' 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 /..-,'--(A,_ 12--(:/!J 

James 

Rosanna 

Wolf, 

Louie-Juzwiak, 

Ph.D., Fat~ Scientist 

Risk Assessn

~J( 

fent Process 

W

Leader 

o-"ff /7 0 ~ 

.... Environmental 

Environmental 

Risk 

Fate and 

Branch 

Effects 

III 

Division (7507P) 

~ ~ l'Z-.... 5-!3 

Dana Spatz, Branch Chie~~ t--a.-} s-/1 '3 

Environmental Risk Branch~ 

Environmental Fate and Effects Division (7507P 

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). 

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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 and the correct application rate 

information will be used in the 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 concern) 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 different 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 trifloxysulfuron (CGA-362622) is 

considered stable (100%). Syngenta believes this scenario is overly conservative and 

environmentally unrealistic. 

EFED Response: EFED has reevaluated the conversion factor approach to account for 

the residues of concern proposed in the Problem Formulation, and agrees with Syngenta 

that this approach would be overly conservative. 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 transformation products of 

trifloxysulfuron-sodium are identified as a potential toxicological concern with similar 

toxicity as the parent, these degradates will 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-436664 Adsorption/Desorption: Koc range 

of 650-1,925. (pg 15, Table 8).
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Syngenta Comment: For CGA-382997 adsorption/desorption the correct MRID number 

is 45371821 and the Syngenta report gives a Koc 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 Koc range. For CGA-53052 adsorption/desorption 

the correct MRID number is 45371823. For NOA-436664 adsorption/desorption (MRID 

#45371816), the Syngenta report gives a Koc range of 650-4,717, which 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 corrections for MRIDs 45371821 and 45371823, 

and has confirmed that the omitted Koc 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 application. 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 days after the third 

application in MRID 45371828. 

EFED Response: EFED appreciates the correction noted that CGA-368732 

concentrations were <0.5 ppb (the LOQ) at all 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) IC25 is listed as 0.000009 lb a.i./A for dicot (radish), using dry shoot weight as 

the endpoint. (pg 25).
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Syngenta Comment: The reported IC25/EC25 value (Schwab, 2000, MRID 45371734) is 

0.000046 lb a.i./A (0.0525 g ai/ha) based on shoot dry weight for radish.

EFED Response: EFED appreciates the noted distinction 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 Record for the study states, “The differences 

in EC25 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 (IC25: 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 LD50 for honey bee is listed 

as >25 μg a.i./bee. The acute toxicity classification is listed as practically nontoxic. (pg 

25).

Syngenta Comment: The footnote describing the toxicity 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/eggs 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 editorial and contextual comment. 

10. EPA Preliminary Problem Formulation: The Health Effects Division (HED) 

determined that the residues of concern in drinking water are parent 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") from 
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registered uses of pesticides in registration review. These assessments will be conducted 

in accordance with standard EPA procedures and good scientific judgment. (pg 30). 

Syngenta Comment: Syngenta has submitted a document to the registration review 

docket summarizing the types of refinements that should be considered for an endangered 

species assessment (Risk Assessment Considerations Concerning 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 implementation 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 technical issues related to the development of 

pesticide risk assessments that are compliant with the Endangered Species Act and the 

Federal Insecticide, Fungicide, and Rodenticide Act. In November, the EPA, along with 

the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service 

(NMFS) (collectively, the Services), and the U.S. Department of Agriculture (USDA), 

released a summary of their joint Interim Approaches for assessing risks to listed species 

from pesticides. The Interim Approaches were developed jointly by the Agencies in 

response to the NAS’ recommendations and 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 the Interim Approaches. The Agencies will 

consider public comments on the Interim Approaches 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 Pesticide Endangered Species Act Assessments 

Based on the Recommendations of the National Academy of Sciences April 2013 

Report,” dated November 1, 2013, available at http://www.epa.gov/espp/2013/nas.html.