OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460



### October 23, 2014

MEMORANDUM

SUBJECT: Drinking Water Assessment for the Proposed New Use of Sedaxane as a Seed Treatment on Sugar Beet and Cotton PC Code: 129223; DP Barcode: 419976

TO: Cynthia Giles-Parker, Chief Fungicide Branch Registration Division (7505P)

THROUGH: Dana Spatz, Branch Chief Environmental Risk Branch 3 Environmental Fate and Effects Division

FROM: Rochelle F. H. Bohaty Ph.D., Chemist Environmental Risk Branch 3 Environmental Fate and Effects Division (7507P)

PEER REVIEW: Rosanna Louie-Juzwiak, RAPL Environmental Risk Branch 3 Environmental Fate and Effects Division

This memorandum provides a drinking water assessment (DWA) for the proposed registration of sedaxane as a seed treatment on cotton and s ugar beet except sugar beets grown for seed production.

Sedaxane is used to protect agains t certain soil-borne and seed-borne diseases. It is registered for use as a seed treatment for small grain cereals (b arley, wheat, oats, rye and triticale), soybean, canola, corn, sorghum, dried shelled pea and bean (Subgroup 6C; except soybean), rapeseed (subgroup 20A), and potato.

Syngenta is proposing the use of sedaxane as a seed treatment on cott on and sugar beet. The proposed new uses are only included on the label for Sedaxane 500FS/Vibrance TM 

### (A16148C; EPA Reg. No. 100-137)—the single active ingredient formulati on. The proposed application rates for cotton and sugar beet are provide in Table 1 

### . The number of applications of sedaxane that can be applied per year is limited to two. This permits initial planting of sedaxane treated seeds followed by either replanting of treated seeds in the event of crop failure or as part of a crop rotation.

### 2 Table 1. Proposed Sedaxane Application Rates

Crop MaxApp Rate lb a.i./ 100 lb of

seed Max Seeding

Rate a lb seed /A Max Single App Rate lb a.i./A (kg a.i./ha) Max Total App Rate Max Number of AppsPHI (days)bREI (hours)bMRI (days)b Minimum Planting Depth in

Inches Per Year lb a.i./A Per Year lb a.i./A

Cotton 0.02 18.8 c 0.004 (0.004) 0.008 2 NS 12 0 1 (Texas A&M AgriLife extension Sugar beet except those
grown for seed 0.36 4.8 d 0.017 (0.019) 0.034 2 NS 12 0 1 (MSU Extension)

a. The maximum seeding rate was developed based on data provided by BEAD—J. Becker; S. Ratnayake. Acres Planted per Day and Seeding Rates of Crops Grown in the United States
, March 24, 2011

. b. PHI – Preharvest interval; REI – reentry interval; MRI – Minimum retreatment interval

c. 1 lb seed/4,500 seeds x 85,000 seeds/A = 18.8 lb seed/A d. 1 lb seed/22,000 seeds x 104,544 seeds/A (processing sugar beets) = 4.8 lb seed/A NS= not specified



### This DWA takes into account sedaxane (CAS Name: N-[2-[1,1 ′ -bicyclopropyl]-2-ylphenyl]-3- (difluoromethyl)-1-methyl-1H-pyrazole-4-car boxamide CAS No.: 874967-67-6; SYN524464), a mixture of two isomers separately numbered SYN508210 ( trans -isomer of sedaxane) and SYN508211 ( cis -isomer of sedaxane), and two known environmental transformation products of equal toxicological concern, CDCD668094 andC DCD668095. These two chemicals were only observed in aquatic photolysis studi es; therefore, these residues we re only considered as part of the surface water modeling.

Tier I groundwater EDWCs are derived using the most recent version of PRZM-GW (version 1.07) as well as the updated standard scenar ios (March 2014). Previous drinking water assessments conducted for sedaxane have shown th at PRZM-GW Tier I estimates are higher than concentrations estimated usi ng SCI-GROW (Screening Concentr ation in Groundwater, version 2.3) and the FQPA Index Reservoir Screening T ool (FIRST) model. Th erefore, SCI-GROW and FIRST runs were not completed for this assessmen t. No monitoring data are available at this time, as sedaxane was only recently registered in the United States.

Seed treatment use of sedaxane on sugar beet and cotton are not e xpected to result in concentrations higher than previously reported for seda xane potato seed treatments 1 

### (the highest peak and post breakthrough EDWCs were 15.1 μ g/L and 13.0 μ g/L, respectively). PRZM-GW EDWCs resulting from sedaxane use on potato ar e recommended for use in the human health risk assessment.

1 U.S. Environmental Protection Agency, Bohaty, R., Hetric k, J. Drinking Water Assessment for the Proposed New Use of Sedaxane as a Seed Treatment on Corn, Sorghum, Dried Shelled Pea and Bean (Subgroup 6C; except soybean), Rapeseed (subgroup 20A), and Potato PC Code: 129223; DP Barcodes: 405391 and 407956

### 3 Table 2. Results Summary: EDWCs fo r Total Toxic Sedaxane Residues

Assessment Tier/

Model Crop Sedaxane Total Toxic Sedaxane Residues

Comments Acute Peak EDWC
μ g/L (ppb) Chronic/Cancer Yearly Mean μ g/L (ppb) Acute Peak EDWC

μ g/L (ppb) Chronic/Cancer Yearly Mean μ g/L (ppb)

Tier I/ FIRST a Potato 4.1 1.2 Values taken from previously conducted DWA b

Tier I/ PRZM-GW Potato 15.1 13.0 c Values are taken from the previously conducted DWA b for WI Central Sands. Assumed two sedaxane application every year. Tier I/ PRZM-GW Sugar beet 8.9 8.4 c NC Eastern Coastal Plain.

a. Surface water EDWCs have been correct ed for a percent cropped area (PCA) of 0.91. b. See footnote 1

c. Post breakthrough average

### 4 ATTACHMENT 1: Groundwater Modeling

Groundwater analysis was completed using PRZM-GW. Input values used in the model runs for PRZM-GW are summarized in Table A1.1 . Standard scenarios, appli cation interval, and data of the first application are provided in Table A1.2 . Rationale for choosing each input parameter is provided in previous drinking water assessments 1



### . Table A1.1 Input Parameters Used in PRZM-GW Modeling to Estimate Sedaxane Concentrations Resulting From the Proposed Uses on Cotton and Sugar Beet

Input Parameter

(Symbol; Unit) Value for Sedaxane (parent only) Reference Comment
Hydrolysis (t 1/2 ; days)] 0 47473318/ Acceptable

Aerobic Soil (t 1/2 ; days)] 1298 days 47473448/ Supplemental Previous input value used based on SFO kinetics is 415 days. Value derived from soil studies only. Representative half-life values used to derive the model input value were developed following the NAFTA kinetics guidance. Average Soil Partition Coefficient K foc = 481 mL/g K oc = 537mL/g 47473461/ acceptable

### 5 Table A1.2. PRZM-GW Representative Model Scenarios

Use Number of Applications/

Application Rate

(kg a.i./ha) Interval Between Applications (days) Application Date(s) Scenario a /

Weather

cotton 2/0.004 30 b 7 days preemergence and 30 days post
emergence a,b NC Eastern Coastal Plain/ W13722

WI Central Sands/ W14920

Delmarva/ W13781

GA Coastal Plain/ W93805

FL Central Ridge/ W12842

FL Jacksonville/ W13889 sugar beet 2/0.019 30 c 7 days preemergence and 30 days post
emergence a,b

a. March 2014 Scenarios were used in model simulations. b. Assumed planting date 7 days prior to emergence date and 30 day retreatment interval in the event of crop failure

c. For FL Central Ridge scenario assumed application on emergence date and 30 post emergence na = not applicable



### PRZM-GW Tier I groundwater EDWC s for sedaxane resulting from the proposed sedaxane uses on cotton and sugar beet are highlighted in Table A1.3 

### . Peak and post breakthrough average EDWCs in groundwater resulting fr om the proposed sedaxane uses are not expected to be > 8.9
μ g/L and 8.4 μ g/L, respectively. These estimates were derived based on the proposed sugar beet use. Model outputs indicate that the time to breakthrough (the time it takes for sedaxane residues to reach the underground aquifer) ranges from 5557 to 11066 days depending on the scenario. These EDWCs are lower than previously report ed for potatoes (one applications every 24 months). 1

### 6 Table A1.3. Tier I PRZM-GW EDWCs for Sedaxane From the Proposed Uses Proposed Uses on Corn, Sorghum, Dried Shelled Pea and Bean ( Subgroup 6C; Except Soybean), Rapeseed (Subgroup 20A), and Potato

Crop Sedaxane Scenario Peak (μg/L) Post-Breakthrough Average (μg/L) Days to Breakthrough

cotton 1.7 1.5 8830 WI Central Sands a

0.5 0.4 9188 GA Coastal Plain

1.9 1.8 6403 NC Eastern Coastal Plain

1.4 1.2 6736 Delmarva

1.5 1.4 5557 FL Central Ridge

0.4 0.4 11066 FL Jacksonville b

sugar beet 8.2 7.0 8830 WI Central Sands a

2.3 2.0 9188 GA Coastal Plain

8.9 8.4 6403 NC Eastern Coastal Plain

6.6 5.6 6736 Delmarva

7.1 6.6 5557 FL Central Ridge

1.8 1.7 11066 FL Jacksonville b

Bold font indicates highest value

a. Canopy height corrected to 300 cm b. Extended weather file used ( i.e. , simulation completed for 100 years)