Pesticides; tolerances in food, animal feeds, and raw agricultural commodities: Penoxsulam,
[Federal Register: September 24, 2004 (Volume 69, Number 185)]
[Rules and Regulations]
[Page 57188-57197]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24se04-11]
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 180
[OPP-2004-0286; FRL-7678-6]
Penoxsulam, 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4] triazolo[1,5-c]pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide; Pesticide Tolerance
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: This regulation establishes a tolerance for residues of penoxsulam 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5- c]pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide in or on rice,grain and rice, straw. Dow AgroSciences LLC requested this tolerance under the Federal Food, Drug, and Cosmetic Act (FFDCA), as amended by the Food Quality Protection Act of 1996 (FQPA).
DATES: This regulation is effective September 24, 2004. Objections and requests for hearings must be received on or before November 23, 2004.
ADDRESSES: To submit a written objection or hearing request follow the detailed instructions as provided in Unit VI. of the SUPPLEMENTARY INFORMATION. EPA has established a docket for this action under Docket identification (ID) number OPP-2004-0286. All documents in the docket are listed in the EDOCKET index at http://www.epa.gov/edocket. Although
listed in the index, some information is not publicly available, i.e., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the Internet and will be publicly available only in hard copy form. Publicly available docket materials are available either electronically in EDOCKET or in hard copy at the Public Information and Records Integrity Branch (PIRIB), Rm. 119, Crystal Mall 2, 1801 S. Bell St., Arlington, VA. This docket facility is open from 8:30 a.m. to 4 p.m., Monday through Friday, excluding legal holidays. The docket telephone number is (703) 305-5805.
FOR FURTHER INFORMATION CONTACT: Joanne I. Miller, Registration Division (7505C), Office of Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania Ave., NW.,Washington, DC 20460- 0001; telephone number: (703) 305-6224; e-mail address: miller.joanne]@epa.gov.
SUPPLEMENTARY INFORMATION:
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General Information
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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 entities may include, but are not limited to:
Crop production (NAICS 111), e.g., agricultural workers; greenhouse, nursery, and floriculture workers; farmers.
Animal production (NAICS 112), e.g., cattle ranchers and farmers, dairy cattle farmers, livestock farmers.
Food manufacturing (NAICS 311), e.g., agricultural workers; farmers; greenhouse, nursery, and floriculture workers; ranchers; pesticide applicators.
Pesticide manufacturing (NAICS 32532), e.g., agricultural workers; commercial applicators; farmers; greenhouse, nursery, and floriculture workers; residential users.
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 this unit could also be affected. The North American Industrial Classification System (NAICS) codes have been provided to assist you and others in determining whether this action might apply to certain entities. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed under FOR FURTHER INFORMATION CONTACT.
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How Can I Access Electronic Copies of this Document and Other Related Information?
In addition to using EDOCKET (http://www.epa.gov/edocket/), you may
access this Federal Register document electronically through the EPA Internet under the ``Federal Register'' listings at http://www.epa.gov/fedrgstr/. A frequently updated electronic version of 40 CFR part 180
is available at E-CFR Beta Site Two at http://www.gpoaccess.gov/ecfr/.
To access the OPPTS Harmonized Guidelines referenced in this document, go directly to the guidelines at http://www.epa.gpo/opptsfrs/home/guidelin.htm/ .
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Background and Statutory Findings
In the Federal Register of August 6, 2003 (68 FR 46609) (FRL-7320- 4), EPA issued a notice pursuant to section 408(d)(3) of FFDCA, 21 U.S.C. 346a(d)(3), announcing the filing of a pesticide petition (PP 3F6542) by Dow AgroSciences LLC, 9330 Zionsville Road, Indianapolis, IN 46268-1054. The petition requested that 40 CFR part 180 be amended by establishing a tolerance for residues of the herbicide penoxsulam, 2- (2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2- yl)-6-(trifluoromethyl)benzenesulfonamide, in or on rice, grain at 0.01 parts per million (ppm), rice, straw at 0.5 ppm, rice, hulls at 0.01 ppm, rice, bran at 0.01 ppm, and rice, polished rice at 0.01 ppm. That notice included a summary of the petition prepared by Dow AgroSciences LLC, the registrant. There were no comments received in response to the notice of filing. The tolerance for rice grain was increased to 0.02 ppm to reflect the submitted field residue data. Residues of penoxsulam do not concentrate in the processed commodities, rice hull, bran, or polished rice, therefore any residues of penoxsulam on these commodities will be covered by the tolerance on rice, grain.
Section 408(b)(2)(A)(i) of 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) of FFDCA 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) of FFDCA 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....''
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 of FFDCA 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).
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Aggregate Risk Assessment and Determination of Safety
Consistent with section 408(b)(2)(D) of FFDCA, 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 and to make a determination on aggregate exposure, consistent with section 408(b)(2) of FFDCA, for a tolerance for residues of penoxsulam on rice, grain at 0.02 ppm and rice, straw at 0.5 ppm. No tolerances were necessary for the rice process commodities, rice hulls, bran, or polished rice, because residues will not exceed the established tolerance in rice, grain. EPA's assessment of exposures and risks associated with establishing the tolerance follows.
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Toxicological Profile
EPA has evaluated the available toxicity data and considered its validity, completeness, and reliability as well as the relationship of the results of the studies to human risk. EPA has also considered available information concerning the variability of the sensitivities of major identifiable subgroups of consumers, including infants and children. The nature of the toxic effects caused by penoxsulam are discussed in Table 1 of this unit as well as the no-observed-adverse- effect-level (NOAEL) and the lowest-observed-adverse-effect-level (LOAEL) from the toxicity studies reviewed.
Table 1.--Subchronic, Chronic, and Other Toxicity
Guideline No.
Study Type
Results
870.3100
90-day oral toxicity-rat NOAEL = Male (M): 50/Female (F): 250 milligrams/kilogram/day (mg/kg/day) LOAEL = M: 250 mg/kg/day based on decease body weight/body weight gain (bw/bwg), decease food consumption, and decease RBC parameters and F:500 mg/kg/day based on increase mineralization and hyperplasia of the kidney pelvic epithelium
870.3100
90-day oral toxicity-mouse NOAEL= M:1027 highest dose tested (HDT)/ F:1029 HDT mg/kg/day LOAEL= M: Not determined, >1027 HDT/F:>1029 HDT mg/kg/day
870.3150
90-day oral toxicity- dog NOAEL = M: 17.8/F: 19.9 mg/kg/day LOAEL = M:49.4/F:57.1 mg/kg/day based on histopathologic changes in kidney
870.3200
28-day dermal Test
NOAEL = M:1,000/F:1,000 mg/kg/day Material: technical
LOAEL = M:>1,000 HDT/F: >1,000 HDT
870.3200
Test Material: 21.9%
NOAEL= M:500/F:1,000 mg/kg/day formulated GF-443
LOAEL = M:1,000 mg/kg/day based on very material, rat
slight hyperplasia at test site and F:>1,000 HDT mg/kg/day
870.3700
Prenatal developmental-rat Maternal NOAEL = 500 mg/kg/day Maternal LOAEL = 1,000 mg/kg/day based on decease bwg, decease food consumption, and decease kidney weights Developmental NOAEL = 1,000 HDT mg/kg/day Developmental LOAEL = >1,000 HDT
870.3700
Prenatal developmental- Maternal NOAEL = 25 mg/kg/day rabbit
Maternal LOAEL = 75 mg/kg/day based on death, clinical signs, decease bwg, and decease food consumption Developmental NOAEL = 75 mg/kg/day Developmental LOAEL = >75 HDT
870.3800
2-Generation Reproduction Parental/Systemic NOAEL = M:100/F:30 mg/kg/ and fertility effects in day rats
Parental/Systemic LOAEL = M:300 mg/kg/day based on decease bw of F1 males Parental/Systemic LOAEL = F:100 mg/kg/day based on kidney lesions Reproductive/Offspring NOAEL = 30 mg/kg/day Reproductive/Offspring LOAEL = 100 mg/kg/ day based on delayed preputial separation
870.4100
Chronic toxicity-dogs NOAEL = M:14.7/F:44.8 HDT mg/kg/day LOAEL = M:46.2 mg/kg/day based on slight multifocal hyperplasia in the kidney epithelium and F:> 44.8 HDT
870.4100
Chronic toxicity- rats NOAEL = M:50/F:50 mg/kg/day LOAEL = M:250 mg/kg/day based on decease bw/ bwg, decease RBC parameters, increase BUN, increase urine volume, decease urine specific gravity, increase kidney wt., increase crystals/calculi in kidney and urinary bladder, hyperplasia of kidney pelvis epithelium and urinary bladder mucosa, and increase severity of chronic glomerulonephropathy
870.4200
Carcinogenicity- rats LOAEL = F:250 mg/kg/day based on decease bw/ bwg, increase urine volume, increase crystals/calculi in urinary bladder, hyperplasia of kidney pelvis epithelium and urinary bladder mucosa
870.4200
Carcinogenicity
Evidence of carcinogenicity in male rats based on possibly treatment related increase incidence of Large Granular Lymphocyte (LGL) Leukemia at 5, 50, & 250 mg/kg/day. Also increase severity at 250 mg/kg/day. Female rats - negative for carcinogenicity, but dosing was only marginally adequate.
870.4300
Carcinogenicity-mice
NOAEL = M:>375 HDT/F:>750 HDT mg/kg/day LOAEL = M:>375 HDT/F:>750 HDT In males, negative for carcinogenicity at doses tested. Dosing inadequate. In females, negative for carcinogenicity at the doses tested. Dosing adequate (750 mg/ kg/day is sufficiently close to limit dose of 1,000 mg/kg/day).
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870.5100
MUTA-Reverse Gene mutation Negative with and without rat S-9 - S.typhimurium/E. coli activation
870.5300
Muta-forward gene mutation Negative with and without rat S-9 (CHO Cells/HGPRT locus) activation
870.5375
Muta-in vitro Mammalian Negative with and without rat S-9 Cytogenetics (Chromosomal activiation aberrations in primary rat lymphocytes)
870.5395
Muta-in vivo Micronucleus, Negative at oral doses (once per day on two Mice (bone marrow cells) consecutive days) of up to 2,000 mg/kg
870.6200
Acute neurotoxicity
NOAEL = M/F 2,000 HDT mg/kg/day screening battery
LOAEL = M/F >2,000 HDT
870.6200
Chronic neurotoxicity NOAEL = M/F 250 mg/kg/day screening battery
LOAEL = M/F >250 (HDT) mg/kg/day
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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 level of concern (LOC). 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.
Three other types of safety or uncertainty factors may be used: ``Traditional uncertainty factors;'' the ``special FQPA safety factor;'' and the ``default FQPA safety factor.'' By the term ``traditional uncertainty factor,'' EPA is referring to those additional uncertainty factors used prior to FQPA passage to account for database deficiencies. These traditional uncertainty factors have been incorporated by the FQPA into the additional safety factor for the protection of infants and children. The term ``special FQPA safety factor'' refers to those safety factors that are deemed necessary for the protection of infants and children primarily as a result of the FQPA. The ``default FQPA safety factor'' is the additional 10X safety factor that is mandated by the statute unless it is decided that there are reliable data to choose a different additional factor (potentially a traditional uncertainty factor or a special FQPA safety factor).
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 an UF of 100 to account for interspecies and intraspecies differences and any traditional uncertainty factors deemed appropriate (RfD = NOAEL/UF). Where a special FQPA safety factor or the default FQPA safety factor is used, 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 safety factor.
For non-dietary risk assessments (other than cancer) the UF is used to determine the 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). An example of how such a probability risk is expressed would be to describe the risk as one in one hundred thousand (1 X 10-\5\), one in a million (1 X 10-\6\), or one in ten million (1 X 10\7\). 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 (MOEcancer= point of departure/exposures) is calculated.
A summary of the toxicological endpoints for penoxsulam used for human risk assessment is shown in Table 2 of this unit:
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Table 2.--Summary of Toxicological Dose and Endpoints for Penoxsulam for Use in Human Risk Assessment
Special FQPA SF* and Exposure Scenario
Dose Used in Risk Level of Concern for Study and Toxicological Assessment, UF
Risk Assessment
Effects
Acute Dietary (all populations)
None
Not applicable
No toxicological UF = N/A...............
endpoint attributable to a single exposure was identified in the available toxicology studies on penoxsulam.
Chronic Dietary (all populations) NOAEL= 14.7 mg/kg/day Special FQPA SF = 1x 1-Year Chronic Feeding UF = 100............... cPAD = chronic RfD..... Study in Dogs. Chronic RfD = 0.147 mg/ Special FQPA SF = 0.147 LOAEL = 46.2 mg/kg/day kg/day.
mg/kg/day.
based on multifocal hyperplasia of the pelvic epithelium of the kidney.
Incidental Oral Short-Term (1 - 30 NOAEL = 17.8 mg/kg/day Residential LOC for MOE 13-Week Feeding Study days)
= 100
in Dogs. Occupational = NA...... LOAEL = 49.4 mg/kg/day based on histopathologic changes in kidneys
Incidental Oral Intermediate-Term (1 - NOAEL = 17.8 mg/kg/day Residential LOC for MOE 13-Week Feeding Study 6 months)
= 100
in Dogs. Occupational = NA...... LOAEL = 49.4 mg/kg/day based on histopathologic changes in kidneys.
Dermal Short-Term (1 - 30 days)
None
Not applicable
No dermal, systemic, neuro or developmental toxicity concerns.
Dermal Intermediate-Term (1 - 6
Oral study
Residential LOC for MOE 13-Week Feeding Study months)
NOAEL= 17.8 mg/kg/day = 100
in Dogs. (dermal absorption Occupational LOC for LOAEL = 49.4 mg/kg/day rate = 50%).
MOE = 100.
based on histopathologic changes in kidneys.
Dermal Long-Term > 6 months)
Oral study
Residential LOC for MOE 1-Year Chronic Feeding NOAEL= 14.7 mg/kg/day = 100
Study in Dogs. (dermal absorption Occupational LOC for LOAEL = 46.2 mg/kg/day rate = 50%).
MOE = 100.
based on multifocal hyperplasia of the pelvic epithelium of the kidney.
Inhalation Short-Term (1 - 30 days) Oral study
Residential LOC for MOE 13-Week Feeding Study NOAEL= 17.8 mg/kg/day = 100
in Dogs. (inhalation absorption Occupational LOC for LOAEL = 49.4 mg/kg/day rate = 100%).
MOE = 100.
based on histopathologic changes in kidneys.
Inhalation Intermediate-Term (1 - 6 Oral study
Residential LOC for MOE 13-Week Feeding Study months)
NOAEL= 17.8 mg/kg/day = 100
in Dogs. (inhalation absorption Occupational LOC for LOAEL = 49.4 mg/kg/day rate = 100%).
MOE = 100.
based on histopathologic changes in kidneys.
Inhalation Long-Term (> 6 months) Oral study
Residential LOC for MOE 1-Year Chronic Feeding NOAEL= 14.7 mg/kg/day = 100
Study in Dogs. (inhalation absorption Occupational LOC for LOAEL = 46.2 mg/kg/day rate = 100%).
MOE = 100.
based on multifocal hyperplasia of the pelvic epithelium of the kidney.
Cancer (oral, dermal, inhalation)
Suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential
UF = uncertainty factor, FQPA SF = Special FQPA safety factor, NOAEL = no observed adverse effect level, LOAEL = lowest observed adverse effect level, PAD = population adjusted dose (a = acute, c = chronic) RfD = reference dose, MOE = margin of exposure, LOC = level of concern, N/A = Not Applicable.
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Exposure Assessment
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Dietary exposure from food and feed uses. Tolerances have been established (40 CFR 180.605) for the residues of penoxsulam, in or on a variety of raw agricultural commodities. Tolerances are established in/ on rice, grain at 0.02 ppm and rice, straw at 0.5 ppm. Risk assessments were conducted by EPA to assess dietary exposures from penoxsulam 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.
EPA did not identify a treatment-related effect observed in any of the available toxicity studies on penoxsulam that could be considered to have resulted from a single dose of the test material.
ii. Chronic exposure. In conducting the chronic dietary risk assessment EPA used the Lifeline\TM\ Model Version 2.0, which uses food consumption data as reported by respondents in the USDA 1994-1996 and 1998 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 chronic exposure assessments: The chronic dietary analysis for penoxsulam was conducted using tolerance levels and 100% Crop Treated (CT) for the use on rice.
iii. Cancer. The Agency has classified penoxsulam as Suggestive Evidence of Carcinogenicity, But not sufficient to assess human carcinogenic potential and, therefore, quantification of human cancer risk is not required. The weight-
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of-the-evidence for this classification is as follows:
a. Evidence of carcinogenicity (mononuclear cell leukemia (MNCL)) was seen in one sex (males) of one species (rat).
b. There was an increased incidence of MNCL at all dose levels with all incidences exceeding the laboratory historical control, however, the dose-response was flat over a wide range of doses.
c. Although MNCL is recognized as a common neoplasm in Fischer rats, the mechanism of producing MNCL is not completely understood. Therefore, the significance of MNCL and its biological relevance for human cancer risk remains uncertain and cannot be discounted.
d. There is no mutagenicity concern for penoxsulam.
e. SAR data are negative for MNCL.
Note: Although dosing in the male mice was not considered to be adequate, the Agency concluded that an additional mouse carcinogenicity study was not required. This was based on the following:
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No treatment-related effects were seen up to the limit dose of a 1,000 mg/kg/day in a subchronic mouse study;
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No hyperplasia was seen in the mouse carcinogenicity study at 350 mg/kg/day in males and 750 mg/kg/day in females;
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No structural alerts were seen with the SAR data;
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Rat data indicate saturation of absorption at 250 mg/kg/day; and
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No mutagenic activity. Based on these data, the CARC determined that a repeat of the male mouse cancer study would have no impact on the regulation of penoxsulam.
iv. Anticipated residue and percent crop treated (PCT) information. For this analysis the tolerance levels and 100% CT for rice commodities were used.
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Dietary exposure from drinking water. The Agency lacks sufficient monitoring exposure data to complete a comprehensive dietary exposure analysis and risk assessment for penoxsulam 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 penoxsulam.
The standard models used by EPA in assessing potential high end pesticide levels in surface water are not designed to address the agricultural practices involved in rice farming. EPA has recently developed a Tier I Aquatic Exposure Assessment method of estimating screening level concentrations in surface water to support regulatory decisions for pesticides used in rice agriculture that require ecological and human health risk assessments.
Under this method estimated environmental concentrations (EEC's) and estimated drinking water concentrations (EDWCs) for the use of pesticides in rice paddies are estimated by applying the total annual application to the paddy and partitioning the pesticide between the water and the paddy sediment according to a linear or Kd partitioning model. The EEC/EDWC ([mu]g. L-\1\) represents the dissolved concentration occurring in the water column and the concentration in water released from the paddy. Movement of pesticide on suspended sediment is not considered. The equation to use for this calculation is:
EEC = 10\9\ MT/VT+ msedKd where MTis the total mass of pesticide in kg applied per ha of paddy, VTis 1.067 x10\6\ L ha-\1\ which is the volume of water in a paddy 4 inches (10.16 cm) deep, and includes the pore space in a 1 cm sediment interaction zone. The mass of sediment, msed, is the amount found in the top 1 cm interaction zone and is 130,000 kg ha-\1\ when the sediment bulk density was assumed to be 1.3 kg L-\1\, a standard assumption for the bulk density of surface horizons of mineral soils (Brady, Nyle C. 1984. The Nature and Properties of Soils, Ninth Edition. Macmillan Publishing Company, New York ; Hillel, Daniel. 1982. Introduction to Soil Physics. Academic Press. Orlando, Florida). The 10\9\ constant converts the units of mass from kg to [mu]g. For chemicals that have a valid Koc, the Kdcan be calculated using a sediment carbon content of 2% (Koc*0.02). An organic carbon content of 2% represents a typical value for a high clay soil that might be used to grow rice in the Mississippi Valley or Gulf Coast regions. Both Kdand Kocshould be estimated according to the methods recommended for other surface water models in EFED's Input Parameter Guidance (USEPA, 2002). References can be viewed on the EPA Pesticide Site at http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm .
This model is considered conservative, because the residues calculated by this method are screening estimates and as such are expected to exceed the true values found in the environment the great majority of the time. Based on preliminary assessment of rice monitoring data, predicted pesticide concentrations as derived above (assuming a 1 cm sediment interaction zone) exceed the observed peak pesticide concentrations. These EEC's are expected to exceed the concentrations measured in the paddy, because degradation processes and dilution with uncontaminated water outside the paddy is not considered. This calculation does not represent a concentration expected in drinking water, as it represents paddy discharge water. Rather, it represents an upper bound on the drinking water concentrations, and is therefore suitable for use in screening assessments. The concentrations found at drinking water facilities impacted by rice culture would be expected to be less than this value (in some cases much less), because of the aforementioned degradation processes, dilution by water from areas in the basin not in rice culture, and the fact that in most cases less than 100% of the rice paddies in a specific area will be treated with the pesticide.
Based on the methodology to estimate screening level concentrations of pesticides in rice and SCI-GROW models, the EECs of penoxsulam for acute and chronic exposures are estimated to be 45 parts per billion (ppb) for surface water and 5.86 ppb for combined residues of penoxsulam in ground water.
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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).
Penoxsulam is not registered for use on any sites that would result in residential exposure.
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Cumulative effects from substances with a common mechanism of toxicity. Section 408(b)(2)(D)(v) of FFDCA requires that, when considering whether to establish, modify, or revoke a tolerance, the Agency consider ``available information'' concerning the cumulative effects of a particular pesticide's residues and ``other substances that have a common mechanism of toxicity.''
Unlike other pesticides for which EPA has followed a cumulative risk approach based on a common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as to penoxsulam and any other substances and penoxsulam 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 penoxsulam 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 policy statements released by EPA's OPP concerning common mechanism determinations and procedures for cumulating effects
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from substances found to have a common mechanism on EPA's web site at http://www.epa.gov/pesticides/cumulative/.
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Safety Factor for Infants and Children
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In general. Section 408 of FFDCA 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 based on reliable data 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 MOE analysis or through using uncertainty (safety) factors in calculating a dose level that poses no appreciable risk to humans. In applying this provision, EPA either retains the default value of 10X when reliable data do not support the choice of a different factor, or, if reliable data are available, EPA uses a different additional safety factor value based on the use of traditional uncertainty factors and/or special FQPA safety factors, as appropriate.
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Prenatal and postnatal sensitivity. There is no quantitative or qualitative evidence of susceptibility in rats or rabbits following in utero exposures. No developmental toxicity was seen at the highest dose tested in either species. Following pre/post-natal exposure in the two- generation study, offspring toxicity was seen at the same dose that induced parental toxicity and was not more severe than maternal toxicity.
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Conclusion. There is a complete toxicity data base for penoxsulam and exposure data are complete or are estimated based on data that reasonably accounts for potential exposures. The uncertainty factor (UF) is 100 based on 10X for interspecies extrapolation and 10X for intraspecies variability. EPA determined that the 10X safety factor (SF) to protect infants and children should be removed based on the following:
i. There was no toxicologically significant evidence observed of neurotoxicity in either the acute or chronic neurotoxicity study.
ii. No definitive quantitative or qualitative susceptibility was observed in either of the developmental rat or rabbit studies.
iii. Significant dose-related effects in the two-generation reproduction study were limited to the delay in preputial separation. No other endpoints of reproductive toxicity or offspring growth and survival were affected by treatment.
iv. The chronic dietary food exposure assessment utilizes proposed tolerance level residues and 100% CT information for all commodities. By using these conservative assessments, actual and chronic exposures/ risks will not be underestimated.
v. The dietary drinking water assessment (Tier 1 estimates) utilizes values generated by model and associated modeling parameters which are designed to provide conservative, health protective, high-end estimates of water concentrations.
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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 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 + residential 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 EPA's Office of Water are used to calculate DWLOCs: 2 liter (L)/70 kg (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 the pesticide 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 residues of the pesticide in drinking water as a part of the aggregate risk assessment process.
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Acute risk. A quantitative acute exposure/risk assessment was not performed, because no treatment-related effect was identified in any of the available toxicity studies on penoxsulam that could be considered to have resulted from a single dose of penoxsulam. Penoxsulam is not expected to pose an acute risk.
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Chronic risk. Using the exposure assumptions described in this unit for chronic exposure, EPA has concluded that exposure to penoxsulam from food will utilize (ppb)
U.S. Population
0.147
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