Pesticides; tolerances in food, animal feeds, and raw agricultural commodities: ethyl,
[Federal Register: June 12, 2002 (Volume 67, Number 113)]
[Rules and Regulations]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
ENVIRONMENTAL PROTECTION AGENCY
Carfentrazone-ethyl; Pesticide Tolerances for Emergency Exemptions
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
SUMMARY: This regulation establishes time-limited tolerances for combined residues of carfentrazone-ethyl (ethyl-[alpha],2-dichloro-5-
[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl)- 4-fluorobenzenepropanoate) and carfentrazone-ethyl chloropropionic acid ([alpha] ,2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo- 1H-1,2,4-triazol-1-yl]-4-fluorobenzenepropanoic acid) in or on fruiting vegetables (except cucurbits) (crop group 8), tomato paste and tomato puree. This action is in response to EPA's granting of an emergency exemption under section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizing use of the pesticide on fruiting vegetables (except cucurbits) (crop group 8). This regulation establishes a maximum permissible level for residues of carfentrazone- ethyl in these food commodities. These tolerances will expire and are revoked on June 30, 2004. This document also reinstates the commodity ``soybean seed'' which was inadvertently omitted in a previous revision published in the Federal Register.
DATES: This regulation is effective June 12, 2002. Objections and requests for hearings, identified by docket ID number OPP-2002-0072, must be received on or before August 12, 2002.
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 ID number OPP-2002-0072 in the subject line on the first page of your response.
FOR FURTHER INFORMATION CONTACT: By mail: Barbara Madden, Registration Division (7505C), Office of Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460; telephone number: (703) 305-6463; e-mail address: Madden.Barbara@epa.gov.
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
Potentially Affected Entities
Crop production 112
Animal production 311
Food manufacturing 32532
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.
How Can I Get Additional Information, Including Copies of this Document and Other Related Documents?
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. To access the OPPTS Harmonized Guidelines referenced in this document, go directly to the guidelines at http://www.epa.gov/ opptsfrs/home/guidelin.htm.
In person. The Agency has established an official record for this action under docket ID number OPP-2002-0072. 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, Crystal 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.
Background and Statutory Findings
EPA, on its own initiative, in accordance with sections 408(e) and section 408(l)(6) of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a, is establishing tolerances for combined residues of the herbicide carfentrazone-ethyl, (ethyl-[alpha],2-dichloro-5-[4- (difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl)-4- fluorobenzenepropanoate) and carfentrazone-ethyl chloropropionic acid ([alpha],2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo- 1H-1,2,4-triazol-1-yl]-4-fluorobenzenepropanoic acid) in or on fruiting vegetables (except cucurbits) (crop group 8) at 0.10 part per million (ppm), tomato paste at 0.60 ppm, and tomato puree at 0.60 ppm. These tolerances will expire and are revoked on June 30, 2004. EPA will publish a document in the Federal Register to remove the revoked tolerances from the Code of Federal Regulations.
In the Federal Register of September 30, 1998 (63 FR 65078) (FRL- 6032-1), the section for carfentrazone-ethyl was added to 40 CFR part 180. The commodity ``soybean seed'' was included at that time. In the Federal Register of August 9, 2000 (65 FR 48626) (FRL-6597-7), Sec. 180.515(a) was revised and the commodity ``soybean seed'' was inadvertently omitted. This document will amend Sec. 180.515(a) to add ``soybean seed.''
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 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.
Emergency Exemption for Carfentrazone-ethyl on Fruiting Vegetables (Except Cucurbits) (Crop Group 8) and FFDCA Tolerances
Paraquat resistant nightshade (Solanum spp.), common groundsel (Portulaca oleracea), and morningglory (Ipomoea spp.) are difficult to control warm season, annual broadleaf weeds that reproduce by seeds. They have high reproductive potential and can be very competitive with tomatoes, peppers, or eggplant during crop establishment.
The alternative chemicals for postemergence control consist of paraquat, diquat, or Enquik (monocarbamide dihydrogen sulfate). Paraquat and diquat resistance, up to 20 fold (increase in rate), has been documented in nightshade species in Florida. Enquik is very corrosive and does not provide acceptable control of nightshade, common purslane, or morningglory. In fact the Enquik label recommends tank mixing with paraquat when used in tomatoes. The chemicals registered for preemergence control of broadleaf weeds in Florida consist of metribuzin, metolachlor, napropamide, and trifluralin. These herbicides do not control nightshade spp., common groundsel, or morningglory. Cultivation and hand weeding will destroy the plastic sheeting used under the crop. The State anticipates yield losses of tomatoes due to nightshade infestations can be greater than 10% compared to the next best alternative. Data from Purdue indicates yield loss averages 5-10% in tomatoes and heavy infestations can cause up to 50% yield loss.
Nightshade species and common groundsel also act as a secondary host for silverleaf whitefly and the pepper weevil both of which can vector Gemini viruses. The applicant says that yield losses due to viruses such as tomato motile virus and tomato yellow leafcurl virus can reduce yields up to 60% or more. Data from Texas in peppers indicates the pepper weevil can directly reduce yields by up to 50% due to the larvae feeding on the fruit. The Agency estimates that yield losses due to weeds and the insects they harbor can be in the range of 10 to 60%. EPA has authorized under FIFRA section 18 the use of carfentrazone-ethyl on fruiting vegetables (except cucurbits) (crop group 8) for control of nightshade, morningglory, and purslane in Florida. 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 carfentrazone-ethyl in or on fruiting vegetables (except cucurbits) (crop group 8). In doing so, EPA considered the safety standard in FFDCA section 408(b)(2), and EPA decided that the necessary tolerance 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, 2004, under FFDCA section 408(l)(5), residues of the pesticide not in excess of the amounts specified in the tolerance remaining in or on fruiting vegetables (except cucurbits) (crop group 8) 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 this tolerance 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 are being approved under emergency conditions, EPA has not made any decisions about whether carfentrazone- ethyl meets EPA's registration requirements for use on fruiting vegetables (except cucurbits) (crop group 8) or whether a permanent tolerance for this use would be appropriate. Under these circumstances, EPA does not believe that these tolerances serve as a basis for registration of carfentrazone-ethyl 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 Florida 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 carfentrazone-ethyl, contact the Agency's Registration Division at the address provided under FOR FURTHER INFORMATION CONTACT.
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 carfentrazone-ethyl and to make a determination on aggregate exposure, consistent with section 408(b)(2), for time-limited tolerances for combined residues of carfentrazone-ethyl, (ethyl-[alpha],2-dichloro-5-
[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-triazol-1-yl)- 4-fluorobenzenepropanoate) and carfentrazone-ethyl chloropropionic acid ([alpha] ,2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo- 1H-1,2,4-triazol-1-yl]-4-fluorobenzenepropanoic acid) carfentrazone- ethyl, in or on fruiting vegetables (except cucurbits) (crop group 8) at 0.10 ppm, tomato paste at 0.60 ppm, and tomato puree at 0.60 ppm. EPA's assessment of the dietary exposures and risks associated with establishing the tolerance follows.
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-\6\ or 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 (MOEcancer= point of departure/exposures) is calculated. A summary of the toxicological endpoints for carfentrazone-ethyl used for human risk assessment is shown in the following Table 1:
Table 1.--Summary of Toxicological Doses and Endpoints for Carfentrazone-ethyl for Use in Human Risk Assessment
Dose Used in FQPA SF* and LOC Exposure Scenario
Risk Assessment, for Risk
Study and Toxicological Effects UF
Acute dietary (General
NOAEL = 500 mg/ FQPA SF = 1
Acute neurotoxicity study in rats population including females kg/day
aPAD = acute RfD/ LOAEL = 1,000 mg/kg/day based on clinical 13-50 years of age, infants, UF = 100........ FQPA.
observations (i.e., salivation) and decreased and children)
Acute RfD = 5 mg/ SF = 5 mg/kg/day
motor activity. kg/day. ..............
Chronic dietary (All
NOAEL = 3 mg/kg/ FQPA SF = 1
Two-year chronic toxicity study in rats. populations)
cPAD = chronic
LOAEL = 12 mg/kg/day based on liver UF = 100........ RfD/.
histopathology (increases in microscopic red Chronic RfD = FQPA............ fluorescence of the liver, liver pigment) and 0.03 mg/kg/day. SF = 0.03 mg/kg/
total mean urinary porphyrin. day.
Short-term incidental oral NOAEL = 500 mg/ LOC for MOE =
Acute neurotoxicity study in rats. exposures (1 to 7 days)
LOAEL = 1,000 mg/kg/day based on clinical (residential) observations (i.e., salivation) and decreased motor activity.
Intermediate-term incidental NOAEL = 50 mg/kg/ LOC for MOE =
Subchronic oral toxicity study in the dog. oral exposures (1 week to day
LOAEL = 150 mg/kg/day based on decreased several months)
body weight gain and increased porphyrin levels.
Short-term dermal (1 to 7 None
No systemic toxicity was seen at the limit- days) and intermediate-term
dose (1,000 mg/kg/day) in a 21-day dermal dermal (1 week to several
toxicity study in rats. months) (residential)
Long-term dermal (several None
None months to lifetime) (residential)
Short-term inhalation (1 to 7 Inhalation (or LOC for MOE =
Acute neurotoxicity study in rats. days) (residential)
oral) study 100
LOAEL = 1,000 mg/kg/day based on clinical NOAEL= 500 mg/kg/ (residential)... observations (i.e., salivation) and motor day.
activity changes (inhalation
.............. absorption rate = 100%).
Intermediate-term inhalation Inhalation (or LOC for MOE =
Subchronic toxicity study in dogs. (1 week to several months) oral) study 100
LOAEL = 150 mg/kg/day based on decreased body (residential)
NOAEL= 50 mg/kg/ (residential) weight gain and increased porphyrin levels day (inhalation absorption rate = 100%).
Long-term inhalation (several Inhalation (or LOC for MOE =
Chronic toxicity study in rats. months to lifetime)
oral) study 100
LOAEL = 12 mg/kg/day based on liver (residential)
NOAEL= 3 mg/kg/ (residential)
histopathology and increased urinary day (inhalation
porphyrin levels. absorption rate = 100%).
Cancer (oral, dermal,
There was no evidence of carcinogenicity in inhalation)
ethyl has been
either a mouse carcinogenicity study or a rat classified as
carcinogenicity study. ``not likely'' to be a human carcinogen.
* The reference to the FQPA Safety Factor refers to any additional safety factor retained due to concerns unique to the FQPA.
Dietary exposure from food and feed uses. Tolerances have been established (40 CFR 180.515) for the combined residues of carfentrazone-ethyl, in or on a variety of raw agricultural commodities including corn, cereal grains, cotton, rice, soybeans and sorghum. Risk assessments were conducted by EPA to assess dietary exposures from carfentrazone-ethyl 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 1 day or single exposure. The Dietary Exposure Evaluation Model (DEEM[reg]) 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: 100% crop treated, tolerance level residues for all commodities, and DEEM[reg] default processing factors for all registered and proposed commodities.
ii. Chronic exposure. In conducting this chronic dietary risk assessment, the DEEM[reg] 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: 100% crop treated, tolerance level residues for all commodities, and DEEM[reg] default
processing factors for all registered and proposed commodities.
iii. Cancer. Carfentrazone-ethyl has been classified as ``not likely'' to be a human carcinogen. Therefore, risk assessments to estimate cancer risk were not conducted.
Dietary exposure from drinking water. The Agency lacks sufficient monitoring exposure data to complete a comprehensive dietary exposure analysis and risk assessment for carfentrazone-ethyl 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 carfentrazone-ethyl.
The Agency uses the First Index Reservoir Screening Tool (FIRST) or the Pesticide Root Zone/Exposure Analysis Modeling System (PRZM/EXAMS) to produce estimates of pesticide concentrations in an index reservoir. The SCI-GROW model is used to predict pesticide concentrations in shallow ground water. For a screening-level assessment for surface water, EPA will generally use FIRST (a tier 1 model) before using PRZM/ EXAMS (a tier 2 model). The FIRST model is a subset of the PRZM/EXAMS model that uses a specific high-end runoff scenario for pesticides. While both FIRST and PRZM/EXAMS incorporate an index reservoir environment, 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 comparisons (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 carfentrazone-ethyl, they are further discussed in the aggregate risk sections below.
Based on the FIRST and SCI-GROW models, the EECs of carfentrazone- ethyl for acute exposures are estimated to be 34.3 parts per billion (ppb) for surface water and 13.4 ppb for ground water. The EECs for chronic exposures are estimated to be 19 ppb for surface water and 13.4 ppb for ground water.
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).
Carfentrazone-ethyl is currently registered for use on the following residential non-dietary sites: Ornamental lawns and turf, including residential and institutional lawns. Therefore, the Agency assessed the estimated exposure from non-dietary exposures. The Agency assessed the non-dietary incidental ingestion via hand-to-mouth exposure by a toddler as this scenario was anticipated to represent the highest exposure potential in the residential setting. Since dermal endpoints have not been selected, no residential post-application dermal assessment was conducted.
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'' 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 carfentrazone-ethyl 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, carfentrazone-ethyl 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 carfentrazone-ethyl 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).
Safety Factor for Infants and Children
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.
i. Developmental toxicity studies. In a developmental toxicity study in rats, body weight, body weight gain, food consumption, gross pathology, and cesarean section data were similar between control and treated groups. The maternal LOAEL is 600 mg/kg/day (based on staining of the abdominogenital area and of the cage pan liner) the maternal NOAEL is 100 mg/kg/day. Evaluation of litter data and an assessment of embryonic and fetal development, including litter size, post- implantation loss, fetal weights, and sex ratio, did not reveal any evidence of treatment-related toxicity. Examination of fetuses for alterations of external, visceral, and skeletal development revealed significantly increased litter incidences of wavy and thickened ribs in the 1,250 mg/kg/day treatment group. The developmental LOAEL is 1,250 mg/kg/day (based upon a significant increase in the litter incidences of wavy and thickened ribs); the developmental NOAEL is 600 mg/kg/day.
In a developmental toxicity study in rabbits, evidence of treatment-related maternal toxicity consisted of unthriftiness and emaciation in two does at 300 mg/kg/day. The maternal LOAEL is 300 mg/ kg/day; the maternal NOAEL is greater than or equal to 150 mg/kg/day. There was no evidence of treatment-related prenatal developmental toxicity: The developmental LOAEL was not determined; the developmental NOAEL is greater than or equal to 300 mg/kg/day.
ii. Reproductive toxicity study. In a 2-generation reproduction study in rats, the parental systemic LOAEL is 4,000 ppm (equivalent to 343 mg/kg/day for males and 387 mg/kg/day for females) based on decreased body weight gains, increased liver weights, liver and bile
duct histopathology, and reductions in the mean cell volume (F0and F1males, F1females), mean cell hemoglobin (F0and F1males, F1 females), hematocrit (F1males), and hemoglobin (F1males). The parental systemic NOAEL is 1,500 ppm (equivalent to 127 mg/kg/day for males and 142 mg/kg/day for females). The offspring LOAEL is 4,000 ppm (387 mg/kg/day) based on decreased pup body weights in both sexes of the F 2generation. The offspring NOAEL is 1,500 ppm (142 mg/kg/day).
iii. Prenatal and postnatal sensitivity. The toxicity data provided no indication of increased susceptibility of rats or rabbits to in utero and/or postnatal exposure to carfentrazone-ethyl. In the prenatal developmental toxicity studies in rats and rabbits and the 2-generation reproduction study in rats, effects in the offspring were observed only at or above treatment levels which resulted in evidence of parental toxicity.
Conclusion. There are no data gaps for the assessment of the effects of carfentrazone-ethyl following in utero and/or postnatal exposure. There is a complete toxicity data base for carfentrazone- ethyl and exposure data are complete or are estimated based on data that reasonably accounts for potential exposures. The data provided no indication of increased susceptibility of rats or rabbits to in utero and/or postnatal exposure to carfentrazone-ethyl. Based on the toxicity profile for carfentrazone-ethyl, a developmental neurotoxicity study in rats is not required. Therefore, the FQPA Safety Factor, for enhanced sensitivity to infants and children was reduced from 10X to 1X.
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 EPA's Office of Water are used to calculate DWLOCs: 2L/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, EPA concludes with reasonable certainty that exposures to carfentrazone-ethyl in drinking water (when considered along with other sources of exposure for which EPA has reliable data) would not result in unacceptable levels of aggregate human health risk at this time. Because EPA 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, EPA will reassess the potential impacts of carfentrazone-ethyl on drinking water as a part of the aggregate risk assessment process.
Acute risk. Using the exposure assumptions discussed in this unit for acute exposure, the acute dietary exposure from food to carfentrazone-ethyl will occupy 1% or less of the aPAD for the U.S. population and all population subgroups represented in DEEM[reg]. In addition, despite the potential for acute dietary exposure to carfentrazone-ethyl in drinking water, after calculating DWLOCs and comparing them to conservative model EECs of carfentrazone-ethyl in surface water 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 Carfentrazone-ethyl
Surface Ground Population Subgroup
aPAD (mg/ % aPAD Water EEC Water EEC Acute DWLOC kg)
02-14770Filed6-11-02; 8:45 am] BILLING CODE 6560-50-S