John Pates, Jr. Reregistration Branch Special Review and Reregistration Division (7508W)

Transcription

1 May 7, 2004 MEMORANDUM SUBJECT: Trifluralin: Human Health Risk Assessment PC Code: Case No: 0179 DP Barcode: FROM: THROUGH: TO: Richard Griffin, Risk Assessor Reregistration Branch II Health Effects Division Alan Nielsen, Branch Senior Scientist Reregistration Branch II Health Effects Division (7509C) John Pates, Jr. Reregistration Branch Special Review and Reregistration Division (7508W) The following human health risk assessment for trifluralin has been prepared by the Health Effects Division for Phase One of the Tolerance Reassessment Eligibility Decision (TRED) process for trifluralin. Occupational risk assessment for trifluralin is not addressed in this document. Aggregate (food / drinking water / residential) risk assessment is based on the following memoranda: Trifluralin: Report of the Hazard Identification Assessment Review Committee (R. Fricke memo, 5/2/03) Trifluralin: Toxicology Disciplinary Chapter for the Tolerance Reassessment Eligibility Decision Document (R. Fricke memo, 10/2/03) Trifluralin. Product Chemistry Chapter for the TRED Document (K. Dockter memo, 12/23/03) Trifluralin: Residue Chemistry Chapter (R. Griffin memo, 3/4/04) Trifluralin. Metabolism Assessment Review Committee Briefing Memorandum

2 (S. Piper memo, 1/6/04) Trifluralin: Health Effects Division (HED) Metabolism Assessment Review Committee (MARC) Decision Document. (S. Piper memo, 3/9/04) Trifluralin: Anticipated Residues, Acute, Chronic, and Cancer Dietary Exposure Assessments for the Reregistration Eligibility Decision (S. Piper memo, 4/12/04) Trifluralin: Drinking Water Assessment for Tolerance Reassessment Eligibility Decision (S. Ramasamy memo, 12/11/03) Residential Exposure Assessment and Recommendations for the Tolerance Reassessment Evaluation Decision (TRED) Document for Trifluralin (S. Recore memo, 5/6/04) Review of Trifluralin Incident Reports (J. Blondell memo, 5/5/04) 2

3 CONTENTS Pg. l.0 SUMMARY PHYSICAL / CHEMICAL PROPERTIES CHARACTERIZATION TOXICOLOGY Toxicity Profile FQPA Considerations Dose-Response Assessment Endocrine Disruption Potential DIETARY / RESIDENTIAL EXPOSURE / RISK Usage Summary Dietary Exposure / Food Dietary Exposure / Water Dietary Risk Estimates Residential Exposure AGGREGATE EXPOSURE / RISK CUMULATIVE RISK HUMAN INCIDENT DATA REVIEW DATA REQUIREMENTS / LABEL REVISIONS TABLES Table 1 Nomenclature 9 Table 2 Physicochemical Properties 9 Table 3 Acute Toxicity 10 Table 4 Toxicology Endpoint Selection 16 Table 5 Registrations for Agricultural Use 20 Table 6 Estimated Concentrations in Water 29 Table 7 Dietary Risk Estimates 33 Table 8 Residential Applicator Systemic Risk 36 Table 9 Residential Applicator Carcinogenic Risk 38 Table 10 Post-Application Oral Ingestion 41 Table 11 Post-Application Oral Ingestion Combined 41 Table 12 Residential Post-Application Carcinogenic Risk 43 Appendix A 49 3

4 Appendix B 50 Appendix C SUMMARY Trifluralin (2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine) is a selective, pre-emergence, dinitroaniline herbicide registered for the control of annual grasses and certain broadleaf weeds. Trifluralin is primarily used in soybeans and cotton, but is also registered for use on a variety of food and feed crops including: alfalfa, asparagus, barley, Brassica vegetables, bulb vegetables, celery, citrus fruits, corn (field), cotton, cucurbit vegetables, endive, flax, fruiting vegetables, grapes, hops, legume vegetables, peanuts, peppermint, root and tuber vegetables, rapeseed (canola), safflower, sorghum, spearmint, stone fruits, sugarcane, sunflower, tree nuts, and wheat. Tolerances range from 0.05 ppm to 2.0 ppm and adequate enforcement methods are available for the determination of residues in/on plant commodities. Tolerances for residues of trifluralin in animal commodities have not been established. Non-agricultural uses include turf, ornamentals, and vegetable gardens. The toxicity database is sufficient for tolerance reassessment. Technical trifluralin exhibits low acute toxicity in rats via the oral, dermal, and inhalation routes of exposure. In rabbit studies trifluralin is a slight eye irritant, but not a skin irritant; however it was found to be a dermal sensitizer in guinea pigs. Subchronic oral studies in the rat and dog show that the liver and kidneys appear to be the principal target organs. Some blood effects such as lower hemoglobin levels and changes in clinical chemistry are reported. In a special urinalysis study in the male rat, tubular cytoplasmic hyaline droplets, increased total protein, aspartate amino-transferase (AST), and lactate dehydrogenase (LDH) were observed in the urine. Following electrophoresis, albumin, α1-globulin, and α2-globulin were identified in the urine. Histopathological findings included increased incidences of lesions of the renal proximal tubules, decreased corticomedullary mineralization, and hyaline droplets in the tubular epithelium in the rat. In the dog, multifocal cortical tubular cytoplasmic pigment deposition was observed. Chronic toxicity to trifluralin was evaluated in the rat, mouse, and dog. Systemic toxicity in rats included decreases in body weight and body weight gains. Two 12- month oral toxicity studies were performed in the dog. In one study, increased frequency of abnormal stool, decreased body weights, decreased body weight gains, decreased erythrocytes and hemoglobin, and increased thrombocytes in males were observed, while increased absolute liver weights were observed in the other. Trifluralin does not appear to be an immunotoxicant. There were no signs of neurotoxicity in the trifluralin data base. 4

5 In a rat metabolism study many non-conjugated (20-30) and conjugated (10-20) urinary metabolites were observed with the majority present at 1-2% of the total urinary radioactivity. Four metabolic pathways were identified; (1) oxidative N-dealkylation of one or both propyl groups and metabolites which were hydroxylated on the propyl side chain; (2) reduction of one or both nitro groups to the corresponding amine; (3) cyclization reactions to give a variety of substituted and unsubstituted benzimidazole metabolites; and (4) conjugation reactions, including acetylation of the reduced nitro groups, sulfate, and glucuronic acid conjugates. In developmental toxicity studies, maternal toxicity consisted of decreased body weight gain and food consumption, increased liver and spleen weights, increased incidence of resorptions and litters with total resorptions in the rat; and an increased number of abortions, macroscopic changes in the liver and lungs, and decreased food consumption in the rabbit. Reduced ossification of vertebrae and ribs were observed in both the rat and rabbit. In reproduction studies kidney toxicity (acute renal failure, lesions of renal proximal tubule, increased relative liver) and uterine atrophy in females were observed. Offspring toxicity consisted of decreased pup weight and increased number of runts. Decreased fetal, neonatal, and litter viability, and decreased lactation index were also observed. The toxicity database is adequate for FQPA consideration. The concern for qualitative susceptibility is low even though some effects seen in the rat developmental study indicate some susceptibility. The HIARC determined that since the dose response was well characterized, the developmental effects were only seen in the presence of materanal toxicity, and clear NOAELs were established for developmental and maternal toxicities, the concern for susceptibilty was low. There are no residual uncertainties for pre-and post-natal toxicities since the doses selected for overall risk assessments will address the concerns seen in these studies. Based on the above data, no Special FQPA Safety Factor is needed (1x) since there are no residual uncertainties for pre- and/or post-natal toxicity. The HIARC reviewed the trifluralin toxicity data and selected the appropriate studies, endpoints, and dose levels for human health risk assessment. An acute Population Adjusted Dose (apad) of 1.0 mg/kg/day was established for females of child-bearing age based on the No Observable Adverse Effect (NOAEL) of 100 mg/kg/day observed in the rat developmental study. A chronic Population Adjusted Dose (cpad) of mg/kg/day was established based on the NOAEL (2.4 mg/kg/day) of a chronic toxicity study in dogs. The endpoint(s) of concern is increased frequency of abnormal stool, decreased body weights, decreased body weight gains, decreased erythrocytes and hemoglobin, and increased thrombocytes in males at the 5

6 study LOAEL. The uncertainty factor is 100, based on 10x for inter-species extrapolation, 10x intra-species variability, and 1x for FQPA considerations. Risk assessment by the Margin of Exposure (MOE) approach for short-term incidental oral exposure to children is based on the NOAEL (10 mg/kg/day) of the two-generation reproduction study in the rat. Risk assessment by the MOE approach for short-term inhalation exposure to residential applicators is based on the NOAEL (81 mg/kg/day) of the 30-day inhalation study in rats. Risk assessment by the MOE approach for short-term dermal exposure is not quantified based on no systemic toxicity observed at the limit dose in the dermal toxicity study. Intermediate- and long-term residential exposure is not expected for trifluralin and not assessed. The Agency considers a Margin of Exposure (MOE) of 100 to be adequately protective for each assessment. On January 29 and February 27, 1986, the Carcinogenicity Peer Review Committee classified trifluralin as a Group C Carcinogen ( possible human carcinogen), and recommended that, for the purpose of risk characterization, a low dose extrapolation model be applied to the experimental animal tumor data for quantification of human risk. The upper-bound potency factor (Q 1 *) for trifluralin is 5.8 x 10-3 (mg/kg/day) -1 based on male rat thyroid follicular cell combined adenoma, papillary adenoma, cystadenoma, and carcinoma tumors (converted from animals to humans by use of the 3/4's scaling factor). Extensive testing showed trifluralin is neither mutagenic nor genotoxic, and does not inhibit the polymerization of microtubules in mammalian cells. The HED Metabolism Assessment Review Committee (MARC) reviewed trifluralin toxicology and metabolism data (2/4/04) and concluded that tolerances for enforcement (and dietary risk assessment for plant commodities) should be based on trifluralin per se. Also, dietary risk assessment for ruminant commodities should be based on trifluralin per se and all metabolites/degradates identified as total radioactive residue, or TRR, in a ruminant metabolism study. Risk assessment for drinking water contamination is based on estimates for trifluralin per se and 3 metabolites identified in metabolism and photolysis studies. All metabolites/degradates are considered toxicologically similar to parent. Trifluralin is not acutely toxic and there is no expectation that single,or singleday high-end exposure, including aggregate exposure, will have an adverse effect. However, based on the toxicity observed in sub-chronic and chronic studies, trifluralin has been assessed for the following; 1) acute exposure from food and water (apad); 2) chronic exposure from food and water (cpad); 3) chronic exposure from food and water (Q 1 *); 4) short-term inhalation exposure to homeowner applicators (MOE); 5) combined inhalation and dermal exposure to homeowner applicators (Q 1 *); 6) short-term oral exposure to children post-application on turf (MOE); and 7) dermal exposure to persons 6

7 (golfers, etc.) post-application on turf (Q 1 *). A refined chronic dietary risk assessment was conducted by comparing trifluralin dietary exposure, due to food uses and contaminated drinking water, to the trifluralin cpad and secondly, by quantifying carcinogenic risk by the Q 1 * approach. The dietary assessment relies on field trial, monitoring (PDP), and usage data (percent crop treated). Contamination estimates for drinking water are refined by PRZM-EXAMS modeling, incorporating percent cropped area (PCA) data. Food consumption data are from the USDA s Continuing Surveys of Food Intakes by Individuals (CSFII), /1998, combined to form the Food Commodity Intake Database (FCID). For the cpad dietary risk estimates, the assessment uses averaged consumption data for the general U.S. population and various population subgroups and for carcinogenic risk uses an overall average. Estimated chronic dietary risk estimates for all population subgroups are less than 1% of the trifluralin cpad (0.005 mg/kg/day) and do not indicate a concern for this route of exposure. Carcinogenic risk for the general U.S. population, based on food and drinking water, is 10-7 and less than the level (10-6 ) considered negligible by the Agency. Trifluralin products are marketed for homeowner use on lawns, landscape ornamentals, and vegetable gardens. Trifluralin-containing products are also marketed for use by professional applicators on residential turf, on golf courses, other turf such as recreational/commercial areas, and on ornamental plantings. Based on these uses, trifluralin is assessed for the residential applicator (or handler ) and for postapplication exposure that may occur from turf contact. For residential applicators, all estimated inhalation MOEs are above the target MOE of 100 and the carcinogenic risk estimate for typical turf applications is Since a toxicological endpoint, based on dermal exposure, was not selected for trifluralin, only post-application incidental oral ingestion (i.e., soil, granule, and hand-tomouth ingestion) exposures to children were calculated. Estimated MOEs for soil, granule, and hand-to-mouth exposures are above the target MOE of 100. However, carcinogenic risk has been estimated, based on dermal exposure during golfing or other activity, over a lifetime of exposure. These estimates are less than 10-8 and are again, considered upper-bound estimates. The Agency remains concerned about dermal sensitization reactions to adults and children who are exposed to trifluralin in residential settings and recommends for labeling to this effect, on all products. Acute dietary exposure based on both food and drinking water sources has been aggregated and the apad risk estimate is less than 1% for women of child-bearing age. Chronic dietary exposure based on both food and drinking water sources has been aggregated and the cpad risk estimates are less than 1% for the general U.S. 7

8 population, and population sub-groups. Oral exposure estimates for 3 specific postapplication activities of children on treated turf have been aggregated to form an upperbound MOE risk estimate that is well above the target level of 100. For trifluralin, chronic exposure from foods ( mg/kg/day) has been added to chronic exposure due to drinking water ( mg/kg/day) and this in turn is added to estimates of residential exposure to estimate carcinogenic risk. Since carcinogenic risk assessment attempts to reflect long-term exposure, the most appropriate exposure estimate would be based on the most common application method; the push-type spreader. The Lifetime Average Daily Dose estimated for this application method is negligible ( mg/kg/day), and when added to the chronic dietary exposure the aggregate carcinogenic risk estimate is 2x10-7. Although recognized as a member of the dinitroaniline group of pesticides, cumulative risk assessment has not been completed for trifluralin. HED has not initiated a comprehensive review to determine if other chemical substances have a mechanism of toxicity common to trifluralin. Based on California incident data and the Agency s Incident Data System, it appears that the majority of reported trifluralin cases involved skin and eye illnesses. Poison Control Center data would tend to support these results, in that dermal and ocular effects were some of the most common effects reported. Appropriate protective clothing to protect the skin and eyes of applicators is recommended. 8

9 2.0 PHYSICAL / CHEMICAL PROPERTIES Table 1 Trifluralin Nomenclature H 3 C N CH 3 Chemical structure O 2 N NO 2 CF 3 Common name Trifluralin Molecular Formula C 13 H 16 F 3 N 3 O 4 Molecular Weight IUPAC name α,α,α-trifluroro-2,6-dinitro-n,n-dipropyl-p-toluidine CAS name 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine CAS # PC Code Table 2 Physicochemical Properties of Trifluralin Parameter Value Reference Melting point/range 42-49EC Trifluralin Update 10/29/91 ph 5.9 ± 0.1 saturated aqueous solution Density or specific gravity ( g/ml D207577, 4/9/97, K. Dockter C) Water solubility (25 C) <1 ppm D207577, 4/9/97, K. Dockter Solvent solubility (25 C) readily soluble in organic solvents such as acetone, acetonitrile, chloroform, dichloromethane, ethyl acetate, and toluene at >100 g/100 ml, and in hexane at g/100 ml or methanol at g/100 ml D207577, 4/9/97, K. Dockter Vapor pressure (25 C) 6.1 x 10-3 Pa D207577, 4/9/97, K. Dockter Dissociation constant (pk a ) not required; does not dissociate D207577, 4/9/97, K. Dockter Octanol/water partition coefficient (log K ow ; 20EC) 4.83 D207577, 4/9/97, K. Dockter 9

10 Table 2 Physicochemical Properties of Trifluralin Parameter Value Reference UV/vis absorption spectrum 3.0 TOXICOLOGY not available 3.1 Toxicity Profile Acute Toxicity Acute toxicity studies are available for technical trifluralin as well as manufactured products. Technical trifluralin shows low acute toxicity via the oral, dermal and inhalation routes of exposure (toxicity categories IV, III, and IV, respectively). Technical trifluralin showed some irritation in the eye (toxicity category III), but not in the skin (toxicity category IV). In the dermal sensitization assay trifluralin was found to be a dermal sensitizer. Although not required, an acute delayed neurotoxicity study was also performed with negative results. Acute toxicity studies are summarized in Table 3. Table 3 Acute Toxicity Guideline No. Study Type MRID No. Results Acute Oral (Rat) (1985) Acceptable/Guideline Acute Dermal (Rat) (1985) Acceptable/Guideline Acute Inhalation (Rat) (1982) Primary Eye Irritation (Rabbit) Acceptable/guideline (1985) Acceptable/Guideline Primary Skin Irritation (1985) Acceptable/Guideline LD50 > 5000 mg/kg LD50 > 2000 mg/kg LC50 > 4660 mg/m 3, 4.66 mg/l Conjunctival redness at 24hr, cleared by 4 days Not an irritant Toxicity Category IV III IV III IV 10

11 Dermal Sensitization (1985) Acceptable/Guideline Sensitizing agent N/A Subchronic Toxicity The subchronic toxicity data base is complete. Trifluralin was evaluated in rat and mouse oral studies, in rat and rabbit dermal studies, in a rat inhalation study, and in a 6-month oral study in the dog. In the rat subchronic oral toxicity study, minor decreases in overall body weight gains and food consumption in males and females, decreased hemoglobin, alkaline phosphatase, and alanine aminotransferase in the males, and increased absolute and relative (to body) liver weights in males and females were observed at the LOAEL of 391 mg/kg/day. In the mouse subchronic oral toxicity study, no toxicity was observed at the highest dose tested of 375 mg/kg/day. In the dog 6-month oral study, increased absolute and relative (to body) liver weights, liver enlargement, discolored kidneys, decreased red cell indices, increased platelets in males; and increased alkaline phosphatase were observed at the LOAEL of 10 mg/kg/day. A 21-day dermal toxicity study in the rat showed no systemic toxicity at the limit dose of 1,000 mg/kg/day (only dose tested). A 31-day dermal toxicity study in the rat showed no systemic toxicity at 1,000 mg/kg/day; dermal effects included sub-epidermal inflamation and ulcerations at 200 mg/kg/day. A rabbit 21-day dermal toxicity study with a formulation (35.8% trifluralin) also did not show any systemic toxicity at 1,000 mg/kg/day; dermal effects observed at the LOAEL (100 mg/kg/day) included erythema, edema, and/or scaling and fissuring. The systemic NOAELs (1,000 mg/kg/day) observed in the dermal toxicity studies are consistent with the dermal absorption factor of 3%. A 30-day inhalation exposure to rats at 1,000 mg/m 3 resulted in increased methemoglobin and bilirubin, as well as dyspnea and ruffled fur Chronic Toxicity Chronic toxicity to trifluralin was evaluated in the rat, mouse, and dog. Systemic toxicity in rats exposed to 169/219 mg/kg/day (males/females) included decreases in body weight (NOAEL 40/53 mg/kg/day). In a 2-year mouse study no systemic toxicity was observed at the highest dose tested of 118 mg/kg/day. Two 12-month oral toxicity studies were performed in the dog. In one study increased frequency of abnormal stool, decreased body weights and body weight gains, decreased erythrocytes and hemoglobin, and increased thrombocytes in males were observed at the LOAEL of 40 mg/kg/day. In the other study increased absolute liver weights in males were observed at the LOAEL of 3.8 mg/kg/day. 11

12 3.1.4 Developmental / Reproductive Toxicity Developmental toxicity of trifluralin in the rat and rabbit, as well as three 2- generation reproduction studies were evaluated. In all of these studies the NOAEL/LOAELs for parental toxicity were the same as, or lower, than the NOAEL/LOAELs for reproductive and developmental toxicity. In the developmental toxicity studies, maternal toxicity consisted of decreased body weight gain and food consumption, increased liver and spleen weights, increased incidence of resorptions and litters (with total resorptions observed in the rat); and increased abortions, macroscopic changes in the liver and lungs, and decreased food consumption in the rabbit. Reduced ossification of vertebrae and ribs were observed in both the rat and rabbit. In the reproduction studies kidney toxicity (acute renal failure, lesions of renal proximal tubule, increased relative liver weight) and uterine atrophy in females were observed. Offspring toxicity consisted of decreased pup weight including an increase in the number of runts. Decreased fetal, neonatal, and litter viability, and decreased lactation index were also observed Mutagenicity / Genotoxicity Extensive testing showed that trifluralin is neither mutagenic nor genotoxic. There was no evidence of mutagenicity in rat dominant lethal, L5178Y mouse lymphoma, Salmonella typhimurium, Saccharomyces cerevisiae, and DNA repair assays, nor did it induce sister chromatid exchange in Chinese hamster ovary cells. These tests showed that trifluralin does not inhibit the polymerization of microtubules in mammalian cells Carcinogenicity Two carcinogenicity studies by the National Cancer Institute (NCI) revealed hepatocellular carcinomas in both the rat and in the mouse. Subsequent analysis of the trifluralin used in these studies showed high concentrations of nitrosamine [Ndinitroso-di-n-propylamine NDPA] and the carcinomas were attributed to this contaminant. Subsequent carcinogenicity studies were conducted with purified trifluralin. On January 29 and February 27, 1986, the Carcinogenicity Peer Review Committee classified trifluralin as a Group C Carcinogen ( possible human carcinogen), and recommended that, for the purpose of risk characterization, a lowdose extrapolation model be applied to the experimental animal tumor data for quantification of human risk. The upper-bound potency factor (Q 1 *) for trifluralin is 5.8 x 10-3 (mg/kg/day) -1 based on male rat thyroid follicular cell combined adenoma, papillary adenoma, cystadenoma, and carcinoma tumors (converted from animals to humans by use of the 3/4's scaling factor) Immunotoxicity 12

13 Effects suggestive of immunotoxicity include thymic hypoplasia and decreased relative thymus weights in the rabbit developmental toxicity study and rat reproduction study, respectively, and increased spleen weights in a rat developmental toxicity study. No other indications of possible immunotoxicity were observed in the trifluralin data base Metabolism In a rat metabolism study, 14 C-trifluralin was administered by gavage at 300 mg/kg/day to 5 rats/sex on three consecutive days. The objective of this study was to identify the urinary metabolites of trifluralin. There was no sex-dependent effect on metabolic profiles. A minimum of non-conjugated metabolites and an additional conjugated metabolites were present in the urine, but no parent compound was detected. No single metabolite accounted for more than 8-10% of the total urinary radioactivity, and the majority of the metabolites were present at 1-2% of the total urinary radioactivity. Thus, almost all of the metabolites were minor (<5% of the total radioactive dose). Four metabolic pathways were identified as follows; (1) oxidative N- dealkylation of one or both propyl groups and metabolites which were hydroxylated on the propyl side chain; (2) reduction of one or both nitro groups to the corresponding amine; (3) cyclization reactions to give a variety of substituted and unsubstituted benzimidazole metabolites; and (4) conjugation reactions, including acetylation of the reduced nitro groups, sulfate, and glucuronic acid conjugates Kidney Toxicity The kidney appears to be a target organ for trifluralin. These findings are summarized in a peer review of trifluralin (April 11, 1986) and include the following observations; kidney and bladder tumors, decreased kidney weights, increased BUN, increases in total protein, aspartate aminotransferase and lactate dehydrogenase in the urine. Also, protein electrophoresis of urine samples showed α1-globulin and α2- globulin, tubular hyaline casts in the kidneys, minimal cortical tubular epithelial regeneration observed microscopically, and increased incidence of progressive glomerulonephritis. A special rat urinalysis study included the presence of tubular cytoplasmic hyaline droplets, increased total protein, AST and LDH in the urine, albumin α1- globulin and α2-globulin observed by urine electrophoresis, and increased urinary volume. A two-generation reproduction study showed increased incidences of lesions of the renal proximal tubules, decreased corticomedullary mineralization, hyaline droplets in the tubular epithelium, and acute renal failure. A developmental toxicity 13

14 study in the rat demonstrated clear fluid in the renal pelvis, grey hollows on the kidney surface, and enlarged kidney with yellow calculi in the pelvis. In a chronic dog study, minimal to slight multifocal cortical tubular cytoplasmic pigment deposition was noted in the kidneys in males and females. A two-week range-finding study in the rat showed urinary triple phosphates. 3.2 FQPA Considerations Database Summary Relative to FQPA No significant toxicological data deficiency has been identified for trifluralin and the HED HIARC committee concluded that the toxicity data base is adequate for FQPA considerations. Acceptable rabbit and rat developmental toxicity studies were available in addition to two, acceptable, 2-generation reproduction studies in the rat. Also, the HIARC was able to conclude that additional developmental neurotoxicity data will not be required since there were no signs of neurotoxicity in the trifluralin data base Evidence of Quantitative / Qualitative Susceptibility Evidence of increased susceptibility: The HIARC concluded that there is a concern for pre- and/or post-natal toxicity resulting from exposure to trifluralin. There was qualitative evidence of increased susceptibility in the rat developmental toxicity study where fetal developmental effects (increased resorptions and wavy ribs) occurred in the presence of less severe maternal effects (decreases in body weight gain, clinical signs, and changes in organ weights). Also qualitatively, there is an indication of increased sensitivity in the 2-generation reproduction study in the rat in that offspring effects (decreased fetal, neonatal and litter viability) were observed at a dose level where there was less severe maternal toxicity (decreased body weight, body weight gain and food consumption). Degree of Concern Analysis and Residual Uncertainties: The HIARC concluded that concern is low for the qualitative susceptibility seen in the developmental rat study because the dose response was well characterized, the developmental effects were seen in the presence of maternal toxicity, and clear NOAELs/LOAELs were established for maternal and developmental toxicities. There is low concern for the qualitative susceptibility observed in the rat reproduction study since the dose-response was well characterized; there was a clear NOAEL/LOAEL for maternal and developmental toxicities; and the effects were seen at a high-dose level (295/337 mg/kg/day). Offspring viability was not adversely affected in two other 2-generation studies with trifluralin at dose levels up to 100 and 148 mg/kg/day. There are no residual uncertainties for pre- and postnatal toxicities since the doses selected for overall risk assessments will address the concerns seen in these studies. Also, the HIARC concluded that there is not a concern for developmental neurotoxicity resulting from 14

15 exposure to trifluralin since there were no signs of neurotoxicity in the trifluralin data base Special FQPA Safety Factor(s) The HIARC concluded that the FQPA Safety Factor should be removed (equivalent to a 1x Safety Factor) based on a conclusion of no concern for qualitative susceptibility seen. The FQPA Safety Factor recommendation by the HIARC assumed that the exposure databases (food, drinking water, and residential) are complete and the risk assessment for each exposure scenario includes all metabolites and/or degradates of concern, and the assessment does not underestimate the potential risk for infants and children. This criteria has been met in the aggregate risk assessment for trifluralin based on food, drinking water, and residential exposure. Specifically, the food exposure assessment is based on reliable residue, usage, and consumption data (including monitoring data) that does not underestimate actual trifluralin exposure. The drinking water assessment is based on an adequate environmental fate database for parent trifluralin and degradates, upper-bound modeling for parent trifluralin and degradates in water, and Agency estimates of daily drinking water consumption. Also, residential risk assessment for trifluralin is considered an upper-bound assessment since it is based (in general) on maximum use rates, the Agency s Residential SOPs (which tend to the high end), and more recent and reliable exposure data, including Outdoor Residential Exposure Task Force (ORETF) data. 15

16 3.3 Dose Response Assessment Table 4 Toxicology Endpoint Selection Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF* Target MOE Study and Toxicological Effects Acute Dietary (Females years of age) NOAEL = 100 mg/kg/day UF = 100 Acute RfD = 1.0 mg/kg/day FQPA SF = 1 apad = 1.0 mg/kg/day Developmental Toxicity Study - Rat LOAEL = 500 mg/kg/day based on increased total litter resorptions. Acute Dietary No appropriate single dose endpoint was selected (General population, including infants and children) Chronic Dietary (All populations) NOAEL= 2.4 mg/kg/day UF = 100 Chronic RfD = mg/kg/day FQPA SF = 1 cpad = mg/kg/day Chronic Toxicity (capsule) - Dog LOAEL = 40 mg/kg/day based on based on increased frequency of abnormal stool, decreased body weights and body weight gains, and on decreased erythrocytes and hemoglobin and increased thrombocytes in males Short-Term Incidental Oral (1-30 days) NOAEL= 10 mg/kg/day MOE = 100 Two-generation Reproduction Study - Rat LOAEL = 32.5 mg/kg/day based on decreased pup weights in both generations Intermediate- Term Incidental Oral (1-6 months) NOAEL= 10 mg/kg/day MOE = 100 Special Urinalysis Study - Rat LOAEL = 40 mg/kg/day based on based on the presence of tubular cytoplasmic hyaline droplets; increased total protein, AST, and LDH in the urine; albumin α1- globulin and α2-globulin observed by urine electrophoresis; and increased urinary volume 16

17 Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF* Target MOE Study and Toxicological Effects Short-Term Dermal (1 to 30 days) No quantification required since there was no systemic toxicity at the limit dose in the dermal toxicity study. There are no developmental toxicity concerns. The HIARC also recommends that the products containing trifluralin should be labeled as SENSITIZER Intermediate- Term Dermal (1 to 6 months) Oral study NOAEL = 10 mg/kg/day (dermal absorption rate = 3 %) Residential MOE = 100 Occupational MOE = 100 Special Urinalysis Study - Rat LOAEL = 40 mg/kg/day based on based on the presence of tubular cytoplasmic hyaline droplets; increased total protein, AST, and LDH in the urine; albumin α1- globulin and α2-globulin observed by urine electrophoresis; and increased urinary volume Long-Term Dermal (>6 months) Oral study NOAEL= 2.4 mg/kg/day (dermal absorption rate = 3 % when appropriate) Residential MOE = 100 Occupational MOE = 100 Chronic Toxicity (capsule) - Dog LOAEL = 40 mg/kg/day based on based on increased frequency of abnormal stool, decreased body weights and body weight gains, and on decreased erythrocytes and hemoglobin and increased thrombocytes in males Short-Term Inhalation (1 to 30 days) Inhalation study NOAEL= 81 mg/kg/day Residential MOE = 100 Occupational MOE = Day Inhalation Study - Rat LOAEL = 270 mg/kg/day based on increased methemoglobin and bilirubin in females and incidences of dyspnea and ruffled fur in males and females Intermediate- Term Inhalation (1 to 6 months) Oral study NOAEL = 10 mg/kg/day (inhalation absorption rate = 100%) Residential MOE = 100 Occupational MOE = 100 Special Urinalysis Study - Rat LOAEL = 40 mg/kg/day based on based on the presence of tubular cytoplasmic hyaline droplets; increased total protein, AST, and LDH in the urine; albumin α1- globulin and α2-globulin observed by urine electrophoresis; and increased urinary volume 17

18 Exposure Scenario Dose Used in Risk Assessment, UF FQPA SF* Target MOE Study and Toxicological Effects Long-Term Inhalation (>6 months) Oral study NOAEL= 2.4 mg/kg/day (inhalation absorption rate = 100%) Residential MOE = 100 Occupational MOE = 100 Chronic Toxicity (capsule) - Dog LOAEL = 40 mg/kg/day based on based on increased frequency of abnormal stool, decreased body weights and body weight gains, and on decreased erythrocytes and hemoglobin and increased thrombocytes in males Cancer (oral, dermal, inhalation) Q 1 * = 5.8 X 10-3 (mg/kg/day) -1 Group C ( Possible Human Carcinogen) UF = uncertainty factor, FQPA SF = FQPA safety factor, NOAL = 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, NA = Not Applicable 3.4 Endocrine Disruption EPA is required under the FFDCA, as amended by FQPA, to develop a screening program to determine whether certain substances (including all pesticide active and other ingredients) may have an effect in humans that is similar to an effect produced by a naturally occurring estrogen, or other such endocrine effects as the Administrator may designate. Following recommendations of its Endocrine Disruptor and Testing Advisory Committee (EDSTAC), EPA determined that there was a scientific basis for including, as part of the program, the androgen and thyroid hormone systems, in addition to the estrogen hormone system. EPA also adopted EDSTAC s recommendation that the Program include evaluations of potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA and, to the extent that effects in wildlife may help determine whether a substance may have an effect in humans, FFDCA authority to require the wildlife evaluations. As the science develops and resources allow, screening of additional hormone systems may be added to the Endocrine Disruptor Screening Program (EDSP). In the available toxicity studies on trifluralin, the effects seen on the thyroid and kidney may possibly be endocrine related. When additional appropriate screening and/or testing protocols being considered under the Agency s EDSP have been developed, trifluralin may be subjected to further screening and/or testing to better characterize effects related to endocrine disruption. 18

19 4.0 DIETARY / RESIDENTIAL EXPOSURE / RISK 4.1 Usage Summary Agricultural Use Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] is a selective, pre-emergence (to the weed) herbicide registered for the control of annual grasses and certain broadleaf weeds. Trifluralin is one of the dinitroaniline family of herbicides that controls weeds by disrupting the growth process (preventing cell division) during germination, but does not control established weeds. The mode of action (MOA) is described as microtubule assembly inhibition. Trifluralin is registered for use on a wide variety of food and feed crops including soybean, cotton, alfalfa, asparagus, barley, Brassica vegetables, bulb vegetables, celery, citrus fruits, corn (field), cotton, cucurbit vegetables, endive, flax, fruiting vegetables, grapes, hops, legume vegetables, peanuts, peppermint, root and tuber vegetables, rapeseed (canola), safflower, sorghum, spearmint, stone fruits, sugarcane, sunflower, tree nuts, and wheat. Trifluralin end-use products for food and feed crops include emulsifiable concentrates (EC, 36.4, 50.8% ai) and a granular formulation (G, 10% ai). These formulations may be applied using ground or aerial equipment, with the EC formulations being typically applied as aqueous dilutions. The application timing may be dormant, pre-plant, or pre-emergence; with application typically followed by mechanical or water-based soil incorporation. 19

20 Table 5 Registrations for Agricultural Use Trifluralin Food / Feed Registrations Registrant Label EPA Reg. No. Acceptance Date Formulation Class Product Name Dow AgroSciences LLC /20/01 4 lb/gal EC Treflan E.C. Weed and Grass Preventer /4/01 10% G Treflan TR /16/ lb/gal EC Broadstrike + Treflan /30/01 4 lb/gal EC Treflan HFP Industria Prodotti Chimici S.P.A /15/99 5 lb/gal EC Flutrix Five EC /15/99 4 lb/gal EC Flutrix 4 EC ATT /25/99 4 lb/gal EC Flutrix 4 EC Agan Chemical Manufacturers Ltd /24/02 4 lb/gal EC Triflurex HFP Residential / Commercial / Other Use Trifluralin is also registered for weed control on ornamentals, field grown roses, cottonwood trees, turfgrass, christmas trees, non-bearing trees and vines, and rootbarrier applications. Sites of usage include home lawns, home vegetable gardens, ornamental gardens (including planting beds, flowers, shrubs, and trees) and other public/private sites including golf courses, parkland, bike paths, and cemeteries. For residential and other non-agricultural uses, trifluralin is formulated as a granular (G % ai) and an emulsifiable concentrate liquid (EC 43 % ai). For turf, trifluralin is typically applied once in Spring (March/April), prior to crabgrass germination. The predominant formulation for the above uses is granular, and granular is the only formulation used on turf. However, trifluralin may also be applied as a liquid to ornamentals and vegetable gardens Use Estimates Based on data, the Agency estimates that approximately 18,000,000 lbs of trifluralin ai is used per year for agricultural production in the United States. Usage data available for this assessment was limited and could not be used to predict the general trend of overall use, although data provided by the registrant(s) indicates a steady decline in trifluralin use on the two major uses, soybean and cotton. The top 6 20

21 uses include soybean, cotton, wheat, alfalfa, sunflowers, and dry beans/peas, and accounts for 93% of total trifluralin ai applied in the US. The label rate for for agricultural uses is 1 to 2 lbs ai/acre, with a maximum rate of 4 lbs ai/acre on sugarcane. However, the registrant reports that the typical use rate is 1 lb ai/acre, or less. The following are agency estimates of percent crop treated for trifluralin registrations. Other crops are estimated to be less than 10% treated (or lack data for a reliable estimate). Use Estimates: Crop Pounds ai/year % Treated Soybeans 8,200, Cotton 5,000, Sunflowers 800, Durum Wheat 600, Dry Beans 300, Sugarcane 200, Tomatoes 100, Beans, Green 70, Peanuts 60, Safflower 50, Carrots 50, Peas, Green 40, Cabbage 30, Asparagus 20, Peppers 20, Dry Peas 20, Watermelons 20, Cantaloupes 10, Broccoli 8, Collards 3, Cauliflower 3, Greens, Turnip 2, Greens, Mustard 2, Spinach 2, Kale 1, Celery 1, Okra < Radishes < Dietary Exposure / Food Tolerance Summary Trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] tolerances are established under 40 CFR and are expressed in terms of trifluralin per se in/on the raw agricultural commodities (RACs) listed above under Current tolerances range from 0.05 ppm to 2.0 ppm, with most tolerances established at the 21

22 enforcement method s level of quantitation (LOQ) of 0.05 ppm in plant matrices. At this time, tolerances for residues of trifluralin in livestock commodities have not been established. Adequate enforcement methods are available for the determination of trifluralin per se residues in/on plant commodities Tolerance Reassessment In general, most trifluralin commodities will retain their current tolerance level of 0.05 ppm based on data indicating trifluralin per se at less than the level of detection, or LOD, in field trial studies. A proposed, but not final, registration for use on mung bean sprouts (at 2.0 ppm) as a growth regulator will be revoked, as well as a revocation of tolerance for upland cress. Other tolerance revocations and recommendations for new tolerances are made to conform to new guidance for crop group definitions. Of greater significance however, is the tolerance increase from 0.2 ppm to 2.0 ppm for alfalfa hay and the new tolerance of 3.0 ppm for alfalfa forage, based on a revised use pattern allowing application during the growing season. In the residue chemistry chapter of the trifluralin Registration Eligibility Document (RED, 10/94), the data requirements for magnitude of trifluralin residues in livestock were waived (R. Perfetti memo, 2/4/93) based on the low levels of radioactive residues shown in the animal metabolism studies and the low trifluralin exposure estimated for cattle. The Agency concluded that tolerances for trifluralin in fat, meat, meat by-products, and milk were not necessary as there was no expectation for finite residues occurring in animal commodities [40 CFR 180.6(a)(3)]. In the recent alfalfa field trials, maximum trifluralin residues at the labeled 21-day PHI were 2.2 ppm in/on alfalfa forage and 1.6 ppm in/on alfalfa hay, and the highest average field trial (HAFT) residues were 2.0 ppm in/on alfalfa forage and 1.3 ppm in/on alfalfa hay. This estimated exposure to ruminants from alfalfa is significant enough to require additional data to both identify metabolites in meat products and milk, and to predict residue levels for tolerance and risk assessment Residue Data As part of the TRED process, the Agency has re-examined the residue chemistry data submitted by the registrant(s) for trifluralin. These data include studies that support trifluralin s food uses in general, including metabolism in plants and livestock, analytical and multiresidue methods for enforcement, and studies with rotational crops. Studies have also been re-reviewed that support trifluralin commodities specifically, such as crop field trials, processing studies, and storage stability studies. This data is presented below as background to the dietary portion of the risk assessment Metabolism in Plants and Livestock 22

23 Plants: The qualitative nature of trifluralin residues in plants is adequately understood based on field corn and mustard green metabolism studies; supplemented with carrot, cotton, peanut, soybean, and sweet potato metabolism data. The residue of concern in plants is trifluralin per se and the current tolerance expression for plants is considered adequate. Trifluralin was the predominant residue in field corn and mustard greens. Smaller amounts of conjugates C1 (N-[2-Ethyl-1-propyl-5- (trifluoromethyl)-1h-benzimidazol-7-yl]-β-d-glucopyranosylamine) and C2 (N-[2-Ethyl- 1-propyl-5-(trifluoromethyl)-1H-benzimidazol-7-yl]-α-D-glucopyranosylamine) as well as the metabolite TR-4 (α,α,α-trifluoro-5-nitro-n 4,N 4,-dipropyltoluene-3,4-diamine) were identified in corn forage. It was concluded that conjugates in corn plants were converted from nonpolar to polar compounds, and subsequently incorporated into insoluble forms including cell wall components. Livestock: Trifluralin metabolism studies in ruminants and in poultry have been submitted to the Agency and are summarized below. Dietary risk assessment is based, in part, on the results of the ruminant metabolism study, even though the study is considered to be of low quality by current standards. To address this uncertainty in the dietary risk assessment, and to establish the appropriate tolerance expression and tolerance levels in ruminant commodities, the HED Metabolism Assessment Review Committee (2/4/04) concluded that a new metabolism study in ruminants must be submitted as well as a ruminant feeding study at 1x, 3x, and 10x (based on the reassessed tolerance of 3.0 ppm for alfalfa forage the revised maximum dietary exposure for cattle is ~6.0 ppm). In addition, an analytical method for determining trifluralin residues in ruminant fat, meat, meat by-products, and milk must be submitted for Agency review. In the available ruminant metabolism study, two steers were dosed with uniformly ring-labeled [ 14 C]trifluralin at 0.88 ppm (0.15x the revised maximum exposure) and 8.8 ppm (1.5x) in the diet for 5 and 3 days, respectively. In addition, two dairy cows were dosed with uniformly ring-labeled [ 14 C]trifluralin at 1.7 ppm (0.3x) and 17 ppm (2.8x) in the diet for 5 and 3 consecutive days, respectively. For the steer dosed with [ 14 C]trifluralin at levels equivalent to 0.15x the (revised) maximum exposure for 5 days, total radioactive residues (TRR) were <0.001 ppm in muscle, ppm in fat and kidney, and ppm in liver. For the steer dosed with [ 14 C]trifluralin at levels equivalent to 1.5x the (revised) maximum exposure for 3 days, TRR were ppm in muscle, ppm in fat, ppm in kidney, and ppm in liver. Average TRR values in milk were ppm from the cow dosed at 0.3x and ppm in milk from the cow dosed at 2.8x. Extracted 14 C-residues were fractionated and characterized by column chromatography, but residues in milk and tissues were not conclusively identified. Based on thin layer chromatography (TLC) data and comparison to metabolite fractions identified in urine, the following compounds were identified in milk and tissues: 23

24 Liver: Kidney: Fat: Milk: TR-14, TR-5, TR-6, TR-7, and desethyl TR-14 TR-42 or TR-44, and desethyl TR-15 Trifluralin, TR-4, TR-6, and TR-14 Trifluralin, TR-2, TR-6, TR-7 and TR-14 It should be noted that the HED Metabolism Committee concluded (2/4/04) that all trifluralin metabolites, including the above, must be considered toxicologically similar to trifluralin per se. The maximum dietary exposure of trifluralin to poultry is 0.05 ppm based on a diet consisting of 80% field corn grain and 20% soybean. In the poultry metabolism study, laying hens were dosed with uniformly ring labeled [ 14 C]trifluralin at 0.05 ppm (1x) and 0.5 ppm (10x) in the diet for five consecutive days, or at 50 ppm (1,000x) for ten consecutive days. For the 1x dose group, TRR were nondetectable in muscle (<0.003 ppm), skin/fat (<0.003 ppm), and eggs (<0.001 ppm) and ppm in liver. For the 10x dose group, TRR were nondetectable (<0.003 ppm) in muscle, ppm in skin/fat, ppm in liver, and #0.002 ppm in eggs. For the 1,000x dose group, TRR were 0.15 ppm in muscle, 0.47 ppm in skin/fat, 2.49 ppm in liver, and ppm in eggs. 14 C-residues in eggs from the 1,000x dose group plateaued by 8 days. TRR in eggs and tissues from the 1,000x dose group were extracted and fractionated, but attempts at identifying metabolites were unsuccessful. However, given the low dietary exposure of trifluralin residues to poultry, the Agency has concluded that further characterization and identification of the residue in eggs and tissue is not required Residue Analytical Methods Data Collection / Enforcement: The reregistration requirements for residue analytical methods are fulfilled for plant commodities. Adequate methods are available for data collection and enforcement of tolerances for residues of trifluralin per se in/on plant commodities. The Pesticide Analytical Manual (PAM, Vol. II, Section ) lists four GC methods (designated as Methods I, II, III, and A) with electron capture detection (ECD) and a detection limit of ppm, as available for determination of trifluralin per se in/on plant commodities. However, although the Agency previously (2/2/94) waived the requirement for an analytical method for animal commodities, an analytical method for determining trifluralin residues in fat, meat, meat byproducts, and milk is now required in conjunction with the required metabolism and feeding studies. Multiresidue Methods: The FDA PESTDATA database (PAM Vol. I, Appendix II, 1/94) indicates that trifluralin is completely recovered (>80%) using multiresidue method PAM Vol. I Sections 302 (Luke method), 303 (Mills, Onley, Gaither method) and 304 (Mills Method; Protocol E, fatty foods) Field Trial Data ( Magnitude of the Residue ) 24