U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460

 

OFFICE OF PREVENTION, 

PESTICIDES AND TOXIC 

SUBSTANCES

PC Code: 123802

DP Code: 373599, 373601

March 2, 2010

MEMORANDUM

SUBJECT: Drinking Water Assessment for Fomesafen Use on Pepper

TO: Michael Walsh

Joanne Miller, PM 23

Registration Division (7505P) 

 

FROM: James Lin, Environmental Engineer

Environmental Risk Branch I

Environmental Fate and Effects Division (7507P)

 

APPROVED Anita Pease, Acting Branch Chief

BY: Environmental Risk Branch I

Environmental Fate and Effects Division (7507P)

Summary

This assessment provides estimated drinking water concentrations (EDWC) of the 

herbicide fomesafen in surface water and in ground water in support of the human health 

risk assessment for assessing of new use on pepper (DP373599, 373601). This drinking 

water exposure memo addresses the human exposure of fomesafen through ingestion of 

drinking water from the new proposed use. Based on the modeling analysis, the 1- in-10 

year fomesafen concentration in surface-source drinking water is not expected to exceed 

25.53 μg/L for peak (acute) and 2.87 μg/L for annual average (non-cancer chronic)

exposures. The 30-year annual average concentration is not expected to exceed 1.20

μg/L (cancer chronic). Therefore, the current EDWCs will not supersede the 

recommended drinking water values previously performed for this chemical (DP 

322213), and the previous drinking water values should be used.
2

Estimated Drinking Water Concentrations (DP 322213)

Food uses of fomesafen considered in the previous assessment are cotton and soybeans. 

Environmental fate data indicate fomesafen is very mobile and highly persistent in 

terrestrial and aquatic environments. Major routes of dissipation from the application site 

are expected to be runoff and leaching. These data suggest fomesafen occurrence in 

surface water and groundwater should be anticipated. The 1- in-10 year fomesafen 

concentration in surface-source drinking water is not expected to exceed 34.8 μg/L for 

peak and 13.1 μg/L for annual average exposures. The 30-year annual average 

concentration is not expected to exceed 6.5 μg/L. Although SCI-GROW modeling 

predicts a fomesafen concentration in ground water of 11.2 μg/L, a prospective ground 

water monitoring study for soybeans on a vulnerable North Carolina site reported

maximum concentrations of fomesafen in ground water of 1 μg/L. EFED recommends 

using the ground water monitoring concentration of 1 μg/L as the benchmark 

concentration for fomesafen in ground water source drinking water because it represents 

actual use conditions of fomesafen on soybeans on a vulnerable soil. 

Label Use Information

Based on the proposed Reflex ® Herbicide label (EPA Reg. No. 100-993), application 

rates and intervals for the new use of fomesafen on pepper vary based on geographical 

regions as shown as Table 1. 

Table 1 Label Application Rates and Intervals for Fomesafen Use on Pepper1

Region States in Region App Rate 

(lbs/A) Application Interval

1

AL, AR, FL, GA, LA, MS, 

MO2, NC, OK2, SC, TN, 

TX2

0.375 1 year

2

DC, DE, IL2, IN2, KY, MD, 

OH2, PA3, WV, VA, 0.375 2 year

3

CT, IA, ME, MA, MI

3

, NH, 

NJ, NY, PA3, RI, WI, VT 0.313 2 year

4

KS2, MI3, MN2, ND3, NE2

SD3, WI2 0.25 2 year

5 ND3, MN3, SD30.1875 2 year

1REFLEX 2.5 Gallon (EPA Reg. No. 100-993)

2Does not include entire state

3

Portions of state are in multiple regions

Among the five regions, region 1 allows the highest application amount as it has a higher 

rate and a shorter application interval. The use on pepper is specified as a preplant nonincorporated pre-emergence broadcast application.
3

Environmental Fate Summary

Major routes of fomesafen dissipation are leaching, runoff, and microbial degradation. 

Because fomesafen is persistent and mobile in soil, it is expected to move from the 

application site into groundwater and surface water. Additionally, off-site movement of 

fomesafen is expected through spray drift from aerial and ground spray. The high 

persistence of fomesafen is expected to contribute to year-to-year accumulation in 

terrestrial and aquatic environments. 

Fomesafen is stable to abiotic hydrolysis. It undergoes slow photodegradation in water

(t1/2= 49 to 289 days). Fomesafen is persistent (t1/2=9 to 99 weeks) in aerobic soil and 

aquatic environments. However, it degrades rapidly (t1/2< 20 days) in anaerobic 

environments. The major degradation product of fomesafen is 5-(2-chloro-,,-

trifluoro-p-tolyloxy)-N-methylsulphonyl-panthranilamide (fomesafen amine). A minor 

degradation product is 5-(2-chloro-,,-trifluoro-p-tolyloxy) anthranilic acid 

(fomesafen amino acid). Neither degradate has been identified as a toxicological 

concern. 

Fomesafen is expected to be very mobile in soil. Simple partitioning coefficients range 

from 0.51 in loamy coarse sand to 2.45 in sandy clay loam soil. Regression analysis 

indicates fomesafen sorption is not dependent on soil organic matter content. Aged soil 

column leaching studies indicate degradation products of fomesafen are not mobile in 

soils; less than 0.06% of applied radioactivity was detected in the leachate samples.

Field dissipation studies in NC, IL, MS, AR, AL, TX, LA, SD, MN, KY, IA and MO 

indicate fomesafen is moderately persistent to persistent (t1/2= 50 to 150 days ) in surface 

soils under actual use conditions. Fomesafen was detected at depths up to 30 inches in 

the soil profile. Fomesafen amine was the only degradation product identified in field 

dissipation studies. Prospective ground water monitoring in NC indicates fomesafen 

moved through the soil profile into medium and deep ground water. 

Fomesafen has a low potential for bioaccumulation in fish tissues. Bioaccumulation 

factors for fomesafen were 0.7 for whole fish, 0.2 for edible tissues, and 5.2 for nonedible 

tissue. Bioaccumulated residues were depurated during a 14-day depuration period. 

Surface Water Assessment

The new proposed pepper use of fomesafen was modeled in the Florida scenario in 

PRZM/EXAMS using index reservoir (IR) scenarios with the default percent crop area 

(PCA) adjustment factor. The estimated drinking water concentrations in surface water 

were derived from Tier II PRZM (Pesticide Root Zone Model; Version 3.12.2, May 12, 

2005) and EXAMS (Exposure Analysis Modeling System; Version 2.98.04.06, Apr. 25, 

2005). PRZM simulates pesticide transport as a result of runoff, erosion, and off-target 

spray drift from an agricultural field. EXAMS estimates environmental fate and transport 

of pesticides in surface water. Additionally, a graphical interface shell, PE5.pl (dated 
4

7/27/2007), was employed to facilitate the input of use-specific information in the PRZM 

input and the EXAMS chemical files (Table 2). 

Linked crop-specific scenario and meteorological data were used to estimate exposure as 

a result of fomesafen use on pepper. Simulations were done using the index reservoir in 

EXAMS, which is a surrogate for a permanent surface water drinking water environment. 

Weather and agricultural practices were simulated over 30 years to estimate the 1-in-10 

year exceedance probability at the site. 

Table 2. Input Parameters for PRZM-EXAMS Modeling of Fomesafen on Pepper.

Parameter Value Reference

Selected Physical/Chemical Properties

Molecular Weight (g/mol) 420 EPA 2020220

Water Solubility (mg/L) 1200 (pH 7, 20oC) MRID 45048207

Vapor pressure (25C) <7.5 x10-7 mmHg (50oC) HSDB

Henry's Law Constant 7.5 x 10-13 atm m3/mol (estimated) HSDB

Persistence

Hydrolysis t1/2 @ pH 7 stable Acc No. 071059

Photolysis t1/2 in Water 289 days in pH 7 buffer solution MRID 40451101

Soil metabolism

Aerobic t1/2

24-25C (days)

loamy sand (Frensham) 187. 6 and 630

sandy loam/loam (18 acres) 57 and 693

Calcareous silty clay loam (Gore) 349.3 

and 527.1 

silty clay loam (Wisborough green) 207

upper 90th percentile of mean= 428.8 

days

mean=387.84 days and SD=242.90 days 

Acc No. 071059 and 

00135660

Aquatic metabolism Aerobic 

t1/2 (days)

loamy sand (Frensham) 139.3 

sandy loam/loam (18 acres) 60.9

Calcareous silty clay loam (Gore) 92.4 

silty clay loam (Wisborough green) 115.5 

upper 90th percentile of mean= 115.71 

days

mean=102.02 days and SD=33.44 days

Acc No. 72158

Aquatic metabolism 

Anaerobic t1/2

Silt loam soil from Illinois half-life in the 

total system: 4.0 days

Loam soil from Mississippi half-life in 

the total system: 3.6 days 

Sand soil from North Carolina half-life in 

the total system: 5.1 days 

MRID 47865308
5

Parameter Value Reference

upper 90th percentile of mean= 5.08 days

mean= 4.233 days and SD= 0.777 days

Mobility/Adsorption-Desorption

Mobility -

Adsorption/Desorption Aged

(Guideline 163-1)

Blount silt loam-0.68. This value 

represents the lowest non-sand Kd. The 

Koc partition model was not used because 

there was no correlation between SOC 

and Kf . 

Acc No 259413

Application Parameters

Application Efficiency Aerial (0.95); Ground (0.99) Input Guidance 

Document Spray Drift Amount Aerial (0.15); Ground (0.064)

The application rate used is the recommended maximum label application rate. The 

standard scenarios were developed by EFED to represent nationwide crop coverage and 

high-end vulnerability sites to runoff and erosion and, therefore, pesticide transport. The 

application information used in the PRZM/EXAMS modeling is provided in Table 3.

Table 3. Standard EFED modeling scenario for fomesafen pepper use

PRZM 

Crop 

Scenario

Application Date

dd-mm

Maximum Single Application

Rate (lb ai/A)

Pepper

Florida Pepper 20-08 0.375 / year

The modeling results of estimated drinking water concentrations (EDWC) are listed in 

Tables 4 (before PCA adjustment) and 5 (after PCA adjustment). The default PCA value

of 0.87 is adjusted for pepper use. The complete PE5 outputs are included in the 

Appendix.

Table 4. Estimated Drinking Water Concentrations before Percent Crop Area 

(PCA) Adjustment 

PRZM 

Crop 

Scenario

1 in 10 year annual 

peak concentration 

(acute) 

1 in 10 year annual 

mean concentration 

(non-cancer chronic)

30 year annual mean 

concentration (cancer 

chronic). 

Pepper (unit: μg/L; ppb)

Florida Pepper: aerial 29.349 3.294 1.376

Florida Pepper: ground 29.253 3.257 1.259
6

Table 5. Estimated Drinking Water Concentrations after Percent Crop Area (PCA) 

Adjustment 

PRZM 

Crop 

Scenario

1 in 10 year annual 

peak concentration 

(acute) 

1 in 10 year annual 

mean concentration 

(non-cancer chronic)

30 year annual mean 

concentration (cancer 

chronic). 

Pepper (unit: μg/L; ppb)

Florida Pepper: aerial 25.534 2.866 1.197

Florida Pepper: ground 25.450 2.834 1.095

The aerial application has the higher estimated drinking water concentrations. The 1 in 

10 year annual peak concentration of 25.53 μg/L should be used to assess acute concerns;

the 1 in 10 year annual mean concentration of 2.87 μg/L should be used for non-cancer 

chronic assessment; and the 30 year annual mean concentration of 1.20 μg/L should be 

used for assessing cancer chronic concerns. 
7

Appendix 

stored as frflpdwa.out

Chemical: Fomesafen

PRZM environment: FLpeppersSTD.txt modified Thuday, 24 May 2007 at 

09:44:22

EXAMS environment: ir298.exv modified Tueday, 26 August 2008 at 

05:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 05:14:22

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 6.432 6.115 4.997 3.413 2.653 0.7136

1962 5.081 4.832 3.954 2.807 2.204 0.6318

1963 9.879 9.391 7.947 5.392 4.171 1.154

1964 29.92 28.45 23.31 15.58 12.06 3.325

1965 2.658 2.527 2.06 1.383 1.069 0.4647

1966 14.91 14.19 12.38 8.472 6.569 1.787

1967 2.639 2.514 2.16 1.513 1.177 0.4084

1968 7.881 7.602 6.291 4.719 3.734 1.029

1969 6.786 6.458 5.457 3.819 2.988 0.8661

1970 13.64 12.97 10.58 7.066 5.467 1.516

1971 7.031 6.824 5.768 3.987 3.125 0.9179

1972 5.502 5.285 4.378 2.942 2.267 0.6455

1973 3.152 3.004 2.813 2.005 1.559 0.4464

1974 5.754 5.482 4.548 3.126 2.435 0.6757

1975 4.053 3.865 3.432 2.365 1.833 0.5246

1976 3.421 3.258 2.926 2.313 1.836 0.5224

1977 7.529 7.16 6.392 4.376 3.41 0.9471

1978 3.662 3.509 2.916 2.239 1.79 0.535

1979 6.78 6.452 5.369 3.644 2.962 0.8417

1980 39.62 37.68 31.34 21.05 16.25 4.405

1981 24.21 23.02 19.72 13.37 10.33 3.016

1982 3.988 3.793 3.122 2.147 1.66 0.5832

1983 4.413 4.194 3.529 2.462 1.919 0.5384

1984 18.6 17.9 15.49 10.56 8.175 2.219

1985 7.165 6.874 5.716 3.884 3.058 0.9352

1986 5.706 5.425 4.619 3.314 2.575 0.7341

1987 3.081 2.962 2.496 2.077 1.655 0.483

1988 81.19 77.2 62.89 41.6 31.98 8.55

1989 8.825 8.388 7.167 4.949 3.833 1.411

1990 3.137 2.982 2.622 1.954 1.526 0.4598

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.032258064516129 81.19 77.2 62.89 41.6 31.98 8.55

0.0645161290322581 39.62 37.68 31.34 21.05 16.25 4.405

0.0967741935483871 29.92 28.45 23.31 15.58 12.06 3.325

0.129032258064516 24.21 23.02 19.72 13.37 10.33 3.016

0.161290322580645 18.6 17.9 15.49 10.56 8.175 2.219

0.193548387096774 14.91 14.19 12.38 8.472 6.569 1.787

0.225806451612903 13.64 12.97 10.58 7.066 5.467 1.516

0.258064516129032 9.879 9.391 7.947 5.392 4.171 1.411

0.290322580645161 8.825 8.388 7.167 4.949 3.833 1.154
8

0.32258064516129 7.881 7.602 6.392 4.719 3.734 1.029

0.354838709677419 7.529 7.16 6.291 4.376 3.41 0.9471

0.387096774193548 7.165 6.874 5.768 3.987 3.125 0.9352

0.419354838709677 7.031 6.824 5.716 3.884 3.058 0.9179

0.451612903225806 6.786 6.458 5.457 3.819 2.988 0.8661

0.483870967741936 6.78 6.452 5.369 3.644 2.962 0.8417

0.516129032258065 6.432 6.115 4.997 3.413 2.653 0.7341

0.548387096774194 5.754 5.482 4.619 3.314 2.575 0.7136

0.580645161290323 5.706 5.425 4.548 3.126 2.435 0.6757

0.612903225806452 5.502 5.285 4.378 2.942 2.267 0.6455

0.645161290322581 5.081 4.832 3.954 2.807 2.204 0.6318

0.67741935483871 4.413 4.194 3.529 2.462 1.919 0.5832

0.709677419354839 4.053 3.865 3.432 2.365 1.836 0.5384

0.741935483870968 3.988 3.793 3.122 2.313 1.833 0.535

0.774193548387097 3.662 3.509 2.926 2.239 1.79 0.5246

0.806451612903226 3.421 3.258 2.916 2.147 1.66 0.5224

0.838709677419355 3.152 3.004 2.813 2.077 1.655 0.483

0.870967741935484 3.137 2.982 2.622 2.005 1.559 0.4647

0.903225806451613 3.081 2.962 2.496 1.954 1.526 0.4598

0.935483870967742 2.658 2.527 2.16 1.513 1.177 0.4464

0.967741935483871 2.639 2.514 2.06 1.383 1.069 0.4084

0.1 29.349 27.907 22.951 15.359 11.887 3.2941

Average of yearly averages: 1.37622

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: frflpdwa

Metfile: w12844.dvf

PRZM scenario: FLpeppersSTD.txt

EXAMS environment file: ir298.exv

Chemical Name: Fomesafen

Description Variable Name Value Units Comments

Molecular weight mwt 420 g/mol

Henry's Law Const. henry 7.5e-13 atm-m^3/mol

Vapor Pressure vapr 7.5e-7 torr

Solubility sol 1200 mg/L

Kd Kd 0.68 mg/L

Koc Koc mg/L

Photolysis half-life kdp 289 days Half-life

Aerobic Aquatic Metabolism kbacw 115.71 days Halfife

Anaerobic Aquatic Metabolism kbacs 5.08 days Halfife

Aerobic Soil Metabolism asm 428.8 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 1 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate: TAPP 0.42 kg/ha

Application Efficiency: APPEFF 0.95 fraction

Spray Drift DRFT 0.16 fraction of application rate applied to pond

Application Date Date 20-08 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND 1

UPTKF

Record 18: PLVKRT

PLDKRT
9

FEXTRC 0.5

Flag for Index Res. Run IR Reservoir

Flag for runoff calc. RUNOFF total none, monthly or 

total(average of entire run)

stored as frflpdwg.out

Chemical: Fomesafen

PRZM environment: FLpeppersSTD.txt modified Thuday, 24 May 2007 at 

09:44:22

EXAMS environment: ir298.exv modified Tueday, 26 August 2008 at 

05:14:08

Metfile: w12844.dvf modified Tueday, 26 August 2008 at 05:14:22

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 5.206 4.95 4.048 2.757 2.141 0.5767

1962 4.01 3.813 3.113 2.123 1.671 0.4831

1963 8.759 8.326 7.062 4.806 3.72 1.026

1964 29.87 28.4 23.27 15.56 12.02 3.29

1965 1.465 1.402 1.173 0.812 0.6343 0.3092

1966 14.19 13.5 11.74 8.052 6.237 1.685

1967 1.214 1.155 1.024 0.7555 0.5924 0.2473

1968 7.049 6.786 5.623 4.139 3.262 0.8949

1969 5.61 5.339 4.549 3.19 2.483 0.7249

1970 12.71 12.09 9.86 6.592 5.083 1.404

1971 6.009 5.858 4.961 3.376 2.631 0.781

1972 4.199 4.048 3.374 2.261 1.744 0.5008

1973 2.09 1.994 1.74 1.275 0.9979 0.2902

1974 4.538 4.326 3.609 2.454 1.913 0.5295

1975 2.716 2.584 2.352 1.648 1.28 0.3702

1976 2.507 2.388 2.034 1.59 1.279 0.3665

1977 6.35 6.06 5.5 3.761 2.924 0.8097

1978 2.764 2.631 2.196 1.516 1.235 0.3806

1979 5.959 5.67 4.735 3.182 2.46 0.7012

1980 39.87 37.92 31.56 21.21 16.37 4.415

1981 23.7 22.54 19.36 13.14 10.15 2.967

1982 2.659 2.529 2.093 1.425 1.105 0.4327

1983 3.214 3.054 2.577 1.755 1.375 0.3859

1984 17.92 17.19 14.94 10.21 7.902 2.135

1985 6.149 5.91 4.933 3.315 2.562 0.7998

1986 4.371 4.156 3.593 2.644 2.061 0.5915

1987 2.196 2.122 1.808 1.359 1.104 0.3299

1988 83.04 78.96 64.32 42.54 32.71 8.738

1989 7.699 7.318 6.283 4.349 3.373 1.297

1990 1.906 1.812 1.543 1.227 0.969 0.3057

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.032258064516129 83.04 78.96 64.32 42.54 32.71 8.738

0.0645161290322581 39.87 37.92 31.56 21.21 16.37 4.415

0.0967741935483871 29.87 28.4 23.27 15.56 12.02 3.29

0.129032258064516 23.7 22.54 19.36 13.14 10.15 2.967

0.161290322580645 17.92 17.19 14.94 10.21 7.902 2.135

0.193548387096774 14.19 13.5 11.74 8.052 6.237 1.685
10

0.225806451612903 12.71 12.09 9.86 6.592 5.083 1.404

0.258064516129032 8.759 8.326 7.062 4.806 3.72 1.297

0.290322580645161 7.699 7.318 6.283 4.349 3.373 1.026

0.32258064516129 7.049 6.786 5.623 4.139 3.262 0.8949

0.354838709677419 6.35 6.06 5.5 3.761 2.924 0.8097

0.387096774193548 6.149 5.91 4.961 3.376 2.631 0.7998

0.419354838709677 6.009 5.858 4.933 3.315 2.562 0.781

0.451612903225806 5.959 5.67 4.735 3.19 2.483 0.7249

0.483870967741936 5.61 5.339 4.549 3.182 2.46 0.7012

0.516129032258065 5.206 4.95 4.048 2.757 2.141 0.5915

0.548387096774194 4.538 4.326 3.609 2.644 2.061 0.5767

0.580645161290323 4.371 4.156 3.593 2.454 1.913 0.5295

0.612903225806452 4.199 4.048 3.374 2.261 1.744 0.5008

0.645161290322581 4.01 3.813 3.113 2.123 1.671 0.4831

0.67741935483871 3.214 3.054 2.577 1.755 1.375 0.4327

0.709677419354839 2.764 2.631 2.352 1.648 1.28 0.3859

0.741935483870968 2.716 2.584 2.196 1.59 1.279 0.3806

0.774193548387097 2.659 2.529 2.093 1.516 1.235 0.3702

0.806451612903226 2.507 2.388 2.034 1.425 1.105 0.3665

0.838709677419355 2.196 2.122 1.808 1.359 1.104 0.3299

0.870967741935484 2.09 1.994 1.74 1.275 0.9979 0.3092

0.903225806451613 1.906 1.812 1.543 1.227 0.969 0.3057

0.935483870967742 1.465 1.402 1.173 0.812 0.6343 0.2902

0.967741935483871 1.214 1.155 1.024 0.7555 0.5924 0.2473

0.1 29.253 27.814 22.879 15.318 11.833 3.2577

Average of yearly averages:

1.25894333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: frflpdwg

Metfile: w12844.dvf

PRZM scenario: FLpeppersSTD.txt

EXAMS environment file: ir298.exv

Chemical Name: Fomesafen

Description Variable Name Value Units Comments

Molecular weight mwt 420 g/mol

Henry's Law Const. henry 7.5e-13 atm-m^3/mol

Vapor Pressure vapr 7.5e-7 torr

Solubility sol 1200 mg/L

Kd Kd 0.68 mg/L

Koc Koc mg/L

Photolysis half-life kdp 289 days Half-life

Aerobic Aquatic Metabolism kbacw 115.71 days Halfife

Anaerobic Aquatic Metabolism kbacs 5.08 days Halfife

Aerobic Soil Metabolism asm 428.8 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 1 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate: TAPP 0.42 kg/ha

Application Efficiency: APPEFF 0.99 fraction

Spray Drift DRFT 0.064 fraction of application rate applied to pond

Application Date Date 20-08 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA
11

IPSCND 1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR Reservoir

Flag for runoff calc. RUNOFF total none, monthly or 

total(average of entire run)