Pesticides; emergency exemptions, etc.: methylheptyl ester,

[Federal Register: September 17, 2001 (Volume 66, Number 180)]

[Rules and Regulations]

[Page 47964-47971]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[DOCID:fr17se01-4]

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 180

[OPP-301164; FRL-6798-5]

RIN 2070-AB78

Fluroxypyr 1-Methylheptyl Ester; Pesticide Tolerances for Emergency Exemptions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

SUMMARY: This regulation establishes time-limited tolerances for the combined residues of fluroxypyr 1-methylheptyl ester and its metabolite fluroxypyr, free and conjugated, all expressed as fluroxypyr in or on grass, forage and grass, hay and modifies the existing permanent tolerances for milk and for kidney of cattle, goat, hog, horse, and sheep. This action is in response to EPA's granting of an emergency exemption under section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act authorizing use of the pesticide on pastures and rangeland. This regulation establishes maximum permissible levels for residues of fluroxypyr 1-methylheptyl ester and its metabolite fluroxypyr, free and conjugated, all expressed as fluroxypyr in these food commodities. The tolerances will expire and are revoked on June 30, 2003.

DATES: This regulation is effective September 17, 2001. Objections and requests for hearings, identified by docket control number OPP-301164, must be received by EPA on or before November 16, 2001.

ADDRESSES: Written objections and hearing requests may be submitted by mail, in person, or by courier. Please follow the detailed instructions for each method as provided in Unit VII. of the SUPPLEMENTARY INFORMATION. To ensure proper receipt by EPA, your objections and hearing requests must identify docket control number OPP-301164 in the subject line on the first page of your response.

FOR FURTHER INFORMATION CONTACT: By mail: Andrew Ertman, Registration Division (7505C), Office of Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460; telephone number: (703) 308-9367, and e-mail address: ertman.andrew@epa.gov.

SUPPLEMENTARY INFORMATION:

1. General Information

   1. Does this Action Apply to Me?

      You may be potentially affected by this action if you are an agricultural producer, food manufacturer, or pesticide manufacturer. Potentially affected categories and entities may include, but are not limited to:

      Examples of Categories

      NAICS codes

      potentially affected entities

      Industry

      111

      Crop production .............................. 112

      Animal production 311

      Food manufacturing .............................. 32532

      Pesticide manufacturing

      This listing is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action. Other types of entities not listed in the table could also be affected. The North American Industrial Classification System (NAICS) codes have been provided to assist you and others in determining whether or not this action might apply to certain entities. If you have questions regarding the applicability of this action to a particular entity, consult the person listed under FOR FURTHER INFORMATION CONTACT.

   2. How Can I Get Additional Information, Including Copies of This Document and Other Related Documents?

      1. Electronically. You may obtain electronic copies of this document, and certain other related documents that might be available electronically, from the EPA Internet Home Page at http://www.epa.gov/. To access this document, on the Home Page select ``Laws and Regulations,'' ``Regulations and Proposed Rules,'' and then look up the entry for this document under the ``Federal Register--Environmental Documents.'' You can also go directly to the Federal Register listings at http://www.epa.gov/fedrgstr/. A frequently updated electronic version of 40 CFR part 180 is available at http://www.access.gpo.gov/ nara/cfr/cfrhtml_00/Title_40/40cfr180_00.html, a beta site currently under development.

      2. In person. The Agency has established an official record for this action under docket control number OPP-301164. The official record consists of the documents specifically referenced in this action, and other information related to this action, including any information claimed as Confidential Business Information (CBI). This official record includes the documents that are physically located in the docket, as well as the documents that are referenced in those documents. The public version of the official record does not include any information claimed as CBI. The public version of the official record, which includes printed, paper versions of any electronic comments submitted during an applicable comment period is available for inspection in the Public Information and Records Integrity Branch (PIRIB), Rm. 119, Mall #2, 1921 Jefferson Davis Hwy., Arlington, VA, from 8:30 a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The PIRIB telephone number is (703) 305-5805.

2. Background and Statutory Findings

   EPA, on its own initiative, in accordance with sections 408(e) and 408 (l)(6) of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a, is establishing tolerances for the combined residues of the herbicide fluroxypyr 1-methylheptyl ester and its metabolite fluroxypyr, free and

   [[Page 47965]]

   conjugated, all expressed as fluroxypyr, in or on grass, forage at 120 part per million (ppm), grass, hay at 160 ppm, and modifying the permanent tolerances for milk from 0.1 ppm to 0.30 ppm and for kidney (cattle, goat, hog, horse, and sheep) from 0.5 ppm to 1.5 ppm. These tolerances will expire and are revoked on June 30, 2003. EPA will publish a document in the Federal Register to remove the revoked tolerances from the Code of Federal Regulations.

   Section 408(l)(6) of the FFDCA requires EPA to establish a time- limited tolerance or exemption from the requirement for a tolerance for pesticide chemical residues in food that will result from the use of a pesticide under an emergency exemption granted by EPA under section 18 of FIFRA. Such tolerances can be established without providing notice or period for public comment. EPA does not intend for its actions on section 18 related tolerances to set binding precedents for the application of section 408 and the new safety standard to other tolerances and exemptions. Section 408(e) of the FFDCA allows EPA to establish a tolerance or an exemption from the requirement of a tolerance on its own initiative, i.e., without having received any petition from an outside party.

   Section 408(b)(2)(A)(i) of the FFDCA allows EPA to establish a tolerance (the legal limit for a pesticide chemical residue in or on a food) only if EPA determines that the tolerance is ``safe.'' Section 408(b)(2)(A)(ii) defines ``safe'' to mean that ``there is a reasonable certainty that no harm will result from aggregate exposure to the pesticide chemical residue, including all anticipated dietary exposures and all other exposures for which there is reliable information.'' This includes exposure through drinking water and in residential settings, but does not include occupational exposure. Section 408(b)(2)(C) requires EPA to give special consideration to exposure of infants and children to the pesticide chemical residue in establishing a tolerance and to ``ensure that there is a reasonable certainty that no harm will result to infants and children from aggregate exposure to the pesticide chemical residue. . . .''

   Section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizes EPA to exempt any Federal or State agency from any provision of FIFRA, if EPA determines that ``emergency conditions exist which require such exemption.'' This provision was not amended by the Food Quality Protection Act (FQPA). EPA has established regulations governing such emergency exemptions in 40 CFR part 166.

3. Emergency Exemption for Fluroxypyr on Pastures and Rangeland and FFDCA Tolerances

   Sericea lespedeza (also known as Chinese bush clover) is a perennial legume native to Asia that was introduced into the United States in 1896 for use as forage for livestock and as an erosion control plant. It was first recognized as a potential weed problem in southeast Kansas in the early 1980s. The Kansas Legislature made sericea lespedeza a statewide noxious weed effective July 1, 2000. It is the first federally listed crop to be declared a noxious weed.

   While sericea lespedeza remains a relatively important forage crop in several southeastern states, it has become an invasive weed in tall grass and high plains prairie lands. Sericea aggressively competes with native prairie plants, and can result in a substantial reduction of native grasses and broadleaf plants. Researchers at Emporia State University (Emporia, Kansas) found that the number of grass and forb species in severely infested fields in east-central Kansas declined by 66% and 74% respectively. In a Kansas State University study, native grass production was reduced by as much as 80% when compared to non- infested areas. In addition, sericea lespedeza develops high tannin levels under the low rainfall conditions that exist in Kansas and becomes unpalatable to cattle as it matures. EPA has authorized under FIFRA section 18 the use of fluroxypyr on pastures and rangeland for control of sericea lespedeza in Kansas. After having reviewed the submission, EPA concurs that emergency conditions exist for this State.

   As part of its assessment of this emergency exemption, EPA assessed the potential risks presented by residues of fluroxypyr in or on grass forage and hay and their associated commodities. In doing so, EPA considered the safety standard in FFDCA section 408(b)(2), and EPA decided that the necessary tolerances under FFDCA section 408(l)(6) would be consistent with the safety standard and with FIFRA section 18. Consistent with the need to move quickly on the emergency exemption in order to address an urgent non-routine situation and to ensure that the resulting food is safe and lawful, EPA is issuing these tolerances without notice and opportunity for public comment as provided in section 408(l)(6). Although these tolerances will expire and are revoked on June 30, 2003, under FFDCA section 408(l)(5), residues of the pesticide not in excess of the amounts specified in the tolerance remaining in or on grass forage and hay and their associated commodities after that date will not be unlawful, provided the pesticide is applied in a manner that was lawful under FIFRA, and the residues do not exceed a level that was authorized by these tolerances at the time of that application. EPA will take action to revoke these tolerances earlier if any experience with, scientific data on, or other relevant information on this pesticide indicate that the residues are not safe.

   Because these tolerances is being approved under emergency conditions, EPA has not made any decisions about whether fluroxypyr meets EPA's registration requirements for use on pastures and rangeland or whether permanent tolerances for this use would be appropriate. Under these circumstances, EPA does not believe that these tolerances serve as a basis for registration of fluroxypyr by a State for special local needs under FIFRA section 24(c). Nor do these tolerances serve as the basis for any State other than Kansas to use this pesticide on this crop under section 18 of FIFRA without following all provisions of EPA's regulations implementing section 18 as identified in 40 CFR part 166. For additional information regarding the emergency exemption for fluroxypyr, contact the Agency's Registration Division at the address provided under FOR FURTHER INFORMATION CONTACT.

4. Aggregate Risk Assessment and Determination of Safety

   EPA performs a number of analyses to determine the risks from aggregate exposure to pesticide residues. For further discussion of the regulatory requirements of section 408 and a complete description of the risk assessment process, see the final rule on Bifenthrin Pesticide Tolerances (62 FR 62961, November 26, 1997) (FRL-5754-7).

   Consistent with section 408(b)(2)(D), EPA has reviewed the available scientific data and other relevant information in support of this action. EPA has sufficient data to assess the hazards of fluroxypyr and to make a determination on aggregate exposure, consistent with section 408(b)(2), for time-limited tolerances for combined residues of fluroxypyr 1-methylheptyl ester and its metabolite fluroxypyr, free and conjugated, all expressed as fluroxypyr, in or on grass, forage at 120 ppm, grass, hay at 160 ppm, and modifying the permanent tolerances for milk from 0.1 ppm to 0.30 ppm and for

   [[Page 47966]]

   kidney (cattle, goat, hog, horse, and sheep) from 0.5 ppm to 1.5 ppm. EPA's assessment of the dietary exposures and risks associated with establishing the tolerance follows.

   1. Toxicological Endpoints

      The dose at which no adverse effects are observed (the NOAEL) from the toxicology study identified as appropriate for use in risk assessment is used to estimate the toxicological endpoint. However, the lowest dose at which adverse effects of concern are identified (the LOAEL) is sometimes used for risk assessment if no NOAEL was achieved in the toxicology study selected. An uncertainty factor (UF) is applied to reflect uncertainties inherent in the extrapolation from laboratory animal data to humans and in the variations in sensitivity among members of the human population as well as other unknowns. An UF of 100 is routinely used, 10X to account for interspecies differences and 10X for intraspecies differences.

      For dietary risk assessment (other than cancer) the Agency uses the UF to calculate an acute or chronic reference dose (acute RfD or chronic RfD) where the RfD is equal to the NOAEL divided by the appropriate UF (RfD = NOAEL/UF). Where an additional safety factor is retained due to concerns unique to the FQPA, this additional factor is applied to the RfD by dividing the RfD by such additional factor. The acute or chronic population adjusted dose (aPAD or cPAD) is a modification of the RfD to accommodate this type of FQPA safety factor.

      For non-dietary risk assessments (other than cancer) the UF is used to determine the level of concern (LOC). For example, when 100 is the appropriate UF (10X to account for interspecies differences and 10X for intraspecies differences) the LOC is 100. To estimate risk, a ratio of the NOAEL to exposures (margin of exposure (MOE) = NOAEL/exposure) is calculated and compared to the LOC.

      The linear default risk methodology (Q*) is the primary method currently used by the Agency to quantify carcinogenic risk. The Q* approach assumes that any amount of exposure will lead to some degree of cancer risk. A Q* is calculated and used to estimate risk which represents a probability of occurrence of additional cancer cases (e.g., risk is expressed as 1 x 10-6or one in a million). Under certain specific circumstances, MOE calculations will be used for the carcinogenic risk assessment. In this non-linear approach, a ``point of departure'' is identified below which carcinogenic effects are not expected. The point of departure is typically a NOAEL based on an endpoint related to cancer effects though it may be a different value derived from the dose response curve. To estimate risk, a ratio of the point of departure to exposure (MOE cancer= point of departure/exposures) is calculated. A summary of the toxicological endpoints for fluroxypyr used for human risk assessment is shown in the following Table 1:

      Table 1. -- Summary of Toxicological Dose and Endpoints for Fluroxypyr for Use in Human Risk Assessment

      Dose Used in Risk FQPA SF and Endpoint/ Study and Toxicological Exposure Scenario

      Assessment, UF LOC for Risk Assessment

      Effects

      Acute dietary females 13-50 years of Developmental

      FQPA SF = 3x

      Developmental rabbit age

      NOAEL = 100 mg/kg/day.. aPAD = acute RfD....... Developmental LOAEL = UF = 100............... FQPA SF = 0.33 mg/kg/ 250 mg/kg/day, based Acute RfD = 1.0 mg/kg/ day.

      on increased day.

      postimplantation loss.

      Acute dietary general population

      A dose and endpoint were not selected for this population group because including infants and children

      there were no effects observed in oral toxicology studies including maternal toxicity in the developmental toxicity studies in rats and rabbits that are attributable to a single exposure (dose). A risk assessment is not required for this population subgroup.

      Chronic dietary all populations

      NOAEL = 50 mg/kg/day FQPA SF = 1X

      28-day dog range- UF = 100............... cPAD = cRfD =.......... finding feeding study Chronic RfD = 0.50 mg/ FQPA SF = 0.50 mg/kg/ LOAEL = 150 mg/kg/day kg/day.

      day.

      based on histopathological lesions in the kidneys, decreased testes weights, and increased adrenal weights in both sexes.

      Incidental, Oral:

      Since there are no residential uses, toxicology endpoints were not Short-term (1-7 days),...............

      proposed/selected for any exposure scenarios. Intermediate-term (1 week - several months),. Long-term (several months - lifetime) (Residential)........................

      Dermal1and Inhalation2,

      Oral NOAEL= 100 mg/kg/ LOC for MOE = 100

      Developmental rabbit Short-term (1-7days)................. day

      (Occupational)......... study (Occupational/Residential)...........

      Developmental LOAEL = 250 mg/kg/day, based on increased postimplantation loss.

      Dermal1and Inhalation 2:

      Oral NOAEL= 100 mg/kg/ LOC for MOE = 100

      Developmental rabbit Intermediate-term (1 week-several day

      (Occupational)......... study months).

      Developmental LOAEL = (Occupational/Residential)...........

      250 mg/kg/day, based on increased postimplantation loss.

      1Since an oral NOAEL was selected, a dermal absorption factor of 100% (default value) should be used in route- to-route extrapolation. 2Since an oral NOAEL was selected, an inhalation absorption factor of 100% (default value) should be used in route-to-route extrapolation.

      [[Page 47967]]

   2. Exposure Assessment

      1. Dietary exposure from food and feed uses. Tolerances have been established (40 CFR 180.535) for the combined residues of fluroxypyr, in or on a variety of raw agricultural commodities, including meat, milk, poultry and eggs. Risk assessments were conducted by EPA to assess dietary exposures from fluroxypyr in food as follows:

         i. Acute exposure. Acute dietary risk assessments are performed for a food-use pesticide if a toxicological study has indicated the possibility of an effect of concern occurring as a result of a one day or single exposure. The Dietary Exposure Evaluation Model (DEEM) analysis evaluated the individual food consumption as reported by respondents in the USDA 1989-1992 nationwide Continuing Surveys of Food Intake by Individuals (CSFII) and accumulated exposure to the chemical for each commodity. The following assumptions were made for the acute exposure assessments: For the acute analysis, published and proposed tolerances level residues were used. Default concentration factors and 100% CT was assumed for all commodities.

         ii. Chronic exposure. In conducting this chronic dietary risk assessment the DEEM analysis evaluated the individual food consumption as reported by respondents in the USDA 1989-1992 nationwide CSFII and accumulated exposure to the chemical for each commodity. The following assumptions were made for the chronic exposure assessments: For the chronic analysis, published and proposed tolerances level residues were used. Default concentration factors and 100% CT was assumed for all commodities.

         iii. Cancer. The Agency has classified fluroxypyr as ``not likely'' to be a human carcinogen, therefore this risk assessment is not required.

      2. Dietary exposure from drinking water. The Agency lacks sufficient monitoring exposure data to complete a comprehensive dietary exposure analysis and risk assessment for fluroxypyr in drinking water. Because the Agency does not have comprehensive monitoring data, drinking water concentration estimates are made by reliance on simulation or modeling taking into account data on the physical characteristics of fluroxypyr.

         The Agency uses the Generic Estimated Environmental Concentration (GENEEC) or the Pesticide Root Zone/Exposure Analysis Modeling System (PRZM/EXAMS) to estimate pesticide concentrations in surface water and Screening Concentrations in Ground Water (SCI-GROW), which predicts pesticide concentrations in ground water. In general, EPA will use GENEEC (a tier 1 model) before using PRZM/EXAMS (a tier 2 model) for a screening-level assessment for surface water. The GENEEC model is a subset of the PRZM/EXAMS model that uses a specific high-end runoff scenario for pesticides. GENEEC incorporates a farm pond scenario, while PRZM/EXAMS incorporate an index reservoir environment in place of the previous pond scenario. The PRZM/EXAMS model includes a percent crop area factor as an adjustment to account for the maximum percent crop coverage within a watershed or drainage basin.

         None of these models include consideration of the impact processing (mixing, dilution, or treatment) of raw water for distribution as drinking water would likely have on the removal of pesticides from the source water. The primary use of these models by the Agency at this stage is to provide a coarse screen for sorting out pesticides for which it is highly unlikely that drinking water concentrations would ever exceed human health levels of concern.

         Since the models used are considered to be screening tools in the risk assessment process, the Agency does not use estimated environmental concentrations (EECs) from these models to quantify drinking water exposure and risk as a %RfD or %PAD. Instead drinking water levels of comparison (DWLOCs) are calculated and used as a point of comparison against the model estimates of a pesticide's concentration in water. DWLOCs are theoretical upper limits on a pesticide's concentration in drinking water in light of total aggregate exposure to a pesticide in food, and from residential uses. Since DWLOCs address total aggregate exposure to fluroxypyr they are further discussed in the aggregate risk sections below.

         Based on the GENEEC and SCI-GROW models the EECs of fluroxypyr for acute exposures are estimated to be 7.6 parts per billion (ppb) for surface water and 0.017 ppb for ground water. The EECs for chronic exposures are estimated to be 1.6 ppb for surface water and 0.017 ppb for ground water.

      3. From non-dietary exposure. The term ``residential exposure'' is used in this document to refer to non-occupational, non-dietary exposure (e.g., for lawn and garden pest control, indoor pest control, termiticides, and flea and tick control on pets).

         Fluroxypyr is not registered for use on any sites that would result in residential exposure.

      4. Cumulative exposure to substances with a common mechanism of toxicity. Section 408(b)(2)(D)(v) requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider ``available information'' aggregate exposure concerning the cumulative effects of a particular pesticide's residues and ``other substances that have a common mechanism of toxicity.''

         EPA does not have, at this time, available data to determine whether fluroxypyr has a common mechanism of toxicity with other substances or how to include this pesticide in a cumulative risk assessment. Unlike other pesticides for which EPA has followed a cumulative risk approach based on a common mechanism of toxicity, fluroxypyr does not appear to produce a toxic metabolite produced by other substances. For the purposes of this tolerance action, therefore, EPA has not assumed that fluroxypyr has a common mechanism of toxicity with other substances. For information regarding EPA's efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the final rule for Bifenthrin Pesticide Tolerances (62 FR 62961, November 26, 1997).

   3. Safety Factor for Infants and Children

      1. In general. FFDCA section 408 provides that EPA shall apply an additional tenfold margin of safety for infants and children in the case of threshold effects to account for prenatal and postnatal toxicity and the completeness of the data base on toxicity and exposure unless EPA determines that a different margin of safety will be safe for infants and children. Margins of safety are incorporated into EPA risk assessments either directly through use of a margin of exposure (MOE) analysis or through using uncertainty (safety) factors in calculating a dose level that poses no appreciable risk to humans.

      2. Developmental toxicity studies. In the developmental study in rats, the maternal (systemic) NOAEL was 125 milligrams/kilograms/day (mg/kg/day), based on clinical signs at the LOAEL of 250 mg/kg/day. The developmental (fetal) NOAEL was 250 mg/kg/day, based on reduced ossification at the LOAEL of 500 mg/kg/day.

         In the developmental toxicity study in rabbits, the maternal (systemic) NOAEL was 250 mg/kg/day, based on maternal deaths at the LOAEL of 400 mg/kg/day.

         [[Page 47968]]

         The developmental (pup) NOAEL was 125 mg/kg/day, based on increased postimplantation loss at the LOAEL of 250 mg/kg/day.

      3. Reproductive toxicity study. In the 2-generation reproductive toxicity study in rats, the maternal (systemic) NOAEL was 100 mg/kg/ day, based on increased kidney weights and kidney histopathology at the LOAEL of 500 mg/kg/day. The developmental (pup) NOAEL was 500 mg/kg/ day, based on decreased body weight at the LOAEL of 1,000 mg/kg/day. The reproductive NOAEL was 1,000 mg/kg/day (HDT).

      4. Prenatal and postnatal sensitivity. The toxicological data base for evaluating prenatal and postnatal toxicity for fluroxypyr is complete with respect to current data requirements. Based on the results of the rabbit developmental toxicity study for fluroxypyr there does appear to be an extra sensitivity for prenatal effects.

      5. Conclusion. Based on the above, EPA concludes that reliable data support use of a 300 fold margin of exposure/uncertainty factor, rather than the standard 1,000 fold margin/factor, to protect infants and children.

   4. Aggregate Risks and Determination of Safety

      To estimate total aggregate exposure to a pesticide from food, drinking water, and residential uses, the Agency calculates DWLOCs which are used as a point of comparison against the model estimates of a pesticide's concentration in water EECs. DWLOC values are not regulatory standards for drinking water. DWLOCs are theoretical upper limits on a pesticide's concentration in drinking water in light of total aggregate exposure to a pesticide in food and residential uses. In calculating a DWLOC, the Agency determines how much of the acceptable exposure (i.e., the PAD) is available for exposure through drinking water e.g., allowable chronic water exposure (mg/kg/day) = cPAD - (average food + chronic non-dietary, non-occupational exposure). This allowable exposure through drinking water is used to calculate a DWLOC.

      A DWLOC will vary depending on the toxic endpoint, drinking water consumption, and body weights. Default body weights and consumption values as used by the US EPA Office of Water are used to calculate DWLOCs: 2Liter/70 kilogram (adult male), 2L/60 kg (adult female), and 1L/10 kg (child). Default body weights and drinking water consumption values vary on an individual basis. This variation will be taken into account in more refined screening level and quantitative drinking water exposure assessments. Different populations will have different DWLOCs. Generally, a DWLOC is calculated for each type of risk assessment used: acute, short-term, intermediate-term, chronic, and cancer.

      When EECs for surface water and ground water are less than the calculated DWLOCs, OPP concludes with reasonable certainty that exposures to fluroxypyr in drinking water (when considered along with other sources of exposure for which OPP has reliable data) would not result in unacceptable levels of aggregate human health risk at this time. Because OPP considers the aggregate risk resulting from multiple exposure pathways associated with a pesticide's uses, levels of comparison in drinking water may vary as those uses change. If new uses are added in the future, OPP will reassess the potential impacts of fluroxypyr on drinking water as a part of the aggregate risk assessment process.

      1. Acute risk. Using the exposure assumptions discussed in this unit for acute exposure, the acute dietary exposure from food to fluroxypyr will occupy 1.5% of the aPAD for females 13-50 years old, the only population sub-group of concern. A dose and endpoint were not selected for the U.S. population, including infants and children because there were no effects observed in oral toxicology studies including maternal toxicity in the developmental toxicity studies in rats and rabbits that are attributable to a single exposure (dose). Therefore, a risk assessment is not required for this population subgroup.

         In addition, despite the potential for acute dietary exposure to fluroxypyr in drinking water, after calculating DWLOCs and comparing them to conservative model estimated environmental concentrations of fluroxypyr in surface and ground water, EPA does not expect the aggregate exposure to exceed 100% of the aPAD, as shown in the following Table 2:

         Table 2. -- Aggregate Risk Assessment for Acute Exposure to Fluroxypyr

         Surface Ground Population Subgroup

         aPAD (mg/ %aPAD Water EEC Water EEC Acute DWLOC kg)

         (Food) (ppb)

         (ppb)

         (ppb)

         Females (13-50 years old)

         0.33

         1.5

         7.6

         0.017

         9,700

      2. Chronic risk. Using the exposure assumptions described in this unit for chronic exposure, EPA has concluded that exposure to fluroxypyr from food will utilize 0.6% of the cPAD for the U.S. population, 0.9% of the cPAD for all infants 01-23092Filed9-14-01; 8:45am] BILLING CODE 6560-50-S