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OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

October 20, 2015

PC Code: 050410

MEMORANDUM DP Barcode: 428910

SUBJECT: Fluensulfone: Drinking Water Exposure Assessment for Proposed New Uses on 

Tuberous and Corm Subgroup 1C, Brassica (Crop Group 5A and 5B), Leafy 

Vegetables (Crop Group 4), Root Vegetables (Crop Group 1B), Strawberry 

including low growing berry subgroup (Crop Group 13-07G), and Tobacco 

FROM: James Lin, Environmental Engineer

Environmental Risk Branch II

Ecological Fate and Effects Division (7507P)

THROUGH: Ronald Parker, Senior Environmental Engineer

Brian Anderson, Branch Chief 

Environmental Risk Branch II

Ecological Fate and Effects Division (7507P)

TO: Michael Doherty, Risk Assessor

Christina Swartz, Branch Chief

Risk Assessment Branch II

Health Effects Division (7509P)

AWillis Ertman, Risk Manager Reviewer

Barbara Madden, Risk Manager

Insecticide-Rodenticide Branch

Registration Division (7505P)

1. EXECUTIVE SUMMARY

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

above subject crop group uses in support of the Health Effects Division’s (HED) human health 

risk assessment. As depicted below in Table 1, the surface water sources for cranberry uses 

provide the higher values than the groundwater sources. Therefore, the EDWCs of 187.84 μg/L, 

and 64.99 μg/L should be used for acute and chronic drinking water exposure, respectively.
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Table 1.1. Maximum Screening Drinking Water Exposure Estimates for Proposed 

Fluensulfone Uses. A

Source (Tier: Model) Use (Maximum Rate) Peak Exposure 

(μg/L)

Annual Mean 

Exposure 

(μg/L)

Surface water (Tier I: Cranberry model) Cranberries (3.5 lb a.i./A) 187.84 64.99

Groundwater (Tier I: PRZM-GW)

Cucurbits and Fruiting 

Vegetables. (3.57 lb 

a.i./A) 

77.5 52.5

A Maximum values in bold.

2. USE CHARACTERIZATION

Two labels are proposed for the new uses and they are summarized below:

MCW-2 15G (alternate band name Nimitz® 1.5G Nematicides) is a granule formulation 

containing 15% of fluensulfone active ingredient by weight. The label use is for nematode 

control in root crop potato (vegetable, tuberous and corm subgroup 1C). Specifically the use 

restrictions including:

 Do not apply more than one application per crop. Do not exceed 24 pounds of product

per acre (3.6 lb ai/ac) per year (365 days).

 Do not allow livestock animals (cattle, sheep or horses etc.) to forage or graze on

treated areas within 6 months following application.

Fluensulfone 480EC (alternate brand name: NIMITZTM) is an emulsifiable concentrate 

formulation containing 4 pounds active ingredient (ai) per gallon. The proposed new label uses 

including:

(1) Brassica (cole) leafy vegetables – broccoli, cabbage, cauliflower and other brassicas 

including: broccoli, Chinese (gai lon); broccoli raab (rapini); brussels sprouts; cabbage, 

Chinese (bok choy); cabbage, Chinese (napa); cabbage, Chinese mustard(gai choy); 

cavalo broccolo; collards; kale; kohlrabi; mizuna; mustard greens; mustard spinach; rape 

greens; 

(2) Leafy vegetables – celery, lettuce (head and leaf) spinach and other leafy vegetables 

including: amaranth (Chinese spinach); arugula (roquette); cardoon; celery, Chinese; 

celtuce; chervil; chrysanthemum, edible-leaved; chrysanthemum, garland; corn salad; 

cress, garden; cress, upland; dandelion; dock (sorrel); endive (escarole); fennel, Florence; 

orach; parsley; purslane, garden; purslane, winter; radicchio (red chicory); rhubarb; 

spinach, New Zealand; spinach, vine; Swiss chard; 

(3) Strawberry and low growing berry - including: bearberry; bilberry; blueberry, lowbush; 

cloudberry; cranberry; lingonberry; muntries; partridgeberry; strawberry; cultivar, 

varieties, and/or hybrids of these; and 

(4) Tobacco. 

Specifically the use restrictions include:
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 Do not make applications when soil temperature is below 55oF. Root knot nematodes 

are not active below 55oF and will not absorb Fluensulfone 480 EC.

 Do not apply more than one application per crop and no more than 112 fl. oz. of product 

per acre (3.5 lb ai/ac) per year (365 days).

3. PREVIOUS DRINKING WATER ASSESSMENTS

The most recent drinking water assessment for turf uses (DP 424167) has indicated that the 

drinking water assessment should be based on the uses for cucurbits and fruiting vegetables uses 

from groundwater sources (DP 411774 and DP 417634). The assessments present maximum 

EDWCs from ground water sources (based on PRZM-GW) of 77.7 μg/L, and 52.5 μg/L, for 

acute and chronic exposure, respectively. The residues of concern for groundwater include 

parent fluensulfone and the degradate methyl sulfone.

4. DRINKING WATER ASSESSMENT 

4.1 From Groundwater Sources Based on MCW-2 15G Label

According to the label, the maximum application rate is 3.6 lb ai/ac and only allowed for one 

application per year. The detailed fate characterizations including product chemistry, transport, 

mobility, degradation, field studies, environmental degradates, and selections of residues of 

concern have been presented in the previous drinking water assessments. Only modeling input 

information and output results are presented in this assessment.

PRZM-GW modeling of Parent Fluensulfone Alone

PRZM-GW (version 1.07) model inputs for fluensulfone alone are listed in Table 2. The outputs 

are presented in Table 3. Three use pattern schemes are represented.

Table 2. PRZM-GW Input Parameters for Fluensulfone Alone. 

Input Parameter Value Justification Source

One application per 

year @ maximum 

application rate

4.032 kg ai/ha

(3.6 lb ai/ac) Values follow label directions Proposed Label

Application Date

Application can be 

made at planting or 

pre-planting

two weeks before emergence 

date: 03/27 (DMV); 12/18 

(FLC); 02/01 (FLP0; 04/17 

(GAP); 05/01 (NCC); 04/17 

(WIC)

Proposed Label

Hydrolysis Half-life 0 Stable at pH 4, 7 and 9 MRID 48574718

Aerobic Soil 

Metabolism

Half-life

17.08 days

90th percentile confidence bound 

on the mean of six half-lives: 

8.05, 9.12, 9.53, 11.9, 15.0, and 

25.4 

MRID 48574823 
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Input Parameter Value Justification Source

Organic Carbon 

Partition Coefficient 

(KOC)

192 L/kgOC

Mean value of 154, 157, 172, 203, 

and 275 MRID 48574833

Table 3. PRZM-GW Output for Fluensulfone Alone

Modeled 

Scenario Max. Daily Conc. (μg/L)

Mean 

Breakthrough 

Time (yrs)

Post-breakthrough Mean 

(μg/L)

DMV corn 3.97 9.14 3.19

FL citrus 13.4 7.25 10.3

FL potato 0.0162 13.03 0.0063

GA peanut 0.578 12.04 0.45

NC cotton 0.536 10.22 0.302

WI corn 18.2 13.54 15.4

A Maximum values are in bold.

PRZM-GW modeling of Degradate Methyl Sulfone Alone

PRZM-GW model inputs for methyl sulfone alone are listed in Table 4. The outputs are 

presented in Table 5.

Table 4. PRZM-GW Input Parameters for Methyl Sulfone Alone. 

Input Parameter Value Justification Source

One application per 

year @ maximum 

application rate

0.3004 kg ai/ha

(0.2682 lb ai/ac) Values follow label directions Proposed Label

Application Date

Application can be 

made at planting or 

pre-planting

Assuming the application dates as 

the modeling for the parent Proposed Label

Hydrolysis Half-life 0 Assumed stable Absence of data

Aerobic Soil 

Metabolism

Half-life

45.3 days

90th percentile confidence bound 

on the mean of three half-lives: 

34.2, 41.3, and 44 days

MRID 48574829 

Organic Carbon 

Partition Coefficient 

(KOC)

27.2 L/kgOC

Mean value of 14.3, 17.5, 26.3, 

27.5, and 50.5 MRID 48574834

Corrected for maximum detection value (7.45%) of methyl sulfone in the aerobic soil metabolism study, as 

fluensulfone equivalent.
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Table 5. PRZM-GW Output for Methyl Sulfone Alone

Modeled 

Scenario Max. Daily Conc. (μg/L)

Mean 

Breakthrough 

Time (yrs)

Post-breakthrough Mean 

(μg/L)

DMV corn 27.2 3.82 22.7

FL citrus 32.4 2.71 24.1

FL potato 9.9 3.11 5.46

GA peanut 8.43 4.56 6.8

NC cotton 12.9 6.04 9.5

WI corn 40.5 7.49 33.9

A Maximum values are in bold.

Combining Results of Parent Fluensulfone and Degradate Methyl Sulfone

The resulting EDWCs of fluensulfone and methyl sulfone combined are derived by adding the 

contents of Table 3 and Table 5. Table 6 shows the final water values based on ground water 

sources.

Table 6. Final Results of EDWC 

Modeled 

Scenario

Max. Daily Conc. 

(μg/L)

Post-breakthrough 

Mean (μg/L)

DMV corn 31.17 25.89

FL citrus 45.80 34.40

FL potato 9.92 5.47

GA peanut 9.01 7.25

NC cotton 13.44 9.80

WI corn 58.70 49.30

A Maximum values are in bold.

The combined EDWCs of 58.7 μg/L and 49.3 μg/L, respectively for acute and chronic concerns 

are less than the values provided by the previous drinking water assessment for cucurbits and 

fruiting vegetables. Therefore, for groundwater sources, the EDWCs of 77.7 μg/L, and 52.5

μg/L should be used for acute and chronic drinking water exposure, respectively. 

4.2 From Surface Water Sources Based on Fluensulfone 480EC Label

Among the proposed new uses including: brassica (Crop Group 5A and 5B), leafy vegetables 

(Crop Group 4), root vegetables (Crop Group 1B), strawberry including low growing berry 

subgroup (Crop Group 13-07G), and tobacco. The maximum application rate is 3.5 lb ai/ac and 

only allowed for one application per year. Based on the past experience, among all these 

proposed used, the cranberry use may have produce the highest EDWC, due to the typical 

flooding practice for harvest. To assess this use, the provisional cranberry model is used.
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Provisional Cranberry Model

The Provisional Cranberry Model is a provisional refinement to the Tier I Rice Model (v1.0, 

May 8, 2007). Refinements include the addition of simple degradation processes in dry and 

flooded conditions and a water depth of twelve inches, rather than the water depth of four inches 

used in the rice model. These modifications allow estimation of screening-level peak and annual 

mean EDWCs of fluensulfone residues of concern that may occur in untreated surface water used 

as drinking water following use on cranberries.

The Tier I Rice Model relies on an equilibrium partitioning concept to provide conservative 

estimates of EDWCs resulting from application of pesticides to rice paddies. When a pesticide is 

applied to a rice paddy, the model assumes that it will instantaneously partition between a water 

phase and a sediment phase. The model does not account for pesticide degradation, mass 

transfer between the aqueous phase and the sediment, volatilization, dilution, or other dissipation 

processes. The Tier I Rice Model was calibrated to generate estimates that are consistent with or 

conservative for dissolved concentrations measured within rice paddies and in discharged paddy 

water. The model was not evaluated or calibrated for concentrations measured in sediment and 

does not account for residues bound to suspended sediment. Guidance for using the Tier I Rice 

Model may be found on the U.S. Environmental Protection Agency (EPA) Water Models webpage (USEPA, 2011a). 

The Provisional Cranberry Model is based on the same assumptions as the Tier I Rice Model, 

with the addition of degradation processes in dry and flood conditions and a water depth of 

twelve inches in the flooded cranberry bog. Degradation of fluensulfone residues of concern is 

assumed to occur predominantly via aerobic microbial metabolism, whether on dry cranberry

bog soil or in bog flood water.

The cranberry bog water depth of twelve inches is a maximum depth recommended by the Cape 

Cod Cranberry Growers Association (2001). Previous assessments of mesotrione uses that 

employed the Provisional Cranberry Model assumed a water depth of eighteen inches (DP 

barcode 339984, USEPA, 2004; DP barcode 325840, USEPA, 2006a), which is within the range 

of water depths traditionally used. However, modern water conservation pressures are causing 

cranberry growers to reduce the flood depth to fewer inches above the vertical cranberry 

branches, which grow up to eight inches high (Cape Cod Cranberry Growers Association, 2001; 

The Cranberry Institute, 2008). Therefore, a twelve-inch deep flood is a reasonable refinement 

to model assumptions.

The proposed use of fluensulfone on cranberries at the maximum application rate of 3.5 lbs a.i./A 

and only one application allowed per year.

Cranberry bogs are not typically flooded until the night before harvesting. For application of 

fluensulfone, it is assumed the maximum application rate of 3.5 lb ai/ac was aged on dry soil 

with the Provisional Cranberry Model for 60 days. The resulting residues (in lbs a.i./A) were 

then input into the flooded component of the model to estimate exposure in bog tailwater 

following harvest. Peak and annual mean EDWCs were calculated twenty-one days after 

flooding to account for three weeks of holding period. 
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The residues of concern from the surface water sources include fluensulfone, methyl sulfone and 

deschloro-fluensulfone, the last one is only detected in the aquatic system, therefore is different 

from the groundwater sources. The modeling inputs are estimated using available chemical 

properties and environmental fate data. Table 7 lists the environmental fate parameters for the 

total residues of concern (TRC) of fluensulfone that are relevant for exposure modeling. These 

parameters reflect regression of the total residues at each interval of the biodegradation studies. 

For the soil metabolism studies (MRID 48574823, 48574824) the TRC biodegradation half-lives 

were based on the sum of parent fluensulfone and methyl sulfone; whereas for the aquatic 

metabolism studies (MRID 48574839, 48574840), the TRC biodegradation half-lives were based 

on the sum of parent fluensulfone, methyl sulfone and deschloro-fluensulfone. Because PCA 

(percent crop area factor) values were not available for non-agricultural uses, they were not used 

for exposure estimates in this assessment.

Table 7. Provisional Cranberry Model Input Parameters for Fluensulfone, DeschloroFluensulfone Plus Methyl Sulfone.

Input Parameter Value Comments Source

Application Rate

(lbs a.i./A) 3.5 Maximum proposed single application rate. Proposed label

Applications per Year 1

Maximum proposed number of 

applications per year at the maximum 

proposed single application rate.

Proposed label

Organic Carbon Partition 

Coefficient (KOC) (L/kgOC)

47.08 Represents the mean KOC of methyl 

sulfone based on five values (31.3, 37.4, 

52.2, 55.4, and 59.1)

MRID 48574833

Aerobic Soil Metabolism 

Half-life (days)

24.01 Represents the upper 90% confidence 

bound on the mean of five half-lives 

(6.73, 8.68, 12.8, 20.2, and 39 days) for 

fluensulfone + methyl sulfone

48574823

Aerobic aquatic metabolism

half-life (days)

93.45 Represents the upper 90% confidence 

bound on the mean of two half-lives (85.7 

and 89.5 )

48574839

The results of provisional cranberry model are presented in Figure 1. The peak EDWC is 

187.84 μg/L, and the annual mean EDWC is 64.99 μg/L.

Figure 1. EDWC for Cranberry Uses

0

100

200

0 100 200 300 400

Aqueous Concentration 

(μg/L)

Days After Application 

Cranberry Bog EDWCs vs 

Time, After a 21-d Holding 

Period
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4.3 Drinking Water Exposure Conclusions

The EDWCs from the surface water sources for cranberry uses are higher than that from the 

groundwater sources, therefore, the final EDWC should be used are 187.84 μg/L and 64.99 μg/L, 

respectively for the peak value and the annual mean value.