2

following the use scenario on loamy sand soil in NC eastern coastal p lain with two single
bensulide maximum granular application s at 1 6 lb ai per acre each a t 4

- month interval ( Table 1 )

.

Table 1. Recommended Surface water and G roundw ater EDWCs ( μg/L ) for
Bensulide Oxon

Surface Water Model: Tier II SWCC ( v 1.106)
1 in 10 yr
Peak 1 in 10 yr

Annual Average 30 y r Annual

A verage Ground Spray

- CA Lettuce scenario (W23273 .dvf) (6 lbs ai/acre for 3 applications (2/1, 6 /1 , 10/1 ) 979 494 305

Ground water Model: Tier 1 PRZM

- GW

Peak
Values Post Breakthrough

Average Breakthrough

Time (Days)

NC Eastern Coastal Plain

- (w13722Extended.dvf)

2.12 lb s ai/acre for 2 applications (3 /1 and 7/1 ) 1,250 1,200 7,1 0 6

The main uncertainties with the bensulide o xon exposure estimate are lack of aerobic soil metabolism and aerobic aquatic studies for bensulide and bensulide oxon. In addition,
bens ulide oxon hydrolysis study is not submitted

.

Previous Drinking Water Assessment

Two previous drinking water e xposure assessments were conducted for parent bensulide only ( USEPA 199 7

, and USEPA 200 0 ). The EDWCs from surface water source s were modeled using the Tier I model GENEEC , with two applications at 12.5 lb /A each and a 120

- day application interval

. The pre vious recommended EDWCs for bensulide from
surface water source s we re 979 μg/L for acute (peak) and 947 μg/L for chronic ( annual

mean ) (USEPA 1997)

. The E DWC from ground water source s w as not expected to exceed 1.0 μg/L based on the Tier I model SCI

- GROW (USEPA 2000)

.

Use and Usage

Bensulide is a pre

- emergen ce organophosphate herbicide currently registere d for use on a variety of agriculture field and vegetable crops, and non

- agricultural ornamental s , golf course turf, residential lawns and turf. According to an u pdated Screening Level Usage Analysis (SLUA) of national agricul tural pesticide usage data (2004

– 2013) by the Agency’s Biological and Economic Analysis Division (BEAD), an average of 587,000 lb
ai bensulide is applied in the U nited States and of this, about 51 % of the total usage was

on lettuce (300,000 lb ai), 14% w as on cantaloupes (80,000 lb ai), and 10% was on broccoli (60,000 lb ai ) ( USEPA 2015).

Bensulide may be applied up to three times per year and with a 120

- day minimum
retreatment interval b ased on a LUIS report by BEAD (USEPA, 2012 a ), and a recent
label su mmary provided by the registrant for the current federally registered agricultural
and non

- agricultural uses ( Table 2 ). No aerial application was specified in any of the
labels and therefore, the EDWCs were not modeled for aerial application

. There are so me3

missing use directions on the label s that are marked as “NA” or “NS” on the r egistrant’s

use s ummary table. These use directions should be clarified on the labels , especially the
maximum annual application rate s

. For this drinking water assessment, we have calculated the maximum annual application rate (ai) based on best available information
on labels for the application of the formulated products. In addition, we did not assess the label with the vague language, for example, the label (EPA10163

- 205) specified “ two or more applications per year may be necessary

... ” because of the uncertainty.

Table 2 . Maximum Labeled Application Rates for Bensulide

Use Ground

Application

Method 1 Maximum

Single Application

Rate (lb a.i./A) Maximum

Number of Applica tions per Year Maximum

Yearly Application

Rate (lb a.i./A) Application

Interval (days) and Date (M/D)

Golf course turf
EPA9198

- 176 Broadcast

– granular 16 2 32 120 (4/1, 8/1) Golf course turf, turf
Ornamental lawns

EPA10163

- 196

EPA10163

- 198

EPA10163

- 1 99
EPA10163

- 204

EPA2217

- 778
EPA9198

- 172

EPA 2217

- 696 Broadcast

– granular
Broadcast

spray

– Emulsifiable

Concentrate 12.5 2 25 120 (4/1, 8/1)

Ornamental lawns and turf
Residential lawns

EPA10163

- 205 Hand spray Disposable
container (16oz) 8.65 2 or more NS 2 120

Ornamental lawns and turf
Residential lawns

EPA 2217

- 838 Broadcast

- Granular 7.5

- 12.5 2 15

- 25 120 (4/1, 8/1)4 Use Ground

Application

Method 1 Maximum

Single Application

Rate (lb a.i./A) Maximum

Number of Applica tions per Year Maximum

Yearly Application

Rate (lb a.i./A) Application

Interval (days) and Date (M/D)

Artichokes, beans, beet, bell

pepper, Brassica (head and stem) vegetables, broccoli, broccoli raab, Brussels sprouts, cabbage, cardoon,

carrot, cauliflower, celery, celtuce, chervil, chicory/radicchio, chrysanthemum (garland), cole crops, collards, corn salad, cress (garden, upland), dandelion, dock (sorrel), eggplant, endive, fennel, garlic, greens, groundcherry (strawberry tomato/tomati llo), kale, kohlrabi, leafy vegetables, lettuce (head, leaf), mustard, mustard cabbage, okra, onion (dry bulb and green), orach (mountain spinach), parsley, peas, pepper, pepper (chili), pimento, radish, roquette (arugula), shallot, spinach,
Swiss chard

EP A10163

- 200 Broadcast

spray

– Emulsifiable
Concentrate 5 (carrot)

6 1, 2, or 3 6, 12, or 18 120 (2/1, 6 /1

, 10/1 )

Cantalo u pe, chayote, cucumber, cucurbit vegetables, cucuzzi, gherkin, gourds, gourd (wax), melons (bitter, honeydew, citron, mango, musk, w ater, winter melons), pepino, pumpkin, squash (butternut, summer, zucchini squash)
CA960003

NJ070001 Broadcast

spray

– Emulsifiable
Concentrate 8.94 1 or 2 9 or 18 120 (4/1, 8/1)

1 When there are several application methods (because of different types o f formulation), the chosen method would either result in the highest environmental exposure or was labeled for a higher maximum rate than other application methods.

2 NS

– not specified. Th is information should be clarified on the labels

. This spot treatme nt use pattern is considered to result in negligible exposure on the watershed

- scale basis of this assessment. Therefore, it was not evaluated with exposure models.

Physical , Chemical and Environmental Fate Properties

Information from acceptable and sup plemental laboratory studies indicates bensulide is persistent. Neither abiotic hydrolysis nor photolysis are major degradation processes in
water or on soil surfaces

. An aerobic aquatic metabolism study was not available for this5

assessment. The aerobic s oil metabolism study was classified as supplemental as only one soil type was used. The main route of dissipation of bensulide appears to be aerobic
soil metabolism. Under aerobic conditions

, bensulide oxon ( up to 13.8% of the applied ) and carbon dioxide ( up to 21% of the applied ) are the major degradates in the soil (MRID 40460301). Under anaerobic soil conditions in the laboratory, bensulide is considered stable (MRID 40460302). The physical, chemical, and environmental fate properties of
bensulide and be nsulide oxon are summarized in Table 3

.

Table 3

. Physical, Chemical and Environmental Fate Properties of Bensulide and Its Major Degradate Bensulide Oxon

Parameter Bensulide (Parent) Bensulide Oxon (Major Degradate)

Value Reference Value Reference

Ch emical Name O,O

- d iisopropyl

- S

- 2

-

phenylsulfonylaminoet hylphosphorodithioate MRID 45761801 O,O

- diisopropyl

- S

- 2

- phenylsul f

onylaminoethyl phosphorothioate MRID 45761801

CAS Number 741

- 58

- 2 MRID 45761801 20243

- 81

- 6 MRID 47660403 Empirical Formula C 14 H 24 NO 4 P S 3 MRID 45761801 C 14 H 24 NO 5 PS 2 EPI Suite (v 4.10) Molecular Weight (g/mole) 397.54 MRID 45761801 381.44 EPI Suite (v 4.10)

Chemical Structure EPI Suite (v 4.10) EPI Suite (v 4.10)

SMILES Code CC(C)OP(=S)(OC(C)C

)SCCNS(=O)(=O)c1cc

ccc1 EPI Suite v4.1 0 CC(C)OP(=O )(OC(C)C)S CCNS(=O)(=O)c1ccccc1 EPI Suite (v 4.10)

Melting Point (oC) 36 MRID 41532001 89.97 EPI Suite (v 4.10) Boiling Point (oC) 424.96 EPI Suite (v 4.10) 476.9 EPI Suite (v 4.10) Vapor pressure ( mm Hg @ 25 o C ) 8.2 x 10

- 7 MRID 41532001 2. 48 10

- 8 EPI Suite (v 4.10) Henry’s Constant ( atm m 3 mole

- 1 ) 7.7 x 10

- 8 MRID 41532001 7.10 x 10

- 12 EPI Suite (v 4.10) Solubility (mg/

/ L @
25 o C ) 5.6 MRID 41532001 461.24 EPI Suite (v 4.10)
K ow 4.20 EPI Suite (v 4.10) 2.35 EPI Suite (v 4.10)

K d (mL/g) 10.9 Sand

30.5 Sandy Loam Soil 34.0 Clay Loam Soil 1 96.8 Clay Loam Soil 2 MRID 4 2826701 1.96 Sand 4.23 Sandy Loam Soil 6.05 Clay Loam Soil 1 26.5 Clay Loam Soil 2 MRID 431807016 Parameter Bensulide (Parent) Bensulide Oxon (Major Degradate)

Value Reference Value Reference

K oc (mL/g) 34 80 Sand

1348 Sandy Loam Soil 4379 Clay Loam Soil 1

232 8 Clay Loam Soil 2 MRID 4 2826701 62 6 Sand

18 7 Sandy Loam Soil

77 9 Clay Loam Soil 1

63 7 Clay Loam Soil 2 MRID 431807 01

Hydrolysis t 1/2 (day)
@ 25 0 C 230 (pH 5)
220 (pH 7 & 9) MRID 00160074

- ( N ot A vailable) -

Aerobic soil met.

t 1/2 (day)

Bensulide Oxon
13 .8%@270 days
Benzenesulfonamide
<0.5%
Bond residues 18%@360 days
CO2 21%@360 days 363 MRID 40460301 749 (Bensulide + Oxon) MRID 40460301

Aquatic photolysis

t 1/2 (day)

Bensulide Oxon 4.8%@41 days 132 MRID 40513401

173 (Bensulide + Oxon) MRID 40513401

Anaerobic Soil met. Stable MRID 40460302

- - Field Dissipation,
California 15

– 34 days MRID 40534902
MRID 40534904
MRID 40534905 - -

Field Dissipation, Mississippi 30

- 210 days MRID 40534901
MRID 40534903
MRID 40534 906 - -

Bioconcentration factor (BCF) 550 MRID 41931001

- -

Environmental Transport , Field Dissipation and Bioconcentration

T he degradate bensulide oxon is more soluble in water (461 mg/L, EPISuite v. 4.10) than
bensulide ( 5.6 mg/L, MRID 41532001 )

. B ens ulide is slightly mobile in the four soils tested (K oc 's ranged from 1,433 to 4,326 mL/g) based on an acceptable study (MRID 42826701); however, its major degradate bensulide oxon (average K oc = 557, MRID 43180701) and the minor degradate benzenesulphonami de (average K oc = 17.72

, MRID 43180702) ranged from moderately mobile to highly mobile in the same four test soils.

Ground spray applications may potentially result in transport and loading of bensulide to
off

- field soil

, and foliage , and water bodies vi a spray drift. Granular ground application methods are not expected to result in granules being distributed to off

- field soil; however

on

- field b ensulide soil residues, from either ground spray or granular application methods, have the potential to be tran sported both dissolved in water and on suspended
soil in runoff to off

- field terrestrial areas and to adjacent surface waters. Once in the aquatic system, bensulide is expected to partition primarily to sediment where it will be relatively stable. B ensulid e is not expected to leach to ground water , but bensulide oxon7

may leach to ground water due to its higher solubility and mobility.

There are six submitted field dissipation studies classified as supplemental. T hree w ere conducted in California with reporte d half

- lives rang ing from 15

- 34 days (MRID 40534902, 40534904 and 40534905)

. Three were conducted in Mississippi with half

lives rang ing from 30

- 210 days (MRID 40534901, 40534903 and 40534906). The field dissipation data confirmed the laboratory findings t hat bensulide is a persistent herbicide.
Bensulide and b ensulide oxon were detected 6

- 12 inches deep in soil in both California (MRID 40534902, 40534904 and 40534905) and Mississippi (MRID 40534901, 40534903 and 40534906).

Bensulide may bioconcentrate i n fish with a whole body bioconcentration factor (BCF) of
550 . However, 98% of the compound is eliminated after 14 days depuration

, once residues are removed from the water. Therefore, b ensulide may bioaccumulate in fish but
not at levels of concern (MRID 41931001). B iomagnification up through the food web is not expected to be a significant transport pathway

.

M ode of Action and Residues of Concern

B ensulide

, ( O,O

- diisopropyl S

- 2

- phenylsulfonylaminoethyl phosphorodithioate), is a pre

emergen ce non

- syst em ic, organophosphate herbicide, which acts on c onjugation of plant acetyl co

- enzyme A by inhibiting meristematic root tissues and preventi ng cell division in root tips (Ware, 1978; Martin, 2000)

. The mode of toxic action to non

- target organisms ( e.g. , mamma ls) is via the inhibition of cholinesterase and accumulation of acetylcholine at the nerve synapses, resulting in classic symptoms of organophosphate poisoning

.

Both bensulide and bensulide oxon ( up to 13.8% in aerobic soil ) are the residues of

concern s in drinking water (USEPA 2009).

Surface Water Modeling

D rinking water from surface water source s is often subject ed to water treatment via
chlorination . During chlorination

, t he parent bensulide may be totally convert ed into
bensulide oxon during the pr ocess ( Kamel et al. , 2009 ). Therefore, a total toxic residue (TTR) approach was used in this assessment for surface water exposure, in which all
residues of bensulide are assumed to be converted to the oxon

. Therefore, bensulide and
its oxon are summed in this assessment as oxon equivalents.

Table 4 shows the modeling input parameters based on TTRs

. The EDWCs in s urface

w ater source s were generated using the Tier II Surface Water Concentration Calculator (SWCC v 1.106 , USEPA 2014 ) , which is a graphical use r interface that runs the Pesticide Root Zone Model and the Variable Volume Water Body Model. The default percentage crop area ( PCA ) of 1.0 was used due to the use of bensulide on non

- agricultural setting s (USEPA 2012 b ).8

Table 4

. SWCC Inputs for Bensul ide Total Toxic Residues

Input variable (Units) Input value and
calculations Source Justification

Crop name See Table 2

Product labels Application method Ground

Application rate (lb a.i./acre) See Table 2

Application Date (M/D) 4/1 and 8/1

o r 2/1, 6/1 and 10/1

Application interval (days) >120 days

Application efficiency

Ground spray 0.99

EFED i nput parameters and spray drift guid ances

(USEPA 2009 a , 2013) Spray drift fraction

Ground spray 0.066

Application efficiency

Granular g round broadcast 1

Spray drift fraction

Granular ground broadcast 0

M olecular W eight (g/mole) 397.5 MRID 45761801 (Value for parent)

Vapor pressure @ 25 o C ( mm Hg ) 2.48 10

- 8 EPI Suite (v 4.10)

Solubility in Water (mg/L) 461 EPI Suite (v 4.10) (Maxi mum value for bensulide oxon)

Aquatic photolysis t 1/2 (day) 173 (40°N latitude) TTR half

- life for parent and oxon ( MRID
40513401 ) calculated using PestDF

Aerobic soil met. t 1/2 (day) 2,247 (25°C) 749 (TTR half

- life for parent and oxon; MRID 40460301) x 3 to account for potential variability across soils EFED guidance, USEPA
2009 a

Hydrolysis t 1/2 (day) @ 25 ° C, pH 7 220 MRID 00160074 (Value for parent

- bensulide oxon not
formed )

Aerobic aquatic met. t 1/2 (day) 4,494 (25°C) No data; (soil aerobic

met. half

- life x 2 EFED guidance; USEPA

2009 a )9 Input variable (Units) Input value and
calculations Source Justification

Anaerobic aquatic met. t 1/2 (day) 0 MRID 40460302 “0” indicates stability,

based on the anaerobic soil metabolism study
results

K oc ( ml/g) 557 MRID 43180701 Average of 4 values for
bensulide oxon

Table 5 shows t he EDWCs of TTRs as bensulide oxon equivalent

. T he recommended

EDWCs from surface water source s are not expected to exceed 979 μg/L for the 1 in 10 year daily peak concentration, 494 μg/L for the 1 in 10 year annual concentration, and 305 μg/L for t he 30 year annual average concentration based on the California lettuce use
scenario

. The peak value ( 979 μg/L ) of the TTRs ( bensulide oxon equivalent s ) is the

same as the previous recommended bensulide peak value ( 979 μg/L ) ( USEPA 2000 ). An example SWCC o utput summary is shown in Appendix I

.

Table 5

. Surface Water EDWCs for Bensulide TTRs A

Scenario Application

Method Single

Application

Rate (lbs ai/ a cre ) No. and

Date(mm/dd)
of Applications Concentration (μg/L)

1 in 10

yr Peak 1 in 10 yr

Annual Aver age 30 year

annual

average

FL Turf (W128 3 4.dvf) Granular

Broadcast 16 2 and (4 /1 , 8/1 ) 554 256 166

PA Turf (W12834.dvf) Granular

Broadcast 16 2 and (4/1, 8/1) 946 409 244

TurfBSS (W13958.dvf) Granular

Broadcast 16 2 and (4/1, 8/1) 605 267 170

CA TurfR LF (W2 3 234 .dvf) Granular

Broadcas 16 2 and (4/1, 8/1) 697 372 208

FL Turf (W12834.dvf) Ground Spray 12.5 2 and (4/1, 8/1) 195 104 80

PA Turf (W 14751 .dvf) Ground Spray 12.5 2 and (4/1, 8/1) 2 80 1 33 95

TurfBSS (W13958.dvf) Ground Spray 12.5 2 and (4/1, 8/1) 213 105 79

CA TurfRLF (W2 3 234 .dvf) Ground Spray 12.5 2 and (4/1, 8/1) 205 129 87

FL Peppers (W1284 4.dvf) Ground Spray 6 3 and (2/1,

6 /1 , 10/1 ) 532 173 11 3

FL Cabbage (W12842 .dvf) Ground Spray 6 3 and (2/1,

6 /1 , 10/1 ) 49 4 164 123

CA Lettuce (W2 32 73 .dvf) Ground Spray 6 3 and (2/1,

6 /1 , 10/1 ) 979 494 305

CA Avocado (W23188 .dvf) Ground Spray 6 3 and (2/1,

6 /1 , 10/1 ) 179 100 73

A Maximum values in bold.10

G roundw ater Modeling

The maximum amount of bensulide oxon formation i s 13.8% in a submitted ae robic soil
metabolism study ( MRID 40460301) . T his percentage and the molecular weight ratio of
bensulide to its oxon were used to calculate the bensulide oxon conversion rate for modeling groundwater exposure to the oxon

. For example, for t he maximum singl e application rate of bensulide

, 1 6 lbs ai/acre

, the equivalent application rate for the
bensulide oxon is 2.12 lbs ai/acre (16 × 13.8% × 381.44/397.54 )

. The maximum annual application rate s for bensulide and bensulide oxon represent the above single maxi mum

rates times 2 applications that occur four months apart ( Table 6 )

.

The EDWCs from g roundwater source s for bensulide and bensulide oxon were simulated separately using the Tier 1 PRZM

- GW model (USEPA, 2012 c,d ). P RZM

- GW is a one

dimensional, finite

- di fference model that estimates the concentrations of pesticides in groundwater. It accounts for pesticide fate in the crop root zone by simulating pesticide soil transport and degradation after a pesticide is applied to an agricultural field. PRZM

GW permit s the assessment of multiple years of pesticide application (up to 100 years) on a single site. Six standard scenarios, each representing a different region known to be vulnerable to groundwater contamination, are available for PRZM

- GW simulations.

PRZM

- GW output values represent pesticide concentrations in a vulnerable groundwater supply that is located directly beneath a rural agricultural field. The breakthrough time ( i.e.

, the number of days that it takes for the applied chemical to reach the aquifer) i s simulated for 30 years or for 100 years (using extended weather files) to determine

EDWCs. PCAs are not applicable to the PRZM

- GW model. The fate input parameters
used for bensulide and bensulide oxon PRZM

- GW modeling are listed in Table 6

.

Table 6

. P RZM

- GW Inputs for B ensulide and Its O xon Degradate

Data Units Value Source Comments

Bensulide

The maximum application rate of
bensulide 16 lbs ai/acre for 2 applications on 3 /1 and 7/1 (4

- month interval )

Aerobic Soil
Metabolism Days 1,089 MRID 404 60301 bensulide (363 × 3 ) ( USEPA, 2009 a )

Soil:Water Coefficient (K
oc ) L/g 2

, 884 MRID 43180701 Average of 4 values
for bensulide ( USEPA 2009 a ) Hydrolysis t 1/2 (day) @ 25

° C and (pH 7) 220 MRID 00160074

Bensulide Oxon

The maximum application rate of
bensulide oxon through
aerobic soil
transformation 2.12 lbs ai/acre for 2 applications on 3 /1 and 7/1 (4

- month interval ) *

*16 × 13.8% (application rate conversion based on aerobic soil metabolism) × 96% (molecular wt conversion) = 2.12 lbs ai/acre

Ae robic Soil
Metabolism Days 2,247 MRID 40460301 B ensulide oxon ( 749

× 3 ) ( USEPA, 2009 a )

Soil:Water Coefficient MRID 43180701 Average of 4 values11

(K
oc ) L/g 557 for bensulide

, ( EFED
Guideline 2009 a ) Hydrolysis t 1/2 (day) 0 No data Stable is assumed

The EDWCs of bensulide and bensulide oxon from ground water source s in six vulnerable
sites ar e shown in Table 7

. Since the oxon concentrations peak much higher and earlier than the bensulide concentrations, the oxon concentrations are recommended for us e in dietary risk assessment. The recommended EDWCs for oxon are not expected to exceed the highest daily value s of 1,250 μg/L and the post

- breakthrough average s of 1,200 μg/L with average simulation breakthrough time of 7,106 days for North Carolina Coastal
Plain scenario

. The above oxon peak EDWC at 1,2 5 0 μg/L supersede s the previous
recommended bensulide EDWC at 1 μg/L by SCI

- GROW model (USEPA 2000)

. E xample s of PRZM

- GW modeling analysis are shown in Appendix I I

.

Table 7

. Groundw ater EDWCs Derived by PRZM

- GW for Bensulide and Bensulide
Oxon in Six Vulnerable Sites A

Crop/Scenario Highest Daily Value μg/L Post Breakthro ugh

Average μg/L Average Simulation

Breakthrough Time Days

Bensulide Oxon Bensulide Oxon Bensulide Oxon

DELMARVA sweet

corn

- Evesboro loamy
sand
Met File (w13781 Extended .dvf) 216 864 211 728 35733 7630

Florida Citrus

- FL Central Ridge, Polk

C ounty Astatula sand, hrgb A. Met File ( w12842Extended.dvf

) 374 943 360 898 29632 6321

Florida

- potato
Jacksonville
Met File ( w 13889Extended.dvf) 1.28 348 Incomplete breakthrough 326 Incomplete breakthrough 12730

GA

- Southern Coastal
Plain , Tifton loamy
sand

– PEANUTS
Met File (w93805Extended.dvf) 7.69 234 Incomplete breakthrough 219 Incomplete breakthrough 10 448

NC Eastern Coastal
Plain

- Norfolk loamy
sand

– Cotton
Met File ( w 13722 Extended .dvf) 48.8 1,250 46 1,200 29084 7106

Wisconsin Corn

- WI
Central Sands
Met File ( w 14920 Extended .dvf) 17 3 915 Incomplete breakthrough 815 Incomplete breakthrough 9830

A The recommended EDWC values are in bold.12

Monitoring Data

No monitoring data were found for bensulide and bensulide oxon in the U.S. Geological Survey ( USGS) National Water Quality Assessment ( NAWQA ) surface and ground water
databases. In an ambient monitoring report by California Department of Pesticide Regulation, bensulide had a detection frequency of 55% out of 51 s amples in surface

water with the highest value at 14 ppb ( Starner, K. 201 3 )

.

Assumptions, Uncertainties, and Limitations

1. The aerobic soil metabolism study for bensulide evaluated only one soil

, with a
half

- life of 363 days. The TTR half

- life was 749 da ys with the inclusion of
bensulide oxon. Because the registrant only submitted data for one soil type, model inputs were conservatively multiplied by three to account for potential variability across soils, following EFED guidance (USEPA, 2009 a )

. If the da ta for more soil types we re available, the modeled aerobic soil metabolism half

- life
could be reduced.

2. The modeled aerobic aquatic metabolism half

- life was calculated by multiplying
the aerobic soil metabolism half

- life by 2 (t 1/2 = 2,247 × 2 = 4,494 days) due to the absence of data, following EFED guidance (USEPA, 2009 a )

. 3. Bensulide oxon hydrolysis is assumed to be stable because of no data.

4. The current labels do not fully specify the application rates, number of applications, and minimum retreatment inte rvals. Label clarifications for some of the uses are necessary to reduce the uncertainty. As such, a ny application rate
exceeded the label rates listed in Table 1 is beyond the scope of this assessment.
5. Groundwater sourced drinking water is seldom chlorin ated. Therefore, bensulide was not assumed to convert 100% to the oxon but only the portion from the

a erobic soil metabolism (13.8%). However, w hen chlorinated, high

- end groundwater EDWCs should be similar regardless of whether bensulide is
assumed to co nvert to the oxon during potential drinking water treatment based on the current bensulide peak concentration at 374 μg/L in groundwater

.

References

Kamel, A., C. Byrne, C. Vigo, J. Ferrario, C. Stafford, G. Verdin, F. Siegelman, S. Knizner, and J. He trick. 2003. Oxidation of selected organophosphate pesticides during chlorination of simulated drinking water. Water Research 43:522

– 534.

Starner, Keith, 2013. Study 282. Surface Water Monitoring for Pesticides in Agricultural Areas of California, 2 013, Department of Pesticide Regulation Environmental Monitoring Branch 1001 I Street Sacramento, California 95812. 77pp.

USEPA. 199 7

. Drinking W ater Assessment for Bensulide. EFED, 11/21/1997. PC Code: 009801). DP Barcode: None. 11pp.13

USEPA. 2000. R evised Estimated Environmental Concentrations in Ground and Surface Water for Bensulide used on Golf Course Fairways. EFED, 2 / 10 / 20 00. PC Code
009801

. DP Barcode: None

. 6 pp.

USEPA. 2009. Guidance for Registration Review Data Requests for Oxon Degradate s of Organophosphate Insecticides (OP) . U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division. Internal memorandum. Mar. 10, 2009.

USEPA. 2009 a . Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides. Version 2.1. U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects Division. Oct. 22, 2009.

USEPA. 2012a. Bensulide label Data Report as of 1/11/2012, also called label use information system (LUIS) report by Biological and Economic Analysis Division (BEAD).

USEPA. 2012b. Guidance on Development and Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments:

2012 Update. March 16, 2012 Memo. 50pp.

USEPA. 2012c . Approval of PRZM

- GW for Use in Drin king Water Exposure

Assessment. EFED Memo 12/11/2012. Pp. 1.

USEPA. 2012d . Guidance for PRZM

- GW in Drinking Water Exposure Assessment. October 15, 2012. Pp. 20

U SEPA. 2013. Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water Assessments. EFED Memo 12/20/2013. 40pp.

USEPA. 2014. Surface Water Concentration Calculator User Manual. OPP 734F14001, July 1, 2014.

USEPA. 2015. Updated Screening Level Usage Analysis (SLUA) Report f or Bensulide, PC Code (009801). July 10, 2015. Biological a nd Economic Analysis Division. 3pp.14



## APPENDIX I

. Example s of SWCC Modeling

Summary of Water Modeling of Bensul ide and Bensulide Oxon
and the USEPA Standard Reservoir

Estimated Environmental Concentrations for Bensulide and Bensulide Oxon are presented in Table 1 for the USEPA standard reservoir with the CAlettuceSTD field scenario. A graphical presentation of the year

- to

- year peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are summarized in Tables 2 and 3.
This model estimates that about 2.8% of Ben sulide and Bensulide Oxon applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by runoff (91.5% of the total transport), followed by spray drift (7.08%) and erosion (1.39%).
In the wate r body, pesticide dissipates with an effective water column half

- life of 114.1 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete system.)
The main source of dissipation in the water column is hydrolysis (effective average half

life = 220.3 days) followed by washout (245.1 days), metabolism (9953.9 days), photolysis (22176.9 days), and volatilization (1.26054E+07 days). In the benthic region, pes ticide dissipation is negligible (13454.8 days). The main source of dissipation in the benthic region is hydrolysis (effective average half

- life = 13454.8 days). The vast majority of the pesticide in the benthic region (98.36%) is sorbed to
sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for Bensulide and
Bensulide Oxon.

Peak (1

- in

- 10 yr) 979.

4

- day Avg (1

- in

- 10 yr) 966.

21

- day Avg (1

- in

- 10 yr) 907.

60

- day Avg (1

- in

- 10 yr) 801.

365

- day Avg (1

- in

- 10 yr) 494.

Entire Simulation Mean 305.

Table 2. Summary of Model Inputs for Bensulide and Bensulide Oxon.

Scenario CAlettuceSTD

Cropped Area Fraction 1.0

Koc (ml/g) 557

Water Half

- Life (days) @ 25 °C 4494

Benthic Half

- Life (days) @ 25 °C 015

Photolysis Half

- Li fe (days) @ 40

°Lat 173

Hydrolysis Half

- Life (days) 220

Soil Half

- Life (days) @ 25 °C 2247

Foliar Half

- Life (days)

Molecular Wt 397.5

Vapor Pressure (torr) 2.48e

- 8

Solubility (mg/l) 461

Table 3. Application Schedule for Bensulide and Bensulide Oxo n.
Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

2/1 Foliar 6.72 .99 .066

6/1 Foliar 6.72 .99 .066

10/1 Foliar 6.72 .99 .066

Figure 1. Yearly Peak Concentrations16



## Summary of Water Modeling of Bensulide and Bensulide Oxon
and the USEPA Standard Res ervoir

Estimated Environmental Concentrations for Bensulide and Bensulide Oxon are presented in Table 1 for the USEPA standard reservoir with the PAturfSTD field scenario. A graphical presentation of the year

- to

- year peaks is presented in Figure 1.
These v alues were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are summarized in Tables 2 and 3. This model estimates that about 0.98% of Bensulide and Bensulide Oxon applied to the
field even tually reaches the water body. The main mechanism of transport from the field to the water body is by runoff (92.3% of the total transport) followed by erosion (7.66%). In the water body, pesticide dissipates with an effective water column half

- life of 152 .1 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete system.) The main source of dissipation in the water column is hydrolysis (effective aver age half

life = 220.3 days) followed by washout (527.8 days), metabolism (9449.1 days), photolysis (27435.1 days), and volatilization (1.651258E+07 days). In the benthic region, pesticide dissipation is negligible (13454.8 days). The main source of dissipa tion in the benthic region is hydrolysis (effective average half

- life = 13454.8 days). The vast majority of the pesticide in the benthic region (98.36%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations ( ppb) for Bensulide and
Bensulide Oxon.

Peak (1

- in

- 10 yr) 946.

4

- day Avg (1

- in

- 10 yr) 925.

21

- day Avg (1

- in

- 10 yr) 850.

60

- day Avg (1

- in

- 10 yr) 735.

365

- day Avg (1

- in

- 10 yr) 409.

Entire Simulation Mean 244.

Table 2. Summary of Model Inputs for Bensul ide and Bensulide Oxon.

Scenario PAturfSTD

Cropped Area Fraction 1.0

Koc (ml/g) 557

Water Half

- Life (days) @ 25 °C 4494

Benthic Half

- Life (days) @ 25 °C 0

Photolysis Half

- Life (days) @ 40

°Lat 17317

Hydrolysis Half

- Life (days) 220

Soil Half

- Life (days ) @ 25 °C 2247

Foliar Half

- Life (days)

Molecular Wt 397.5

Vapor Pressure (torr) 2.48e

- 8

Solubility (mg/l) 461

Table 3. Application Schedule for Bensulide and Bensulide Oxon.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

4/1 Incorporated to 0

cm 17. 92 1 0

8/1 Incorporated to 0

cm 17.92 1 0

Figure 1. Yearly Peak Concentrations18



## APPENDIX II

. Example s of PRZM

- GW Modeling

Groundwater Analysis for Bensulide Oxon and the NC Eastern
Coastal Plain

- Norfolk Loamy Sand

- Cotton Scenario
Estimated groundwater concentrations and breakthrough times for Bensulide Oxon are presented in Table 1 f

or the NC Eastern Coastal Plain

- Norfolk loamy sand

- Cotton groundwater scenario. A graphical presentation of the daily concentrations in the aquifer is presented in Figure 1. These values were generated with the PRZM

- GW (Version 1.07). Critical input va lues for the model are summarized in Tables 2 and 3.

Table 1. Groundwater Results for Bensulide Oxon and the NC Eastern Coastal
Plain

- Norfolk loamy sand

- Cotton Scenario.

Peak Concentration (ppb) 1.25E+03

Post

- Breakthrough Mean Concentration (ppb) 1 .2E+03

Entire Simulation Mean Concentration (ppb) 541

Average Breakthrough Time (days) 7106.488

Throughputs 1.542253

Table 2. Chemical Properties for Groundwater Modeling of Bensulide Oxon .

Koc (ml/g) 557

Surface Soil Half Life (days) 2247

Hyd rolysis Half Life (days) 0

Diffusion Coefficint Air (cm2/day) 0

Henry's Constant 0

Enthalpy (kcal/mol) 0.0

Table 3. Pesticide application sc heme used for Bensulide Oxon . T his application scheme was applied every year of the simulation.

Application D ate
(Month/Day) Application Method Application Rate
(kg/ha)

3/1 Ground application with mass

distribution increasing proportionally with depth to 4 cm 2.374419

7/1 Ground application with mass

distribution increasing proportionally with depth to 4 cm 2.374 4

Figure 1. Aquifer Breakthrough Curve for Bensulide Oxon and the NC Eastern
Coastal Plain

- Norfolk Loamy Sand

- Cotton Scenario