Pesticides; tolerances in food, animal feeds, and raw agricultural commodities: Propoxycarbazone-sodium,

[Federal Register: July 7, 2004 (Volume 69, Number 129)]

[Rules and Regulations]

[Page 40774-40781]

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

[DOCID:fr07jy04-9]

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 180

[OPP-2004-0172; FRL-7365-7]

Propoxycarbazone-sodium; Pesticide Tolerance

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

SUMMARY: This regulation establishes a tolerance for combined residues of propoxycarbazone-sodium and its metabolite in or on meat, meat byproducts, wheat and milk. Bayer CropScience 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 July 7, 2004. Objections and requests for hearings must be received on or before September 7, 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 ID number OPP-2004-0172. 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., Confidential Business Information (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 Bell Street, 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:

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 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.

   2. 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/. The OPPTS Harmonized Test Guidelines

      referenced in this document are avaiable at http://www.epa.gpo/opptsfrs/home/guidelin.htm/ .

2. Background and Statutory Findings

   In the Federal Register of August 21, 2002 (67 FR 54188) (FRL-7195- 2), 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 0F6094) by Bayer Corporation, 8400 Hawthorn Road, Kansas City MO, 64120-0013. That notice included a summary of the petition prepared by Bayer Corporation, the registrant. There were no comments received in response to the notice of filing. The company name and address were subsequently changed to Bayer CropScience, P.O. Box 12014, 2 T.W. Alexander Drive, Research Triangle Park, NC 27709.

   The petition requested that 40 CFR 180 be amended by establishing tolerances for residues of the herbicide, propoxycarbazone-sodium, methyl 2-[[[(4,5-dihydro-4-methyl-5-oxo-3-propoxy-1H-1,2,4-triazol-1- yl)carbonyl]amino]sulfonyl]benzoate, sodium salt and its metabolite, methyl 2-[[[(4,5-dihydro-4-methyl-5-oxo-3-(2'-hydroxy-propoxy)-1H- 1,2,4-triazol-1-yl)carbonyl]amino]sulfonyl]benzoate, in or on the raw agricultural commodities (RACs) wheat forage, wheat hay, wheat straw, wheat grain, meat, and meat byproducts, (cattle, sheep, goats, horses, hogs), and milk at 1.5, 0.15, 0.05, 0.01, 0.05, and 0.002 parts per million (ppm); respectively. Bayer CropScience subsequently amended the petition by requesting that 40 CFR 180 be amended establishing tolerances for residues of the herbicide, propoxycarbazone, methyl 2-

   [[[(4,5-dihydro-4-methyl-5-oxo-3-propoxy-1H-1,2,4-triazol-1- yl)carbonyl] amino]sulfonyl]benzoate, sodium salt and its metabolite, methyl 2-[[[(4,5-dihydro-3-(2-hydroxypropoxy)-4-methyl-5-oxo-1H-1,2,4- triazol-1-yl)carbonyl]amino]sulfonyl]benzoate, in

   [[Page 40775]]

   or on Wheat, forage at 1.5 ppm, Wheat, hay at 0.15 ppm, Wheat, straw at 0.05 ppm, and Wheat, grain at 0.02 ppm and for residues of the herbicide propoxycarbazone, methyl 2-[[[(4,5-dihydro-4-methyl-5-oxo-3- propoxy-1H-1,2,4-triazol-1-yl)carbonyl]amino]sulfonyl]benzoate in or on the Meat of cattle, sheep, goat and horse at 0.05 ppm, Meat byproducts of cattle, sheep, goat and horse at 0.05 ppm and Milk at 0.004 ppm.

   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).

3. 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 tolerances for combined residues of propoxycarbazone-sodium and its metabolite on Wheat, forage at 1.5 ppm, Wheat, hay at 0.15 ppm, Wheat, straw at 0.05 ppm, and Wheat, grain at 0.02 ppm and for residues of propoxycarbazone-sodium in or on the Meat of cattle, sheep, goat and horse at 0.05 ppm, Meat byproducts of cattle, sheep, goat and horse at 0.05 ppm and Milk at 0.004 ppm. EPA's assessment of exposures and risks associated with establishing the tolerance follows.

   1. 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 propoxycarbazone- sodium 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-- NOAEL = 286.4 males (M) and 350.6 females rodents (rat)

      (F) milligrams/kilogram/day (mg/kg/day)

      LOAEL = 1507.5 (M) and 1769.9 (F) mg/kg/day based on gastric irritation 870.3100

      90-Day oral toxicity-- NOAEL = 205 (M) and 1159 (F) mg/kg/day rodents (mouse)

      LOAEL = 860 (M) and 5109 (F) mg/kg/day based on decreased body weight, body weight gain and food efficiency

      870.3150

      64-Day oral toxicity-- NOAEL = 1,407 (M) and 1,181 (F) mg/kg/day nonrodents (dog)(range- Highest Dose Tested (HTD) finding)

      LOAEL not determined

      870.3200

      21/28-Day dermal toxicity NOAEL = 1,000 mg/kg/day (HTD) LOAEL not determined

      870.3700

      Prenatal developmental-- Maternal NOAEL equal or greater than (>=) rodents (rat)

      1,000 mg/kg/day (HTD) Maternal LOAEL not determined Developmental NOAEL >= 1,000 mg/kg/day (HTD) Developmental LOAEL not determined

      870.3700

      Prenatal developmental-- Maternal NOAEL = 100 mg/kg/day nonrodents (rabbit)

      Maternal LOAEL = 500 mg/kg/day based on reduced body weight gain and food consumption, GI toxicity and decreased water consumption and urination Developmental NOAEL = 500 mg/kg/day Developmental LOAEL = 1,000 mg/kg/day based on an abortion, decrease in mean fetal weights, and elevated pre- and post- implantation loss.

      870.3800

      Reproduction and fertility Parental/Systemic NOAEL = 74.8-79.6 (M) and effects

      373.5-413.5 (F) mg/kg/day Parental/Systemic LOAEL = 297.1-322.9 (M) and 1605.3-1907.5 (F) mg/kg/day based on microscopic lesions of the stomach. Reproductive NOAEL = 1230.7-1313.9 (M) and 373.5-413.5 (F) mg/kg/day Reproductive LOAEL = 1605.3-1907.5 (F) mg/ kg/day based on increased in diestrous/ metestrous Offspring NOAEL = 297.1-322.9 (M) and 373.5- 413.5 (F) mg/kg/day Offspring LOAEL = 1230.7-1313.9 (M) and 1605.3-1907.5 (F) mg/kg/day based on increased postimplantation loss and decreased live litter size in the F2 litters

      [[Page 40776]]

      870.4100

      Chronic toxicity--dogs NOAEL = 630.7 mg/kg/day LOAEL > 630.7 mg/kg/day

      870.4300

      Combined chronic toxicity NOAEL = 43 (M) and 49 (F) mg/kg/day carcinogenicity - rodents LOAEL = 459 (M) and 525 (F) mg/kg/day based (rats)

      on decreased body weight and increased urinary pH (preceding histological changes in the kidney of rats in the mid- and high- dose groups such as: Foci of mineralization of pelvis, dilated and cystic renal tubules filled with proteinaceous material, regenerative tubular epithelium, glomerular and interstitial fibrosis, and hyperplasia of the pelvic epithelium). No evidence of carcinogenicity

      870.4300

      Carcinogenicity--mice NOAEL = 369.0 (M) mg/kg/day and 3,106.1 (F) mg/kg/day (HTD) LOAEL = 1,880.9 (M) mg/kg/day based on decreased body weight gain combined with lower food efficiency. No evidence of carcinogenicity

      870.5100

      Gene mutation--Ames

      Negative

      870.5100

      Gene mutation--Ames

      Negative

      870.5100

      Gene mutation--Ames

      Negative

      870.5300

      Gene mutation--In vitro Negative Chinese hamster V79-HPRT

      870.5375

      Cytogenetics--In vitro Negative Chinese hamster

      870.5375

      Cytogenetics--In vitro Negative Chinese hamster

      870.5395

      Cytogenetics--Hsd/Win: Negative NMRI mouse bone marrow micronucleus

      870.5550

      Other effects--UDS

      Negative

      870.6200

      Acute neurotoxicity

      NOAEL = 2,000 (M) and 800 (F) mg/kg (HDT) screening battery

      LOAEL = 2,000 (F) mg/kg/day based on decrease in body weight gains

      870.6200

      Subchronic neurotoxicity NOAEL >= 1,321 (M) and 1,651 (F) mg/kg/day screening battery

      (HDT) LOAEL not established

      870.7485

      Metabolism and

      Based on the amount of radiolabel recovered pharmacokinetics

      in the urine, 23-26% of the radiolabeled test material was absorbed by the males, with females absorbing slightly more (31%). Absorption in male rats that received 200 mg/kg was 21%. Radiolabel position did not influence absorption. Plasma Tmax was rapid, being 0.33 hours regardless of radiolabel position in rats that received 2 mg/kg and 0.81 hours in rats that received 200 mg/kg. No bioaccumulation or tissue reservoirs were found; this result confirmed by whole body autoradiography. Plasma clearance was biphasic and rapid, with a T1/81/25/29/ 21/13/23/85/83/8 for the first phase of 1.1 hours for the compound labeled in the triazol position and 0.6 hours for the compound labeled in the phenyl position, regardless of dose. No radiolabel effects were noted in the second phase plasma T1/81/25/29/ 21/13/23/85/83/8 which was 11 hours at 2 and 200 mg/kg of test material. Plasma area under the curve (AUC) was 3.6 [mu]g/mLhour for rats that received 2 mg/kg radiolabeled propoxycarbazone-sodium and 45 times greater (169 [mu]g/mLhour) in rats that received 200 mg/kg. The radiolabeled test material was primarily eliminated unchanged in the urine and feces (75-88% of the administered dose), with essentially none eliminated by the lungs. Of the absorbed radiolabeled test material, 90% was excreted into the urine while the remaining was recovered from the bile. However, radiolabel position influenced the metabolic products. Two minor metabolites that contributed -\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 propoxycarbazone- sodium used for human risk assessment is shown in Table 2 of this unit:

      Table 2.--Summary of Toxicological Dose and Endpoints for propoxycarbazone-sodium for Use in Human Risk Assessment

      Dose Used in Risk Assessment, Interspecies Special FQPA SF and LOC Study and Toxicological Exposure Scenario

      and Intraspecies and any Traditional UF for Risk Assessment

      Effects

      Acute dietary

      An endpoint of concern attributable to a single dose (exposure) was not identified from the available studies. An acute RfD was not established

      Chronic dietary (all populations)

      NOAEL= 74.8 mg/kg/day Special FQPA SF = 1X Two-generation reproduction UF = 100X cPAD = chronic RfD /

      study in rats Chronic RfD = 0.748 mg/kg/day Special FQPA SF = 0.748 LOAEL = 297.1 mg/kg/day mg/kg/day based on microscopic lesions of the stomach in parental male rats

      Cancer (oral, dermal, inhalation)

      Not likely to be a carcinogen for humans based on the lack of carcinogenicity in a rat carcinogenicity study, an mouse carcinogenicity study and a battery of mutagenic studies.

   3. Exposure Assessment

      1. Dietary exposure from food and feed uses. Tolerances have not been previously established (40 CFR 180) for the residues of propoxycarbazone-sodium in or on raw agricultural commodities. Risk assessments were conducted by EPA to assess dietary exposures from propoxycarbazone-sodium 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.

         An effect of concern attributable to a single exposure (dose) was not identified from the oral toxicity studies including the developmental toxicity studies in rat and rabbits. Abortions seen in the developmental toxicity study in rabbits at 1,000 mg/kg/day during GD 19-28, were not considered to be a single dose effect. Since they occur late in gestation after repeated exposures.

         ii. Chronic exposure. In conducting the chronic dietary risk assessment EPA used the Dietary Exposure Evaluation Model software with the Food Commodity Intake Database (DEEM-

         [[Page 40778]]

         FCID\TM\), which incorporates 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: For the chronic analyses, tolerance-level residues were assumed for all food commodities with current or proposed propoxycarbazone-sodium tolerances, and it was assumed that all of the crops included in the analysis were treated. Percent Crop Treated (PCT) and/or anticipated residues were not used in the chronic risk assessment.

      2. Dietary exposure from drinking water. The Agency lacks sufficient monitoring exposure data to complete a comprehensive dietary exposure analysis and risk assessment for propoxycarbazone-sodium 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 propoxycarbazone-sodium.

         The Agency uses the FQPA Index Reservoir Screening Tool (FIRST) or the Pesticide Root Zone Model/Exposure Analysis Modeling System (PRZM/ EXAMS), to produce estimates of pesticide concentrations in an index reservoir. The screening concentration in ground water (SCI-GROW) model is used to predict pesticide concentrations in shallow ground water. For a screening-level assessment for surface water EPA will 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. Both FIRST and PRZM/EXAMS incorporate an index reservoir environment, and both models include 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 screen for sorting out pesticides for which it is unlikely that drinking water concentrations would exceed human health LOC.

         Since the models used are considered to be screening tools in the risk assessment process, the Agency does not use estimated environmental concentrations (EECs), which are the model estimates of a pesticide's concentration in water. EECs derived from these models are used 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 propoxycarbazone- sodium they are further discussed in the aggregate risk sections in Unit E.

         Based on the FIRST and SCI-GROW models, the EECs of propoxycarbazone-sodium for acute exposures are estimated to be 2.3 parts per billion (ppb) for surface water and 0.4 ppb for ground water. The EECs for chronic exposures are estimated to be 0.9 ppb for surface water and 0.4 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).

         Propoxycarbazone-sodium is not registered for use on any sites that would result in residential exposure.

      4. 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.''

         EPA does not have, at this time, available data to determine whether propoxycarbazone-sodium has a common mechanism of toxicity with other substances. 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 propoxycarbazone-sodium and any other substances and propoxycarbazone- sodium 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 propoxycarbazone-sodium 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 from substances found to have a common mechanism on EPA's web site at http://www.epa.gov/pesticides/cumulative/ .

   4. Safety Factor for Infants and Children

      1. 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.

      2. Conclusion. The toxicology database is complete for FQPA purposes and there are no residual uncertainties for pre-/post-natal toxicity. Based on the quality of the exposure data, EPA determined that the 10X SF to protect infants and children should be removed. The FQPA factor is removed based on the following:

      (i) There is no quantitative or qualitative evidence of increased susceptibility of rat and rabbit fetuses to in utero exposure to propoxycarbazone-sodium in developmental toxicity studies. There is no quantitative or qualitative evidence of increased susceptibility to propoxycarbazone-sodium following pre-/post-natal exposure to a 2- generation reproduction study.

      (ii) There is no concern for developmental neurotoxicity resulting from exposure to propoxycarbazone-sodium. A developmental neurotoxicity study (DNT) study is not required.

      (iii) The toxicological database is complete for FQPA assessment.

      [[Page 40779]]

      (iv) The chronic dietary food exposure assessment utilizes HED- recommended tolerance level residues and 100% CT information for all commodities. By using these screening-level assessments, actual exposures/risks will not be underestimated.

      (v) The dietary drinking water assessment utilizes water concentration values generated by model and associated modeling parameters which are designed to provide conservative, health protective, high-end estimates of water concentrations which will not likely be exceeded.

   5. 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, EPA concludes with reasonable certainty that exposures to the pesticide 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 residues of the pesticide in drinking water as a part of the aggregate risk assessment process.

      1. Acute risk. An effect of concern attributable to a single exposure (dose) was not identified from the oral toxicity studies including the developmental toxicity studies in rat and rabbits. No acute risk is expected from exposure to propoxycarbazone-sodium.

      2. Chronic risk. Using the exposure assumptions described in this unit for chronic exposure, EPA has concluded that exposure to propoxycarbazone-sodium from food will utilize