UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION

PC Code: 129009

DP Barcode: 391086 

Date: 3/15/12 

MEMORANDUM

SUBJECT: Tier I Estimated Drinking Water Concentrations of Rimsulfuron, for the 

Use in the Human Health Risk Assessment: New Use Request for the Use 

of Rimsulfuron on “Chryosolite” Variety of Sulfonylurea Tolerant 

Chicory. 

TO: Andrew Ertman, Risk Manager Reviewer 

 Barbara Madden, Risk Manager 

 Herbicide Branch 

 Registration Division (7505P) 

AND: Cassi Walls, Lead Assessor 

Paula Deschamp, Chief 

Registration Action Branch III 

Health Effects Division (7509P) 

FROM: Michael Barrett, Senior Chemist 

 Environmental Risk Branch 5 

 Environmental Fate and Effects Division (7507P) 

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

 Environmental Risk Branch 5 

 Environmental Fate and Effects Division (7507P) 

 

This memorandum updates the Tier 1 Estimated Drinking Waters Concentrations 

(EDWCs) for surface and ground waters for rimsulfuron, a pyrimidinyl sulfonylurea 

herbicide (CAS name: N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-

(ethylsulfonyl)-2-pyridinesulfonamide; CAS No. 122931-48-0), calculated using the Tier 

1 aquatic models FIRST and SCI-GROW, for use in the human health risk assessment. 

This update is based upon a Section 3 New Use request for the use of Rimsulfuron 

[BASIS® Herbicide (Reg. No. 352-571)]. The application is for the use of this product 

only on the “Chrysolite” variety of sulfonylurea tolerant chicory. The proposed 
 2

application rate is 0.3 ounces per acre, which is equivalent to 0.00938 lb ai/acre. The 

product, BASIS®, contains two active ingredients that include thifensulfuron methyl at 

25% and rimsulfuron at 50% by weight; only exposure to rimsulfuron is addressed in this 

review. 

Drinking water exposure to rimsulfuron has previously been estimated (DP Barcode 

D384624; 10/27/11) for other uses which drive exposure according to the Tier 1 

modeling; the new use at a much lower rate (i.e., maximum annual application of 0.00938 

lb ai/acre versus 0.06250 lb ai/acre). We have updated, however, the previous estimates 

based upon a revision of the aerobic soil degradation rate for rimsulfuron using data 

submitted under MRID 48332003; please see the Appendix for a summary of the model 

input. We additionally note that there is no difference in the use pattern for the new use 

on chicory that would modify the inputs for the Tier 1 modeling to the extent that the 

highest previously calculated estimated drinking water concentrations would change. 

Should there be the need; additional levels of refinements are possible with a higher tier 

assessment. 

For rimsulfuron, the surface water acute drinking water exposure value has been revised 

slightly downward to be 5.396 ppb or ug/L (previously 5.596 ppb), and the cancer/ 

chronic value is now 0.116 ppb (previously it was 0.120 ppb). The groundwater screening 

concentration from the highest exposure uses of rimsulfuron associated with drinking 

well water is now 0.029 ppb (previously it was 0.016 ppb of rimsulfuron). The 

groundwater screening concentration is suitable for acute and chronic exposure (see the 

Appendix for further details on the updated modeling). 
 3

APPENDIX: Exposure Modeling Input and Output 

Below is a revised input parameter model 

Table A1. FIRST input parameters for modeling drinking water EDWCs

Input Parameter Value* Reference

Application Rate (lb a.i./Acre) 0.0625 (One Application) Maximum label rate/Minimum application 

Application Intervals (days) Does not apply, 1 applic. intervals (Product Label) 

Percent Crop Area 0.83 Corn and soybeans 

Partition Coefficient “KOC” (L/Kg) 19 Lowest non-sand value (MRID 413563-36) 

Aerobic Soil Metabolism Half-life 

(days) 44.8 

Determined by calculating 90th percentile 

confidence bound on the mean half-life 

value (MRID 413563-34 and 483320-03); 

the half-lives from the 3 available studies 

were 21.3, 21.5, and 48.1 days. 

Wetted In? No 

Depth of Incorporation (inches) 0 Product Label 

Method of Application Aerial 

Solubility in Water (ppm) 7.3 MRIDs: 419316-02 and 413563-01.

Aerobic Aquatic Metabolism Half-life 

(days) 

The experiment was exposed to artificial light source thus the value was 

not used and hydrolysis half-live was entered. 

Hydrolysis Half-life @ pH 7 (days) 7.2 Average value at pH 7 (MRID 413563-33) 

Direct Aqueous Photolysis Halflife(days) Stable Half-lives in dark<irradiated samples 

(MRID 419316-08) 

* Fate data values are as per Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides; Version II, February 28, 2002. 

Table 7. SCI-GROW input parameters for modeling drinking water from ground water 

(EDWCs). 

Input Parameter Value Reference

Application Rate (lb a.i./Acre) 0.0625 Maximum Yearly Application rate (Product 

Label) 

Maximum Number of Applications/Year 1 

Partition Coefficient “Koc” (L Kg-1) 55 

Median of 4 values (<3 fold variations in Kocs

(MRID 413563-36) 

Aerobic Soil Metabolism Half-life (days) 30.3 

Average of half-lives measured in 3 soils (MRID 

413563-34 and 483320-03) 
 4

FIRST Model Output files 

 RUN No. 2 FOR Rimsulfuron ON Fruit Tree * INPUT VALUES * 

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

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

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

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

 .063( .063) 1 1 19.0 7.3 GROUND( 6.4) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 64.00 2 7.20 .00- .00 .00 7.20 

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 5.445 .117 

 RUN No. 4 FOR Rimsulfuron ON Fruit Tree * INPUT VALUES * 

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

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

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

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

 .063( .063) 1 1 19.0 7.3 GROUND( 6.4) 87.0 .0 

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED 

 (FIELD) RAIN/RUNOFF (RESERVOIR) (RES.-EFF) (RESER.) (RESER.) 

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

 44.80 2 7.20 .00- .00 .00 7.20 

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

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 5.396 .116 
 5

SCI-GROW Model Output files 

 SCIGROW 

 VERSION 2.3 

 ENVIRONMENTAL FATE AND EFFECTS DIVISION 

 OFFICE OF PESTICIDE PROGRAMS 

 U.S. ENVIRONMENTAL PROTECTION AGENCY 

 SCREENING MODEL 

 FOR AQUATIC PESTICIDE EXPOSURE 

 

 SciGrow version 2.3 

 chemical:Rimsulfuron 

 time is 3/15/2012 12:50:11 

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

-- 

 Application Number of Total Use Koc Soil Aerobic 

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism 

(days) 

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

-- 

 30.300 1.0 30.300 5.50E+01 30.3 

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

-- 

 groundwater screening cond (ppb) = 1.39E+01 

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

* 

 

 SciGrow version 2.3 

 chemical:Rimsulfuron 

 time is 3/15/2012 12:51:55 

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

-- 

 Application Number of Total Use Koc Soil Aerobic 

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism 

(days) 

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

-- 

 0.063 1.0 0.063 5.50E+01 30.3 

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

-- 

 groundwater screening cond (ppb) = 2.86E-02 

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

*