UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY AND PO LL U T IO N PREVENTION
PC Code: 125203 DP Barcode: 409558

May 2, 2013

MEMORANDUM

SUBJECT :

TO:

FROM:

THRU: The Environmental Fate and Effects Division Response to Comments Posted to the Registration Review Docket for Clodinafop-propargyl; Docket ID EPA-HQ-OPP-2012- 0424.

Wilhelmena Liv i ngston Chemical Review Ma nager Pesticide Re-eva luatio n Div i sion (7508P)

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Melanie Biscoe, Environmental

# Pro~~tion**Specialist ~~**  Tanja Crk, Biologist

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### S/'2-/(3 Environmental Risk**Branch~** Environmental Fate and Effects D i vision (7507P)

Dana Spatz; Branch Chie**:c::;:~~ibt!~** Rosanna Louie-Juzwiak, Risk As**.r;:;:~ot_:~** Environmental Risk Branch 3 Environmental Fate and Effects Division (7507P)

This document conta ins the Environmental Fate and Effects Division's (EFED) response to comments on the Clodinafop-propargyl Problem Formulat i on (Docket ID EPA-HQ-OPP-2012-0931). Other than the corrected Koc value pointed out by Syngenta, which indicates greater mobility than originally stated in the P ro b l em Formulation, none of the public comments w i ll mater ially impact the ecologica l risk or drinking water exposu r e assessments to be completed in Registration Review.

COMMENT SOURCE : SVNGENTA

EPA Statement Page 2, Section 1, Table 1 Percent Crop Treated for wheat: Avg: 5, Max: 10. Syngenta Comment 1: Syngenta believes the Percent Crop Treated for wheat should be 7.4 (average) and 15.1 (max i mum).

EFED Response 1: EFED defers questions about use or usage to the Bio l ogical and Economic Analysis Divis ion

.

Page 1 of 6Page 2 of 6 EPA Statement Page 3, Table 2, application Method Timing, WHEAT, (6.4% a.i., Emulsifiable Concentrate) Stated application method timing was Foliar, Tillering.

Syngenta Comment 2 : Syngenta would like to respectfully revise Foliar to Foliar, Post

emergence. EFED Response 2 : EFED defers questions about use or usage to the Biological and Economic Analysis Division.

EPA Statement Page 4, Section 2.2, paragraph 1, 1st
sentence “...drinking water EECs....”.

Syngenta Comment 3 : Syngenta would like to respectfully revise EECs to EDWCs. EFED Response 3 : EFED acknowledges that "EDWCs" should be used in place of "EECs" in this
context.

EPA Statement Page 4, Section 2.2, paragraph 1, 2nd
sentence In this DWA, the surface water values were modeled using PRZM EXAMS based on the North Dakota wheat scenario....”.

Syngenta Comment 4 : Syngenta would like to respectfully revise to add “based on the North Dakota and Oregon wheat scenarios...”. Values (1

- in

- 10 year annual Mean) cited in Table 4 (page 4) were derived from the Oregon wheat scenario (2006 EPA DWA, DP324688).
EFED Response 4 : EFED acknowledges that the Oregon wheat scenario should be added to the sentence as indicated by Syngenta. The PRZM

- EXAMS Oregon wheat scenario resulted in a 1

- in

- 10 year annual mean surface water EDWC of 2.5 μg/L, as indicated in Table 4 of the Problem Formulation (2006 EPA DWA, DP324688).

EPA Statement Page 7, Table 5, Degradation Product Formation in Environmental Fate Studies For degradation product CGA

- 193469, Study

- Aerobic Soil, the maximum percentage formed is stated as 79.9% of applied (2 hours).Page 3 of 6 Syngenta Comment 5 : Syngenta believes the actual percentage formed for the degradate, CGA

- 193469 is 79.7% of applied (2 hours). EFED Response 5 : EFED agrees that with Syngenta that, based on data from aerobic soil metabolism study MRID 46012931, the maximum percentage formed is 79.7% of applied (as an average of two samples at hour 2 of the study).

EPA Statement Page 7, Table 5, Degradation Product Formation in Environmental Fate Studies For degradation product CGA

- 193468, Study

- Aerobic Soil, the maximum percentage formed is stated as 10.7% of applied (3 days).

Syngenta Comment 6 : Syngenta believes the actual percentage formed for the degradate, CGA

- 193468 is 5.4% of applied (3 days). EFED Response 6 : Based on data presented in aerobic soil metabolism study MRID 46012931, the maximum percentage formed for degradation product CGA

- 193468 is 10.7% of applied (as an average of two samples on day 3). Based on the latter data and anaerobic aquatic metabolism data (as referenced in Table 5 of the Problem Formulation), EFED considers CGA

193468 to be a major degradate of clodin a fop

- propa rgyl.

EPA Statement Page 8, 4. Receptors “Table 7 and Table 7 provide a summary.....” . Syngenta Comment 7 : Syngenta believes that the reference should be Table 6 and Table 7. EFED Response 7 : EFED agrees with Syngenta's editorial comment regarding Table 6 and Table 7.

EPA Statement Page 8, 4.1 Effects to Aquatic Organisms, paragraph 1, 4th
sentence “A comparison of non

- vascular aquatic plant data suggests that the green algae ( S. subspicatus ) is less sensitive to the degradate CGA

302371 than it is to the parent...”.

Syngenta Comment 8 : The alga tested in the study with the CGA

- 302371 metabolite was Pseudokirchneriella subcapitata ( Selenastrum capricornutum ) rather than S. subspicatus . Table 6 (page 9) and Appendix E (page 43) also list S. subspicatus rather than P subcapitata

. P. subcapitata was less sensitive to the degradate CGA

- 302371 (MRID 44399161) than to the parent compound (MRID 44561104). In addition, Syngenta will submit additional algal data for the primary degradate, CGA

- 193469, by the end of 1st Quarter 2013.Page 4 of 6 EFED Response 8 : Syngenta pointed out that the study cited in the problem formulation was not referencing the correct species. Indeed, the algae study, MRID 44399161, using the metabolite CGA

- 302371 as the test compound, u sed Selenastrum capricornutum (new name: Pseudokirchneriella subcapitata ) and not Scenedesmus subspicatus . The text (paragraphs in section 4.1 and Appendix E, and Table 6) where this species is cited under this MRID number is an error in the problem formulation; however, the conclusions from the study are the same and the sentence pointed out should read as follows: “A comparison of non

- vascular aquatic plant data suggests that the green algae ( S. capricornutum ) is less sensitive to the degradate CGA

- 30237 1 than it is to the parent...”

EPA Statement Page 13, 5. Conceptual Modal, paragraph 1, 4th
sentence “Clodinafop acid and its transformation products are persistent,...”.

Syngenta Comment 9 : Under aerobic conditions, metabolites CGA

- 193469, CGA

- 302371 and CGA

- 193468 degrade with half

- lives of 1 to 2.4 days (MRID 46012931 and 46012930), 11 days (MRID 46012930) and 1.1 days (MRID 46012931), respectively. Therefore, Syngenta believes that the transformation products of clodinafop are not persistent to pers istent, depending on the environment. EFED Response 9: EFED agrees that clodinafop acid and its transformation products are not persistent to persistent, depending on the environment. Regardless of the individual half

- lives of clodinafop

- propargyl transformation products, EFED will use the half

- life of the totality of the toxic residues identified in the Problem Formulation for the Preliminary Ecological Risk and Drinking Water Assessments for registration review.

EPA Statement Page 15

- 16, Table 8, Vapor Pressure and Aqueous Solubility The referenced source for these studies is MRID 44399101.

Syngenta Comment 10 : Syngenta believes the referenced source should be MRID 44399103. EFED Response 10 : EFED agrees that MRID 44399103 is the appropriate source for data concerning the aqueous solubility and vapor pressure of clodinafop

- propargyl.

EPA Statement Page 16, Table 8, Anaerobic Aquatic The referenced source for this study (MRID 46012933) was in duplicate. Syngenta Comment 11 : Syngenta believes the referenced sources should be MRID 46012933 and 44399177.Page 5 of 6 EFED Response 11 : EFED agrees that MRID 44399177 is the appropriate source for data concerning anaerobic aquatic metabolism, in addition to MRID 46012933.

EPA Statement Page 16, Table 8, Mobility The Koc values for metabolite CGA

- 193468 are stated as (average of “..........832, 2133, 647, 998, 718, 577”) (MRID 46012936). Syngenta Comment 12 : The study report (MRID 46012936) cites Koc adsorption values for metabolite CGA

- 193468 as 289, 630, 363, 378, 367 and 352. EFED Response 12 : EFED acknowledges that MRID 46012936 reports adsorption K f oc values for metabolite CGA

- 193468 as 289, 630, 363, 378, 367 and 352. The K f oc values for CGA

- 193468 that EFED listed in Table 8 were the d esorption K f oc values for this metabolite reported in MRID 46012936. Because EFED uses the adsorption K f oc values to estimate exposure, the average Koc value that should be listed in Table 8 on Page 16 of the Problem Formulation is 144.4. EFED intends to use this average Koc value in the Preliminary Ecological Risk and Drinking Water Assessments for registration review.

EPA Statement Page 19, Section 7.1, Environmental Fate, Table 9, Submitted Studies (MRID) For OCSPP Guideline 835.4100, Aerobic Soil Metabolism, MRID 46012931 is cited in duplicate.

Syngenta Comment 13 : Syngenta believes that one of the references should be MRID No. 46012930. EFED Response 13 : EFED agrees that the duplicate entry for MRID 46012931 should be MRID 46012930.

EPA Statement Page 19, Section 7.1, Environmental Fate, Table 9, Submitted Studies (MRID) For OCSPP Guideline 835.4400, Anaerobic Aquatic Metabolism, MRID 4399176.

Syngenta Comment 14 : Syngenta believes that the reference should be MRID No. 44399176. EFED Response 14 : EFED agrees that this reference should be should be MRID 44399176.

EPA Statement Page 28, Appendix A, EFED Label Data Report Reg# 100

- 907, the Original (Product/A.I.) Max App Rate is listed as “1 unspecified”. Syngenta Comment 15 : The maximum application rate for Discover Herbicide (EPA Reg. No. 100

- 907) is 4 fl oz/A. EFED Response 15 : See EFED Response 16 below.Page 6 of 6 EPA Statement Page 28, Appendix A, EFED Label Data Report Reg# 100

- 907, the A. I. Max App Rate is listed as NDC, No Dosage Conversion. Syngenta Comment 16 : The active ingredient (A.I.) maximum application rate for Discover Herbicide (EPA Reg. No. 100

- 907) is 0.0625 lb/A. EFED Response 16 : Based on the information provided on the Discover Herbicide product (EPA Reg. No. 100

- 907) label approved November 23, 2009, ( i.e., product contents of 2 lb active ingredient (a.i.) per gallon, maximum single application rate of 4 fl oz per acre) EFED agrees that the maximum single application rate for this product is 0.0625 lb a.i./acre.

EPA Statement Page 31, Appendix A, Screening Level Estimates of Agricultural Uses of Clodinafop

propargyl Percent Crop Treated for Wheat: Avg: 5, Max:10.

Syngenta Comment 17 : Syngenta believes the Percent Crop Treated for wheat should be 7.4 (average) and 15.1 (maximum). EFED Response 17 : EFED defers questions about use or usage to the Biological and Economic Analysis Division.