assumes it takes 30 minutes to record this information for
                about two miners for each of the 603 mines.
                Proposed Sec. 60.15--Medical Surveillance for Mental and Nonmetal
                Miners
                 ICR. Proposed Sec. 60.15 would require MNM mine operators to
                obtain a written medical opinion from a PLHCP or specialist regarding
                any recommended limitations on a miner's use of respirators, as
                previously described.
                 Number of respondents. MSHA assumes that 75 percent of eligible MNM
                miners (current MNM miners), including contract workers, would make use
                of the opportunity to receive a voluntary medical exam that is paid by
                their mine operator. As a result, an average of 25,175 current miners
                are estimated to receive voluntary medical exams per year. This
                estimate represents the upper range of the participation rate of
                voluntary medical exams by miners. MSHA is using the upper end of the
                range to avoid underestimating compliance costs.
                 MSHA further estimates that 8,392 miners in a given year, including
                contract workers, would be new miners and contractors who would undergo
                mandatory medical examinations.
                [[Page 44954]]
                MSHA estimated that the turnover of MNM miners would be 8,392 miners
                per year (1/22 of the estimated total of 184,615 MNM workers with an
                average number of 22 years on the job before leaving the mining
                industry). The estimated total respondents per year therefore would be
                33,567 (= 8,392 + 25,175).
                 Annual number of responses. The estimated annual number of
                responses would be 33,567, including 8,392 new miners and 25,175
                current miners.
                 Estimated annual burden. The estimated annual burden would be 8,392
                hours, including 2,098 hours for new MNM miners and 6,294 hours for
                current miners. MSHA estimates it takes 15 minutes to record the
                medical examination results for each of the 33,567 miners.
                Total Recordkeeping and Documentation Burden for Proposed Part 60
                [GRAPHIC] [TIFF OMITTED] TP13JY23.048
                 As shown in Table XI-1, the total number of respondents is 46,198:
                12,631 mines plus 33,567 miners; the estimated annual number of
                responses would be 192,102; and the estimated annual burden would be
                41,440 hours. These estimates are based on the conservative assumption
                that 75 percent of eligible current miners would take part in medical
                surveillance, which could overestimate the recordkeeping cost and
                burden. The following estimates of information collection burden are
                summarized in Table XI-2.
                 1. Affected Public: Businesses or For-Profit.
                 2. Estimated Number of Respondents: 47,456 respondents in the first
                year; 46,198 respondents in the second year; and 44,939 respondents in
                the third year.
                 3. Frequency: On Occasion.
                 4. Estimated Number of Responses: 192,990 responses in the first
                year; 197,021 responses in the second year; and 186,294 responses in
                the third year.
                 5. Estimated Number of Burden Hours: 44,678 hours in the first
                year; 41,162 hours in the second year; and 38,480 hours in the third
                year.
                 6. Estimated Hour Burden Costs: $2,843,901 in the first year;
                $2,558,724 in the second year; and $2,377,996 in the third year.
                 7. Estimated Capital Costs to Respondents: $25,262 in each of the
                three years.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.049
                 Most of the reduction in the number of responses and burden hours
                from the first year to the second year is a result of baseline sampling
                being carried out in all current mines in the first year
                [[Page 44955]]
                while only being carried out in new mines starting from the second
                year.
                 For a detailed summary of the burden hours and related costs by
                provision, see the Preliminary Regulatory Impact Analysis (PRIA)
                accompanying the proposed rule. The PRIA includes the estimated costs
                and assumptions for the paperwork requirements related to this proposed
                rule.
                C. Changes to Existing Information Collection Requirements
                 I. Type of review: Non-substantive change to currently approved
                information collection.
                 OMB Control Number: 1219-0011.
                 1. Title: Respirable Coal Mine Dust Sampling.
                 2. Description of the ICR:
                Background
                 In October 2022, MSHA received OMB approval for the reauthorization
                of the Respirable Coal Mine Dust Sampling under OMB Control Number
                1219-0011. This information collection request outlines the legal
                authority, procedures, burden, and costs associated with recordkeeping
                and reporting requirements for coal mine operators. MSHA's standards
                require that coal mine operators sample respirable coal mine dust
                quarterly and make records of such samples.
                Summary of Changes
                 This non-substantive change request is to revise the supporting
                statement for this information collection request due to the proposed
                PEL for respirable crystalline silica for all miners in this proposed
                rule. These proposed revisions would remove any reference in the
                information collection request to quartz or the reduction of the
                respirable dust standard due to the presence of quartz. This change
                does not modify the authority, affected mine operators, or paperwork
                burden.
                 3. Summary of the Collection of Information:
                Changes in Burden
                 The calculated burden including respondents and responses remain
                the same.
                 Affected Public: Businesses or For-Profit.
                 Estimated Number of Respondents: 676 (0 from this rulemaking).
                 Frequency: On occasion.
                 Estimated Number of Responses: 995,102 (0 from this rulemaking).
                 Estimated Number of Burden Hours: 58,259 (0 from this rulemaking).
                 Estimated Hour Burden Costs: $3,271,611 ($0 from this rulemaking).
                 Estimated Capital Costs to Respondents: $29,835 ($0 from this
                rulemaking).
                 II. Type of Review: Discontinued information collection request.
                 OMB Control Number: 1219-0048.
                 1. Title: Respirator Program Records.
                 2. Description of the ICR:
                Background
                 Title 30 CFR parts 56 and 57 incorporate by reference requirements
                of ANSI Z88.2-1969, ``Practices for Respiratory Protection.'' Under
                this standard, certain records are required to be kept in connection
                with respirators. The proposed rule would incorporate by reference ASTM
                F3387-19, ``Standard Practice for Respiratory Protection,'' in 30 CFR
                parts 56 and 57 to replace the Agency's existing respiratory protection
                standard. The proposal would require mine operators' respiratory
                protection plans to include certain minimally acceptable program
                elements, but beyond that, would permit mine operators to select the
                requirements of ASTM F3387-19 that are applicable to their mines.
                Summary of Changes
                 The proposed rule would remove the paperwork burden associated with
                respiratory protection in the information collection request.
                 3. Summary of the Collection of Information:
                Changes in Burden
                 MSHA has submitted a request to discontinue OMB Control Number
                1219-0048, eliminating all paperwork burden associated with the
                information collection request. It would discontinue upon the effective
                date of the final rule.
                 Affected Public: Businesses or For-Profit.
                 Estimated Number of Respondents: 0 (-350 from this rulemaking).
                 Frequency: On occasion.
                 Estimated Number of Responses: 0 (-630 from this rulemaking).
                 Estimated Number of Burden Hours: 0 (-3,588 from this rulemaking).
                 Estimated Hour Burden Costs: $0 (-$284,084 from this rulemaking).
                 Estimated Capital Costs to Respondents: $0 (-$140,000 from this
                rulemaking).
                D. Submitting Comments
                 The information collection package for this proposal has been
                submitted to OMB for review under 44 U.S.C. 3506(c) of the Paperwork
                Reduction Act of 1995, as amended. Comments on the information
                collection requirements should be sent to MSHA by one of the methods
                previously explained in the DATES section of this preamble.
                 The information collection request will be available on http://www.regulations.gov. MSHA cautions the commenter against providing any
                information in the submission that should not be publicly disclosed.
                Full comments, including personal information provided, will be made
                available on www.regulations.gov and www.reginfo.gov.
                 The public may also examine publicly available documents at the
                Mine Safety and Health Administration, 201 12th South, Suite 4E401,
                Arlington, VA 22202-5450. Sign in at the receptionist's desk on the 4th
                floor via the East elevator. Before visiting MSHA in person, call 202-
                693-9440 to make an appointment and determine if any special health
                precautions are required in keeping with the Department of Labor's
                COVID-19 policy.
                 Questions about the information collection requirements may be
                directed to the contact person listed in the FOR FURTHER INFORMATION
                CONTACT section of this preamble.
                E. Docket and Inquiries
                 Those wishing to download comments and other materials relating to
                paperwork determinations should use the procedures described in this
                preamble. One may also obtain a copy of this ICR by going to http://www.reginfo.gov/public/do/PRAMain, clicking on ``Currently under
                Review--Open for Public Comments'' and scrolling down to ``Department
                of Labor.''
                 A Federal agency cannot conduct or sponsor a collection of
                information unless it is approved by OMB under the Paperwork Reduction
                Act and displays a currently valid OMB control number. The public is
                not required to respond to a collection of information unless the
                collection of information displays a currently valid OMB control
                number.
                XII. Other Regulatory Considerations
                A. National Environmental Policy Act
                 The National Environmental Policy Act (NEPA) of 1969 (42 U.S.C.
                4321 et seq.), requires each Federal agency to consider the
                environmental effects of final actions and to prepare an Environmental
                Impact Statement on major actions significantly affecting the quality
                of the environment. MSHA has reviewed the proposed standard in
                accordance with NEPA requirements, the regulations of the Council on
                Environmental Quality (40 CFR part 1500), and the Department of Labor's
                NEPA procedures (29 CFR part 11). As a result of this review, MSHA has
                determined that this proposed rule will
                [[Page 44956]]
                not have a significant environmental impact. Accordingly, MSHA has not
                conducted an environmental assessment nor provided an environmental
                impact statement.
                B. The Unfunded Mandates Reform Act of 1995
                 MSHA has reviewed the proposed rule under the Unfunded Mandates
                Reform Act of 1995 (2 U.S.C. 1501 et seq.). The Unfunded Mandates
                Reform Act requires Federal agencies to assess the effects of their
                discretionary regulatory actions. In particular, the Act addresses
                actions that may result in the expenditure by State, local, and Tribal
                governments, in the aggregate, or by the private sector, of $100
                million or more (adjusted annually for inflation) in any 1 year (5
                U.S.C. 1532(a)). MSHA has determined that this proposed rule does not
                result in such an expenditure. Accordingly, the Unfunded Mandates
                Reform Act requires no further Agency action or analysis.
                C. The Treasury and General Government Appropriations Act of 1999:
                Assessment of Federal Regulations and Policies on Families
                 Section 654 of the Treasury and General Government Appropriations
                Act of 1999 (5 U.S.C. 601 note) requires agencies to assess the impact
                of Agency action on family well-being. MSHA has determined that the
                proposed rule will have no effect on family stability or safety,
                marital commitment, parental rights and authority, or income or poverty
                of families and children, as defined in the Act. The proposed rule
                impacts the mine industry and does not impose requirements on states or
                families. Accordingly, MSHA certifies that this proposed rule will not
                impact family well-being, as defined in the Act.
                D. Executive Order 12630: Government Actions and Interference With
                Constitutionally Protected Property Rights
                 Section 5 of E.O. 12630 requires Federal agencies to ``identify the
                takings implications of proposed regulatory actions . . .'' MSHA has
                determined that the proposed rule does not implement a taking of
                private property or otherwise have takings implications. Accordingly,
                E.O. 12630 requires no further Agency action or analysis.
                E. Executive Order 12988: Civil Justice Reform
                 The proposed rule was written to provide a clear legal standard for
                affected conduct and was carefully reviewed to eliminate drafting
                errors and ambiguities so as to minimize litigation and avoid undue
                burden on the Federal court system. Accordingly, the proposed rule
                meets the applicable standards provided in section 3 of E.O. 12988,
                Civil Justice Reform.
                F. Executive Order 13045: Protection of Children From Environmental
                Health Risks and Safety Risks
                 E.O. 13045 requires Federal agencies submitting covered regulatory
                actions to OMB's Office of Information and Regulatory Affairs (OIRA)
                for review, pursuant to E.O. 12866, to provide OIRA with (1) an
                evaluation of the environmental health or safety effects that the
                planned regulation may have on children, and (2) an explanation of why
                the planned regulation is preferable to other potentially effective and
                reasonably feasible alternatives considered by the agency. In E.O.
                13045, ``covered regulatory action'' is defined as rules that may (1)
                be significant under Executive Order 12866 Section 3(f)(1) (i.e., a
                rulemaking that has an annual effect on the economy of $200 million or
                more or would adversely affect in a material way the economy, a sector
                of the economy, productivity, competition, jobs, the environment,
                public health or safety, or State, local or Tribal governments or
                communities), and (2) concern an environmental health risk or safety
                risk that an agency has reason to believe may disproportionately affect
                children. Environmental health risks and safety risks refer to risks to
                health or to safety that are attributable to products or substances
                that the child is likely to come in to contact with or ingest through
                air, food, water, soil, or product use or exposure.
                 MSHA has determined that, in accordance with E.O. 13045, while the
                proposed rule is considered significant under E.O. 12866 Section
                3(f)(1), it does not concern an environmental health or safety risk
                that may have a disproportionate impact on children. MSHA's proposed
                rule would lower the occupational exposure limit to respirable
                crystalline silica for all miners, take other actions to protect miners
                from adverse health risks associated with exposure to respirable
                crystalline silica, and require updated respiratory standards to better
                protect miners from all airborne hazards.
                 MSHA is aware of studies which have characterized and assessed the
                risks posed by ``take-home'' exposure pathways for hazardous dust
                particles. However, the proposed rule's primary reliance on engineering
                and administrative controls to protect miners from respirable
                crystalline silica exposures helps minimize risks associated with
                ``take-home'' exposures by reducing or eliminating silica that is in
                the mine atmosphere or the miner's personal breathing zone. The risks
                of take-home exposures are further minimized by MSHA's existing
                standards, operators' policies and procedures, and operators' use of
                clothing cleaning systems.
                 MSHA's existing standards limit miners' exposures to respirable
                crystalline silica. MSHA also requires coal mine operators to provide
                miners bathing facilities and change rooms. Miners have access to these
                facilities to shower and change their work clothes at the end of each
                shift. In addition, some mine operators provide miners with clean
                company clothing for each shift, have policies and procedures for
                cleaning or disposing of contaminated clothing, and provide a boot wash
                for miners to clean work boots during and after each shift. Moreover,
                some operators use clothing cleaning systems that can remove dust from
                a miner's clothing. Many of these systems include NIOSH-designed dust
                removal booths that use compressed air to remove dust, which is then
                vacuumed through a filter to remove airborne contaminants. Overall, the
                Agency's standards, mine operators' policies and procedures, and other
                safety practices including the use of clothing cleaning systems help to
                reduce or eliminate the amount of take-home exposure, therefore
                protecting other persons in a miner's household or persons who come in
                to contact with the miner outside of the mine site.
                 MSHA identified one epidemiological study (Onyije et al., 2022)
                that suggests a possible association between paternal exposure to
                respirable crystalline silica and childhood leukemia. However, this
                study does not provide dose-response data which would be needed to
                establish the dose of respirable crystalline silica which results in a
                no-adverse-effect-level (NOAEL) for childhood leukemia. This potential
                association has not been independently confirmed by another study. MSHA
                invites comment on the identification of any other scientific or
                academic study or information that evaluates the potential association
                between paternal exposure to respirable crystalline silica and
                childhood leukemia during the NPRM's public comment period.
                 MSHA also invites comment on the identification of any scientific
                or academic study or information that evaluates the potential risks to
                female workers who are exposed to respirable crystalline silica during
                pregnancy.
                 MSHA has no evidence that the environmental health or safety risks
                posed by respirable crystalline silica,
                [[Page 44957]]
                including ``take-home'' exposure to respirable crystalline silica,
                disproportionately affect children. Therefore, MSHA preliminarily
                concludes no further analysis or action is needed, in accordance with
                E.O. 13045.
                G. Executive Order 13132: Federalism
                 MSHA has determined that the proposed rule does not have
                ``federalism implications'' because it will not ``have substantial
                direct effects on the States, on the relationship between the national
                government and the States, or on the distribution of power and
                responsibilities among the various levels of government.'' Accordingly,
                under E.O. 13132, no further Agency action or analysis is required.
                H. Executive Order 13175: Consultation and Coordination With Indian
                Tribal Governments
                 MSHA has determined the proposed rule does not have ``tribal
                implications'' because it will not ``have substantial direct effects on
                one or more Indian tribes, on the relationship between the Federal
                Government and Indian tribes, or on the distribution of power and
                responsibilities between the Federal Government and Indian tribes.''
                Accordingly, under E.O. 13175, no further Agency action or analysis is
                required.
                I. Executive Order 13211: Actions Concerning Regulations That
                Significantly Affect Energy Supply, Distribution, or Use
                 E.O. 13211 requires agencies to publish a Statement of Energy
                Effects for ``significant energy actions,'' which are agency actions
                that are ``likely to have a significant adverse effect on the supply,
                distribution, or use of energy'' including a ``shortfall in supply,
                price increases, and increased use of foreign supplies.'' MSHA has
                reviewed the proposal for its impact on the supply, distribution, and
                use of energy because it applies to the mining industry. The proposed
                rule would result in annualized compliance costs of $4.85 million using
                a 3 percent real discount rate and $4.97 million using a 7 percent real
                discount rate for the coal mine industry relative to annual revenue of
                $27.03 billion. The proposal would also result in annualized compliance
                costs of $54.23 million using a 3 percent real discount rate and $55.72
                million using a 7 percent real discount rate for the metal/nonmetal
                mine industry relative to annual revenue of $88.32 billion. Because it
                is not ``likely to have a significant adverse effect on the supply,
                distribution, or use of energy'' including a ``shortfall in supply,
                price increases, and increased use of foreign supplies,'' it is not a
                ``significant energy action.'' Accordingly, E.O. 13211 requires no
                further agency action or analysis.
                J. Executive Order 13272: Proper Consideration of Small Entities in
                Agency Rulemaking
                 MSHA has thoroughly reviewed the proposed rule to assess and take
                appropriate account of its potential impact on small businesses, small
                governmental jurisdictions, and small organizations. MSHA's analysis is
                presented in Section X. Initial Regulatory Flexibility Analysis.
                K. Executive Order 13985: Advancing Racial Equity and Support for
                Underserved Communities Through the Federal Government
                 E.O. 13985 provides ``that the Federal Government should pursue a
                comprehensive approach to advancing equity for all, including people of
                color and others who have been historically underserved, marginalized,
                and adversely affected by persistent poverty and inequality.'' E.O.
                13985 defines ``equity'' as ``consistent and systematic fair, just, and
                impartial treatment of all individuals, including individuals who
                belong to underserved communities that have been denied such treatment,
                such as Black, Latino, and Indigenous and Native American persons,
                Asian Americans and Pacific Islanders and other persons of color;
                members of religious minorities; lesbian, gay, bisexual, transgender,
                and queer (LGBTQ+) persons; persons with disabilities; persons who live
                in rural areas; and persons otherwise adversely affected by persistent
                poverty or inequality.'' To assess the impact of the proposed rule on
                equity, MSHA considered two factors: (1) the racial/ethnic distribution
                in mining in NAICS 212 (which does not include oil and gas extraction)
                compared to the racial/ethnic distribution of the U.S. workforce (Table
                XII-1), and (2) the extent to which mining may be concentrated within
                general mining communities (Table XII-2).
                 In 2008, NIOSH conducted a survey of mines, which entailed sending
                a survey packet to 2,321 mining operations to collect a wide range of
                information, including demographic information on miners. NIOSH's 2012
                report, entitled ``National Survey of the Mining Population: Part I:
                Employees'' reported the findings of this survey (NIOSH 2012a). Race
                and ethnicity information about U.S. mine workers is presented in Table
                XII-1. Of all mine workers, including miners as well as administrative
                employees at mines, 93.4 percent of mine workers were white, compared
                to 80.6 percent of all U.S workers.\71\ There were larger percentages
                of American Indian or Alaska Native and Native Hawaiian or Other
                Pacific Islander people in the mining industry compared to all U.S.
                workers, while there were smaller percentages of Asian, Black or
                African American, and Hispanic/Latino people in the mining industry
                compared to all U.S. workers.
                ---------------------------------------------------------------------------
                 \71\ National data on workers by race were not available for the
                year 2008; comparable data for 2012 are provided for comparison
                under the assumption that there would not be major differences in
                distributions between these two years.
                ---------------------------------------------------------------------------
                 Table XII-2 shows that there are 22 mining communities, defined as
                counties where at least 2 percent of the population is working in the
                mining industry.\72\ Although the total population in this table
                represents only 0.15 percent of the U.S. population, it represents 12.0
                percent of all mine workers. The average per capita income in these
                communities in 2020, $47,977,\73\ was lower than the U.S. average,
                $59,510, representing 80.6 percent of the U.S. average. However, each
                county's average per capita income varies substantially, ranging from
                56.4 percent of the U.S. average to 146.8 percent.
                ---------------------------------------------------------------------------
                 \72\ Although 2 percent may appear to be a small number for
                identifying a mining community, one might consider that if the
                average household with one parent working as a miner has five
                members in total, then approximately 10 percent of households in the
                area would be directly associated with mining. While 10 percent may
                also appear small, this refers to the county. There are likely
                particular areas that have a heavier concentration of mining
                households.
                 \73\ This is a simple average rather than a weighted average by
                population.
                ---------------------------------------------------------------------------
                 The proposed rule would lower exposure to respirable crystalline
                silica and improve respiratory protection for all mine workers. MSHA
                determined that the proposed rule is consistent with the goals of E.O.
                13985 and would support the advancement of equity for all workers at
                mines, including those who are historically underserved and
                marginalized.
                BILLING CODE 4520-43-P
                [[Page 44958]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.050
                [[Page 44959]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.051
                [[Page 44960]]
                BILLING CODE 4520-43-C
                L. Availability of Materials To Be Incorporated by Reference
                 The Office of the Federal Register (OFR) has regulations concerning
                incorporation by reference. 5 U.S.C. 552(a); 1 CFR part 51. These
                regulations require that information that is incorporated by reference
                in a rule be ``reasonably available'' to the public. They also require
                discussion in the preamble to the rule of the ways in which materials
                it proposes to incorporate by reference are reasonably available to
                interested parties or how it worked to make those materials reasonably
                available to interested parties. Additionally, the preamble to the rule
                must summarize the material. 1 CFR 51.5(b).
                 In accordance with the OFR's requirements, MSHA provides in the
                following: (a) summaries of the materials to be incorporated by
                reference and (b) information on the public availability of the
                materials and on how interested parties can access the materials during
                the comment period and upon finalization of the rule.
                 ASTM F3387-19, ``Standard Practice for Respiratory Protection''
                (ASTM F3387-19) ASTM F3387-19 is a voluntary consensus standard that
                represents up-to-date advancements in respiratory protection
                technologies, practices, and techniques. The standard includes
                provisions for selection, fitting, use, and care of respirators
                designed to remove airborne contaminants from the air using filters,
                cartridges, or canisters, as well as respirators that protect miners in
                oxygen-deficient or immediately dangerous to life or health
                atmospheres. These provisions are based on NIOSH's long-standing
                experience of testing and approving respirators for occupational use
                and OSHA's research and rulemaking on respiratory protection. The
                proposed rule would incorporate by reference ASTM F3387-19 in existing
                Sec. Sec. 56.5005, 57.5005, and 72.710 and in proposed Sec.
                60.14(c)(2) to better protect all miners from airborne hazards. MSHA
                believes that incorporating by reference ASTM F3387-19 would provide
                mine operators with up-to-date requirements for respirator technology,
                reflecting an improved understanding of effective respiratory
                protection and therefore better protecting the health and safety of
                miners. For further details on MSHA's proposed update to the Agency's
                existing respiratory protection standard, please see section VII.C of
                this preamble, Updating MSHA Respiratory Protection Standards by
                Incorporating by Reference ASTM F3387-19.
                 A paper copy or printable version of ASTM F3387-19 may be purchased
                by mine operators or any member of the public at any time from ASTM
                International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
                PA 19428-2959; https://www.astm.org/. ASTM International makes read-
                only versions of its standards that have been referenced or
                incorporated into Federal regulation or laws available free of charge
                at its online Reading Room, https://www.astm.org/products-services/reading-room.html. During the comment period, a read-only version of
                ASTM F3387-19 will be made available free of charge.\74\
                ---------------------------------------------------------------------------
                 \74\ The read-only version of ASTM F3387-19 available for public
                review during the comment period can be accessed using the following
                link--https://tinyurl.com/mwk97hjn.
                ---------------------------------------------------------------------------
                 In addition, during the comment period and upon finalization of
                this rule, ASTM F3387-19 will be available for review free of charge at
                MSHA headquarters at 201 12th Street South, Arlington, VA 22202-5450
                (202-693-9440).
                 ISO 7708:1995: Air Quality--Particle Size Fraction Definitions for
                Health-Related Sampling.
                 ISO 7708:1995 is an international consensus standard that defines
                sampling conventions for particle size fractions used in assessing
                possible health effects of airborne particles in the workplace and
                ambient environment. It defines conventions for the inhalable,
                thoracic, and respirable fractions. The proposed rule would incorporate
                by reference ISO 7708:1995 in proposed Sec. 60.12(f)(4) to ensure
                consistent sampling collection by mine operators through the
                utilization of samplers conforming to ISO 7708:1995.
                 A paper copy or printable version of ISO 7708:1995 may be purchased
                by mine operators or any member of the public at any time from ISO, CP
                56, CH-1211 Geneva 20, Switzerland; phone: + 41 22 749 01 11; fax: + 41
                22 733 34 30; website: www.iso.org/. ISO makes read-only versions of
                its standards that have been incorporated by reference in the CFR
                available free of charge at its online Incorporation by Reference
                Portal, http://ibr.ansi.org/Default.aspx.
                 In addition, during the comment period and upon finalization of
                this rule, ISO 7708:1995 will be available for review free of charge at
                MSHA headquarters at 201 12th Street South, Arlington, VA 22202-5450,
                (202-693-9440).
                 TLV's Threshold Limit Values for Chemical Substances in Workroom
                Air Adopted by ACGIH for 1973.
                 This material is referenced in the amendatory text of this document
                but has already been approved for appendix A. No changes are proposed.
                XIII. References Cited in the Preamble
                Abraham, J.L. and Wiesenfeld, S.L. 1997. Two cases of fatal PMF in
                an ongoing epidemic of accelerated silicosis in oilfield
                sandblasters: Lung pathology and mineralogy. Annals of Occupational.
                Hygiene, Vol. 41, Supplement 1, pp. 440-447, 1997.
                Agency for Toxic Substances and Disease Registry (ATSDR). 2019.
                Toxicological profile for silica. U.S. Department of Health and
                Human Services, Centers for Disease Control and Prevention, Division
                of Toxicology and Human Health Sciences, Atlanta, GA.
                Almberg, K.S., Friedman, L.S., Rose, C.S., Go, L.H.T., Cohen, R.A.
                2020. Progression of coal workers' pneumoconiosis absent further
                exposure. Occupational and Environmental Medicine. 77:748-751.
                Almberg, K.S., Halldin, C.N., Blackley, D.J., Laney, A.S., Storey,
                E., Rose, C.S., Go, L.H.T. and Cohen, R.A. 2018a. Progressive
                massive fibrosis resurgence identified in U.S. coal miners filing
                for black lung benefits, 1970-2016. Annals of American Thoracic
                Society. 15(12): 1420-1426.
                Am. Fuel & Petrochemical Manufacturers v. Env't Prot. Agency, 3
                F.4th 373, 384 (D.C. Cir. 2021).
                American Conference of Governmental Industrial Hygienists (ACGIH)
                2022. TLV chemical substances introduction. https://www.acgih.org/science/tlv-bei-guidelines/tlv-chemical-substances-introduction/.
                American Conference of Governmental Industrial Hygienists (ACGIH).
                2010: Silica, crystalline: [alpha]-Quartz and cristobalite.
                Documentation of TLV Recommendation. Cincinnati, Ohio.
                American Conference of Governmental Industrial Hygienists (ACGIH).
                TLVs[supreg] Threshold limit values for chemical substances in
                workroom air adopted by the American Conference of Government
                Industrial Hygienists for 1973. Journal of Occupational Medicine.
                1974; 16(1):39-49 PMID: 4814108.
                American Iron and Steel Institute et al., v. Occupational Safety and
                Health Administration, 577 F.2d 825 (3d Cir. 1978).
                American Society of Testing and Materials (ASTM). 2019. Standard
                practice for respiratory protection. F3387-19. West Conshohocken,
                PA.
                American Thoracic Society (ATS). 2010a. Breathing in America:
                Diseases, progress, and hope. Ed: D.E. Schraufnagel. American
                Thoracic Society. 282 pages.
                American Thoracic Society (ATS). 2010b. An official American
                Thoracic Society public policy statement: Novel risk factors and the
                global burden of chronic obstructive pulmonary disease. By: Eisner
                M.D., Anthonisen, N., Coultas, D., Kuenzli, N., Perez-Padilla, R.,
                Postma, D., Romieu, I., Silverman, E.K., and Balmes, J.R. American
                Journal of Respiratory and Critical Care Medicine. 182:693-718.
                [[Page 44961]]
                American Thoracic Society (ATS). 1997. Adverse effects of
                crystalline silica exposure. Committee members Beckett W., Abraham,
                J., Becklake M., et al. American Journal of Respiratory Critical
                Care Medicine. 155:761-768.
                Ant[atilde]o, V.C., Petsonk, E.L., Sokolow, L.Z., Wolfe, A.L.,
                Pinheiro, G.A., Attfield, M.D., 2005. Rapidly progressive coal
                workers' pneumoconiosis in the United States: geographic clustering
                and other factors. Occup Environ Med. 62(10):670-4.
                Attfield, M. and Costello, J. 2004. Quantitative exposure-response
                for silica dust and lung cancer in Vermont granite workers. American
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                and Checkoway, H. 2006. Occupational risk factors for esophageal and
                stomach cancers among female textile workers in Shanghai, China.
                American Journal of Epidemiology. 163:717-725.
                Wiles, F.J. and Faure, M.H. 1977. Chronic obstructive lung disease
                in gold miners. In: Inhaled Particles IV, Part 2. Walton WH, ed.
                Oxford: Pergamon Press.
                Windau, J., Rosenman, K., Anderson, H., Hanranhan, L., Rudolph, L.,
                Stanbury, M., and Stark, A. 1991. The identification of occupational
                lung disease from hospital discharge data. Journal of Occupational
                Medicine. 33(10):1061-1066.
                Winter, P.D., Gardner, M.J., Fletcher, A.C., and Jones, R.D. 1990. A
                mortality follow-up study of pottery workers: Preliminary findings
                on lung cancer. International Agency on Research for Cancer Sci Publ
                97:83-94.
                Wright, J.L., Harrison, N., Wiggs, B., and Churg, A. 1988. Quartz
                but not iron oxide causes air-flow obstruction, emphysema, and small
                airways lesions in the rat. American Review of Respiratory Disease.
                138:129-135.
                Xu, Z., Morris Brown L., Pan, L.M., Liu, T-F., Stone, B.J., Guan,
                D.X., Liu, Q., Sheng, J-H., Dosemeci, M., Fraumeni, Jr, J., and
                Blot, J.W. 1996a. Cancer risks among iron and steel workers in
                Anshan, China, Part I: Proportional mortality ratio analysis.
                American Journal of Industrial Medicine. 30:1-6.
                Yang, H., Yang, L., Zhang, J.L. and Chen, J. 2006. Natural course of
                silicosis in dust-exposed workers. Journal of Huazhong
                [[Page 44970]]
                University of Science and Technology. [Med Sci]. 26: 257-260.
                Yu I.T., Tse, L.A., Wong, T.W., Leung, C.C., Tam, C.M, and Chan, A.
                C.K. 2005. Further evidence for a link between silica dust and
                esophageal cancer. International Journal of Cancer. 114:479-483.
                Yu, Q., Fu, G., Lin, H., Zhao, Q., Liu, Y., Zhou, Y., Shi, Y.,
                Zhang, L., Wang, Z., Zhang, Z., Qin, L. and Zhou, T. 2020. Influence
                of silica particles on mucociliary structure andMUC5B expression in
                airways of C57BL/6 mice. Experimental Lung Research. 46(7):217-225.
                doi: 10.1080/01902148.2020.1762804.
                XIV. Appendix
                Appendix A
                Description of MSHA Respirable Crystalline Silica Samples
                 This document describes the respirable crystalline silica
                samples used in this rulemaking. The Mine Safety and Health
                Administration (MSHA) collected these samples from metal/nonmetal
                (MNM) and coal mines and analyzed the data to support this
                rulemaking. Technical details are discussed in the following
                attachments.
                MNM Respirable Dust Sample Dataset, 2005-2019
                 From January 1, 2005, to December 31, 2019, 104,354 valid MNM
                respirable dust samples were entered into the MSHA Technical Support
                Laboratory Information Management System (LIMS) database.\75\ The
                dataset includes MNM mine respirable dust personal exposure samples
                collected by MSHA inspectors. A total of 57,824 samples contained a
                respirable dust mass of 0.100 mg or greater (referred as
                ``sufficient-mass dust samples''), while a total of 46,530 samples
                contained a respirable dust mass of less than 0.100 mg (referred as
                ``insufficient-mass dust samples'').
                ---------------------------------------------------------------------------
                 \75\ Only valid (non-void) MNM respirable dust samples were
                included in the LIMS dataset. Voided samples include any samples
                with a documented reason which occurred during the sampling and/or
                the MSHA's laboratory analysis for invalidating the results.
                ---------------------------------------------------------------------------
                 Respirable dust samples collected by MSHA inspectors are
                assigned a three-digit ``contaminant code'' based on the contaminant
                in the sample. MSHA's contaminant codes group contaminants based on
                their health effects \76\ and are assigned by the MSHA Laboratory
                based on sample type and analysis results. The codes link
                information, such as contaminant description, permissible exposure
                limit (PEL), and the units of measure for each contaminant sampled.
                ---------------------------------------------------------------------------
                 \76\ For example, contaminant code 523 indicates that dust from
                that sample contained 1 percent or more respirable crystalline
                silica (quartz). Exposure to respirable crystalline silica has been
                linked to the following health outcomes: silicosis, non-malignant
                respiratory disease, lung cancer, and renal disease.
                ---------------------------------------------------------------------------
                 The MNM respirable crystalline silica dataset includes five
                contaminant codes.
                MNM Respirable Dust Sample Contaminant Codes
                 Contaminant code 521--MNM respirable dust samples that
                were not analyzed for respirable crystalline silica.
                 Contaminant code 523--MNM respirable dust samples
                containing 1 percent or more quartz.
                 Contaminant code 525--MNM respirable dust samples
                containing cristobalite.
                 Contaminant code 121--MNM respirable dust samples
                containing less than 1 percent quartz where the commodity is listed
                as a ``nuisance particulate'' in Appendix E of the TLVs[supreg]
                Threshold Limit Values for Chemical Substances in Workroom Air
                Adopted by ACGIH for 1973 (reproduced in Table A-1).
                 Contaminant code 131--MNM respirable dust samples
                containing less than 1 percent quartz where the commodity is not
                listed as a ``nuisance particulate'' in Appendix E of the 1973 ACGIH
                TLV[supreg] Handbook.
                BILLING CODE 4520-43-P
                [GRAPHIC] [TIFF OMITTED] TP13JY23.052
                MNM Respirable Dust Samples With a Mass of at Least 0.100 milligram
                (mg) (Sufficient-Mass Dust Samples)
                 The 57,824 samples that contained at least 0.100 mg of
                respirable dust were analyzed to quantify their respirable
                crystalline silica content--mostly respirable quartz but also
                respirable cristobalite. The respirable crystalline silica
                concentrations were entered into the MSHA Standardized Information
                System (MSIS) database (internal facing) and Mine Data Retrieval
                System (MDRS) database (public facing). Those MNM respirable dust
                samples with a mass of at least 0.100 mg are analyzed and contained
                in MSIS. MSIS and MDRS differ from LIMS in that some of the fields
                associated with a sample can be modified or corrected by the
                inspector. These correctable fields include Mine ID, Location Code,
                and Job Code. Inspectors cannot access or modify the fields in the
                LIMS database.
                [[Page 44971]]
                 From the database, 55 samples \77\ were removed because they
                were erroneous, had an incorrect flow rate, had insufficient
                sampling time, or were duplicated. This resulted in a final dataset
                of 57,769 MNM samples that contained a mass of at least 0.100 mg of
                respirable dust. Datasets containing the analyzed samples that MSHA
                removed and retained can be found in the rulemaking docket MSHA-
                2023-0001.
                ---------------------------------------------------------------------------
                 \77\ There were 55 samples removed: 7 samples had no detected
                mass gain (denoted as ``0 mg''); 1 sample was a partial shift that
                was not originally marked correctly; 1 sample was removed at the
                request of the district; 44 samples had flow rates outside the
                acceptable range of 1.616-1.785 L/min; and 2 samples were duplicates
                of samples that were already in the dataset. This resulted in the
                final sample size of 57,769 = 57,824-(7 + 1 + 1 + 44 + 2).
                ---------------------------------------------------------------------------
                MNM Respirable Dust Samples With a Mass of Less Than 0.100 mg
                (Insufficient-Mass Samples)
                 The LIMS database also included 46,530 MNM respirable dust
                samples that contained less than 0.100 mg of respirable dust. These
                samples did not meet the minimum dust mass criterion of 0.100 mg and
                were not analyzed for respirable crystalline silica by MSHA's
                Laboratory.
                 From these 46,530 samples, 167 samples \78\ were removed because
                they were erroneous, had an incorrect flow rate, or had insufficient
                sampling time. This resulted in 46,363 remaining MNM samples
                containing less than 0.100 mg of respirable dust. These samples were
                assigned to contaminant code 521, indicating that the samples were
                not analyzed for quartz. Datasets containing the unanalyzed samples
                that MSHA removed and retained can be found in the rulemaking docket
                MSHA-2023-0001.
                ---------------------------------------------------------------------------
                 \78\ There were 167 samples removed: 75 samples had a cassette
                mass less than -0.03 mg (based on instrument tolerances, samples
                that report a cassette mass between -0.03 mg and 0 mg were treated
                as having a mass of 0 mg, samples with masses below that threshold
                of -0.03 mg were excluded); 52 samples had Mine IDs that did not
                report employment for any year from 2005-2019; 31 samples had flow
                rates outside the acceptable range of 1.615-1.785 L/min; six samples
                had sampling times of less than 30 minutes; and three samples had
                invalid Job Codes. This resulted in the final sample size of 46,363
                = 46,530-(75 + 52 + 31 + 6 + 3).
                ---------------------------------------------------------------------------
                All MNM Respirable Dust Samples
                 After removing the 222 samples mentioned above (55 sufficient-
                mass and 167 insufficient-mass), the dataset consisted of 104,132
                MNM respirable dust samples: 57,769 sufficient-mass samples and
                46,363 insufficient-mass samples. A breakdown of the MNM respirable
                dust samples is included in Table A-2.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.053
                BILLING CODE 4520-43-C
                Coal Respirable Dust Sample Dataset, 2016-2021
                 From August 1, 2016, to July 31, 2021, 113,607 valid respirable
                dust samples from coal mines were collected by MSHA inspectors and
                entered in the LIMS database.\79\ For coal mines, the analysis is
                based on samples collected by inspectors beginning on August 1,
                2016, when Phase III of MSHA's 2014 respirable coal mine dust (RCMD)
                standard went into effect. Samples taken prior to implementation of
                the RCMD standard would not be representative of current respirable
                crystalline silica exposure levels in coal mines.
                ---------------------------------------------------------------------------
                 \79\ Only valid (non-void) coal respirable dust samples were
                included in the LIMS dataset. Voided samples include any samples
                with a documented reason which occurred during the sampling and/or
                the MSHA's Laboratory analysis for invalidating the results.
                ---------------------------------------------------------------------------
                 Of these samples collected by MSHA inspectors, 67,963 samples
                were analyzed for respirable crystalline silica; 45,644 samples
                [[Page 44972]]
                were not. Respirable dust samples from coal mines contain the
                records of the sample type, and the occupation of the miner sampled.
                A coal sample's type is based on the location within the mine as
                well as the occupation of the miner sampled. Below is a list of coal
                sample types and descriptions, as well as the mass of respirable
                dust required for that type of sample to be analyzed for respirable
                crystalline silica.
                 Type 1--Designated occupation (DO). The occupation on a
                mechanized mining unit (MMU) that has been determined by results of
                respirable dust samples to have the greatest respirable dust
                concentration. Designated occupation samples must contain at least
                0.100 mg of respirable dust to be analyzed for respirable
                crystalline silica.
                 Type 2--Other designated occupation (ODO). Occupations
                other than the DO on an MMU that are also designated for sampling,
                required by 30 CFR part 70. These samples must contain at least
                0.100 mg of respirable dust to be analyzed for respirable
                crystalline silica.
                 Type 3--Designated area (DA). Designated area samples
                are from specific locations in the mine identified by the operator
                in the mine ventilation plan under 30 CFR 75.371(t), where samples
                will be collected to measure respirable dust generation sources in
                the active workings. These samples must contain at least 0.100 mg of
                respirable dust to be analyzed for respirable crystalline silica.
                 Type 4--Designated work position (DWP). A designated
                work position in a surface coal mine or surface work area of an
                underground coal mine designated for sampling to measure respirable
                dust generation sources in the active workings. Designated work
                position samples must contain at least 0.200 mg of respirable dust
                to be analyzed for respirable crystalline silica. There are
                exceptions for certain occupations: bulldozer operator (MSIS general
                occupation code 368), high wall drill operator (code 384), high wall
                drill helper (code 383), blaster/shotfirer (code 307), refuse/
                backfill truck driver (code 386), or high lift operator/front end
                loader (code 382). Samples from these occupations must have at least
                0.100 mg of respirable dust to be analyzed for respirable
                crystalline silica.
                 Type 5--Part 90 miner. A Part 90 miner is employed at a
                coal mine and has exercised the option under the old section 203(b)
                program (36 FR 20601, Oct. 27, 1971) or under 30 CFR 90.3 to work in
                an area of a mine where the average concentration of respirable dust
                in the mine atmosphere during each shift to which a miner is exposed
                is continuously maintained at or below the applicable standard and
                has not waived these rights. A sample from a Part 90 miner must
                contain at least 0.100 mg of respirable dust to be analyzed for
                respirable crystalline silica.
                 Type 6--Non-designated area (NDA). Non-designated area
                samples are taken from locations in the mine that are not identified
                by the operator in the mine ventilation plan under 30 CFR 75.371(t)
                as areas where samples will be collected to measure respirable dust
                generation sources in the active workings. These samples are not
                analyzed for respirable crystalline silica.
                 Type 7--Intake air samples are taken from air that has
                not yet ventilated the last working place on any split of any
                working section or any worked-out area, whether pillared or non-
                pillared, as per 30 CFR 75.301. These samples are not analyzed for
                respirable crystalline silica.
                 Type 8--Non-designated work position (NDWP). A work
                position in a surface coal mine or a surface work area of an
                underground coal mine that is sampled during a regular health
                inspection to measure respirable dust generation sources in the
                active workings but has not been designated for mandatory sampling.
                For the analysis of respirable crystalline silica, these samples
                must have at least 0.200 mg of respirable dust. There are exceptions
                for certain occupations: bulldozer operator (MSIS general occupation
                code 368), high wall drill operator (code 384), high wall drill
                helper (code 383), blaster/shotfirer (code 307), refuse/backfill
                truck driver (code 386), or high lift operator/front end loader
                (code 382). Samples taken from these occupations must contain at
                least 0.100 mg respirable dust to be analyzed for respirable
                crystalline silica.
                Coal Respirable Dust Samples Analyzed for Respirable Crystalline Silica
                 There were 67,963 samples from coal mines collected by MSHA
                inspectors from underground and surface coal mining operations that
                were analyzed for respirable crystalline silica. These results were
                entered first into LIMS, and then into MSIS and MDRS. Results from
                MSIS were used as they may be updated by the inspectors at later
                dates.\80\ From those 67,963 samples, 4,836 samples were removed as
                they were environmental samples, voided in MSIS, or had other
                errors.\81\ This resulted in a dataset of 63,127 samples from coal
                mines that were analyzed for respirable crystalline silica. Datasets
                containing the analyzed samples that MSHA removed and retained can
                be found in the rulemaking docket MSHA-2023-0001.
                ---------------------------------------------------------------------------
                 \80\ As mentioned in the section concerning samples for MNM
                mines, MSIS and MDRS differ from LIMS in that some data fields can
                be modified or corrected by the inspector. These correctable fields
                include Mine ID, Location Code, and Job Code.
                 \81\ There were 4,836 samples removed: 4,199 samples were
                environmental and not personal samples (see Sample Type explanation
                for more detail); 631 samples had been voided after they had been
                entered into MSIS; and 6 had invalid Job Codes. This resulted in the
                final sample size of 63,127 = 67,963-(4,199 + 631 + 6).
                ---------------------------------------------------------------------------
                Coal Respirable Dust Samples Not Analyzed for Respirable Crystalline
                Silica
                 Similar to MNM respirable dust samples, the LIMS database
                includes 45,644 coal samples that did not meet the criteria for
                analysis and were thus not analyzed for respirable crystalline
                silica content.\82\ After removing 13,243 \83\ samples that were
                environmental samples, erroneous, or had voided controls, there were
                32,401 samples that were not analyzed for respirable crystalline
                silica. Datasets containing the unanalyzed samples that MSHA removed
                and retained can be found in the rulemaking docket MSHA-2023-0001.
                ---------------------------------------------------------------------------
                 \82\ In addition to the criteria listed above, samples from Shop
                Welders (code 319) are not analyzed for respirable crystalline
                silica as they are instead analyzed for welding fumes.
                 \83\ There were 13,243 samples removed: 6 samples had
                typographical errors; 14 samples had a cassette mass less than -0.03
                mg (based on instrument tolerances, samples that report a cassette
                mass between -0.03 mg and 0 mg were treated as having a mass of 0
                mg); 92 samples had invalid Job Codes; 12,724 were environmental
                samples; 44 samples had an occupation code of 000 despite having a
                personal sample `Sample Type'; 271 samples had controls that were
                voided; and 92 came from Job Code 319--Welder (see Footnote 82).
                This resulted in the final sample size of 32,401 = 50,545-(6 + 14 +
                92 + 12,724 + 44 + 271 + 92).
                ---------------------------------------------------------------------------
                All Coal Respirable Dust Samples
                 In total, 18,079 respirable dust samples from coal mines were
                removed from the original datasets: 4,836 samples that were analyzed
                for respirable crystalline silica and 13,243 samples that were not.
                This created a final dataset of 95,528 samples: 63,127 analyzed
                samples and 32,401 samples that were not analyzed.\84\ A breakdown
                of respirable dust samples from coal mines is included in Table A-3.
                ---------------------------------------------------------------------------
                 \84\ This dataset did not include any other coal mine respirable
                dust sample types collected by MSHA inspectors--i.e., sample types 3
                (designated area samples), types 6 (Non-face occupations) and 7
                (Intake air), samples taken on the surface mine shop welder (n=319),
                and all voided samples. Voided samples are any samples that have a
                documented reason which occurred during the sampling and/or
                laboratory analysis for invalidating the results.
                ---------------------------------------------------------------------------
                BILLING CODE 4520-43-P
                [[Page 44973]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.054
                Attachment 1. MNM Samples Analyzed for Cristobalite
                 Cristobalite is one of the three polymorphs of respirable
                crystalline silica analyzed by MSHA's Laboratory upon request that
                is included in this proposed rule. At the request of the inspector,
                MNM \85\ respirable dust samples that contain at least 0.050 mg of
                respirable dust are analyzed for cristobalite. Of the 57,769
                retained MNM samples that contained at least 0.050 mg of respirable
                dust, 0.6 percent (or 359 samples) were analyzed for cristobalite.
                Coal respirable dust samples are not analyzed for cristobalite.\86\
                ---------------------------------------------------------------------------
                 \85\ See Attachment 2. Technical Background about Measuring
                Respirable Crystalline Silica, for more information.
                 \86\ See Attachment 2. Technical Background about Measuring
                Respirable Crystalline Silica, for more information.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.055
                 While the samples that were analyzed for cristobalite were
                assigned to all four contaminant codes seen in this dataset, the
                majority were assigned contaminant code 523.
                [[Page 44974]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.056
                 The distribution of the 359 samples by cristobalite mass can be
                seen in Table A1-3.\87\
                ---------------------------------------------------------------------------
                 \87\ Of the 369 samples that were analyzed for cristobalite, 334
                had a value for cristobalite mass that was less than the limit of
                detection (LOD) for cristobalite, 10 [micro]g. As such these samples
                were assigned a value of 5 [micro]g of cristobalite, one half the
                LOD. See Attachment 2. Technical Background about Measuring
                Respirable Crystalline Silica, for more information.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.057
                 The mass of each sample was then used to calculate a
                cristobalite concentration by dividing the mass of cristobalite by
                the volume of air sampled (0.816 m\3\). The calculated
                concentrations ranged from 6 [micro]g/m\3\ to 53 [micro]g/m\3\.\88\
                ---------------------------------------------------------------------------
                 \88\ One sample had a cristobalite concentration of 53 [micro]g/
                m\3\. It was sampled in July of 2011 at Mine ID 4405407 and cassette
                number 610892. The commodity being mined was Stone: Crushed, Broken
                Quartzite. The occupation of the miner being sampled was Miners in
                Other Occupations: Job Code 513--Building and Maintenance.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.058
                [[Page 44975]]
                BILLING CODE 4520-43-C
                Attachment 2. Technical Background About Measuring Respirable
                Crystalline Silica
                 In the proposed rule, respirable crystalline silica refers to
                three polymorphs: quartz, cristobalite, and tridymite. MSHA's
                Laboratory uses two methods to analyze respirable crystalline silica
                content in mine respirable dust samples. The first method, X-ray
                diffraction (XRD), separately analyzes quartz, cristobalite, and
                tridymite contents in respirable dust samples that mine inspectors
                obtain at MNM mine sites (MSHA Method P-2, 2018a). The second
                method, Fourier transform infrared spectroscopy (FTIR), is used to
                analyze quartz in respirable dust samples obtained at coal mines
                (MSHA Method P-7, 2018b and 2020). Although the XRD method can be
                expanded from MNM to coal dust samples, MSHA chooses to use the FTIR
                method for coal dust samples because it is a faster and less
                expensive method. However, the current MSHA P-7 FTIR method cannot
                quantify quartz if cristobalite and/or tridymite are present in the
                sample. The method also corrects the quartz result for the presence
                of kaolinite, an interfering mineral for quartz analysis in coal
                dust.
                Limits of Detection and Limits of Quantification for Silica Sample Data
                 The Limits of Detection (LOD) and Limits of Quantification (LOQ)
                are the two terms used to describe the method capability. The LOD
                refers to the smallest amount of the target analyte (respirable
                crystalline silica) that can be detected in the sample and
                distinguished from zero with an acceptable confidence level that the
                analyte is actually present. It can also be described as the
                instrument signal that is needed to report with a specified
                confidence that the analyte is present. The LOQ refers to the
                smallest amount of the target analyte that can be repeatedly and
                accurately quantified in the sample with a specified precision. The
                LOQ is higher than the LOD. The values of the LOD and LOQ are
                specific to MSHA's Laboratory as well as the instrumentation and
                analytical method used to perform the analysis. These values do not
                change from one batch to another when samples are analyzed on the
                same equipment using the same method. However, their levels may
                change over time due to updated analytical methods and technological
                advances. The values of the LOD and LOQ for the methods (XRD and
                FTIR) used in analyzing respirable crystalline silica samples are
                explained in MSHA documents for MNM samples and coal samples (MSHA
                Method P-2, 2018a; MSHA Method P-7, 2018b and 2020). MSHA
                periodically updates these values to reflect progress in its
                analytical methods. The values of LOD and LOQ were last updated in
                2022 for MNM samples and in 2020 for coal samples.
                 The values of LODs and LOQs for respirable crystalline silica in
                samples from MSHA inspectors depend on several factors, including
                the analytical method used (XRD or FTIR) and the silica polymorph
                analyzed (quartz, cristobalite, or tridymite), as presented in Table
                A2-1.
                 For a sample with respirable crystalline silica content less
                than the method LOD, the maximum concentration is calculated as the
                respirable crystalline silica mass equivalent to LOD divided by the
                volume of air sampled. For example, if no quartz is detected by XRD
                analysis for an MNM sample, the method LOD is 5 [micro]g. If that
                sample is collected at 1.7 L/min air flow rate for 480 minutes
                (i.e., 8 hours), the air sample volume would be 816 L (= 1.7 L/min *
                480 minutes), or 0.816 m\3\. The calculated maximum concentration
                associated with a sample having respirable crystalline silica mass
                below the method LOD would be 6 [micro]g/m\3\ (= 5 [micro]g/0.816
                m\3\). The ``half maximum concentration'' is the midpoint between 0
                and the calculated maximum respirable crystalline silica
                concentration, which is 3 [micro]g/m\3\ (= \1/2\ * 6 [micro]g/m\3\)
                in this example.
                BILLING CODE 4520-43-P
                [[Page 44976]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.059
                 The air volume is treated differently for MNM and coal samples
                under the existing standards. In the case of MNM samples, 8-hour
                equivalent time weighted averages (TWAs) are calculated using 480
                minutes (8 hours) and a flow rate of 1.7 L/min, even if samples are
                collected for a longer duration. In contrast, coal TWAs are
                calculated using the full duration of the shift and a flow rate of
                2.0 L/min and converted to an MRE equivalent concentration under
                existing standards.
                Assumptions for Analyzed Samples
                 Samples from MNM mines that contain at least 0.100 mg of dust
                mass are analyzed for the presence of quartz and/or cristobalite.
                For samples from coal mines, the minimum amount of respirable dust
                in a sample to be analyzed for respirable crystalline silica is
                determined by sample type and the occupation of the miner sampled.
                For Sample Types 1, 2, and 5, the sample must contain at least 0.100
                mg of respirable dust. For Sample Types 4 and 8, the sample must
                contain at least 0.200 mg of respirable dust unless it comes from
                one of the following occupations: bulldozer operator (MSIS general
                occupation code 368), high wall drill operator (code 384), high wall
                drill helper (code 383), blaster/shotfirer (code 307), refuse/
                backfill truck driver (code 386), and high lift operator/front end
                loader (code 382). Samples taken from these occupations must contain
                at least 0.100 mg respirable dust to be analyzed for respirable
                crystalline silica. Samples from Shop Welders (code 319) are never
                analyzed for quartz, as they instead are sent for welding fume
                analysis.
                 MSHA makes separate assumptions based on the mass of respirable
                crystalline silica for a sample, whether it is above or below the
                method LOD. For all samples reporting a mass of respirable
                crystalline silica greater or equal to the method LOD, MSHA used the
                reported values to calculate the respirable crystalline silica
                concentration for the sample. For samples with values below the
                method LOD, including samples reported as containing 0 [micro]g of
                silica, MSHA used \1/2\ of the LOD to calculate the respirable
                crystalline silica concentration of the sample. MSHA understands
                that its assumptions regarding samples with respirable crystalline
                silica mass below the method LOD will have a minimal impact on the
                assessment.\89\
                ---------------------------------------------------------------------------
                 \89\ In its Final Regulatory Economic Analysis (FREA) for its
                2016 silica rule, OSHA observed: ``. . . that XRD analysis of quartz
                from samples prepared from reference materials can achieve LODs and
                LOQs between 5 and 10 [micro]g was not disputed in the [rulemaking]
                record.'' (OSHA, 2016).
                ---------------------------------------------------------------------------
                [[Page 44977]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.060
                 The reported value of respirable crystalline silica mass from an
                MNM or coal sample can fall under one of the four groups: (1) at or
                above the method LOQ, (2) at or above the method LOD but below the
                LOQ, (3) greater than 0 [mu]g but less than the method LOD, or (4)
                equal to 0 [mu]g. MSHA treats these samples differently based on
                their respirable crystalline silica mass.
                Quartz Mass at or Above the Method LOQ
                 For MNM and coal samples reporting quartz mass at or above the
                method LOQs, MSHA uses the values reported by the MSHA's Laboratory.
                Quartz Mass Between Method LOD and LOQ
                 For MNM and coal samples reporting quartz mass at or above the
                method LOD but below the LOQ, MSHA uses the values reported by the
                MSHA's Laboratory.
                Quartz Mass Between the Method LOD and 0 mg
                 A review of respirable crystalline silica samples in LIMS
                reveals that some samples had a respirable crystalline silica mass
                below the LOD of the analytical methods but greater than 0 [mu]g.
                Values in this range (i.e., below the method LOD but greater than 0
                [mu]g) cannot reliably indicate the presence of respirable
                crystalline silica. The mass of silica in these is too small to
                reliably detect, but the concentration of silica could be up to the
                calculated maximum concentration based on the method LOD. For
                example, consider a sample from an MNM mine that was analyzed for
                quartz and had a reported quartz mass of 4 [mu]g. This falls below
                the LOD of 5 [mu]g but above 0 [mu]g, and as such the sample could
                actually contain anywhere from 0 [mu]g of quartz up to the LOD value
                of 5 [mu]g of quartz.
                 In these cases, MSHA used \1/2\ the LOD value to calculate
                respirable crystalline silica concentration. MSHA explored other
                options to treat these samples such as treating the reported silica
                mass as 0 [mu]g/m\3\ (lower bound) as well as assuming the sample
                silica mass is just below the LOD and assigning each sample a value
                of the method LOD (upper bound). The use of the \1/2\ LOD value is
                considered a reasonable assumption since using either the lower
                bound of 0 [mu]g/m\3\ or the upper bound of the associated method's
                LOD could under or overestimate exposures, respectively. The
                assumption is not expected to impact the assessment of silica
                concentration because any sample results with respirable crystalline
                silica mass below the method LODs (between 3-10 [mu]g/m\3\) would
                also have been well below the lowest exposure profile range ( Job code 0 ``Area,'' because area samples are not
                specific to any one occupation.
                 Job code 398 ``Groundman,'' because there were no
                sample data for this code in the respirable crystalline silica
                sampling dataset.
                 Job codes 590 ``Education Specialist,'' 591 ``Mineral
                Industrial Safety Officer,'' 592 ``Mine Safety Instructor,'' and 594
                ``Training Specialist,'' because there were no coal respirable
                crystalline silica (quartz) data for these codes for the timeframe
                selected.
                 Job codes 602 ``Electrician,'' 604 ``Mechanic,'' 609
                ``Supply Person,'' 632 ``Ventilation Worker,'' and 635 ``Continuous
                Miner Operator Helper,'' because there were no sample data for these
                codes in the respirable crystalline silica sampling dataset.
                 The remaining 209 coal job codes are first divided by the job
                location--underground or surface--because potential respirable
                crystalline silica exposures at coal mines can vary depending on
                where a miner works at a given mine. (Three job codes are used in
                [[Page 44981]]
                both underground and surface locations: job codes 402 ``Master
                Electrician,'' 404 ``Master Mechanic,'' and 497 ``Clerk/
                Timekeeper.'') The underground and surface job codes are further
                grouped on the basis of the types of tasks and typical engineering
                controls. For example, as shown in Figure 1, the underground
                ``Continuous Mining Machine Operators'' occupational category
                includes 14 different occupations that involve drilling activities--
                occupations such as ``Coal Drill Helper,'' ``Coal Drill Operator,''
                and ``Rock Driller.'' The underground ``Operators of Large Powered
                Haulage Equipment'' occupational category has 12 similar occupations
                including ``Loading Machine Operator,'' ``Shuttle Car Operator,''
                and ``Motorman.''
                [GRAPHIC] [TIFF OMITTED] TP13JY23.065
                 There are five categories of underground occupations and four
                categories of surface occupations.
                 The five underground occupational categories include:
                 (1) Continuous Mining Machine Operators (e.g., Coal Drill Helper
                and Coal Drill Operator);
                 (2) Operators of Large Powered Haulage Equipment (e.g., Shuttle
                Car, Tractor, Scoop Car);
                 (3) Longwall Workers (e.g., Headgate Operator and Jack Setter
                (Longwall));
                 (4) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper); and
                 (5) Underground Miners (e.g., Electrician, Mechanic, Belt Man/
                Conveyor Man, and Laborer, etc.).
                 The four surface occupational categories include:
                 (1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and
                Auger Operator);
                 (2) Operators of Large Powered Haulage Equipment (e.g., Backhoe,
                Forklift, and Shuttle Car);
                 (3) Crusher Operators (e.g., Crusher Attendant, Washer Operator,
                and Scalper-Screen Operator); and
                 (4) Mobile Workers (e.g., Electrician, Mechanic, Blaster,
                Cleanup Man, Mine Foreman, etc.).
                 Attachments 1 and 3 provide the full lists of occupational
                categories and coal job codes.
                MNM Occupational Categories
                 From the 121 MNM job codes in IAS, 120 job codes are included in
                the occupational categories and 1 job code is excluded. The code
                that has been excluded is:
                 Job code 413 ``Janitor,'' because there were no sample
                data for this code in the respirable crystalline silica sampling
                dataset.
                 Of the 120 job codes included, 1 job code was listed in both the
                ``Crushing Equipment and Plant Operators'' occupational category and
                the ``Kiln, Mill and Concentrator Workers'' category. The code that
                was used twice is:
                 Job Code 388 ``Screen/Scalper Operators,'' because MNM
                job codes do not indicate the location where the work is taking
                place and this work can be conducted either in a plant or on the
                surface of the mine.
                 The final 121 MNM job codes (with job code 388 included twice)
                were first grouped into 14 occupational categories based on the
                types of tasks and typical engineering controls used. For example,
                as seen in Figure 2, the ``Drillers'' occupational category includes
                the 20 different occupations that involve drilling activities, such
                as ``Diamond Drill Operator,'' ``Drill Operator Churn,'' and
                ``Continuous Miner Operator.'' ``Belt Cleaner,'' ``Belt Crew,'' and
                ``Belt Vulcanizer'' are included in the occupational category,
                ``Conveyor Operators.'' Similar tasks were grouped together because
                the work activities and respirable crystalline silica exposures were
                anticipated to be comparable.
                [[Page 44982]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.066
                 The 14 occupational categories were:
                 (1) Bagging Machines;
                 (2) Stone Saws;
                 (3) Stone Trimmers, Splitters;
                 (4) Truck Loading Stations;
                 (5) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and
                Supervisors);
                 (6) Conveyors;
                 (7) Crushers;
                 (8) Dry Screening Plants;
                 (9) Kilns/Dryers, Rotary Mills, Ball Mills, and Flotation/
                Concentrators;
                 (10) Large Powered Haulage Equipment (e.g., Trucks, FELs,
                Bulldozers, and Scalers);
                 (11) Small Powered Haulage Equipment (e.g., Bobcats and
                Forklifts);
                 (12) Jackhammers;
                 (13) Drills; and
                 (14) Other Occupations.
                 After additional consideration, it was determined that the
                original 14 categories could be further condensed into the final 11
                categories since some of the occupational categories contained job
                codes where the types of tasks and engineering and administrative
                controls were similar enough to be combined.
                 The final 11 occupational categories include:
                 (1) Drillers (e.g., Diamond Drill Operator, Wagon Drill
                Operator, and Drill Helper);
                 (2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting
                Machine Operator, and Cutting Machine Helper);
                 (3) Operators of Large Powered Haulage Equipment (e.g., Trucks,
                Bulldozers, and Scalers);
                 (4) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt
                Vulcanizer);
                 (5) Crushing Equipment and Plant Operators (Crusher Operator/
                Worker, Scalper Screen Operator, and Dry Screen Plant Operator);
                 (6) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill
                Operator, Leaching Operator, and Pelletizer Operator);
                 (7) Operators of Small Powered Haulage Equipment (e.g., Bobcats,
                Shuttle Car, and Forklifts);
                 (8) Packaging Equipment Operators (e.g., Bagging Operator and
                Packaging Operations Worker);
                 (9) Truck Loading Station Tenders (e.g., Dump Operator and Truck
                Loader);
                 (10) Mobile Workers (Laborers, Electricians, Mechanics, and
                Supervisors, etc.); and
                 (11) Miners in Other Occupations (Welder, Dragline Operator,
                Shotcrete/Gunite Man, and Dredge/Barge Operator, etc.).
                 The sampling data for each of the 11 occupational categories
                were then summarized by commodity group (``Metal,'' ``Nonmetal,''
                ``Stone,'' ``Crushed Limestone,'' and ``Sand and Gravel'') based on
                the material being extracted.\93\ The available sampling data were
                then collated for each occupation and commodity and summarized by
                concentration ranges in the exposure profile tables for MNM mines.
                ---------------------------------------------------------------------------
                 \93\ Crushed Limestone and Sand and Gravel were considered
                separately because these commodities make up a large percentage of
                inspection samples. Watts et al. (2012). Respirable crystalline
                silica [Quartz] Concentration Trends in Metal and Nonmetal Mining, J
                Occ Environ Hyg 9:12, 720-732.
                ---------------------------------------------------------------------------
                Attachment 1: Tables for MNM
                [[Page 44983]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.067
                [[Page 44984]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.068
                [[Page 44985]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.069
                [[Page 44986]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.070
                [[Page 44987]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.071
                [[Page 44988]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.072
                [[Page 44989]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.073
                [[Page 44990]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.074
                [[Page 44991]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.075
                [[Page 44992]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.076
                [[Page 44993]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.077
                Attachment 2: Tables for Coal
                [[Page 44994]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.078
                [[Page 44995]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.079
                [[Page 44996]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.080
                [[Page 44997]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.081
                [[Page 44998]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.082
                [[Page 44999]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.083
                [[Page 45000]]
                Attachment 3: Coal Job Codes
                 The complete list of job codes that are found in IAS, as of
                March 11, 2022, are included below, with Table C3-1 listing job
                codes for coal miners. For coal, the first digit of the job code
                identifies where the work is taking place. For example, codes
                starting with 0 represent jobs that occur at the underground face of
                the mine. Job codes that start with 6 were added in 2020.
                0--Underground Section Workers (Face)
                1--General Underground (Non-Face)
                2--Underground Transportation (Non-Face)
                3--Surface
                4--Supervisory and Staff
                5--MSHA--State
                6--Shaft and Slope Sinking
                [GRAPHIC] [TIFF OMITTED] TP13JY23.084
                [[Page 45001]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.085
                [[Page 45002]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.086
                [[Page 45003]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.087
                Attachment 4: MNM Job Codes
                 The complete list of job codes that are found in IAS, as of
                March 11, 2022, are included below with Table C4-1 outlining job
                codes for MNM miners.
                [[Page 45004]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.088
                [[Page 45005]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.089
                [[Page 45006]]
                Attachment 5. Examples of Job Code Pocket Cards
                 Inspectors previously received pocket-sized job code cards for
                use in filling out forms with the correct job code. Now, a drop-down
                menu in IAS is used to select the codes. Table C5-1 contains
                Underground Coal Mining Occupation Codes from Coal Job Code Cards
                used by MESA between 1973 and 1977. Table C5-2 contains Surface
                Occupation Codes from Coal Job Codes used by MESA between 1973 and
                1977.
                [GRAPHIC] [TIFF OMITTED] TP13JY23.090
                [[Page 45007]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.091
                [GRAPHIC] [TIFF OMITTED] TP13JY23.092
                [[Page 45008]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.093
                MNM Job Code Cards (1997)
                 Table C5-3 includes MNM Job Codes from a MNM Job Code Card
                printed in 1997 by the GPO and which referenced a 1981 MSHA form
                (MSHA Form 4000-50, Sept. 1981).
                [[Page 45009]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.094
                [[Page 45010]]
                [GRAPHIC] [TIFF OMITTED] TP13JY23.095
                BILLING CODE 4520-43-C
                List of Subjects
                30 CFR Part 56
                 Chemicals, Electric power, Explosives, Fire prevention, Hazardous
                substances, Incorporation by reference, Metal and nonmetal mining, Mine
                safety and health, Noise control, Reporting and recordkeeping
                requirements, Surface mining.
                30 CFR Part 57
                 Chemicals, Electric power, Explosives, Fire prevention, Gases,
                Hazardous substances, Incorporation by reference, Metal and nonmetal
                mining, Mine safety and health, Noise control, Radiation protection,
                Reporting and recordkeeping requirements, Underground mining.
                30 CFR Part 60
                 Coal, Incorporation by reference, Metal and nonmetal mining,
                Medical surveillance, Mine safety and health, Respirable crystalline
                silica, Reporting and recordkeeping requirements, Surface mining,
                Underground mining.
                30 CFR Part 70
                 Coal, Mine safety and health, Reporting and recordkeeping
                requirements, Respirable dust, Underground coal mines.
                30 CFR Part 71
                 Coal, Mine safety and health, Reporting and recordkeeping
                requirements, Surface coal mines, Underground coal mines.
                30 CFR Part 72
                 Coal, Health standards, Incorporation by reference, Mine safety and
                health, Training, Underground mining.
                30 CFR Part 75
                 Coal, Mine safety and health, Reporting and recordkeeping
                requirements, Underground coal mines, Ventilation.
                [[Page 45011]]
                30 CFR Part 90
                 Coal, Mine safety and health, Reporting and recordkeeping
                requirements, Respirable dust.
                Christopher J. Williamson,
                Assistant Secretary of Labor for Mine Safety and Health.
                 For the reasons discussed in the preamble, the Mine Safety and
                Health Administration is proposing to amend 30 CFR subchapters K, M,
                and O as follows:
                Subchapter K-Metal and Nonmetal Mine Safety and Health
                PART 56--SAFETY AND HEALTH STANDARDS--SURFACE METAL AND NONMETAL
                MINES
                0
                1. The authority citation for part 56 continues to read as follows:
                 Authority: 30 U.S.C. 811.
                Subpart D--Air Quality and Physical Agents
                0
                2. Amend Sec. 56.5001 by revising paragraph (a) to read as follows:
                Sec. 56.5001 Exposure limits for airborne contaminants.
                * * * * *
                 (a) Except as provided in paragraph (b) of this section and in part
                60 of this chapter, the exposure to airborne contaminants shall not
                exceed, on the basis of a time weighted average, the threshold limit
                values adopted by the American Conference of Governmental Industrial
                Hygienists, as set forth and explained in the 1973 edition of the
                Conference's publication, entitled ``TLV's Threshold Limit Values for
                Chemical Substances in Workroom Air Adopted by ACGIH for 1973,'' pages
                1 through 54. This publication is incorporated by reference into this
                section with the approval of the Director of the Federal Register under
                5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or at any MSHA
                Metal and Nonmetal Mine Safety and Health District Office. For
                information on the availability of this material at NARA, visit
                www.archives.gov/federal-register/cfr/ibr-locations.html or email
                [email protected]. The material may be obtained from American
                Conference of Governmental Industrial Hygienists, 1330 Kemper Meadow
                Drive, Attn: Customer Service, Cincinnati, OH 45240; www.acgih.org.
                * * * * *
                0
                3. Amend Sec. 56.5005 by revising the introductory text and paragraphs
                (b) and (c) to read as follows:
                Sec. 56.5005 Control of exposure to airborne contaminants.
                 Control of employee exposure to harmful airborne contaminants shall
                be, insofar as feasible, by prevention of contamination, removal by
                exhaust ventilation, or by dilution with uncontaminated air. However,
                where accepted engineering control measures have not been developed or
                when necessary by the nature of work involved (for example, while
                establishing controls or occasional entry into hazardous atmospheres to
                perform maintenance or investigation), employees may work for
                reasonable periods of time in concentrations of airborne contaminants
                exceeding permissible levels if they are protected by appropriate
                respiratory protective equipment. Whenever respiratory protective
                equipment is used, its selection, fitting, maintenance, cleaning,
                training, supervision, and use shall meet the following minimum
                requirements:
                * * * * *
                 (b) Approved respirators shall be selected, fitted, cleaned, used,
                and maintained in accordance with the requirements, as applicable, of
                ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
                Protection approved August 1, 2019, is incorporated by reference into
                this section with the approval of the Director of the Federal Register
                under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
                Safety and Health Enforcement District Office. For information on the
                availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
                material may be obtained from ASTM International, 100 Barr Harbor
                Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
                 (c) When respiratory protection is used in atmospheres immediately
                dangerous to life or health (IDLH), the presence of at least one other
                person with backup equipment and rescue capability shall be required in
                the event of failure of the respiratory equipment.
                PART 57--SAFETY AND HEALTH STANDARDS--UNDERGROUND METAL AND
                NONMETAL MINES
                0
                4. The authority citation for part 57 continues to read as follows:
                 Authority: 30 U.S.C. 811.
                Subpart D--Air Quality, Radiation, Physical Agents, and Diesel
                Particulate Matter
                0
                5. Amend Sec. 57.5001 by revising paragraph (a) to read as follows:
                Sec. 57.5001 Exposure limits for airborne contaminants.
                * * * * *
                 (a) Except as provided in paragraph (b) of this section and in part
                60 of this chapter, the exposure to airborne contaminants shall not
                exceed, on the basis of a time weighted average, the threshold limit
                values adopted by the American Conference of Governmental Industrial
                Hygienists, as set forth and explained in the 1973 edition of the
                Conference's publication, entitled ``TLV's Threshold Limit Values for
                Chemical Substances in Workroom Air Adopted by ACGIH for 1973,'' pages
                1 through 54. Excursions above the listed thresholds shall not be of a
                greater magnitude than is characterized as permissible by the
                Conference. This publication is incorporated by reference into this
                section with the approval of the Director of the Federal Register under
                5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or any MSHA Metal
                and Nonmetal Mine Safety and Health District Office. For information on
                the availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email
                [email protected]. The material may be obtained from American
                Conference of Governmental Industrial Hygienists by writing to 1330
                Kemper Meadow Drive, Attn: Customer Service, Cincinnati, OH 45240;
                www.acgih.org.
                * * * * *
                0
                6. Amend Sec. 57.5005 by revising the introductory text and paragraphs
                (b) and (c) to read as follows:
                Sec. 57.5005 Control of exposure to airborne contaminants.
                 Control of employee exposure to harmful airborne contaminants shall
                be, insofar as feasible, by prevention of contamination, removal by
                exhaust
                [[Page 45012]]
                ventilation, or by dilution with uncontaminated air. However, where
                accepted engineering control measures have not been developed or when
                necessary by the nature of work involved (for example, while
                establishing controls or occasional entry into hazardous atmospheres to
                perform maintenance or investigation), employees may work for
                reasonable periods of time in concentrations of airborne contaminants
                exceeding permissible levels if they are protected by appropriate
                respiratory protective equipment. Whenever respiratory protective
                equipment is used, its selection, fitting, maintenance, cleaning,
                training, supervision, and use shall meet the following minimum
                requirements:
                * * * * *
                 (b) Approved respirators shall be selected, fitted, cleaned, used,
                and maintained in accordance with the requirements, as applicable, of
                ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
                Protection approved August 1, 2019, is incorporated by reference into
                this section with the approval of the Director of the Federal Register
                under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
                Safety and Health Enforcement District Office. For information on the
                availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
                material may be obtained from ASTM International, 100 Barr Harbor
                Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
                 (c) When respiratory protection is used in atmospheres immediately
                dangerous to life or health (IDLH), the presence of at least one other
                person with backup equipment and rescue capability shall be required in
                the event of failure of the respiratory equipment.
                Subchapter M-Uniform Mine Health Regulations
                0
                7. Add part 60 to subchapter M to read as follows:
                PART 60-RESPIRABLE CRYSTALLINE SILICA
                Sec.
                60.1 Scope; effective date.
                60.2 Definitions.
                60.10 Permissible exposure limit (PEL).
                60.11 Methods of compliance.
                60.12 Exposure monitoring.
                60.13 Corrective actions.
                60.14 Respiratory protection.
                60.15 Medical surveillance for metal and nonmetal miners.
                60.16 Recordkeeping requirements.
                60.17 Severability.
                 Authority: 30 U.S.C. 811, 813(h) and 957.
                Sec. 60.1 Scope; effective date.
                 This part sets forth mandatory health standards for each surface
                and underground metal, nonmetal, and coal mine subject to the Federal
                Mine Safety and Health Act of 1977, as amended. Requirements regarding
                medical surveillance for metal and nonmetal miners are also included.
                The provisions of this part are effective [date 120 days after
                publication of the final rule].
                Sec. 60.2 Definitions.
                 The following definitions apply in this part:
                 Action level means an airborne concentration of respirable
                crystalline silica of 25 micrograms per cubic meter of air ([mu]g/m\3\)
                for a full-shift exposure, calculated as an 8-hour time-weighted
                average (TWA).
                 Objective data means information, such as air monitoring data from
                industry-wide surveys or calculations based on the composition of a
                substance, demonstrating miner exposure to respirable crystalline
                silica associated with a particular product or material or a specific
                process, task, or activity. The data must reflect mining conditions
                closely resembling or with a higher exposure potential than the
                processes, types of material, control methods, work practices, and
                environmental conditions in the operator's current operations.
                 Respirable crystalline silica means quartz, cristobalite, and/or
                tridymite contained in airborne particles that are determined to be
                respirable by a sampling device designed to meet the characteristics
                for respirable-particle-size-selective samplers that conform to the
                International Organization for Standardization (ISO) 7708:1995: Air
                Quality--Particle Size Fraction Definitions for Health-Related
                Sampling.
                 Specialist means an American Board-Certified Specialist in
                Pulmonary Disease or an American Board-Certified Specialist in
                Occupational Medicine.
                Sec. 60.10 Permissible exposure limit (PEL).
                 The mine operator shall ensure that no miner is exposed to an
                airborne concentration of respirable crystalline silica in excess of 50
                [mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA.
                Sec. 60.11 Methods of compliance.
                 (a) The mine operator shall install, use, and maintain feasible
                engineering controls, supplemented by administrative controls when
                necessary, to keep each miner's exposure at or below the PEL, except as
                specified in Sec. 60.14.
                 (b) Rotation of miners shall not be considered an acceptable
                administrative control used for compliance with this part.
                Sec. 60.12 Exposure monitoring.
                 (a) Baseline sampling. (1) The mine operator shall perform baseline
                sampling within the first 180 days after [date 120 days after
                publication of the final rule] to assess the full shift, 8-hour TWA
                exposure of respirable crystalline silica for each miner who is or may
                reasonably be expected to be exposed to respirable crystalline silica.
                 (2) The mine operator is not required to conduct periodic sampling
                under paragraph (b) of this section if the baseline sampling indicates
                that miner exposures are below the action level and if the conditions
                in either paragraph (a)(2)(i) or (ii) of this section are met:
                 (i) One of the following sources from within the preceding 12
                months of baseline sampling indicates that miner exposures are below
                the action level:
                 (A) Sampling conducted by the Secretary; or
                 (B) Mine operator sampling conducted in accordance with paragraphs
                (f) and (g) of this section; or
                 (C) Objective data.
                 (ii) Subsequent sampling that is conducted within 3 months after
                the baseline sampling indicates that miner exposures are below the
                action level.
                 (b) Periodic sampling. Where the most recent sampling indicates
                that miner exposures are at or above the action level but at or below
                the PEL, the mine operator shall sample within 3 months of that
                sampling and continue to sample within 3 months of the previous
                sampling until two consecutive samplings indicate that miner exposures
                are below the action level.
                 (c) Corrective actions sampling. Where the most recent sampling
                indicates that miner exposures are above the PEL, the mine operator
                shall sample after corrective actions taken pursuant to Sec. 60.13
                until the sampling indicates that miner exposures are at or below the
                PEL.
                 (d) Semi-annual evaluation. At least every 6 months after [date one
                year after the effective date of the final rule], mine operators shall
                evaluate any changes in
                [[Page 45013]]
                production, processes, engineering or administrative controls, or other
                factors that may reasonably be expected to result in new or increased
                respirable crystalline silica exposures. Once the evaluation is
                completed, the mine operator shall:
                 (1) Make a record of the evaluation and the date of the evaluation;
                and
                 (2) Post the record on the mine bulletin board and, if applicable,
                by electronic means, for the next 31 days.
                 (e) Post-evaluation sampling. If the mine operator determines as a
                result of the semi-annual evaluation under paragraph (d) of this
                section that miners may be exposed to respirable crystalline silica at
                or above the action level, the mine operator shall perform sampling to
                assess the full shift, 8-hour TWA exposure of respirable crystalline
                silica for each miner who is or may reasonably be expected to be at or
                above the action level.
                 (f) Sampling requirements. (1) Sampling shall be performed for the
                duration of a miner's regular full shift and during typical mining
                activities.
                 (2) The full-shift, 8-hour TWA exposure for such miners shall be
                measured based on:
                 (i) Personal breathing-zone air samples for metal and nonmetal
                operations; or
                 (ii) Occupational environmental samples collected in accordance
                with Sec. 70.201(c) or (b) or Sec. 90.201(b) of this chapter for coal
                operations.
                 (3) Where several miners perform the same tasks on the same shift
                and in the same work area, the mine operator may sample a
                representative fraction (at least two) of these miners to meet the
                requirements in paragraphs (a) through (e) of this section. In sampling
                a representative fraction of miners, the mine operator shall select the
                miners who are expected to have the highest exposure to respirable
                crystalline silica.
                 (4) The mine operator shall use respirable-particle-size-selective
                samplers that conform to ISO 7708:1995 to determine compliance with the
                PEL. ISO 7708:1995, Air Quality--Particle Size Fraction Definitions for
                Health-Related Sampling, Edition 1, 1995-04, is incorporated by
                reference into this section with the approval of the Director of the
                Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. This material
                is available for inspection at the Mine Safety and Health
                Administration (MSHA) and at the National Archives and Records
                Administration (NARA). Contact MSHA at: MSHA's Office of Standards,
                Regulations, and Variances, 201 12th Street South, Arlington, VA 22202-
                5450; 202-693-9440; or any Mine Safety and Health Enforcement District
                Office. For information on the availability of this material at NARA,
                visit www.archives.gov/federal-register/cfr/ibr-locations.html or email
                [email protected]. The material may be obtained from the
                International Organization for Standardization (ISO), CP 56, CH-1211
                Geneva 20, Switzerland; phone: + 41 22 749 01 11; fax: + 41 22 733 34
                30; website: www.iso.org.
                 (g) Methods of sample analysis. (1) The mine operator shall use a
                laboratory that is accredited to ISO/IEC 17025 ``General requirements
                for the competence of testing and calibration laboratories'' with
                respect to respirable crystalline silica analyses, where the
                accreditation has been issued by a body that is compliant with ISO/IEC
                17011 ``Conformity assessment--Requirements for accreditation bodies
                accrediting conformity assessment bodies.''
                 (2) The mine operator shall ensure that the laboratory evaluates
                all samples using respirable crystalline silica analytical methods
                specified by MSHA, the National Institute for Occupational Safety and
                Health (NIOSH), or the Occupational Safety and Health Administration
                (OSHA).
                 (h) Sampling records. For each sample taken pursuant to paragraphs
                (a) through (e) of this section, the mine operator shall make a record
                of the sample date, the occupations sampled, and the concentrations of
                respirable crystalline silica and respirable dust, and post the record
                and the laboratory report on the mine bulletin board and, if
                applicable, by electronic means, for the next 31 days, upon receipt.
                Sec. 60.13 Corrective actions.
                 (a) If any sampling indicates that a miner's exposure exceeds the
                PEL, the mine operator shall:
                 (1) Make approved respirators available to affected miners before
                the start of the next work shift in accordance with Sec. 60.14;
                 (2) Ensure that affected miners wear respirators properly for the
                full shift or during the period of overexposure until miner exposures
                are at or below the PEL; and
                 (3) Immediately take corrective actions to lower the concentration
                of respirable crystalline silica to at or below the PEL.
                 (4) Once corrective actions have been taken, the mine operator
                shall:
                 (i) Conduct sampling pursuant to Sec. 60.12(c); and
                 (ii) Take additional or new corrective actions until sampling
                indicates miner exposures are at or below the PEL.
                 (b) The mine operator shall make a record of corrective actions and
                the dates of the corrective actions under paragraph (a) of this
                section.
                Sec. 60.14 Respiratory protection.
                 (a) Temporary non-routine use of respirators. The mine operator
                shall use respiratory protection as a temporary measure in accordance
                with paragraph (c) of this section. Miners must use respirators when
                working in concentrations of respirable crystalline silica above the
                PEL while:
                 (1) Engineering control measures are being developed and
                implemented; or
                 (2) It is necessary by the nature of work involved.
                 (b) Miners unable to wear respirators. Upon written determination
                by a physician or other licensed health care professional (PLHCP) that
                an affected miner is unable to wear a respirator, the miner shall be
                temporarily transferred either to work in a separate area of the same
                mine or to an occupation at the same mine where respiratory protection
                is not required.
                 (1) The affected miner shall continue to receive compensation at no
                less than the regular rate of pay in the occupation held by that miner
                immediately prior to the transfer.
                 (2) The affected miner may be transferred back to the miner's
                initial work area or occupation when temporary non-routine use of
                respirators under paragraph (a) of this section is no longer required.
                 (c) Respiratory protection requirements. (1) Affected miners shall
                be provided with a NIOSH-approved atmosphere-supplying respirator or
                NIOSH-approved air-purifying respirator equipped with the following:
                 (i) Particulate protection classified as 100 series under 42 CFR
                part 84; or
                 (ii) Particulate protection classified as High Efficiency ``HE''
                under 42 CFR part 84.
                 (2) Approved respirators shall be selected, fitted, used, and
                maintained in accordance with the requirements, as applicable, of ASTM
                F3387-19. ASTM F3387-19, Standard Practice for Respiratory Protection
                approved August 1, 2019, is incorporated by reference into this section
                with the approval of the Director of the Federal Register under 5
                U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
                Safety and Health Enforcement District Office. For information on the
                availability of
                [[Page 45014]]
                this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be
                obtained from ASTM International, 100 Barr Harbor Drive, PO Box C700,
                West Conshohocken, PA 19428-2959; www.astm.org/.
                Sec. 60.15 Medical surveillance for metal and nonmetal miners.
                 (a) Medical surveillance. Each operator of a metal and nonmetal
                mine shall provide to each miner periodic medical examinations
                performed by a physician or other licensed health care professional
                (PLHCP) or specialist, as defined in Sec. 60.2, at no cost to the
                miner.
                 (1) Medical examinations shall be provided at frequencies specified
                in this section.
                 (2) Medical examinations shall include:
                 (i) A medical and work history, with emphasis on: past and present
                exposure to respirable crystalline silica, dust, and other agents
                affecting the respiratory system; any history of respiratory system
                dysfunction, including diagnoses and symptoms of respiratory disease
                (e.g., shortness of breath, cough, wheezing); history of tuberculosis;
                and smoking status and history;
                 (ii) A physical examination with special emphasis on the
                respiratory system;
                 (iii) A chest X-ray (a single posteroanterior radiographic
                projection or radiograph of the chest at full inspiration recorded on
                either film (no less than 14 x 17 inches and no more than 16 x 17
                inches) or digital radiography systems), classified according to the
                International Labour Office (ILO) International Classification of
                Radiographs of Pneumoconioses by a NIOSH-certified B Reader; and
                 (iv) A pulmonary function test to include forced vital capacity
                (FVC) and forced expiratory volume in one second (FEV1) and
                FEV1/FVC ratio, administered by a spirometry technician with
                a current certificate from a NIOSH-approved Spirometry Program Sponsor.
                 (b) Voluntary medical examinations. Each mine operator shall
                provide the opportunity to have the medical examinations specified in
                paragraph (a) of this section at least every 5 years to all miners
                employed at the mine. The medical examinations shall be available
                during a 6-month period that begins no less than 3.5 years and not more
                than 4.5 years from the end of the last 6-month period.
                 (c) Mandatory medical examinations. For each miner who begins work
                in the mining industry for the first time, the mine operator shall
                provide medical examinations specified in paragraph (a) of this section
                as follows:
                 (1) An initial medical examination no later than 30 days after
                beginning employment;
                 (2) A follow-up medical examination no later than 3 years after the
                initial examination in paragraph (c)(1) of this section; and
                 (3) A follow-up medical examination conducted by a specialist no
                later than 2 years after the examinations in paragraph (c)(2) of this
                section if the chest X-ray shows evidence of pneumoconiosis or the
                spirometry examination indicates evidence of decreased lung function.
                 (d) Medical examinations results. The results of medical
                examinations or tests made pursuant to this section shall be provided
                only to the miner, and at the request of the miner, to the miner's
                designated physician.
                 (e) Written medical opinion. The mine operator shall obtain a
                written medical opinion from the PLHCP or specialist within 30 days of
                the medical examination. The written opinion shall contain only the
                following:
                 (1) The date of the medical examination;
                 (2) A statement that the examination has met the requirements of
                this section; and
                 (3) Any recommended limitations on the miner's use of respirators.
                 (f) Written medical opinion records. The mine operator shall
                maintain a record of the written medical opinions received from the
                PLHCP or specialist under paragraph (e) of this section.
                Sec. 60.16 Recordkeeping requirements.
                 (a) Table 1 to this paragraph (a) lists the records the mine
                operator shall retain and their retention period.
                 (1) Evaluation records made under Sec. 60.12(d) shall be retained
                for at least 2 years from the date of each evaluation.
                 (2) Sampling records made under Sec. 60.12(h) shall be retained
                for at least 2 years from the sample date.
                 (3) Corrective action records made under Sec. 60.13(b) shall be
                retained for at least 2 years from the date of each corrective action.
                These records must be stored with the records of related sampling under
                Sec. 60.12(h).
                 (4) Written determination records received from a PLHCP under Sec.
                60.14(b) shall be retained for the duration of the miner's employment
                plus 6 months.
                 (5) Written medical opinion records received from a PLHCP or
                specialist under Sec. 60.15(f) shall be retained for the duration of
                the miner's employment plus 6 months.
                 Table 1 to Paragraph (a)--Recordkeeping Requirements
                ------------------------------------------------------------------------
                 Record Section references Retention period
                ------------------------------------------------------------------------
                1. Evaluation records........... Sec. 60.12(d)... At least 2 years
                 from date of each
                 evaluation.
                2. Sampling records............. Sec. 60.12(h)... At least 2 years
                 from sample date.
                3. Corrective action records.... Sec. 60.13(b)... At least 2 years
                 from date of each
                 corrective
                 action.
                4. Written determination records Sec. 60.14(b)... Duration of
                 received from a PLHCP. miner's
                 employment plus 6
                 months.
                5. Written medical opinion Sec. 60.15(f)... Duration of
                 records received from a PLHCP miner's
                 or specialist. employment plus 6
                 months.
                ------------------------------------------------------------------------
                 (b) Upon request from an authorized representative of the
                Secretary, from an authorized representative of miners, or from miners,
                mine operators shall promptly provide access to any record listed in
                this section.
                Sec. 60.17 Severability.
                 Each section of this part, as well as sections in 30 CFR parts 56,
                57, 70, 71, 72, 75, and 90 that address respirable crystalline silica
                or respiratory protection, is separate and severable from the other
                sections and provisions. If any provision of this subpart is held to be
                invalid or unenforceable by its terms, or as applied to any person,
                entity, or circumstance, or is stayed or enjoined, that provision shall
                be construed so as to continue to give the maximum effect to the
                provision permitted by law, unless such holding shall be one of utter
                invalidity or unenforceability, in which event the provision shall be
                severable from these
                [[Page 45015]]
                sections and shall not affect the remainder thereof.
                Subchapter O--Coal Mine Safety and Health
                PART 70--MANDATORY HEALTH STANDARDS--UNDERGROUND COAL MINES
                0
                8. The authority citation for part 70 continues to read as follows:
                 Authority: 30 U.S.C. 811, 813(h), 957.
                Subpart A--General
                Sec. 70.2 [Amended]
                0
                9. Amend Sec. 70.2 by removing the definition of ``Quartz''.
                Subpart B--Dust Standards
                Sec. 70.101 [Removed and Reserved]
                0
                10. Remove and reserve Sec. 70.101.
                Subpart C--Sampling Procedures
                0
                11. Amend Sec. 70.205 by revising paragraph (c) to read as follows:
                Sec. 70.205 Approved sampling devices; operation; air flowrate.
                * * * * *
                 (c) If using a CPDM, the person certified in sampling shall monitor
                the dust concentrations and the sampling status conditions being
                reported by the sampling device at mid-shift or more frequently as
                specified in the approved mine ventilation plan to assure: The sampling
                device is in the proper location and operating properly; and the work
                environment of the occupation or DA being sampled remains in compliance
                with the standard at the end of the shift. This monitoring is not
                required if the sampling device is being operated in an anthracite coal
                mine using the full box, open breast, or slant breast mining method.
                Sec. 70.206 [Removed and Reserved]
                0
                12. Remove and reserve Sec. 70.206.
                Sec. 70.207 [Removed and Reserved]
                0
                13. Remove and reserve Sec. 70.207.
                0
                14. Amend Sec. 70.208 by:
                0
                a. Removing and reserving paragraph (c);
                0
                b. Revising paragraphs (d), (e) introductory text, (e)(2), (f), (g),
                (h) introductory text, (h)(2), (i) introductory text, and (i)(1); and
                0
                c. Adding table 1.
                 The revisions and addition read as follows:
                Sec. 70.208 Quarterly sampling; mechanized mining units.
                * * * * *
                 (d) If a normal production shift is not achieved, the DO or ODO
                sample for that shift may be voided by MSHA. However, any sample,
                regardless of production, that exceeds the standard by at least 0.1 mg/
                m\3\ shall be used in the determination of the equivalent concentration
                for that occupation.
                 (e) When a valid representative sample taken in accordance with
                this section meets or exceeds the ECV in table 1 to this section that
                corresponds to the particular sampling device used, the operator shall:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable dust to at or below the respirable dust standard; and
                * * * * *
                 (f) Noncompliance with the standard is demonstrated during the
                sampling period when:
                 (1) Three or more valid representative samples meet or exceed the
                ECV in table 1 to this section that corresponds to the particular
                sampling device used; or
                 (2) The average for all valid representative samples meets or
                exceeds the ECV in table 1 to this section that corresponds to the
                particular sampling device used.
                 (g)(1) Unless otherwise directed by the District Manager, upon
                issuance of a citation for a violation of the standard involving a DO
                in an MMU, paragraph (a)(1) of this section shall not apply to the DO
                in that MMU until the violation is abated and the citation is
                terminated in accordance with paragraphs (h) and (i) of this section.
                 (2) Unless otherwise directed by the District Manager, upon
                issuance of a citation for a violation of the standard involving a type
                of ODO in an MMU, paragraph (a)(2) of this section shall not apply to
                that ODO type in that MMU until the violation is abated and the
                citation is terminated in accordance with paragraphs (h) and (i) of
                this section.
                 (h) Upon issuance of a citation for violation of the standard, the
                operator shall take the following actions sequentially:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable coal mine dust to at or below the standard; and
                * * * * *
                 (i) A citation for a violation of the standard shall be terminated
                by MSHA when:
                 (1) Each of the five valid representative samples is at or below
                the standard; and
                * * * * *
                 Table 1 to Sec. 70.208--Excessive Concentration Values (ECV) Based on a Single Sample, Three Samples, or the
                 Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
                ----------------------------------------------------------------------------------------------------------------
                 ECV (mg/m\3\)
                 Section Samples -------------------------------
                 CMDPSU CPDM
                ----------------------------------------------------------------------------------------------------------------
                70.208 (e)................................. 70.100(a)--Single sample........... 1.79 1.70
                 70.100(b)--Single sample........... 0.74 0.57
                70.208(f)(1)............................... 70.100(a)--3 or more samples....... 1.79 1.70
                 70.100(b)--3 or more samples....... 0.74 0.57
                70.208(f)(2)............................... 70.100(a)--5 sample average........ 1.63 1.59
                 70.100(b)--5 sample average........ 0.61 0.53
                70.208(f)(2)............................... 70.100(a)--15 sample average....... 1.58 1.56
                 70.100(b)--15 sample average....... 0.57 0.52
                70.208(i)(1)............................... 70.100(a)--Each of 5 samples....... 1.79 1.70
                 70.100(b)--Each of 5 samples....... 0.74 0.57
                ----------------------------------------------------------------------------------------------------------------
                0
                15. Amend Sec. 70.209 by:
                0
                a. Removing and reserving paragraph (b);
                0
                b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f)
                introductory text, (f)(2), (g) introductory text, and (g)(1); and
                0
                c. Adding table 1.
                 The revisions and addition read as follows:
                [[Page 45016]]
                Sec. 70.209 Quarterly sampling; designated areas.
                * * * * *
                 (c) When a valid representative sample taken in accordance with
                this section meets or exceeds the ECV in table 1 to this section that
                corresponds to the particular sampling device used, the operator shall:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable dust to at or below the respirable dust standard; and
                * * * * *
                 (d) Noncompliance with the standard is demonstrated during the
                sampling period when:
                 (1) Two or more valid representative samples meet or exceed the ECV
                in table 1 to this section that corresponds to the particular sampling
                device used; or
                 (2) The average for all valid representative samples meets or
                exceeds the ECV in table 1 to this section that corresponds to the
                particular sampling device used.
                 (e) Unless otherwise directed by the District Manager, upon
                issuance of a citation for a violation of the standard, paragraph (a)
                of this section shall not apply to that DA until the violation is
                abated and the citation is terminated in accordance with paragraphs (f)
                and (g) of this section.
                 (f) Upon issuance of a citation for a violation of the standard,
                the operator shall take the following actions sequentially:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable coal mine dust to at or below the standard; and
                * * * * *
                 (g) A citation for a violation of the standard shall be terminated
                by MSHA when:
                 (1) Each of the five valid representative samples is at or below
                the standard; and
                * * * * *
                 Table 1 to Sec. 70.209--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                 Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
                ----------------------------------------------------------------------------------------------------------------
                 ECV (mg/m\3\)
                 Section Samples -------------------------------
                 CMDPSU CPDM
                ----------------------------------------------------------------------------------------------------------------
                70.209 (c)................................. 70.100(a)--Single sample........... 1.79 1.70
                 70.100(b)--Single sample........... 0.74 0.57
                70.209(d)(1)............................... 70.100(a)--2 or more samples....... 1.79 1.70
                 70.100(b)--2 or more samples....... 0.74 0.57
                70.209(d)(2)............................... 70.100(a)--5 sample average........ 1.63 1.59
                 70.100(b)--5 sample average........ 0.61 0.53
                70.209(d)(2)............................... 70.100(a)--15 sample average....... 1.58 1.56
                 70.100(b)--15 sample average....... 0.57 0.52
                70.209(g)(1)............................... 70.100(a)--Each of 5 samples....... 1.79 1.70
                 70.100(b)--Each of 5 samples....... 0.74 0.57
                ----------------------------------------------------------------------------------------------------------------
                Table 70--1 to Subpart C of Part 70 [Removed]
                0
                16. Remove table 70-1 to subpart C of part 70.
                Table 70--2 to Subpart C of Part 70 [Removed]
                0
                17. Remove table 70-2 to subpart C of part 70.
                PART 71--MANDATORY HEALTH STANDARDS--SURFACE COAL MINES AND SURFACE
                WORK AREAS OF UNDERGROUND COAL MINES
                0
                18. The authority citation for part 71 continues to read as follows:
                 Authority: 30 U.S.C. 811, 813(h), 957.
                Subpart A--General
                Sec. 71.2 [Amended]
                0
                19. Amend Sec. 71.2 by removing the definition of ``Quartz''.
                Subpart B--Dust Standards
                Sec. 71.101 [Removed and Reserved]
                0
                20. Remove and reserve Sec. 71.101.
                Subpart C--Sampling Procedures
                0
                21. Amend Sec. 71.205 by revising paragraph (c) to read as follows:
                Sec. 71.205 Approved sampling devices; operation; air flowrate.
                * * * * *
                 (c) If using a CPDM, the person certified in sampling shall monitor
                the dust concentrations and the sampling status conditions being
                reported by the sampling device at mid-shift or more frequently as
                specified in the approved respirable dust control plan, if applicable,
                to assure: The sampling device is in the proper location and operating
                properly; and the work environment of the occupation being sampled
                remains in compliance with the standard at the end of the shift.
                0
                22. Amend Sec. 71.206 by:
                0
                a. Removing and reserving paragraph (b);
                0
                b. Revising paragraphs (e), (g), (h) introductory text, (h)(2), (i),
                (j), (k) introductory text, (k)(2), and (l);
                0
                c. Removing tables 71-1 and 71-2;
                0
                d. Revising paragraphs (m) and (n); and
                0
                e. Adding table 1.
                 The revisions and addition read as follows:
                Sec. 71.206 Quarterly sampling; designated work positions.
                * * * * *
                 (e) Each DWP sample shall be taken on a normal work shift. If a
                normal work shift is not achieved, the respirable dust sample shall be
                transmitted to MSHA with a notation by the person certified in sampling
                on the back of the dust data card stating that the sample was not taken
                on a normal work shift. When a normal work shift is not achieved, the
                sample for that shift may be voided by MSHA. However, any sample,
                regardless of whether a normal work shift was achieved, that exceeds
                the standard by at least 0.1 mg/m\3\ shall be used in the determination
                of the equivalent concentration for that occupation.
                * * * * *
                 (g) Upon notification from MSHA that any valid representative
                sample taken from a DWP to meet the requirements of paragraph (a) of
                this section exceeds the standard, the operator shall, within 15
                calendar days of notification, sample that DWP each normal work shift
                until five valid representative samples are
                [[Page 45017]]
                taken. The operator shall begin sampling on the first normal work shift
                following receipt of notification.
                 (h) When a valid representative sample taken in accordance with
                this section meets or exceeds the excessive concentration value (ECV)
                in table 1 to this section that corresponds to the particular sampling
                device used, the mine operator shall:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable coal mine dust to at or below the standard; and
                * * * * *
                 (i) Noncompliance with the standard is demonstrated during the
                sampling period when:
                 (1) Two or more valid representative samples meet or exceed the ECV
                in table 1 to this section that corresponds to the particular sampling
                device used; or
                 (2) The average for all valid representative samples meets or
                exceeds the ECV in table 1 to this section that corresponds to the
                particular sampling device used.
                 (j) Unless otherwise directed by the District Manager, upon
                issuance of a citation for a violation of the standard, paragraph (a)
                of this section shall not apply to that DWP until the violation is
                abated and the citation is terminated in accordance with paragraphs (k)
                and (l) of this section.
                 (k) Upon issuance of a citation for violation of the standard, the
                operator shall take the following actions sequentially:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable coal mine dust to at or below the standard; and
                * * * * *
                 (l) A citation for violation of the standard shall be terminated by
                MSHA when the equivalent concentration of each of the five valid
                representative samples is at or below the standard.
                 (m) The District Manager may designate for sampling under this
                section additional work positions at a surface coal mine and at a
                surface work area of an underground coal mine where a concentration of
                respirable dust exceeding 50 percent of the standard has been measured
                by one or more MSHA valid representative samples.
                 (n) The District Manager may withdraw from sampling any DWP
                designated for sampling under paragraph (m) of this section upon
                finding that the operator is able to maintain continuing compliance
                with the standard. This finding shall be based on the results of MSHA
                and operator valid representative samples taken during at least a 12-
                month period.
                 Table 1 to Sec. 71.206--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                 Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
                ----------------------------------------------------------------------------------------------------------------
                 ECV (mg/m\3\)
                 Section Samples -------------------------------
                 CMDPSU CPDM
                ----------------------------------------------------------------------------------------------------------------
                71.206(h)..................................... Single sample................... 1.79 1.70
                71.206(i)(1).................................. 2 or more samples............... 1.79 1.70
                71.206(i)(2).................................. 5 sample average................ 1.63 1.59
                71.206(l)..................................... Each of 5 samples............... 1.79 1.70
                ----------------------------------------------------------------------------------------------------------------
                Subpart D--Respirable Dust Control Plans
                0
                23. Amend Sec. 71.300 by revising paragraph (a) introductory text to
                read as follows:
                Sec. 71.300 Respirable dust control plan; filing requirements.
                 (a) Within 15 calendar days after the termination date of a
                citation for violation of the standard, the operator shall submit to
                the District Manager for approval a written respirable dust control
                plan applicable to the DWP identified in the citation. The respirable
                dust control plan and revisions thereof shall be suitable to the
                conditions and the mining system of the coal mine and shall be adequate
                to continuously maintain respirable dust to at or below the standard at
                the DWP identified in the citation.
                * * * * *
                0
                24. Amend Sec. 71.301 by revising paragraph (a)(1) to read as follows:
                Sec. 71.301 Respirable dust control plan; approval by District
                Manager and posting.
                 (a) * * *
                 (1) The respirable dust control measures would be likely to
                maintain concentrations of respirable coal mine dust at or below the
                standard; and
                * * * * *
                PART 72--HEALTH STANDARDS FOR COAL MINES
                0
                25. The authority citation for part 72 continues to read as follows:
                 Authority: 30 U.S.C. 811, 813(h), 957.
                Subpart E--Miscellaneous
                0
                26. Revise Sec. 72.710 to read as follows:
                Sec. 72.710 Selection, fit, use, and maintenance of approved
                respirators.
                 Approved respirators shall be selected, fitted, used, and
                maintained in accordance with the provisions of a respiratory
                protection program consistent with the requirements, as applicable, of
                ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory
                Protection approved August 1, 2019, is incorporated by reference into
                this section with the approval of the Director of the Federal Register
                under 5 U.S.C. 552(a) and 1 CFR part 51. This material is available for
                inspection at the Mine Safety and Health Administration (MSHA) and at
                the National Archives and Records Administration (NARA). Contact MSHA
                at: MSHA's Office of Standards, Regulations, and Variances, 201 12th
                Street South, Arlington, VA 22202-5450; 202-693-9440; or any Mine
                Safety and Health Enforcement District Office. For information on the
                availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The
                material may be obtained from ASTM International, 100 Barr Harbor
                Drive, P.O. Box C700, West Conshohocken, PA 19428-2959; www.astm.org/.
                0
                27. Revise Sec. 72.800 to read as follows:
                Sec. 72.800 Single, full-shift measurement of respirable coal mine
                dust.
                 The Secretary will use a single, full-shift measurement of
                respirable coal mine dust to determine the average concentration on a
                shift since that measurement accurately represents atmospheric
                conditions to which a miner is exposed during such shift. Noncompliance
                with the respirable dust standard, in accordance with this subchapter,
                is demonstrated when a single, full-shift measurement taken by
                [[Page 45018]]
                MSHA meets or exceeds the applicable ECV in table 1 to Sec. 70.208,
                table 1 to Sec. 70.209, table 1 to Sec. 71.206, or table 1 to Sec.
                90.207 of this chapter that corresponds to the particular sampling
                device used. Upon issuance of a citation for a violation of the
                standard, and for MSHA to terminate the citation, the mine operator
                shall take the specified actions in this subchapter.
                PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES
                0
                28. The authority citation for part 75 continues to read as follows:
                 Authority: 30 U.S.C. 811, 813(h), 957.
                Subpart D--Ventilation
                0
                29. Amend Sec. 75.350 by:
                0
                a. Revising paragraph (b)(3)(i);
                0
                b. Removing paragraph (b)(3)(ii); and
                0
                c. Redesignating (b)(3)(iii) as (b)(3)(ii).
                 The revision reads as follows:
                Sec. 75.350 Belt air course ventilation.
                * * * * *
                 (b) * * *
                 (3) * * *
                 (i) The average concentration of respirable dust in the belt air
                course, when used as a section intake air course, shall be maintained
                at or below 0.5 milligrams per cubic meter of air (mg/m\3\).
                * * * * *
                PART 90--MANDATORY HEALTH STANDARDS--COAL MINERS WHO HAVE EVIDENCE
                OF THE DEVELOPMENT OF PNEUMOCONIOSIS
                0
                30. The authority citation for part 90 continues to read as follows:
                 Authority: 30 U.S.C. 811, 813(h), 957.
                Subpart A--General
                0
                31. Amend Sec. 90.2 by revising the definition of ``Part 90 miner''
                and removing the definition of ``Quartz''.
                 The revision reads as follows:
                Sec. 90.2 Definitions.
                * * * * *
                 Part 90 miner. A miner employed at a coal mine who has exercised
                the option under the old section 203(b) program (36 FR 20601 preview
                citation details, October 27, 1971), or under Sec. 90.3 to work in an
                area of a mine where the average concentration of respirable dust in
                the mine atmosphere during each shift to which that miner is exposed is
                continuously maintained at or below the standard, and who has not
                waived these rights.
                * * * * *
                0
                32. Amend Sec. 90.3 by revising paragraph (a) to read as follows:
                Sec. 90.3 Part 90 option; notice of eligibility; exercise of option.
                 (a) Any miner employed at a coal mine who, in the judgment of the
                Secretary of HHS, has evidence of the development of pneumoconiosis
                based on a chest X-ray, read and classified in the manner prescribed by
                the Secretary of HHS, or based on other medical examinations shall be
                afforded the option to work in an area of a mine where the average
                concentration of respirable dust in the mine atmosphere during each
                shift to which that miner is exposed is continuously maintained at or
                below the standard. Each of these miners shall be notified in writing
                of eligibility to exercise the option.
                * * * * *
                Subpart B--Dust Standards, Rights of Part 90 Miners
                Sec. 90.101 [Removed and Reserved]
                0
                33. Remove and reserve Sec. 90.101.
                0
                34. Amend Sec. 90.102 by revising paragraph (a) to read as follows:
                Sec. 90.102 Transfer; notice.
                 (a) Whenever a Part 90 miner is transferred in order to meet the
                standard, the operator shall transfer the miner to an existing position
                at the same coal mine on the same shift or shift rotation on which the
                miner was employed immediately before the transfer. The operator may
                transfer a Part 90 miner to a different coal mine, a newly created
                position or a position on a different shift or shift rotation if the
                miner agrees in writing to the transfer. The requirements of this
                paragraph do not apply when the respirable dust concentration in a Part
                90 miner's work position complies with the standard but circumstances,
                such as reductions in workforce or changes in operational status,
                require a change in the miner's job or shift assignment.
                * * * * *
                0
                35. Amend Sec. 90.104 by revising paragraph (a)(2) to read as follows:
                Sec. 90.104 Waiver of rights; re-exercise of option.
                 (a) * * *
                 (2) Applying for and accepting a position in an area of a mine
                which the miner knows has an average respirable dust concentration
                exceeding the standard; or
                * * * * *
                Subpart C--Sampling Procedures
                0
                36. Amend Sec. 90.205 by revising paragraph (c) to read as follows:
                Sec. 90.205 Approved sampling devices; operation; air flowrate.
                * * * * *
                 (c) If using a CPDM, the person certified in sampling shall monitor
                the dust concentrations and the sampling status conditions being
                reported by the sampling device at mid-shift or more frequently as
                specified in the approved respirable dust control plan, if applicable,
                to assure: The sampling device is in the proper location and operating
                properly; and the work environment of the Part 90 miner being sampled
                remains in compliance with the standard at the end of the shift. This
                monitoring is not required if the sampling device is being operated in
                an anthracite coal mine using the full box, open breast, or slant
                breast mining method.
                0
                37. Amend Sec. 90.206 by revising paragraphs (b) and (c) to read as
                follows:
                Sec. 90.206 Exercise of option or transfer sampling.
                * * * * *
                 (b) Noncompliance with the standard shall be determined in
                accordance with Sec. 90.207(d).
                 (c) Upon issuance of a citation for a violation of the standard,
                the operator shall comply with Sec. 90.207(f).
                0
                38. Amend Sec. 90.207 by:
                0
                a. Removing and reserving paragraph (b);
                0
                b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f)
                introductory text, (f)(2) introductory text, (f)(2)(ii), and (g);
                0
                c. Removing tables 90-1 and 90-2; and
                0
                d. Adding table 1.
                 The revisions and addition read as follows:
                Sec. 90.207 Quarterly sampling.
                * * * * *
                 (c) When a valid representative sample taken in accordance with
                this section meets or exceeds the ECV in table 1 to this section
                corresponding to the particular sampling device used, the mine operator
                shall:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable coal mine dust to below the standard; and
                * * * * *
                 (d) Noncompliance with the standard is demonstrated during the
                sampling period when:
                 (1) Two or more valid representative samples meet or exceed the ECV
                in table 1 to this section that corresponds to the particular sampling
                device used; or
                 (2) The average for all valid representative samples meets or
                exceeds
                [[Page 45019]]
                the ECV in table 1 to this section that corresponds to the particular
                sampling device used.
                 (e) Unless otherwise directed by the District Manager, upon
                issuance of a citation for a violation of the standard, paragraph (a)
                of this section shall not apply to that Part 90 miner until the
                violation is abated and the citation is terminated in accordance with
                paragraphs (f) and (g) of this section.
                 (f) Upon issuance of a citation for a violation of the standard,
                the operator shall take the following actions sequentially:
                * * * * *
                 (2) Immediately take corrective action to lower the concentration
                of respirable dust to below the standard. If the corrective action
                involves:
                * * * * *
                 (ii) Transferring the Part 90 miner to another work position at the
                mine to meet the standard, the operator shall comply with Sec. 90.102
                and then sample the affected miner in accordance with Sec. 90.206(a).
                * * * * *
                 (g) A citation for a violation of the standard shall be terminated
                by MSHA when the equivalent concentration of each of the five valid
                representative samples is below the standard.
                 Table 1 to Sec. 90.207--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                 Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
                ----------------------------------------------------------------------------------------------------------------
                 ECV (mg/m\3\)
                 Section Samples -------------------------------
                 CMDPSU CPDM
                ----------------------------------------------------------------------------------------------------------------
                90.207(c)..................................... Single sample................... 0.74 0.57
                90.207(d)(1).................................. 2 or more samples............... 0.74 0.57
                90.207(d)(2).................................. 5 sample average................ 0.61 0.53
                90.207(g)..................................... Each of 5 samples............... 0.74 0.57
                ----------------------------------------------------------------------------------------------------------------
                Subpart D--Respirable Dust Control Plans
                0
                39. Amend Sec. 90.300 by revising paragraphs (a) and (b)(3) to read as
                follows:
                Sec. 90.300 Respirable dust control plan; filing requirements.
                 (a) If an operator abates a violation of the standard by reducing
                the respirable dust level in the position of the Part 90 miner, the
                operator shall submit to the District Manager for approval a written
                respirable dust control plan for the Part 90 miner in the position
                identified in the citation within 15 calendar days after the citation
                is terminated. The respirable dust control plan and revisions thereof
                shall be suitable to the conditions and the mining system of the coal
                mine and shall be adequate to continuously maintain respirable dust
                below the standard for that Part 90 miner.
                 (b) * * *
                 (3) A detailed description of how each of the respirable dust
                control measures used to continuously maintain concentrations of
                respirable coal mine dust below the standard; and
                * * * * *
                0
                40. Amend Sec. 90.301 by revising paragraphs (a)(1) and (b) to read as
                follows:
                Sec. 90.301 Respirable dust control plan; approval by District
                Manager; copy to part 90 miner.
                 (a) * * *
                 (1) The respirable dust control measures would be likely to
                maintain concentrations of respirable coal mine dust below the
                standard; and
                * * * * *
                 (b) MSHA may take respirable dust samples to determine whether the
                respirable dust control measures in the operator's plan effectively
                maintain concentrations of respirable coal mine dust below the
                standard.
                * * * * *
                [FR Doc. 2023-14199 Filed 7-6-23; 11:15 am]
                BILLING CODE 4520-43-P
                

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