### 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### MEMORANDUM Date: April 3

, 2012

DP Barcode: D 39377 7 and 397770

PC Code 129081

SUBJECT: Drinking Water Exposure Assessment for the Section 3 New Use Registration

of Sulfentrazone on R hubarb, Turnip roots and tops, Sunflower Subgroup 20B, Succulent Cowpea, Succulent Lima Bean, Wheat (Spring), Citrus Fruit Crop Group 10

- 10, Low Growing Berry C rop Group 13

- 07, Tree Nut Crop Group 14 and Pistachios, and Crop Group 18: Nongrass Animal Feeds

TO: Barbara Madden , Risk Manager Laura Nollen, Risk Manager Reviewer Registration Division (7504P)

Julie Langsdale Van Alstine

, Chemist Dana Vogel , Chief

R isk Assessment Branch 1
Health Effects Division (7509P)

FROM: Michael R. Barrett, Senior Chemist

Environmental Risk Branch V
Environmental Fate and Effects Division (7507 P )

THROUGH: Mah T. Shamim, Ph.D., Chief

Environmental Risk Branch V

Environmental Fate and Effects Division (7507 P )

EFED has evaluated the proposed new uses on several crops (listed in Table 1 and determined that no changes are needed in the sulf entrazone drinking water exposure estimate s from the previous assessment (see DP Barcode D 349322; dated 8/28/2008 ; updated modeling showing no change in the estimated drinking water concentrations is located in the Appendix to this review )

.

### 2 Application rat es for the new uses (up to 0.375 lbs ai/A per season) are the same as for previously assessed uses and the addition of these uses does not change exposure estimates from the previous assessment (see Table 2 for a summary of these estimates )

. In general, sulfentrazone is persistent and mobile (for example, a 545

- day aerobic soil half

- life 1 

### and an average Koc coefficient of 45 ml/g), and has a strong potential to leach into groundwater (this conclusion is reinforced by the four completed small

- scale prospective ground

- water monitoring studies for

sulfentrazone ) and move offsite to surface wa ter , discussed below)

.

Table 1

. New use information for sulfentrazone (based on proposed labels).

PROPOSED USE EPA Reg NO. SINGLE

APP.

RATE

(lb.
a.i./A) NUMBER

OF APPS. SEASONAL

APP. RATE

(lb. a.i./A) INTERVAL

BETWEEN

APP S . (days) APP.

METHOD PHI (days)

Rhubarb

279

- 3149

279

- 3189 0.07

- 0.375 1

- 2 or Not Specified 0.375 Not specified Preplant, Pre

emergent

Ground
(Broadcast
soil, banded, chemigation ) 3

- 120 Turnip roots and tops

Sunflower Crop Subgroup

20B

Spring wheat

Succulent cowpea

Succulent lima beans

Tree nut Crop Group 14 including pistachios

Citrus Crop Group 10

Small berry and fruit Crop
Group 13

- 07

Non

- grass animal feed
Crop Group 18



### Table 2

. Estimated Tier 1 Concentrations of s ulfentrazone and 3

- c arboxylic a cid s ulfentrazone in

d rinking w ater d ue to the u se of s ulfentrazone on crop sites such as s ugarcane, c abbage, p otatoes,

m int, or h orseradish

.

Chemical Surface Water (ug/L) Groundwater (ug/L)

Acute Chronic Acute and Chronic

Sulfentrazone 32. 1 5. 1 15.7

3

- Carboxylic Acid Sulfentrazone 3. 7 2.7 10.3

Total 35.8 7.8 26.0

1 90 th percentile upper confidence interval of the mean half

- life for all soils tested

.

### 3 Prospective groundwater monitoring data have been submitted to the Agency for four sites tracking the movement of sulfentrazone and its degradate through the soil profile into groundwater after application. Maximum groundwater concentrations observed in ea ch of these

four studies are summarized in Table 3 . The four sites were selected by the registrant to be representative of >99 th 

### (NC1 site), 95 th 

### (IN1 site), 85 th 

### (IN 2 site), and 75 th 

### (IN3 site) percentile groundwater vulnerability in likely sulfentrazone use areas at the time of the studies. Although the maximum concentration observed at the NC1 site was higher than the estimated exposure

from all sources for the comb ined residues, we continue to recommend use of the modeled values for Tier 1 drinking water estimation. This is because the conditions at this study site ( by

far the most vulnerable conditions of the test sites , but all four sites had high groundwater

vuln erability ) are unlikely to be reproduced at a drinking water well site.

Table 3

. Maximum ob served concentrations of sulfentrazone and its acid degradate in shallow groundwater below or immediately downgradient of treated fields at four sites compared to Tier

1 estimated concentrations using the SCI

- GROW model

.

Chemical NC1

Site IN1

Site IN2

Si te IN3

Site SCI

GROW

Concentration in ppb (days after initial applic. of obs.)

Sulfentrazone 37.4

(160d) 0.86

(577d) 0.11

(153d) 0.26

(634d) 15.7

3

- Carboxylic Acid Sulfentrazone 11.4

(160d) 2.50

(455d) <5

(variable) 1.61

(1499d) 10.3

SITE DESCRIPTIONS:

NC1 = The test site was located near the town of near Tarboro in Edgecombe County, North Carolina, and was located in a setting classified as vey high vulnerability to groundwater contamination. Soil series = Tarboro sand to loamy sand. Sulfe ntrazone application rate = 0.50 lb ai/acre. (MRID 43345434 and 43926814 ). Average depth to groundwater = 9.2 feet.

IN1 = The test site was located near the town of Leesburg in Kosciusko County, Indiana, and was located in a setting classified as 85 th percentile in terms of vulnerability to groundwater contamination. Soil series = Tyner loamy sand to sandy loam. Sulfentrazone application rate = 0.17 lb ai/acre. Average depth to groundwater = 18.9

feet. (MRID 46816001 ).

IN2 = The test site was located near the town of Hanna in LaPorte County, Indiana, and was located in a setting

classified as 95 th percentile in terms of vulnerability to groundwater contamination. Soil series = Shipshe loamy sand to sandy loam. Sulfentrazone application rate = 0.22 to 0.44 lb ai/acre. Average depth to groundwater = 30 feet.
(MRID 47453601 ).

IN3 = The test site was located near the town of La Porte in LaPorte County, Indiana, and was located in a setting

classified as 75 th percentile in terms of vulnerability to ground water contamination. Soil series = Coupee silt loam. Sulfentrazone application rate = 0.22 lb ai/acre. Average depth to groundwater = 21 feet. (MRID 47453602 ).

### 4 The following conclusions from previous drinking water assessment s are still appropriate with the addition of the newly requested uses on rhubarb, turnip roots and tops, and the sunflower

group crops:

Tier I Estimated Drinking Water Concentrations (EDWCs) for sulfentrazone and its major degradate (3

- carboxylic acid sulf entrazone) were calculated using FIRST (surface water) and SCIGROW (ground water) for use in the human health risk assessment. EFED believes that the Tier I models used for these crops provide a reasonable worst case scenario and provide estimates suitable for screening purposes. For surface water, the acute (peak) sulfentrazone value is 32.0 ppb and the annual average value ranges from 0.5 ppb in alkaline or neutral waters (most common) to 5.1 ppb in acidic waters. The groundwater screening sulfentrazone concentration is 15.7 ppb. For 3

- carboxylic acid sulfentrazone, the acute peak is 3.8 2 

### ppb and the annual average is 2.7 ppb. For 3

- carboxylic acid sulfentrazone in groundwater, the concentration is 10.3 ppb.

- Source: DP Barcode: D284975, “Tier I Es timated Environmental Concentrations of Sulfentrazone and Degradate 3

- Carboxylic Acid Sulfentrazone for Use in the Human Health Risk
Assessment”, review document dated 4/17/2003. See also DP Barcode 284975 et al., “EFED

Section 3 and IR

- 4 Registration Chap ter for Sulfentrazone...”, review document dated 6/16/2003

2 

### Current model runs estimate a peak of 3.735 ppb which is not significantly different.

### 5 

## APPENDIX

Updated FIRST Modeling Inputs and Results ( for additional details see DP Barcode: D28497;
review dated 4/17/2003) :

FIRST Output File

RUN No. 1 FOR Sulfentrazone ON Citrus etc * INPUT VALUES *

--------------------------------------------------------------------

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .375( .375) 1 1 43.0 400.0 AERIAL(16.0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

-------------------------------- ------------------------------------
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

--------------------------------------------------------------------

545.00 2 N/A .50

- 62.00 ****** 58.66

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVE RAGE (CHRONIC)

CONCENTRATION CONCENTRATION

-------------------------------------------------------------------- 32.102 5.047

RUN No. 3 FOR Sulfentraz. acid ON Citrus Etc * INPUT VALUES *

--------------------------------------------------------------------

RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

-------------------------------------------------------------------- .041( .041) 1 1 .0 400.0 GRANUL( .0) 87.0 .0

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS)

--------------------------------------------------------------- -----
METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES.

- EFF) (RESER.) (RESER.)

-------------------------------------------------------------------- .00 2 N/A .00

- .00 .00 .00

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007

-------------------------------------------------------------------- PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC)

CONCENTRATION CONCENTRATION

-------------------------------------------------------------------- 3.735 2.678

### 6 SCIGROW Modeling Input and Results

SCIGROW

VERSION 2.2: NOVEMBER 1, 2001

RUN No. 1 FOR SULFENTRAZONE ** INPUT VALUES **

--------------------------------------------------------

APP RATE APPS/ TOTAL/ SOIL AEROBIC SOIL METAB

(LBS/AC) YEAR SEASON KOC HALFLIFE (DAYS)

-------------------------------------------------------- .375 1 .375 43.0 545.00

GROUND

- WATER SCREENING CONCENTRATION (IN UG/L

- PPB)

-------------------------------------------------------- 15.701670

--------------------------------------------------------



## Results of Vadose Zone Monitoring at Four Prospec tive Groundwater Monitoring Sites

Table 4

. Maximum o bserved concentrations of sulfentrazone and its acid degradate in soil

- pore

water 7

- to 9

- feet below the surface of treated fields at four sites compared to Tier 1 estimated

con centrations using the SCI

- GROW model.

Chemical NC1

Site IN1

Site IN2

Site IN3

Site SCI

GROW

Sulfentrazone 22.5

(186d) 0.28

(911d) 0.35*

(1229d) 0.09

(1149d) 15.7

3

- Carboxylic Acid Sulfentrazone 38.1

(186d) 4.28

(577d) 3.36

(363d) 0.07

(753d) 10.3

* Also at 0.44 ppb 2135 days after the original application after an additional application 1961 days after the initial application. The degradate was detected at a maximum concentration of 0.33 ppb at 2226 days after this last application

.