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 sugar beet except sugar beets grown for seed 

production. 

Sedaxane is used to protect against certain soil-borne and seed-borne diseases. It is registered for 

use as a seed treatment for small grain cereals (barley, 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 cotton and sugar beet. The 

proposed new uses are only included on the label for Sedaxane 500FS/VibranceTM (A16148C; 

EPA Reg. No. 100-137)—the single active ingredient formulation. 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 

Ratea 

lb seed /A 

Max Single 

App Rate 

lb a.i./A 

(kg a.i./ha) 

Max Total 

App Rate 

Max 

Number 

of Apps

PHI (days)b

REI (hours)b 

MRI (days)b 

Minimum 

Planting 

Depth in 

Inches Per Year 

lb a.i./A 

Per Year 

lb a.i./A 

Cotton 0.02 18.8c 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 4.8d 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-carboxamide 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 andCDCD668095. These two chemicals were only 

observed in aquatic photolysis studies; therefore, these residues were 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 scenarios (March 2014). Previous drinking water 

assessments conducted for sedaxane have shown that PRZM-GW Tier I estimates are higher than 

concentrations estimated using SCI-GROW (Screening Concentration in Groundwater, version 

2.3) and the FQPA Index Reservoir Screening Tool (FIRST) model. Therefore, SCI-GROW and 

FIRST runs were not completed for this assessment. 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 expected to result in 

concentrations higher than previously reported for sedaxane potato seed treatments1

 (the highest 

peak and post breakthrough EDWCs were 15.1 μg/L and 13.0 μg/L, respectively). PRZM-GW 

EDWCs resulting from sedaxane use on potato are recommended for use in the human health 

risk assessment. 

 

1 U.S. Environmental Protection Agency, Bohaty, R., Hetrick, 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 for Total Toxic Sedaxane Residues 

Assessment 

Tier/ 

Model 

Crop 

Sedaxane Total Toxic Sedaxane 

Residues 

Acute Comments 

Peak 

EDWC 

μg/L (ppb)

Chronic/Cancer 

Yearly Mean μg/L 

(ppb) 

Acute 

Peak 

EDWC 

μg/L 

(ppb)

Chronic/Cancer 

Yearly Mean μg/L 

(ppb) 

Tier I/ 

FIRSTa Potato 4.1 1.2 Values taken from 

previously conducted DWAb 

Tier I/ 

PRZM-GW Potato 15.1 13.0c 

Values are taken from the 

previously conducted DWAb

for WI Central Sands. 

Assumed two sedaxane 

application every year. 

Tier I/ 

PRZM-GW Sugar beet 8.9 8.4c NC Eastern Coastal Plain. 

a. Surface water EDWCs have been corrected 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, application 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 assessments1. 

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 (t1/2; 

days)] 0 47473318/ Acceptable 

Aerobic Soil (t1/2; 

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 

Kfoc = 481 mL/g 

Koc = 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) 

Scenarioa/ 

Weather 

cotton 2/0.004 30b 

7 days preemergence and 30 

days post 

emergencea,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 30c 

7 days preemergence and 30 

days post 

emergencea,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 EDWCs 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 from the proposed sedaxane uses are not expected to be > 8.9 

μg/L and 8.4 μg/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 reported 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 

Peak Scenario 

(μg/L) 

Post-Breakthrough Average 

(μg/L) Days to Breakthrough 

cotton 

1.7 1.5 8830 WI Central Sandsa 

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 Jacksonvilleb 

sugar beet 

8.2 7.0 8830 WI Central Sandsa 

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 Jacksonvilleb 

Bold font indicates highest value 

a. Canopy height corrected to 300 cm 

b. Extended weather file used (i.e., simulation completed for 100 years)