1

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION

PC Code: 129009

DP Barcode: 384624 

Date: 10/27/11 

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 Caneberry 13-07A and Bushberry Subgroup 13-07B. 

TO: Debra Rate, Acting Team Lead Section 18 and 24C 

Risk Integration, Minor Use and Emergency Response Branch 

Mindy Ondish, Risk Manager Reviewer 

 Kable Davis, Risk Manager 

 Herbicide Branch 

 Registration Division (7505P) 

AND: Elizabeth Holman, Lead Assessor 

Christina Swartz, Chief 

Registration Action Branch II 

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 (IR4) request 
 2

for the use of Rimsulfuron [Matrix SG (water soluble granule) (Reg. No. 352-768)] on 

Caneberry Subgroup 13-07A (cranberry) and Bushberry Subgroup 13-07B (blueberry). Matrix 

SG contains 25% active ingredient by weight in the formulation. The proposed application rates 

are up to a total of 0.0625 lb a.i./A per season, which is consistent with previously registered 

uses. Two applications may be made when using a banded treatment with a minimum of a 30 day 

interval, however, a total of 0.0625 lb a.i./A still should not be exceeded on a per year basis. 

In general, applications can be made by both aerial ground methods and chemigation, but not via 

aerial application methods. 

The previous Tier 1 modeling covers these new uses (see attached copies of reviews under DP 

Barcodes D358869, D358875 (assessment dated 7/24/2009) and D 334221 (2/6/2007). This is 

because there is no difference in the use pattern for these new uses 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 is still estimated to be 

5.596 ppb, and the cancer/ chronic value is still 0.120 ppb. The groundwater screening 

concentration is still 0.016 ppb of rimsulfuron, which is suitable for acute and chronic exposure 

(see Table 1 in the attached assessment from 7/24/2009). 
 3

Electronic Copy of Previous Drinking Waters Analysis (7/24/2009

Assessment)

 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES 

 PC Code 129009 

 DP Barcode D358869, D358875 

Date July 24, 2009 

MEMORANDUM 

SUBJECT: Tier I Estimated Drinking Water Concentrations of Rimsulfuron, 

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

Proposals for the Chemical on DUPONTTM OPTIMUM® GAT® 

Corn and Soybeans

TO: Vickie Walters, Risk Manager Reviewer 

 James Tompkins, Product Manager 25 

 Daniel Kenny, Chief 

 Herbicide Branch 

 Registration Division (7505P) 

AND: Douglas Dotson 

Cristina Swartz, Chief 

 Registration Action Branch II 

 Health Effects Division (7509P) 

FROM: José L. Meléndez, Chemist

 Environmental Risk Branch V 

 Environmental Fate and Effects Division (7507P) 

APPROVED BY: Mah T. Shamim, Branch Chief 

 Environmental Risk Branch V 

 Environmental Fate and Effects Division (7507P) 

 

This memorandum presents the Tier 1 Estimated Drinking Waters Concentrations 
 4

(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 Drinking Waters Assessment (DWA) is largely based on a previous DWA, dated 

February 6, 2007 (electronic copy is provided below). The EDWCs were calculated 

based on the maximum application rate of 0.0625 lb a.i./A/season (for citrus, pome and 

stone fruits, ground broadcast application, wetted in). For rimsulfuron, the surface waters 

acute value is 5.596 ppb, and the cancer/ chronic value is 0.120 ppb. The groundwater 

screening concentration is 0.016 ppb of rimsulfuron, which is suitable for acute and 

chronic (refer to Table 1). EFED stresses the fact that this is a Tier 1 screening-level 

analysis and should there be the need, additional levels of refinements are possible. 

Currently, rimsulfuron is used on a number of crops, including corn (maximum 

application rate for corn, 0.03125 lb a.i./A). EFED evaluated the new uses for 

rimsulfuron on DUPONTTM OPTIMUM® GAT® herbicide tolerant corn and soybean for 

pre-emergence and post-emergence control of certain annual grass and broadleaf weeds. 

The product name is RESOLVETM SG Herbicide (water soluble granule, containing 25% 

a.i.). It was noted that aerial applications are allowed for these uses and the maximum 

application rate is 0.0625 lb a.i./A for both crops (same than the previously assessed for 

citrus, pome and stone fruits). It was evaluated if the new scenarios posed more exposure 

than previously assessed. The results of a FIRST run showed lower EDWCs than the 

previously assessed scenarios (refer to Appendix A for the table of input parameters used, 

and a copy of the output file from FIRST). Therefore, EFED relied on the results of the 

previous DWA for this assessment. It appears that, because the pesticide is not wetted in 

and a specific PCA was used (for corn and soybeans, 0.83), the results were lower for the 

new scenarios. 

None of rimsulfuron’s transformation products were included in this assessment. Based 

on a HED’s March 29, 1994 memorandum, it was concluded that, “None of rimsulfuron’s 

metabolites warrant inclusion in tolerance regulation or separate regulation or inclusion 

in the dietary risk assessment” (refer to Attachment 1 of the attached 2/7/2007 DWA 

Assessment). Rimsulfuron shows significant levels of various transformation products 

that may persist in the environment and may contaminate surface or ground waters. 

For information related to the environmental fate characteristics of rimsulfuron, mode of 

action, uncertainties, etc., please, refer to the previous DWA, provided in Appendix B. 

For any questions related to this document, please, contact us in EFED. 

Table 1. Maximum Tier I EDWCs for drinking water assessment based on ground 

application of rimsulfuron*

Use/Rate Modeled: Fruit trees applied once, by ground sprayers, at a rate of 0.0625 lbs. a.i./A

Chemical

Maximum Surface water EDWC (ppb) Maximum Ground water 

Acute Value Chronic/Cancer Value Acute/Chronic EDWC (ppb)

Rimsulfuron Parent 5.596 0.120 0.016
 5

* Degradates are not included as recommended by HED Metabolism Committee. Please, refer to attached 

2/7/2007 DWA Assessment for further details. 
 6

Appendix A. FIRST Supplementary Run Inputs Parameter Table and 

Output File 

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) 64 

Determined by multiplying the available 

half-life by 3 to account for the uncertainty 

associated with using a single value 

(21.3x3; MRID 413563-34) 

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. 
 7

Appendix A. FIRST Supplementary Run Inputs Parameter Table and 

Output File (cont.)

FIRST Output Run: 

 RUN No. 1 FOR Rimsulfuron ON Soy+Corn * INPUT VALUES * 

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

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

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

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

 0.063( 0.062) 1 1 19.0 7.3 AERIAL(16.0) 83.0 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 0.00 0.00- 0.00 7.20 7.20 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.1 MAR 26, 

2008 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 5.138 0.111 
 8

 Electronic Copy of Previous Drinking Waters Analysis (2/6/2007 

Assessment)

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

 OFFICE OF 

 PREVENTION, PESTICIDES 

 AND TOXIC SUBSTANCES

 

 PC Code No.: 129009 

 DP Barcode: D 334221 

Date: February 6, 2007 

MEMORANDUM 

SUBJECT: Estimated Drinking Water Concentrations of Parent Rimsulfuron for 

the Use in Human Health Risk Assessment.

TO: James Tompkins, Risk Manager 25 

 Vickie Walters, Risk Manager Reviewer 

 John Redden, Team Leader, ARIA 

 Registration Division (7505P) 

AND: Christina Swartz, Branch Chief 

RAB2, HED (7509P) 

FROM: M. A. Ruhman, Agronomist, Environmental Fate Reviewer 

 Environmental Fate and Effects Division (7507P) 

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

Environmental Risk Branch V 

 Environmental Fate and Effects Division (7507P) 

I. EXECUTIVE SUMMARY

This memo presents the Estimated Drinking Water Concentrations (EDWCs) for parent 

Rimsulfuron for use in an FQPA human health risk assessment. It is noted that 

significant quantities of some of rimsulfuron transformation products/degradates may 

persist in the environment and may contaminate surface/ground water. None of these 

transformation products/degradates are included in this risk assessment based on HED 

Metabolism Committee Memorandum dated March 29, 1994. The Committee concluded 

that “None of the rimsulfuron metabolites warrant inclusion in the tolerance regulation or 

separate regulation or inclusion in the dietary risk assessment” (Attachment No. 1). 
 9

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

Rimsulfuron is selective/systemic pyrimidinyl sulfonylurea herbicide. Rimsulfuron is a 

member of the sulfonylurea family1

 with a mode of action that inhibit acetolactate 

synthase ALS (ALS is also known as acetohydroxyacid synthase AHAS) (HRAC Group 

B)2

. ALS or AHAS is a key enzyme in biosynthesis of certain amino acids in plants. This 

herbicide is currently registered as pre/post emergence weeds control in field corn, 

potatoes, potatoes grown for seed, and field grown tomatoes. The registrant is seeking 

new section 3 registration for new use on grapes, stone Fruit, tree nuts, pistachios, pome 

fruit, and citrus fruit. These proposed new uses for rimsulfuron may cause the chemical to 

reach surface and to a lesser extent groundwater under some conditions. 

The screening level surface water and ground water estimates for rimsulfuron parent 

are calculated using tier 1 models of FIRST (version 1.0) and SCI-GROW (version 

2.3), respectively. The estimates are presented in Table 1 for surface/ground water. 

Table 1. Maximum Tier I EDWCs for drinking water assessment based on ground 

application of rimsulfuron*

Full chemical name: N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridine sulfonamide

CAS No.: 122931-48-0

PC Code: 129009 

Use/Rate Modeled: Fruit trees applied once, by ground sprayers, at a rate of 0.0625 lbs. a.i./A

Chemical

Maximum Surface water EDWC (ppb) Maximum Ground water 

Acute Value Chronic/Cancer Value Acute/Chronic EDWC (ppb)

Rimsulfuron Parent 5.596 0.120 0.016

* Degradates are not included as recommended by HED Metabolism Committee. 

The above stated values for parent rimsulfuron represent upper-bound estimates of 

concentrations that might be found in surface water and groundwater due to the propose 

new use of the chemical on grapes, stone Fruit, tree nuts, pistachios, pome fruit, and 

citrus fruit using one application at the maximum yearly rate (worst case scenario). 

EFED emphasizes that this is a tier 1 screening-level analysis, and should there be a need, 

by HED, additional refinements can be made. It is noted that this assessment supersedes 

earlier assessment entitled “Preliminary Drinking Water Exposure Assessment” Dated 

02/25, 1998. In this referenced assessment older models and parameter guidance were 

used. 

Only one aerobic soil study was submitted and in order to be protective it was necessary 

to multiply this half-life by 3 before use in modeling. The geographic extent of use 

warrant the submission of new aerobic soil studies using soils representing new/current 

use areas. Uncertainties in representation of the default half-life may result in 

conservative EDWCs. 

 

1

 URL: http://www.alanwood.net/pesticides/

2

 URL: http://www.plantprotection.org/hrac/Bindex.cfm?doc=moa2002.htm
 10

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

II. PROBLEM FORMULATION

This is a Tier I drinking water assessment that uses modeling (no monitoring data is 

available) to estimate the surface and ground water concentrations of pesticides in 

drinking water source water (pre-treatment) resulting from pesticide use on sites that are 

highly vulnerable. This initial tier screens out chemicals with low potential risk and 

provides estimated exposure concentrations for human health dietary risk assessment. 

 

III. ANALYSIS

(1) Use Characterization 

Rimsulfuron herbicide formulation (DPX-E9636 FNV Dry Flowable) contains 25.0% of 

the active ingredient is proposed to be applied, by injection through sprinkler irrigation or 

by ground equipment only. For ground application, the herbicide is applied as a uniform 

broadcast to orchard or vineyard floor or as a uniform band at the base of the trunk or 

vine. The best results can be obtained from this systematic pre/early post emergence 

herbicide by applying to cool soils and by moisture activation within 2-3 weeks of 

application. Activation can be achieved by rainfall or overhead irrigation of a minimum 

of 1⁄2 to 1 inch. The herbicide is recommended for use on vigor and healthy trees that 

have been established for two full growing seasons. One single application of 4 ounces 

of product in 10 gallons of <4 or >8 pH buffered water/acre/year is recommended for 

either the broadcast or the band treatments. The chemical may be applied twice 

(maximum 4 ounces) on 50% or less band along the base of the trees with a minimum of 

30-day intervals. It is claimed to control susceptible weeds over a period of 60 to 90 days. 

The maximum label rates for the proposed new uses are presented in Table 2. 

Table 2. Rimsulfuron use patterns (Maximum rates/number and minimum intervals are 

included). 

Crop Spray Type Target 

Application: Maximum Rate/Number and Minimum Interval

Rate (lb a.i./Acre) Number Interval (days) 

Citrus/Pome/S

tone Fruits, 

Tree nuts, and 

Grapes 

Ground 

Broadcast 

injection 

through 

sprinkler Whole Soil Surface 0.0625 1 

Not applicable 

Ground 

Broadcast 

Banded 

A soil surface band 

through base of 

trees 

0.0625 1 

0.03125 * 2 30 

* Assuming that each application= half of the yearly application 

(2) Environmental Fate/Transport Characterization 

Table 1 (Attachment No. 2) contains a detailed summary of the physical/chemical and 

environmental fate/transport properties of rimsulfuron. Hereunder, is a summary of 
 11

various parameters that relates to its predicted behavior in various compartments of the 

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

environment and possible contamination of surface/ground water. 

(a) Environmental Persistence/Mobility

Rimsulfuron has a low vapor pressure (1.447 x10-11 atms. at 25 o

C) and is highly soluble 

in water (solubility 7.3 ppm at 20 oC3). Based on submitted environmental fate studies, 

the chemical is short lived in aqueous systems (mainly affected by hydrolysis with 

hydrolysis half-lives ranging from 5-7 days in acidic/neutral conditions and <1day in 

alkaline conditions). Also the chemical is short-lived in aerobic/anaerobic soil systems 

(t1/2= 19-21 days determined for only one soil, shorter half-lives were determined under 

field conditions: t1/2= 5 to 18 days). Rimsulfuron appears not to be affected by 

aqueous/on soil photolysis. 

Adsorption/desorption were studied using four soils with varied texture and organic 

matter contents (clay content= 4-30% and organic carbon content= 0.6-2.5%). The 

observed partitioning coefficient Koc ranged from 19-74 L Kg-1 suggesting that 

rimsulfuron may be highly mobile and vulnerable to run-off and leaching. Therefore, the 

chemical may reach surface and ground water resources. 

(b) Environmental Metabolites and their Persistence/Mobility

Rimsulfuron is expected to transform/degrade into a number of transformation/ 

degradation products under different environmental conditions (Figure 1, Attachment 

No. 3). The three major degradates for rimsulfuron result from contraction or cleavage or 

the sulfonurea-bridge (IN-70941 and IN-70942 from contraction while IN-J9260 from 

cleavage). In contrast, the minor degradates are cleavage degradates (IN-J9260 in 

systems other than aerobic soil, IN-J290 and IN-T5831). A summary of the degradation 

profiles in various laboratory systems is included in Table 3. 

Table 3. Transformation/degradation profiles of rimsulfuron in various systems. 

Degradate 

Name 

Max Degradate Concentration in % of applied and (Time in Days to Max Concentration; Does it Decline Y/N) 

Hydrolysis @ pH7 Aerobic Soil Anaerobic Soil Other Studies 

IN-70941 17% 

(3 days; Y to 1%) 

55% 

(10 days; Y to 30%) 

32% 

(10 days; Y to 6%) 

H2OPhotolysis: Similar to hydrolysis 

with reduction in transformation of IN70941 into IN-70942 and/or increase in 

the degradation of IN-70942. Plus 

enhanced formation of IN-J920 and 

IN-E9260 

Aerobic Aquatic Data: May not 

represent the natural environment as 

the system was exposed to light

TFD (Terrestrial Field Dissipation) 

Data: None Identified possibly due to 

IN-70942 84% 

(30 days; N) 

30% 

(360 days; N) 

56% 

(360 days; N) 

IN-E9290 10% 

(30 days; N) 

19% 

(30 days; Y to 16%) 

23% 

(360 days; N) 

IN-J290 7% 

(14 days; Y to 6%) 

3% 

(30 days; Y to 1%) 

8% 

(28 days; Y to 6%) 

 

3

 It was not clear if the reported solubility was 7.3 or 7,300 ppm; therefore the solubility of 7.3 ppm was 

assumed to be the correct solubility as values reported elsewhere were near the 7.3 value (for example, The 

solubility was reported to be 10 ppm in the EU database). 
 12

Degradate 

Name 

Max Degradate Concentration in % of applied and (Time in Days to Max Concentration; Does it Decline Y/N) 

Hydrolysis @ pH7 Aerobic Soil Anaerobic Soil Other Studies 

inappropriate LOD/LOQ (limits of 

detection/quantification)

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

Degradate 

Name 

Max Degradate Concentration in % of applied and (Time in Days to Max Concentration; Does it Decline Y/N) 

Hydrolysis @ pH7 Aerobic Soil Anaerobic Soil Other Studies 

IN-T5831 None 

Only Minor @ pH 5 

1% 

(270 days, Y to <1%) 

1% 

(360 days, N) 

Mobility of the transformation products/degradates were checked by TLC (thin layer 

chromatography) and results indicate high mobility to IN-E9260 and high to medium 

mobility for IN-70941, IN-70942 and IN-J290. Solubility was reported for only IN-70941 

and IN-70942 and was 0.7 ppm for the first and 0.2 ppm for the second. Considering 

quantities formed and relative persistent, the three rimsulfuron degradates are 

expected to reach both surface and ground water at varied concentrations. The timeline for this event is expected to be as follows: IN-79041 at the short to medium-term 

(because it transforms into IN-70942), IN-70942/IN-E9290/In-J290 at the medium to 

long-term. Finally, IN-70942 is expected to be the terminal and persistent degradate. 

(3) Drinking Water Exposure Modeling

(a) Models 

Surface and ground water EECs for drinking water (EDWCs) for rimsulfuron were 

obtained by modeling using tier 1 FIRST (version 1.0) and SCIGROW (version 2.3) 

simulated models, respectively. 

FIRST (FQPA Index Reservoir Screening Tool) is a meta-model of PRZM and EXAMS 

used as a screening tool to estimate pesticide concentrations found in surface water used 

as drinking water. FIRST was developed by making multiple runs of PRZM using 

varying sorption coefficients and determining the concentration in the EXAMS index 

reservoir scenario after a two-inch single storm event. (The Index Reservoir is a standard 

water body used by the Office of Pesticide Programs to assess drinking water exposure 

(Office of Pesticide Programs, 2002). It is based on a real reservoir (albeit not currently 

in active use as a drinking water supply), Shipman City Lake in Illinois, that is known to 

be vulnerable to pesticide contamination.) The single runoff event moves a maximum of 

8% of the applied pesticide into the reservoir (FIRST Users Manual; 08/01/2001). 

SCIGROW (Screening Concentration in Ground Water) is a regression model used as a 

screening tool to estimate pesticide concentrations found in ground water used as 

drinking water. SCIGROW was developed by fitting a linear model to groundwater 
 13

concentrations with the Relative Index of Leaching Potential (RILP) as the independent 

variable. Groundwater concentrations were taken from 90-day average high 

concentrations from Prospective Ground Water studies; the RILP is a function of aerobic 

soil metabolism and the soil-water partition coefficient. The output of SCIGROW 

represents the concentrations that might be expected in shallow unconfined aquifers 

under sandy soils, which is representative of the ground water most vulnerable to 

pesticide contamination likely to serve as a drinking water source ( SCIGROW: Users 

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

Manual (11/01/2001, revised 08/23/2002). 

If drinking water levels of concern are exceeded for Tier I surface water EDWCs, Tier II 

modeling will be able to refine these EDWCs by including volatility, Henry’s Law, 

diffusion in air, and enthalpy considerations. Since SCIGROW is a regression model 

developed from actual pesticide data with a range of volatilities, systematic conclusions 

cannot be drawn about over or underestimation of groundwater EDWCs at Tier I. 

(b) Modeling Approach and Input Parameters 

Input values used in FIRST modeling were based on the label and fate/transport 

parameters and are summarized in Table 4. 

Table 4. FIRST input parameters for modeling drinking water EDWCs. 

Input Parameter Value* Reference

Application Rate (lb a.i./Acre) 

0.0625 (One Application)

0.0313 (Two Application) Maximum label rate/Minimum application 

intervals (Product Label) 

Application Intervals (days) 30 

Percent Crop Area 0.87 Fruit trees 

Partition Coefficient “Koc” (L Kg-1) 19 Lowest non-sand value (MRID 413563-36) 

Aerobic Soil Metabolism Half-life 

(days) 64 

One half-life x 3 (21.3x3; MRID 413563-

34) 

Wetted In? Yes

Depth of Incorporation (inches) 0 Product Label 

Method of Application Ground** 

Solubility in Water (ppm) 7.3 

MRIDs: 419316-02 and 413563-01; Using 

water solubility of 7,300 ppm have not 

affected the results.

Aerobic Aquatic Metabolism Halflife (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 
 14

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

** The label permits application through the Sprinkler Irrigation Systems (reason for choosing ground 

application is stated in the text) 

Modeling was simulated for applying the pesticide once or twice as stated in the label. 

The results, for two applications, were lower compared to one application possibly due to 

degradation within the 30-day interval between applications (Table 5). For reference, 

sample runs are included in Attachment No. 4. 

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

Table 5. Modeled EDWCs of rimsulfuron in surface water. 

Application Procedure/Time Line Peak Day (Acute; ppb) Annual Average (Chronic; ppb) 

Once (applied only one time) 5.596 0.120 

Twice (divided in half with 30-day interval) 4.786 0.103 

Although higher drift might be associated with sprinkler irrigation, ground application 

was chosen for the simulation as the EDWCs were more conservative. This was 

confirmed by running the model with drift value of up to 16% (aerial application) which 

gave lower EDWCs (i.e. less conservative values). The reason for such results is 

associated with the how concentrations are calculated by the model combined by the fact 

that this chemical has low affinity to soil particles resulting in higher importance of runoff than drift. As shown in Table 6, the model calculates lower amounts of the pesticide 

pool available for run-off in aerial compared to ground spray (amount of 2.114 lbs 

compared to 2.028 lbs). Although, the model calculates higher amount of drift for aerial 

compared to ground (0.130 lbs for aerial compared to 0.052 lbs for ground), these 

amounts are only 3-6% of the pesticide run-off pool. 

 

Table 6. Rimsulfuron: Amount of run-off and drift pools as calculated by FIRST. 

Pesticide Pools Ground spray Aerial spray. Bases for the calculation 

Run-off 2.114 lbs 

(427 x 0.0625*x 0.08 

x 0.99) 

2.028 lbs 

(427 x 0.0625*x 0.08 

x 0.95) 

8% of the total mass of pesticide applied 

to 427 acres watershed with application 

efficiency of 99% for ground and 95% 

for aerial. 

Drift 0.052 lbs 

(13 x 0.0625* 

x 0.064) 

0.130 lbs 

(13 x 0.0625* 

x 0.16) 

Fraction of the rate of the amount 

applied to 13 acres water body with drift 

values of 6.4% for ground and 16% for 

aerial. 

* The value of 0.0625 = application rate which is equal to 0.0625 lb a.i./Acre. 

Input values used in SCI-GROW modeling were based on the label and fate/transport 

parameters summarized in Table7.

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

(EDWCs). 

Input Parameter Value Reference
 15

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) 21.3 One half-life (MRID 413563-34) 

A summary of the results is included in Table 8. For reference, a sample run is included 

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

in Attachment No. 4. 

Table 8. Summary of outputs from SCI-GROW for rimsulfuron. 

Application Procedure/Time Line Acute and Chronic Values (ppb) 

Once (applied only one time) 0.0158 

Twice (divided in half with 30-day interval) 0.0158 

IV. MONITORING DATA

Although this pesticide is currently registered for use, no monitoring data was found or 

submitted. 

V. DRINKING WATER TREATMENT

No data were submitted for drinking water treatment effects. However, water treatment 

may include water softening which generally increase the pH. This pesticide is expected 

to hydrolyze at much faster rates in alkaline systems (half-life of 4-11 hours at pH 9 

compared to 5-7 days at pHs 5 and 7). Therefore, enhanced degradation is expected as 

result of water treatment raising the potential for lower EDWCs in treated water 

compared to the modeled raw water. 

VI. CONCLUSIONS

For surface water, only one aerobic soil half-life was available, EDWCs were calculated 

based on a default half-life value that is three times longer. Therefore, EDWCs could 

therefore be conservative. The registrant may submit additional aerobic soil studies to 

represent the range of texture and organic matter for soils in the expanded use areas. 

For ground water: only one aerobic soil half-life was available and used. Resultant 

EDWCs could therefore be underestimated because of the use of single aerobic soil halflife. 
 16

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ATTACHMENT No. 1: 
 17

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 18

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)
 19

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

ATTACHMENT No. 2: 

Table 1. The physical/chemical and environmental fate/transport properties of 

rimsulfuron: a detailed summary.

Parameter Value Source

I. Physical/chemical properties 

Classification Pyrimidinyl Sulfonylurea 

Registrant 

Data and the 

Web 1 

Molecular Formula C14H17N5O7S2

PC Code 129009 

Chemical Name (IUPAC) 

1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-

pyridylsulfonyl)urea 

Chemical Name (CAS) 

N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-

pyridine sulfonamide 

CAS Number 122931-48-0 

MRIDs: 

419316-02 

413563-01 

Molecular Weight 431.44 

pKa 4 

H20 Solubility (ppm) 7.3 @ pH 7/25 oC2

Vapor pressure (25oC) 1.1x10-8 torr Equal to 1.447x10-11 atms. 

Henry's Law Constant 1.40x10-12 atms. m 3 . mole -1 (Calculated) 

Octanol/Water Partition, Kow 1 @ pH7 and 87 @ pH 5 (log KOW 0.034 @ pH7 &1.94 @ pH 5) 

II. environmental fate/transport properties 

Hydrolysis 

t1⁄2= 4.5- 4.7days @ 25 o

C, pH 5; 7.1- 7.3days @ 25 oC, pH 7; 4.2- 

10.9Hours @ 25 o

C, pH 9. 

MRID: 

413563-33 

Photolysis in water 

at pH 7 

Half-lives in irradiated samples (11.0-12.4 days) were longer than 

the dark controls (6.4-6.5 days) indicating that Direct photolysis is 

NOT an important degradation pathway. 

MRID: 

419316-08 

Photolysis on soil 

Half-lives in irradiated/dark control samples were in the range of 11-

12 days indicating that photolysis on soil is NOT an important 

degradation pathway. 

MRID: 

419316-09 

Aerobic soil metabolism t1⁄2 = 21.3 days for two labels (R2= 0.87-0.94) 

MRID: 

413563-34 

Anaerobic soil metabolism t1⁄2 = 17.9-18.1 days for two labels (R2= 0.91-0.99) 

MRID: 

413563-35 

Aerobic aquatic metabolism 

t1⁄2 =0.5-2 Days at 25 o

C in the water column; t1⁄2 = 59-77 Days at 5 oC in 

the water column. 

Important Note: Calculated half-lives may NOT represent an aerobic 

aquatic system because of exposure to light and use of diluted sediment. 

MRID: 

432885-02 

Adsorption/Desorption 

(Kd and Koc in L Kg-1) 

Kd = 0.23; 1.36; 0.32 and 1.52 corresponding to: 

Koc= 19; 55; Koc= 55; and 61

MRIDs: 

413563-36 

413563-37 

Terrestrial Field/Lysimeter 

Dissipation 3 t1⁄2 (average in the top 0-3” of four soils): 5-18 Days

MRIDs: 

419316-06 

419316-10 1 URL: http://www.scorecard.org/chemical-profiles/text-search.tcl?query_string=Rimsulfuron 2 Solubility was reported to be 10 ppm, elsewhere; URL:http://www.eu-footprint.org/ppdb.html

3

 The terrestrial field dissipation study for a soil in Newark, Delaware submitted under MRID 419316-10 

was classified as unacceptable study. 
 20

N

S O

O

CH2

H3C

S

O

O

H2N

Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

ATTACHMENT No. 3: 

Figure 1: Expected degradation scheme for rimsulfuron in the important compartments 

of the environment. 

N

N

O

O

H3C

H3C

N

H N

S O

O

CH2

H3C

N

H

S

O

O

O

Parent Rimsulfuron 

N

S O

O

CH2

H3C

N

N

O

O

H3C

H3C

N

CO

NH2 IN-70941 

N

S O

O

CH2

H3C

N

N

O

O

H3C

H3C

NH

IN-70942 

N

N

O

O

H3C

H3C

NH2

IN-J290: Pyrimidine Amine IN-E9260: Pyridine Sulfonamide 

IN-T5831: Pyrimidinyl Urea 

N

N

O

O

H3C

H3C

NH

CO

NH2

Sulfonurea-Brigde Cleavage (MINOR 

in all systems, Except as indicated)

MAJOR in 

Aerobic 

Soil Only 

Sulfonurea-Brigde Contraction (MAJOR 

in all systems) 

Sulfonylurea Bridge 

Pyrimidine Ring Pyridine Ring 
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ATTACHMENT No. 4: Example Model Runs

A. Surface Water:

RUN No. 1 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 0 7.20 .00- .00 .00 7.20 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 5.596 .120 

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

 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) 

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

 .031( .054) 2 30 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 0 7.20 .00- .00 .00 7.20 

 UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 DEC 12, 2005 

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

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

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

 4.786 .103 

 -------------------------------------------------------------------- 
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Electronic Copy of Previous Drinking Waters Analysis (2/6/07; cont.)

B. Ground Water:

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 1/12/2007 9:20:20 

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

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 21.3 

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

Groundwater screening concentration (ppb) = 1.58E-02 

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