1

Problem Formulation for the Environmental Fate, 

Ecological Risk, Endangered Species, and Human 

Health Drinking Water Exposure Assessments in 

Support of the Registration Review of Rimsulfuron

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

pyridinesulfonamide

CAS: 122931-48-0

PC Code: 129009

Prepared by:

Joseph DeCant, Ecologist, ERB V

Michael Barrett, Senior Chemist, ERB V

U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch V

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

Anita Ullagaddi, Biologist, ERB I

William Shaughnessy, Chemist, ERB I

Approved by:

Mah Shamim, PhD, Branch Chief, ERB V

Date: September 13, 2012
2

Table of Contents

PURPOSE ...............................................................................................................................................................3

STRESSOR SOURCE AND DISTRIBUTION.................................................................................................................3

MECHANISM OF ACTION AND NATURE OF CHEMICAL............................................................................................................3

OVERVIEW OF PESTICIDE USE AND USAGE ..........................................................................................................................4

PROBLEM FORMULATION......................................................................................................................................7

NATURE OF REGULATORY ACTION.....................................................................................................................................7

PREVIOUS ASSESSMENTS .................................................................................................................................................8

EXPOSURE CHARACTERISTICS ................................................................................................................................8

ENVIRONMENTAL FATE ...................................................................................................................................................8

ECOLOGICAL EFFECTS........................................................................................................................................... 15

TOXICITY TO AQUATIC ORGANISMS .................................................................................................................................15

TOXICITY TO TERRESTRIAL ORGANISMS ............................................................................................................................16

DEGRADATE TOXICITY ...................................................................................................................................................18

INCIDENT REPORTS.......................................................................................................................................................21

ECOSYSTEMS POTENTIALLY AT RISK..................................................................................................................... 22

RISK HYPOTHESIS.........................................................................................................................................................23

Risk Hypothesis Description ...............................................................................................................................23

ANALYSIS PLAN.................................................................................................................................................... 25

STRESSORS OF CONCERN...............................................................................................................................................25

MEASURES OF EXPOSURE ..............................................................................................................................................26

MEASURES OF EFFECT...................................................................................................................................................26

ENDANGERED SPECIES ASSESSMENTS...............................................................................................................................28

PRELIMINARY IDENTIFICATION OF DATA GAPS.................................................................................................... 28

ENVIRONMENTAL FATE .................................................................................................................................................28

Environmental Fate Data Gaps..........................................................................................................................30

ECOLOGICAL EFFECTS DATA ...........................................................................................................................................31

REFERENCES......................................................................................................................................................... 34

APPENDIX 1. SUBMITTED ENVIRONMENTAL FATE AND EFFECTS STUDIES .......................................................... 36

APPENDIX 2. UNCERTAINTIES RELATED TO THE USE OF INCIDENT INFORMATION FROM THE ECOLOGICAL 

INCIDENT INFORMATION SYSTEM ....................................................................................................................... 46

APPENDIX 3. SIP V.1.0 INPUTS AND OUTPUTS .................................................................................................... 48

APPENDIX 4. STIR V.1.0 INPUTS AND OUTPUTS .................................................................................................. 50

APPENDIX 5. THE RISK QUOTIENT METHOD AND LEVELS OF CONCERN .............................................................. 52
3

Purpose

The purpose of this problem formulation is to provide an understanding of the environmental fate 

and ecological effects of the registered uses of rimsulfuron. Rimsulfuron is a sulfonylurea 

herbicide that is currently registered for various agricultural commodities and non-agricultural 

uses and can be applied using a variety of methods. This document will provide a plan for 

analyzing data relevant to rimsulfuron, as well as for conducting environmental fate and 

ecological risk, endangered species, and human health drinking water assessments for its 

registered uses. Additionally, this problem formulation is intended to identify data gaps, 

uncertainties, and potential assumptions used to address those uncertainties, relative to 

characterizing the ecological risk associated with the registered uses of rimsulfuron. 

Stressor Source and Distribution

Mechanism of Action and Nature of Chemical

Rimsulfuron is a selective/systemic pyrimidinyl sulfonylurea herbicide and a member of the 

sulfonylurea class of compounds1. It has a mode of action that inhibits acetolactate synthase 

ALS (ALS is also known as acetohydroxyacid synthase AHAS) (HRAC Group B)2. ALS or 

AHAS is a key enzyme in the biosynthesis of certain amino acids in plants. The mode of action 

appears to require relatively low concentrations of the chemical. It is noted that repeated 

application might cause weeds to develop resistance to the sulfonylurea family of herbicides that 

would require the application of an herbicide resistance program.

In rimsulfuron the sulfonylurea moiety serves as a “bridge” between aminopyrimidine (the “Q” 

moiety on the -NH- or amine side of bridge) and pyridine (“A” on the -SO2- or sulfonyl side of 

bridge) ring structures in the molecule as shown below in Figure 1. 

 

1 URL: http://www.alanwood.net/pesticides/class_herbicides.html#sulfonylurea_herbicides

2 URL: 

Stidham, Mark A. 1991. Herbicides That Inhibit Acetohydroxyacid Synthase. Weed Science 39(3):428-434.
4

Generic Molecular Structure for Sulfonylurea Herbicides

Rimsulfuron Chemical Structure

Figure 1. Molecular structure of a sulfonylurea and rimsulfuron.

Overview of Pesticide Use and Usage

Rimsulfuron is applied pre-emergent or post-emergent for weed control in various crop / noncrop 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 the following crop / non-agricultural use sites (Table 1); note 

that some use site descriptions on some label sites are not well-defined.

N

N

O

O

H3C

H3C

N

H

N

S O

O

CH2

H3C

N

H

S

O

O

O
5

Table 1. List of uses currently registered for rimsulfuron.

Agricultural crops/soils 

(unspecified)

Crabapple Pecan

Agricultural rights-ofway/fencerows/hedgerowsDrainage systems Pistachio

Agricultural uncultivated areas Filbert (hazelnut) Plum

Agricultural/farm premises Golf course turf plum, Japanese

Airports/landing fields Grapefruit potato, white/Irish

Almond Grapes Prune

Apple Hickory nut Pummelo (shaddock)

Apricot Industrial / construction 

areas (outdoor)

Quince

Beech nut Kumquat Rangeland

Butternut Lemon Recreation area lawns 

(public)

Calamondin Lime Sewage disposal areas

Cashew Loquat Sorghum

Cherry Macadamia nut (bushnut) Soybeans (unspecified)

Chestnut Mayhaw (hawthorn) Tangelo

Chinquapin Nectarine Tangerines

Citron (citrus) Nonagricultural rights-ofway/fencerows/hedgerowsTomato

Citrus hybrids other than tangelo Nonagricultural uncultivated 

areas/soils

Walnut (English/black)

Commercial/industrial lawns Orange

Commercial/institutional/industrial 

premises/equipment (outdoor)

Ornamental sod farm (turf)

Corn (unspecified) Paved areas (private 

roads/sidewalks)

Corn, field Peach

Cotton (unspecified) Pear

Major use sites include potatoes, tomatoes, corn, almonds, grapes, apricots, peaches, 

plums/prunes, apples, cherries, pears, pistachios, nectarines, oranges, lemons, walnuts, cotton, 

soybeans, and sweet corn (

Table 2; USEPA 2011a). The greatest agricultural use intensity is estimated to occur in parts of 

the Midwest and California (Figure 2)

3

. Further details on rimsulfuron usage profile and history 

are available in the public docket for the registration review of Rimsulfuron.

 

3

Pesticide usage in Figure 2 is displayed as average pounds (for the years 2006-2010) per 1,000 acres of farmland in 

a Crop Reporting District (CRD - aggregates of counties used in crop data reporting by the National Agricultural 

Statistics Service) to normalize for the variation in farmland between CRDs. Usage is based on private market

surveys of pesticide use in agriculture (Proprietary Data, 2006-2010). The survey data are limited to the states that 

represent the top 80-90% of acreage for the individual crops, therefore, use may be occurring in regions outside the 

scope of the survey. CRDs showing no usage of pesticides may be due to either the lack of pesticide use in the 

region or non-participation in the agricultural surveys. In addition, across the years, there may be variations in the 

specific crops included in the CRD survey. This may result in a lower annual average for the CRD.
6

Table 2. Screening level estimates of agricultural usage of rimsulfuron.

Percent Crop 

Treated

Crop Lbs. A.I. Avg. Max.

Potatoes 6,000 30 35

Tomatoes 5,000 30 50

Corn 70,000 10 15

Almonds 6,000 10 15

Grapes 2,000 10 15

Apricots <500 10 20

Peaches <500 10 15

Plums/Prunes <500 10 15

Apples 1,000 5 10

Cherries <500 5 10

Pears <500 5 10

Pistachios <500 5 5

Nectarines <500 4 4

Oranges 1,000 2.5 5

Lemons <500 2.5 5

Walnuts <500 2.5 5

Cotton <500 1 2.5

Soybeans <500 1 2.5

Sweet Corn , 

other corn for 

food uses

<500 1 2.5
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Figure 2. Rimsulfuron agricultural pesticide usage intensity 2006 - 2010 at the Crop 

Reporting District (CRD) level.

For additional details about Figure 2, please refer to BEAD Chemical Profile (BEAD 2012). It 

is noted that the maps show usage all throughout the continental US, except for the southern 

states, with higher intensity use in California, the Northwest coast states and the Corn Belt.

Problem Formulation

Nature of Regulatory Action

The Food Quality Protection Act of 1996 mandated EPA to implement a program for reassessing 

the risks of currently registered pesticides, i.e., registration review4. All pesticides distributed or 

sold in the United States generally must be registered by EPA. The decision to register a 

pesticide is based on the consideration of scientific data and other factors showing that it will not 

cause unreasonable risks to human health, workers, or the environment when used as directed on 

product labeling. The registration review program is intended to ensure that, as the ability to 

assess risk evolves and as policies and practices change, all registered pesticides continue to 

 

4

http://www.epa.gov/oppsrrd1/registration_review/
8

meet the statutory standard of no unreasonable adverse effects to human health and the 

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the new registration review program, the Agency periodically reevaluates pesticides to 

ensure that as change occurs, products in the marketplace can be used safely. 

As part of the implementation of the new Registration Review program pursuant to Section 3(g) 

of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its 

evaluation to determine whether rimsulfuron continues to meet the FIFRA standard for 

registration. This problem formulation for the environmental fate and ecological risk assessment 

chapter in support of the registration review is intended for the initial docket that opens the 

public phase of the review process. 

Previous Assessments

The last risk assessment conducted for rimsulfuron was an abbreviated assessment in March of 

2012 for use on Chicory (D391028). This latter assessment included information from and was 

based on a previous assessment (D358867+) for corn and soybean conducted in 2009. The 

assessment for chicory found that these applications result in exposures exceeding Levels of 

Concern (LOCs) for risk to both listed and non-listed terrestrial plants. A previous assessment in 

2011 for uses on Caneberry 13-07A and Bushberry Subgroup 13-07B (D384591) also found risk 

to federally listed aquatic vascular plants.

Exposure Characteristics

Environmental Fate

Rimsulfuron is a relatively nonpersistent and relatively mobile pesticide. Table 3 provides a 

summary of its physicochemical and environmental fate properties. Rimsulfuron does have 

persistent degradation products unlike other US-registered sulfonylurea herbicides, whose 

degradates are generally the product of the rupture of the sulfonylurea bridge (sometimes after 

formation of transitional degradates that retain the intact sulfonylurea bridge). The most 

persistent moieties of this herbicide involve contraction of the sulfonylurea bridge into a urea or 

amine bridge. The transformation products are discussed further below.

Upon pre-emergent / post-emergent application of rimsulfuron for weed control, the major 

quantities of the applied material is expected to be deposited on soil surfaces and be distributed 

within the surface layer of the soil depending on the amount of rainfall/irrigation for the required 

wetting-in. Other relatively smaller quantities of the parent may reach nearby terrestrial/aquatic 

systems by drift (but it should be noted that some crop species can be injured by very-low dose 

exposure to some sulfonylurea herbicides). Runoff to surface waters may occur in the form of 

parent or as the more persistent transformation products (especially IN-70941 and IN-70942, see 

Table 4 and Table 5 for a summary of data on degradates formed in fate studies and the 

identities of these degradates, respectively) depending on how soon after application the runoff 

event occurs. 
9

Rimsulfuron has a low vapor pressure (1.447 x10-11 atms. at 25 oC) and is highly soluble in water 

(solubility 7300 ppm at 25

oC and pH 7). Based on submitted environmental fate studies, the 

chemical is short lived in aqueous systems (mainly affected by hydrolysis with hydrolysis halflives ranging from 5-7 days in acidic/neutral conditions and <1 day in alkaline conditions). 

Table 3. Nomenclature and physicochemical properties of rimsulfuron.

Parameter Value Reference

Chemical Classification Pyrimidinyl Sulfonylurea

Registrant 

Data and 

PPDB 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

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

Parent rimsulfuron is relatively short-lived in aerobic/anaerobic soil systems. In three aerobic 

soil metabolism test soils (two of these studies are still in review, so these values are 

preliminary), the t1/2 ranged from 21 to 48 days. Concentrations of the IN-70941 degradate 

peaked within 90 days after application and were still present at 20% of applied in two of the test 

soils incubated at 20o C. IN-70942 concentrations rose subsequent to formation of IN-70941 and 

had not perceptibly declined at study termination in any of the three test soils. Shorter half-lives 

were determined under field conditions: t1/2= 5 to 18 days. In an anaerobic pond water / 

sediment system rimsulfuron degraded rapidly (t1/2= 4 to 5 days) and neither IN-70941 or IN70942 were particularly persistent (IN-70941 peak concentrations were 43 to 45% 14 days after 

application of rimsulfuron to the test system and later declined to less than 1% while IN-70942 

concentrations peaked at 10 to 12% 30 days after application and declined to 0.1% of applied 

when the study was terminated after 365 days). None of the transformation products from IN-
10

70941 were identified; however, none were reported to peak at greater than 10% of the applied 

parent on a molar basis. In contrast, in the same pond water / sediment test system sterilized by 

autoclaving, IN-70942 reached a peak concentration of 37 to 42% of applied rimsulfuron from 

30 to 365 days post-treatment (the last sampling date). Rimsulfuron appears not to be subject to

aqueous or soil photolysis. 

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): IN70941 (degrading into IN-70942)

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 IN70941 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.

419316-08, 

Acceptable

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).

These data are still in review:

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).

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).

Major degradates (from contraction of the sulfonylurea bridge): IN70941 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
11

Parameter Value MRID

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).

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

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.

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.

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.)

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.

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 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 
12

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 (INE9260) (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). Please refer to Figure 3 for structures of the degradates and identified 

pathways; full chemical names are provided in Table 5. In contrast, 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
13

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

values).

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.
14

N

S O

O

CH2

H3C

S

O

O

H2N

Figure 3. Identified transformation/degradation pathways for rimsulfuron in soil and 

water systems.

Parent Rimsulfuron 

N

S O

O

CH2

H3C

N

N

O

O

H3C

H3C

N

CO

NH2

IN-70941: Rimsulfuron Urea 

degradate

N

S O

O

CH2

H3C

N

N

O

O

H3C

H3C

NH

N

N

O

O

H3C

H3C

NH2

IN-J290: Pyrimidine Amine

IN-E9260: Pyridine Sulfonamide

N

N

O

O

H3C

H3C

NH

CO

NH2

Sulfonylurea-Bridge Cleavage (MINOR 

in all systems, Except as indicated)

MAJOR in 

one Aerobic 

Soil Only

Sulfonylurea-Bridge Contraction (MAJOR 

in all systems)

Sulfonylurea Bridge

Pyrimidine Ring Pyridine Ring

IN-70942: Rimsulfuron 

Amine degradate

IN-T5831

Pyridine Urea

N

N

O

O

H3C

H3C

N

H

N

S O

O

CH2

H3C

N

H

S

O

O

O
15

Ecological effects

Toxicity to Aquatic Organisms

Rimsulfuron is considered practically non-toxic to most aquatic animals on an acute basis (Table 

7). This includes freshwater fish (rainbow trout LC50 > 390 ppm; bluegill sunfish LC50 > 390 

ppm), freshwater invertebrates (Daphnia magna LC50 > 360 ppm), and estuarine/marine 

organisms (sheepshead minnow LC50 > 110 ppm; mysid shrimp LC50 > 110 ppm; oyster shell 

deposition EC50 > 120 ppm). In contrast, vascular plants are extremely sensitive to rimsulfuron. 

The most sensitive aquatic plant tested is duckweed (EC50 = 11.6 ppb, NOAEC = 0.09 ppb). 

Non-vascular plants appear to be less sensitive than aquatic vascular plants, with the most 

potentially sensitive being Selenastrum capricornutum that showed a non-definitive EC50 and a 

NOAEC of 29 ppb. 

While information exists on the acute toxicity of rimsulfuron to aquatic animals, chronic toxicity 

data is either lacking or in review. Three freshwater fish early life-stage (ELS) studies are 

currently in review, as are two daphnid life-cycle studies, in order to determine the chronic 

toxicity of rimsulfuron to freshwater fish and invertebrates. One of the fish ELS studies and one 

of the daphnid life-cycle studies tests the effects of a formulated product, while the other studies 

test the technical product of rimsulfuron. However, no data have been submitted relative to the 

chronic toxicity of rimsulfuron to marine/estuarine species. Depending on the acceptability of 

the freshwater studies, they may provide insight into the potential for toxicity to estuarine/marine 

species due to chronic exposure to rimsulfuron. 

Table 7. Most sensitive endpoints for aquatic species.

Species

(common 

name)

Measure of 

Effect

EndpointDuration

(hours)

Toxicity 

value (mg 

a.i./L)

Test 

substance 

(% a.i.)

Study 

Classification

Reference

(MRID)

Freshwater Fish

Lepomis 

macrochirus

(Bluegill 

Sunfish)

Mortality LC50 96 >390 98.8% Acceptable 41356308

Oncorhynchus 

mykiss

(Rainbow 

Trout)

Mortality LC50 96 >390 98.8% Acceptable 41356307

Freshwater Invertebrates

Daphnia 

magna

(Water Flea)

Mortality EC50 48 >390 98.8% Acceptable 41356309

Estuarine/Marine Fish

Cypridon 

variegatus

(Sheepshead 

Minnow)

Mortality LC50 96 >110 99% Acceptable 42471303
16

Species

(common 

name)

Measure of 

Effect

EndpointDuration

(hours)

Toxicity 

value (mg 

a.i./L)

Test 

substance 

(% a.i.)

Study 

Classification

Reference

(MRID)

Estuarine/Marine Invertebrates

Americamysis 

bahia

(Mysid 

shrimp)

Mortality LC50 96 >110 99% Acceptable 42471302

Crassostrea 

virginica

(Eastern 

oyster)

Shell 

deposition EC50 96 >120 99% Acceptable 42471301

Aquatic Plant

Lemna gibba

(Duckweed) Biomass EC50 14 days 11.6 ppb 98.57 Acceptable 42471308

Selenastrum 

capricornutum

(Green algae)

Cell count, 

biomass, 

growth rate

EC50 120 >29 ppb 98.57 Acceptable 42471305

Toxicity to Terrestrial Organisms

Rimsulfuron is considered practically non-toxic to most terrestrial animals (Table 8). This 

includes birds (mallard LD50 > 2000 mg/kg; bobwhite quail LD50 > 2250 mg/kg; mallard and 

bobwhite quail LC50 > 5620 ppm), mammals (rat LD50 > 5000 mg/kg), and bees (LD50 > 100 

ug/bee). The NOAEC in an avian reproduction study with bobwhite quail is 1250 ppm (No 

adverse effects were identified up to the maximum dose), and the NOAEL for mammals based 

on the rat is 165 mg/kg body weight (bwt). No data have been submitted relative to the acute 

toxicity to passerine bird species or to the chronic toxicity to the Mallard duck. These two 

species therefore represent an uncertainty; however, given the lack of effects in the other avian 

studies it is unlikely that these other species would be sensitive to rimsulfuron.

In contrast, plants are extremely sensitive to rimsulfuron. For seedling emergence, plant height 

was the most sensitive parameter (EC25 = 0.0006 lb ai/A for the most sensitive monocot and 

EC25 = 0.00013 for the most sensitive dicot). For vegetative vigor, root weight was the most 

sensitive parameter (EC25 = 0.00004 lb ai/A for the most sensitive monocot and 0.00003 lb ai/A 

for the most sensitive dicot). For both types of plant studies, NOAEL values could not be 

determined for the most sensitive species because effects were seen at all test concentrations. 

And in each study the technical grade active ingredient was mixed with a buffered solution and 

combined with a surfactant rather than the test being conducted with a typical end-use product as 

required by the CFR 40 part 158 guidelines.

Terrestrial plants appear to be very sensitive to rimsulfuron exposure. While toxicity data were 

available for endpoints related to systemic growth, seedling emergence and visual injury, these 

guideline studies are not designed to capture reproductive endpoints. There is some evidence5to 

 

5

Snipes et al. 1992, Bansal et al. 1999; Fletcher et al. 1993, 1995,1996; Bhatti et al. 1995; Al-Khatib et al. 1992; 

Boutin et al. 2000; Asghari and Evans 1992
17

suggest plant reproduction may be affected by sulfonylurea herbicides at levels below effects on 

vegetative growth or visual injury (Fletcher et al., 1993). Uncertainty regarding the potentially 

greater sensitivity of terrestrial plant reproduction has been discussed extensively in the 

environmental fate and effects assessment for chlorsulfuron (D330621). However, an analysis 

by the EFED Plant Technical Team revealed that plants exposed to SU herbicides during the 

reproductive life stage are likely to exhibit adverse effects on reproduction, generally expressed 

as reduced seed number or reduced seed weight. Based on the latest data analysis, these effects 

are expected to occur at similar concentrations to those effects determined in the guideline 

vegetative vigor studies (850.4150) so further data are not requested at this time.

Table 8. Most sensitive endpoints for terrestrial species.

Species 

(common 

name)

Measure of 

effect End-point Toxicity 

Value 

Test 

Substance 

(% a.i.)

Study 

Classification

Reference

(MRID)

Birds

Anas 

platyrhynchos

(Mallard Duck)

Mortality

LD50

>2000 ppm

>2250 ppm

98.8%

25%

Acceptable

Acceptable

41931629

41931630

LC50

>5620 ppm

>1378 ppm

98.8%

25%

Acceptable

Supplemental

41356306

41931633

Colinus 

virginianus

(Northern 

Bobwhite Quail)

Mortality

LD50

>2000 ppm

>2250 ppm

98.8%

25%

Acceptable

Supplemental

41356304

41931631

LC50

>5620 ppm

>1339 ppm

98.8%

25%

Acceptable

Supplemental

41356305

41931632

Colinus 

virginianus

(Northern 

Bobwhite Quail)

Avian 

Reproduction

NOAEC 1250 ppm

99% Acceptable 43277201

LOAEC >1250 ppm

Mammals

Rattus 

norvegicus

(laboratory rat)

Mortality

Oral LD50 >5000 mg/kg

25%

98.8%

25%

25.7%

Acceptable

Acceptable

Acceptable

Acceptable

41356311

41356310

41931634

47091007

Inhalation 

LC50

>5.4 mg/L 

(TGAI)

98.8%

26.5%

25%

98.6%

Acceptable

Acceptable

Acceptable

Acceptable

41356314

41931625

41931637

41931636
18

Species 

(common 

name)

Measure of 

effect End-point Toxicity 

Value 

Test 

Substance 

(% a.i.)

Study 

Classification

Reference

(MRID)

Reproductive 

and fetal 

toxicity, lower 

body weight 

gain

NOAEL 165 mg/kg 

bwt

98.8% Acceptable 41931644

LOAEL 830 mg/kg 

bwt

Terrestrial Invertebrates

Apis mellifera

(Honey Bee) Mortality LD50 >100 μg/bee 98.8% Acceptable 41356331

Terrestrial Plants1

Sorghum bicolor

(sorghum)

Seedling 

Emergence

EC25

0.0006 98.8% Supplemental 42471304

Triticum 

aestivum

(wheat)

Vegetative 

Vigor 0.00004 98.8% Supplemental 42471304

Brassica 

campestris

(field mustard)

Seedling 

Emergence

EC25

0.00013 98.8% Supplemental 42471304

Vegetative 

Vigor 0.00003 98.8% Supplemental 42471304

1 Toxicity values are in lbs/Acre corresponding to a rate of application.

Degradate Toxicity

A number of degradates of parent rimsulfuron have been identified from the various fate studies, 

as previously highlighted in Figure 3 and Table 5. From the list of degradates that have been 

identified, only three of them are considered major degradates with formation rates at or above 

10% of the applied parent compound in one or more studies and only two of these degradates 

were consistently detected at peak concentrations that were greater than 5 to 10% of applied 

material. None of the degradates, major or minor, have an intact sulfonylurea bridge. The two 

consistently major degradates (IN-70941 and IN-70942) are the product of bridge contraction to 

form a urea compound and/or an amine derivative. Data are available for a few taxa on the 

major degradates as summarized in Table 9, and, given uncertainty because of non-definitive 

endpoints, none of the studies show any of the degradates to be more toxic than the parent 

compound. Estimates of toxicity using structure activity relationships (ECOSAR in EpiSuite v. 
19

4.16) for the three major degradates were calculated and are summarized in Table 10. It is also 

important to note that the EPA Health Effects Division (HED) Metabolism Committee concluded 

that only parent rimsulfuron was of toxicological concern to mammals7.

Table 9. Toxicity of the three major degradates of rimsulfuron to various taxa.

Degradate Organism Toxicity MRID

(classification)

IN-70941

Sorghum/Oilseed 

Rape

NOAEC: 0.122 lb/A

EC25: > 0.122 lb/A

47702508

(Supplemental)

Duckweed NOAEC: 3.6 mg/L

EC50: > 11 mg/L

47702512

(Acceptable)

IN-70942

Rainbow Trout LC50: > 175 mg/L 47702502

(Supplemental)

Daphnia magna EC50: 179 mg/L 47702505

(Supplemental)

Chironomus riparius NOAEC: 0.143 mg/L 

(pore water)

LOAEC: > 0.143 

mg/L (pore water)

47702503

(Supplemental)

Sorghum/Oilseed 

Rape

NOAEC: 0.122 lb/A

EC25: > 0.122 lb/A

47702507

(Supplemental)

Duckweed NOAEC: 0.0159 

mg/L

EC50: > 0.0159 mg/L

47702509

(Supplemental)

Selenastrum 

capricornutum

NOAEC: 9.9 mg/L

EC50: > 9.9 mg/L

47702510

(Supplemental)

IN-E9260

Sorghum/Oilseed 

Rape

NOAEC: 0.0244 lb/A

EC25: > 0.122 lb/A

47702506

(Supplemental)

Duckweed NOAEC: 3.7 mg/L

EC50: > 130 mg/L

47702511

(Supplemental)

Table 10. EcoSAR estimates of toxicity based on structure activity relationships. 

Degradate Structural Class Most Sensitive Estimated Endpoints

IN-70941 Substituted Ureas

Amides

Acute Fish: 15.5 ppm

Daphnid: 10.8 ppm

Green Algae: 0.214 ppm

Chronic Fish: 0.092 ppm

Daphnid: 0.143ppm

Green Algae: 0.052 ppm

 

6 EPISuite (Estimation Programs Interface Suite) version 4.1 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 that estimates physical chemical and environmental fate properties for 

mainly organic compounds. 

7 D200158, March 29, 1994.
20

IN-70942 Neutral Organics Acute Fish: 191.6 ppm

Daphnid: 110.2 ppm

Green Algae: 55.4 ppm

Chronic Fish: 20.1 ppm

Daphnid: 13.0 ppm

Green Algae: 21.6 ppm

IN-E9260 Amides Acute Fish: 6421.3 ppm

Daphnid: 1325.0 ppm

Green Algae: 3.6 ppm

Chronic Fish: 38.0 ppm

Daphnid: 17.5 ppm

Green Algae: 0.4 ppm

The data in Table 9 in combination with toxicity estimates from EpiSuite 4.1 structural activity 

relationships (SAR) in Table 10 indicate that the degradate IN-70941 has low acute toxicity to 

all organisms. Chronic exposure, however, presents a different picture for IN-70941. In some 

aquatic environments, IN-70941 can be relatively persistent. Furthermore, the estimated 

endpoints based on SARs show that fish and aquatic invertebrates may be sensitive to chronic 

exposure to the amide moiety where estimated toxicity endpoints are several orders of magnitude 

lower than acute endpoints. However, EFED does not anticipate requesting additional toxicity 

data on this degradate due to the levels of estimated toxicity relative to previously modeled peak 

EEC’s and the conservative assumption that all of the parent transforms into the IN-70941 

degradate. A recent risk assessment for soybean and corn (D358867+) that evaluated the 

maximum use rate revealed peak EEC’s for the parent ranging from 0.459 ppb up to 1.380 ppb. 

If the entire parent compound converted to equivalent concentrations of IN-70941, exposure 

would still be over an order of magnitude below the chronic toxicity endpoints for aquatic taxa 

based on the SAR estimates. 

In terms of aquatic vascular plants, the toxicity of IN-70941 from a laboratory study showed that

Lemna gibba has an EC50 of >11 ppm, which is several orders of magnitude greater than the 

EC50 for the parent rimsulfuron. Therefore, IN-70941 is less toxic to aquatic vascular plants than 

parent rimsulfuron. Considering that IN-70941 is a substituted urea, data for another related urea 

(diuron, PC035505) can also be used for comparison. The data for diuron indicates that nonvascular aquatic plants are more sensitive than vascular aquatic plants by a factor of five. The 

most sensitive non-vascular plant is Selenastrum capricornutum with an EC50 of 2.4 ppb, but 

Lemna has an EC50 of 15 ppb. Applying this same non-vascular to vascular ratio established by 

diuron to IN-70941, an estimate of the non-vascular EC50 would therefore be approximately 2.2 

ppm. Consequently, aquatic non-vascular plants are also much less sensitive to IN-70941 

compared to the parent rimsulfuron. 

Similarly, data for the degradate IN-70942 in Table 9 in conjunction with SAR toxicity 

estimates from Table 10 support the conclusion that this degradate is also less toxic to either 

terrestrial or aquatic organisms compared to parent rimsulfuron. In the case of freshwater 

invertebrates, IN-70942 appears to be more toxic than the parent compound, though the toxicity 

is relatively low compared to potential concentrations in the environment. In addition, this 

degradate was not identified to be of concern to mammals by HED. However, fate data show 
21

that this terminal degradate is persistent in the environment. While the current body of available 

literature indicates that this degradate appears to present a low potential for concern to terrestrial

and aquatic organisms due both to low toxicity to various taxa and low use rates of rimsulfuron, 

there is uncertainty as to how the persistence of this degradate may affect its fate in the aquatic 

environment over an extended period of time following multiple years of consecutive 

applications. 

As shown in Table 10, aquatic animal taxa do not appear to be sensitive to the degradate INE9260 based on estimated toxicity endpoints. The taxa of concern based on these estimated 

toxicity endpoints narrow the focus to plant taxa. Actual data on terrestrial plants indicate that 

IN-E9260 would not alter the risk picture from that obtained by the parent compound. As for 

aquatic plants, one study tested the effects of the degradate IN-E9260 on the growth and biomass 

of Lemna gibba. Biomass, yield based on dry weight, and growth rate based on dry weight were 

significantly reduced at the highest treatment level relative to the negative control. The 7-Day 

NOAEC and EC50 values for all three endpoints were 3.7 and >130 mg ai/L, respectively. This 

degradate evidently shows much less toxicity than the parent compound to aquatic vascular 

plants by several orders of magnitude. The estimated value based on SAR’s reveals that the nonvascular plants are more sensitive than aquatic vascular plants by an order of magnitude. 

Nonetheless, toxicity estimates for IN-E9260 reveal that it is much less toxic to aquatic plants 

than parent rimsulfuron.

In summary, the three major degradates in both the aquatic and terrestrial environments (IN70941, IN-70942, and IN-E9260) are less toxic to most taxa than the parent rimsulfuron. The 

exception is the potential toxicity to aquatic organisms due to chronic exposure to IN-70941. 

EFED does not anticipate requesting additional toxicity data on this degradate due to the levels 

of estimated toxicity relative to previously modeled peak EEC’s and the conservative assumption 

that all of the parent transforms into the IN-70941 degradate.

Incident Reports

Incident reports submitted to EPA since approximately 1994 have been tracked by assignment of 

“incident numbers” in an Incident Data System (IDS), microfiched, and then entered into a 

second database, the Ecological Incident Information System (EIIS, see Appendix 2; USEPA 

2007b). A preliminary review of the EIIS and the Avian Incident Monitoring System (AIMS), 

which is maintained by the American Bird Conservancy, indicates that there are no incidents for 

wildlife. Since rimsulfuron was first registered, there were 26 incidents reported in the EIIS that 

show incidents that involve plant damage where rimsulfuron was applied to agricultural crops 

(corn, soybean, and potato). The magnitude of damages described in the various incidents 

ranged from 6.5 acres of damage (possibly caused by rimsulfuron) to corn up to 1600 acres of 

soybean (misuse). Only 6 of the incidents of plant damage are considered probable or highly 

probable as caused by rimsulfuron, whereas 20 of the incidents are considered only possibly or 

unlikely resulting from exposure to rimsulfuron.

In addition to the incidents recorded in EIIS, additional incidents have been reported to the 

Agency in aggregated incident reports. Pesticide registrants report certain types of incidents to 
22

the Agency as aggregate counts of incidents occurring per product per quarter. Ecological 

incidents reported in aggregate reports include those categorized as “minor fish and wildlife” 

(W-B), “minor plant” (P-B), and “other nontarget” (ONT) incidents. “Other nontarget” incidents 

include reports of adverse effects to insects and other terrestrial invertebrates. For rimsulfuron, 

which was first registered in 2005, registrants have reported a total of 12 minor incidents, with 

seven incidents related to plants, one related to other nontargets, one related to wildlife, two 

related to domestic animals, and one related to human exposure. 

In the risk assessment, the incidents will be further evaluated to determine if the reported 

incidents represent current patterns of use for rimsulfuron. Examples of additional 

considerations are mitigation (e.g., reduced application rates), product cancellations, and changes 

in use patterns that have occurred since the date of the reported incidents.

An absence of reported incidents should not be construed as the absence of incidents. Incident 

reports for non-target organisms typically provide information only on mortality events and plant 

damage incidents. Except for phytotoxic effects in terrestrial plants, sublethal effects, such as 

reduced growth or impaired reproduction, are rarely reported. EPA’s changes in the registrant 

reporting requirements for incidents in 1998 may account for a reduced number of reported 

incidents. Registrants are now only required to submit detailed information on ‘major’ fish, 

wildlife, and plant incidents. Minor fish, wildlife, and plant incidents, as well as all other 

nontarget incidents, are generally reported aggregately and are not included in the EIIS. In 

addition, there have been changes in state monitoring efforts due to a lack of resources. 

However, the incident data that are available suggest that exposure pathways for rimsulfuron are 

complete and that exposure levels are sufficient to result in field-observable effects.

Ecosystems Potentially at Risk

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible 

to identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk could include 

the treated field and immediately adjacent areas that may receive drift or runoff. Areas adjacent 

to the treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow 

fields or grasslands, woodlands, riparian habitats, and other uncultivated areas. 

Aquatic ecosystems potentially at risk include water bodies adjacent to or downstream from the 

treated site and might include impounded bodies such as ponds, lakes and reservoirs, or flowing 

waterways such as streams or rivers including all adjacent off-channel habitats that are 

permanently or intermittently connected to flowing waters. For uses in coastal areas, aquatic 

habitat also includes marine ecosystems, including estuaries, embayments, and near shore 

environments.
23

Risk Hypothesis

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of 

exposure for ecological receptors, and a feasible route of exposure. 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For rimsulfuron, the 

following ecological risk hypothesis is being employed for this national-level ecological risk 

assessment:

Rimsulfuron is mobile in soil and toxic to plants and may pose a 

risk to terrestrial plants near the site of application. Rimsulfuron is

mobile and has been detected in aquatic systems. Therefore, 

rimsulfuron may also pose a risk to aquatic organisms. Toxicity 

studies suggest that this risk may be greatest to aquatic vascular

plants. 

The available data do not suggest that rimsulfuron is particularly 

toxic to aquatic or terrestrial animals. However, concentrations of 

the chemical in drinking water for birds and mammals may be of

concern due to the chemical’s high solubility. Finally, the 

chemical's persistence and effect on aquatic and terrestrial plants 

could affect primary productivity and, in turn, have secondary 

effects on the entire animal community.

Risk Hypothesis Description 

The environmental fate properties of rimsulfuron indicate that runoff, leaching, and spray drift 

represent potential transport mechanisms to aquatic and terrestrial organisms. The movement 

away from the site of application in turn represents exposure pathways for a broad range of 

biological receptors of concern (nontarget animals) and the potential attribute changes, i.e., 

effects such as reduced survival, growth and reproduction, in the receptors due to rimsulfuron 

exposure. Based on the nature of rimsulfuron applications which include aerial and ground 

application of rimsulfuron dispersible granules and solutions as well as rimsulfuron’s mobility in 

the environment, dietary and aquatic exposure from rimsulfuron applications will be assessed in 

the risk assessment. A preliminary evaluation is presented in this problem formulation on the 

applicability of rimsulfuron inhalation and drinking water exposure for terrestrial organisms to 

the risk assessment. Two models are used in this evaluation: SIP is used to address potential 
24

adverse effects from drinking water exposure and STIR is used to address the same for inhalation 

exposure. These models and results are described below.

Screening Imbibition Program (SIP)

The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to calculate an 

upper bound estimate of exposure using rimsulfuron’s solubility (7,300 mg/L), the most sensitive 

acute and chronic avian toxicity endpoint (>2,000 ppm; 1250 ppm, respectively) and the most 

sensitive acute and chronic mammalian toxicity endpoints (>5,000 and 165 mg/kg-bwt, 

respectively). Drinking water exposure alone was determined to be a potential pathway of 

concern for both mammalian and avian species on an acute and chronic basis for rimsulfuron. 

For a sample of the output generated by SIP v.1.0, please see Appendix 3. Detailed information 

about the SIP v.1.0, as well as the tool, can be found on the EPA’s website at 

http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial. While rimsulfuron exhibits 

low toxicity to avian and mammalian species, it is also highly soluble. This high degree of 

solubility translates into potentially high concentrations in water that animals may use as a 

source of drinking water. Yet use rates are very low, and so the likelihood of achieving the 

concentrations at the solubility limit is low. This pathway will be explored further in the 

Ecological Risk Assessment for rimsulfuron pending the development of SIP v.2.0.

Screening Tool for Inhalation Risk (STIR)

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate 

an upper bound estimate of exposure for rimsulfuron using the vapor pressure and molecular 

weight for vapor phase exposure as well as the maximum application rate and method of 

application for spray drift. STIR incorporates results from several toxicity studies including 

acute oral and inhalation rat toxicity endpoints obtained from the series of six guideline studies 

that are submitted to the Registration Division of the Office of Pesticide Programs for technical 

and formulated products of a pesticide (LD50 > 5,000 mg/kg and LC50 > 5.0 mg/L) as well as the 

most sensitive acute oral avian toxicity endpoint (Mallard duck with LD50 > 2,000 mg/kg). 

Based on the results of the STIR model, inhalation exposure alone was not determined to be a 

potential pathway of concern for either avian or mammalian species on an acute basis.

Inhalation exposure via spray drift and vapor-phase of the pesticide alone does not appear to be 

of concern. The analysis of the inhalation route in STIR does not consider that aggregation with 

other exposure pathways such as dietary, dermal, or drinking water may contribute to a total 

exposure that has a potential for effects to non-target animals. However, the Agency does 

consider the relative importance of other routes of exposure in situations where data indicate that 

pesticide exposures through other routes may be potentially significant contributors to wildlife 

risk (USEPA, 2004). The risk characterization section of the risk assessment will discuss the 

impact of consideration of other routes of exposure that have been identified as potentially 

important and the degree of certainty associated with screening-level risk assessment 

conclusions. Detailed information about STIR v.1.0, as well as the tool, can be found on the 

EPA’s website at: http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial. For a 

sample of the output generated by STIR v.1.0, please see Appendix 4.
25

Analysis Plan

In order to address the risk hypothesis, the potential for adverse effects on the environment is 

estimated. The use, environmental fate, and ecological effects of rimsulfuron are characterized 

and integrated to assess the potential for risks. This is accomplished using a risk quotient (ratio 

of exposure concentration to effects concentration) approach (Appendix 5). Although risk is 

often defined as the likelihood and magnitude of adverse ecological effects, the risk quotientbased approach does not provide a quantitative estimate of likelihood and/or magnitude of an 

adverse effect. However, as outlined in the Overview Document (USEPA 2004), the likelihood 

of effects to individual organisms from particular uses of rimsulfuron is estimated using the 

probit dose-response slope and either the level of concern (discussed below) or actual calculated 

risk quotient values.

This analysis plan will be revisited and may be revised depending upon the information 

submitted by the public in response to the opening of the Registration Review docket for 

rimsulfuron.

Stressors of Concern

Parent rimsulfuron and its three major degradates (IN-70941, IN-70942, and E9260) will be 

evaluated in the registration review risk assessment based on the potential for exposure in the

aquatic and terrestrial environments. The risk assessment will therefore address the potential risk 

related to the parent alone as well as any concerns related to these major degradates by taking 

into consideration both exposure as well as the available toxicity data.

While the current toxicity dataset shows that IN-70942 is of lower toxicity than the parent 

rimsulfuron to various taxa, it is worth noting that the IN-70942 degradate in particular can be 

persistent in the environment. Therefore, there is uncertainty as to the fate of IN-70942 in 

aquatic environments subject to run-off following multiple years of applications of rimsulfuron. 

This potential persistence of IN-70942 will be further examined in the registration review risk 

assessment, as well as any implications for the characterization of risks related to rimsulfuron 

use. 

An evaluation of environmental pesticide mixtures is beyond the scope of this assessment 

because of the myriad factors that cannot be quantified based on the available data. Those 

factors include identification of other possible co-contaminants and their concentrations, 

differences in the pattern and duration of exposure among contaminants, and the differential 

effects of other physical/chemical characteristics of the receiving waters (e.g. organic matter 

present in sediment and suspended water). Evaluation of factors that could influence 

additivity/synergism is beyond the scope of this assessment and the capabilities of the available 

data to allow for an evaluation. However, EFED acknowledges that not considering mixtures 

could over- or under-estimate risks depending on the type of interaction and factors discussed 

above. Given the limitations above, the final assessment will evaluate, characterize, and 

potentially make use of data available on combinations of active ingredients with rimsulfuron, 

inert products, or environmental mixtures.
26

Measures of Exposure

The measures of exposure will be estimated using models. Aquatic exposure for ecological 

effects will consist of aquatic EECs based on a total residue approach to include the parent 

rimsulfuron and the relevant degradates, as well as parent alone, and derived using a water body

that is vulnerable and representative of static ponds and first order waterways. Drinking water 

exposure will focus on the parent rimsulfuron alone. Terrestrial exposure will be estimated using 

a model that assumes direct application to a variety of avian, mammalian and reptilian food 

items. Exposure to terrestrial plants will be estimated using a model that assumes rimsulfuron 

drifts or moves with runoff to adjacent habitats. For more information on the various models 

that will be used in the risk assessment see the links as outlined in Table 11.

Table 11. List of the various models and the related taxa for which the models will be used.

Environment Concern Model Link

Aquatic

Fish/ 

Invertebrates

/Plants

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

water/

Human 

Health 

Drinking 

Water

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

water/first_v1_1_1_description.htm

SCI-GROW http://www.epa.gov/oppefed1/models/

water/scigrow_description.htm

Terrestrial

Animal

T-REX (dietary 

item/terrestrial 

invertebrate 

contact)

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

errestrial/index.htm

SIP v2.0 (drinking 

water) Pending development

Plant

TerrPlant (Run-off) http://www.epa.gov/oppefed1/models/t

errestrial/index.htm#terrplant

AgDRIFT (Spray 

drift)

http://www.agdrift.com/AgDRIFt2/Do

wnloadAgDrift2_0.htm

AGDISP (Spray 

drift)

http://www.continuumdynamics.com/pr-agdisp.html

Measures of Effect

Assessment endpoints represent the actual environmental value that is to be protected, defined by 

an ecological entity (species, community, or other entity) and its attribute or characteristics 

(USEPA, 1998). For rimsulfuron, the ecological entities may include the following: birds, 

mammals, terrestrial-phase amphibians, reptiles, freshwater fish and invertebrates, aquatic-phase 

amphibians, estuarine/marine fish and invertebrates, terrestrial plants, terrestrial invertebrates, 

and aquatic plants. The attributes for each of these entities include growth, reproduction, and 

survival.
27

Acute and chronic toxicity data from studies submitted by pesticide registrants along with the 

available open literature are used to evaluate the potential direct and indirect effects of 

rimsulfuron on aquatic and terrestrial receptors. This includes toxicity data on the technical 

grade active ingredient, degradates, and when available, formulated products. The open 

literature studies are identified using EPA’s ECOTOX database (USEPA 2007a), which employs 

a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, 

and wildlife. ECOTOX is a source for locating single chemical toxicity data and potential 

chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife. ECOTOX was 

created and is maintained by the USEPA, Office of Research and Development, and the National 

Health and Environmental Effects Research Laboratory's Mid-Continent Ecology Division. The 

evaluation of both sources of data can also provide insight into the direct and indirect effects of 

rimsulfuron on biotic communities from loss of species that are sensitive to the chemical and 

from changes in structure and functional characteristics of the affected communities. Where 

available, sublethal effects observed in both registrant-submitted and open literature studies will 

be evaluated qualitatively. Such effects have included behavioral changes (e.g., lethargy, 

changes in coloration and effects olfaction). Quantitative assessments of risks, though, are 

limited to those endpoints that can be directly linked to the Agency’s assessment endpoints of 

impaired survival, growth and reproduction. An updated report of the available studies 

contained within the ECOTOX database will be used for the final risk assessment, and the 

studies will be evaluated according to guidance established for open literature studies (USEPA, 

2011b). In the absence of data for either acute or chronic effects, the conservative assumption 

will be to presume that rimsulfuron is toxic.

Consistent with the process described in the Overview Document (USEPA, 2004), the Agency 

has routinely relied on a surrogate species approach. Toxicological data generated from 

surrogate test species, which are intended to be representative of broad taxonomic groups, have 

been used to extrapolate the potential effects on a variety of species (receptors) included under 

these taxonomic groups. For example, guideline data for freshwater fish have typically served as 

surrogates for aquatic-phase amphibians and submitted studies for birds have served as 

surrogates for terrestrial-phase amphibians and reptiles. For the purposes of Registration 

Review, the Agency will consider the best available data in an effort to provide additional 

refined endpoints for specified taxonomic groups for which guideline data on surrogate species 

are typically not available and large numbers of listed species occur. These taxa include aquaticphase and terrestrial-phase amphibians, freshwater mollusks, and reptiles. Based on an updated 

ECOTOX search, which will be conducted as part of the Registration Review preliminary risk 

assessment, EPA will consider both more and less sensitive endpoints for amphibians, freshwater 

mollusks, and reptiles, as compared to the registrant-submitted data for surrogate species (i.e., 

freshwater fish are surrogates for aquatic-phase amphibians, freshwater invertebrates are 

surrogates for freshwater mollusks, and birds are surrogates for terrestrial-phase amphibians and 

reptiles) In situations where no additional open literature data are available to refine endpoints 

for amphibians, freshwater mollusks, and reptiles, the Agency will rely on registrant-submitted 

data and open literature for surrogate test species, as specified above.
28

Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the 

Agency will evaluate risks to Federally-listed threatened and/or endangered species from 

registered uses of rimsulfuron. This assessment will be conducted in accordance with the 

Overview Document (USEPA 2004), provisions of the ESA, and the Services’ Endangered 

Species Consultation Handbook (USFWS/NMFS 1998). 

The assessment of effects associated with registrations of rimsulfuron is based on an action area. 

The action area is considered to be the area directly or indirectly affected by the federal action, as 

indicated by the exceedance of Agency Levels of Concern (LOCs) used to evaluate direct or 

indirect effects. The Agency’s approach to defining the action area under the provisions of the 

Overview Document (USEPA 2004) considers the results of the risk assessment process to 

establish boundaries for that action area with the understanding that exposures below the 

Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this assessment, 

attention will be focused on the footprint of the action (i.e., the area where rimsulfuron 

application occurs), plus all areas where offsite transport (i.e., spray drift, runoff, etc.) may result 

in potential exposure that exceeds the Agency’s LOCs. Specific measures of ecological effect 

that define the action area for listed species include any direct and indirect effects and/or 

potential modification of its critical habitat, including reduction in survival, growth, and 

reproduction as well as the full suite of sublethal effects available in the effects literature. 

Therefore, the action area extends to a point where environmental exposures are below any 

measured lethal or sublethal effect threshold for any biological entity at the whole organism, 

organ, tissue, and cellular level of organization. In situations where it is not possible to 

determine the threshold for an observed effect, the action area is not spatially limited and is 

assumed to be the entire United States. 

Preliminary Identification of Data Gaps

Table 12 and Table 13 identify environmental fate and eco-toxicological studies, respectively,

that offer data for each guideline requirement, as well as study classifications and whether or not 

further data are needed in order to support the risk assessment.

Environmental Fate

Table 12 lists the status of the fate and transport data requirements for rimsulfuron. The 

adequacy of the submitted data was evaluated relative to Agency guidelines. 
29

Table 12. Environmental fate data requirements for rimsulfuron and remaining data gaps.

Guideline 

Number

Data Requirement MRID Study 

Classification

Are more data needed?

830.7950 Vapor Pressure 41356301 Acceptable No

161-1 835.2120 Hydrolysis 41356333 Acceptable No

161-2 835.2240 Photodegradation in 

Water 

41931608 Acceptable No

161-3 835.2410 Photodegradation on 

Soil 

41931609 Acceptable No

162-1 835.4100 Aerobic Soil 

Metabolism 

41356334

48332003

Acceptable

In Review

No (for first study)

TBD

162-2 835.4200 Anaerobic Soil 

Metabolism 

41356335 Acceptable No

162-4 835.4300 Aerobic Aquatic 

Metabolism

43288502

45490802

Supplemental

In Review TBD

162-3 835.4200 Anaerobic Aquatic 

Metabolism

48332004 In Review TBD

163-1 835.1240 Adsorption/Desorption 413563-36 Acceptable No

164-1 835.6100 Terrestrial Field 

Dissipation

419316-06

419316-10 Acceptable No

165-4 850.1730 Fish Bioconcentration No Study 

Submitted

- No
30

Guideline 

Number

Data Requirement MRID Study 

Classification

Are more data needed?

164-1 835.6100

(supporti

ng data)

Environmental 

Chemistry Methods in 

soil and water

41821701 

43406701 

43023101 

43023102 

43023103 

43023104 

43601701

Supplemental MRID #43023101 method 

for soil has been 

published at 

http://www.epa.gov/pestic

ides/methods/ecmp2r.htm

#R.

Yes, for rimsulfuron and 

data on the IN-70941, 

70942 and E-9260 

degradates

164-1 835.6100

(supporti

ng data)

Independent 

Laboratory Validation 

(ILV) 

No study 

has been 

submitted

- Yes, for rimsulfuron and 

data on the IN-70941, 

70942, and E-9260 

degradates

Environmental Fate Data Gaps

The Agency has completed a review of all available data submitted by the registrant. Two studies 

that have previously been requested (see Rimsulfuron Ecological Risk Assessment dated 

8/4/2009, DP Barcode D358867; page 5) are scientifically valid but additional data are still 

required:

Aerobic aquatic metabolism (OPPTS guideline # 835.4300) – A study has been 

submitted in response to a previously identified data gap and is currently under review. 

The data requirement will be considered unfulfilled until the study is fully reviewed and 

found either acceptable or supplemental.

Anaerobic aquatic metabolism (OPPTS guideline # 835.4400) – A study has been 

submitted that is scientifically valid but additional characterization of secondary 

metabolites is requested. 

Non-Guideline Study: Environmental Chemistry Methods(ECMs)/Independent Laboratory 

Validation(ILV): Rimsulfuron and Major Degradates

State of the art ECMs for trace residues in soil and water and ILVs are requested for rimsulfuron 

and its IN-70941, 70942, and E-9260 degradates. Environmental chemistry methods for soil and 

water are only available for parent rimsulfuron. In addition, no ILVs have been submitted to the 

Agency. Therefore, ECMs should be submitted and ILVs should be conducted for parent 

rimsulfuron studies in water and soil. The ECMs and ILVs should also include information and 

investigate the degradates IN-70941 and IN-70942 in both soil and water.
31

Ecological Effects Data

For the ecological assessment, Table 13 lists the status of ecological data requirements for 

rimsulfuron. The following table presents a summary of identified data gaps and associated 

uncertainties. 

Table 13. Ecological effects data requirements for rimsulfuron and remaining data gaps.

Guideline 

#

Data 

Requirement

Test 

Substance

MRID # or 

Citation Study 

Classification Is More Data Needed?

850.2100 Avian Oral LD50

98.8%

25% (TEP)

98.8%

25% (TEP)

41356304

41931629

41931630

41931631

Acceptable

Acceptable

Acceptable

Supplemental

No, a study is required for 

avian passerine species 

based on the 40CFR part 

158 guidelines. However, 

no mortality or sublethal 

effects were found in any 

of the avian toxicity 

studies at any 

concentration when tested 

with the TGAI. A study 

on passerines with the 

TGAI is not needed for the 

risk assessment given the 

lack of toxicity. 

850.2200 Avian Dietary 

LC50

98.8%

98.8%

25% (TEP)

25% (TEP)

41356305

41356306

41931632

41931633

Acceptable

Acceptable 

Supplemental

Supplemental

No

850.2300 Avian 

Reproduction 99% 43277201 Acceptable

No; only one study was 

submitted on Bobwhite 

quail even though two are 

required by the 40CFR 

part 158 guidelines. 

However, rimsulfuron 

does not appear to be toxic 

to avian species on either 

an acute or chronic basis, 

therefore this study would 

add little information to 

the risk assessment.

850.1075 Freshwater Fish 

Acute LC50

98.8%

41356307

41356308

41931620

Acceptable

Acceptable

In Review

No
32

Guideline 

#

Data 

Requirement

Test 

Substance

MRID # or 

Citation Study 

Classification Is More Data Needed?

850.1010

Freshwater 

Invertebrate 

Acute LC50

98.8% 41356309

41931621

Acceptable 

Supplemental No

850.1075 Estuarine/Marine 

Fish Acute LC50

99% 42471303 Acceptable No

850.1025

Estuarine/Marine 

Mollusk Acute 

EC50

99% 42471301 Acceptable No

850.1035

850.1045

850.1055

Estuarine/Marine 

Shrimp Acute 

EC50

99% 42471302 Acceptable No

850.1400 Freshwater Fish 

Early Life-Stage

25% (TEP)

99%

98.8%

43472703

43472704

43472705

In Review

Yes, data have been 

submitted but are in 

review. Request of 

additional data will be 

pending the outcome of 

the formal review of these 

studies.

850.1400

Estuarine/Marine 

Fish Early LifeStage

No Data Submitted

Yes, the exposure pathway 

is complete for saltwater 

fish. This toxicity study 

may be waived pending 

the review of freshwater 

fish ELS data.

850.1300

Aquatic 

Invertebrate LifeCycle 

(freshwater)

98.8%

25% (TEP)

43472701

43472702 In Review

Yes, data have been 

submitted but are in 

review. Request of 

additional data will be 

pending the outcome of 

the formal review of these 

studies.

850.1350 Aquatic 

Invertebrate LifeCycle (marine)

No Data Submitted

Yes, the exposure pathway 

is complete for saltwater 

invertebrates. This

toxicity study may be 

waived pending the review 

of freshwater invertebrate 

lifecycle data.
33

Guideline 

#

Data 

Requirement

Test 

Substance

MRID # or 

Citation Study 

Classification Is More Data Needed?

850.1500 Fish Full LifeCycle No Data Submitted

No, there is no information 

to indicate that 

rimsulfuron or any of its 

degradates will be toxic 

enough on a chronic basis 

to trigger the request 

specifically for a fish full 

life-cycle study 

850.4100

Seedling 

Emergence (Tier 

I)

98.8% TGAI

98.1% TGAI

42471304

43539201

Supplemental 

(tomato) No 

850.4100

Seedling 

Emergence (Tier 

II)

98.8% TGAI

98.1% TGAI

42471304

43539201

Supplemental

(rape, onion, 

sugar beet, 

wheat, 

soybean, 

sorghum, pea, 

cucumber)

Yes, these studies used the 

TGAI. However, the use 

of a TEP is required. In 

addition, NOAEL values 

were not determined for 

the most sensitive species. 

Tier II seedling emergence 

studies should be 

conducted for 6 dicots and 

4 monocots with a TEP. 

850.4150 Vegetative Vigor 

(Tier II)

98.8% TGAI

98.1% TGAI

42471304

43539201

Supplemental 

(soybean, rape, 

sugarbeet,

onion, wheat, 

sorghum, 

tomato, 

cucumber, pea)

Yes, these studies used the 

TGAI. However, the use 

of a TEP is required. In 

addition, NOAEL values 

were not determined for 

the most sensitive species. 

Tier II vegetative vigor 

studies should be 

conducted for 6 dicots and 

4 monocots with a TEP. 

Nonguideline

Terrestrial Plant 

reproduction 

toxicity

No Data Submitted Noa

850.4400

Aquatic Plant 

Growth: Vascular

(Tier II)

98.57% 42471308 Acceptable No
34

Guideline 

#

Data 

Requirement

Test 

Substance

MRID # or 

Citation Study 

Classification Is More Data Needed?

850.5400

Aquatic Plant 

Growth: NonVascular

(Tier I)

98.57%

98.57%

98.57%

98.8%

42471305

42471306

42471307

43043601

Acceptable

Acceptable

Acceptable

Acceptable

No, the studies provide 

NOAEC values, and the 

non-definitive EC50 values 

are an order of magnitude 

greater than previously 

modeled EECs. However, 

if use rates increase then 

the need for non-vascular 

aquatic plants will be reevaluated.

850.3020 Honey Bee Acute

Contact LD50

98.8% 41356331 Acceptable No

870.1100 Acute Oral 

Toxicity to Rat

25% (TEP)

98.8%

25% (TEP)

25.7% (TEP)

41356311 

41356310 

41931634

47091007 

Acceptable

Acceptable

Acceptable

Acceptable

No

870.1300 Acute Inhalation 

Toxicity to Rat

98.8%

26.5% (TEP)

25% (TEP)

98.6%

41356314 

41931625 

41931637 

41931636 

Acceptable

Acceptable

Acceptable

Acceptable

No

870.3800

Mammalian 

Reproduction --

Rat

98.8% 41931644 Acceptable No

aEFED's Plant Technical Team (PTT) conducted an analysis of available SU plant reproduction data from the open 

literature and the registrant-submitted data for chlorsulfuron and concluded that data from the 850.4150 vegetative 

vigor guideline study are sufficiently protective of potential impacts to plant reproduction. Acetolactate synthase 

(ALS) inhibitors primarily affect metabolically-active meristem tissues. When plants are exposed at a young, 

vigorously growing life-stage, effects are expressed primarily as inhibition of vegetative growth (i.e. biomass, 

shoot length). As plants mature these effects are less pronounced. However, as plants enter their reproductive 

life-stage, the metabolically-active tissue will include flower and seed production. Plants exposed to SU

herbicides during the reproductive life stage are likely to exhibit adverse effects on reproduction, generally 

expressed as reduced seed number or reduced seed weight. Based on the latest data analysis, these effects are 

expected to occur at similar concentrations to those effects determined in the guideline vegetative vigor studies 

(850.4150) so further data are not requested at this time.

References

USDA, 2006-2010. NASS Crop Reporting Districts. Online: 

http://www.ers.usda.gov/briefing/arms/resourceregions/resourceregions.htm#nass.
35

USDA, 2007. Census of Agriculture. Online:

http://www.agcensus.usda.gov/Publications/2007/index.asp

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of 

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004.

USEPA. 2007a. Ecotoxicology (ECOTOX) database. Version 4. Office of Research and 

Development (ORD) , and the National Health and Environmental Effects Research 

Laboratory's (NHEERL's) Mid-Continent Ecology Division (MED). 

http://cfpub.epa.gov/ecotox/ecotox_home.cfm

USEPA. 2007b. Ecological Incident Information System (EIIS). Environmental Fate and 

Effects Division.

USEPA. 2007c. 40 CFR Part 158. Pesticides; Data Requirements for Conventional Chemicals: 

Final Rule. 72 FR 60934. October 26, 2007.

USEPA. 2011a. Screening Level Estimates of Agricultural Uses on Rimsulfuron. Biological 

and Economic Assessment Division, Office of Pesticide Programs. Dated October 31, 

2011.

USEPA. 2011b. Guidance for the evaluation of open literature. U.S. Environmental Protection 

Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs, Washington DC. May 16, 2011.

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation 

and Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. 

March 1998.
36

APPENDIX 1. Submitted Environmental Fate and Effects 

Studies

SUBMITTED FATE STUDIES:

9/8/11

161-1 Hydrolysis

MRID Citation Reference

41356333 Horne, P.; Boucher, C. (1989) Hydrolysis of [Pyridine-2-Cardon 14] DPXE9636 and [Pyrimidine-2-Carbon 14]DPX-E9636 in Buffer Solu- tions of 5, 7, 

and 9: Lab Project Number: AMR-1221-88. Unpub- lished study prepared by 

E. I. du Pont de Nemours & Co., Inc. 46 p. 

161-2 Photodegradation-water

MRID Citation Reference

41931608 Horne, P.; Boucher, C. (1989) Photodegradation of ?Pyridine-2-14C| DPX-E9636 

and ?Pyrimidine-2-14C| in Water(Conducted in Sunlight) : Lab Project Number: 

AMR-1220-88. Unpublished study prepared by E. I. du Pont de Nemours and Co. 

59 p. 

Naidu, M.V. 1993. Response to EFQB CamMts. Submitted by du Pcnt at the 

request of EFGWB reviewer Nov. 18, 1993

161-3 Photodegradation-soil

MRID Citation Reference

41931609 Brown, A.; Young, G. (1989) Photodegradation of ?Pyridine-2-14C|DPX -E9636 

and ?Pyrimidine-2-14C|DPX-E9636 on Soil: Lab Project Num- ber: AMR-1219-

88. Unpublished study prepared by E. I du Pont de Nemours and Co. 54 p. 

Naidu, M.V. 1993. Additional infonmtion requested by m during the

review process of the 162-3 study. Suhitted t a letter f m D. Drane,

du Pont ; 11/16/93

162-1 Aerobic soil metabolism

MRID Citation Reference

41356334 Naidu, M. (1989) Aerobic Soil Metabolism of [Pyridine-2-carbon 14] DPXE9636 and [Pyrimidine-2-carbon 14]DPX-E9636: Lab Project Number: AMR1218-88. Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc. 

49 p. 

45490802 Trabue, S.; Lydick, T. (2001) Degradation of Rimsulfuron in Two Water 
37

Sediment Systems: Lab Project Number: DUPONT-3980: 3980. Unpublished 

study prepared by E.I. du Pont de Nemours and Company. 97 p. 

162-2 Anaerobic soil metabolism

MRID Citation Reference

41356335 Naidu, M.; Fogiel, A. (1989) Anaerobic Soil Metabolism of [Pyri- dine-2-carbon 

14]DPX-E9636 and [Pyrimidine-2-carbon 14]DPX-E9636 Laboratory Project 

Number: AMR-1217-88. Unpublished study pre- pared by E. I. du Pont de 

Nemours and Co., Inc. 53 p. 

162-4 Aerobic aquatic metab.

MRID Citation Reference

43288502 Naidu, M. (1991) Aerobic Aquatic Metabolism of (Pyridine-2-(carbon 14)) DPXE9636 and (Pyrimidin-2-(carbon 14)) DPX-E9636: Lab Project Number: 

AMR/1407/89. Unpublished study prepared by E.I. du Pont de Nemours and Co. 

76 p. 

163-1 Leach/adsorp/desorption

MRID Citation Reference

41356336 Naidu, M. (1989) Batch Equilibrium (Adsorption/Desorption) Studies of DPXE9636: Lab Project Number: AMR-1204-88. Unpublished study prepared by E. I. 

du Pont de Nemours & Co., Inc. 38 p. 

41356337 Naidu, M.; Fogiel, A. (1989) Soil Mobility of DPX-E9636 and Its Soil 

Degradates by Soil TLC: Lab Project Number: AMR-1327-88. Unpublished 

study prepared by E. I. du Pont de Nemours & Co., Inc. 21 p. 

44448101 Warren, R. (1997) Monitoring for Rimsulfuron in Leachate from Field 

Lysimeters Treated with Basis Herbicide: Lab Project Number: AMR 3417-95: 

008-017. Unpublished study prepared by E.I. du Pont de Nemours and Co., 

Lancaster Labs. and Centre Analytical Labs., Inc. 86 p. 

164-1 Terrestrial field dissipation

MRID Citation Reference

41931606 Naidu, M. (1991) Field Soil Dissipation Study of ?Pyridine-2-14C| DPX-E9636 

and ?Pyrimidine-2-14C|DPX-E9636: Lab Project Number: AMR-1451-89. 

Unpublished study prepared by E. I du Pont de Nem- ours and Co. 142 p. 

41931610 Naidu, M. (1990) Field Soil Dissipation Study of ?Pyridine-2-14C| DPX-E9636 

and ?Pyrimidine-14C|DPX-E9636 at Newark, Delaware: Lab Project Number: 

AMR-1225-88. Unpublished study prepared by E. I du Pont de Nemours and Co. 

51 p. 
38

Review of rimsulfuron field dissipation and column lysimeter study

protocols

165-1 Confined rotational crop

MRID Citation Reference

41356338 Schneiders, G. (1989) Confined Accumulation Study of DPX-E9636 on 

Rotational Crops: Lab Project Number: AMR-1187-88. Unpublish- ed study 

prepared by E. I. du Pont de Nemours and Co., Inc. 60 p. 

41931607 Schneiders, G. (1989) Confined Accumulation Study of DPX-E9636 on 

Rotational Crops: Lab Project Number: AMR-1187-88. Unpublished study 

prepared by E. I. du Pont de Nemours and Co. 63 p. 

165-4 Bioaccumulation in fish

MRID Citation Reference

41356339 Lee, P. (1989) Fish Accumulation Potential for DPX-E9636: Lab Pro- ject 

Number: AMR-1561-89. Unpublished study prepared by E. I. du Pont de 

Nemours & Co., Inc. 13 p. 

ECM Methods

41821701 Proksch, L.R. and M.P, Wadsley (1989) Residue Method for Extraction and 

HPLC Analysis of Harmony Herbicide from Soil Matrices. Performed and 

Submitted by Du Pont. AMR-1550-89. Completed 11/17/89 and Reformatted 

3/18/91.

43406701 Batelle (1988) (Columbus, OH) Method for the Determination of Chlorsulfuron, 

DPX-A7881, DPX-L5300, DPX-M6316 and Metsulfuron Methyl in 

Groundwater. Du Pont Report 1335-88. Completed 11/21/88, Revised 6/21/91.

43023101 Amoo, J. (1993) Analytical Method for the Quantitation of DPX-E9636 in Soil by 

Liquid Chromatography: Lab Project Number: AMR 2231-91. Unpublished study 

prepared by E.I. du Pont de Nemours and Co., DuPont Agricultural Products. 68 

p. 

43023102 Shalaby, L.; Bramble, F. (1990) Thermospray LC/MS Analytical Method for the 

Quantitation of DPX-79406 and Metabolites in Soil: Lab Project Number: AMR1509-89. Unpublished study prepared by E.I. du Pont de Nemours and Co., 

DuPont Agricultural Products. 35 p. 

43023103 Zahnow, E.; Orescan, D. (1991) Analytical Method for the Determination of 

E9636 and V9360 in Water by HPLC: Lab Project Number: AMR-2186-91. 

Unpublished study prepared by E.I. du Pont de Nemours and Co., DuPont 

Agricultural Products. 20 p. 

43023104 Zahnow, E.; Orescan, D. (1992) Analytical Method for the Determination of 

E9636 in Water by HPLC: Lab Project Number: AMR 2210-91. Unpublished 

study prepared by E.I. du Pont de Nemours and Co., DuPont Agricultural 

Products. 20 p. 
39

43601701 Validation of Immunoassay Methods (Soil; Water)

Du Pont Report No. AMR 2438-92, "An Enzyme-Linked

Immunoassay (ELISA) Method for .the Determination of

Residues of Sulfonylureas in Water and Soilff (.-#43601701) 

Non Guideline Selections

43288503 Naidu, M. (1991) DPX-E9636 Environmental Fate and Residue Monograph: Lab 

Project Number: AMR/2131/91. Unpublished study prepared by E.I. du Pont de 

Nemours and Co. 32 p. 

43396501 Russel, M. (1994) Estimated Environmental Concentrations of Rimsulfuron and

Competitive Corn Herbicides in Ground Water and Surface Water in the USA: 

Lab Project Number: 423/09/05: 3064/94. Unpublished study prepared by 

Blasland, Bouck & Lee, Inc. 45 p. 

44186701 McCooey, K. (1996) Magnitude of Residues of Rimsulfuron in Soil Following 

Application of DPX-E9636 at Maximum Label Rates: Lab Project Number: AMR 

3404-95. Unpublished study prepared by Dupont Agricultural Products. 197 p. 

47702504 Leva, S.; Rardon, P. (2001) Summary of Herbicide Screening Data for Major 

Metabolites of Rimsulfuron. Project Number: DUPONT/6787. Unpublished study 

prepared by E.I. du Pont de Nemours and Company. 13 p.

48106102 LeNoir, J. (2003) South Dakota Surface Water Monitoring of Sullfonylureas, 

Summer 2003. Project Number: DUPONT/13166, ML03/1080/DUP. 

Unpublished study prepared by Morse Laboratories, Inc. 145 p.

43288501 Naidu, M.V. and Hershberger (1992) Environmental and Toxicological 

Assessment of DPX-E9636 Metabolites. Performed by E.I. du Pont de Nemours 

and Comp-any, Du Pont Agricultural Products, Wilmington, DE Laboratory 

Project ID AMR 2268-91, Completed 1/21/92.

43406702 Ibid. Supplement to Report. Performed by Batelle, Frankfurt.

1994 Fate Database Oneliner report
40

SUBMITTED EFFECTS STUDIES:

Revised August 16, 2011

71-1 Avian Single Dose Oral Toxicity

MRID Citation Reference

41356304 Grimes, J.; Jaber, M. (1988) An Acute Oral Toxicity Study with the Bobwhite: H 

# 17,463: Final Report: Lab Project Number: 112-208; 797-88. Unpublished 

study prepared by Wildlife International Ltd. 19 p. 

41931629 Culotta, J.; Campbell, S.; Hoxter, K.; et al. (1990) An Acute Oral Toxicity Study 

with the Mallard: H #18,231: Lab Project Number: 112-239: 363-90. 

Unpublished study prepared by Wildlife Inter- national Ltd. 18 p. 

41931630 Culotta, J.; Campbell, S.; Hoxter, K.; et al. (1990) An Acute Oral Toxicity Study 

with the Mallard: H #17,463: Lab Project Number: 12-232: 411-90. Unpublished 

study prepared by Wildlife Interna- tional Ltd. 18 p. 

41931631 Culotta, J.; Hoxter, K.; Smith, G. (1990) An Acute Oral Toxicity Study with the 

Northern Bobwhite: H #18,231: Lab Project Number: 112-238: 364-90. 

Unpublished study prepared by Wildlife Inter- national Ltd. 18 p. 

71-2 Avian Dietary Toxicity

MRID Citation Reference

41356305 Grimes, J.; Jaber, M. (1989) A Dietary LC50 Study with the Bobwhite H 

#17,463: Lab Project Number: 112-206. Unpublished study prepared by Wildlife 

International Ltd. 27 p. 

41356306 Grimes, J.; Jaber, M. (1989) A Dietary LC50 Study with the Mallard: H # 17,463: 

Lab Project Number: 112-207: 17-89. Unpublished study prepared by Wildlife 

International Ltd. 27 p. 

41931632 Driscoll, C.; Foster, J.; Hoxter, K. et al. (1990) A Dietary LC50 Study with the 

Northern Bobwhite: H #18,231: Lab Project Number: 112-236: 487-90. 

Unpublished study prepared by Wildlife Inter- national Ltd. 25 p. 

41931633 Driscoll, C.; Foster, J.; Hoxter, K. et al. (1990) A Dietary LC50 Study with the 

Mallard: H #18,231: Lab Project Number: 112-237: 486-90. Unpublished study 

prepared by Wildlife International Ltd. 27 p. 

71-4 Avian Reproduction

MRID Citation Reference

42835801 Beavers, J.; Trumbull, S.; Grimes, J.; et al. (1993) H-17,463: A Pilot 

Reproduction Study with the Northern Bobwhite (Colinus virginianus): Lab 

Project Number: 112-336: 428-93. Unpublished study prepared by Wildlife 

International, Ltd. 69 p. 

43277201 Beavers, J.; Foster, J.; Mitchell, L. et al. (1994) H-17,463 (Rimsulfuron): A OneGeneration Reproduction Study with the Northern Bobwhite (Colinus 

virginianus): Lab Project Number: 112/337: 257/94: HLO/257/94. Unpublished 
41

study prepared by Wildlife International, Ltd. 246 p. 

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

41356307 Hutton, D. (1989) Static Acute 96-Hour LC50 of DPX-E9636-22 to 

Rainbow Trout (Salmo gairdneri): Lab Project Number: 351-89: 4581-660. 

Unpublished study prepared by E. I. du Pont de Ne- mours and Co., Inc., 

Haskell Laboratory for Toxicology and Industrial Medicine. 18 p. 

41356308 Hutton, D. (1989) Static Acute 96-Hour LC50 of DPX-E9636-22 to Bluegill 

Sunfish (Lepomis macrochirus): Lab Project Number: 352- 89: 4581-660. 

Unpublished study prepared by E. I. du Pont de Nemours and Co., Inc., 

Haskell Laboratory for Toxicology and Industrial Medicine. 18 p. 

41931620 Hutton, D. (1989) Static Acute 96-Hour LC50 of DPX-E936-22 to Blue- gill 

Sunfish (Lepomis macrochirus): Lab Project Number: 4581-660 : 352-89. 

Unpublished study prepared by E. I. du Pont de Nemou- rs and Co. 18 p. 

43472706 Baer, K. (1991) Static, Acute, 96-Hour LC50 of IN E9636-37 to Rainbow 

Trout (Oncorhynchus mykiss): Lab Project Number: MR-4581-794: 710-90: 

HLR 710-90. Unpublished study prepared by DuPont Haskell Lab for 

Toxicology and Industrial Medicine. 20 p. 

47702502 Kreamer, G. (1993) Static, Acute, 96-Hour LC50 of IN-70942-4 to Rainbow 

Trout, Oncorhynchus mykiss. Project Number: 9581/042, 85/93. 

Unpublished study prepared by E.I. du Pont de Nemours and Company. 27 

p. IN-70942-4 = Dual active mixture 129002+629009

72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

41356309 Hutton, D. (1989) Static Acute 48-Hour EC50 of DPX-E9636-22 to Daphnia 

magna: Lab Project Number: 350-89: 4581-660. Unpub- lished study prepared by 

E. I. du Pont de Nemours and Co., Inc., Haskell Laboratory for Toxicology and 

Industrial Medicine. 18 p. 

41931621 Baer, K. (1990) Static Acute 48-Hour EC50 of IN E9636-22 to Fed Daphnia 

magna: Lab Project Number: 26-90: MR-4581-677. Unpubli- shed study prepared 

by E. I. du Pont de Nemours and Co. 13 p. 

47702505 Pierson, K. (1991) Static, Acute, 48-Hour EC50 of IN 70942-2 to Daphnia 

magna. Project Number: 113/91, MR/4581/839, 18404. Unpublished study 

prepared by E.I. du Pont de Nemours and Company. 19 p.

72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

42471301 Graves, W. ; Swigert, J. (1992) DPX-E9636-22: A 96-Hour Shell Deposition Test 
42

with the Eastern Oyster (Crassostrea virginica): Lab Project Number: 112A-104: 

542-92. Unpublished study prepared by Wildlife International Ltd. 34 p. 

42471302 Graves, W.; Swigert, J. (1992) DPX-E9636-22: A 96-Hour Flow-Through Acute 

Toxicity Test with the Salt Water Mysid (Mysidopsis bahia): Lab Project 

Number: 112A-105: 544-92. Unpublished study prepared by Wildlife 

International Ltd. 32 p. 

42471303 Graves, W.; Swigert, J. (1992) DPX-E9639-22: A 96-Hour Flow-Through Acute 

Toxicity Test with the Sheepsheed Minnow (Cyprinodon variegatus): Lab Project 

Number: 112A-103: 543-92. Unpublished study prepared by Wildlife 

International Ltd. 32 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

43472701 Baer, K. (1990) Chronic Toxicity of IN E9636-22 to Daphnia magna: Revision 

No. 1: Lab Project Number: 95-90: MR-4581-677: HLR 95-90. Unpublished 

study prepared by DuPont Haskell Lab for Toxicology and Industrial Medicine. 

423 p. 

43472702 Baer, K. (1991) Chronic Toxicity of IN E9636-37 to Daphnia magna: Lab Project 

Number: 134-91: MR-4581-794: HLR 134-91. Unpublished study prepared by 

DuPont Haskell Lab for Toxicology and Industrial Medicine. 54 p. 

43472703 Baer, K. (1991) Flow-through, 21-Day Toxicity of DPX-E9636-40 (25DF) to 

Rainbow Trout (Oncorhynchus mykiss): Revision No. 1: Lab Project Number: 

135-91: MR-4581-869: HLR 135-91. Unpublished study prepared by DuPont 

Haskell Lab for Toxicology and Industrial Medicine. 32 p. 

43472704 Kreamer, G. (1994) Early Life-stage Toxicity of DPX-E9636-22 (Rimsulfuron) 

with Rainbow Trout, Oncorhynchus mykiss: Lab Project Number: 9895-001: 

HLR 507-94: 507-94. Unpublished study prepared by DuPont Haskell Lab for 

Toxicology and Industrial Medicine. 515 p. 

43472705 Hutton, D. (1991) Flow-through, 21-Day Toxicity of DPX-E9636-22 to Rainbow 

Trout, Oncorhynchus mykiss: Revision No. 1: Lab Project Number: MR-4581-

848: 672-91: HLR 672-91. Unpublished study prepared by DuPont Haskell Lab 

for Toxicology and Industrial Medicine. 37 p. 

45490801 Samel, A. (2001) IN-JF999: 21-Day Chronic, Static-Renewal Toxicity to Daphnia 

magna: Lab Project Number: 13694: 254: DUPONT-6024. Unpublished study 

prepared by E.I. du Pont de Nemours and Company. 61 p. {OPPTS 850.1300} 

122-1 Seed Germination/Seedline Emergence and Vegetable Vigor

MRID Citation Reference

42471304 McKelvey, R; Kuratle, H. (1992) Infuence of Rimsulfuron on Seed Germination, 

Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab 

Project Number: AMR 2074-91. Unpublished study prepared by E. I. du Pont de 

Nemours and Co. 230 p. 

42471308 Hoberg, J. et al. (1992) Acute Toxicity of DPX-E9636 to Lemna gibba G3: Lab 
43

Project Number: 92-4-4236: 97.0991.6128.410. Unpublished study prepared by 

Springborn Laboratories Inc. 62 p. 

43539201 McKelvey, R. (1994) Influence of Rimsulfuron on Seed Germination, Seedling 

Emergence, and Vegetative Vigor of Several Terrestrial Plants: Supplement No. 

1: Lab Project Number: AMR 2074-91: HA-94-067. Unpublished study prepared 

by DuPont Agricultural Products; and Haskell Lab for Toxicology and Industrial 

Medicine (DuPont). 118 p. 

122-2 Aquatic plant growth

MRID Citation Reference

42471305 Hughes, J. (1992) DPX-E9636: Toxicity to Selenastrum capricornutum: Lab 

Project Number: B382-153-1: AMR-2316-92. Unpublished study prepared by 

malcolm Pirnie Inc. 51 p. 

42471306 Hughes, J. (1992) DPX-E9636: Toxicity to Anabaena flos-aquae: Lab Project 

Number: B382-153-2: AMR 2317-92. Unpublished study prepared by Malcolm 

Pirnie Inc. 51 p. 

42471307 Hughes, J. (1992) DPX-E9636: Toxicity to Navicula pelliculosa: Lab Project 

Number: B382-153-3: AMR 2318-92. Unpublished study prepared by Malcolm 

Pirnie Inc. 51 p. 

42711601 Feddersen, P. (1993) IN 70942-4 Metabolite Algal Growth Inhibition: Lab 

Project Number: DPC 17/930307. Unpublished study prepared by Huntingdon 

Research Centre, Ltd. 22 p. 

43043601 Thompson, S. (1993) RIMSULFURON (DPX-E9636): Influence on Growth and 

Reproduction of Skeletonema costatum: Lab Project Number: AMR 2769-93: 

112A-120. Unpublished study prepared by Wildlife International Ltd. and DuPont 

Agricultural Products. 33 p. 

123-1 Seed germination/seedling emergence and vegitative vigor

MRID Citation Reference

42471304 McKelvey, R; Kuratle, H. (1992) Infuence of Rimsulfuron on Seed Germination, 

Seedling Emergence, and Vegetative Vigor of Several Terrestrial Plants: Lab 

Project Number: AMR 2074-91. Unpublished study prepared by E. I. du Pont de 

Nemours and Co. 230 p. 

43539201 McKelvey, R. (1994) Influence of Rimsulfuron on Seed Germination, Seedling 

Emergence, and Vegetative Vigor of Several Terrestrial Plants: Supplement No. 

1: Lab Project Number: AMR 2074-91: HA-94-067. Unpublished study prepared 

by DuPont Agricultural Products; and Haskell Lab for Toxicology and Industrial 

Medicine (DuPont). 118 p. 

43683001 McKelvey, R. (1995) Influence of Rimsulfuron on Seed Germination, Seedling 

Emergence and Vegetative Vigor of Several Terrestrial Plants: Revision No. 1: 

Lab Project Number: AMR 2074-91. Unpublished study prepared by DuPont 

Agricultural Products. 230 p. 

47702506 Porch, J. (2001) In-E9260: A Greenhouse Study to Investigate the Effects on 
44

Seedling Emergence and Growth of Two Sensitive Terrestrial Plants Following 

Soil Exposure . Project Number: DUPONT/6647, 112/504. Unpublished study 

prepared by Wildlife International Ltd. 42 p.

47702507 Porch, J. (2001) IN-70942: A Greenhouse Study to Investigate the Effects on 

Seedling Emergence and Growth of Two Sensitive Terrestrial Plants Following 

Soil Exposure. Project Number: DUPONT/6648, 112/505. Unpublished study 

prepared by Wildlife International Ltd. 41 p.

47702508 Porch, J. (2001) IN-70941: A Greenhouse Study to Investigate the Effects on 

Seedling Emergence and Growth of Two Sensitive Terrestrial Plants Following 

Soil Exposure. Project Number: DUPONT/6649, 112/506. Unpublished study 

prepared by Wildlife International Ltd. 42 p.

123-2 Aquatic plant growth

MRID Citation Reference

42471308 Hoberg, J. et al. (1992) Acute Toxicity of DPX-E9636 to Lemna gibba G3: Lab 

Project Number: 92-4-4236: 97.0991.6128.410. Unpublished study prepared by 

Springborn Laboratories Inc. 62 p. 

42711601 Feddersen, P. (1993) IN 70942-4 Metabolite Algal Growth Inhibition: Lab 

Project Number: DPC 17/930307. Unpublished study prepared by Huntingdon 

Research Centre, Ltd. 22 p. 

47702510 Sloman, T. (2000) IN-70942: Influence on Growth Rate of Green Alga 

Selenastrum capricornutum. Project Number: DUPONT/3743, 13208, 280. 

Unpublished study prepared by E.I. du Pont de Nemours and Company. 40 p.

48085001 Douglas, M.; Halls, R. (1992) DPX-E9636-22 Technical: An Assessment of the 

Inhibitory Effect on the Growth of Duckweed (Lemna minor). Project Number: 

DPT/186/E/920708. Unpublished study prepared by Huntingdon Research 

Centre, Ltd. 20 p.

47702511 Softcheck, K. (2008) IN-E9260: 7-Day Toxicity Test with Duckweed (Lemna 

gibba). Project Number: 26572, 97/6431, 17979. Unpublished study prepared by 

Springborn Smithers Laboratories. 61 p.

47702512 Softcheck, K. (2008) IN-70941: 7-Day Toxicity Test with Duckweed (Lemna 

gibba). Project Number: 26573, 17980, 328. Unpublished study prepared by 

Springborn Smithers Laboratories. 66 p.

47702509 Sloman, T.L. 1996. IN-70942 (Metabolite ofDPX-E9636): Influence on Growth and 

Reproduction of Lemna gibba G3. Unpublished study performed by E.!. du Pont de 

Nemours and Company, DuPont Stine-Haskell

Research Center, Newark, Delaware. Laboratory Project ID: AMR 4060-96 and MR 

11011. Study sponsored by E.!. du Pont de Nemours and Company, Wilmington, 

Delaware. Study completed December 4, 1996.

141-1 Honey bee acute contact

MRID Citation Reference

41356331 Hoxter, K.; Jaber, M. (1989) An Acute Contact Toxicity Study with the Honey 

Bee: H # 17,463: Lab Project Number: 112-216: 267-89. Unpublished study 
45

prepared by Wildlife International Ltd. 15 p. 

885.4150 Wild mammal testing, Tier I

MRID Citation Reference

47260101 McGaughey, B.; Rives, A.; Dressel, S.; et al. (2007) NatureServe Data Evaluation 

and Review. Project Number: 06763. Unpublished study prepared by Compliance 

Services International. 78 p.

885.4750 Aquatic ecosystem test

MRID Citation Reference

47260101 McGaughey, B.; Rives, A.; Dressel, S.; et al. (2007) NatureServe Data Evaluation 

and Review. Project Number: 06763. Unpublished study prepared by Compliance 

Services International. 78 p.

850.1790 Chironomid Sediment Toxicity Test

MRID Citation Reference

47702503 Krueger, H.; Thomas, S.; Kendell, T. (2003) IN-70942: A Prolonged Sediment 

Toxicity Test with Chironomus Riparius Using Spiked Sediment. Project 

Number: 12329, 14625, 1539. Unpublished study prepared by Wildlife 

International Ltd. 66 p.

Non Target Beneficial Insect Toxicity

44217701 Candolfi, M. (1996) DPX-KX710 in Mixture with IN-KG691 Surfactant: 

Laboratory Contact Toxicity Test with the Predacious Mite, Typhlodromus pyri 

Scheuten (Acari: Phytoseiidae), Based on the IOBC Approved Method of 

Overmeer (1988): Final Report: Lab Project Number: 96-004-1028: 

1028.000.268: AMR 3679-95. Unpublished study prepared by Springborn Labs., 

(Europe) AG. 41 p. 

44217702 Kuehner, C. (1995) DPX-KV141-12: Acute Toxicity to the Predatory Mite, 

Typhlodromus pyri Scheuten (Acari: Phytoseiidae) in the Laboratory: Final 

Report: Lab Project Number: 3133-94: 94113/94114/01-NLTP. Unpublished 

study prepared by GAB Biotechnologie GMBH and IFU Umweltanalytik GMBH. 

28 p. 

44217703 Kuhner, C. (1995) DPX-KV141-12: Acute Toxicity to the Aphid Parasitoid, 

Aphidius spp. (Hymenoptera, Aphidiidae) in the Laboratory: Final Report: Lab 

Project Number: 3135-94: 94113/94114/01-NLAP. Unpublished study prepared 

by GAB Biotechnologie GMBH and IFU Umweltanalytik GMBH. 36 p. 
46

APPENDIX 2. Uncertainties Related to the Use of Incident 

Information from the Ecological Incident Information System

Incident data are used in risk assessments to provide evidence that the risk predictions from the 

screening level assessment are supported by actual effects in the field. Incident reports 

submitted to EPA since approximately 1994 have been tracked by assignment of incident 

numbers in an Incident Data System (IDS), microfiched, and then entered to a second database, 

the Ecological Incident Information System (EIIS). Additionally, there is an on-going effort to 

enter information to EIIS on incident reports received prior to establishment of current databases. 

Incident reports are not received in a consistent format (e.g., states and various labs usually have 

their own formats), may involve multiple incidents involving multiple chemicals in one report, 

and may report on only part of a given incident investigation (e.g., residues). 

Incidents entered into EIIS are categorized into one of several certainty levels regarding the 

likelihood that a particular pesticide is associated with the incident: highly probable, probable, 

possible, unlikely, or unrelated. In brief, “highly probable” incidents usually require carcass 

residues and/or clear circumstances regarding the exposure. “Probable” incidents include those 

where residues were not available and/or circumstances were less clear than for “highly 

probable.” “Possible” incidents include those where multiple chemicals may have been involved 

and it is not clear what the contribution was of a given chemical. The “unlikely” category is 

used, for example, where a given chemical is practically nontoxic to the category of organism 

killed and/or the chemical was tested for but not detected in samples. “Unrelated” incidents are 

those that have been confirmed to be not pesticide-related.

Incidents entered into the EIIS are also categorized as to use/misuse. Unless specifically 

confirmed by a state or federal agency to be misuse, or there was very clear misuse such as 

intentional baiting to kill wildlife, incidents are not typically considered misuse. 

The number of documented kills in EIIS is believed to be a small fraction of total mortality 

caused by pesticides. Mortality incidents must be seen, reported, investigated, and have 

investigation reports submitted to EPA to have the potential for entry into the database. 

Incidents often are not seen, due to scavenger removal of carcasses, decay in the field, or simply 

because carcasses may be hard to see on many sites and/or few people are systematically 

looking. Poisoned animals may also move off-site to less conspicuous areas before dying. 

Incidents may not get reported to appropriate authorities capable of investigating the incident for 

a variety of reasons including the finder may not know of the importance of reporting incidents, 

may not know who to call, may not feel they have the time or desire to call, or may hesitate to 

call because of their own involvement in the kill. Incidents reported may not get investigated if 

resources are limited or may not get investigated thoroughly, with residue analyses, for example. 

Also, if kills are not reported and investigated promptly, there will be little chance of 

documenting the cause, since tissues and residues may deteriorate quickly. Reports of 

investigated incidents often do not get submitted to EPA, since reporting by states is voluntary. 

Furthermore, the database relies heavily on registrant-submitted incident reports, and registrants 

are currently only required to submit detailed information on ‘major’ ecological incidents, while 

‘minor’ incidents are reported aggregately. 
47

Based on the 40 CFR (§159.184 Toxic or adverse effect incident reports), an ecological incident 

is considered ‘major’ if any of the following criteria are met:

Fish or wildlife:

(A) Involves any incident caused by a pesticide currently in Formal Review for 

ecological concerns. 

(B) Fish: Affected 1,000 or more individuals of a schooling species or 50 or more 

individuals of a non-schooling species. 

(C) Birds: Affected 200 or more individuals of a flocking species, or 50 or more 

individuals of a songbird species, or 5 or more individuals of a predatory species. 

(D) Mammals, reptiles, amphibians: Affected 50 or more individuals of a relatively 

common or herding species or 5 or more individuals of a rare or solitary species. 

(E) Involves effects to, or illegal pesticide treatment (misuse) of a substantial tract of 

habitat (greater than or equal to 10 acres, terrestrial or aquatic). 

Plants: 

(A) The effect is alleged to have occurred on more than 45 percent of the acreage 

exposed to the pesticide.

All other ecological incidents are considered ‘minor’ and only need to be aggregately reported. 

‘Minor’ incidents reported by the registrants are not included in the EIIS database. Therefore, 

for example, an incident could affect 900 fish, 150 birds, 45 mammals, and 40% of an exposed 

crop and not be included in the EIIS database [unless is it reported by a non-registrant (e.g., an 

incident submitted by a state agency – which are not systematically collected)]. Therefore, 

because the number of documented kills in EIIS is believed to be a small fraction of total 

mortality caused by pesticides, absence of reports does not necessarily provide evidence of an 

absence of incidents. 
48

APPENDIX 3. SIP v.1.0 Inputs and Outputs

SIP employs the following conservative assumptions to derive upper bound exposure 

estimates:

1) The chemical concentration in drinking water is at the solubility limit in water (at 25oC).

2) The assessed animals obtain 100% of their daily water needs through drinking water.

3) The daily water need is equivalent to the daily water flux rate as calculated by Nagy and 

Peterson (1988).

4) The body weight of the assessed bird is equivalent to the smallest generic bird modeled in 

T-REX (i.e., 20 g). This assumption results in the highest ratio of exposure to toxicity for the 

3 assessed avian body weights of T-REX (i.e., 20, 100, 1000 g).

5) The body weight of the assessed mammal is equivalent to the largest generic mammal 

modeled in T-REX (i.e., 1000 g). This results in the highest ratio of exposure to toxicity for 

the 3 assessed mammalian body weights of T-REX (i.e., 15, 35, 1000 g). 

Table 1. Inputs

Parameter Value

Chemical name Rimsulfuron

Solubility (in water at 25oC; mg/L) 7300

Mammalian LD50 (mg/kg-bw) 5000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian 

species

Mammalian NOAEL (mg/kg-bw) 165

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian 

species

Avian LD50 (mg/kg-bw) 2000

Avian test species mallard duck

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 1250

Bobwhite quail NOAEC (mg/kg-diet)

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird 

species

Body weight (g) of 2nd other avian species
49

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 1255.6000 1255.6000

Adjusted toxicity value (mg/kg-bw) 3845.8028 126.9115

Ratio of exposure to toxicity 0.3265 9.8935

Conclusion*

Exposure through 

drinking water alone is a 

potential concern for 

mammals

Exposure through 

drinking water alone is 

a potential concern for 

mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 5913.0000 5913.0000

Adjusted toxicity value (mg/kg-bw) 1038.4508 62.0157

Ratio of exposure to acute toxicity 5.6941 95.3468

Conclusion*

Exposure through 

drinking water alone is a 

potential concern for 

birds

Exposure through 

drinking water alone is 

a potential concern for 

birds

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. 

Therefore, when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure 

through drinking water may contribute to a total exposure that has potential for effects to non-target 

animals.
50

APPENDIX 4. STIR v.1.0 Inputs and Outputs

Rimsulfuron

Welcome to the EFED 

Screening Tool for Inhalation Risk

This tool is designed to provide the risk assessor with a rapid method for determining 

the potential

significance of the inhalation exposure route to birds and mammals in a risk 

assessment.

Input

Application and Chemical Information

Enter Chemical Name Rimsulfuron

Enter Chemical Use Herbicide

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) ground

Enter Chemical Molecular Weight (g/mole) 431.44

Enter Chemical Vapor Pressure (mmHg) 1.10E-08

Enter Application Rate (lb a.i./acre) 0.0625

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2000

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 1.58

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 5000

Enter Lowest Rat Inhalation LC50 (mg/L) 5

Duration of Rat Inhalation Study (hrs) 4

Enter Rat Weight (kg) 0.35

Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 2.55E-04

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.21E-05

Adjusted Inhalation LD50 8.04E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 3.99E-06

Exposure not Likely 

Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 6.60E-03

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 8.22E-04

Exposure not Likely 

Significant
51

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 2.55E-04

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 4.04E-05

Adjusted Inhalation LD50 2.98E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 1.36E-07

Exposure not Likely 

Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 8.30E-03

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 2.79E-05

Exposure not Likely 

Significant
52

APPENDIX 5. The Risk Quotient Method and Levels of 

Concern 

The Risk Quotient Method is the means used by EFED to integrate the results of exposure and 

ecotoxicity data. For this method, Risk Quotients (RQs) are calculated by dividing exposure 

estimates by the acute and chronic ecotoxicity values (i.e., RQ = EXPOSURE/TOXICITY). 

These RQs are then compared to OPP's levels of concern (LOCs). These LOCs are criteria used 

by OPP to indicate potential risk to non-target organisms and the need to consider regulatory 

action. EFED has defined LOCs for acute risk, potential restricted use classification, and for 

endangered species. 

The criteria indicate that a pesticide used as directed has the potential to cause adverse effects 

on non-target organisms. LOCs currently address the following risk presumption categories: 

(1) acute - there is a potential for acute risk; regulatory action may be warranted in addition to 

restricted use classification; 

(2) acute restricted use - the potential for acute risk is high, but this may be mitigated through 

restricted use classification; 

(3) acute endangered species - the potential for acute risk to endangered species is high, 

regulatory action may be warranted; and 

(4) chronic risk - the potential for chronic risk is high, regulatory action may be warranted. 

Currently, EFED does not perform assessments for chronic risk to plants, acute or chronic 

risks to non-target insects, or chronic risk from granular/bait formulations to mammalian or 

avian species. 

The ecotoxicity test values (i.e., measurement endpoints) used in the acute and chronic RQs are 

derived from required studies. Examples of ecotoxicity values derived from short-term 

laboratory studies that assess acute effects are: (1) LC50 (fish and birds), (2) LD50 (birds and 

mammals), (3) EC50 (aquatic plants and aquatic invertebrates), and (4) EC25 (terrestrial 

plants). Examples of toxicity test effect levels derived from the results of long-term laboratory 

studies that assess chronic effects are: (1) the Lowest Observed Adverse Effect Concentration 

(LOAEC) (birds, fish, and aquatic invertebrates), and (2) the No Observed Adverse Effect 

Concentration (NOAEC) (birds, fish and aquatic invertebrates). The NOAEC is generally used 

as the ecotoxicity test value in assessing chronic effects. Risk presumptions, along with the 

corresponding RQs and LOCs are summarized in Table B1.
53

Table B1. Agency risk quotient (RQ) metrics and levels of concern (LOC) per risk class.

Risk Class Risk Description RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from acute 

exposures

Peak EEC/LC50

1

0.5

Acute 

Restricted 

Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use 

classification

Peak EEC/LC50

1

0.1

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

Peak EEC/LC50

1

0.05

Chronic Potential for effects to non-listed and listed animals 

from chronic exposures 

60-day EEC/NOEC (fish) 1

21-day EEC/NOEC 

(invertebrates)

Terrestrial Animals (mammals and birds)

Acute Potential for effects to non-listed animals from acute 

exposures

EEC2/LC50 (Dietary) 0.5

EEC/LD50 (Dose)

Acute 

Restricted 

Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use 

classification

EEC2/LC50 (Dietary) 0.2

EEC/LD50 (Dose)

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

EEC 2/LC50 (Dietary) 0.1

EEC/LD50 (Dose)

Chronic Potential for effects to non-listed and listed animals 

from chronic exposures

EEC 2/NOAEC 1

Plants

Non-Listed Potential for effects to non-target, non-listed plants 

from exposures

EEC/ EC25 1

Listed Plant Potential for effects to non-target, listed plants from 

exposures

EEC/ NOEC 1

EEC/ EC05

1 LC50 or EC50. 2 Based on upper bound Kenaga values.