UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

CHEMICAL SAFETY AND POLLUTION PREVENTION 

PC Code: 129009 

DP Barcode: D414506 

MEMORANDUM 

DATE: 

SUBJECT: 

FROM: 

TO: 

Through: 

March 12,2014 

Tier I Drinking Water Assessment for the proposed Section 3 ALS inhibition 

tolerant sorghum crops new use for the chemical Rimsulfuron (P.C. Code: 129009, 

DP Barcode 414506) /() • 

1 

__ 

Michael Barrett, Senior Chern· (In n~;yi 'f 

Environmental Risk Branch V ~ -j ~ e 

Environmental Fate and Effects Division (7507P) 

Kable Davis, Risk Manager (RM-25) 

Daniel Kenny, Risk Manager Reviewer 

Herbicide Branch 

Registration Division (7505P) 

Meheret N egussie, Risk Assessor 

Christine Olinger, Chief 

Registration Action Branch 3 

Health Effects Division (7509P) ' J //3// J 

Environmental 

Environmental 

Mah Shamim, Ph.D, 

Risk 

Fate and 

Branch 

Chief 

Effects 

V 

Division 

~ 

(7507 P) 

Enclosed is the Tier I drinking water assessment for the proposed Section 3 new uses of 

rimsulfuron for sorghum crops tolerant to the inhibition of the acetolactate synthase (ALS) 

enzyme. 

1 
2

Executive Summary

The impact of rimsulfuron (1-(4, 6-Dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-

pyridylsulfonyl)urea) residues of concern (also referred to as the “total toxic residues”) was 

addressed in order to evaluate the impact of a proposed new use on ALS inhibition tolerant 

sorghum. This assessment replaces previous drinking water assessments since two environmental 

degradation products have been added to the residues of concern for human exposure.

Rimsulfuron belongs to the sulfonyl urea class of herbicides, which acts by inhibiting the plant 

enzyme acetolactate synthetase (ALS). The inhibition of this enzyme blocks the production of 

amino acids, valine and isoleucine, which are important in the production of plant proteins and 

other components. This leads to the disruption of cell division and elongation in the plant. It is 

intended to control a variety of annual and perennial grass and annual broadleaf weeds in both 

agricultural and non-agricultural settings such as barnyardgrass, crabgrass, foxtail, panicum, 

volunteer wheat, Johnson grass and shattercane. The application of rimsulfuron to ALS inhibition 

tolerant crops will enable for rimsulfuron to treat these crops without damage while killing other

target weeds. The new use for ALS inhibition tolerant sorghum crops is proposed for DuPontTM 

Resolve® and DuPontTM Steadfast® (see Table 2 in the Use Characterization section).

This Tier I Drinking Water Assessment for the proposed new use of rimsulfuron on ALS inhibition 

tolerant sorghum crops provides estimates of the upper bound residue concentration of 

rimsulfuron total toxic residues (parent and the IN-70941 and IN-70942 degradates in surface and 

ground water drinking water sources resulting from its proposed uses. The tier 2 model 

PRZM/EXAMS (PRZM version 3.12.2, May 2005 and EXAMS version 2.98.4.6, April 2005) is

used to evaluate surface water exposure. The Tier 1 model PRZM-GW (version 1.0, December 

2012) is used to evaluate ground water exposure. Rimsulfuron existing water monitoring data is 

also cited, however there are no data for the rimsulfuron degradates of concern to verify modeled 

exposures for drinking water.

Rimsulfuron foliar applications using ground and aerial sprays impact both surface and ground 

water drinking water sources given that it possesses similar physical chemical properties and 

persistence to other chemicals which are known to translocate to these media. Rimsulfuron

degrades mainly in sequence to degradates IN-70941 and IN-70942 – both of these molecules

maintain a contracted form of the sulfonylurea bridge. IN-70942 only slowly degrades over a 

period of months or years under most environmental conditions. Since IN-70941 and IN-70942

are expected to possess similar environmental fate and toxicity to parent rimsulfuron for the 

purposes of human health risk assessment, these degradates are included in the drinking water 

assessment. 

In this updated drinking water exposure assessment it has been determined that exposure from the 

current and proposed uses should not exceed 22.2 μg/L (ppb) for acute exposure and 19.7 μg/L

(ppb) for chronic and cancer exposure. These values reflect a predicted higher potential exposure 

level from groundwater sourced drinking water supplies than surface water supplies. The Table 1
3

values are based on uses from several crop sites with higher single and seasonal maximum 

application rates than is proposed for the new use on ALS inhibition tolerant sorghum. 

Table 1. Maximum Tier I Rimsulfuron ROC EDWCs for drinking water based on 

application of rimsulfuron to crops with highest rates and exposure potential.

Crops / Uses 

Represented

Highest Daily Value

(Acute)

Post-Breakthrough 

Average 

(Chronic and Cancer)

All 22.2 19.7

Based upon the highest values from six standard Tier 1 groundwater scenarios (i.e., 

a WI scenario based upon a predominantly corn production area, see also Table 12

for more detailed results. The EDWCs are representative for crop use sites with 

higher allowed application rates than for the proposed use on ALS inhibition 

tolerant sorghum.

The estimated drinking water concentrations (EDWCs) in this assessment are additionally higher 

than in previous assessments because of the addition of two degradation products to the total toxic 

residues (TTR) – also known as the residues of concern1. The TTR includes parent rimsulfuron, 

plus the IN-70941, and IN-70942 degradates. The EDWCs for groundwater and surface water 

sourced drinking water specific to the proposed new use are discussed later in this document but 

only the values in Table 1 should be used for a conservative estimate of the drinking water 

contribution to dietary exposure estimates.

Use Characterization

Rimsulfuron is applied pre-emergent or post-emergent for weed control in various crop / non-crop 

uses via ground (broadcast and banded applications) and aerial applications. Rimsulfuron 

formulated products are available as an emulsifiable concentrate (field corn use only), water 

dispersible granules (dry flowable), or soluble concentrates (solid). Maximum single application 

rates for the various crop and non-crop use sites range between 0.0078 and 0.0625 lbs. a.i./A. In 

many cases the labels are not specific with regards to the maximum number of applications or 

application intervals per year for a particular use site.

Rimsulfuron herbicide is used for control of many broadleaf and grass weed species (primarily 

pre- and early post-emergent) on numerous crop and non-agricultural use sites

 

1 Both terms (TTR and ROC) in this document are used to represent the residues assessed to determine drinking water 

exposure.
4

The proposed use is for two formulations of rimsulfuron water soluble granular applied via 

conventional ground or aerial foliar applications on ALS inhibition tolerant sorghum crops. This 

new use is proposed for DuPontTM Resolve® (25 percent rimsulfuron) and DuPontTM Steadfast® 

(15 percent rimsulfuron) products. Proposed maximum application rates range between 0.012 lbs. 

a.i./A – 0.031 lbs. a.i./A with seasonal maximum application rates ranging between 0.016 – 0.031

lbs. a.i./A with a minimum of 7 seven days between applications specified on the draft product 

label. Table 1 shows the complete proposed use information for rimsulfuron on ALS inhibition 

tolerant sorghum crops. 

Table 2. Summary of application information based on labels provided by DuPontTM for 

rimsulfuron related to the proposed Section 3 new use for ALS inhibition tolerant sorghum crops.

PRODUCT % A.I. FORMULATION

APPLICATION

METHOD

SINGLE APP. 

RATE 

(lbs. a.i./A)

MAX. 

SEASONAL 

APP. RATE 

(lbs. a.i./A)

MIN. 

RETREATMENT 

INTERVAL

(days)

DuPontTM 

Resolve®

(352-768)

25 SG G,A

0.0156 

-0.0313 0.0313

7

DuPontTM 

Steadfast®

(352-816)

15 SG G,A 0.0117 

-0.0157 0.0157. 7

1. Formulation identifier: SG = Water soluble granule

2. Application method identifiers: G = foliar ground application; A = foliar aerial application

Sorghum crop production is highly concentrated over an area of the country confined to mainly the 

Southern Great Plains region including Central and West Texas, the Panhandle of and Central 

Oklahoma, Central and Western Kansas, South Central Nebraska, and South Central South 

Dakota. Figure 1 below shows a map of the density of sorghum crops planted nationwide by 

county from the United States Department of Agriculture’s National Agricultural Statistics 

Service (USDA NASS).
5

Figure 1. . Recent distribution of sorghum crops planted nationwide (ca. 2012).

Map Citation: United States Department of Agriculture National Agricultural Statistics Service 

http://www.nass.usda.gov/Charts_and_Maps/Crops_County/pdf/AS-PL12-RGBChor.pdf

Environmental Fate and Transport Characterization

Properties of Parent and Degradates of Concern

Physical and chemical properties of rimsulfuron are shown in Table 3 below. Environmental fate 

and transport properties of rimsulfuron based upon registrant submitted studies or other references 

are shown in Table 4 below.

Table 3. Nomenclature and physicochemical properties of rimsulfuron.

Parameter Value Reference

Chemical Classification Pyrimidinyl Sulfonylurea Registrant 

Data and 

PPDB

Molecular Formula 1C14H17N5O7S2

PC Code 129009

Chemical Name (IUPAC)

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

onyl)urea
6

Parameter Value Reference

Chemical Name (CAS)

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

nyl)-2-pyridine sulfonamide

CAS Number 122931-48-0

Pesticide Classification Herbicide

MRIDs

413563-01

Molecular Weight 431.44

Physical State Solid

pKa 4

Water 

Solubility 

(ppm)

Parent 7,300 @ pH 7/25 oC; 135 ppm @ pH 5; 5,560 ppm @ pH 9

IN-70941 0.7 @ pH 7/25 oC

IN-70942 0.2 @ pH 7/25 oC

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

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

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

1 PPDB = Pesticide Properties Database or Footprint database. URL: 

http://sitem.herts.ac.uk/aeru/iupac/Reports/586.htm

Table 4. A summary of the environmental fate data for rimsulfuron.

Parameter Value MRID

Hydrolysis

t1⁄2= 4.5- 4.7days @ 25 oC, pH 5;

t1⁄2= 7.1- 7.3days @ 25 oC, pH 7;

t1⁄2= 4.2- 10.9Hours @ 25 oC, pH 9.

Major degradates (from contraction of the sulfonylurea bridge): 

IN-70941 and IN-70942, IN-70942 appears to be stable at pH 7.

Minor degradates (from cleavage of the sulfonylurea bridge): IN-E9260 

and IN-J290 and IN-T5831 (only @ pH 5).

413563-33, 

Acceptable

Direct 

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) suggesting that Direct photolysis is NOT an 

important degradation pathway.

Major and Minor degradates: Similar to hydrolysis although irradiation was 

associated with reduced conversion of the transformation product IN-70941 

into IN-70942 and/or enhanced degradation of IN-70942. Formation of 

IN-E9260, IN-J290, and the un-identified polar compounds appeared to be 

enhanced.

No evidence of photolysis of IN-70942 (the terminal toxic residue for human 

health risk assessment).

419316-08, 

Acceptable
7

Parameter Value MRID

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.

Major and Minor degradates: Similar to hydrolysis although irradiation 

appeared to increase the formation of soluble un-identified polar compounds.

419316-09, 

Acceptable

Aerobic soil 

metabolism

t1⁄2 = 21.3 days for two labels (R2= 0.87-0.94; separate tests done with 

pyrimidine and pyridine labeled parent) in Sassafras sandy loam soil from 

Penns Grove, NJ (Sand= 77%, Silt= 14%, Clay 9%, pH 6.7, Organic matter= 

1.1%, CEC= 3.2 meq/100 g).

TTR (rimsulfuron + IN-70941 + IN-70942) t1⁄2 = 484.8 days at 25 C.

t1⁄2 = 21.5 days for two labels (R2= 0.95) in Traver sandy loam soil from 

Madera, CA (Sand= 53%, Silt= 28%, Clay 19%, pH 7.4 – 7.5, Organic matter= 

1.7%, CEC= 19.1 meq/100 g).

TTR t1⁄2 = 1960.8 days at 20 C, 1386.4 days at 25 C.

t1⁄2 = 48.1 days for two labels (R2= 0.82) in Arkansaw sandy loam soil from 

Arkansaw, WI (Sand= 76%, Silt= 16%, Clay 8%, pH 6.8 – 7.3, Organic 

matter= 3.7 %, CEC= 13.7 meq/100 g).

TTR t1⁄2 = 214.5 days at 20 C, 151.7 days at 25 C

Major degradates (from contraction of the sulfonylurea bridge): 

IN-70941 further degrading into IN-70942) plus IN-E9260 (from cleavage of 

the sulfonylurea bridge; only quantified in one of the three test soils)

Minor degradates (from cleavage of the sulfonylurea bridge): IN-J290 and 

IN-T5831.

41356334: 

Acceptable

48332003: 

In review

Anaerobic 

aquatic 

metabolism

t1⁄2 = 4.2 days for combined labels (R2= 0.98; note separate results for 

pyrimidine and pyridine labeled product are available from this study) in Farm 

pond in Mississauga, Ontario, Canada (sediment classified as a loam with 

Sand=44%, Silt= 30%, Clay 26%, pH 7.6, Organic matter= 5.4%, CEC= 29.2 

meq/100 g), at 25 C.

TTR (rimsulfuron + IN-70941 + IN-70942) t1⁄2 = 58.3 days at 25 C

Major degradates were identified:

IN-70941 (most persistent, up to 43-45% of applied at 7 to 14 days after 

treatment) and the subsequently formed IN-70942 which was up to 10-12% at

30 DAT but declined rapidly thereafter.

48332004, In 

Review

Anaerobic soil 

metabolism

t1⁄2 = 17.9-18.1 days range for two labels (R2= 0.91-0.99) in Sassafras sandy 

loam soil from Penns Grove, NJ (same soil used in the aerobic soil study).

Major/Minor degradates: Same as the aerobic soil.

41356335, 

Acceptable
8

Parameter Value MRID

Aerobic aquatic 

metabolism t1⁄2 =0.5-2 Days at 25 oC in the water column;

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

(No indication of sediment included in study.)

At 25 C IN-70942 was 65% of applied rimsulfuron and constituted essentially 

all of the remaining residues.

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

aquatic system because of exposure to light and the use of extremely diluted 

sediment; but note that photolysis has not been found to be a major dissipation 

pathway Also, a newer study is currently under review. 

Major/Minor degradates: Similar to hydrolysis.

Rimsulfuron appears to be slightly more persistent with half-lives of a few 

days in two test systems (study still in review.)

Preliminary results for TTR degradation:

Blackiston, DE loam system t1⁄2 = 273.4 days

Hampshire, UK sand system t1⁄2 = 39.1 days

43288502, 

Supplemental

(45490802:in 

review)

Adsorption/

Desorption 

(Kd and 

Koc in L Kg-1)

[Pyrimidine-2-

14C]:

Cecil sandy loam (NC): Kd = 0.23 and Koc= 19

Fargo clay loam (ND): Kd = 1.36 and Koc= 55

Sassafras sandy loam (NJ): Kd = 0.32 and Koc= 55

Flanagan silt loam (IL): Kd = 1.52 and Koc= 61

(Limited data also available on some degradates; please refer to Table 6

the “Environmental Fate” section of this Problem Formulation 

document.)

See Table xxx for details on degradate sorption coefficients. 

41356336, 

Acceptable

Terrestrial 

Field/Lysimeter

Dissipation 1

Greenville, MS: t1⁄2 = 09 Days (average in the top 0-3”)

Madera, CA: t1⁄2 = 08 Days (average in the top 0-3”)

Rochelle, IL: t1⁄2 = 18 Days (average in the top 0-3”)

Newark, DE: t1⁄2 = 05 Days (average in the top 0-3”)

Major degradates: IN-70941 (degrading into IN-70942)

Minor degradates: None identified as the bridge-cleavage degradates may 

have fallen below the LOD (LOD≤10% of the applied) 

419316-06,

419316-10, 

Acceptable

Bioconcentration in Fish: Waived following request (MRID 413563-39) due to low Kow=1 at pH7.

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

upgraded to acceptable.

Environmental Fate Summary

In the natural environment, the major routes of dissipation of rimsulfuron are expected to be 

hydrolysis and / or bio-transformation. Additionally, adsorption/desorption studies suggest that 

rimsulfuron may be highly mobile and vulnerable to run-off and leaching (Koc ranged from 19-74 
9

L Kg-1). Therefore, the chemical may enter aquatic systems via run-off and erosion. Although 

there is a potential for rimsulfuron parent to reach groundwater when conditions promote its 

stability and relatively rapid subsurface transport, it is also true that its persistence is relatively low 

compared to most pesticides which have been commonly detected in groundwater. The soil 

mobility / leachability of the primary degradates IN-70941 and IN-70942 is somewhat less than for 

parent rimsulfuron (Table 6) but these compounds are more environmentally persistent than 

parent rimsulfuron. Significant leaching was not confirmed in the field dissipation studies but it is 

uncertain whether residues that may have leached could be confirmed given the sampling methods 

and detection limits of the analytical methods.

Rimsulfuron is expected to transform/degrade into a number of products under different 

environmental conditions. The two consistently major degradates for rimsulfuron result from 

contraction of the sulfonylurea-bridge (IN-70941 and IN-70942). A third major degradate (in one 

aerobic soil metabolism study only) results from cleavage of the sulfonylurea bridge (IN-E9260) 

(an aminopyrimidine degradate, IN-J290, is formed from the remainder of the cleaved molecule 

and, while reported as a major degradate for some other sulfonylurea herbicides, is not major for 

rimsulfuron). Full chemical names are provided in Table 5 (IN-J290 is not included because it is 

not part of the residues of concern. The minor degradates are cleavage degradates (IN-J9260 in 

systems other than aerobic soil, IN-J290 and IN-T5831). Note that In-J290 is an aminopyrimdine 

compound that is also a degradation product of several other registered sulfonylurea herbicides. 

Mobility of the transformation products/degradates were evaluated by thin layer chromatography

(TLC) and results indicate high mobility to IN-E9260 and high to medium mobility for IN-70941, 

IN-70942 (this persistent degradate had highly variable estimated mobility between the test soils)

and IN-J290 (Table 6). 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. These solubilities are four orders of magnitude smaller 

than for the parent compound. Considering quantities formed and relative persistence of 

transformation products/degradates, all are expected to reach aquatic systems in varied 

concentrations. In addition, most of the parent that reaches aquatic systems by drift is expected to 

transform under aerobic conditions by hydrolysis into (the usually) transient IN-70941 then into 

the usually persistent IN-70942 (only in the single biologically active anaerobic aquatic test 

system did IN-70942 degrade substantially). 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. IN-70942 is expected to be the terminal 

and persistent degradate under aerobic conditions but transforms further into multiple unidentified 

minor polar products under anaerobic conditions (≤10% AR). 

Table 5. Rimsulfuron transformation products/degradate code/chemical names.

Applicant's 

Code IUPAC Chemical Name

IN-70941 N-(4, 6-Dimethoxy-2-pyrimidinyl)-N-((3-ethylsulfonyl)-2-pyridinyl))Urea

IN-70942 N-((3-Ethylsulfonyl)-2-pyridinyl)-4, 6-dimethoxy-2-pyrimidineamine)

IN-E9260 3-(Ethylsulfonyl)-2-pyridine sulfonamide

IN-J290 2-Amino-4, 6-dimethoxy pyrimidine

IN-T5831 N-(4, 6-Dimethoxy-2pyrimidinyl) Urea
10

Table 6. Mobility of parent rimsulfuron and its transformation products/degradates (Koc

values).

Environmental Transformation Products of Rimsulfuron and the

Residues of Concern

Details of rimsulfuron degradation in the environment are discussed in the Rimsulfuron 

Registration Review Problem Formulation (EFED, 9/13/2012; DP Barcode D401380).

For the purposes of this exposure assessment the relevant environmental degradation pathway is:

Parent Rimsulfuron > IN-70941 > IN-70942

This pathway was observed in hydrolysis, aerobic soil metabolism, aerobic and anaerobic aquatic 

metabolism, and field dissipation studies. In most cases it is the initial and primary for transformation of 

rimsulfuron. Chemical nomenclature and identity information are provided in Table 3. 

Rimsulfuron Degradates of concern:

Ad/Des Method 1 TLC Method 2

Parent Parent IN-70941 IN-70942 IN-E9260 IN-J290

Cecil sandy loam 19 51 58 41 44 284

Fargo clay loam 55 63 357 317 6 ND 3

Sassafras sandy loam 55 41 79 207 110 ND

Flanagan silt loam 61 74 142 1,398* 6 834

Woodstown sandy loam ND ND ND ND ND 393

Keyport silt loam ND ND ND ND ND 362

Mobility Class 4 Very high-High High- Medium (except *=Low) Medium

1 K d calculated from a 4-hour/4 concentrations adsorption/desorption experiments; results from MRID 41356336.

2 K d calculated from R f values using Hamaker equation; 3 ND= No Data; results from MRID 41356337.

4 Mobility class as per: McCall, et al. 1980. Estimation of chemical mobility in soil from liquid chromatographic 

retention times. Bull. Environmental Contamination. Toxicology. 24, 190-195.
11

Table 7. Structures and names of rimsulfuron and degradates of concern for drinking water 

exposure.

Rimsulfuron [DPX-E9636]

IUPAC Name: 1-(4,6-Dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea.

CAS Name: N-[[(4,6-Dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-(ethylsulfonyl)-2-pyridines

ulfonamide.

CAS Number: 122931-48-0

SMILES String: CCS(=O)(=O)c1cccnc1S(=O)(=O)NC(=O)Nc2nc(OC)cc(OC)n2 (EpiSuite 4.0).

Empirical formula: C14H17N5O7S2 Molecular formula: C14H17N5O7S2

Molecular weight: 431.44

IN-70941

IUPAC Name: 1-(4,6-Dimethoxypyrimidin-2-yl)-1-(3-ethylsulfonyl-2-pyridyl)urea (IUPAC 

Name).

CAS Name: N-(4,6-Dimethoxy-2-pyrimidinyl)-N-((3-(ethylsulfonyl)-2-pyridinyl))urea.

CAS Number: 138724-53-5

SMILES String: COC1=NC(=NC(=C1)OC)N(C(=O)N)C2=NC=CC=C2S(=O)(=O)CC

Molecular wt: 367.39
12

IN-70942

IUPAC Name: N-(3-Ethylsulfonyl-2-pyridyl)-4,6-dimethoxy-pyrimidin-2-amine .

CAS Name: N-((3-(Ethylsulfonyl)-2-pyridinyl)-4,6-dimethoxy-2-pyrimidineamine.

CAS Number: 151331-80-5

SMILES String: C1=C(N=C(N=C1OC)NC2=NC=CC=C2S(=O)(=O)CC)OC

Molecular wt: 324.36

SMILES Strings were retrieved from the CAS numbers at:

http://cactus.nci.nih.gov/chemical/structure
13

Derivation of Degradate Properties for Drinking Water Exposure 

Prediction

There are limited physical-chemical or environmental fate data which have been submitted by 

registrants or available from the open literature for the degradates discussed above including for 

IN-70941 and IN-70942. Physical chemical property values for these metabolites were estimated 

from EPISuite2.

. Table 5 shows the predicted and measured (where available) properties of the 

IN-70941 and IN-70942 degradates compared to those of parent rimsulfuron (from studies

submitted to the Agency). Since IN-70942 is the terminal and most persistent degradate in the 

residues of concern its properties are especially relevant to a total toxic residue analysis for the

rimsulfuron drinking water exposure assessment. While all three moieties are weakly to 

moderately sorbed to soil and sediment materials IN-70942 is measurably more strongly 

partitioned onto organic material or clay minerals with Koc or Kfoc values generally between 200 

and 300 ml/g. 

Table 8. Comparison of physical chemical properties of rimsulfuron degradation products to 

parent rimsulfuron.

Property/

EPISuite 

Estimator 

Program 

Value from 

Existing 

Database EPISuite Value and/or measured value

Rimsulfuron Rimsulfuron IN-709411

IN-709421

Other

IN-709421

measured

Molecular Weight 431.4 --- 367.38 324.36 ---

Solubility in Water 

(25 °C, mg/L)

(WSKOW v. 1.41)

7300 @ pH 7

135 @ pH 5

270 28.59 133.6 ---

Vapor Pressure 

(25 °C, mm Hg)

(MPBPVP v. 1.43)

1.1x10-91.13x10-87.69x10-

12 4.23x10-9

---

Henry’s Law 

Constant (25 °C, 

atm·m3/mol)

(HENRYWIN v. 

3.20)

1.40x10-12 2.33 E-16 2.33E-13 2.36x10-9---

Octanol-Water 

Partition Coeff. 

(Log Kow)

(WSKOW v. 1.41)

0.034 @pH7

1.94 @pH5

0.029 @ pH 7 2.61 2.31 ---

Soil-Water Partition 

Coeff. (Koc, ml/g)

(KOCWIN v. 2.00)

47 (median)

55 (mean)

--- 13.9 (MCI 

estim.)

1061 (Kow 

28.2 (MCI estim.)

589.6 (Kow 

estim.)

Kfoc 145 – 223; 

median 204 in 4 

soils

 

2

 EPISuite (Estimation Programs Interface Suite) version 4.0 was used. EPISuite is a software developed by the EPA 

Office of Chemical Safety and Pollution Prevention in collaboration with the Syracuse Research Corporation (SRC). 

EPISuite is a collection of programs which estimate physical chemical and environmental fate properties for mainly 

organic compounds. 
14

Table 8. Comparison of physical chemical properties of rimsulfuron degradation products to 

parent rimsulfuron.

Property/

EPISuite 

Estimator 

Program 

Value from 

Existing 

Database EPISuite Value and/or measured value

Rimsulfuron Rimsulfuron IN-709411

IN-709421

Other

IN-709421

measured

estim.)

110 (TLC 

meas.)

262 (TLC meas.) Germany DAR 

(7/2/03)

1

 Degradates incorporated in the Drinking water residues of concern.

Rimsulfuron and IN-70942 physical chemical property values generally agreed well with estimates from EPISuite.

Other literature cited: Rapporteur Member State Germany. 2005. Draft Assessment Report (DAR): Rimsulfuron; 

second stage of the review programme referred to in Article 8(20 of Council Directive 91/414/EEC.
15

Problem Formulation

The environmental fate properties of the rimsulfuron total toxic residues / residues of concern

indicate that drinking water exposure potentially may occur in surface water supplies or in 

drinking water wells. Direct deposition of rimsulfuron from aerial applications and subsequent 

washoff from crop foliage, runoff, leaching, and spray drift deposition are potential transport 

mechanisms to surface and ground water. The potential for rimsulfuron TTR exposure in surface 

and ground drinking waters also exists based on the high persistence of the rimsulfuron TTR and 

high mobility in the environment. Therefore, this drinking water assessment will address 

scenarios which depict the potential for rimsulfuron to be transported off-site to drinking water 

sources. 

As per meeting with the Health Effects Division’s Risk Assessment Branch 3 (meeting dated 

December 17, 2013) the residues of concern for drinking water include parent rimsulfuron and all 

major degradates which maintain the original or a contracted form of the sulfonylurea bridge

between the pyridine and pyrimidinyl moieties of rimsulfuron (the other identified degradation 

products not included in this assessment arise form the cleavage of this bridge and therefore only 

consist of a either a pyrimidine or pyridine derivative). These include degradates identified as 

IN-70941 and IN-70942. Table 4 in the previous section indicated that these degradates were 

detected at significant levels (greater than 10 percent of applied) in soil, sediment, and water. 

These degradates possess similar physical chemical properties and are being considered to be of 

equal toxicity for the purposes of a human dietary exposure assessment for rimsulfuron. Therefore, 

the total residue method will be used to estimate exposure in drinking water sources. In estimated 

drinking water concentrations (EDWCs) using the total residue method, degradate residues from 

environmental fate laboratory studies were added to the parent rimsulfuron to calculate the total 

residue half-life. This approach assumes that degradates possess equivalent toxicity and fate 

properties to the parent active ingredient. An overview of the total residue method is provided in 

the white paper on the FIFRA SAP Meeting on, “Selected Issues Associated with the Risk 

Assessment Process for Pesticides with Persistent, Bioaccumulative, and Toxic Characteristics” 

held in October 2008 (EPA, 2008).

Exposure Analysis

Methods for Estimation of Drinking Water Concentrations

In this Tier I analysis, 1-in-10 year peak concentrations are representative of acute levels of 

exposure, the 1-in-10 year annual average concentration are representative of chronic levels of 

exposure, and the 30-year mean concentration is assumed to represent cancer drinking water 

exposure from surface drinking water sources. In ground water, estimated peak concentrations are 

assumed to represent acute exposure concentrations and the post-breakthrough average (generally 
16

a multi-year exposure value) estimated concentrations are assumed to represent chronic and cancer 

concentrations. 

Estimated drinking water concentrations (EDWCs) in surface waters are estimated using the Tier 2 

model PRZM/EXAMS (PRZM version 3.12.2, May 2005 and EXAMS version 2.98.4.6, April 

2005). PRZM/EXAMS is publically available on-line at 

http://www.epa.gov/oppefed1/models/water/#przmexamsshell. The index reservoir scenario 

simulating inflow and pesticide transport from streams into a reservoir intake is simulated for the 

drinking water assessment. Crop and regional specific percent crop areas (PCAs) are accounted 

for in EDWCs specific to each crop to factor in the portion of watersheds that are typically subject 

to pesticide loadings and subsequent transport to water bodies. The guidance, “Development and 

Use of Percent Cropped Area and Percent Turf Area Adjustment Factors in Drinking Water 

Exposure Assessments: 2012 Update”, are used to determine PCA values for each crop (EPA, 

2012).

Ground water estimates of concentrations are estimated using the PRZM-GW (version 1.0, 

December 2012) will be used to evaluate ground water exposure. PRZM-GW is publically 

available on-line at http://www.epa.gov/oppefed1/models/water/#przm_gw. Results from the 

long-standing tier I SCI-GROW model (Screening Concentration in GRound Water model, 

Version 2.3, May 16, 2006) will also be shown in comparison with the PRZM-GW modeling 

results according to EFED guidance related to the evaluation period for the recent release of 

PRZM-GW. SCI-GROW is publically available on-line at 

http://www.epa.gov/oppefed1/models/water/#scigrow. 

The fate parameters and use-specific input parameters for the surface water modeling are shown in

Table 9 (for parent rimsulfuron and Table 10 (for the rimsulfuron TTR or residues of concern).

Parameters for the groundwater modeling of the TTR are provided in Input values for the 

groundwater modeling are summarized in Table 11. Aerial applications are only evaluated in this 

Tier 1 drinking water assessment since this is considered to be the application type resulting in the 

most conservative (highest) exposure scenario. Representative PRZM/EXAMS input and output 

files are provided in Appendix A and B.
17

Table 9. PRZM-EXAMS (PE5) input parameters for modeling drinking water exposure to 

parent rimsulfuron.

Input Parameter Value* Reference

APPLICATION DETAILS

Application Rate (lb a.i./Acre) 0.031 (One 

Application)

Equal to the maximum label rate for 

single and annual periods. (See

proposed and existing product 

labels)

Application Intervals (days) NA

Application Dates June 5 (1st run) and 

June 25 (2nd model 

run)

Represents variability between a 

preemergent and postemergent 

application

Percent Crop Area 0.91 Default national value for all 

agricultural land. See:

http://www.epa.gov/oppefed1/models/

water/pca_adjustment_dwa.html

Wetted In? No Product Label. CAM = 2 used for 

PRZM input.

Depth of Incorporation (inches) 0

Method of Application Aerial

CHEMICAL AND FATE PROPERTIES

Molecular Weight 431.44 Value for parent rimsulfuron

Vapor Pressure 1.1x10-8

torr Value for parent rimsulfuron

Solubility in Water (ppm) 7300 MRIDs: 419316-02 and 413563-01.

Partition Coefficient “KOC” 

(L/Kg)

47.5 Average value for parent 

rimsulfuron (MRID 41356336) 

Aerobic Soil Metabolism 

Half-life (days)

44.8 days Determined by taking the 90% upper 

bound C.I. value for the mean 

half-life of Parent in 3 test soils.

(MRID 41356334 and 48332003)

Aerobic Aquatic Metabolism 

Half-life (days)

In an alternative approach, the value was not used and 

hydrolysis half-life at pH 7 was entered. This input value is a 

zero rate under the assumption the hydrolysis is the dominant 

transformation process in the simulated reservoir.
18

Table 9. PRZM-EXAMS (PE5) input parameters for modeling drinking water exposure to 

parent rimsulfuron.

Input Parameter Value* Reference

Anaerobic Aquatic Metabolism 

Half-life (days)

4.2 MRID 48332004.

Hydrolysis Half-life @ pH 7 

(days)

7.2 Average value at pH 7.(MRID 

413563-33) 

Direct Aqueous Photolysis 

Half-life(days)

Stable The half-lives of parent rimsulfuron

in dark were less than in 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 10. PRZM-EXAMS (PE5) input parameters for modeling drinking water exposure to 

rimsulfuron TTR (residues of concern) from sorghum new use and from all registered uses.

Input Parameter Value* Reference

APPLICATION DETAILS

Application Rate (lb a.i./Acre) 0.031 (One Application)

For sorghum new use.

0.0625 for all new uses.

Equal to the maximum label rate for 

single and annual periods. (See 

proposed and existing product 

labels) Application Intervals (days) NA

Application Dates June 5 (1st run) and 

June 25 (2nd model 

run)

Represents variability between a 

preemergent and postemergent 

application

Percent Crop Area 0.91 Default national value for all 

agricultural land. See:

http://www.epa.gov/oppefed1/models/

water/pca_adjustment_dwa.html

Wetted In? No Product Label. CAM = 2 used for 

PRZM input.

Depth of Incorporation (inches) 0 Labels

Method of Application Aerial
19

Table 10. PRZM-EXAMS (PE5) input parameters for modeling drinking water exposure to 

rimsulfuron TTR (residues of concern) from sorghum new use and from all registered uses.

Input Parameter Value* Reference

CHEMICAL AND FATE PROPERTIES

Molecular Weight 324.36 Value for IN-70942, the terminal 

residue of concern.

Vapor Pressure (torr) 1.1x10-8 Default to value for parent rimsulfuron, 

all of the TTR have low volatility.

Solubility (mg/L) 134 Value for IN-70942 at pH 7 and 25 C.

Partition Coefficient “KOC” (L/Kg) 262 Median (lower than avg. value) for 

IN-70942, the terminal degradate in the 

residues of concern (MRID 41356336). 

Outside (not reviewed by EFED) data 

indicates that Koc or Kfoc values near 200 

to 300 in soil may be common – see 

Table 8.)

Aerobic soil Metabolism Half-life 

(days)

1526 Determined by taking the 90% upper 

bound C.I. value for the mean half-life 

of Parent + IN-70941 +IN-70942 in 3 

test soils.

(MRID 41356334 and 48332003)

Aerobic Aquatic Metabolism 

Half-life (days)

In an alternative approach, the value was not used and hydrolysis 

half-live was entered3.

Aerobic Aquatic Metabolism 

Half-life (days)

Zero rate used for this 

simulation.

(517 tentative value.)

Data are preliminary, study in review. 

Model run with the more conservative 

value of a zero rate.

Preliminary half-life determined by 

taking the 90% upper bound C.I. value 

for the mean half-life of Parent + 

IN-70941 +IN-70942 in 2 test soils.

(MRID: 45490802.)

Anaerobic Aquatic Metabolism 

Half-life (days)

174.9 Per Input Guidance, used 3 x the single 

measured half-life of 58.3 days for 

rimsulfuron TTR.

MRID 48332004.

 

3

In two test soils calculated half-lives were 273 and 39 days for the rimsulfuron TTR in the2 test systems (MRIDs 

43288502 and 45490802). 90% upper bound confidence interval of the mean is 517 days as a model input. An 

alternative approach, given the high variability in aerobic soil metabolism rates, is to use the hydrolysis rate of 

IN-70942 at pH 7. This rate is zero.
20

Table 10. PRZM-EXAMS (PE5) input parameters for modeling drinking water exposure to 

rimsulfuron TTR (residues of concern) from sorghum new use and from all registered uses.

Input Parameter Value* Reference

Hydrolysis Half-life @ pH 7 (days) 0 rate

(no hydrolysis)

No evidence of IN-70942 hydrolysis at 

pH 5 to 9 in available study (MRID 

41356333). PMRA(PRVD2008-06) 

reports that a separate study shows 

IN-70942 to be stable over 30 days at 

pH 5, 7, and 9.

Direct Aqueous Photolysis 

Half-life(days)

0 rate

(no photolysis)

The half-lives of parent rimsulfuron in 

dark were less than in irradiated 

samples (MRID 419316-08), no 

evidence of photolysis of IN-70941 and 

IN-70942 available.

* 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 11. PRZM-GW input parameter values for physical chemical and fate properties 

used for rimsulfuron TTR (residues of concern in groundwater sourced drinking water.

PRZM/EXAMS Input 

Parameter

Input Value and Unit Source

Pesticide Properties

Hydrolysis Half-life @ pH 7 (days) 0 

(no hydrolysis)

No evidence of IN-70942 

hydrolysis at pH 5 to 9 in 

available study (MRID 

41356333). 

PMRA(PRVD2008-06) 

reports that a separate study 

shows IN-70942 to be stable 

over 30 days at pH 5, 7, and 9.

Aerobic (top) soil metabolism 

(t1/2)

1526

(also an input for 

SCI-GROW)

Determined by taking the 90% 

upper bound C.I. value for the 

mean half-life of Parent + 

IN-70941 +IN-70942 in 3 test 

soils.

(MRID 41356334 and 

48332003)
21

Table 11. PRZM-GW input parameter values for physical chemical and fate properties 

used for rimsulfuron TTR (residues of concern in groundwater sourced drinking water.

PRZM/EXAMS Input 

Parameter

Input Value and Unit Source

Soil-Water Partition Coefficient 

(Koc)

(mL/g)

262

(also an input for 

SCI-GROW)

Median (lower than avg. 

value) for IN-70942, the 

terminal degradate in the 

residues of concern (MRID 

41356336). Outside (not 

reviewed by EFED) data 

indicates that Koc or Kfoc

values near 200 to 300 in soil 

may be common.)

Application Methods and Crop Management Input Parameters

Crop Scenario and Weather WI Sands

w14920 

(La Crosse, WI)

All PRZM screening scenarios 

run including Delmarva, FL 

Citrus, FL Potato, Georgia 

Coastal, and NC Coastal. WI 

Sands scenario maximum 

exposure scenario and shown in 

this report.

Application Rate

Lb ai/A

0.031 (One Application)

For sorghum new use.

0.0625 for all new uses.

(also an input for 

SCI-GROW)

Equal to the maximum label 

rate for single and annual 

periods.

Application Date June 25 Represents a relatively late 

season application for sorghum 

and most use sites. PRZM-GW 

results are usually not highly date 

sensitive except for certain 

non-persistent pesticides that are 

more stable in subsurface 

horizons.

Number of Applications and 

Retreatment Interval

Single application per 

year.

Maximum single and annual 

application rates are the same 

(product labels)

Application Methods Ground application Most conservative application 

method for leaching to 

groundwater
22

Exposure Modeling Results

Table 12 and Table 13 show the ground water and surface water sourced drinking water exposure 

estimates. Initially both the groundwater and surface water scenarios were run to represent the 

propose use rates on ALS inhibition tolerant sorghum. The highest estimates were from the 

Wisconsin “corn” groundwater scenario for both acute and chronic exposure (by convention, when 

groundwater impacts are assessed, a standard set of 6 scenarios are run to provide a conservative 

estimate of exposure, regardless of the crop site being evaluated). Subsequently the Wisconsin 

scenario was rerun for the TTR or residues of concern to represent exposure potential from the 

highest rimsulfuron application rate for all uses. Based on this the screening concentration that 

should be used in drinking water contributions to dietary exposure are 22.2 for acute and 19.7 for 

chronic or cancer risk assessments. By contrast, for the proposed use on sorghum PRZM-GW 

model estimates upper-bound concentrations of in ground drinking water sources are 12.2 μg/L 

(ppb) for acute exposure and 11.0 μg/L (ppb) for chronic and cancer exposure (Table 12). Lower 

EDWCs for the sorghum new use are predicted for surface water supplies: modeling using 

PRZM/EXAMS predicts that the concentrations of rimsulfuron, IN-70941, and IN-70942 in 

surface drinking water sources are not likely to exceed 1.38 μg/L (ppb) for the acute peak 

concentration, and 0.38 μg/L (ppb) for the chronic and cancer concentration (Table 13). Again, 

PRZM-GW estimates were subsequently run to estimate the highest expected exposure levels 

from all uses (i.e., to represent several crops with higher use rates than the proposed new use) and 

only the higher values in bold text (Table 12) should be used to represent the drinking water 

contribution to dietary risk assessment.

Finally, it should be noted that the predicted chronic exposures for the residues of concern is 

considerably higher than for residues of parent rimsulfuron alone (Table 13), demonstrating that 

the degradation products provide the dominant component to chronic exposure.

Table 12. PRZM-GW and SCI-GROW estimated upper bound concentrations in 

ground water (ppb) for rimsulfuron and degradates of concern including IN-70941 

and IN-70942.

Crops (scenario)

Highest Daily Value

(Acute)

Post-Breakthrough 

Average 

(Chronic and Cancer)

ALS inhibition 

tolerant sorghum

(FL citrus)

7.33 6.0

Sorghum

(WI corn) 12.4 11.3

All uses 

(WI corn) 22.2 19.7

Sorghum

(DE corn) 7.29 5.97
23

Table 12. PRZM-GW and SCI-GROW estimated upper bound concentrations in 

ground water (ppb) for rimsulfuron and degradates of concern including IN-70941 

and IN-70942.

Crops (scenario)

Highest Daily Value

(Acute)

Post-Breakthrough 

Average 

(Chronic and Cancer)

Sorghum

(NC cotton) 8.63 6.96

(GA peanut) 3.49 3.15

(FL potato) 4.19 3.65

SCI-GROW 2.3 0.49 0.49

FL, WI, DE, NC, and GA scenarios are standard for PRZM-GW Tier 1.

Highest acute and chronic DWECs for sorghum new use and all existing uses are

bolded.

Table 13. Maximum Tier I / II rimsulfuron parent and ROC EDWCs for drinking water sourced 

from surface and ground waters based on the proposed application of rimsulfuron to sorghum. *

Use/Rate Modeled: ALS tolerant sorghum, at a rate of 0.031 lbs. a.i./A

Chemical

Maximum PRZM/EXAMS Surface water 

EDWC (ppb)

Maximum PRZM-GW Ground 

water

Acute/Chronic EDWC (ppb)

Acute Value Chronic/Cancer 

Value Acute Chronic

Rimsulfuron Parent 1.08 0.019 NA NA

Rimsulfuron ROC

(residues of concern) 1.38 0.380 12.2 11.0

Exposure Characterization

Although the modeled groundwater concentrations for the TTR (residues of concern) at the Tier I 

level were much higher than the modeled surface water concentrations it is important to 

understand what these concentrations represent. The highest groundwater exposure values were 

obtained from modeling scenarios of some of the most highly vulnerable shallow aquifers in the 

United States. For example, the Wisconsin groundwater scenario where the highest exposure was 

estimated in an area of sand soils overlying an aquifer 30 feet below the land surface. These do not 

represent the concentrations that may occur in a large majority of the US agricultural and noncrop 

land use areas were both weather and soil characteristics result in much lower concentrations of 
24

pesticides reaching groundwater. Furthermore, the concentrations represent the potential exposure 

level for drinking water wells tapping shallow aquifers and directly located in these vulnerable 

areas. Most of the predicted chronic exposure is expected to be to IN-70942 which is the terminal 

residue in the residues of concern definition and is much more persistent in the environment than 

parent rimsulfuron. Further consideration of additional refinements or scenario development 

representative of rimsulfuron applications to sorghum crops is possible, if needed.

In addition to the high persistence of IN-70942 another factor contributing to the increased 

estimated exposure potential to the TTR (compared to parent rimsulfuron) is the apparent 

resistance of IN-70942 to hydrolysis leading to an assumption of no hydrolysis in the modeling. 

This can significantly increase the EDWCs from groundwater modeling in particular compared to 

a similar chemical which undergoes (even slow) hydrolysis in long-term simulations. By 

comparison, parent rimsulfuron is rapidly hydrolyzed in the environment with even more rapid 

hydrolysis under alkaline conditions (half-life of several hours) in particular (Table 4). Additional

data on the environmental fate data such as directed IN-70942 metabolism and hydrolysis studies 

might allow further refinements of modeling inputs which could lead to lower exposure estimates.

Monitoring Data Analysis

Rimsulfuron monitoring data found from stream water, spring water, and ground water sources are 

not yet available for the United States Geological Survey National Water Quality Assessment 

(USGS NAWQA) program as it has only recently been considered for addition to the analyte 

schedule. Monitoring data from NAWQA are available on-line at: 

http://infotrek.er.usgs.gov/nawqa_queries/index.jsp

No monitoring studies could be located for the rimsulfuron degradates included in the residues of 

concern. Kreuger and Adielsson (2008)

4

reported rimsulfuron at concentrations of 0.01 to 0.21 

ug/L in <1% of samples collected from four streams associated with light rimsulfuron use 

intensity (i.e., less than 2% of the watershed treated) It was estimated that the maximum percent of 

applied rimsulfuron appearing in the stream water was 1.79% from 5 years of sampling at 3 sites 

and 9 years of sampling at a 4th site. Much of the difference between these observed concentrations 

and modeled parent concentrations in this risk assessment can be attributed to differences in the 

actual use intensity and the use intensity levels that must be assumed for the risk assessment. 

A monitoring study from Quebec (for parent rimsulfuron only) has been reported in a Proposed 

Re-evaluation Decision by Health Canada5as follows:

Four rivers situated in agricultural regions of Quebec that predominantly grow corn (20–36.5% of 

cropped area) and soya (5.6–13.2% of cropped area) were sampled three times weekly from the 

 

4 Ekohydrologi 103 Uppsala 2008. Avdelningen för vattenvårdslära. Swedish University of Agricultural Sciences, 

Division of Water Quality Management. ISRN SLU-VV-EKOHYD-103-SE; ISSN 0347-9307

5

Pest Management Regulatory Agency, Health Canada. 2008. Proposed Re-evaluation Decision dated January 29, 

2008 (PRVD2008-06).
25

middle of May to the middle of August in the years 2002, 2003, and 2004. Rimsulfuron was 

detected in 2.6% to 14.3% of the samples analyzed. The maximum concentration of rimsulfuron 

detected was in one sample at a concentration of 1.0 mg a.i./L (LOD 0.06 μg a.i./L).

These data have not been received or reviewed by EFED.

Uncertainties and Limitations

There are two main areas of uncertainty with regards to the modeling of rimsulfuron residues of

concern:

(1.)The extent of the representativeness of the most vulnerable areas modeled to actual 

drinking water supplies in rimsulfuron current or future use areas.

(2.) Limitations on the data for model input regarding the fate of rimsulfuron degradates 

included in the residues of concern. Hydrolysis, aerobic soil metabolism, aerobic aquatic, 

and anaerobic aquatic metabolism studies were all terminated before substantial decline 

was observed of IN-70942 and sometimes also of IN-70941. In most studies (not including 

the hydrolysis study), levels of these degradates were observed to level off several 

sampling period before study termination allowing calculation of a TTR half-life but with 

less certainty than if more substantial decline of the “terminal” degradate IN-70942 had 

been observed

References

FIFRA SAP Final Meeting Minutes 2008. Transmittal of Meeting Minutes of the FIFRA 

Scientific Advisory Panel Meeting Held October 28 - 31, 2008 on Selected Issues Associated with 

the Risk Assessment Process for Pesticides with Persistent, Bioaccumulative, and Toxic 

Characteristics. http://www.epa.gov/scipoly/sap/meetings/2008/october/minutes.pdf

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides. U.S. Environmental Protection Agency, Office of Prevention, Pesticides 

and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division. 

Feb. 28, 2002. Online at: 

http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm.

U.S. Environmental Protection Agency 2012.. Development and Use of Percent Cropped Area 

and Percent Turf Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 

Update. EPA Office of Pesticide Programs. Washington, DC.

USEPA. 2013. Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift. U.S. 

Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office 

of Pesticide Programs, Environmental Fate and Effects Division. Dec. 20, 2013. 
26
27

Appendix A – Surface Water Modeling Supporting 

Documentation

PRZM/EXAMS (PE5 Shell) Modeling File (Rimsulfuron Total Toxic 

Residues)

stored as RimsTTR_KSsorg_Rsvr2-aer0625.out

Chemical: Rimsulfuron TTR

PRZM environment: KSsorghumSTD.txt modified Tueday, 29 May 2007 at 12:55:46

EXAMS environment: ir298.exv modified Tueday, 26 August 2008 at 05:14:08

Metfile: w13996.dvf modified Wedday, 3 July 2002 at 09:04:44

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.8062 0.7913 0.7434 0.6492 0.5957 0.2313

1962 0.6804 0.6684 0.623 0.574 0.5437 0.3026

1963 1.237 1.213 1.122 0.9663 0.8695 0.4126

1964 0.7963 0.7825 0.7287 0.6545 0.5975 0.3442

1965 1.309 1.289 1.23 1.058 0.9528 0.4678

1966 0.7308 0.7183 0.6667 0.5885 0.5571 0.3309

1967 0.5235 0.5142 0.4827 0.4225 0.398 0.24

1968 1.458 1.438 1.379 1.209 1.108 0.4836

1969 0.6005 0.5907 0.5732 0.5221 0.4771 0.3354

1970 0.5312 0.5249 0.4925 0.4303 0.3943 0.2288

1971 0.4563 0.4483 0.4185 0.3671 0.3353 0.2177

1972 0.5527 0.5429 0.5186 0.4777 0.4427 0.2281

1973 1.438 1.412 1.31 1.135 1.023 0.4585

1974 0.6968 0.6843 0.6359 0.6063 0.5644 0.3708

1975 0.4106 0.4039 0.3788 0.3361 0.312 0.2282

1976 0.4423 0.4346 0.4089 0.3498 0.3192 0.203

1977 0.8334 0.8223 0.7742 0.7217 0.6613 0.3086

1978 0.647 0.6354 0.5897 0.5441 0.5262 0.3175

1979 1.503 1.485 1.431 1.281 1.162 0.5368

1980 1.126 1.105 1.029 0.9117 0.8497 0.4696

1981 1.078 1.059 0.9976 0.9499 0.8832 0.4903

1982 1.284 1.26 1.167 1.068 0.985 0.4951

1983 1.065 1.047 0.9824 0.8372 0.7499 0.422

1984 0.9807 0.9633 0.902 0.7721 0.6995 0.3738

1985 0.9511 0.9355 0.8812 0.7616 0.6917 0.3574

1986 0.7335 0.7202 0.6863 0.6483 0.6053 0.3399

1987 0.4155 0.4081 0.3789 0.3583 0.3416 0.2187

1988 1.114 1.094 1.035 0.8973 0.8095 0.3577

1989 0.9367 0.9224 0.8775 0.7989 0.7315 0.3933

1990 0.8894 0.8735 0.8478 0.7831 0.7193 0.3821

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.032258064516129 1.503 1.485 1.431 1.281 1.162 0.5368

0.0645161290322581 1.458 1.438 1.379 1.209 1.108 0.4951
28

0.0967741935483871 1.438 1.412 1.31 1.135 1.023 0.4903

0.129032258064516 1.309 1.289 1.23 1.068 0.985 0.4836

0.161290322580645 1.284 1.26 1.167 1.058 0.9528 0.4696

0.193548387096774 1.237 1.213 1.122 0.9663 0.8832 0.4678

0.225806451612903 1.126 1.105 1.035 0.9499 0.8695 0.4585

0.258064516129032 1.114 1.094 1.029 0.9117 0.8497 0.422

0.290322580645161 1.078 1.059 0.9976 0.8973 0.8095 0.4126

0.32258064516129 1.065 1.047 0.9824 0.8372 0.7499 0.3933

0.354838709677419 0.9807 0.9633 0.902 0.7989 0.7315 0.3821

0.387096774193548 0.9511 0.9355 0.8812 0.7831 0.7193 0.3738

0.419354838709677 0.9367 0.9224 0.8775 0.7721 0.6995 0.3708

0.451612903225806 0.8894 0.8735 0.8478 0.7616 0.6917 0.3577

0.483870967741936 0.8334 0.8223 0.7742 0.7217 0.6613 0.3574

0.516129032258065 0.8062 0.7913 0.7434 0.6545 0.6053 0.3442

0.548387096774194 0.7963 0.7825 0.7287 0.6492 0.5975 0.3399

0.580645161290323 0.7335 0.7202 0.6863 0.6483 0.5957 0.3354

0.612903225806452 0.7308 0.7183 0.6667 0.6063 0.5644 0.3309

0.645161290322581 0.6968 0.6843 0.6359 0.5885 0.5571 0.3175

0.67741935483871 0.6804 0.6684 0.623 0.574 0.5437 0.3086

0.709677419354839 0.647 0.6354 0.5897 0.5441 0.5262 0.3026

0.741935483870968 0.6005 0.5907 0.5732 0.5221 0.4771 0.24

0.774193548387097 0.5527 0.5429 0.5186 0.4777 0.4427 0.2313

0.806451612903226 0.5312 0.5249 0.4925 0.4303 0.398 0.2288

0.838709677419355 0.5235 0.5142 0.4827 0.4225 0.3943 0.2282

0.870967741935484 0.4563 0.4483 0.4185 0.3671 0.3416 0.2281

0.903225806451613 0.4423 0.4346 0.4089 0.3583 0.3353 0.2187

0.935483870967742 0.4155 0.4081 0.3789 0.3498 0.3192 0.2177

0.967741935483871 0.4106 0.4039 0.3788 0.3361 0.312 0.203

0.1 1.4251 1.3997 1.302 1.1283 1.0192 0.48963

Average of yearly averages: 0.351543333333333

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: RimsTTR_KSsorg_Rsvr2-aer0625

Metfile: w13996.dvf

PRZM scenario: KSsorghumSTD.txt

EXAMS environment file: ir298.exv

Chemical Name: Rimsulfuron TTR

Description Variable Name Value Units Comments

Molecular weightmwt 324.36 g/mol

Henry's Law Const. henry atm-m^3/mol

Vapor Pressure vapr 1.1e-8 torr

Solubility sol 134 mg/L

Kd Kd mg/L

Koc Koc 207 mg/L

Photolysis half-life kdp 0 days Half-life

Aerobic Aquatic Metabolism kbacw 517 days Halfife

Anaerobic Aquatic Metabolism kbacs 178 days Halfife

Aerobic Soil Metabolism asm 3775 days Halfife

Hydrolysis: pH 7 0 days Half-life

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm
29

Application Rate:TAPP 0.035 kg/ha

Application Efficiency: APPEFF0.95 fraction

Spray Drift DRFT 0.16 fraction of application rate applied to pond

Application Date Date 25-06 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR Reservoir

Flag for runoff calc. RUNOFF total none, monthly or total(average of entire run)

PRZM/EXAMS (PE5 Shell) Modeling File (Parent Rimsulfuron)

stored as Rimsu_KSsorg_Eco6-aer0605.out

Chemical: Rimsulfuron

PRZM environment: KSsorghumSTD.txt modified Tueday, 29 May 2007 at 12:55:46

EXAMS environment: pond298.exv modified Thuday, 24 July 2003 at 09:02:00

Metfile: w13996.dvf modified Wedday, 3 July 2002 at 08:04:44

Water segment concentrations (ppb)

Year Peak 96 hr 21 Day 60 Day 90 Day Yearly

1961 0.2226 0.1845 0.1015 0.04942 0.03339 0.008238

1962 0.115 0.09534 0.06457 0.03327 0.02236 0.005516

1963 0.1108 0.09184 0.06232 0.03066 0.02073 0.005116

1964 0.3219 0.2669 0.1749 0.07267 0.04861 0.01196

1965 0.2049 0.1732 0.1116 0.04616 0.03088 0.007615

1966 0.3238 0.2685 0.1876 0.07917 0.05297 0.01306

1967 0.2419 0.2101 0.1371 0.05755 0.03851 0.009496

1968 0.2891 0.2397 0.1422 0.06391 0.04297 0.01057

1969 0.5924 0.4911 0.2682 0.1149 0.07698 0.01899

1970 0.4506 0.374 0.1929 0.08392 0.05628 0.01388

1971 0.2077 0.1722 0.09681 0.04194 0.02809 0.006928

1972 0.111 0.09205 0.06247 0.03329 0.02258 0.005558

1973 0.1407 0.1173 0.06572 0.04104 0.02853 0.007052

1974 0.3092 0.2566 0.1466 0.06073 0.04066 0.01003

1975 0.4195 0.3645 0.1954 0.08218 0.055 0.01356

1976 0.08749 0.07253 0.04245 0.02458 0.01677 0.004131

1977 0.4187 0.3471 0.2168 0.09605 0.06441 0.01589

1978 0.5381 0.4641 0.2411 0.1071 0.07217 0.01781

1979 0.2137 0.1774 0.09803 0.04283 0.02868 0.007074

1980 0.08749 0.07253 0.0373 0.01496 0.01635 0.004126

1981 0.4649 0.3854 0.2055 0.08959 0.06002 0.0148

1982 0.1646 0.1365 0.08643 0.03621 0.02423 0.005975

1983 0.1293 0.1072 0.07018 0.03258 0.02184 0.005386

1984 0.09302 0.08141 0.05318 0.02353 0.01576 0.003876

1985 0.08749 0.07253 0.05026 0.02701 0.01828 0.004512

1986 0.1366 0.1133 0.06589 0.03902 0.02633 0.006496

1987 0.3095 0.2566 0.1445 0.06649 0.04457 0.01099

1988 0.3632 0.3154 0.165 0.07806 0.05337 0.01314

1989 0.1145 0.09902 0.05623 0.03466 0.02335 0.005762

1990 0.089 0.07575 0.05983 0.0262 0.01755 0.004329

Sorted results

Prob. Peak 96 hr 21 Day 60 Day 90 Day Yearly

0.032258064516129 0.5924 0.4911 0.2682 0.1149 0.07698 0.01899
30

0.0645161290322581 0.5381 0.4641 0.2411 0.1071 0.07217 0.01781

0.0967741935483871 0.4649 0.3854 0.2168 0.09605 0.06441 0.01589

0.129032258064516 0.4506 0.374 0.2055 0.08959 0.06002 0.0148

0.161290322580645 0.4195 0.3645 0.1954 0.08392 0.05628 0.01388

0.193548387096774 0.4187 0.3471 0.1929 0.08218 0.055 0.01356

0.225806451612903 0.3632 0.3154 0.1876 0.07917 0.05337 0.01314

0.258064516129032 0.3238 0.2685 0.1749 0.07806 0.05297 0.01306

0.290322580645161 0.3219 0.2669 0.165 0.07267 0.04861 0.01196

0.32258064516129 0.3095 0.2566 0.1466 0.06649 0.04457 0.01099

0.354838709677419 0.3092 0.2566 0.1445 0.06391 0.04297 0.01057

0.387096774193548 0.2891 0.2397 0.1422 0.06073 0.04066 0.01003

0.419354838709677 0.2419 0.2101 0.1371 0.05755 0.03851 0.009496

0.451612903225806 0.2226 0.1845 0.1116 0.04942 0.03339 0.008238

0.483870967741936 0.2137 0.1774 0.1015 0.04616 0.03088 0.007615

0.516129032258065 0.2077 0.1732 0.09803 0.04283 0.02868 0.007074

0.548387096774194 0.2049 0.1722 0.09681 0.04194 0.02853 0.007052

0.580645161290323 0.1646 0.1365 0.08643 0.04104 0.02809 0.006928

0.612903225806452 0.1407 0.1173 0.07018 0.03902 0.02633 0.006496

0.645161290322581 0.1366 0.1133 0.06589 0.03621 0.02423 0.005975

0.67741935483871 0.1293 0.1072 0.06572 0.03466 0.02335 0.005762

0.709677419354839 0.115 0.09902 0.06457 0.03329 0.02258

0.005558

0.741935483870968 0.1145 0.09534 0.06247 0.03327 0.02236

0.005516

0.774193548387097 0.111 0.09205 0.06232 0.03258 0.02184

0.005386

0.806451612903226 0.1108 0.09184 0.05983 0.03066 0.02073

0.005116

0.838709677419355 0.09302 0.08141 0.05623 0.02701 0.01828

0.004512

0.870967741935484 0.089 0.07575 0.05318 0.0262 0.01755 0.004329

0.903225806451613 0.08749 0.07253 0.05026 0.02458 0.01677

0.004131

0.935483870967742 0.08749 0.07253 0.04245 0.02353 0.01635

0.004126

0.967741935483871 0.08749 0.07253 0.0373 0.01496 0.01576

0.003876

0.1 0.46347 0.38426 0.21567 0.095404 0.063971 0.015781

Average of yearly averages: 0.0090622

Inputs generated by pe5.pl - Novemeber 2006

Data used for this run:

Output File: Rimsu_KSsorg_Eco6-aer0605

Metfile: w13996.dvf

PRZM scenario: KSsorghumSTD.txt

EXAMS environment file: pond298.exv

Chemical Name: Rimsulfuron

Description Variable Name Value Units Comments

Molecular weight mwt 431.44 g/mol

Henry's Law Const. henry atm-m^3/mol

Vapor Pressure vapr 1.1e-8 torr

Solubility sol 7300 mg/L

Kd Kd mg/L

Koc Koc 47.5 mg/L

Photolysis half-life kdp 0 days Half-life

Aerobic Aquatic Metabolism kbacw 0 days Halfife

Anaerobic Aquatic Metabolism kbacs 4.2 days Halfife

Aerobic Soil Metabolism asm 44.8 days Halfife

Hydrolysis: pH 7 7.2 days Half-life
31

Method: CAM 2 integer See PRZM manual

Incorporation Depth: DEPI 0 cm

Application Rate: TAPP 0.035 kg/ha

Application Efficiency: APPEFF 0.95 fraction

Spray Drift DRFT 0.05 fraction of application rate applied to pond

Application Date Date 05-06 dd/mm or dd/mmm or dd-mm or dd-mmm

Record 17: FILTRA

IPSCND 1

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5

Flag for Index Res. Run IR EPA Pond

Flag for runoff calc. RUNOFF none none, monthly or total(average of entire run)
32

Appendix B – Ground Water Modeling Supporting

Documentation

PRZM-GW Modeling Input and Output Files

PRZM-GW estimated upper bound concentrations in ground water (ppb) for 

rimsulfuron and degradates of concern including IN-70941 and IN-70942.

Crops (scenario)

Highest Daily Value

(Acute)

Post-Breakthrough 

Average 

(Chronic and Cancer)

ALS inhibition 

tolerant sorghum

(FL citrus)

 7.33 6.0

Sorghum

(WI corn) 12.4 11.3

All uses

(WI corn) 22.2 20.1

Sorghum

(DE corn) 7.29 5.97

Sorghum

(NC cotton) 8.63 6.96

(GA peanut) 3.49 3.15

(FL potato) 4.19 3.65

Highest acute and chronic DWECs for sorghum new use and all existing uses are

bolded.

PRZM-GW Shell Processing File (WI Corn Scenario, 0.0625 lb ai/A 

Rate)

Rimsulfuron TTR

0

1526

True

262

1

1

25,,,,,,,,,,
33

06,,,,,,,,,,

0.07,,,,,,,,,,

1,,,,,,,,,,

,,,,,,,,,,

True

1

last

Wisconsin Corn - WI Central Sands

C:\Models\Inputs\Metfiles\w14920.dvf

0.76

0.36

18

90

100

0.25

01

05

21

07

20

10

1

2

0.1

0

4.0

9

1.63,1.63,1.68,1.68,1.59,1.59,1.59,1.59

0.088,0.088,0.079,0.079,0.068,0.068,0.068

0.034,0.034,0.025,0.025,0.016,0.016,0.016

0.46,0.46,0.14,0.09,0.09,0.08,0.07,0.07

True

95,95,96,96,97,97,97,97

2.3,2.3,2.5,2.5,1.7,1.7,1.7,1.7

5.6

0.2

50

1
34

PRZM-GW Input File (WI Corn Scenario, 0.0625 lb ai/A Rate)

3/3/2014 7:09:17 PM; Rimsulfuron TTR; Wisconsin Corn - WI Central Sands

User Interface Version: PRZM-GW (Version 1.01)

***Record 3 

 0.76 0.36 0 18 1 1

***Record 6

 0

***Record 8

 1

***Record 9

 1 0.25 90 100 1 10 10 10 0 100

***Record 10

 30

***Record 11

 010561 210761 201061 1

 010562 210762 201062 1

 010563 210763 201063 1

 010564 210764 201064 1

 010565 210765 201065 1

 010566 210766 201066 1

 010567 210767 201067 1

 010568 210768 201068 1

 010569 210769 201069 1

 010570 210770 201070 1

 010571 210771 201071 1

 010572 210772 201072 1

 010573 210773 201073 1

 010574 210774 201074 1

 010575 210775 201075 1

 010576 210776 201076 1

 010577 210777 201077 1

 010578 210778 201078 1

 010579 210779 201079 1

 010580 210780 201080 1

 010581 210781 201081 1

 010582 210782 201082 1

 010583 210783 201083 1

 010584 210784 201084 1

 010585 210785 201085 1

 010586 210786 201086 1

 010587 210787 201087 1

 010588 210788 201088 1

 010589 210789 201089 1

 010590 210790 201090 1

***Record 12

Place Holder

***Record 13

 30 1 0 0
35

***Record 15

Place Holder

***Record 16

 25 661 0 1 4 0.07 1 0

 25 662 0 1 4 0.07 1 0

 25 663 0 1 4 0.07 1 0

 25 664 0 1 4 0.07 1 0

 25 665 0 1 4 0.07 1 0

 25 666 0 1 4 0.07 1 0

 25 667 0 1 4 0.07 1 0

 25 668 0 1 4 0.07 1 0

 25 669 0 1 4 0.07 1 0

 25 670 0 1 4 0.07 1 0

 25 671 0 1 4 0.07 1 0

 25 672 0 1 4 0.07 1 0

 25 673 0 1 4 0.07 1 0

 25 674 0 1 4 0.07 1 0

 25 675 0 1 4 0.07 1 0

 25 676 0 1 4 0.07 1 0

 25 677 0 1 4 0.07 1 0

 25 678 0 1 4 0.07 1 0

 25 679 0 1 4 0.07 1 0

 25 680 0 1 4 0.07 1 0

 25 681 0 1 4 0.07 1 0

 25 682 0 1 4 0.07 1 0

 25 683 0 1 4 0.07 1 0

 25 684 0 1 4 0.07 1 0

 25 685 0 1 4 0.07 1 0

 25 686 0 1 4 0.07 1 0

 25 687 0 1 4 0.07 1 0

 25 688 0 1 4 0.07 1 0

 25 689 0 1 4 0.07 1 0

 25 690 0 1 4 0.07 1 0

***Record 17

 0 1 0

***Record 19

Place Holder

***Record 20

 1000 0 0 0 0 0 2 1 1 0

***Record 26

 0 0 0

***Record 27

 3 0.1 0 4.0

***Record 31

 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.97 10.0

***Record 32

 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6

***Record 32A

 2.00 25.0
36

***Record 33

 8

*** Record 34,36,37 Horizon 1

 1 10 1.63 0.088 0 0 0

 0.0004540.000454 0

 1 0.088 0.034 0.46 1.2052

 5.6 95 2.3 0 0

*** Record 34,36,37 Horizon 2

 2 10 1.63 0.088 0 0 0

 0.0004290.000429 0

 5 0.088 0.034 0.46 1.2052

 5.6 95 2.3 0 0

*** Record 34,36,37 Horizon 3

 3 20 1.68 0.079 0 0 0

 0.0003530.000353 0

 20 0.079 0.025 0.14 0.3668

 5.6 96 2.5 0 0

*** Record 34,36,37 Horizon 4

 4 20 1.68 0.079 0 0 0

 0.0002520.000252 0

 20 0.079 0.025 0.09 0.2358

 5.6 96 2.5 0 0

*** Record 34,36,37 Horizon 5

 5 20 1.59 0.068 0 0 0

 0.0001510.000151 0

 20 0.068 0.016 0.09 0.2358

 5.6 97 1.7 0 0

*** Record 34,36,37 Horizon 6

 6 20 1.59 0.068 0 0 0

 5.05E-055.05E-05 0

 20 0.068 0.016 0.08 0.2096

 5.6 97 1.7 0 0

*** Record 34,36,37 Horizon 7

 7 800 1.59 0.068 0 0 0

 0 0 0

 50 0.068 0.016 0.07 0.1834

 5.6 97 1.7 0 0

*** Record 34,36,37 Horizon 8

 8 100 1.59 0.396 0 0 0

 0 0 0

 50 0.396 0.001 0.07 0.1834

 5.6 97 1.7 0 0

*** Record 40

 0

*** Record 42

 YEAR 10 YEAR 10 YEAR 10 

0

*** Record 45

 3 YEAR
37

*** Record 46

 DCON1 TAVE 33 34 1.0E3

 INFL TCUM 33 33 0.00277

 IRRG TSER
38

Figure 2. PRZM-GW rimsulfuron residues of concern concentration time series chemographs 

(30-year simulation).

FL citrus – sorghum use

WI corn – sorghum use
39

DE Corn
40

WI Corn (highest rate for all use sites)