' UNITED STATES ENVffiONMENTAL PROTECTION AGENCY WASHINGTON D.C.

, 20460

PC Code: 119009 DP Code: 415535 December 5, 2013 MEMORANDUM

Subject:

To:

From:

Through: Environmental Fate and Effects Division's Response to Public Comments on the Registration Review Preliminary Problem Formulation for Trifloxysulfuron-Sodium

Kelly Ballard, Chemical Review Manager Neil Anderson, Branch Chief Risk Management and Implementation Branch I Pesticide Re-evaluation Division (7508P)

Tanja Crk, M.S., Biologist 

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James Wolf, Ph.D

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## ~ Rosanna Louie-Juzwiak, Risk Assessn fe nt Process Leader 

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.... Environmental Risk Branch III

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Dana Spatz, Branch**Chie~~** 

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This document contains the Environmental Fate and Effects Division's (EFED's) responses to
comments received on the Registration Review Preliminary Problem Formulation for the Ecological Risk Assessment for Trifloxysulfuron-Sodium that are within the purview of EFED (e

. g., comments submitted related to the environmental fate, drinking water exposure and ecological assessments). Comments were only received from Syngenta Crop Protection, LLC, which included trifloxysulfuron-specific comments on the preliminary problem formulation, and a report titled Risk Assessment Considerations Concerning the Potential/ Impacts of Pesticides on Endangered Species (Syngenta Report Number TKO 181948) (EPA Docket ID No.: EPA-HQ-OPP-2013-0409). Comment summaries and the Agency's response to comments are below.

1. EPA Preliminary Problem Formulation: Based on the usage report prepared by OPP's Biological and Economic Division, 3000 and 1000 pounds ( ai) of trifloxysulfuronsodium is used per year on com and sugarcane, respectively. (pg 5).



### 12 Syngenta Comment : We believe that the 3000 pound (ai) usage corresponds to cotton instead of corn. Trifloxysulfuron-sodium is not registered for use on corn.

EFED Response : EFED appreciates the comment and the corrected information will be reflected in the preliminary risk assessment.

2. EPA Preliminary Problem Formulation: Uses corresponding to Reg# 100-1134, Spot treatment, Backpack sprayer; A.I. Max App Rate (lb ai/a) 0.02482. (pg 6-7).

Syngenta Comment : ...The directions for use as a spot treatment with backpack sprayer state that 0.0176 oz

. product (0

. 000825 lb. a

. i.) be sprayed per 1000 sq

. ft

. Using a conversion factor of 43

. 56 sq. ft

. per acre, the a

. i. maximum application rate is 0.036 lb./a instead of 0.02482 lb./a.

EFED Response : EFED appreciates the comment a nd the correct application rate information will be used in th e preliminary risk assessment.

3. EPA Preliminary Problem Formulation: To account for the total residues of concern, the conversion factor (from parent compound to all residues of con cern) is, therefore, 2.68. (pg. 9).

Syngenta Comment: The conversion factor (2.68) is expressed as a sum of maximum percent formation fractions for each individual residue of concern ( i.e. 0.61 + 0.54 + 0.53 + 1.0 = 2.68). These values occur at diffe rent sampling times and under different laboratory conditions. CGA-053052 peaks at 61% (hydrolysis at pH 5 after 30 days), CGA-382997 peaks at 54% (aerobic soil metabolism after 365

. days), CGA-368732 peaks at 53% (hydrolysis at pH 7 after 30 days), and parent trifloxy sulfuron (CGA-362622) is considered stable (100%). Syngenta believes this scenario is ove rly conservative and environmentally unrealistic.

EFED Response : EFED has reevaluated the conversion factor approach to account for the residues of concern proposed in the Probl em Formulation, and agrees with Syngenta that this approach would be overly conser vative. Currently, these major degradates ( i.e.
, CGA-053052, CGA-382997 and CGA- 368732) are considered residues of concern in drinking water, and all residues plus the parent will be considered using a total toxic residue (TTR) approach. If any additional environmental transform ation products of trifloxysulfuron-sodium are identified as a pot ential toxicological concern with similar toxicity as the parent, these degradates w ill also be included in the TTR approach.

4. EPA Preliminary Problem Formulation: CGA-382997 Adsorption/Desorption: MRID given was 45371721 and Table 8 Koc range of 15-50

. CGA-53052 Adsorption/ Desorption: MRID given was 4537123. NOA-436 664 Adsorption/Desorption: Koc range of 650-1,925. (pg 15, Table 8).3 Syngenta Comment: For CGA-382997 adsorption/desorptio n the correct MRID number is 453718 21 and the Syngenta report gives a K oc range of 14

. 5-72

. 5

, which includes the CA sandy loam soil results. It appears that the CA sandy loam soil data was inadvertently not included when EPA calculated the K oc range

. For CGA-53052 adsorption/desorption the correct MRID number is 453718 23. For NOA-436664 adsorption/desorption (MRID #45371816), the Syngenta report gives a K oc range of 650-4,717, whic h includes the MS sandy loam soil results. It appears that the MS sandy loam soil data was inadvertently not included when EPA calculated the Koc range

. EFED Response : EFED appreciates the corr ections for MRIDs 45371821 and 45371823, and has confirmed that the omitted K oc values for the respective soils should be included, which will be considered in the preliminary risk assessment.

5. EPA Preliminary Problem Formulation: After the third application, the degradate CGA-382997 in the 0-15 cm depth reached a maximum of 22.8 ppb in the sugarcane plot and 15.3 ppb in the bare ground plot after 90 days

. For CGA-53052

, a maximum of 12.98 ppb was found after 121 days (cropped plot) and 9.91 after 90 days (bare ground plot). (pg 16).

Syngenta Comment: For CGA-382997, the degradate concentration reached a maximum of 22.3 ppb , and CGA-53052 reached a maximum of 9.21 ppb in MRID 45371828.

EFED Response : EFED appreciates the corrections for the maximum percentage formation percentages of CGA-382997 and CGA-053052 in the respective soils. The values Syngenta noted have been confirmed, and will be considered in the preliminary risk assessment.

6. EPA Preliminary Problem Formulation: In California

, the highest amount of a bridge elimination/contraction product (CGA- 368732) in the 0-15 cm depths was 8

. 3 in the cotton plot 21 days after the third applica tion. This product was also the highest in the Louisiana plots (11 ppb 177 days after the third application). (pg 16).

Syngenta Comment: The degradation product CGA-368732 was below the LOQ of 0.5 ppb at all depth intervals (ranging from 0 – 76 centimeters) 177 da ys after the third application in MRID 45371828.

EFED Response : EFED appreciates the corr ection noted that CGA-368732 concentrations were <0.5 ppb (the LOQ) at a ll depths 177 days after the third application, which will be considered in the preliminary risk assessment.

7. EPA Preliminary Problem Formulation: The vegetative vigor study (MRID 45371734) IC 25 is listed as 0.000009 lb a.i./A for dico t (radish), using dry shoot weight as the endpoint. (pg 25).4 Syngenta Comment: The reported IC 25 /

EC 25 value (Schwab

, 2000

, MRID 45371734) is 0.000046 lb a.i./A (0.0525 g ai/ha) base d on shoot dry weight for radish

. EFED Response : EFED appreciates the noted distinc tion between the endpoint cited in the problem formulation and that reported by the study authors. However, the endpoint cited in the problem formulation is consistent with the study reviewers who recalculated the toxicity endpoint. The Data Evaluation R ecord for the study states, “The differences in EC 25 estimates were due to the different statistical methods used to determine these values.” Therefore, the vegetative vigor study (MRID 45371734) endpoint remains as cited in the problem formulation (IC 25 : 0.000009 lb a.i./A or 0.01 g a.i./Ha for radish using dry shoot weight as the endpoint).

8. EPA Preliminary Problem Formulation: The acute contact LD 50 for honey bee is listed as >25 μg a.i./bee

. The acute toxicity classification is listed as practic ally nontoxic. (pg 25).

Syngenta Comment: The footnote describing the toxi city classification should be number 3 instead of number 2.

EFED Response : EFED appreciates the editorial comment.

9. EPA Preliminary Problem Formulation: Footnote 4: However

, there was a statistically significant increase in number of eggs cracked/e ggs laid at 54 mg a.i./kg, but not at 106 or 201 mg a.i./kg . (pg 26).

Syngenta Comment: A reference to footnote No

. 4 is not provided in Table 12

. We believe that footnote No

. 4 references the chronic 1-gen mallard duck reproductive study on page 23.

EFED Response : EFED appreciates the editoria l and contextual comment.

10. EPA Preliminary Problem Formulation: The Health Effects Division (HED) determined that the residues of concern in drinking water are pa rent trifloxysulfuronsodium, CGA-053052, CGA-382997, and CGA-3687337. (pg 29).

Syngenta Comment: No corresponding reference is provided for footnote number 7

. EFED Response : EFED appreciates the editorial comment. 11. EPA Preliminary Problem Formulation: “Consistent with the Agency's responsibility under the Endangered Species Endangered Species Act (ESA), the Agency will evaluate risks to federally listed threatened and/or endangered species (“listed species") from5 registered uses of pesticides in registration review. These assessments will be conducted in accordance with standard EPA procedur es and good scientific judgment. (pg 30).

Syngenta Comment: Syngenta has submitted a document to the registration review docket summarizing the types of refinements th at should be considered for an endangered species assessment ( Risk Assessment Considerations C oncerning the Potential/Impacts of Pesticides on Endangered Species , Syngenta Report Number TK0181948).

EFED RESPONSE: EPA has reviewed the comments from Syngenta on the registration review docket openings for trifloxysulfuron- sodium and plans to address many of the concerns raised by Syngenta as part of the im plementation plan for assessing the risks of pesticides to listed species based on the recommendations of the April 2013 National Academy of Sciences (NAS) report. EPA will address concerns specific to trifloxysulfuron-sodium in connection with the development of its registration review decision for trifloxysulfuron-sodium.

The NAS report, available at http ://www.nap.edu/catalog.php?record_id=18344 , outlines recommendations on specific scientific and tech nical issues related to the development of pesticide risk assessments that are compliant with the Endangered Species Act and the Federal Insecticide, Fungicide, and Rodentic ide Act. In November, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) (collectively, the Services), and th e U.S. Department of Agriculture (USDA), released a summary of their joint Interim A pproaches for assessing risks to listed species from pesticides. The Interim Approaches were developed jointly by the Agencies in response to the NAS’ recommendations a nd reflect a common approach to risk assessment shared by the Agencies as a way of addressing scientific differences between EPA and the Services. The joint Interim Approaches were released prior to the stakeholder workshop held on November 15, 2013. EPA is presenting the joint Interim Approaches at the December 2013 PPDC and SFIREG meetings, allowing additional opportunities for stakeholders to comment on th e Interim Approaches. The Agencies will consider public comments on the Interim A pproaches prior to implementing them. The Agencies intend to jointly implement these approaches as part of a phased iterative process. EPA will refine its listed species risk assessments based on these interim approaches. The details of the joint Interim Approaches are contained in the white paper “Interim Approaches for National-Level Pe sticide Endangered Species Act Assessments Based on the Recommendations of the Na tional Academy of Sciences April 2013 Report,” dated November 1, 2013, available at http://www.epa.gov/espp/2013/nas.html

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