Isoxaben Summary of Analytical Chemistry and Residue Data DP Barcode D340895

Page 1 of 38 UNITED STA

TES ENVIRONMENTA L PROTECTION AGENCY WA SHINGTON, D.C. 20460 Office of Chemical Safety and Pollution Prevention MEMORANDUM Date: July

21, 2010 Subject: Is oxaben. Petition for Establishment of Tolerances for Residues of I soxaben in/o n

Grape s and Tree Nuts (including Pistachio) . Summary of Analy tic al Chemistry

and Residue Data. PC Code: 125851 DP Barcode s : D340895, D 341694, D 342083 , D346398, D352226, D354469, D355150, D355805, D368803 Decision No.: 379577, 379578,

398238 File Symbol : 62719 - LIN MRID Nos.: 47140006 - 47140010,

47140012, 47175101 , 47462101, 47492601 , 47825501 Regulatory Action: Section 3 Petition #: 7F7222 Reregistration Case No.: NA Assessment Type: NA CAS # 82558 - 50 - 7 TXR No.: NA 40 CFR 180.xxx (to be determined) From: Dennis McNeilly , Chemist William T. Drew, Chemist Elizabeth Holman, Chemist Risk Assessment Branch I I Health Effects Division (7509P) Through: Douglas Dotson, Ph.D., Chemist

Richard L oranger, Ph.D., Senior Scientist C hristina Swartz, Chief Risk Assessment Branch I I Health Effects Division (7509P) To: Kathry

n V. Montague , PM - 23 Herbicide Branch Registration Division (7505P) This document was originally prepared under contr act by Dynamac Corporation (2275 Research Blvd, Suite 300; Rockville, MD 20850; submitted 12/12/2007). The document has been reviewed by the Health Effects Division (HED) and revised to reflect current Office of Pesticide Programs (OPP) policies.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 2 of 38 Executive Summary Dow AgroSciences has submitted a petition, PP#7F7222, proposing the establishment of tolerances for residues of isoxaben [N - [3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxy

benzamide] in/on the following raw agricultural commodities: Gra pe ................................ ................................ ........... 0.01 ppm Grape, juice ................................ ................................ . 0.01 ppm Grape, raisin ................................ ................................ 0.01 ppm Nut, tree, group 14 ................................ ...................... 0.03 ppm Pistachio ................................ ................................ ...... 0.03 ppm Almond, hulls ................................ .............................. 0.35 ppm The petitioner has also requested a waiver from the requirement for a tolerance for isoxaben residues in or on cattle meat by pr oducts, meat, and milk. Inconjunction with this petition, Dow AgroSciences has submitted a FIFRA Section 3 request to register an end - use product, FN - 3133 Speciality Herbicide , a 75% dry

flowable (DF) formulation of isoxaben with EPA File Sy mbol 62719 - LI

N. The product is proposed for use on grapes and tree nuts (including pistachio) with two soil applications at application rates ranging from 0.5

– 1.0 lb . ai/acre and a maximum of 1.0 lb ai/A per crop per year (harvest to harvest) . No minimum retreatment interval (RTI) was specified on the proposed label . The proposed pre - harvest intervals ( PHI s ) are 60 days for tree nuts, and 165 days for grapes. Is oxaben is a benzamide herbicide (Group 21) used for control of broadleaf weeds. I soxaben reportedly

acts via inhibition of cell wall sy nthesis. The herbicide is currently registered for non food uses on turf, ornamentals, non - bearing fruit and nut trees, and non - bearing vineyards. The petitioner (as the Elanco Products Company ) previously

applied for temp orary

tolerances for residues of isoxaben in/on barley and wheat grain in conjunction with an experimental use permit (PP#5G3216; RCB# 1188, 7/26/85, J. Worthington). At that time, HED recommended in favor of the requested temporary tolerances. For the p urposes of this petition only , the nature of the residue in grapes and tree nuts is adequately

understood based on grape and barley metabolism studies. With respect to future uses, HED concludes that the submitted plant metabolism studies are adequate for uses on cereal grains, grasses, grapes, and tree nuts. For grapes and tree nuts the grape metabolism study is adequate only

for early season uses (i.e., prior to or at bloom). Additional radiolabeled studies would be needed for later season uses on tree nuts or grapes and for any uses on crops other than grains or grasses . A livestock metabolism study has been submitted to support the proposed uses. Only o ne commodity

associated with the proposed uses, almond hulls, is a cattle/dairy cow feed item. Th ere are no poultry

or swine feed items associated with the proposed uses. HED ’s review of this livestock metabolism study indicates that a cattle feeding study , and tolerances for livestock commodities are not needed for the proposed uses currently under consideration. Although the goat metabolism study

identified low percentages of the total radioactive residues in mostIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 3 of 38 matrices, it is adequate for the proposed uses , based on the very low dietary

burden for cattle. Another goat metabolism study with better identification and characterization of the residues will be needed to support any

additional uses of isoxaben that result in significantly higher dietary burdens. HED concludes that residues in milk, ruminant and poultry meat, fat, and meat by products and eggs remain a 40CFR §180.6[a][3] situation ( i.e., no expectation of finite residues in these commodities). The petitioner has proposed a high - performance liquid chromatography with tandem mass spectromectric detection (LC/MS/MS), method GRM 02.26 .S.1 , for the enforcement of tolerances for residues of isoxaben in plant commodities. The limit of quantitation (L OQ) is 0.01 ppm for each commodity . An ILV study was submitted with wheat grain and endive leaves fortified with isoxaben at 0.01 ppm, 0.02 ppm , and 0.10 ppm. Adequate recoveries were obtained for both commodities using the method as written. HED concludes this L C/MS/MS method is adequate for enforcement of the proposed tolerances. Inaddition, e xisting data for the FDA Multiresidue Methods in dicate that isoxaben is completely recovered using mul tiresidue method Section 302. The petitioner submitted crop field trial studies with grape, almond, and pecan to support the proposed uses. All studies were conducted at 1 . 0 x the proposed maximum seas onal rate of 1 lb . ai/ acre . Inthe submitted crop field trial studies, residues of isoxaben were below the L OQ of 0.01 ppm in/on all samples of grape and pecan collected 60 days following application at 1 lb . ai/ acre . Residues of isoxaben were <0.01 - 0.01 5 ppm in/on almond nutmeat samples collected 60 day s posttreatment. Quantifiable residues of isoxaben (up to 0.30 ppm) were observed in/on almond hulls at a PHIof ~60 days. Dow AgroSciences submitted a storage stability study with isoxaben on grapes, ce real grain , cereal straw, and endive leaves. Subsamples of fortified samples were collected at 3 - , 6 - , 12 - , 18 - and 24 - month storage intervals and analy zed for residues of isoxaben. The storage stability data indicate that residues of isoxaben are stable under frozen storage conditions for up to 24 months in/on grapes, cereal grain , and cereal straw, and for up to 12 months in/on endive leaves. No storage stability

data for livestock sample matrices w ere provided by the petitioner. T he dates of sample c ollection, extraction, and HPL C analysis, indicate that all samples were analy zed within 4 - 6 months of sample collection . Therefore, storage stability data are not required . Because grape vines and tree nuts are not normally rotated, no data pertaining t o rotational crops are required to support the proposed uses. There are no Codex, Canadian, or Mexican Maximum Residue L imits (MRL s) established for residues of isoxaben. Regulatory Recommendations and Residue Chemistry Deficienci es HED has examined the residue chemistry database for isoxaben and pending the results of the forthcoming human health assessment, HED recommend s that the requested uses be approved and the supporting tolerances as specified in Table 15 be established.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 4 of 38 860.1300 Nature of the Residue - Plants

 For the purposes of this petition only , the nature of the residue in grapes and tree nuts is adequately

understood based on grape and barley metabolism studies. With respect to future uses, HED concludes that the s ubmitted plant metabolism studies are adequate for uses on cereal grains, grasses, grapes and tree nuts. For grapes and tree fruit the grape metabolism study

is adequate only

for early season uses (i.e., prior to or at bloom) . 860.1300 Nature of the Resi due - Li vestock

 The submitted livestock metabolism study is sufficient for the proposed uses currently under review. However, additional ruminant metabolism data with better identification and characterization of the residue will be needed for any additi onal uses of isoxaben that result in significantly

higher dietary

burdens. 860.1480 Meat, Milk, Poultry , and Eggs

 HED ’s review of the livestock metabolism indicates that a cattle feeding study is not needed for the proposed uses currently under conside ration. However, a cattle feeding study may be needed for any

additional uses of isoxaben that result in significantly higher dietary burdens. 860.1550 Proposed Tolerances

 HED recommends the isoxaben tolerance expression be established as follows: “Tol erances are established for residues of the herbicide isoxaben , including its metabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by measuring only isoxaben [N - [ 3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2, 6 - dimethoxy benzamide] in or on the commodity .  The proposed tolerances for the tree nut group and pistachios should be revised to 0.02 ppm. The commodity

definition for the tree nut group should be revised to “Nut, tree, Group 14.”

 The proposed tolerance for almond hulls should be revised to 0. 40 ppm.  The available processing data indicate that residues of isoxaben do not concentrate in grape juice or raisins; therefore, no tolerances are needed for grape proce ssed commodities. A revised Section F should be submitted with grape juice and raisins removed. Background The chemical structure and nomenclature of isoxaben are presented in Table 1. The phy siochemical properties of the technical grade of isoxaben a re presented in Table. 2. TheIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 5 of 38 chemical names and structures of isoxaben and its transformation products are presented in Appendix I . Table 1. Isoxaben Nomenclature . Compound

O C H 3 N H O O N C H 3 C H3 C H

3 O C H 3

Common name Isoxaben Company experimental name EL - 107 IUPAC name N - [3 - (1 - ethyl - 1 - methylpropyl)isoxazol - 5 - yl ] - 2,6 - dimethoxy benzamide CAS name N - [3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxy benzamide CAS registry

number 82558 - 50 - 7 End - use product (EP) FN - 3133 Speciality Herbicide (75% DF formulation; EPA Reg. No. 627 19 - LIN ) Table 2. Physicochemical Properties of Isoxaben. Parameter Value Reference Melting range 17 3 - 17 6.5 oC MRID 47140001 Density (relative) 0.5 80 g/ml at 22oC MRID 4 7140001 Water solubility 1.42 mg/L at 20oC MRID 47140001 Solvent solubility, at 20oC Acetone 270 g/L Methanol 98 g/L 1 - Octanol 29 g/L Ethyl acetate 88 g/L 1,2 - Dichloroethane 51 g /L Xylene 4 .0 g/L Hexane 0.0 28 g/L MRID 4 7140001

Vapor pressure 1.3 x 10 - 8 Pa at 2 5 oC Email for DowAgroscience s (5/19/10) revising vapor pressure Dissoci ation constant, pK a 9.78 ± 0.06 at 20oC EFSA 1 (May 2006 Draft Report) Octanol/water partition coefficient, Log(KOW ) 3. 83 at 20oC MRID 4 7140001 UV/visible absorption spectrum  max1 = 2 02 nm / 26000 mol - 1 cm- 1  max2 = 2 52 nm / 16500 mol - 1 cm- 1  max3 = 2 75 nm / 20800 mol - 1 cm- 1 EFSA 1 (May 2006 Draft Report) 1 - European Food Safety Authority (EFSA)Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 6 of 38 860.1200 Directions for Use Dow AgroSciences submitted a proposed label for FN - 3133 Specialty Herbicide (EPA File Sy mbol No. 62719 - LIN, label dated 2 /0 9 ). The proposed use s include bearing nut trees and vineyards and nonbearing nut trees and vineyards. The proposed use directions on bearing crops are presented in Table 3 below. Table 3. Summary of Directions for Use of Isoxaben. Applic. Timing, Ty pe, an d Equip. Formulation

[EPA File Symbol No.] Applic.

Rate (lb ai/A) Max. No.

Applic. per Season Max. Seasonal

Applic. Rate (lb ai/A) PHI

(days) Use Directions and

Limitations Grape (American, European, Muscadine) Soil application, Equipment type not speci fied 75% DF

[62719 - LIN] 0.50 - 1.0 2 1.0 per crop season (harvest to harvest) 165 Not to be used in NY.

Application is to be made prior to germination of target weeds or immediately after cultivation. Application is to be made in a minimum of 10 gal/A . Al mo nd; Beech Nut; Brazil Nut; Butternut; Cashew; Chestnut; Chinquapin; Filbert (Hazelnut); Hickory Nut;

Macadamia Nut (Bush Nut); Pecan; Pistachio; and Walnut ( Black, En glish/Persian) Soil application, Equipment type not specified 75% DF

[62719 - LIN] 0.50 - 1 .0 NS 1.0 per crop season (harvest to harvest) 60 Not to be used in NY.

Application is to be made prior to germination of target weeds or immediately after cultivation. Application is to be made in a minimum of 10 gal/A. The product is not to be applie d through any ty pe of irrigation system or t o crops grown in containers. A restricted entry interval of 12 hours has been established on the label. Conclusions . The proposed use directions are adequate to allow evaluation of the crop field trial data su bmitted with this petition. T he proposed use directions represent maximum seasonal rates

~ 1 x those used in the crop field trials. The available crop field trial data support a maximum seasonal rate of 1 lb a ctive i ngredient/A. 860.1300 Nature of the Res idue - Plants DER Reference s : 47140006.der.doc (Barley)

47175101.der.doc (Grape) Residue Chemistry Memo PP#5G3216, 5/17/85, J. Worthington Inconjunction with the temporary tolerance petition reviewed by the Agency

in 1985 (PP#5G3216, J. Worthington, 5/17/85), the petitioner submitted metabolism data for barley and wheat, reflecting use of [ 14 C]isoxaben labeled at the carbonyl carbon and in the isoxazole ring. Winter wheat and barley

plants were grown in small outdoor plots treated at 81 - 324 g ai/A (0.18 - 0.71 lb ai/A) with labeled isoxaben. A greenhouse experiment reflecting 162 g ai/A (0.36 lbIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 7 of 38 ai/A) was also reported. Grain and straw samples were collected from all of the treated plots about 100 days after planting. The following four metabolites , comprising 33.1% and 14.4% of the activity in wheat and barley straw, respectively , were identified: (1) and (2) N - [3 - (1 - ethyl - 2 - hydroxy- 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxy benzamide (isoxaben - 2 - hydroxy ) and its diastereomer; (3) N - [3 - (1 - ethyl - 3 - hydroxy- l - methylpropyl) - 5 - isoxazolyl) - 2,6 - dimethoxy benzamide (isoxaben - 3 - hydroxy ); and (4) 2,6 - dimethoxy

benzamide. The pattern of residue s in wheat and barley grain was similar except that more extensive degradation of the radioactivity was shown. About 5% of the recovered activity

was shown to be parent. Only about 50% of the activity present in the grain was solubilized. The same four metabolites were also detected in the grain samples; however, quantification of the lower residue levels in the grain samples was more difficult. HED concluded that the fate of isoxaben in wheat grain was adequately delineated for the purpose of the proposed temporary tolerances, considering the fact that grazing, foraging, and cutting crops grown in treated areas was to be prohibited. I soxaben was determined to be the residue of concern. It was also concluded that for any future submission involving feed use of treated foliage, characterization of a greater portion of the activity in forage and straw might be require d. Barley (Note: This is a new study , not the study reviewed by

HED in 1985.) Dow AgroSciences submitted a study investigating the metabolism of [isoxazole - 5 - 14 C]isoxaben (specific activity

5.8 mCi/mmol) and [phenyl 14 C]isoxaben (specific activity 17.3 9 mCi/mmol) in barley . Each radiolabeled test substance was formulated with blank suspension concentrate ( SC ) formulation, diluted with water, and applied as a single foliar application at 0.178 lb ai/A (200 g ai/ha) to barley

at the BBCH 13 growth stage (3 unfolded leaves) grown outdoors in tubs. The application rate used in the study is ~0. 18 x the proposed maximum seasonal rate of 1 lb ai/A for grapes and tree nuts and ~0. 18 x the maximum rates used in the crop field trials. Immature plant samples were taken 3 hours after application (0 days after treatment; 0 - DAT), 7 DAT, 14 DAT, and 28 DAT. Samples of mature barley grain, straw, and chaff were harvested at 87 DAT and allowed to air dry . Total radioactive residues (TRR) were generally slightly highe r in isoxazole - label samples than in phenyl - label samples, and TRR decreased (both labels) with later sampling intervals. TRR in mature barley

matrices were initially

determined by

combustion/L SC. However, TRR were calculated in immature and mature barley matrices by summing radioactivity

in extractable and nonextractable fractions, and these values were used for all calculations. Calculated TRR for isoxazole - label barley

and for phenyl - label barley matrices are provided in Table 4.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 8 of 38 TABLE 4 Total Radio active Residues (TRR) in Barley at 0. 18 X Application Rate. 1 Matrix Application rate (lb ai/A) PHI (days) Isoxazole label Phenyl label

ppm ppm Immature plant 0.178 0 5.731 4.718 7 3.129 1.307 14 0.376 0.341 28 0.084 0.052 Grain 87 0.019 (0 .019) 0.012 (0.011) Straw 0.281 (0.298) 0.222 (0.213) Chaff 0.458 (0.475) 0.279 (0.295) 1 TRR calculated by summing radioactivity in extractable and nonextractable fractions; TRR in mature grain, straw and chaff determined by combustion/L SC are rep orted in parentheses. Solvent extraction with acetonitrile (ACN) and ACN/water released the majority (92.3 - 99.9% TRR) of the radioactivity (with highest levels in the ACN extract) from immature plants from both labels; nonextractable residues accounted fo r 0.1 - 7.7% TRR (0.003 - 0.016 ppm) in immature barley . Solvent extraction with ACN and ACN/water released lower levels of radioactivity (with highest levels in the ACN/water extract) from mature barley matrices: 63.2 - 66.6% TRR from grain, 73.3 - 75.3% TRR from chaff, and 73.0 - 75.4% TRR from straw. Additional radioactivity (19.2 - 21.2% TRR) was released from barley straw with acid hydroly sis at reflux. Nonextractable residues accounted for 33.3 - 36.8% TRR (0.004 - 0.007 ppm) in grain, 4.5 - 4.6% TRR (0.01 - 0.013 pp m) in straw, and 24.7 - 26.6% TRR (0.069 - 0.122 ppm) in chaff. Nonextractable residues in chaff were not further investigated because chaff represents a small component of barley straw. The extraction/hydrolysis procedures adequately extracted the majority of residues from barley matrices. Because TRR in immature barley were determined by

summing radioactivity

in extractable and nonextractable residues, accountabilities for immature plants were 100%. Accountabilities for mature barley grain, straw, and cha ff were 94.6 - 109.1% (based on comparison of combustion/L SC and calculated TRR values). Residues were identified and confirmed by thin layer chromatography ( TLC ) and HPL C, except for those in the ACN extract of grain samples and the enzy me/acid hydrolysate s (with low levels) which were characterized by TLC only . The metabolic pattern was similar in isoxazole - and phenyl - label barley matrices. The major and only residue identified in 0 - , 7 - and 14 - DAT immature barley was the parent isoxaben, accounting f

or 85.1 - 94.8% TRR (0.298 - 5.367 ppm). I soxaben was also the major residue identified in 28 - DAT immature barley , at 88.5 - 89.3% TRR (0.046 - 0.075 ppm), and mature barley straw, at 25.9 - 29.2% TRR (0.057 - 0.082 ppm). I soxaben was identified as a minor residue i n mature barley

grain, at 5.8 - 6.7% TRR (0.001 ppm), and chaff, at 4.7 - 5.2% TRR (0.013 - 0.024 ppm). Major residues identified in mature barley grain, straw, and chaff were Metabolite II (isoxaben - 2 - hydroxy ) and Metabolite IV (isoxaben - 1 - hydroxy ). Metaboli te I I accounted for 15.8% TRR (0.002 - 0.003 ppm) in grain, 12.2 - 16.1% TRR (0.045 - 0.056 ppm) in chaff, and 13.9 - 16.2% TRR (0.036 - 0.039 ppm) in straw; Metabolite IV accounted for 9.5 - 11.7% TRR (0.001 - 0.002 ppm) in grain, 14.0 - 15.4% TRR (0.043 - 0.064 ppm) in ch aff, and 11.6 - 11.7% TRR (0.026 - 0.033 ppm) inIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 9 of 38 straw. Metabolites II and IV were identified as minor residues in immature 28 - DAT barley , each at <3% TRR ( ≤0.002 ppm). An additional minor residue identified was Metabolite III (isoxaben - 3 - hydroxy ), which acc ounted for <5% TRR (0.001 ppm) in mature barley grain, <7% TRR ( ≤0.018 ppm) in straw, and <5% TRR ( ≤0.021 ppm) in chaff. Metabolite I

(2,6 - dimethoxy

benzoic acid) was only

identified in phenyl - label straw at 0.9% TRR (0.002 ppm) and was suspected by the pe titioner to be an artifact of the acid hydrolysis procedure. This was confirmed by the detection of Metabolite I and an unknown in the phenyl label isoxaben standard acid hydroly zed (as a control) under the same conditions. Polar metabolites were a maj or residue characterized in barley matrices; polar metabolites accounted for 10.7 - 13.5% TRR (0.007 - 0.009 ppm) in 28 - DAT immature barley and 27.5 - 27.9% TRR (0.003 - 0.005 ppm) in mature barley grain, 12.5 - 13.5% TRR (0.030 - 0.035 ppm) in straw, and 37.3% TRR (0 .104 - 0.171 ppm) in chaff. Other unknown residues accounted for 2.7% TRR (0.006 ppm) in phenyl - label straw. The polar compounds were determined to consist of multiple components using HPL C analysis. Polar metabolites in the ACN/water extracts of straw we re subjected to enzy

me and subsequent acid hydrolysis to release conjugated residues. Enzy me hydrolysis did not significantly change the polar fraction pattern, but acid hydrolysis after the enzy me hydrolysis released small amounts of isoxaben, and Metabo lites I I, I II and IV. TABLE 5. Summary of Characterization and Identification of Radioactive Residues in Barley Grain,

Straw, and Chaff Following Application of [Isoxazole - 5 - 14 C] Isoxaben at 0.178 lb ai/A. Compound Barley Grain Barley Straw Barley Chaf f TRR = 0.019 ppm TRR = 0.281 ppm TRR = 0.458 ppm % TRR ppm % TRR ppm % TRR ppm Isoxaben 5.8 0.0011 29.2 0.082 5.2 0.024 Metabolite II 15.8 0.0030 13.9 0.039 12.2 0.056 Metabolite III 3.4 0.0007 6.4 0.018 4.6 0.021 Metabolite IV 9.5 0.0018 11.7 0.0 33 14.0 0.064 Polar compounds 27.9 0.0053 12.5 0.035 37.3 0.171 Total identified 34.5 0.0066 61.2 0.172 36.0 0.165 Total characterized 27.9 0.0053 12.5 0.035 37.3 0.171 Total extractable 63.2 0.012 94.7 0.266 73.3 0.336 Unextractable (PES) 1 36.8 0.007 4.6 0.013 26.6 0.122 Accountability

2 100.0 93.6 96.4 1 Residues remaining after exhaustive extractions. 2 Accountability = (Total extractable + Total unextractable)/(TRR from combustion analysis) x 100. TABLE 6. Summary of Characterization and Ident ification of Radioactive Residues in Barley Grain,

Straw, and Chaff Following Application of [Phenyl 14 C]Isoxaben at 0.178 lb ai/A. Compound Barley Grain Barley Straw Barley Chaff TRR = 0.012 ppm TRR = 0.222 ppm TRR = 0.279 ppm % TRR ppm % TRR Ppm % TRR ppm Isoxaben 6.7 0.0008 25.9 0.057 4.7 0.013 Metabolite I -- -- 0.9 0.002 -- -- Metabolite II 15.8 0.0019 16.2 0.036 16.1 0.045Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 10 of 38 TABLE 6. Summary of Characterization and Ident ification of Radioactive Residues in Barley Grain,

Straw, and Chaff Following Application of [Phenyl 14 C]Isoxaben at 0.178 lb ai/A. Compound Barley Grain Barley Straw Barley Chaff TRR = 0.012 ppm TRR = 0.222 ppm TRR = 0.279 ppm % TRR ppm % TRR Ppm % TRR ppm Metabolite III 4.4 0.0005 5.4 0.012 2.2 0.006 Metabolite IV 11.7 0.0014 11.6 0.026 15.4 0.043 Polar compounds 27.5 0. 0033 13.5 0.030 37.3 0.104 Other Unknowns -- -- 2.7 0.006 -- -- Total identified 38.6 0.0046 60.0 0.133 38.4 0.107 Total characterized 27.5 0.0033 16.2 0.036 37.3 0.104 Total extractable 66.6 0.0080 94.2 0.209 75.3 0.210 Unextractable (PES) 1 33.3 0.00 40 4.5 0.010 24.7 0.069 Accountability

2 109.1 102.8 94.6 1 Residues remaining after exhaustive extractions. 2 Accountability = (Total extractable + Total unextractable)/(TRR from combustion analysis) x 100. The petitioner did not provide any dates of sample combustion, extraction, or analysis. Based on the experimental completion date, samples may have been stored for up to ~15 months prior to completion of analysis. Extraction and analysis of additional 0 - DAT plant samples following storage at < - 16o C at the end of the experimental stage of the study demonstrated that the parent isoxaben (only

residue found in 0 - DAT barley ) was stable in frozen barley plants for the study duration. Other available s torage stability data for grapes, endive, and cereal grains indicate that the p arent compound is stable in frozen storage for up to two years. Based on the submitted barley metabolism studies, the petitioner proposed that isoxaben is significantly

metabolized in summer barley . Hydroxylation of the aliphat ic side chain of the intact molecule is the major route of metabolism in barley ; cleavage of the amide bond was not observed. I soxaben and metabolites were also present as acid - hydroly zable conjugates. I soxaben and metabolites, as well as conjugates/pola r compounds, were partly incorporated into the nonextractable residues of barley matrices. Grape Dow AgroSciences submitted a study investigating the metabolism of [isoxazole - 5 - 14 C]isoxaben (specific activity

9.01 μCi/mg) and [phenyl 14 C]isoxaben (specif ic activity 8.55 μCi/mg) in grape. The radiolabeled test substances, dissolved in ACN and water, were applied as a single broadcast application to the soil surrounding grape vines at the dormant stage at 1.97 lb ai/A for the isoxazole label and 1.79 lb ai /A for the phenyl label. The application rates used in the study are ~ 2 x the proposed maximum seasonal rate of 1 lb ai/A, and ~2x the individual application rate used in the grape crop field trials. Samples of grape fruit and foliage were harvested from each plot at maturity , 165 days after application. The petitioner reported that the crop did not show any sign of phy

totoxicity during the course of the study . TRR were below the L OQ (<0.008 ppm) in/on grape fruit harvested 165 days following soil treatment with isoxazole - or phenyl - labeled isoxaben at 1.79 or 1.97 lb ai/A. TRR were 0.304 and 0.288 ppm in grape foliage following soil treatment with isoxazole - or phenyl - labeledIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 11 of 38 isoxaben, respectively . Because TRR were <LOQ in/on grape fruit, no attempt s were made to characterize or identify

metabolites in the fruit. TABLE 7. Total Radioactive Residues (TRR) in Grape Matrices. Matrix No. of

applications PHI

(days) Application rate

(lb ai/A) Isoxazole label Phenyl label

ppm p pm Grape, fruit 1 165 1.79 - 1.97 <LOQ (0.0057) 1 <LOQ (0.0031) 1 Grape, foliage 1 165 0.304 0.288 1 The LSC LOQ was 0.008 ppm for grape fruit. Extraction with ACN and water released the majority of the radioactivity

from grape foliage samples, 69% TRR for the isoxazole label and 75% TRR for the phenyl label (average of six subsamples for each). Additional residues (10 - 14% TRR) were released from the grape foliage with acid hydrolysis. Nonextractable residues in foliage were 11 - 14% TRR (0.032 - 0.041 ppm) following acid hydrolys is. All extraction results were normalized to 100% for further calculations; however, extraction recoveries were reported to be 76 - 97% (average of 85.1% for the isoxazole label and 92.6% for the phenyl label). Residues were identified by comparison of HPL C retention times with those of known standards. No confirmatory

analyses were performed; therefore, all metabolite identifications are considered to be tentative. The petitioner reported the dates of sample collection, combustion, extraction, and ini tial HPL C analysis; however, the dates of final analyses were not provided. Initial HPL C analyses were conducted within 4 months of sample collection. HPL C analysis yielded five distinct metabolite components plus a region of polar metabolites. The parent, isoxaben, was not identified in any sample. A metabolite eluting at ~21.2 min, tentatively

identified as 2 - hydroxy- 6 - methoxy- benzamide, accounted for 2.9% TRR in phenyl label foliage. A metabolite with a similar retention time was characterized in isoxazole - label samples, accounting for 4.7% TRR. The major metabolite detected (retention time of ~18.4 min) accounted for 27.8% TRR (0.084 ppm) in isoxazole - label foliage and 23.9% TRR (0.069 ppm) in phenyl - label foliage. The metabolite was isolated from the aqueous phase of extractable foliage residues (both labels) and purified by partitioning and solid - phase extraction (SPE). Attempts to identify the isolated metabolite by L C/MS/MS were unsuccessful; however, the petitioner characterized the residue as aqueous - soluble, polar, and containing both sides of the benzamide bridge (the residue was observed in foliage from both labels). TABLE 8. Distribution of the Parent and the Metabolites in Grape Foliage Following Application of 14 C - Isoxaben at 1.79 - 1.97 lb ai/A. Metabolite Fraction Isoxazole label Phenyl label TRR = 0.304 ppm TRR = 0.288 ppm %TRR ppm %TRR ppm ACN:H 2 O 1 75 0.229 69 0.198 Neutral Organic Fraction 2 19 0.057 16 0.045 2 - OH - 6 - OMe benzamide (Rt ~21.2 min) 4.7 3 0.014 3 2.9 0.008 Polars (Rt ≤ 5 min) 1.6 0.005 1.6 0.005 Peak Rt ~19.0 min 2.1 0.006 <0.1 0.002 Acidic Organic Fraction 2 5 0.015 4 0.011 Polars (Rt ≤ 5 min) 0.7 0.002 1.5 0.004Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 12 of 38 TABLE 8. Distribution of the Parent and the Metabolites in Grape Foliage Following Application of 14 C - Isoxaben at 1.79 - 1.97 lb ai/A. Metabolite Fraction Isoxazole label Phenyl label TRR = 0.304 ppm TRR = 0.288 ppm %TRR ppm %TRR ppm Peak Rt ~27.0 min 3.7 0.011 2.4 0.007 Aqueous Fraction 2 52 0.157 49 0.142 P olars (Rt ≤ 5 min) -- -- 17.4 0.050 Peak Rt ~16.5 min 5.1 0.016 4.1 0.012 Peak Rt ~18.4 min 27.8 0.084 23.9 0.069 Peak Rt ~19.0 min 11.3 0.034 4.4 0.013 Post - extracted tissue 29 2 0.087 2 32 4 0.092 Acid hydrolysate 10 2 0.031 2 14 0.039 Organic fraction 10 5 0.030 6 8 0.023 6 Aqueous fraction 4 5 0.012 6 6 0.017 6 Unextractable 11 2 0.032 14 0.041 1 Average of 6 subsamples. 2 Average of 3 subsamples. 3 14 C - 2 - OH - 6 - OMe - benzamide would not be present in isoxazole - label samples, as this compound doe s not contain the isoxazole ring. 4 Average of 5 subsamples. 5 Obtained from a single sample; actual result for acid hydrolysis for this sample was 14 %TRR (0.043 ppm). 6 ppm values were calculated by the study reviewer. TABLE 9. Summary of Characterization and Identification of Radioactive Residues in Grape Foliage

Following Application of 14 C - Isoxaben at 1.79 - 1.97 lb ai/A. Compound Isoxazole label Phenyl label TRR = 0.304 ppm TRR = 0.288 ppm % TRR ppm % TRR ppm Isoxaben -- -- -- -- 2 - OH - 6 - OM e benzamide (RT ~21.2 min) (RT= - retention time) -- -- 2.9 0.008 Peak RT ~21.2 min 1 4.7 0.014 -- -- Polars (RT ≤ 5 min) 2.3 0.007 20.5 0.059 Peak RT ~16.5 min 5.1 0.016 4.1 0.012 Peak RT ~18.4 min 27.8 0.084 23.9 0.069 Peak RT ~19.0 min (neutral organic) 2 2.1 0.006 <0.1 0.002 Peak RT ~19.0 min (aqueous) 2 11.3 0.034 4.4 0.013 Peak RT ~27 min 3.7 0.011 2.4 0.00 7 Acid hydrolysate 10 0.031 14 0.039 Total identified 0 0 2.9 0.008 Total characterized 67 0.203 69.8 0.201 Total extractable 85 0.260 83 0.237 Unextractable (PES) 3 11 0.032 14 0.041 Accountability

4 96.1 96.5 1 The petitioner concluded that this pe ak corresponded to 2 - OH - 6 - OMe benzamide. Because the metabolite identified does not contain the isoxazole ring, it could not have been present in the isoxazole - label sample. 2 While the retention times are similar for these metabolites, it is expected that they are different as they occur in different fractions. 3 Residues remaining after exhaustive extractions. 4 Accountability = (Total extractable + Total unextractable)/(TRR from combustion analysis) * 100.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 13 of 38 Polar unknowns accounted for 20.5% TRR (0. 059 ppm) in phenyl - label foliage, but only 2.3% TRR in the isoxazole - label samples. Other metabolites characterized by their partitioning characteristics and HPLC retention times accounted for ≤5% TRR in grape foliage (both labels), except for one unknown peak (retention time ~19 mins) in isoxazole - label foliage which accounted for 11% TRR (0.034 ppm). The petitioner provided example chromatograms which included information indicating that additional metabolites may have been identified in grape foliage fractions: ( 1 ) 1 - hydroxy isoxaben in the organic phases of isoxazole - and phenyl - label foliage; ( 2 ) 5 - isoxazolamine in the organic phases of isoxazole - and phenyl - label foliage (however, this metabolite would not be present in phenyl - label samples because it does not contain the phenyl rin g); and , ( 3 ) 3 - hydroxy isoxaben in the organic phase of the acid hydrolysates of isoxazole - and phenyl - label foliage. These metabolite identifications were not mentioned in the petitioner’s summary discussion or tables, and were only

reported in the listi ng of chromatographic data with the representative chromatograms. However, these metabolites were included in the petitioner’s proposed metabolic pathway

for grapes. In sufficient information was provided with the representative chromatograms to allow the study reviewer to verify

the results reported for the metabolite and peak fractions. The petitioner reported peak results in terms of %HPL C; however, as the petitioner did not identify the individual fraction that was injected for each representative chromatogram, the study reviewer could not convert these results to %TRR or ppm values. Based on the submitted grape metabolism study , the petitioner proposed that following application of isoxaben to the soil, low levels of radioactivity are taken up by

the grape vine roots, and even lower levels of radioactivity are translocated into the edible fruit. The metabolism of isoxaben in grape leaves appears to proceed through hydroxylation of the methylpropyl group. Ultimately , the soil degradation/plant metabo lism proceeds to low level, multiple, polar components, presumably through cleavage of the benzamide bridge. Conclusions . For the purposes of this petition only , the nature of the residue in grapes and tree nuts is adequately

understood based on grape and barley metabolism studies. With respect to future uses, HED concludes that the submitted plant metabolism studies are adequate for uses on cereal grains, grasses, grapes and tree nuts. For grapes and tree fruit the grape metabolism study is adequate only

for early season uses (i.e., prior to or at bloom). Additional radiolabeled studies would be needed for later season uses on tree nuts or grapes and for any uses on other crops not mentioned above. For the grape study , the application rate of the te st substance was not sufficient to allow adequate characterization/identification of the residues in grapes, and very limited information and data were provided in the study report to allow the study

reviewer to verify

the study results. The following add itional deficiencies were identified:  individual sample extracts for which representative chromatograms were provided were not identified;  chromatographic data in figures were not reported in terms of % TRR;  metabolites were assigned to peaks in chromatograms in the figures but these results were not transferred to the petitioner’s summary of results;Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 14 of 38  metabolites were identified in fractions incorrectly (e.g., 2 - hydroxy- 6 - methoxybenzamide was “identified” in grape foliage treated with isoxazole - label isoxa ben; however, this metabolite could not possibly be identified radio - chromatographically in this fraction because 2 - hydroxy- 6 - methoxy- benzamide does not contain the isoxazole ring);  metabolite identifications were not confirmed using a second chromatograph ic method;  dates of final sample/extract analysis were not reported for any sample;  d ata were not submitted to support extract stability during storage. For the barley

metabolism study , submission of additional storage stability data/information is not re quired ; since storage stability data indicate that the parent compound is stable in frozen storage for up to 2 years (samples may have been stored for up to ~15 months) . The petitioner should have provide d the dates of sample collection, combustion, extra ction, and analysis for each sample. 860.1300 Nature of the Residue - Livestock DER Reference: 47825501.der.doc ( Goat) A livestock metabolism study was recently

submitted for this petition. The only livestock feedstuff associated with the proposed use is almond hulls. Almond hulls are not fed to poultry or swine. Dow AgroSciences has submitted a study investigating the metabolism of [isoxazole - 5 - 14 C]isoxaben (specific activity 5.8 mCi/mmol) and [phenyl 14 C]isoxaben (specific activity 31.7 mCi/mmol) in goats. Each radiolabeled test substance was admin istered to two lactating goats at a dose level of 10 mg ai/kg feed/day . The daily oral dose was administered in the morning for five consecutive days using a bolus gun. Based on final feed consumption during the dosing period, the actual dosing was 12.290 mg ai/kg feed/day for the [isoxazole - 5 - 14 C]isoxaben dosed goat and 19.460 mg ai/kg feed/day for the [phenyl 14 C]isoxaben dosed goat. (The goat dosed with [phenyl 14 C]isoxaben consumed less f ee d than expected.) Samples of milk, urine, and feces were collected daily

throughout the study . Approximately 7 hours after the final dose the animals were sacrificed and matrices were collected, including liver, kidney , muscle (loin and flank), fat (subcutaneou s, omental, and renal), bile, and the gastrointestinal tract. The in - life and analy tical phases of the study

were conducted by

the Charles River L aboratory (Edinburgh, United Kingdom). Total radioactive residues (TRR) were higher in isoxazole - label sampl es than in phenyl - label samples. TRR in total goat matrices were determined by combustion/L SC. The maximum calculated TRR for isoxazole - label goat matrices were 2.026, 0.279, 0.026, 0.024, and 0.021 ppm for liver, kidney , milk, muscle, and fat matrices r espectively . The maximum calculated TRR for phenyl - label goat matrices were 1.080, 0.181, 0.015, 0.015, and 0.012 ppm for liver, kidney, milk, muscle, and fat matrices respectively . Solvent extraction with acetonitrile (ACN) and ACN/water released the m ajority (89 - 98.5% TRR) of the radioactivity (with highest levels in the ACN extract) from goat matrices from both labels; nonextractable residues accounted for 1.5 - 11.0% TRR (<0.001 - 0.051 ppm) in goatIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 15 of 38 matrices. The extraction/hydrolysis procedures adequat ely extracted the majority

of residues from goat matrices. The accountability ranged from 78 - 100%, with extractions in milk having the poorest accountability (78 - 90%) while other matrices ha d much higher accountability (97 - 100%). Residues were identified and confirmed using HPL C, with comparison to known reference standards for identifying specific metabolites. L C/MS analy sis was used to analy ze the putative metabolite of 3 - hydroxy isoxaben (using a reference standard) and to evaluate the hy pothesized fr agmentation pathway of this metabolite. The metabolic pattern , summarized in Tables 10a - 10d was similar in isoxazole - and phenyl - label goat matrices . The parent isoxaben was identified as a major residue in fat matrices (11 - 23% TRR; 0.002 - 0.004 ppm) , but was also found to be a minor residue in liver and muscle matrices. An oxime isomer metabolite (RT=16.5 min) was identified as a major metabolite in liver (13 - 14% TRR; 0.260 - 0.279 ppm) and kidney (12% TRR; 0.032 ppm) matrices and a minor one in muscl e in the isoxazole labeled goat. By contrast, this oxime metabolite was only found to be a major metabolite in liver and a minor metabolite in kidney and muscle in the phenyl label goat. Another oxime metabolite (RT=17.5) was identified as a major metabo lite only in kidney (1 - 22% TRR; 0.002 - 0.069 ppm). Additionally , a carboxylic acid metabolite was found to be a major metabolite only

in kidney (29 - 43% TRR; 0.052 - 0.105 ppm). Inliver matrices, 60 - 68% (0.649 - 1.379 ppm) of the TRR was tentatively ident ified as being either oxime isomer metabolite, 3 - hydroxy isoxaben, or hydroxylated isoxaben. In milk, muscle, and fat, significant portions of the TRR were identified as being either oxime isomer, 3 - hydroxy isoxaben, hydroxylated isoxaben, or the carboxyl ic acid metabolite, specifically with the following % TRR values observed: Milk

– 14 - 32% (0.001 - 0.005 ppm); Muscle

– 39 - 59% (0.006 - 0.014 ppm); Fat

– 26 - 35% (0.003 - 0.007 ppm). In addition, across all matrices there were many components <L OQ that were group ed together to form a significant portion of the TRR, with the following ranges of % TRR observed: Milk 40 - 73% (0.005 - 0.009 ppm); Muscle 18 - 56% (0.003 - 0.014); Fat 20 - 36% (0.002 - 0.007); L iver 4 - 5% (0.040 - 0.105 ppm); Kidney 10 - 23% (0.017 - 0.63 ppm). Overall, 84% of the administered dose was recovered for the isoxazole - labeled isoxaben and 69% recovered for the phenyl - labeled isoxaben, with the majority of the dose being recovered in the excreta (60% in feces and 14% in urine for the isoxazole label; 53% in fe ces and 8% in urine for the phenyl label). Only a small portion of the administered dose was distributed in milk, with 0.22% recovered for the isoxazole label and 0.09% for the pheny l label. No storage stability

data for sample matrices was provided by the petitioner. Based on the dates of sample collection, extraction, and HPL C analysis, all samples were analy zed within 4 - 6 months of sample collection. Is oxaben metabolism in the lactating goat is proposed to occur by hydroxylation to form the 3 - hydo xy isoxaben metabolite and the hydroxylated isoxaben metabolite (with the hydroxylation occurring on the methyl pentanyl moiety ). Oxidation of these hydroxylated metabolites is hy pothesized to result in the carboxylic acid metabolite of isoxaben. Two oxi me metabolites (of unclear stereochemistry

) are then formed by

hydryoly tic cleavage of the isoxazole ring. Finally , cleavage of the amide link in isoxaben causes the formation of the 2,6 dimethoxy benzamide, 2,6 - dimethoxy

benzoic acid, and 2 - hydroxy- 6 - metho xy benzamide metabolites (minor residuesIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 16 of 38 identified in liver, kidney , and muscle in the phenyl label goat matrices). Conclusions . Although the goat metabolism study identified low percentages of the total radioactive residues in most matrices, it is ade quate for the proposed uses based on the very low dietary burden for cattle. Only

one commodity

associated with the proposed uses, almond hulls, is a cattle feed item. There are no poultry or swine feed items associated with the proposed uses. HED revie w of the livestock metabolism study indicates that a cattle feeding study , and tolerances for livestock commodities are not needed. Another goat metabolism study with better identification and characterization of the residues will be needed for any additi onal uses of isoxaben that result in significantly higher dietary

burdens. HED concludes that residues in milk, ruminant and poultry meat, fat, and meat by

products and eggs remain a 40CFR §180.6[a][3] situation (there is no expectation of finite residues in these commodities). No poultry or swine metabolism studies are required to support the proposed uses.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 17 of 38 Table 10a. Summary of Characterization and Identification of Radioactive Residues in Goat Matrices Following the Oral Admini stration of Radiolabeled [ 14 C] - 5 - Isoxazole Isoxaben at a Rate of 12.290 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Flank) Fat (Subcutaneous) Liver (Replicate 1) Kidney

(Replicate 1) Milk

– Day 3 Milk

– Day 5 TRRs = 0.024 ppm TRRs = 0.021 ppm TRRs = 2.026 ppm TRRs = 0.279 ppm TRRs = 0.026 ppm TRR=0.020 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm Isoxaben 11.3 0.002 1.4 0.029 Oxime Isomer (RT=16.5) 5.4 0.001 12.9 0.260 11.5 0.032 Oxime Isomer (RT=17.0) 0.6 0.013 0 .6 0.002 Oxime Isomer (RT=17.5) 23.4 0.065 Carboxylic Acid Metabolite 36.5 0.102 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben 68.0 1.378 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben Carboxylic acid metabolite 38.9 0.009 35.1 0.007 20.7 0.004 Unknown (RT=10.5) 1.1 0.022 Unknown (RT=15.0) 2.1 0.043 Unknown (RT=20.5) 22.6 0.005 Unknown (RT=22.0) 5.0 0.101 Acidifie d aqueous ACN 0.3 0.006 -- <LOQ Pepsin Labile 0.9 0.018 1.6 0.004 Many components <LOQ 55.7 0.014 20.3 0.005 5.2 0.105 22.5 0.063 73.0 0.019 63.3 0.013 Total identified 5.4 0.001 11.3 0.002 14.9 0.302 72 0.201 0 0 0 0 Total characterize d 94.6 0.023 78.0 0.017 82.6 1.673 24.1 0.067 73.0 0.019 84.0 0.017 Total extractable 100.0 0.024 89.3 0.019 97.5 1.975 96.1 0.268 73.0 0.019 84.0 0.017 Unextractable (PES) 1

-- <LOQ 10.8 0.002 2.5 0.051 2.7 0.008 11.0 0.003 7.1 0.001 Accountability

2 ~10 0 ~100 ~100 99 85 90 1 Residues remaining after exhaustive extractions . 2 Accountability = (Total extractable + Total unextractable)/(TRRs from combustion analysis) * 100.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 18 of 38 Table 10b. Summary of Characterization and Identification of Radioactive Residues in Goat Matrices Following the Oral Administration of Radiolabeled [ 14 C] - 5 - Isoxazole Isoxaben at a Rate of 12.290 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Loin) Fat

(Omental) Fat (Renal) Liver

(Replicate 2) Kidney

(Replicate 2) T RRs = 0.023 ppm TRRs = 0.020 ppm TRRs = 0.020 ppm TRRs = 1.979 ppm TRRs = 0.274 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm Isoxaben 17.5 0.004 20.6 0.004 1.4 0.027 Oxime Isomer (RT=16.5) 14.1 0.279 11.5 0.032 Oxime Isomer (RT=17.0 ) Oxime Isomer (RT=17.5) 25.1 0.069 Carboxylic Acid Metabolite 38.4 0.105 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben 67.8 1.342 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben Carboxylic acid metabolite 58.9 0.014 29.2 0.006 28.9 0.006 Unknown (RT=10.5) 1.3 0.026 Unknown (RT=12.5) 0.6 0.012 Unknown (RT=15.0) 2.4 0.048 Unknown (RT=20.5) 14.7 0.003 17.4 0.004 Unknown (RT=22. 0) 5.0 0.098 Acidified aqueous ACN 0.4 0.008 -- <LOQ Pepsin Labile 1.0 0.020 1.8 0.005 Many components <LOQ 41.1 0.009 36.4 0.007 27.1 0.005 4.6 0.091 18.9 0.051 Total identified 0 0 17.5 0.004 20.6 0.004 15.5 0.306 75.0 0.206 Tota l characterized 100 0.023 80.3 0.016 73.4 0.015 83.1 1.645 20.7 0.056 Total extractable 100 0.023 97.8 0.020 94.0 0.019 98.6 1.951 95.7 0.262 Unextractable (PES) 1

-- <LOQ 2.2 <0.001 6.0 0.001 1.5 0.030 2.8 0.008 Accountability

2 100 100 100 ~100 ~99 1 . Residues remaining after exhaustive extractions . 2 . Accountability = (Total extractable + Total unextractable)/(TRRs from combustion analysis) * 100.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 19 of 38 Table 10c. Summary of Characterization and Identification of Radioactive Residues in Goat Matrices F ollowing the Oral Administration of Radiolabeled [ 14 C] - UL - Phenyl Isoxaben at a Rate of 19.460 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Loin) Fat (Subcutaneous) Liver (Replicate 2) Kidney

(Replicate 2) Milk

– Day 3 Milk

– Day 5 T RRs = 0.015 ppm TRRs = 0.012 ppm TRRs = 1.080 ppm TRRs = 0.181 ppm TRRs = 0.009 ppm TRR=0.015 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm % TRR Ppm % TRR ppm Isoxaben 3.0 <0.001 20.9 0.002 1.9 0.020 Oxime Isomer (RT=16.5) 7.2 0.001 10.8 0.1 17 9.4 0.017 Oxime Isomer (RT=17.5) 1.0 0.002 2,6 - Dimethoxybenzamide 3.4 0.001 4.2 0.045 6.6 0.012 2.5 <0.001 6.2 0.001 2,6 - Dimethoxybenzoic acid 0.3 0.001 2 - Hydroxy - 6 - methoxy - Benzamide 3.8 0.041 8.2 0.015 Desmethyl Isoxaben 2.7 <0.001 Carboxylic Acid Metabolite 43.4 0.078 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben 60.1 0.649 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben Carboxylic acid metabolite 39.8 0.006 28.8 0.003 13.6 0.001 31.7 0.005 Unknown (RT=3.5) 2.5 <0.001 Unknown (RT=5.0) 0.1 0.001 0.1 <0.001 Unknown (RT=10.5) Unknown (RT=13.5) 0.3 0.003 Unknown (RT=14.5) 0.4 0.005 Unknown (RT=20.5) 2.7 <0.001 26.4 0.003 Unknown (RT=21.0) 0.1 0.001 Unknown (RT=21.5) 6.9 0.074Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 20 of 38 Table 10c. Summary of Characterization and Identification of Radioactive Residues in Goat Matrices F ollowing the Oral Administration of Radiolabeled [ 14 C] - UL - Phenyl Isoxaben at a Rate of 19.460 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Loin) Fat (Subcutaneous) Liver (Replicate 2) Kidney

(Replicate 2) Milk

– Day 3 Milk

– Day 5 T RRs = 0.015 ppm TRRs = 0.012 ppm TRRs = 1.080 ppm TRRs = 0.181 ppm TRRs = 0.009 ppm TRR=0.015 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm % TRR Ppm % TRR ppm Unknown (RT=24.0) 1.9 0.020 Unknown (RT=30.0) 9.6 0.001 Unknown (RT=49.5) 0.6 0. 007 Acidified aqueous ACN 0.6 0.006 0.7 0.001 Pepsin Labile 1.8 0.019 2.8 0.005 Many components <LOQ 30.6 0.005 21.0 0.003 4.3 0.046 19.7 0.035 53.9 0.005 40.3 0.006 Total identified 13.6 0.002 20.9 0.002 20.7 0.223 68.9 0.125 5 .2 <0.002 6.2 0.001 Total characterized 73.1 0.011 76.2 0.009 75.2 0.811 23.3 0.041 77.1 0.007 74.5 0.011 Total extractable 86.7 0.013 97.1 0.011 95.9 1.034 92.2 0.166 82.3 0.007 80.7 0.012 Unextractable (PES) 1 7.7 0.001 2.9 <0.001 4.1 0.044 5.3 0.010 5 .2 <0.001 3.8 <0.001 Accountability

2 93 ~100 ~100 97 78 80 1 Residues remaining after exhaustive extractions . 2 Accountability = (Total extractable + Total unextractable)/(TRRs from combustion analysis) * 100. Table 10d. Summary of Characterization an d Identification of Radioactive Residues in Goat Matrices Following the Oral Administration of Radiolabeled [ 14 C] - UL - Phenyl Isoxaben at a Rate of 19.460 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Flank) Fat (Omental) Liver (Replicate 1) Kidney

(Replicate 1) TRRs = 0.013 ppm TRRs = 0.011 ppm TRRs = 1.080 ppm TRRs = 0.177 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm Isoxaben 5.7 0.001 22.8 0.003 2.0 0.022 Oxime Isomer (RT=16.5) 3.2 <0.001 10.8 0.117 7.8 0.014 Oxime Isomer (RT=17.5 ) 22.1 0.039 2,6 - Dimethoxybenzamide 2.9 <0.001 3.2 0.035 4.5 0.009 2,6 - Dimethoxybenzoic acid 3.7 0.007 2 - Hydroxy - 6 - methoxy - B enzamide 4.2 0.045 8.2 0.015 Desmethyl IsoxabenIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 21 of 38 Table 10d. Summary of Characterization an d Identification of Radioactive Residues in Goat Matrices Following the Oral Administration of Radiolabeled [ 14 C] - UL - Phenyl Isoxaben at a Rate of 19.460 mg ai/kg feed/day for Five Consecutive Days Compound Muscle (Flank) Fat (Omental) Liver (Replicate 1) Kidney

(Replicate 1) TRRs = 0.013 ppm TRRs = 0.011 ppm TRRs = 1.080 ppm TRRs = 0.177 ppm % TRR ppm % TRR ppm % TRR ppm % TRR ppm Carboxylic Acid Metabolite 29.1 0.052 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben 61.2 0.661 Oxime isomer 3 - hydroxy isoxaben Hydroxylated isoxaben Carboxylic acid metabolite 52.0 0.007 25.5 0.003 Unknown (RT=5.0) 0.1 0.001 0.2 <0.001 Unknown (RT=10.0) 0.1 <0.001 Unknown (RT=20.5) 8.5 0.001 24.5 0.003 Unknown (RT=21.5) 8.1 0.087 1.7 0.003 Acidified aqueous ACN 0.6 0.006 0.7 0.001 Pepsin Labile 1.8 0.019 2.8 0.005 Many components <LOQ 18.4 0.003 25.5 0.002 3.7 0.040 10.2 0.017 Total identified 11.8 0.001 22.8 0.003 20.2 0.22 75.4 0.136 Total characterized 78.9 0.011 75.5 0.008 75.5 0.814 15.7 0.026 Total extractable 90.7 0.012 98.3 0.011 95.7 1.034 91.1 0.162 Unextractable (PES) 1 9.3 0.001 1.7 <0.001 4.2 0.045 6.9 0.012 Accountability

2 100 100 ~100 98 1 Residues remaining after exhaustive extractions . 2 Accountability = (Total extractable + Total unextractable)/(TRRs from combustion analysis) * 100.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 22 of 38 860.1340 Residue Analytical Methods DER Reference: 47492601.der.doc Residue Analytical Method

47140007.der.doc Residue Analytical Method and ILV Enforcement method: Dow AgroSciences has submitted a study of a proposed residue analy tical method (RAM) utilizing liquid chromatography with tandem mass spec trometric detection (LC/MS/MS), GRM 02.26.S.1 (a revision of GRM 02.26). Dow has proposed this method to enforce tolerances for residues of isoxaben in or on various crop commodities. The method, entitled Determination of Residues of Isoxaben in Cereals, Chicory, Endives, Almonds, Pecans, and Grapes by Liquid Chromatography with Tandem Mass Spectrometry , was used for supplementary

method validation generated during analysis of samples from almond, pecan and grape field trial studies associated with DP Barcode D342083. Briefly , residues of isoxaben are extracted from crop samples with acetonitrile (ACN)/water (7:3, v:v). An aliquot of the extract is diluted with water, and subjected to liquid - liquid extraction on a diatomaceous earth column, using dichl oromethane to elute the residues. The eluate is evaporated to dry

ness, redissolved in methanol/water (1:1, v:v) containing 5 mM ammonium acetate, and analy

zed by L C/MS/MS. The validated limit of quantitation (L OQ) is 0.010 ppm for isoxaben in each matrix . The limits of detection (L ODs) were calculated and reported as ranging from 0.0008 ppm (in endives) to 0.0029 ppm (in cereal straw). The method includes instructions for the analysis of samples of cereal, chicory , endive, almond, pecan and grape comm odities. The method was adequately validated by

the petitioner using fortified samples of barley (forage, grain and straw), wheat (forage, grain and straw), chicory (roots and foliage), whole endives, almonds (nutmeat and hulls), pecans (nutmeat), and grapes (fruit, juice and raisins). Overall, recoveries of isoxaben ranged 63 - 120% from samples fortified at 0.010 ppm (L OQ), 0.10 ppm, 0.50 ppm, and 1.00 ppm. The revised method, as written, monitors three MS/MS ion transitions for isoxaben (m/z 333 →165 for quantitation, m/z 333→150 for confirmation, and m/z 333→107 for confirmation), as shown on page 38 of the report. However, it was noted that the third produ ct ion in the table in Section 8.2 (page 19 of the report) is listed as m/z 150 instead of m/z 107. BEAD’s Analy tical Chemistry

Branch (ACB) currently

recommends that enforcement methods include information for two MS/MS ion transitions per analy te in ord er to be considered sufficiently specific not to require a confirmatory

method, so the current revised method exceeds this requirement. No radiovalidation data were submitted for method GRM 02.26.S.1. Because the extraction solvents used for this metho d are very similar to those used in the barley and grape metabolism studies associated with D342083, HED concludes that radiovalidation of the method will not be required at this time. An independent laboratory validation (ILV) was not submitted for the e n forcement method GRM 02.26.S.1. However, an ILV study was submitted for the initial Method GRM 02.26 with wheat grain and endive leaves fortified with isoxaben at 0.01 ppm, 0.02 ppm, and 0.10 ppm. Adequate recoveries were obtained for both commodities using the method as written.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 23 of 38 Data collection: The related method, L C/MS/MS method GRM 02.26, was used for data collection in samples of grape and tree nut commodities from the crop field trial and processing studies associated with this petition. Brie fly , residues of isoxaben are extracted from crop samples with acetonitrile (ACN):water (70:30, v:v). An aliquot of the extract is diluted with water and subjected to liquid - liquid extraction on a diatomaceous column, using dichloromethane to elute the re sidues. The eluate is evaporated to dry

ness, redissolved in methanol:water (50:50, v:v) containing 5 mM ammonium acetate, and analy

zed by L C/MS/MS. The validated limit of quantitation (L OQ) is 0.01 ppm for isoxaben in each matrix. The L ODs were calculat ed and reported as ranging from 0.00016 ppm for endive to 0.0029 ppm for cereal straw. The method, as written, includes instructions for the analysis of samples of cereals (wheat and barley ), chicory (roots and leaves) and whole endives. The method was a dequately validated using fortified samples of barley forage, barley

grain, barley straw, chicory

root, chicory

foliage, whole endive, wheat forage, wheat grain, and wheat straw. Overall, recoveries of isoxaben ranged 71 - 108%, with an average of 91% (stan dard deviation of 6.5%), from samples fortified at 0.01 ppm (L OQ), 0.10 ppm, and 1.0 ppm. The commodities of grapes and tree nuts, in which tolerances have been proposed, were not included in the validation study . Concurrent method recovery data for th ese commodities were included with the crop field trial and processing studies submitted in conjunction with DP Barcode D 342083. These concurrent method validation data are sufficiently representative of the expected residue levels in the plant commoditie s. As stated above, an independent laboratory validation (ILV) study

was submitted for Method GRM 02.26 (the grape and tree nut data collection method) with wheat grain and endive leaves fortified with isoxaben at 0.01 ppm, 0.02 ppm, and 0.10 ppm. Adequate recoveries were obtained for both commodities using the method as written. As with Method GRM 02.26.S.1, n o confirmatory analysis procedures were included in the method, and no interference study was submitted. The petitioner stated that because of th e specificity

of the L C/MS/MS analy ses, no further confirmation was needed. The method as written only

monitors one transition ion for isoxaben. ACB currently recommends that enforcement methods include information for two MS/MS ion transitions per analy te in order to be considered sufficiently specific not to require a confirmatory method. When two transitions are not available, ACB recommends providing an alternate chromatographic column and/or mobile - phase combination to reduce the possibility of fals e positive residues. As with Method GRM 02.26.S.1, n o radiovalidation data were submitted for method GRM 02.26. Because the extraction solvents used for the data collection method are very similar to those used in the barley

and grape metabolism studies associated with D342083, HED concludes that radiovalidation of the method will not be required at this time. Conclusions . The plant commodity analy tical method data are adequate to satisfy data requirements for both data collection and tolerance enforcem ent . T he petitioner did not submitIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 24 of 38 an ILV study

for the proposed enforcement method using a crop commodity associated with the prop osed uses . The submitted ILV for Method GRM 02.26 was submitted with wheat grain and endive leaves fortified with isoxaben at 0.01 ppm, 0.02 ppm, and 0.10 ppm. Adequate recoveries were obtained for both commodities using the method. As a result, an ILV for the proposed enforcement method, GRM 02.26.S.1, will not be required. HED notes that the OPPTS Guideline 860.1340 speci fies that the commodity chosen for ILV should be the commodity the petitioner has had the most difficulty analy zing. Based on the review of the submitted livestock metabolism data, HED concludes that an analy tical method for livestock commodities is not r equired to support the proposed uses under this petition. HED concludes that residues in milk, ruminant and poultry meat, fat, and meat by products and eggs remain a 40CFR §180.6[a][3] situation (there is no expectation of finite residues in these commodit ies). However, analy tical methods for livestock commodities may be needed for any

additional uses of isoxaben that result in significantly higher dietary

burdens. 860.1360 Multiresidue Methods No multiresidue method testing data were submitted with th is petition. The FDA PESTDATA database (dated 06/05) indicates that isoxaben is completely recovered using multiresidue method Section 302. The database did not include any information for any

of the other test methods. 860.1380 Storage Stability DER References: 47 4621901 .der.doc The storage durations and conditions of samples from the crop field trials submitted to support this petition are presented in Table 11 . Table 11 . Summary of Storage Conditions/Durations of Samples fromCrop Field Trial and Processing Studies. Matrix Storage Temperature (°C) Actual Storage Duration Interval of Demonstrated Storage Stability Almond, hulls - 20 144 - 186 days (4.7 - 6.1 months) S table under frozen storage conditions ( ≤ - 20 °C ) for up to 24 months in/on grape and cereal matrices, and for up to 12 months in/on endive leaves . Almond, nutmeat 149 - 191 days (4.9 - 6.3 months) Grape (field trials) 106 - 184 days (3.5 - 6.1 months) Grape (processing study) 128 days (4.2 months) Raisins 120 days (3.9 months) Juic e 124 days (4.1 months) Pecan, nutmeat 77 - 110 days (2.5 - 3.6 months) Dow AgroSciences submitted a storage stability study with isoxaben on grapes, cereal grain ,Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 25 of 38 cereal straw, and endive leaves. Untreated samples for all matrices were fortified with isoxaben at 0.1 ppm, and then stored frozen ( ≤ - 20 °C ). Subsamples of fortified samples were collected at 3 - , 6 - , 12 - , 18 - and 24 - month storage intervals and analy zed for residues of isoxaben using high pressure liquid chromatography with positive ion atmo spheric pressure chemical ionization mass spectrometry (LC/MS) . Inthe submitted storage stability data for isoxaben , residues were relatively stable under frozen storage conditions ( ≤ - 20 °C ) for up to 24 months in/on grape and cereal matrices, and for up to 12 months in/on endive leaves; see Table 12. TABLE 12. Stability of Isoxaben Residues in Grape, Cereal Grain, Cereal Straw and Endive Leaves

following Storage at ≤ - 20°C. Matrix Spike Level (ppm) Storage Interval

(days) Sample Size (n) Mean Recovered Residue (%) Mean Corrected Recovery

(%) Grape 0.1 90 3 0.095 113 180 3 0.085 103 365 3 0.079 103 552 3 0.090 114 720 3 0.080 108 Cereal Grain 0.1 85 3 0.097 99.5 179 3 0.100 105 367 3 0.092 100 575 3 0.096 107 725 3 0.091 99.2 C ereal Straw 0.1 85 3 0.088 96.1 179 3 0.096 99.7 367 3 0.087 93.8 575 3 0.094 111 725 3 0.084 98.8 Endive Leaves 0.1 90 3 0.106 112 181 3 0.105 102 365 3 0.104 101 Conclusions . The available storage stability data indicate that residu es of isoxaben are stable under frozen storage conditions for up to 24 months in/on grapes, cereal grain and cereal straw, and for up to 12 months in/on endive leaves. 860.1480 Meat, Milk, Poultry, and Eggs The only livestock feedstuff associated with th e proposed use is almond hulls. Almond hulls are not fed to poultry

or swine. The worst case dietary burden of isoxaben to beef and dairy cattle is presented in Table 1 3 . Table 1 3 . Calculation of Dietary Burdens of Isoxaben Residues to Livestock. Fe edstuff Ty pe 1 % Dry Matter2 % Diet2 Recommended

Tolerance (ppm) Dietary

Contribution (ppm) 3 Beef and Dairy Cattle Almond, hulls R 90 10 0. 40 0.0 44Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 26 of 38 Table 1 3 . Calculation of Dietary Burdens of Isoxaben Residues to Livestock. Fe edstuff Ty pe 1 % Dry Matter2 % Diet2 Recommended

Tolerance (ppm) Dietary

Contribution (ppm) 3 Other R, not treated R -- 2 0 N/A N/A CC, not treated CC -- 55 N/A N/A PC, not treated PC -- 15 N/A N/A TOTAL BURDEN -- -- 100 -- 0.0 44 1 R: Roughage; CC: Carbohydrate concentrate; PC: Protein concentrate. 2 OPPTS 860.1000 Table 1 Feedstuffs ( June 2008 ). Rarely fed at up to 10%, 5% would reflect a mo re typical feeding level . 3 Contribution = ([t olerance /% DM] X % diet). No livestock feeding studies were submitted with this petition. The petitioner has requested a waiver from the requirement for a tolerance for isoxaben in or on cattle meat by products, meat, and milk. Conclusions . A livestoc k metabolism study has been submitted to support the proposed uses. There are no poultry

or swine feed items associated with the proposed uses. HED ’s review of this goat metabolism study indicates that a cattle feeding study , and tolerances for livestoc k commodities are not needed for the proposed uses currently under consideration. Although the goat metabolism study

identified low percentages of the total radioactive residues in most matrices, it is adequate for the proposed uses, based on the very low dietary

burden for cattle. Another goat metabolism study with better identification and characterization of the residues will be needed to support any

additional uses of isoxaben that result in significantly higher dietary burdens. HED concludes that re sidues in milk, ruminant and poultry meat, fat, and meat by products and eggs remain a 40CFR §180.6[a][3] situation ( i.e., no expectation of finite residues in these commodities). 860.1500 Crop Field Trials DER Reference: 47140008.der.doc (Almond)

47140 009.der.doc (Pecan) 47040010.de1.doc (Grape) To support the proposed uses on grapes and tree nuts, Dow AgroSciences has submitted crop field trial data for grapes, almonds, and pecans. The submitted data are discussed below and summarized in Table 1 4 .Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 27 of 38 Table 1 4 . Summary of Residue Data fromCrop Field Trials with Isoxaben. Crop matrix Treat.

Plot No. 1 Total Applic.

Rate (lb ai/A) PHI (days) Residue Levels 2 (ppm) n Min. Max. HAFT 3 Median Mean Std. Dev. 4 GRAPE (proposed use = 1 .0 lb ai/A total ap plication rate , PHI = 165 days ) Grape 2 1.0 141 - 182 24 <0.01 <0.01 0.01 0.01 0.01 NA

3 1.0 60 24 <0.01 <0.01 0.01 0.01 0.01 NA TREE NUT (proposed use = 1 .0 lb ai/A total application rate , PHI = 60 days ) Almond, hulls 2 1.0 182 - 216 10 <0.01 <0.01 0.01 0.01 0.01 NA

3 1.0 - 1.1 60 - 61; 68 5 10 <0.01 0.301 0.267 0.039 0.085 0.103 Almond, nutmeat 2 1.0 182 - 216 10 <0.01 <0.01 0.01 0.01 0.01 NA

3 1.0 - 1.1 60 - 61; 68 5 10 <0.01 0.015 0.015 0.01 0.011 0.002 Pecan, nutmeat 2 0.7, 1.0 6 219 - 243 10 <0.01 <0.01 0.01 0.01 0.01 NA

3 1.0 57 - 60 10 <0.01 <0.01 0.01 0.01 0.01 NA 1 Treatment Plot No. 2: single application made just prior to bud break; Treatment Plot No. 3: single application made ~60 days prior to harvest. 2 For the calculation of the HAFT, median, me an, and standard deviation values, the LOQ (0.01 ppm) was used for residues reported as <LOQ. 3 HAFT = Highest Average Field Trial 4 NA = Not Applicable 5 In the residue decline trial for Treatment Plot No. 3, residues in hulls and nutmeats were highest in samples from the 68 - day sampling interval. Therefore, these samples were included in the summary instead of the results from the 61 - day sampling interval. 6 The application rate was 1.0 lb ai/A at four of the trial sites and 0.7 lb ai/A at one site. Grape Dow AgroSciences submitted field trial data for isoxaben on grapes. Twelve trials were conducted in Zones 1 (NY; 2 trials), 10 (CA; 8 trials), and 11 (WA; 2 trials) during the 2006 growing season. Each test site included one control plot and tw o treated plots. Each treated plot received a single broadcast application of a 75% DF formulation of isoxaben to the soil at 1.0 lb ai/A. The application rate represents 1x the maximum proposed single application rate and 1 x the maximum proposed seasona l rate to grapes. For one plot (at each site), designated as Treatment Plot No. 2, the application was made just prior to bud break. For the other plot, designated as Treatment Plot No. 3, the application was made 60 days prior to harvest. Applications were made using ground equipment in 23 - 29 gal/A spray volumes without an adjuvant. Samples of whole grapes were collected 141 - 182 days after application from Treatment Plot No. 2 and 60 days after application from Treatment Plot No. 3. At one trial, addi tional samples were collected at 134, 141, 148, and 155 days after treatment (Treatment Plot No. 2) and 53, 60, 67, and 74 days after treatment (Treatment Plot No. 3) for evaluation of residue decline. Samples of grapes were analy zed for residues of isoxa

ben using an adequate LC/MS/MS method, GRM 02.26, with a validated L OQ of 0.01 ppm. Samples of grapes were stored frozen (< - 20  C) for 106 - 184 days (3.5 - 6.1 months) prior to extraction for analysis. Adequate su pporting storageIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 28 of 38 stability data are available for grapes . These data indicate that isoxaben is stable in frozen storage for up to 2 years . Residues of isoxaben were below the L OQ of 0.01 ppm in/on all grape samples from Treatment Plot Nos. 2 and 3. Because isoxaben residues were below the method LOQ in/on all samples of grapes from Treatment Plot Nos. 2 and 3, the potential for residue decline could not be assessed. Tree nut, group 14 Dow AgroSciences submitted crop field trial data for almond and pecan, the representative commodities of the tr ee nut crop group. Almond : Dow AgroSciences submitted field trial data for isoxaben on almonds. Five field trials were conducted in Zone 10 (CA) during the 2006 growing season. Each test site included one control plot and two treated plots. Each tre ated plot received a single broadcast application of a 75% DF formulation of isoxaben to the soil at 1.0 - 1.1 lb ai/A. The application rate represents ~1x the maximum proposed single application rate and ~ 1 x the maximum proposed seasonal rate to tree nuts. For one plot, designated as Treatment Plot No. 2, the application was made just prior to bud break. For the other plot, designated as Treatment Plot No. 3, the application was made 60 - 61 day s prior to harvest. Applications were made using ground equipm ent in 22 - 26 gal/A spray volumes without an adjuvant. Samples of almonds (hulls and nutmeat) were collected 182 - 216 days after application from Treatment Plot No. 2 and 60 - 61 day s after application from Treatment Plot 3. At one trial, additional samples were collected at 175, 182, 189, and 196 days after treatment (Treatment Plot No. 2) and 54, 61, 68, and 75 days after treatment (Treatment Plot No. 3) to evaluate residue decline. Samples of almond hulls and nutmeat were analy zed for residues of isoxaben using an adequate LC /MS/MS method, GRM 02.26, with a validated L OQ of 0.01 ppm. Samples were stored frozen (< - 20  C) prior to extraction for analysis, for a maximum of 186 day s (4.7 - 6.1 months) for almond hulls and a maximum of 191 day s (4.9 - 6.3 months) f or almond nutmeat. No supporting storage stability

data are available for almond commodities. Residues of isoxaben were <L OQ in/on all almond nutmeat samples from Treatment Plot Nos. 2 and 3, with the exception of two samples collected from Treatment P lot No. 3 in the decline trial (sampling interval of 68 days) which bore residues of 0.014 and 0.015 ppm. Residues of isoxaben were below the L OQ in/on all samples of almond hulls from Treatment Plot No. 2, including samples from the decline trials. Resi dues of isoxaben were <0.01 - 0.301 ppm in/on almond hull samples (including samples from decline trials) from Treatment Plot No. 3. Inthe decline trial for Treatment Plot No. 2, isoxaben residues were below the L OQ in/on all samples of almond nutmeat and hulls. In the decline trial from Treatment Plot No. 3, residues of isoxaben were <L OQ in/on all samples of nutmeat except those harvested at the 68 - day sampling interval (as noted above). For almond hulls from Treatment Plot No. 3, residues of isoxaben increased from the 54 - day sampling interval (average of 0.103 ppm) to the 68 - day samplingIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 29 of 38 interval (average of 0.267 ppm) and then decreased at the 75 - day sampling interval (average of 0.123 ppm). Pecan : Dow AgroSciences has submitted field trial data for isoxaben on pecans. Five field trials were conducted in Zones 2 (GA; 2 trials), 4 (LA; 1 trial), 6 (TX; 1 trial), and 8 (TX; 1 trial) during the 2006 growing season. Each test site included one control plot and two treated plots. Each treated plot received a single broadcast application of a 75% DF formulation of isoxaben to the soil at 1.0 lb ai/A. The application rate represents ~1x the maximum proposed single application rate and ~ 1 x the maximum proposed seasonal rate to tree nuts. For one plo t, designated as Treatment Plot No. 2, the application was made just prior to bud break. For the other plot, designated as Treatment Plot No. 3, the application was made 57 - 60 day s prior to harvest. Applications were made using ground equipment in 18 - 30 gal/A spray volumes without an adjuvant. At one site (LA), application to Treatment Plot No. 2 was made at 0.7 lb ai/A due to a calculation error. Samples of pecans were collected 219 - 243 days after application from Treatment Plot No. 2 and 57 - 60 day s after application from Treatment Plot 3. At one trial, additional samples were collected at 213, 220, 227, and 234 days after treatment (Treatment Plot No. 2) and 53, 60, 67, and 74 days after treatment (Treatment Plot No. 3) to evaluate residue decline. Samples of pecan nutmeat were analy zed for residues of isoxaben using an adequate L C/MS/MS method, GRM 02.26, with a validated L OQ of 0.01 ppm. Samples of pecan nutmeat were stored frozen (< - 20  C) for 77 - 110 days (2.5 - 3.6 months) prior to extraction for analysis. No supporting storage stability

data are available for pecans. Residues of isoxaben were <L OQ in/on all pecan nutmeat samples from Treatment Plot Nos. 2 and 3. Because isoxaben residues were below the method L OQ in/on all samples of pecan nutmeat from Treatment Plot Nos. 2 and 3, the potential for residue decline could not be assessed. Conclusions . The submitted field trial data are adequate to satisfy data requirements . S upporting storage stability

data , while not available for tree nuts , are available for other commodities and indicate that isoxaben is stable in frozen storage for up to 2 years. The number and locations of field trials are in accordance with OPPTS Residue Chemistry Test Guideline 860.1500 for grapes and tree nuts, and samples were anal yz ed using an adequate method. T he available data support tolerances for residues of isoxaben in/on grapes at 0.01 ppm, the tree nut crop group at 0.02 ppm, pistachio at 0.02 ppm, and almond hulls at 0. 40 ppm. HED notes that the crop fiel d trials did not include the addition of adjuvants to the spray mixtures. The proposed use of isoxaben involves application to the weeds growing on the orchard floor such that very little contact of the crop foliage by spray droplets will occur. As a res ult, adjuvants are not expected to have a significant impact on residues of isoxaben in tree nuts or grapes and a prohibition of adjuvants is not needed on the product label.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 30 of 38 860.1520 Processed Food and Feed DER Reference: 47140010.de2.doc Processing data for grapes are required to support the proposed uses; no processing data for tree nuts are required. Dow AgroSciences submitted a processing study with isoxaben on grapes. Samples used for processing were generated from one trial conducted in NY during the 2006 growing season. Grapes were harvested 60 days following a single broadcast application of the 75% DF formulation of isoxaben to the soil at 5.0 lb ai/A (5x the field trial rate and 5x the proposed maximum seasonal rate ). Application was made using ground equipment in 25 gal/A spray volumes without an adjuvant. Whole grapes were processed into raisins and juice using simulated commercial processes. Samples of grapes (whole fruit) and the processed commodities (raisins and juice) were analy ze d for residues of isoxaben using an adequate L C/MS/MS method, GRM 02.26, with a validated LOQ of 0.01 ppm. Samples were stored frozen (< - 20  C) prior to extraction for analysis, for a maximum of 128 day s (4.2 months) for grape, 120 days (3.9 months) for ra isins, and 124 days (4.1 months) for grape juice. S upporting storage stability data are available for grapes , and indicate that isoxaben is stable in frozen storage for up to 2 years. Following a single broadcast application of the 75% DF formulation o f isoxaben at 5.0 lb ai/A, all residues were below the LOQ in/on all samples of grapes, raisins, and grape juice; therefore, processing factors could not be calculated. The theoretical concentration factors are 1.2x for grape juice (based on separation into components; OPPTS 860.1520, Table 3) and 4.7x for raisins (based on loss of water; OPPTS 860.1520, Table 2). Conclusions . The submitted processing data are adequate to satisfy data requirements . The data indicate that no tolerances are needed for the p rocessed commodities of grapes. 860.1650 Submittal of Analytical Reference Standards An analy tical standard for isoxaben is currently available in the EPA National Pesticide Standards Repository

with a expiration date of March 201 2 (personal communication with Theresa M. Cole , ACB, 4/16/08). 860.1850 and 860.1900 Confined and Field Accumulation in Rotational Crops Because grapes and tree nuts are not rotated, no data pertaining to rotational crops are required to support the proposed use. 860.1550 Proposed Tolerances The petitioner has proposed that the tolerance expression for isoxaben consist of residues of parent isoxaben only . For the purposes of this petition only , the nature of the residue in grapesIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 31 of 38 and tree nuts is ade quately understood ( for early

season uses only

) based on grape and barley metabolism studies. HED recommends the isoxaben tolerance expression be established as follows: “Tolerances are established for residues of the herbicide isoxaben , including its me tabolites and degradates, in or on the commodities in the table below. Compliance with the tolerance levels specified below is to be determined by

measuring only isoxaben [N - [3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2, 6 - dimethoxy

benzamide] in or on the c ommodity . ” No Codex, Canadian, or Mexican MRL s have been established for isoxaben. A tolerance summary

for isoxaben is presented in Table 1 5 . T he available crop field trial data support tolerances for isoxaben residues in/on grape, the tree nut crop group, pistachio, and almond hulls. For all commodities except almond hulls, residues were below the LOQ in/on ≥80% of samples; therefore, the tolerance spreadsheet in the Agency ’s Guidance for Setting Pesticide Tolerances Based on Field Trial Data was no t used to calculate tolerance s for these commodities. The tolerance for grape should be set at the LOQ, 0.01 ppm. The maximum residues observed in almond and pecan were 0.015 ppm; therefore, the proposed tolerance of 0.03 ppm for the tree nut group is too high. A tolerance of 0.02 ppm would be appropriate for the tree nut crop group. HED has determined that pistachio should be added to the tree nut crop group; almond and pecan w ill remain the representative commodities for this group. Until the crop is officially added to the crop group listings in 40 CFR, residue data for almond and pecan may be used to establish a tolerance for pistachio, which is to be set at the same level as the tree nut tolerance. Therefore, the proposed tolerance of 0.03 ppm f or pistachio is too high; a tolerance of 0.02 ppm would be appropriate. The tolerance calculation for almond hulls is presented in Appendix II. The available data indicate that a 0.40 ppm tolerance for almond hulls would be a ppropriate. The availabl e processing data indicate that residues of isoxaben do not concentrate in grape juice or raisins. Therefore, no tolerances are needed for grape processed commodities. The proposed tolerances should be removed from Section F. Although the goat metabol ism study identified low percentages of the total radioactive residues in most matrices, it is adequate for the proposed uses based on the very low dietary

burden for cattle. There are no poultry or swine feed items associated with the proposed uses. HED ’s review of the livestock metabolism study indicates that a cattle feeding study and tolerances for livestock commodities are not needed. Another goat metabolism study with better identification and characterization of the residues will be needed for any additional uses of isoxaben that result in significantly

higher dietary

burdens. HED concludes that residues in milk, ruminant and poultry meat, fat, and meat by

products and eggs remain a 40CFR §180.6[a][3] situation (there is no expectation of finite re sidues in these commodities). Therefore, no tolerances are needed for livestock commodities.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 32 of 38 Table 1 5 . Tolerance Sum ma ry for Isoxaben. Commodity Proposed Tolerance (ppm) Recommended

Tolerance (ppm) 1 Comments; Correct Commodity

Definition Grape 0.0 1 0.01 Grape, juice 0.01 Remove A separate tolerance for grape juice is not needed. Grape, raisin 0.01 Remove A separate tolerance for raisin is not needed. Nut, tree, Group 14 0.03 0.02 Nut, tree, Group 14 Pistachio 0.03 0.02 Almond, hulls 0.35 0. 4 0 1 The recommended tolerance levels are based on the current crop field trial data and assume that the petitioner will mo dify the proposed uses to correspond to the use patterns of the crop field trials. References European Food Safety

Authority

(EFS A), May

2006 Draft Report PP #5G3216. EL - 107® on wheat and barley . Comments on the analy tical method and residue data. RCB #591, J. Worthington, 5/17/85. MRIDs: 073291 and 072296 PP #5G3216. EL - 107 on wheat and barley . Comments on the amendment of 6/17/85. RCB #1188, J. Worthington, 7/26/85. MRID: 073648 Attachments: International Residue L imit Status sheet Appendix I - Chemical Name and Structure Table Appendix I I - Tolerance Assessment C alculationsIsoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 33 of 38 

## INTERNATIONAL RESIDUE LIMIT STATUS Chemical Name: N - [3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxybenzamide Common Name: Isoxaben X Proposed tolerance [ ] Reevaluated tolerance [ ] Other Date: 7 / 12 / 10 Codex Status (Maximum Residue L imits) U. S. Tolerances X No Codex proposal step 6 or above [ ] No Codex proposal step 6 or above for the crops requested Petition Number: PP#7E7222 DP#s: 341694, 342083 Other Identifier: Residue definition (step 8/CXL): N/A Reviewer/Branch: D. McNe illy/RAB2 Residue definition: Isoxaben Crop (s) MRL (mg/kg) Crop(s) Tolerance (ppm) Grape 0.01 Grape, juice N/A Grape, raisin N/A Nut, tree, group 0.03 Pistachio 0.03 Almond, hulls 0. 40 Limits for Canada Limits for Mexico X No Limi ts [ ] No Limits for the crops requested X No Limits [ ] No Limits for the crops requested Residue definition: N/A Residue definition: N/A Crop(s) MRL (mg/kg) Crop(s) MRL (mg/kg)

Notes/Special Instructions: S.Funk, 08/16/2007Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 34 of 38 APPENDIX I. Chemical Nam es and Structures of Isoxaben and Metabolites. Common name; Company code Chemical name Chemical structure Isoxaben N - [3 - (1 - ethyl - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxybenzamide

O C H 3 N H O O N C H 3 C H 3 C H

3 O C H 3

Metabolite I 1 2,6 - dimethoxybenzoic acid O C H 3

O C H

3 O H O

Isoxaben - 2 - hydroxy/ Metabolite II (mixture of two diastereomers) N - [3 - (1 - ethyl - 2 - hydroxy - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxybenzamide O C H 3

O C H

3 N H O O N C H 3 C H 3 C H

3 O H

Isoxaben - 3 - hydroxy/ Metabolite III N - [3 - (3 - hydroxy - 1 - ethyl - 1 - methylpropyl) - 5 - isox azolyl] - 2,6 - dimethoxybenzamide O C H 3

O C H

3 N H O O N C H 3 C H 3 O H

Isoxaben - 1 - hydroxy/ Metabolite IV N - [3 - (1 - hydroxy - 1 - methylpropyl) - 5 - isoxazolyl] - 2,6 - dimethoxybenzamide

O C H 3 N H O O N C H 3 O H C H

3 O C H 3Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 35 of 38 APPENDIX I. Chemical Nam es and Structures of Isoxaben and Metabolites. Common name; Company code Chemical name Chemical structure 2 - OH - 6 - OMe benzamide 2 - hydroxy - 6 - methoxy benzamide O C H 3 N H 2 O

O H 2,6 - dimethoxy benzamide 2,6 - dimethoxy benzamide O C H 3

O C H 3 N H 2 O

Oxime metab olite N - [4 - ethyl - 4 - methyl - 3 - nitroso - 1 - hydroxy - 1 - hexenyl] - 2,6 - demethoxy benzamide

Carboxylic acid metabolite N - [1 - carboxyethyl - 1 - methylpropyl] - 2,6 - dimethoxybenzamide

Hydroxylated isoxaben2

1 Suspected to be an artifact formed during acid hydrol ysis. 2 The 3 possible variations of hydroxylated isoxaben are shown above

– Isoxaben - 1 - hydroxy, Isoxaben - 2 - hydroxy, and Isoxaben - 3 - hydroxy. Generic version of hydroxylated isoxaben tentatively identified only in livestock metabolism study.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 36 of 38 Appendix II. Tolerance Assessment Calculations. The dataset used to establish a tolerance for isoxaben on almond hulls consisted of field trial data representing a single application at 1.0 or 1.1 lbs ai/A with 60 - 61 day PHI s, except for the CA5 test site , where the PHI s ranged from 54 - 75 day s (decline study data) . The application rate was 1 x or 1.1 x the proposed maximum seasonal use rate . A 60 - Day PHI is proposed on the label. The residue values used to calculate the tolerance are provided in Table II - 1. The alm ond hulls dataset was entered into the tolerance spreadsheet. Visual inspection of the lognormal probability

plot (Figure II - 1) provided in the spreadsheet indicates that the dataset is not lognormal. The result from the approximate Shapiro - Francia test statistic (Figure II - 2) indicate that the assumption of lognormality should be rejected. Since the data set is flagged as not being reasonable lognormal based on the conclusion of the approximate Shapiro - Francia test statistic, and a visual inspection of the lognormal probability plot indicates the data set are not reasonable lognormal, the “Mean + 3SD method” was used to calculate the tolerance for the almond hull data set. As shown in Figure I I - 3, the recommended tolerance is 0. 4 ppm.Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 37 of 38 Table II - 1. Res idue data used to calculate tolerance for isoxaben on alm ond hulls. Chemical: Isoxaben Crop: Almond hulls (MLE) PHI: 60 - 61 days ( 54 - 75 Days used for CA5 site) App. Rate: 1 lb ai/A MRID Citation: MRID 47140008 Residues of Isoxaben (ppm) 0.042 0 .036 0.01 (LOQ) 0.01 (LOQ) 0.01 (LOQ) 0.0 1 (LOQ) 0.082 0.119 0.087 0.119 0.221 0.229 0.301 0.232 0.156 0.089 Figure II - 1 . Lognorm al probability plot of isoxaben field trial data for alm ond hull s. Lognormal Probability Plot

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 1.0000 0.5000 0.2500 0.1250 0.0625 0.0313 0.0156 0.0078 y = 1.2257x - 2.7523 R 2 = 0.8845

PercentilesConcentrations EPA Isoxaben Almond Hulls 60-61 (54-75 for the CA5 site)Isoxaben Summary of Analytical Chemistry and Resi due Data DP Barcode: D340895

Page 38 of 38 Figure II - 3. Tolerance spreadsheet summary of isoxaben field trial data for almond hulls. Regulator: EPA Chemical: Isoxaben Crop: Almond Hulls PHI: 60-61 (54-75 for the CA5 site) App. Rate: Submitter:

n: 16 min: 0.01 max: 0.30 median: 0.09 average: 0.11 95th Percentile 99th Percentile 99.9th Percentile 0.30 0.35 0.40 (0.35) (0.45) (--) 0.50 1.2 3.5 (1.5) (5.0) (--) 0.45 0.40 0.50 0.8845 0.05 >= p-value > 0.01 : Reject lognormality assumption Approximate Shapiro-Francia Normality Test EU Method I Normal

UCLMedian95th 95/99 Rule EU Method II Distribution-Free Mean+3SD