Page 1 of 8

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

PC Code: 270000 

DP Barcode: 422934 

MEMORANDUM September 22, 2014 

SUBJECT: Isofetamid: ADDENDUM to Drinking Water Exposure Assessment for 

the Section 3 Registration of the New Chemical Isofetamid, in Support of 

Proposed Almond, Lettuce, Grapes (Subgroup 13-07F), Low Growing 

Berries (Subgroup 13-07G), Rapeseed (Subgroup 20A), and Turf Uses. 

TO: Christine Olinger, Branch Chief 

 Risk Assessment Branch 3 

 Health Effects Division (7509P) 

Cynthia Giles-Parker, Branch Chief 

Fungicide Branch 

 Registration Division (7505P) 

 

THROUGH: Dana Spatz, Branch Chief 

Environmental Risk Branch 3 

Environmental Fate and Effects Division (7507P) 

FROM: Melanie Biscoe, Physical Scientist 

 Environmental Risk Branch 3 

Environmental Fate and Effects Division (7507P) 

PEER REVIEW: James Hetrick, Ph.D., Senior Science Advisor 

 Environmental Risk Branch 3 

 Environmental Fate and Effects Division (7507P) 

Executive Summary

The Environmental Fate and Effects Division (EFED) has completed a Drinking Water 

Assessment (DWA) addendum for the Section 3 registration decision on the new broadspectrum, systemic fungicide isofetamid (IKF-5411) (PC Code 270000). The previous DWA 

(DP 410179, June 11, 2014) considered the following proposed uses: almond, lettuce, grapes 
Page 2 of 8

(Subgroup 13-07F), low growing berries (Subgroup 13-07G), rapeseed (Subgroup 20A), and turf 

uses; however, potential surface-water-sourced drinking water exposure from isofetamid use on 

cranberry was not assessed. This DWA addendum fully considers the proposed cranberry use 

that is included in the proposed low-growing berries Subgroup 13-07G, which results in the 

highest estimated potential concentrations in drinking water when considering both surface water 

and groundwater sources.

The maximum EDWCs calculated in this addendum are shown in Table 1. In surface water, the 

highest estimated 1-in-10 year peak (acute) concentration of isofetamid is 136 μg/L, and the 

highest estimated 1-in-10 year annual average concentration is 110 μg/L. EFED recommends 

using the 1-in-10 year peak surface water EDWC value (136 μg/L) for assessing human 

health dietary risk from acute exposures and the maximum 1-in-10 year annual average 

surface water EDWC value (110 μg/L) for assessing human health dietary risk from 

chronic and life-time/cancer exposures. Note that in the previous DWA, the maximum EDWC 

for acute exposures was 96 μg/L (surface water using Surface Water Concentration Calculator 

version 1.101, low-growing berry use) and the maximum EDWC for chronic exposures was 43 

μg/L (groundwater using Pesticide Root Zone Model-GroundWater version 1.07, turf use). 

Table 1. Maximum estimated drinking water concentrations (EDWCs) in parts per billion 

(μg/L) resulting from applications of Isofetamid on Cranberry. 

Drinking 

Water Source 

(model) 

Application Information 

Acute Chronic 

μg/L 

Pesticide 

Flooded 

Applications 

Model 

(PFAM) 

5 applications of 0.442 lb 

a.i./acre with a 7 day retreatment interval and a 30-

day resistance management 

interval 

Peak 

1-in-10 Year 

Chronic 

1-in-10 Year 

136 110 

Use Assessed

Isofetamid use on cranberry is assessed in this DWA addendum. Use information from the 

proposed isofetamid labels are in Table 2. 

Table 2. Cranberry Application Information from the Proposed Isofetamid Labels1,2. 

Maximum 

Individual 

Application 

Rate 

lbs a.i./A 

Number of 

Applications/ year

Minimum 

Application 

Interval 

(days) 

Max Annual 

Application Rate 

in lbs a.i./A/year 

Application 

Method Comments 

0.442 53 7 2.28 

Ground 

Aerial 

Chemigation4

Do not make more 

than two sequential 

applications of 

isofetamid. 
Page 3 of 8

1 There is 3.33 lb a.i. (isofetamid) in one gallon of the isofetamid products. 2

 This proposed use is part of the low growing berries crop subgroup 13-07G, which includes bearberry, bilberry, 

blueberry (low bush), cloudberry, cranberry, lingonberry, muntries, partrisgeberry, strawberry, and cultivars, 

varieties, and/or hybrids of these. 

3 This is not specified on the label; it is assumed by dividing the maximum application rate allowed/year by the 

maximum single application rate. 

4 Only center pivot, motorized lateral move, traveling gun, solid set or portable (wheel move, side roll, end tow, or 

hand move) irrigation systems. 

Drinking Water Modeling 

The Pesticide Flooded Application Model (PFAM version 1.0) model was used to generate 

Estimated Drinking Water Concentrations (EDWCs). Detailed descriptions, documentation, and 

links for running the PFAM model may found at 

http://www.epa.gov/oppefed1/models/water/index.htm. 

The PFAM generates daily, 1-in-10-year, and 30-year average EDWCs of isofetamid that may 

occur in and downstream of flooded fields through dry-field runoff, overflows, and manual 

releases of water. PFAM simulates pesticide application, movement and transformation in a 

watershed and the resultant pesticide loadings to a receiving water body via runoff, erosion, and 

spray drift, and then simulates the fate of the pesticide and resulting concentrations in the water 

body. The standard watershed geometry used for drinking water assessments assumes 

application to a 427-acre watershed that drains into an adjacent 13-acre reservoir that is an 

average of 2.7 meters deep (4,665,600 m3

 volume). A Percent Cropped Area (PCA) adjustment 

factor is not available for cranberries, and a surrogate PCA was not selected in this screening 

assessment for the cranberry use. 

In this DWA addendum, weather data files for LaCrosse, Wisconsin; Atlantic City, NJ; and 

Boston, MA were used to simulate conditions in areas where cranberry farming is prevalent. 

Likely application dates were selected based on guidance and references from the Biological and 

Economic Analysis Division (BEAD) (McManus and Colquhoun 2014; Oudemans et al. 2013; 

Sandler and DeMoranville 2008). Because the proposed label language prohibits more than two 

sequential isofetamid applications, surface water modeling conducted in this DWA addendum 

assumes that a pair of isofetamid applications with a 7-day retreatment interval are subsequently 

separated from the next pair of applications by 30-day interval. Input parameters used in the 

PFAM are found in Table 3. 

Table 3. Isofetamid Cranberry Application Input Parameters Used in the PFAM. 

Input Parameter Value Comments Source

Water column half-life 

(d) at 

20 °C 

240.52 

Represents the 90th percentile 

confidence bound on the mean of 

two test system half-lives. 

MRID 49011986 

Benthic Compartment 

half-life at 20 °C (d) 100,000 (default) 1 Represents no biodegradation under 

anaerobic conditions. MRID 49011985 

Unflooded half-life at 20 

°C (d) 60.92 

Represents the 90th percentile 

confidence bound on the mean of 

four soil half-lives. 

MRIDs 49011981 

and 49011982 
Page 4 of 8

Input Parameter Value Comments Source

Aqueous photolysis 

half-life at 

40° Latitude (d) 

1.8 The longer half-life of the two halflives calculated in the study. MRID 49011977 

Hydrolysis half-life (d) 100,000 (default) Represents no hydrolysis. MRID 49011976 

Organic Carbon 

Partition Coefficient 

(KOC) (L/kgOC) 

491 The mean of isofetamid KFoc's 

calculated for five soils. MRID 49011979 

Molecular weight 

(g/mol) 359.48 Product chemistry data (Calculated) 

Vapor pressure at 20 °C 

(torr) 4.4 x 10-11 Product chemistry data MRID 49011905 

Water solubility at 20 °C 

(mg/L) 5.33 Product chemistry data MRID 49011905 

Heat of Henry at 25 °C 

(J/mol) 54872.4 

Equals 8.314 × enthalpy of salvation 

(6,600 K) estimated by HenryWin 

v3.20. 

(Calculated) 

Application Date & Rate 

(kg a.i./ha) 

5/17: 0.495 

5/24: 0.495 

6/23: 0.495 

6/30: 0.495 

7/30: 0.495 

Maximum proposed single 

application rate and maximum 

number of applications. Minimum 

re-application intervals (7 days) 

applied, in addition to (assumed) 30 

day intervals for mandatory 

resistance management measures. 

Proposed label and 

likely application 

timeframes for 

Wisconsin, New 

Jersey, and 

Massachusetts 

(BEAD) 

Slow Release (1/day) 0 for each application Estimated (Estimated) 

Meteorology data 

location (metfile code) 

La Crosse, WI (w14920) 

Atlantic City, NJ (w14734) 

Boston, MA (w14739) 

Meteorological file for a location 

near cranberry agriculture. CEAM, 2011 

Flood Events Starting on 10/1, 2 events 3 

days apart Estimated (Estimated) 

Fill level (m) 10/1: 0.305 

10/4: 0 

Minimum flood depth and release 

depth. (Estimated) 

Wier level (m) 10/1: 0.458 

10/4: 0 Estimated wier heights. (Estimated) 

Min. Level (m) 0 for each event Estimated minimum water level (Estimated) 

Turn Over (1/day) 0 for each event Estimated turn over (Estimated) 

Crop zero height 

reference May 1 Estimated value (Estimated) 

Days from zero to full 

height 120 Estimated value (Estimated) 

Days from zero height to 

removal 153 Estimated value (Estimated) 

Max. aerial coverage 0.2 Value from OR berries PE scenario (Estimated) 

Area of application (m2) 526,090 Represents 10x the area of the Index 

Reservoir (Calculated) 

Area of watershed (m2) 1,728,000 Area of the Index Reservoir 

watershed USEPA, 2010 
Page 5 of 8

Input Parameter Value Comments Source

Watershed curve 

number 84 Value for fallow conditions in OR 

berries and other PE scenarios (Estimated) 

Base flow (m3/sec) 0 Value based on conceptual models 

for Index Reservoir and Farm Pond (Estimated) 

Modeling Results

Table 4 reports the EDWCs calculated for each location representing cranberry use areas. The 

maximum 1-in-10 year peak EDWCs in surface water range from 91 to 136 μg/L, the 1-in-10 

year annual average EDWCs in surface water range from 62 to 110 μg/L. The LaCrosse, 

Wisconsin location results in the maximum EDWCs. The PFAM output for the surface water 

EDWCs for the LaCrosse, Wisconsin location is attached in Appendix A. 

Table 4. Isofetamid Surface Water EDWCs for the Cranberry Use. 

Weather File 

Location

1-in-10 Year Peak 

Concentration 

(μg/L)

1-in-10 Year 

Chronic 

Concentration 

(μg/L) 

La Crosse, WI 

(w14920) 136 110 

Atlantic City, NJ 

(w14734) 91 62 

Boston, MA 

(w14739) 103 72 

Bibliography 

McManus, Patricia; Colquhoun, Jed; Nice, Glenn; and Guedot, Christelle. 2014. “Cranberry 

Pest Management in Wisconsin.” UW Extension. A3276. 

Oudemans, Peter; Majek, Bradley; and Rodriguez-Saona, Caesar. 2013. 2013 Commercial 

Cranberry Pest Control Recommendations for New Jersey.” Rutgers New Jersey Agricultural 

Experiment Station: Cooperative Extension Bulletin E308. 

Sandler, Hilary and DeMoranville, Carolyn. 2008. "Cranberry Production: A Guide for 

Massachusetts - Summary Edition." Cranberry Production Guide. Paper 1. 

http://scholarworks.umass.edu/cranberry_prod_guide/1

USEPA 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides. Version 2.1 October 22, 2009. U.S. Environmental Protection Agency, 

Office of Pesticide Programs, Environmental Fate and Effects Division. Arlington, VA. 

http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm 
Page 6 of 8

USEPA. 2010. R. Jones, K. Costello, J. Hetrick, J. Lin, R. Parker, N. Thurman, and C. Peck. 

Development and Use of the Index Reservoir in Drinking Water Exposure Assessments. U.S. 

Environmental Protection Agency, Office of Pesticide Programs. Apr. 15, 2010. Online at: 

http://www.epa.gov/oppefed1/models/water/index_reservoir_dwa.html

USEPA 2012. Development and Use of Percent Cropped Area and Percent Turf Area 

Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update. March 16, 2012. 

U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. Arlington, VA. 

http://www.epa.gov/oppefed1/models/water/pca_adjustment_dwa.html

USEPA 2014. D411110. Isofetamid: Report of the Residues of Concern Knowledgebase 

Subcommittee (draft). U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Health Effects Division. Arlington, VA. 

 
Page 7 of 8

Appendix A. Isofetamid Cranberry Use PFAM Output for LaCrosse, Wisconsin Weather 

File Location 

 Variable Volume Water Model, Version 0.0 

 

 ******************************************* 

Performed on: 9/ 3/2014 at 15:20 

 Standard Reservoir, Area = 52555 m2, Depth = 2.73 m 

 Chemical # 1 

 

Peak 1-in-10 = 1.36E+02 ppb 

Chronic 1-in-10 = 1.10E+02 ppb 

 

4-day avg 1-in-10 = 1.34E+02 ppb 

21-day avg 1-in-10 = 1.30E+02 ppb 

60-day avg 1-in-10 = 1.24E+02 ppb 

90-day avg 1-in-10 = 1.24E+02 ppb 

 

 YEAR Peak 4-day 21-day 60-day 90-day Yearly Avg 

 1 7.72E+01 7.67E+01 7.55E+01 7.43E+01 7.28E+01 5.63E+01 

 2 1.20E+02 1.15E+02 1.07E+02 1.04E+02 9.75E+01 8.62E+01 

 3 1.08E+02 1.06E+02 1.00E+02 9.62E+01 9.45E+01 8.54E+01 

 4 9.53E+01 9.46E+01 9.33E+01 9.15E+01 8.96E+01 7.90E+01 

 5 1.39E+02 1.36E+02 1.31E+02 1.21E+02 1.13E+02 9.43E+01 

 6 1.04E+02 1.01E+02 9.72E+01 9.26E+01 9.11E+01 8.57E+01 

 7 9.35E+01 9.06E+01 8.15E+01 8.70E+01 8.82E+01 6.70E+01 

 8 1.13E+02 1.09E+02 1.04E+02 1.02E+02 1.02E+02 9.11E+01 

 9 1.16E+02 1.12E+02 1.09E+02 1.09E+02 1.07E+02 9.88E+01 

 10 1.26E+02 1.26E+02 1.25E+02 1.23E+02 1.21E+02 1.09E+02 

 11 1.36E+02 1.34E+02 1.34E+02 1.32E+02 1.31E+02 1.23E+02 

 12 1.69E+02 1.64E+02 1.62E+02 1.52E+02 1.43E+02 1.11E+02 

 13 1.02E+02 9.78E+01 9.58E+01 9.38E+01 9.65E+01 8.35E+01 

 14 1.25E+02 1.25E+02 1.24E+02 1.24E+02 1.23E+02 1.04E+02 

 15 1.11E+02 1.09E+02 1.05E+02 1.14E+02 1.17E+02 9.46E+01 

 16 1.08E+02 1.07E+02 1.06E+02 1.03E+02 1.00E+02 8.69E+01 

 17 1.27E+02 1.26E+02 1.25E+02 1.24E+02 1.24E+02 1.10E+02 

 18 1.33E+02 1.26E+02 1.22E+02 1.20E+02 1.21E+02 8.24E+01 

 19 1.18E+02 1.14E+02 1.08E+02 1.01E+02 9.85E+01 9.00E+01 

 20 1.13E+02 1.10E+02 1.06E+02 9.50E+01 9.37E+01 7.34E+01 

 21 8.87E+01 8.50E+01 8.45E+01 8.37E+01 8.36E+01 7.14E+01 

 22 1.16E+02 1.15E+02 1.12E+02 1.09E+02 1.07E+02 9.97E+01 

 23 1.30E+02 1.28E+02 1.25E+02 1.21E+02 1.19E+02 9.51E+01 

 24 9.47E+01 9.43E+01 9.35E+01 9.17E+01 9.00E+01 7.68E+01 

 25 1.11E+02 1.09E+02 1.05E+02 9.95E+01 9.55E+01 8.34E+01 

 26 1.21E+02 1.18E+02 1.14E+02 1.12E+02 1.09E+02 8.74E+01 

 27 9.86E+01 9.64E+01 9.29E+01 8.55E+01 8.33E+01 7.43E+01 
Page 8 of 8

 28 8.15E+01 7.91E+01 7.57E+01 7.29E+01 7.53E+01 6.43E+01 

 29 9.46E+01 9.37E+01 9.14E+01 8.97E+01 8.81E+01 8.00E+01 

 30 9.76E+01 9.35E+01 8.54E+01 8.17E+01 8.48E+01 7.49E+01 

 

 

 *********************************************************************** 

 Effective compartment halflives averaged over simulation duration: 

 

 washout halflife (days) = 228.8117 

 water col metab halflife (days) = 421.2925 

 hydrolysis halflife (days) = 100109.8 

 photolysis halflife (days) = 353.5643 

 volatile halflife (days) = 1.2372009E+08 

 total water col halflife (days) = 104.3581 

 

 zero burial 

 benthic metab halflife (days) = 175159.0 

 benthic hydrolysis halflife (days) = 5402744. 

 total benthic halflife (days) = 169658.6 

 *********************************************************************** 

 

 **************** Inputs ******************* 

 Chemical # 1 

 240.520000000000 

 Water Column System Halflife(except photo & hydrolysis = 

 100000.000000000 Benthic Compartment Halflife (except hydrolysis) = 

 1.80000000000000 Photolysis Halflife = 

 100000.000000000 Hydrolysis Halflife = 

 359.480000000000 Molecular Wieght = 

 4.400000000000000E-011 Vapor Pressure = 

 5.33000000000000 Solubility = 

 491.000000000000 Koc = 

 20.0000000000000 Aerobic Reference Temper = 

 20.0000000000000 Anaerobic Reference Temper = 

 40.0000000000000 Reference Latitude = 

 54872.4000000000 Enthalpy of Henry = 

 25.0000000000000 Henry Reference Temperature 

 ****************** End of Run ************************ 

 ******************************************************