


EPA ANTIMICROBIALS DIVISION COMPANY NOTICE OF FILING FOR PESTICIDE PETITIONS PUBLISHED IN THE FEDERAL REGISTER  

EPA Antimicrobials Division contact: [Kathryn Montague, (703) 305-1243]

INSTRUCTIONS:  Please utilize this outline in preparing the pesticide petition.  In cases where the outline element does not apply, please insert "NA-Remove" and maintain the outline. Please do not change the margins, font, or format in your pesticide petition. Simply replace the instructions that appear in green, i.e., "[insert company name]," with the information specific to your action.

TEMPLATE:

[Dow Agrosciences]

[0F8875]

	EPA has received a pesticide petition ([0F8875]) from [Dow Agrosciences], [9330 Zionsville Road, Indianapolis, IN 46268] requesting, pursuant to section 408(d) of the Federal Food, Drug, and Cosmetic Act (FFDCA), 21 U.S.C. 346a(d), to amend 40 CFR part 180.350

(Options (pick one)
   
   	1. by establishing a tolerance for residues of


	[nitrapyrin [2-chloro-6-(trichloromethyl) pyridine] and its metabolite, 6-chloropicolinic acid (6-CPA)] in or on the raw agricultural commodity [Cottonseed Crop Subgroup 20C; cotton, gin byproducts; cotton, meal; rice, grain; and rice, straw] at [4.0, 0.6, 6.0, 0.03 and 0.15 respectively] parts per million (ppm).  EPA has determined that the petition contains data or information regarding the elements set forth in section 408 (d)(2) of  FDDCA; however, EPA has not fully evaluated the sufficiency of the submitted data at this time or whether the data supports granting of the petition. Additional data may be needed before EPA rules on the petition.

A. Residue Chemistry

 Plant metabolism. [Studies with [14]C-nitrapyrin have been conducted with multiple crops, including rice, corn, potato, lettuce, and pasture grass.  The majority of nitrapyrin is quickly hydrolyzed to form 6-chloro-picolinic acid (6-CPA) and base labile conjugates of 6-CPA.  Recent studies on potato, lettuce, and pasture grass have resulted in a second minor metabolite which has been proposed as the glucose conjugate of (6-chloropyridin-2-yl) methanol or its isomer, based on analysis by LC/MS.  The conjugate of (6-chloropyridin-2-yl) methanol is present at lower levels than 6-CPA and is rapidly cleaved to form (6-chloropyridin-2-yl) methanol.  Metabolism continues through natural incorporation into plant constituents such as protein, pectin, and lignin.  Confined rotational crop studies demonstrate low residue levels when crops are planted 30 or 124 days after soil application, and the plant residues have been characterized as free and conjugated 6-CPA with no nitrapyrin present in the crops.
  

	2. Analytical method. [Adequate residue analytical methods are available for plant tolerance enforcement. Method 205G881A-1 determines residues of nitrapyrin by extracting with deionized water and 1:1 (v/v) hexane:toluene.  Extracts are then concentrated and passed through a silica gel column before being analyzed by gas chromatography with electron-impact mass spectrometry detection. Method 205G881-B1 determines residues of 6-chloropicolinic acid by extracting with aqueous 0.1 N sodium hydroxide.  Extracts are then acidified and cleaned up by C18 solid phase extraction before being analyzed by liquid chromatography with tandem mass spectrometry detection.  Both methods have been validated with four crop types including iceberg lettuce (high water), whole navel orange fruit (acidic), maize grain (dry) and canola seed (oily).  This method was validated in an ILV which included head lettuce and oilseed rape.]


	3. Magnitude of residues. [DAS has submitted field trial data for nitrapyrin and 6-Chloropicolinic Acid (6-CPA) on cotton and processed commodities, hulls, delinted cottonseed, meal press cake, toasted meal, crude oil, and refined oil and in rice grain, straw and processed commodities, hulls, bran, and white milled polished rice.  Twenty seven (27) trials (11 cotton, and 16 rice) were conducted encompassing Regions 2 (1 cotton trial), 4 (3 cotton and 11 rice trials), 5 (1 rice trial), 6 (1 cotton and 2 rice trials), 8 (3 cotton trials), and 10 (3 cotton and 2 rice trials) growing seasons.  The number and locations of field trials are in accordance with OPPTS Guideline 860.1500.
For cotton, each trial site had two test plots: Plot 1 was untreated and Plot 2 received two broadcast applications of nitrapyrin (GF-4016) at the nominal rate of 0.5 lb ai/A (560 g ai/ha) for a total application at 1.0 lb ai/A (1120 g ai/ha).  The applications occurred at pre-planting up to the first bloom cotton growth stage with re-treatment intervals of 42-85 days.  A 5x rate for determination of processing concentration was included as a separate plot (Plot 3) at one location.
For the cotton trials, RAC samples of cotton seed (all sites) and gin trash (2 sites) were collected at normal harvest.  In the two decline trials, cottonseed samples were harvested at a target 7 and 3 days before normal harvest (DBNH) and 3 and 4 days after normal harvest (DANH).  Bulk samples of cotton seed from the exaggerated-rate plot (trial 5) were collected at normal harvest for processing. 
For rice, each trial site had two test plots: Plot 1 was untreated and Plot 2 received two broadcast applications of nitrapyrin (GF-4016) at the nominal rate of 0.5 lb ai/A (560 g ai/ha) for a total application at 1.0 lb ai/A (1120 g ai/ha).  The applications occurred at pre-planting up to V7 before flood with re-treatment intervals of between 25-35 days.  A 5x rate for determination of processing concentration was included as a separate plot (Plot 3) at one location.
For the rice trials, rice grain and straw were harvested at normal harvest.   In two trials, grain samples were harvested at a target 7 and 3 days before normal harvest (DBNH) and 3 and 7 days after normal harvest (DANH) to monitor decline. Bulk samples of rice grain from the exaggerated-rate plot (trial 14) were collected at normal harvest for processing. 
Cotton and rice samples were analyzed using Method 205G881A-1, an analysis by gas chromatography with mass selective detection to determine nitrapyrin residues.  Additionally, samples were analyzed using Method 205G881B-1, an analysis using liquid chromatography with mass selective detection to determine 6-chloropicolinic acid residues.  The LOQ was set at 0.01 mg/kg (ppm).  The LOD was defined as approximately 30% of the LOQ or 0.003 mg/kg (ppm).  These values are in alignment with empirically-derived LOD and LOQ values determined within the method validation studies.
The results of the cotton study showed that following a total application of 1.0 lb ai/A nitrapyrin residues in samples collected at normal harvest were not detected (ND) in cottonseed and ranged from ND to 0.0185 mg/kg in gin trash.  Residues of 6-CPA ranged from ND to 1.86 mg/kg in cottonseed and from ND to 0.132 mg/kg in gin trash.
Decline trials demonstrated that nitrapyrin residue was ND in cottonseed, while the level of 6-CPA residue remained constant with time.
Following a total application of 5 lb ai/A (i.e., 5x application rate), residues of nitrapyrin were ND and average residues of 6-CPA were 2.91 mg/kg in cottonseed prior to processing.  Nitrapyrin residue was ND in the processed commodities of hulls, delinted cottonseed, meal press cake, toasted meal, or refined oil and was below LOQ in crude oil. Average residues of 6-CPA in hulls, delinted cottonseed, meal press cake, toasted meal, and crude oil were 4.15, 2.93, 4.26, 6.63, and 0.0109 mg/kg, respectively.  Average residues of 6-CPA in refined oil were ND.  These residue data following processing of undelinted cottonseed show that total residue in nitrapyrin equivalents did not concentrate in delinted seed, crude or refined oil and only slightly concentrated in hulls, meal press cake, and toasted meal, with processing factors of <1.5X, < 1.5X and <2.3X, respectively.
The results of the rice study showed that following a total application of 1.0 lb ai/A nitrapyrin residues were ND in rice grain and ranged from ND to 0.00315 mg/kg in rice straw collected at normal harvest. Residues of 6-CPA ranged from ND to 0.00499 mg/kg in rice grain and from ND to 0.0538 mg/kg in straw.
Residue decline data indicated that the level of residues in rice grain over time were ND for nitrapyrin and ranged from ND to below LOQ for 6-CPA.
Following a 5x application (5 lb ai/A), residues of nitrapyrin and 6-CPA in rice grain prior to processing were below LOQ.  Residues of nitrapyrin and 6-CPA in the processing commodities, hulls, bran, and white milled polished rice were also below LOQ, with the exception of residues of 6-CPA in rice hulls at 0.0159 mg/kg.  Since residue levels in rice grain were below LOQ prior to processing, processing factors could not be calculated.

B. Toxicological Profile

There is an extensive toxicological database on both nitrapyrin and its metabolite, 6-CPA.  Across numerous subchronic and chronic toxicity studies, 6-CPA has been demonstrated to be 2-15 fold less toxic than the parent nitrapyrin.  Given the structural similarities between (6-chloropyridin-2-yl) methanol with 6-CPA, and the fact that 6-CPA is less toxic than nitrapyrin, the toxicological database on nitrapyrin would be protective of human health.  The metabolite (6-chloropyridin-2-yl) methanol is not considered a residue of concern.  
	1. Acute toxicity.  [Nitrapyrin has a low order of acute toxicity via oral and dermal routes of exposure (Toxicity Category III), produces mild irritation to the eyes (Toxicity Category II) and very slight irritation to skin (Toxicity Category IV).  For dermal sensitization nitrapyrin is positive in the modified Maguire method.  Due to the waxy physical nature of technical nitrapyrin precludes generating aerosols of appropriate atmospheric concentration to meaningfully assess inhalation toxicity.]

	2. Genotoxicity. [Results of the battery of genotoxicity studies indicate that nitrapyrin is not a genotoxic agent.]

	3. Reproductive and developmental toxicity. [No reproductive or developmental effects were observed in rats and rabbits.]

	4. Subchronic toxicity. [Subchronic Toxicity Mouse: During the study, nitrapyrin was administered orally, via dietary admixture to B6C3F1 mice (10/sex/group) at dose levels of 0, 200, 300, 400 and 600 mg/kg bw/day for the males and 0, 200, 400, 600 and 800 mg/kg bw/day for the females for a period of up to 3 months.  An LOAEL of 300 mg/kg/day in males and 400 mg/kg/day for females was based on increased liver weight hepatocellular hypertrophy and enzyme changes.  The NOAEL for the study was 200 mg/kg/day for males and females.
Dermal Toxicity Study: A 21/28-day dermal toxicity study was conducted in rabbits with dose levels of 0, 100, 500, or 1000 mg/kg/day.  The LOAEL of 1000 mg/kg/day was based on liver weight effects, resulting in an NOAEL of 500 mg/kg/day.
Neurotoxicity Studies: The neurotoxicity of nitrapyrin was investigated in a study which was conducted under GLP conditions and in accordance with the standardised guidelines EPA OPPTS 870.6200 and OECD 424.

During the study groups of 10 male and 10 female F344/DuCrl rats were exposed to 0, 10, 40 or 120 mg test material/kg/day, in the diet, for at least 90 days.  These dose levels corresponded to actual time-weighted average doses of 0, 10.2, 40.6, or 122 mg/kg/day for males, and 0, 10.0, 40.2, or 121 mg/kg/day for females, respectively.  Ten rats/sex/dose were evaluated pre-exposure and during 2, 4, 8, and 13 weeks of exposure using a functional observational battery (FOB), determinations of grip performance, rectal temperature, landing foot splay, and an automated test of motor activity.  Weekly clinical observations, body weights, and food consumption were also evaluated, and ophthalmic examinations were conducted pre- and post-exposure.  At the end of the study, five rats/sex/dose were perfused for histopathologic evaluation of the central and peripheral nervous system, which was conducted on the control and high-dose groups.  The other five rats/sex/dose were grossly examined at necropsy and liver weights were measured.

Treatment with test material did not affect FOB observations, grip performance, rectal temperature, ophthalmic examinations, or clinical observations in males or females at any dose level tested.  At the end of the study, males of the 120 mg/kg/day group had mean in-life body weight and body weight gain that was 9.5 and 18.0 % less than controls, respectively.  Males of the 120 mg/kg/day group also had a slight decrease in feed consumption during the course of the study.  There were no treatment-related effects on body weight or feed consumption in low or mid-dose males or in females from any dose group.  There was a treatment-related increase in landing foot splay in the 120 mg/kg/day dose group at week 13 in males and at weeks 8 and 13 in females.  There also was a treatment-related increase in total motor activity in the 120 mg/kg/day dose group at weeks 8 and 13 in males and at week 13 in females.  Absolute and relative liver weights for animals given 120 mg/kg/day were increased 88.0 and 105 % for males and 75.1 and 75.4 % for females, respectively.

There were no treatment-related gross or histopathologic observations in the central or peripheral nervous systems of rats administered test material.  The NOEL for neuropathology was 120 mg/kg/day, the highest dose level tested.]

	5. Chronic toxicity. [Dog: During the study, nitrapyrin was fed in the diet to beagle dogs (4/sex/group) at dose levels of 0 (control), 0.5, 3, or 15 mg/kg body weight/day, for a period of one year.

Changes resulting from the administration of test material involved primarily the liver and were seen only in the animals, both male and female, given the highest dose level (15 mg/kg/day).  These changes were increased absolute and relative liver weights and diffuse enlargement of hepatocytes.  Serum alkaline phosphatase activity, judged to be associated with the liver enlargement, and cholesterol levels were also increased in the high dose level animals.  No other study parameters were affected by treatment in the high dose level animals; no study parameters were affected by treatment in the middle and low dose level animals.

Under the conditions of the study the NOAEL, for chronic dietary administration of test material, was determined to be 3 mg/kg bw/day.

Mouse: There are two mouse cancer bioassays available for nitrapyrin. In the first study, nitrapyrin was administered to 50 male and 50 female B6C3F1 mice of each sex at 0, 5, 25 or 75 mg/kg/day for 2 years.  A satellite group of 10 mice per sex per dose was included for evaluation after 1 year on test. 

Under the conditions of the study, the NOAEL in this study was 25 mg/kg/day for toxicity, based upon the liver and kidney effects at 75 mg/kg/day.  Dietary administration of 5, 25 or 75 mg test material/kg/ day for 2 years to B6C3F1 mice did not result in an oncogenic response.

In the second mouse cancer bioassay, nitrapyrin was administered to 50 male and 50 female B6C3F1 mice at 0, 125 or 250 mg/kg/day for 2 years.  An interim group of 10 mice/sex/dose was included in the study for evaluation of chronic toxicity after 12 months. 

The maximum tolerated dose was exceeded in males and females given 125 or 250 mg/kg/day, based on treatment-related hepatocellular necrosis and hepatocellular proliferation.  In addition, significant treatment-related depression of body weights occurred in males administered 250 mg/kg/day.  Body weights from this group of mice were decreased 3 - 12 % relative to controls, and body weight gains were decreased 26 - 33 % relative to controls, over much of the dosing period.

Chronic dietary administration of test material caused excessive toxicity of the liver, which included hepatocellular necrosis and increased hepatocellular turnover in both sexes administered 125 or 250 mg/kg/day.  These alterations led to the development of an increased incidence of hepatocellular adenomas and/or carcinomas in males administered 250 mg/kg/day, and females administered 125 or 250 mg/kg/day.  Males and females administered 125 or 250 mg/kg/day also had an increased incidence of hyperplasia, papillomas, and/or squamous cell carcinomas of the nonglandular mucosa of the stomach.
Other primary treatment-related alterations consisted of vacuolation, hyperplasia and hypertrophy of mucosal epithelial cells of the duodenum and jejunum in males and females of both treatment groups.

In conclusion, dietary administration of nitrapyrin for 2 years to B6C3F1 mice resulted in an increased incidence of liver tumors in males given 250 mg/kg/day and females given 125 or 250 mg/kg/day, and non-glandular stomach tumors in in males and females given 125 or 250 mg/kg/day.  Evaluation of the liver mode of action (MoA) in mice determined that the observed hepatocellular effects are mediated by constitutive androstane receptor (CAR) nuclear receptor (NR) activation, which is not considered relevant for human health risk assessment.   

Rat: In the rat study, the two year repeated dose toxicity of nitrapyrin, via the oral route, was investigated in Fischer 344 rats.  An NOAEL of 5 mg/kg/day was based on an LOAEL of 20 mg/kg/day based on decreased body weight gain in males, and increase in renal tumors related to alpha 2μ globulin model which are not relevant to assess cancer risk in humans.

Following evaluation of additional information on mutagenicity, mode of action data, and other possible mechanisms of toxicity, nitrapyrin was reclassified from "Suggestive Evidence of Carcinogenic Potential" to "Not Likely to be Carcinogenic to Humans." (Nitrapyrin: Review of a female mouse liver mechanistic study (MRID 50414401) in support of the Sixth Cancer Assessment Review Committee (CARC) Evaluation. EPA Memorandum.  May 11, 2018.)]

	6. Animal metabolism. [Nitrapyrin is well absorbed regardless of dose or treatment regimen (single gavage dose alone or in repeated dietary feeding).  The primary route of excretion is via the urine (79.56-85.48%) followed by fecal elimination (11.04-13.63%) and levels remaining in tissues are negligible.]

	7. Metabolite toxicology. [Several studies were conducted on the metabolite, 6-chloropicolinic acid (6-CPA).  The oral LD50 for 6-CPA was 2180 mg/kg/day (Norris 1970).  In a 90-day guideline rat study, the NOAEL for 6-CPA was 15 mg/kg/day based upon liver and kidney weight increases (Greenhoe 1961).  The NOAEL for the 6-CPA 90-day mouse study was 700 mg/kg/day for male mice and >1200 mg/kg/day for female mice based on histological changes in renal tubules of male mice (Tollett, et al. 1982).  In a 90-day dog study with 6-CPA, the NOAEL was 66 mg/kg/day for both sexes and there were no treatment-related effects (Copeland, et al. 1963).

Under a two year dietary study for 6-CPA, the NOAEL was 15 mg/kg/day based on degenerative changes in the liver and kidney (McCollister, et al. 1967b). 6-CPA was considered not to be carcinogenic to male and female mice [Cancer Assessment Review Committee Report for Nitrapyrin (2nd Review), May 5, 2000.]

	8. Endocrine disruption. [Nitrapyrin was not among the group of 58 pesticide active ingredients on the initial list to be screened under the EDSP.]

C. Aggregate Exposure

 Dietary exposure. [Acute and chronic dietary risk assessment for nitrapyrin were conducted using the Dietary Exposure Evaluation Model software with the Food Commodity Intake Database (DEEMFCID), Version 4.02. This software uses 2005-2010 food consumption data from the U.S. Department of Agriculture's National Health and Nutrition Examination Survey, What We Eat in America, (NHANES/WWEIA). This assessment evaluates the potential risks due to chronic and acute dietary exposures of the U.S. population subgroups to residues of nitrapyrin and its metabolite, 6-CPA.  These analyses cover the proposed tolerances for Cottonseed Crop Subgroup 20C, including Cotton gin byproducts and Cotton meal; Rice grain; and Rice straw.
      
     i. 	Food. [The current acute and chronic dietary assessment is an unrefined assessment using tolerance level assuming 100% crop treated.  The results of the dietary assessment are considered to be conservative (health protective) risk estimates.  

a)  Acute assessments were conducted to evaluate potential risks due to acute dietary exposures of the U.S. population and sensitive sub-populations to residues of nitrapyrin; estimated exposures were compared to the established acute PAD of 0.16 mg/kg/day based on a NOAEL of 16 mg/kg/day from the neurotoxicity study in rats and an uncertainty factor of 100 (10x for intra-species variation and 10x for inter-species variation).  The FQPA Safety Factor (SF) = 1x; therefore, the acute Population Adjusted Dose (cPAD) = 0.16 mg/kg/day.

b)  Chronic assessments were conducted to evaluate potential risks due to chronic dietary exposures of the U.S. population and sensitive sub-populations to residues of nitrapyrin; estimated exposures were compared to the established chronic reference dose (cRfD) of 0.03 mg/kg/day based on a NOAEL of 3 mg/kg/day from the chronic feeding study in dogs and an uncertainty factor of 100 (10x for intra-species variation and 10x for inter-species variation).  The FQPA Safety Factor (SF) = 1x; therefore, the chronic Population Adjusted Dose (cPAD) = 0.03 mg/kg/day.]


	ii. 	Drinking water.  [Groundwater-sourced drinking water exposure was estimated using the exposure model pesticide water calculator (PWC) v1.5; 12/08/2015. The PWC incorporates the PRZM-GW model. The output values represent pesticide concentrations in a vulnerable groundwater supply that is located directly beneath a rural agricultural field following many years of pesticide application.  The highest EDWCs were found in groundwater which are 76 μg/L for acute exposure and 67 μg/L for chronic exposure using the soil incorporation scenario (Nitrapyrin: Acute and Chronic Aggregate Dietary (Food and Drinking Water) Exposure and Risk Assessment for Section 3 New Uses in/on Bulb Vegetables (Group 3-07), Leafy Vegetables (Group 4-16), Brassica Head and Stem Vegetables (Group 5-16), Citrus Fruits (Group 10-10), and Leaf Petiole Vegetables (Subgroup 22B)]

	2. 	Non-dietary exposure. [Nitrapyrin is not used as a residential use product.]  


D. Cumulative Effects

	[At this time, EPA does not have available data to determine whether nitrapyrin has a common mechanism of toxicity with other substances.  EPA has not made a common mechanism of toxicity finding as to nitrapyrin and any other substances, and nitrapyrin does not appear to produce a toxic metabolite produced by other substances which have tolerances in the U.S.  Therefore, EPA has not assumed that nitrapyrin has a common mechanism of toxicity with other substances and no cumulative assessment is needed.]

E. Safety Determination
	1. U.S. population. [Acute dietary exposure (food and drinking water) to nitrapyrin and its metabolite, 6-CPA from all registered uses and the proposed new uses will utilize 4.84% of the aPAD for the U. S. population.  Values less than 100% of the aPAD are not generally of concern.  
Chronic dietary exposure (food and drinking water) to nitrapyrin and its metabolite, 6-CPA from all registered uses and the proposed new uses will utilize 11.2% of the cPAD for the U. S. population.  Generally, EPA has no concern for exposures below 100% of the cPAD because the chronic PAD represents the level at or below which daily dietary exposures over a lifetime will not pose appreciable risks to human health.
Therefore, based on this risk assessment, is reasonable certainty that no harm will result to any population from aggregate exposure to nitrapyrin and its metabolite, 6-CPA residues from all supported registered uses and the proposed new use.]
	2. Infants and children. [EPA uses a weight of evidence approach in determining what safety factor is appropriate for assessing risks to infants and children.  This approach takes into account the nature and severity of the effects observed in pre- and post-natal studies and other information such as epidemiological data.  The completeness and adequacy of the toxicity database is also considered.  HED has fully evaluated the toxicity database of nitrapyrin with respect to the potential for special sensitivity for infants and children, and concludes that there is no concern for pre-and postnatal susceptibility for infants and children.  The FQPA safety factor has been reduced to 1X because (1) the toxicity database is complete and adequate to characterize the potential pre- and postnatal risk for infants and children; (2) no reproductive or developmental effects were observed in rats and rabbits; and (3) exposure database is adequate and will not underestimate risk. 
The most sensitive, relevant, subgroup with the highest acute food and drinking water exposure is all infants, accounting for 22.0% of the cPAD.  The most sensitive, relevant, subgroup with the highest chronic food and drinking water exposure is all infants, accounting for 10.09% of the aPAD. 
Therefore, based on the completeness and reliability of the toxicity data and the conservative exposure assessment, is reasonable to conclude that no harm will result to infants and children from the aggregate exposure to nitrapyrin and 6-CPA residues from registered and the proposed use.]

F. International Tolerances

	[Nitrapyrin is not currently regulated as a pesticide anywhere outside the United States.  In addition to the tolerances or Maximum Residue Levels (MRLs) for nitrapyrin established by the US EPA, nitrapyrin is also on the Positive List maintained by the Japanese Ministry of Health, Labour and Welfare and Korea's Ministry of Food and Drug Safety.  No international MRLs are planned for nitrapyrin on cotton or rice.]
