EPA REGISTRATION DIVISION COMPAN Y NOTICE OF FILING FOR PESTICIDE

PETITIONS PUBLISHED IN THE FEDERAL REGISTER

EPA Registration Division Contact: Kable Bo Davis; 703-306-0415

BASF Corporation

0E7794

EPA has received a pesticide petitio n (0E7794) from BASF Corporation, 26 Davis Drive, Research Triangle Park, NC 27709 proposing, 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 180.490 by establishing a tolerance fo r residues of imazapic (±)-2-[4,5-dihydro4-methyl-4-(1-methylethyl)-5-oxo-1-H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid in or on the raw agricultural commodity soybean at 0.5 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 tim e or whether the data supports granting of the petition. Additional data may be needed before EPA rules on the petition.

A. Residue Chemistry

1. Plant metabolism. The metabolic pathway of imazapic is understood and is similar in a range of different crops includi ng Bermuda grass, sugarcane and peanuts (a legume), and is comparable to the metabol ic pathway of a structural analogues, imazethapyr and imazamox, in soybean and wheat, respectively. The methyl group at position 5 of the pyridine ring, or in the case of imazethapyr the 5-ethyl group, is hydroxylated, and the hydroxyl group is conjugated to form a glucoside.

2. Analytical method. The proposed analytical met hod for detecting residues of imazapic and the metabolites M715H001 (CL 263,284) and M715H002 (CL 189,215) in soybean seed and processed fractions is an LC-MS/MS method. This validated method has an LOQ of 0.01 mg/kg.

Enforcement methods for analysis of re sidues of imazapic and metabolite M715H001 (CL 263,284) in animal commodities have been previously submitted. The analytical method for analysis in meat and meat by-pr oducts is based on capil lary electrophoreseswith confirmation by LC/MS. The method LOQ is 0.05 mg/kg for meat and meat byproducts. The analytical method for analysis in milk and fat is based on determination by LC/MS with confirmation by LC/MS/MS. Th e method LOQ is 0.01 mg/kg for milk and 0.05 mg/kg for fat. Both methods were su ccessfully validated by an independent laboratory validation.

3. Magnitude of residues. i. Soybeans. Imazapic was applied at labeled rates in 8 field trials. Residues of imazapic ranged from non-detect to 0.25 mg/kg in samples taken 60 days after treatment.2

An additional residue decline trial was conduc ted using labeled rates. Samples were analyzed for imazapic and metabolites M175H001 (CL 263,284) and M715H002 (CL189,215). Residues of imazapic and the metabolite M715H001 (CL 263,284) were nondetect in all samples taken from 40 to 120 days after treatment and residues of the metabolite M715H002 (CL 189,215) were less than the LOQ (<0.01 mg/kg) in all samples taken from 40 to 120 days after treatment.

A processing study was conducte d using soybeans from two trials applied at two times and three times the proposed maximum seasona l application rate. The soybean samples were taken 60 days after treatment and proce ssed into fractions (flake soybean, oil, meal, and toasted meal). The samples were analyzed for imazapic and metabolites M715H001 (CL 263,284) and M715H002 (CL 189,215). Follo wing treatment at three times the proposed maximum application rate, the resi dues of imazapic in soybean grain and all process fractions were <LOQ and residues of metabolites in soybean grain and all process fractions were < LOD. Therefore no processing factors could be determined from this site. Following treatment at tw o times the proposed maximum application rate, residues of the metabolite M715H001 (CL 263,284) were < LOQ in the grain and in all process fractions. Compared to the imazapic level in the grain, residues of the metabolite M715002 (CL 189,215) in the grain were much lowe r. The transfer factors show that imazapic residues do not concentrate in soybean process fractions.

Soybean hulls and aspirated grain fractions were not analyzed in the processing study. However, soybean hulls and aspirated grai n fractions are blended commodities and therefore any imazapic treated soybean hulls and aspirated grain fractions would be blended with untreated soybean hulls and aspi rated grain fractions before being fed to cattle. Based on the limited import of im idazolinone-tolerant soybeans from Brazil and the blended nature of these commodities, any potential imazapic residues would be

diluted and can be considered de minimus

.

ii. Ruminants. A cattle feeding study was conducted with four groups of cows, each group containing three animals, which were orally dosed with imazapic. Milk samples were collected twice daily during dosing and ed ible tissues, muscle, fat, liver and kidney

were collected afte r sacrifice.

All samples were analyzed for imazapic and the hydroxymethyl metabolite M715H001 (CL 263,284). At the lowest feeding level of 67 mg/kg, imazapic residues in milk averaged 0.013 mg/kg and the residues of the metabolite averaged <0.010 mg/kg. Residues of both imazapic and the metabolite in muscle and fat were <0.05 mg/kg (LOQ) for all dosing levels. At 67 mg/kg imazapic re sidues in kidney and liver averaged 0.384 mg/kg and <0.05 mg/kg, respectively, while me tabolite M715H001 resi dues in liver and kidney were <0.05 mg/kg for all dosing levels.

Based on the maximum reasonably balanced diet as defined by the EPA guidance document of 2009, the anticipated dietary burden for dairy cattle due to grass (tolerances for grass forage at 15 mg/kg; grass hay at 30 mg/kg) and peanut meal (tolerance of 0.1 mg/kg) is 27.012 mg/kg. With the addition of soybean meal at 0.54 mg/kg (0.5 mg/kg x3

1.08), the estimated dietary burden for dairy cattle is 27.079 mg/kg, whic h is a negligible increase over the current dietary burden. Ther efore, the existing tole rances for meat and

milk commodities are sufficient to cover th e proposed use on soybeans, and introducing the import tolerance for soybeans will not requi re any changes to the current meat and

milk tolerances.

iii. Poultry. Based on the maximum reasonably ba lance diet as defined by the EPA guidance document of 2009, the anticipated di etary burden for poultry was determined as 0.135 mg/kg diet (without correct ion for dry matter). The only dietary input is from soybean meal with a proposed tolerance of 0.5 mg/kg and processing factor of 1.08.

A metabolism study with 14 C-imazapic was performed in laying hens at feeding levels of 2.1 and 11.4 mg/kg feed. Based on a dietary bur den of 0.135 mg/kg, the feeding levels in the metabolism study were 16 times (2.1/0.135) and 84.4 times (11.4/0.135) the expected dietary burden of imazapic. At the 11.4 mg/kg feeding level, 84.4 times the predicted

feed burden, total 14 C-residues found in eggs and all tissu e, kidney, liver, muscle and skin with fat adhering were <LOQ of 0.01 mg/kg. Therefore, no residues would be expected in poultry commodities due to the import of Cultivance imidazolinone-tolerant soybean.

B. Toxicological Profile

1. Acute toxicity. Imazapic technical is considered to be nontoxic (toxicity category IV) to the rat by the oral route of exposure. In an acute oral toxicity study in

rats, the LD 50 value of imazapic technical was greater than 5,000 milligrams/kilograms body weight (mg/kg bw) for males and females. Th e results from an acute dermal toxicity study in rabbits indicate that imazapic is sli ghtly toxic (toxicity cat egory III) to rabbits by the dermal route of exposure. The dermal LD 50 value of imazapic technical was greater than 2,000 mg/kg bw for both male and female rabbits. Imazapic technical is considered to be nontoxic (toxicity categor y IV) to the rat by th e respiratory route of exposure. The

4-hour LC 50 value was greater than 5.52 mg/L (a nalytical) for both males and females. Imazapic technical was shown to be non-irrita ting to rabbit skin (toxicity category IV) and minimally irritating to the rabbit eye (tox icity category III). Based on the results of a dermal sensitization study, imazapic technical is not considered a sensitizer in guinea pigs.

2. Genotoxicity. Imazapic technical was tested in a battery of in vitro and in vivo genotoxicity assays measuring several diffe rent endpoints of potential genotoxicity.

Collective results from these studies indicate that imazapic does not pose a mutagenic or genotoxic risk.

3. Reproductive and developmental toxicity. i. The developmental toxicity study in Sprague Dawley rats conducted with imazapic technical showed no evidence of teratogenic effects in fetuses and no eviden ce of developmental toxicity. Thus, imazapic is neither a developmental toxicant nor a tera togen in the rat. In the rat developmental toxicity study with imazapic technical, the no observed adverse effect level (NOAEL) for maternal toxicity and developmental toxic ity was 1,000 mg/kg bw/day, the highest dose

tested.4

ii. Results from a developmental toxicity st udy in New Zealand White rabbits with imazapic technical also indicated no evidence of teratogenicity or developmental toxicity. Thus, imazapic technical is neither a developm ental toxicant nor a teratogen in the rabbit. In the rabbit developmental toxicity study, the NOAEL for maternal toxicity was 350 mg/kg bw/day, based on decreased food cons umption and body weight gain at 500 mg/kg bw/day, the next highest dose tested. The NOAEL for developmental toxicity was determined by EPA to be 500 mg/kg bw/day; the excessive mortality in dams at 700 mg/kg bw/day (the highest dose tested) resulted in too few fetuses that were available for

evaluation.

iii. The results from the two-generation reproduc tion toxicity study in rats with imazapic technical support a NOAEL for parental toxi city of 20,000 ppm (or approximately 1,205 mg/kg bw/day in males and 1,484 mg/kg bw/day in females, calculated from food consumption data), the highest concentr ation tested. The NOAEL for growth and development of the offspring is also 20,000 ppm, or approximately 1,205 mg/kg bw/day in males and 1,484 mg/kg bw/day in females. Results from the reproduction study and the developmental toxicity studies conducted with imazapic technical show no increased sensitivity to developing offspring as co mpared to parental animals, because the NOAELs for growth and development of offspr ing were equal to or greater than the NOAELs for parental toxicity.

4. Subchronic toxicity. i. A short-term (21-day) dermal toxicity study in rabbits was conducted with imazapic technical. No derm al irritation or abnormal clinical signs were observed at dose levels up to and including 1,000 mg/kg bw/day (highest dose tested), supporting a NOAEL for dermal irr itation and systemic toxicity of 1,000 mg/kg bw/day.

ii. In a subchronic (13-week) diet ary toxicity study in rats with imazapic technical, no signs of systemic toxicity were noted, supporting a NOAEL of 20,000 ppm (or approximately 1,552 mg/kg/day for males and 1,728 mg/kg/day for females, calculated from food consumption data), the highest c oncentration tested. The requirement for a subchronic dietary toxicity study in non-rodents is satisf ied by the one-year dietary toxicity study in dogs.

5. Chronic toxicity. i. A one-year dietary toxicity study was conducted with imazapic technical in Beagle dogs at dietary concentrations of 0, 5,000, 20,000, and 40,000 ppm. In this study, the NOAEL for syst emic toxicity was less than 5,000 ppm or approximately 158 mg/kg bw/day (137 mg/kg bw/day for males and 180 mg/kg bw/day for females), calculated from food consump tion data, based on a slight skeletal myopathy, characterized by degene ration/necrosis of single fibe rs (minimal severity) and lymphocyte/macrophage infiltration in skeletal muscle, in males and females, and slightly

decreased serum creatinine in females at 5,000 ppm (lowest con centration tested).

The skeletal myopathy observe d at 5,000 ppm was considered of minimal toxicological significance because the limited presence and th e minimal severity of skeletal myopathy5

was evident in only a few fibers out of hundreds evaluated per section per animal. Further, these focal myopathies of minimal se verity were not consis tently diagnosed in all skeletal muscles sites examined per dog (i.e., vastus and abdominal muscles, diaphragm and esophagus). Moreover, no clin ical observations i ndicative of muscle dysfunction were noted in any animal in the study. Finally, although the skeletal myopathy noted at 40,000 ppm (highest conc entration tested) was associated with increases in creatine kinase, aspartate ami notransferase and lactate dehydrogenase, no statistically or biologically significant increases in these serum enzymes were noted during the study period for animals in the 5,000 ppm group. As such, the minimal myopathy diagnosed microscopically at 5,000 ppm was not considered to impair or adversely affect the functional capacity of the affected skeletal muscles.

ii. In a 2-year chronic dietar y oncogenicity and toxicity st udy in rats conducted with imazapic technical, the NOAEL for oncogenicity and chronic systemic toxicity was 20,000 ppm (approximately 1,029 mg/kg bw/day in males, 1,237 mg/kg bw/day in females, calculated from food consumption da ta), the highest con centration tested.

iii. An 18-month chronic dietary oncogenicity and toxicity study in mice with imazapic technical supports a NOAEL for oncogenicity and for chronic systemic toxicity of 7,000 ppm (or approximately 1,134 mg/kg bw/day in males, 1,422 mg/kg bw/day in females, calculated from food consumption data), the highest concen tration tested.

The EPA has classified imazapic as a group E carcinogen (evidence of noncarcinogenicity for humans) based on the ab sence of treatment-related tumors in acceptable carcinogenicity studi es in both rats and mice.

6. Animal metabolism. The rat, goat and hen metabol ism studies indicate that the qualitative nature of the residues of imazap ic in animals is adequately understood.

In the rat metabolism study conducted with radiolabeled imazapic (BAS 715 H, CL 263,222), urinary excretion was the primary elim ination route with 94% to 102% of the radioactivity excreted in the urine. The ma jor component in the urine and feces was the unchanged parent compound.

Lactating goats were orally treated using radiolabeled imazapic. Imazapic was mainly eliminated from the goat through urine and feces . HPLC of goat urin e showed essentially unchanged imazapic, while residues in feces we re comprised of imazapic and low levels of hydroxymethyl metabolites M715H001 (C L 263,284). There were no detectable radiolabeled imazapic-derived residues in m ilk during or after treatment, nor in tissues except kidney 20 hours after the last dose. The 14 C-residue in the hi gh-dose kidney (0.05 mg/kg) was predominantly parent imazapic with low levels of metabolite M715H001 (CL 263,284, 8% TRR, <0.01 mg/kg) and two unknowns, each ≤ 0.02 mg/kg.

A ruminant metabolism study was also c onducted with the radiolabeled imazapic hydroxymethyl metabolite M715H001 (CL 263,284). During treatment, TRR in the daily blood and milk samples were less than 0.01 mg/kg, regardless of the treatment dose6

levels. The TRR in liver, muscle, and omental fat were less than 0.01 mg/kg, regardless of the dose level. Analysis of the kidney extract showed that 9% (<0.01 mg/kg) of the

extractable TRR was CL 263,284.

A metabolism study was performed on hens using radiolabeled imazapic. Total recovery of radioactivity in urine and feces wa s 90.6% and 95.2% for the low and high doses, respectively. Residues in all tissues (liver, kidne y, muscle, skin with adhering fat), blood and eggs were <0.01 mg/kg, the validated detection limit.

A poultry metabolism study was also conduc ted with the radi olabeled imazapic hydroxymethyl metabolite M715H001 (CL 263,284). To tal recovery of radioactivity in

urine and feces was 85.3% and 88.6% for the low and high doses, respectively. Residues in all tissues, liver, kidney, musc le, skin with adhering fat, blood and eggs, were less than 0.01 mg/kg, the validated detection limit.

7. Metabolite toxicology . Metabolism studies in gr ass, peanuts and sugar cane indicate that the only significant metabol ites are the hydroxymethyl resulting from hydroxylation of the methyl group at the 5-position of the pyr idine ring, (±)-2-[4,5- dihydro-4-methyl-4-(1 -methylethyl)-5-oxo-1 H -imidazol-2-yl]-5-hydroxymethyl-3- pyridinecaroxylic acid, and the conjugate re sulting from glucosylation at the hydroxyl group. The hydroxymethyl metabolite was also id entified in minor quantities in the rat metabolism study and in the goat metabolis m study. No additional toxicologically significant metabolites were detected in the plant or animal metabolism studies.

8. Endocrine disruption . Collective organ weight data and histopathological findings from the two-generation rat reproduc tive study, as well as from the subchronic and chronic toxicity studies in three different animal sp ecies, demonstrate no apparent estrogenic effects or treatment-related eff ects of imazapic on the endocrine system.

C. Aggregate Exposure

1. Dietary exposure.

i. Food.

a. Acute Dietary Exposure. An acute diet ary assessment is not necessary because no acute dietary endpoint was se lected based on the absence of an appropriate endpoint attributable to a single dose of imazapic.

b. Chronic Dietary Exposure. A Tier 1 asse ssment of potential chronic dietary exposurewas performed for the proposed import tolerance for use of imazapic on imidazolinonetolerant soybeans. The assessment was done using DEEMTM, incorporating the current tolerances as listed in 40 CFR 180.490 on pea nut, tissues of cattle, sheep, goats, and horses, and milk and the proposed tolerance for imidazolinone-tolerant soybean. For this Tier 1 analysis, tolerance values were us ed for soybean at 0.5 mg/kg; peanut at 0.1 mg/kg; fat of cattle, sheep, goats, and horses at 0.1 mg/kg; kidney of cattle, sheep, goats, and horses at 1.0 mg/kg; meat byproducts, exce pt kidney of cattle, sheep, goats, and7

horses at 0.1 mg/kg; meat of cattle, sheep, goats, and horses at 0.1 mg/kg; and milk at 0.1 mg/kg. Chronic dietary exposures for th e overall U.S. population and population subgroups, including infants and children were compared to the chronic Reference Dose (RfD) of 0.46 mg/kg/day (based on a LOAEL of 137 mg/kg bw/day from the chronic dog toxicology study and a safety f actor of 300). Results of the chronic dietary analyses for all population subgroups examined were at or below 1.0% of the chronic RfD. Exposure estimates for children 1-2 years old, the most highly exposed subpopulation, were only 0.004470 mg/kg bw/day (or 1.0% of the RfD). Th erefore, the results of the chronic dietary assessment demonstrate a reasonable certainty of no harm from the proposed and existing uses of imazapic.

ii. Drinking water . Drinking water residues at an estimated drinking water concentration (EDWC) of 14 μ g/L, i.e., the maximum level estimated by EPA, as reported in the 2001 Federal Register notice (66 FR 66325) were included in a dietary assessment using DEEMTM. A proposed tolerance for an imported commodity would have no impact on the exposure due to dri nking water. The exposur e estimates for all population subgroups when compared to the Rf D of 0.46 mg/kg bw/day were at or below 0.3% (non-nursing infants) of the chronic RfD.

iii. Aggregate dietary. The aggregate exposure estimate due to food and water in the diet for children 1-2 years old, th e most highly exposed subpopulation, was 0.004908 mg/kg bw/day or less than 1.1% of the chronic RfD.

2. Non-dietary exposure . Residential aggregate exposure assessments are not required because the only source of potential im azapic exposure in the U.S. is via the diet and drinking water.

D. Cumulative Effects. Imazapic belongs to the imidazolinone class of compounds a class comprised of a number of registered he rbicides. The herbicidal activity of the

imidazolinones is due to the inhibition of acetohydroxyacid synthase (AHAS), an enzyme only found in plants. AHAS is part of the bi osynthetic pathway leading to the formation

of branched chain amino acids. Animals lack AHAS and this biosynthetic pathway. This

lack of AHAS contributes to the low toxicity of the imidazolinone compounds in animals. We are aware of no information to indicate or suggest that imazapic has any toxic effects

on mammals that would be cumulative with those of any other chemical.

E. Safety Determination

1. U.S. population. Based on the chronic Rf D of 0.46 mg/kg bw/day, the proposed soybean application, in addition to the existing uses, will utilize a maximum of approximately 1.1% of the RfD. Exposure es timates for the genera l U.S. population were only 0.001340 mg/kg/day or 0.29% of the RfD. Exposure estimates for children 1-2 years old, the most highly exposed s ubpopulation, were only 0.004908 mg/kg/day or

≤ 1.1% of the RfD. EPA generally has no conc ern for exposure below 100% of the RfD, which represents the level at or below wh ich daily aggregate dietary exposure over a lifetime will pose no appreciable risks to hum an health. The complete and reliable8

toxicity data, indicating low potential mammalian toxicity, and the conservative chronic exposure assumptions support the conclusion that there is a “reasonable certainty of no harm” from aggregate exposure to imazapic residues.

2. Infants and children . The conservative dietary exposure estimates presented

above will utilize 0.65% of the RfD for all infants and 1.1% of the RfD for children 1-2 years old, the most highly exposed popul ation subgroup. Results from the twogeneration reproduction study in rats and the de velopmental toxicity studies in rabbits

and rats indicate no increased sensitivity to developing offspring when compared to parental toxicity. These results also indi cate that imazapic is neither a developmental toxicant nor a teratogen in either the rat or rabbit. Therefore, an additional safety factor is not warranted, and the RfD of 0.46 mg/kg/day, wh ich utilizes a 300-fold safety factor is appropriate to ensure a reasonable certain ty of no harm to infants and children.

F. International Tolerances

There are no Codex tolerances es tablished for imazapic on soybeans.