2

REGISTRATION REVIEW

ECOLOGICAL RISK ASSESSMENT

PROBLEM FORMULATION FOR:

Sulfosulfuron

PREPARED BY:

Ron Parker, Senior Environmental Engineer

Amy Blankinship, Chemist

Environmental Risk Branch 3

Environmental Fate and Effects Division

Office of Pesticide Programs

REVIEWED BY:

Melissa Panger, Senior Effects Scientist

James Hetrick, Senior Advisor

Environmental Risk Branch 3

Environmental Fate and Effects Division

Office of Pesticide Programs
3

TABLE OF CONTENTS

TABLE OF CONTENTS ..................................................................................................................... 3

1.0 Description of Regulatory Action .............................................................................. 6

2.0 Stressor Source and Distribution.............................................................................. 6

2.1 Mechanism of Action ........................................................................................................ 6

2.2 Overview of Pesticide Usage ............................................................................................ 7

3.0 Fate of Sulfosulfuron in the Environment............................................................. 10

3.1 Metabolites and/or Degradates...................................................................................... 14

4.0 Conclusions from Previous Assessments............................................................ 16

5.0 Ecological Effects ........................................................................................................ 17

5.1 Terrestrial Organism Toxicity Data.............................................................................. 18

5.1.1 Avian Toxicity, Acute............................................................................................... 19

5.1.2 Avian Toxicity, Chronic ........................................................................................... 19

5.1.3 Mammal Toxicity, Acute .......................................................................................... 20

5.1.4 Mammal Toxicity, Chronic....................................................................................... 20

5.1.5 Terrestrial Invertebrate Toxicity, Acute ................................................................... 21

5.1.6 Terrestrial Plant Toxicity .......................................................................................... 21

5.2 Aquatic Organism Toxicity Data................................................................................... 22

5.2.1 Fish Toxicity Data, Acute ......................................................................................... 24

5.2.2 Fish Toxicity Data, Chronic...................................................................................... 24

5.2.3 Aquatic Invertebrate Toxicity Data, Acute ............................................................... 25

5.2.4 Aquatic Invertebrate Toxicity Data, Chronic............................................................ 25

5.2.5 Aquatic Plant Toxicity Data...................................................................................... 26

6.0 Evaluation of Non-definitive Toxicity Values ....................................................... 27

7.0 Uncertainties Associated with Lack of Data or Acceptable Studies.............. 29

7.1 Parent Sulfosulfuron....................................................................................................... 29

7.2 Degradate/Metabolites of Sulfosulfuron....................................................................... 31

8.0 Incident Database Review ......................................................................................... 34

9.0 Monitoring Data ............................................................................................................ 34

10.0 Clean Water Act............................................................................................................ 35

11.0 Ecosystems Potentially at Risk................................................................................ 36

12.0 Assessment Endpoints .............................................................................................. 36

13.0 Conceptual Model........................................................................................................ 37

14.0 Risk Hypothesis ........................................................................................................... 41

15.0 Analysis Plan................................................................................................................. 43

15.1 Ecological Measures of Exposure .................................................................................. 43

15.2 Drinking Water Measures of Exposure ........................................................................ 44

15.3 Measures of Effect........................................................................................................... 44

15.4 Uncertainties in the Analysis Plan................................................................................. 45

15.5 Endangered Species Assessments.................................................................................. 45

16.0 Anticipated Data Needs.............................................................................................. 46

16.1 Environmental Fate ........................................................................................................ 48

16.2 Ecological Effects............................................................................................................ 48

17.0 Other Information Needs............................................................................................ 49

18.0 Data Call-In Tables For Fate and Ecological Effect Studies............................. 50
4

18.1 Environmental Fate Studies........................................................................................... 50

18.2 Ecological Effects Studies............................................................................................... 52

19.0 References..................................................................................................................... 58

Tables

Table 1. Current Registrations of Sulfosulfuron ...................................................................... 7

Table 2. Current Application Data for Sulfosulfuron .............................................................. 8

Table 3. Summary of Uncertainties for Registered Label for Sulfosulfuron ......................... 8

Table 4. Screening Level Usage Estimates (SLUA) for Agricultural Uses of 

Sulfosulfuron as of December 1, 2010. .......................................................................... 10

Table 5. Physical/Chemical Properties for Sulfosulfuron (Source: EPA Product Chemistry 

Review)............................................................................................................................. 12

Table 6. General Environmental Fate Property Values for Sulfosulfuron ........................... 13

Table 7. Degradation/Metabolite Products Observed in Various Studies............................ 14

Table 8. Most Sensitive Terrestrial Organism Toxicity Values for Sulfosulfuron Based on 

Available Data ................................................................................................................. 18

Table 9. Most Sensitive Aquatic Organism Toxicity Values for Sulfosulfuron Based on 

Available Data ................................................................................................................. 23

Table 10. Detection Frequency and Maximum Concentration of Sulfosulfuron at Four 

Drinking Water Facilities............................................................................................... 35

Table 11. Available Ecological Effects Data for Terrestrial Animals Exposed to 

Sulfosulfuron and Remaining Data Gaps..................................................................... 46

Table 12. Available Ecological Effects Data for Aquatic Animals Exposed to Sulfosulfuron 

and Remaining Data Gaps. ............................................................................................ 46

Table 13. Available Ecological Effects Data for Plants Exposed to Sulfosulfuron and 

Remaining Data Gaps..................................................................................................... 47

Table 14. Degradates and Requested Studies.......................................................................... 48

Figures

Figure 1. 2002 Estimated Annual Agricultural Use Map for Sulfosulfuron (Source: USGS)9

Figure 2. Sulfosulfuron Chemical Structure ........................................................................... 11

Figure 3. Conceptual Model Depicting Potential Risks to Terrestrial Animals and Plants 

from the Use of Sulfosulfuron........................................................................................ 38

Figure 4. Conceptual Model Depicting Potential Risks to Aquatic Animals and Plants from 

the Use of Sulfosulfuron ................................................................................................. 39

Figure 5. Conceptual Model Depicting Potential Risks to Terrestrial Vertebrates and 

Invertebrates from Inhalation and Drinking Water Exposure from the Use of 

Sulfosulfuron ................................................................................................................... 40

Appendicies

Appendix A. MRID Bibliography ............................................................................................ 60

Appendix B. Summary of Structure, Chemical Formulas and Common Names................ 74

Appendix C. Summary of Toxicity Studies for Sulfosulfuron............................................... 76

Appendix C. Summary of Toxicity Studies for Sulfosulfuron............................................... 76

Appendix D. GENEEC2 Output............................................................................................... 83
5

Appendix E. T-REX Output ..................................................................................................... 84

Appendix F. SIP Output............................................................................................................. 87

Appendix G. STIR Input and Output...................................................................................... 88
6

1.0 Description of Regulatory Action

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

assessing the risks of pesticides1. 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 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 sulfosulfuron uses continue 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 

opening, which starts the public phase of the review process. This problem formulation 

considers all current and active registrations for sulfosulfuron. The MRID bibliography for 

sulfosulfuron is presented in Appendix A. 

The purpose of problem formulation is to provide the foundation for the environmental fate 

and ecological risk assessment being conducted for sulfosulfuron. It sets the objectives for the 

risk assessment, evaluates the nature of the problem, and provides a plan for analyzing the data 

and characterizing the risk (US EPA, 1998).

2.0 Stressor Source and Distribution

Sulfosulfuron (PC code 085601) is used for pre and postemergence control of many annual 

and perennial grasses and broadleaf weeds, such as brome and mustard species. It is registered 

for use on wheat, pastures (including Bermuda grass and Bahia grass), rangeland and a wide 

variety of non-crop uses including golf courses, fallow land and rights-of-ways.

2.1 Mechanism of Action

Sulfosulfuron [N-[[4,6-dimethoxy-2-pyimidinyl)carbonyl]-2-)ethylsulfonyl)-imidazo[l,2-

a]pyridine-3-sulfonamide] is a sulfonylurea class herbicide that inhibits acetolactate synthase

(ALS). ALS is necessary for the synthesis of amino acids in plants. 

 

1

(http://www.epa.gov/oppsrrd1/registration_review/)
7

2.2 Overview of Pesticide Usage

Sulfosulfuron is formulated either as a water dispersible or soluble granule formulation 

(WDG or WSG) or a soluble concentrate (SC). 

According to the labels, sulfosulfuron may be applied with aerial or ground equipment to 

wheat, non-crop, pasture and rangeland, sod farms, golf courses, landscaped areas, native grass 

sites, and ornamental nurseries. The type of applications include: broadcast, hand-held and high 

volume. The type of equipment that may be used includes: ground, aircraft, helicopter, hand-held 

spray guns, and backpack sprayers.

Current registrations and uses of sulfosulfuron are shown in Table 1 and Table 2 below. 

Table 1. Current Registrations of Sulfosulfuron

Product Name

(Registrant)

EPA Registration 

Number

(latest label date)1

Active Ingredients

(% w/w) Crops

Section 3 End Use Products and Technical Chemical

Mon 37500Technical

(Monsanto Company)

Technical Chemical

524-499

(10/12/10)

Sulfosulfuron 98.0% Not Applicable

Maverick/Outrider 

Herbicide

(Monsanto Company)

Water Dispersible Granule

524-500

(09/22/10)

Sulfosulfuron 75.0%

Non-crop sites2; Pasture and 

Rangeland3; and Wheat 

(winter and spring)

Maverick Pro (C/A)

(Monsanto Company)

Water Soluble Granule

524-525

(05/25/00)

(09/02/01 

Supplemental label)

Sulfosulfuron 75.0% Wheat (winter)

Mon 37525 NC/ Mon 

37525 W

(Monsanto Company)

Soluble Concentrate

524-526

(03/15/01) Sulfosulfuron 24.1%

Non-crop sites2; Wheat 

(winter and spring)

Mon 44940 SC

(Monsanto Company)

Soluble Concentrate

524-533

(02/27/02) Sulfosulfuron 24.1% Sod farms and Golf Courses

Certainty Turf Herbicide

(Monsanto Company)

Water Dispersible Granule

524-534

(12/04/06)

(01/25/10 

Supplemental label)

Sulfosulfuron 75.0%

Landscaped areas; Ornamental 

Nurseries; Sod farms and 

Highly managed turf and 

Native grass sites4

1 Date of label according to Office of Pesticide Program Information Network (OPPIN)

2 Non-crop sites include: airports, conservation areas (non-crop tree sites) (on 524-500 only), ditch banks, dry 

ditches, dry canals, fallow areas, fencerows, industrial sites, lumberyards, manufacturing sites, natural areas (on 524-

500 only), petroleum tank farms and pumping installations, railroads, roadsides, storage areas, utility rights-of-way, 

utility sites (on 524-500 only) and substations, warehouse areas; wildlife areas (non-crop tree sites) (on 524-500 

only), and similar industrial and noncrop sites (on 524-526 only).

3

Pasture and Rangeland sites include: bermudagrass and bahiagrass pasture sites, pasture and rangeland sites in 

states west of Mississippi River, native grasses and conservation reserve program sites, and forestry conifer release 

program.

4

Sod farms, highly managed turf and native grass sites include: apartment complexes, athletic fields, cemeteries, 

golf courses (except putting greens), hotel properties, office complexes, parks, public turf areas, retail sites, storage 

facilities, school grounds, sod and turfgrass seed farms and other highly managed turfgrass sites.
8

Table 2. Current Application Data for Sulfosulfuron

Crop Max Single 

Application 

rate

lbs a.i./A

Number of 

Applications

Max 

Application 

per 

year/season

lb a.i./A

Application 

Method

Application 

Interval

(days)

Reg #*

Non-crop sites 0.0938 N.S. 0.125 Ground; 

Aerial

21 to N.S 524-500; 

524-526

Pasture and 

Rangeland

0.0938 1 to N.S 0.125 Ground; 

Aerial

21 to N.S 524-500; 

524-534

Sod farms and Turf 

areas

0.0938 1 to N.S. 0.125 Ground 14 to N.S. 524-533; 

524-534

Landscaped areas 

and Ornamental 

Nurseries

0.0586 1 0.117 Directed 

Spray; Overthe-top; Preplant

4 wks 524-534 

(Supplemental label)

Wheat (winter and 

spring)

0.0313 1 or 

2 (524-500 

only)

0.0313 

(0.0352)1/

cropping 

season

Ground; 

Aerial

Not 

applicable for 

single app; 14 

days for split 

app. (524-500 

only)

524-500; 

524-525; 

524-526 

N.S.=not specified on label

*: While every crop listed in the “Crop” column may not be a registered use for every EPA Reg #’s listed at least 

one crop is for every reg #. Application rates represent maximum application rate for a least one of the EPA Reg# 

listed. Other labels may have slightly different application rates.

1 Max rate of 0.0352 lb a.i./A for split applications for label 524-500 only where single max app is 0.0176 lb a.i./A

There are some uncertainties in the registered labels such as re-application intervals and 

maximum number of applications. A summary of the uncertainties for each label is presented 

below in Table 3.

Table 3. Summary of Uncertainties for Registered Label for Sulfosulfuron

Product Name

(EPA Reg Number)

Uncertainty

Maverick/Outrider Herbicide

(524-500)

Maximum number of applications are not defined for: bermudagrass and 

bahiagrass non-crop sites, tall fescue non-crop sites, pasture and rangeland sites 

(w. of Mississippi R), native grasses and conservation reserve program, noncrop tree sites, forestry conifer release use

Re-application intervals are not define for: bermudagrass and bahiagrass noncrop sites (hand-held & high-volume app), tall fescue non-crop sites, pasture 

and rangeland sites (w. of Mississippi R), forestry conifer release use

Mon 37525 NC/ Mon 37525W

(524-526)

Maximum number of applications and re-application interval are not defined for 

non-crop uses for Mon 37525 NC

Mon 44940 SC

(524-533)

Maximum number of applications (all uses) and the re-application interval 

(bermudagrass-for removal of ryegrass only) are not defined. In addition, it is 

unclear whether the 30 day interval application interval for the other uses is for 

fall application only or does it apply to year-round application.

Certainty Turf Herbicide

(524-534)

Maximum number of applications and re-application interval are not defined 

for: buttonweed suppression, annual bluegrass control non-overseeded turf, 

annual bluegrass control prior to overseeding turf
9

In situations where the label is not clear on maximum number of applications or application 

interval, conservative assumptions will be made when conducting the exposure assessment. For 

example, the number of applications will be assumed to be two when the maximum per year is 

slightly more than the single maximum application. Also, for re-application interval, the 

assumed application interval may be the shortest reported application rate for the particular use. 

These assumptions may overestimate the exposure concentrations, therefore, it is advantageous 

to have labels that clearly define maximum number of applications and application intervals.

A national map showing the estimated poundage of sulfosulfuron used in 2002 is presented 

in Figure 1. The map was downloaded from the U.S. Geological Survey (USGS), National 

Water Quality Assessment Program (NAWQA) website. 

(http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m9125 ; accessed 

February 25, 2011)

. 

Figure 1. 2002 Estimated Annual Agricultural Use Map for Sulfosulfuron (Source: USGS)

Table 4 below shows the estimates of agricultural uses of sulfosulfuron as of December 1, 

2010.
10

Table 4. Screening Level Usage Estimates (SLUA) for Agricultural Uses of 

Sulfosulfuron as of December 1, 2010.

 

Crop Lbs. A.I.

1 Fallow, Summer <500

2 Pasture 1,000

3 Wheat 30,000

All numbers rounded.

<500 Less than 500 pounds of active ingredient

<2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated

SLUA data sources include: 

USDA-NASS (United States Department of Agriculture's National Agricultural Statistics 

Service) 

Private Pesticide Market Research

California DPR (Department of Pesticide Regulation)

Usage information for non-agricultural uses is not currently available.

3.0 Fate of Sulfosulfuron in the Environment

The chemical name for sulfosulfuron is N-[[(4-Hydroxy-6-dimethoxy-2-pyrimidinyl) amino] 

carbonyl]-2-(ethylsulfonyl)imidazo[1,2-a]pyridine-3-sulfonamide. EPA Product Chemistry 

Review Physical/Chemical Properties are listed in Table 5. The structure of sulfosulfuron is 

shown in Figure 2. A summary of the environmental fate data for sulfosulfuron and 

sulfosulfuron degradation products were presented in the Drinking Water Assessment dated 

05/24/2007 and are presented here in Table 6. This table also contains calculated Residue of 

Concern (ROC) chemical properties which are more fully described later in this document.
11

Figure 2. Sulfosulfuron Chemical Structure

The primary routes of sulfosulfuron dissipation will be through leaching, runoff, and spray 

drift. Sulfosulfuron is highly mobile due to its low sorption affinity as described by the 

Freundlich sorption isotherm (Kads). Sulfosulfuron is an ionic (pKa=3.5) compound and hence 

will be anion under environmentally relevant pHs. The aerobic soil metabolism studies show 

moderate to slow degradation. No anaerobic soil metabolism study was submitted. Hydrolysis 

studies show that sulfosulfuron will be persistent in the neutral and alkaline environments. Rapid 

aqueous photolysis and moderate aerobic aquatic metabolism will contribute to the degradation 

of sulfosulfuron in surface water. Environmental fate studies show that mobility and persistence 

of sulfosulfuron is correlated with pH (more persistent and mobile with increasing pH). Due to 

its moderate persistence and high mobility in soil, sulfosulfuron has the potential to leach to 

groundwater.

Sulfosulfuron undergoes acid catalyzed hydrolysis where half-lives are 7 days @ pH4; 48 

days @ pH5 168 days @ pH7; 156 days @ pH9) and soil metabolism rates (expressed as halflives range from 30 (75 for unextractable residues) to 226 days. Sulfosulfuron may undergo 

photodegradation in surface water systems, but is insignificant on soil. In surface water the 

aqueous photolysis half-life is 2.47 days. The aerobic aquatic metabolism half-life is 26.4 days. 

Sulfosulfuron is not volatile. In the New Chemical Review, EFED determined that sulfosulfuron 

had a low potential to bioaccumulate and a fish bioaccumulation study was not required. 

The mobility as defined by the Freundlich sorption isotherm (Kads) indicated that 

sulfosulfuron is highly mobile. The Kads ranged from 0.08 to 0.71, the lowest non-sand was 0.23 

mL/g. Because sulfosulfuron is a weak acid (ionized compound), other soil factors (e.g., 

mineralogy, clay content) are expected to influence sorption, Sulfosulfuron can also move off 

site via spray drift when the pesticide is being applied

Terrestrial field dissipation studies in Washington and California yielded dissipation half-lives 

from the soil surface ranging from 13 to 41 days (MRID 44295732). For terrestrial field 

dissipation studies in North Dakota and Texas, the half-lives were 75 and 13.6 days, respectively 

(MRID 44295733). 
12

Table 5. Physical/Chemical Properties for Sulfosulfuron (Source: EPA Product Chemistry 

Review)

Physical/Chemical Properties (Source: EPA Product 

Chemistry Review)

Molecular formula: C16H18N6O7S2

Molecular weight: 470.49

CAS Registry No.: 141776-32-1

Physical State: powder

Melting Point: mean range: 180.9 - 184.1°C

Density: 1.55 g/ml (20°C)

Water Solubility (20oC): pH 5: 17.60 ± 2.71 mg/L

pH 7: 1626.8 ± 39.8 mg/L

pH 9: 482.44 ± 8.35 mg/L

Vapor Pressure (20oC): 2.29 x 10-10 mm Hg

Dissociation Constant: pKa = 3.51 at 20°C

Octanol/water Partition Coefficient (Log P) pH 5: 0.81

pH 7: -1.01

pH 9: -1.37

Stability: Stable (no stability data for metal ions 

provided)
13

Table 6. General Environmental Fate Property Values for Sulfosulfuron

Property Value Data Source

Chemical Name N-[[4,6-dimethoxy-2-pyrimidinyl)carbonyl]-2-) 

ethylsulfonyl)-imidazo[1,2-a]pyridine-3-

sulfonamide

Solubility 17.6 ppm @ pH 5; 1627 ppm @ pH 7; 

482 ppm @ pH9

MRID 442957-20

Hydrolysis Half-Life @ 25 C 7 days @ pH4; 48 days @ pH5

168 days @ pH7; 156days @ pH9

MRID 442957-20

Aqueous Photolysis Half-Life Sulfosulfuron

2.47 days (sulfosulfuron)

ROC

4.97 days (sulfosulfuron + Sulfonic acid + 

sulfone)

MRID 442957-21

Sulfosulfuron

Aerobic Soil Metabolism Half-Life

[stated to be DT50 values) 

[75*,88*, 92, 194, 226 days]

[*extractable residue values in these studies 

were 30 and 37 days]

Total Residues of Concern (ROC)

Aerobic Soil Metabolism Half-Life

(ROC = sum of sulfosulfuron + sulfonamide)

[calculated by first order linear regression]

[100.5, 223, 266.6, 247.6]

Sulfosulfuron*

mean (3) = 184.0 days; median = 194.0 days

std. = 87.43 days

mean (5) = 143.0 days; median = 92.0 days

std. = 83.64 days

ROC*

mean = 209.5 days ; median = 235.3 days

std. = 74.78 days

*these values were calculated using the 

unextractable residue halflife values 

MRID 442957-31

MRID 442957-23

MRID 442957-31

Sulfosulfuron

Aerobic Aquatic Metabolism half-life

Total System (water + sediment)

[32.7 (river) 20.0 (pond)]

Total Residues of Concern (ROC)

(ROC = sum of sulfosulfuron + sulfonamide)

Total System (water + sediment)

[37.7 (river) 30.8 (pond)]

Sulfosulfuron

mean = 26.4 days

std. = 8.98 days

ROC

mean = 34.25 days

std. = 4.87 days

Limited sulfonamides observed

River and Pond System @ 

20 C MRID 442957-26

Anaerobic Aquatic Metabolism DT50 Mean DT50 (sterile water): 126 days MRID 442957-25

Mobility Sulfosulfuron

Freundlich Kads [0.36, 0.08, 0.08, 0.23, 0.71]

Koc [ 40, 25, 6.6, 5.3, 89]

Sulfonamide

Freundlich Kads [0.52, 2.07, 1.49, 0.91]

Koc [ 61, 106 , 261, 223]

Sulfosulfuron (ml/g)mean

Kads = 0.29; median Kads = 0.23

mean Koc = 33.2; median Koc = 25.0

Sulfonamide (ml/g)

mean Kads = 1.25; median Kads = 1.20

mean Koc = 162.8; median Koc = 164.0

MRID 442957-28
14

3.1 Metabolites and/or Degradates

Degradation of sulfosulfuron in the environment produces a number of transformation 

products. The major (>10%) degradation products seen in metabolism studies are primarily the 

sulfonamide and aminopyrimidine products, as well as the desmethyl product. Several other 

major degradates are observed in the aqueous photolysis study. The degradates mentioned above 

are formed through hydrolytic cleavage of the sulfonylurea bond. Degradation of sulfosulfuron 

in soil or water occurs under acidic, neutral and alkaline conditions; however, degradation occurs 

most rapidly under acidic conditions. Depending on the pH of the system, the parent 

sulfosulfuron may be transformed to one of the degradation products. The rate of formation and 

distribution of the sulfonamide and aminopyrimidine degradates is reflected by the decline in 

concentration of sulfosulfuron. The major degradation products that were observed in several

environmental fate studies and their formation percentage is listed in Table 7 (structures, 

chemical formulas, and common names are listed in Appendix B. 

Table 7. Degradation/Metabolite Products Observed in Various Studies

Common Name 

(CAS #, if 

available) 

Chemical Name Degradation Process Forming

Metabolite: Percent Formed: MRID

Desmethyl N-[[(4-Hydroxy-6-dimethoxy-2-

pyrimidinyl)amino]carbonyl]-2-

(ethylsulfonyl)imidazo[1,2-

a]pyridine-3-sulfonamide

Aerobic soil metabolism: extractable-2.58% and 

1.8% of the applied 14C-activity at day 360; bound1.15% and 0.97% of the applied 14C-activity at day 

360 (This minor route of transformation involves 

the demethylation of sulfosulfuron to yield 

desmethyl, which is further degraded to 

guanidine): 442957-23

Aerobic soil metabolism: extractable-5.2%, 2.6% 

and 1.9% of the applied 14C-activity at day 100 in 

3 soils: 442957-31

Aerobic aquatic metabolism: 14 and 13% at day 

30, <1% in sterile system only: 442957-26

Anaerobic aquatic metabolism: 11.6% and ≤6.3% 

of the applied dose at day 365; 2.0% in sterile 

solution at day 365: 442957-25

Soil column leaching: 2.7% of applied dose in 

leachates: 442957-27

Sulfamic acid [[(4,6-dimethyoxy-2-

pyrimidinyl)amino]carbonyl]-

sulfamic acid

Aqueous photolysis: 14% at 48 hour, 19% at 96 

hours, 21% at 6 days: 442957-21

Aminopyrimidine 4,6-dimethoxy-2-pyrimidinamine Hydrolysis: 92% (pH 4), 31% (pH 5), 12% (pH 

7), and 15% (pH 9) at 30 days: 442957-20
15

Aqueous photolysis: 10% at 48 hours, 24% at 96 

hours, 28% at 6 days: 442957-21

Aerobic soil metabolism: extractable – 39.92% 

and 29.33 % of the applied 14C-activity; bound 

27.10 and 32.96% at day 360: 442957-23

Aerobic soil metabolism: 1.7%: 442957-26

Soil column leaching: limited mobility - <2% of 

applied dose in leachates: 442957-27

Anaerobic aquatic metabolism: 13% at day 365 

(identified at hydrolysis product): 442957-25

Sulfonamide

(63-74-1)

2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine-3-sulfonamide

Hydrolysis: 93% (pH 4), 34% (pH 5), 13% (pH 7), 

and 15% (pH 9) at 30 days: 442957-20

Aerobic soil metabolism: Extractable- 54.69% and 

46.66 % (maximum 14C-activity) ; bound 15.29 

and 14.46% of amount applied at 360 days: 

442957-23

Aerobic soil metabolism: 6.1% : 442957-26

Aerobic soil metabolism: 3,7%, 4.4%, and 12.8 % 

(maximum 14C-activity) at day 100: 442957-31

Aerobic aquatic system: Minor transformation 

product (6.1%). (Identified as hydrolysis product): 

442957-26

Anaerobic aquatic system: Major transformation 

product 64.9% of 14C-activity at day 365 

(Identified as hydrolysis product): 442957-25

Soil photolysis: irradiated -13% at day 14, and 

22.6% at Day 30, dark control 24.4% at day 30; 

442957-22

Soil column leaching: 2% of applied dose in 

leachates: 442957-27

Sulfonic acid

(27176-87-0)

2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine-3-sulfonic acid

Aqueous photolysis: 13% at 72 hours, 15% at 96 

hours, 13% at 6 days: 442957-21

Aerobic soil metabolism: Minor transformation 

product (<0.5%): 442957-31

Aquatic sediment: Not mentioned in aerobic 

aquatic systems study: 442957-26

Sulfone 2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine

Aqueous photolysis: 14% at 24 hours; 28% at 96 

hours and 21% at 6 days: 442957-21

Urea (4,6-dimethoxy-2-pyrimidinyl)-

urea

Anaerobic aquatic metabolism: 29.2% (postulated 

to form due to elevated ammonia in system): 

442957-25 

N-hydroxy urea N-(4,6-dimethoxy-2-pyrimidinyl)-

N’-hydroxy-urea

Aqueous photolysis: 13% at 24 hours, 15% at 48 

hours, 7% at 96 hours: 442957-21
16

Oxamic acid 2-imino-alpha-oxo-1 (2H)-

pyridineacetic acid

Aqueous photolysis: 12% at 96 hours; 16% at 6 

days: 442957-21

The Residues of Concern2(ROC) as determined by the Health Effects Division (HED) are

sulfosulfuron and its ethyl sulfone metabolites [including 2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine-3-sulfonic acid (sulfonic acid); 2-(ethylsulfonyl)-imidazo[1,2-a]pyridine-3-

sulfonamide (sulfonamide); and 2- (ethylsulfony1)-imidazo[1,2-alpyridine (sulfone)].2 

Therefore, a total toxic residue (TTR) approach by EFED will be undertaken when assessing 

exposure to non-target animals. Sulfosulfuron and the residues of concern (metabolites) were all 

considered and converted to the common ethyl sulfone moiety, 2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine. As stated above, calculated environmental fate properties for the Residues of Concern 

(RoC) are included in Table 6 above. 

Plant metabolite formation appears to occur by demethylation and cleavage of sulfonylurea 

bond. A plant metabolite study was available in which wheat was treated with sulfosulfuron 

either pre or post emergence at approximately 2 and 5 times the registered application rate of 

sulfosulfuron. Parent sulfosulfuron residues in wheat plants represented the majority of total 

residues with the other residues generally representing <10% of the total radioactive residues 

(TRR), except for wheat straw that was exposed to sulfosulfuron pre-emergence at 

approximately 5 times the registered application rate. The metabolites in this study that were 

>10% of the TRR included the sulfonamide and guanidine metabolite, 23 and 18% of the TRR, 

respectively. The report stated that no phytotoxic effects were noted at either treatment rate.3 

4.0 Conclusions from Previous Assessments

In October 1998, the Environmental Risk Branch III in the Environmental Fate and Effects 

Division (EFED) completed a Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) 

Section 3 new chemical assessment for use of sulfosulfuron on wheat, forestry and other noncrop sites.4

 The review concluded that sulfosulfuron exceeded the level of concern (LOC) for 

risk to nontarget terrestrial and aquatic vascular plants (risk quotients (RQs) for terrestrial plants: 

3-133; aquatic vascular plant RQs: 2-3), and that sulfosulfuron may persist in the environment 

under certain conditions. In addition, as an SU herbicide it has a high potential to move off-site 

by drift, runoff and via wind-blown soil particles, and it may contaminate surface waters that 

may pose a risk to irrigated crops. 

 

2 Health Effects Division (HED) memorandum from Susie Chun and Alberto Protzel to George Kramer; Subj: 

Sulfosulfuron (Maverick ) in/on Wheat. PP#7F04840. The ad hoc Metabolism Assessment Review Committee 

Meeting Held on 9/3/98. DP Barcode: D249043, November 23, 1998.

3 Memorandum from Susie Chun in HED to Jim Tompkins in Registration Division; Subj: PP# 7F04840. New 

Chemical- Sulfosulfuron (i.e. MON37500, Maverick ) in/on Wheat. Evaluation of Residue Data and Analytical 

Methods. MRID#s: 442957-02 thru 04, 442957-07 thru11, 442957-13 thru 14, 442957-16 thru 18, 44295735, 

44309301. DP Barcodes: D237683, D239109. Chemical No. 085601. Case No. 288878; September 28, 1998.

4 Memorandum from Raanan Bloom and William Erickson, Environmental Risk Branch III in 

Environmental Fate and Effects Division to Donald Stubbs, Herbicide Branch in Registration Division; 

Subj: Sulfosulfuron: New Chemical Environmental Risk Assessment, Chemical: 085601/Company: 

000524 Monsanto Agricultural Company, DP barcode: D237257, D241674, D241678, D249831, October 

30, 1998.
17

In July 2007, EFED completed a risk assessment for a Section 3 new use of sulfosulfuron on 

Bermudagrass and Bahiagrass pastures.5The assessment concluded use of sulfosulfuron on these 

pastures is presumed to pose risk to endangered and non-endangered non-target terrestrial plants 

and aquatic vascular plants. The risk quotients (RQs) for a single application for terrestrial 

plants exceed the LOC by one to three orders of magnitude (3-258). RQs for the seasonal rate are 

approximately twice that of the single application. No acute or chronic risks were presumed for 

terrestrial and aquatic animals. 

Finally, several Section 18 emergency exception assessments were completed for the use of 

sulfosulfuron on Bermudagrass hay fields or pastures and for sulfosulfuron use on wheat. These 

Section 18 requests were from 1997 to 2006, and included the states: Oregon, Washington, 

Idaho, Oklahoma, Georgia, Louisiana, Arkansas, and Texas. Again, these assessments 

concluded the potential for risk to endangered and non-endangered terrestrial plants and aquatic 

vascular plants.6

5.0 Ecological Effects

The Agency evaluates the potential for adverse effects to non-target terrestrial and aquatic 

organisms as a result of sulfosulfuron usage. As described in the Agency’s Overview Document 

(US EPA, 2004), the most sensitive endpoint for each taxon is used to estimate potential risks. 

Assessment endpoints include direct toxic effects on the survival, reproduction, and growth of 

terrestrial and aquatic life, as well as indirect effects, such as reduction in prey base and/or 

modification of habitat. The evaluated taxa include freshwater fish, freshwater aquatic 

invertebrates, birds, small mammals, terrestrial invertebrates, algae, and terrestrial plants. 

Acute (short-term) and chronic (long-term) toxicity information is characterized based on 

registrant-submitted studies and a comprehensive review of the open literature on sulfosulfuron. 

Currently, an open literature ECOTOX search has not been conducted at this time, however this 

search will be conducted and a review of open literature studies will be conducted for potential 

use in the registration review ecological risk assessment. Other sources of information, 

including use of the acute probit dose response relationship to establish the probability of an 

individual effect and reviews of the Ecological Incident Information System (EIIS), are 

conducted to further refine the characterization of potential ecological effects associated with 

exposure to sulfosulfuron. A summary of the available ecotoxicity information and the incident 

information for sulfosulfuron are provided below. A summary of the studies are presented in 

Appendix C.

 

5 Memorandum from James Wolf and Stephen Carey, Environmental Risk Branch III in Environmental Fate and 

Effects Division to James Tompkins, Herbicide Branch in Registration Division; Subj: Ecological Risk assessment 

for Section 3 New Use (R17.3) of Sulfosulfuron on Bermudagrass and Bahiagrass pastures; DP barcode: D327364, 

July 26, 2007.

6

From assessments with the following DP barcode: D304290, D304476, D304659, D312625, D328236; also from 

memorandums from EFED to Minor Use, Inerts and /or Emergency Response Branch on August 11, 1997 and 

September 17, 1998.
18

5.1 Terrestrial Organism Toxicity Data

Table 8 summarizes the most sensitive ecological toxicity endpoints based on currently 

available data for terrestrial organisms. A brief summary of submitted data considered relevant 

to this ecological risk assessment is presented below.

Table 8. Most Sensitive Terrestrial Organism Toxicity Values for Sulfosulfuron Based on 

Available Data

Assessment 

Endpoint 

Measures of 

Effect 

Species Toxicity Value MRID Number; 

Reference; and 

Study 

Classification

Abundance 

(i.e., survival, 

reproduction, 

and growth) of 

individuals 

and 

populations of 

birds 

Avian acute 

oral (single 

dose) 14-day 

LD50

Northern bobwhite 

quail (Colinus 

virginianus)

LD50 > 2250 mg a.i./kg-bw

NOAEC = 810 mg a.i./kg-bw

(based on clinical signs of toxicity)

44295768;

Campbell and 

Beavers, 1994;

Acceptable

Avian 

subacute 5-day 

dietary LC50

Mallard duck 

(Anas 

platyrhynchos)

LC50 > 5110 mg a.i./kg-diet 

NOAEC (observed) = 3000 mg 

a.i./kg-diet 

(based on body weight)

44295771;

Campbell and 

Beavers,1994;

Acceptable

Avian 

reproduction 

NOAEC

Mallard duck 

(Anas 

platyrhynchos)

NOAEC = 245 mg a.i./kg-diet 

(based on 14-d old body weights)

44295773;

Frey et. al, 1996;

Acceptable

Abundance

(i.e., survival, 

reproduction, 

and growth) of 

individuals 

and 

populations of 

mammals 

Mammalian 

acute oral 

(single dose) 

14-day LD50

Rat (Rattus 

norvegicus)

LD50 > 5000 mg/kg-bw 

(Male &Female) (1)

44295737;

Bonnette, 1993;

Acceptable

Mammalian 2-

generation rat 

reproduction

NOAEL

Rat (Rattus 

norvegicus)

NOAEL = 5,000 mg/kg-diet

(312 mg/kg/day) (2)

(based on decreased body wt in 

offspring and paternal toxicity)

44295758;

Naylor and 

Thake,1996;

Acceptable

Survival of 

beneficial 

insect 

populations 

Honey bee 

acute contact 

LD50

Honey bee (Apis 

mellifera)

LD50 = >25 μg a.i./bee 

NOAEL = 25 μg a.i./bee

44295788;

Palmer and 

Beavers, 1994;

Acceptable

Honey bee 

acute oral 

LD50

Honey bee (Apis 

mellifera)

LD50 = >29.6 μg a.i./bee (3) 

NOAEL = 29.6 μg a.i./bee (3) 

44295789;

Palmer and 

Beavers, 1995;

Acceptable

Survival and 

growth of 

terrestrial 

plants 

Seedling 

Emergence Monocot: Onion 

(Allium cepa)

EC25 = 7.7x10-4lb a.i./A (4)

EC05 = 1.0 x 10-4lb a.i./A

44295783;

Chetram and Cone, 

1997;

Supplemental Dicot: Radish 

(Raphanus 

sativus)

EC25 = 7.1 x10-4lb ai/A

NOAEC = 0.001 lb a.i./A; EC05 = 

9.2 x10-5

Vegetative 

Vigor

Monocot: 

Ryegrass

(Lolium 

perenne)

EC25 = 0.0034 lb ai/A (5)

NOEC = 0.0020 lb a.i./A

44295784;

Chetram and Cone, 

1995;

Supplemental

Dicot: Radish 

(Raphanus 

sativus)

EC25 = 8.4 x10-5lb ai/A

NOAEC = 3.1 x 10-5lb a.i./A
19

1Product tested contained 98.9% active ingredient (Technical Grade); One female lost weight from Day 8 to 15.

2 Product tested contains 98.4 % active ingredient (Technical Grade).

3 Product tested contained >98.5% active ingredient (Technical Grade); reviewer adjusted reported LD50 value for purity.

4 Values based on most sensitive endpoint of dry weight. Study was not conducted using a TEP, rather tested using TGAI 

(98.4%) ; solutions prepared using deionized water. There is uncertainty in the EC25 value for the most sensitive dicot, radish, as 

the data for the most sensitive endpoint, dry weight, did not provide a reliable EC25 value as it was lower than the NOAEC 

value. 

5 Values based on most sensitive endpoint of dry weight. Study was not conducted using a TEP, rather tested using TGAI 

(98.4%); solutions prepared using deionized water. 

5.1.1 Avian Toxicity, Acute

Sulfosulfuron is classified as practically non-toxic to birds as the acute oral LD50 is >2,250 

mg a.i./kg-bw for both bobwhite quail and mallard ducks (MRID 44295768 and 44295769). In 

the bobwhite quail acute oral study, signs of toxicity were observed at the two highest test doses 

and an effect on body weight gain at the highest dose; therefore, the NOAEL for the bobwhite 

quail study was determined to be 810 mg a.i./kg-bw. No sublethal effects were observed in the 

mallard duck acute oral study. The 5-day subacute dietary LC50 value for the bobwhite quail and 

mallard duck is >5,570 mg a.i./kg-diet and >5,110 mg a.i./kg-diet, respectively, and therefore are 

classified as practically non-toxic (MRID 44295770 and 44295771). No sublethal effects were 

observed in the bobwhite quail study. A slight reduction in body weight was observed at the 

highest concentration tested for the mallard duck; therefore, the NOAEC (observed and not 

statistically derived due to lack of replication) is 3,000 mg a.i./kg-diet. In the previous Data 

Evaluation Record (DER), the reviewer based the toxicity values on the mean measured 

concentrations of the treated feed at test initiation. As Day 5 test dietary feed were analyzed to 

determine stability, these concentration values were included in determination of the overall 

mean measured dietary concentration and the LC50 and NOAEC values reported in this problem 

formulation reflect these changes.

Acute oral toxicity data with a passerine species was not available.

5.1.2 Avian Toxicity, Chronic

Two studies were available for evaluating the effects of chronic exposure to sulfosulfuron on 

birds. Adult bobwhite quail and mallard ducks were exposed to nominal dietary concentrations 

of 50, 250 and 1,250 mg a.i./kg-diet. For the bobwhite quail reproduction study, no observed 

effects on survival, growth or reproduction were observed at the highest concentration tested and 

the NOAEC value is 1,229 mg a.i./kg-diet (mean-measured) (MRID 4429572). For the mallard 

duck reproduction study, there was an effect on the body weight of 14-day old hatchlings at the 

highest concentration tested (MRID 4429573). Therefore, the chronic NOAEC for birds is 245

mg a.i./kg-diet, and the LOAEC is 1,221 mg a.i./kg-diet (mean-measured). In the previous avian 

reproduction DERs, the toxicity values were based on nominal concentrations. As diet 

concentrations were analyzed periodically throughout the test, an overall mean measured dietary 

concentration was calculated and the toxicity values reported in the problem formulation reflect 

this change.
20

5.1.3 Mammal Toxicity, Acute

The acute oral LD50 toxicity value for mammals using technical grade sulfosulfuron (based 

on a rat study) is > 5,000 mg/kg-bw (98.9 % a.i.) (MRID 44295737). One female lost weight 

between Day 8 and 15 (249 versus 252 grams); all other animals gained weighed during the 

study. Clinical findings included soft/mucoid stools on days 1-3 post dosing. The observed 

slight weight loss in one out of ten animals does not appear to indicate a treatment-related effect.

There were two reported acute oral rat studies using sulfosulfuron formulations. Both were 

limit tests and resulted in an acute LD50 value of > 5,000 mg/kg-bw. One study tested MON 

37532 (73.7% a.i.) and the other study tested MON 37525 (23.7% a.i.) (MRID 44295738 and 

MRID 45116102).

Sulfosulfuron is also not a mammalian dermal or skin irritant or skin sensitizer (MRIDs 

44295739, 44295743 and 44295739). It is a moderate eye irritant (MRID 44295741).

The HED CARC classified Sulfosulfuron as “Not Likely to be Carcinogenic to Humans” at 

doses that do not cause crystals with subsequent calculi formation resulting in cellular damage of 

the urinary tract. (MRID 44295759 and 44295755; Kidwell December 16, 2008). Sulfosulfuron

is not expected to be mutagenic.

5.1.4 Mammal Toxicity, Chronic

A 2-generation reproduction study with rats was available (MRID 44295758). The NOAEL 

is 5,000 mg/kg (312.1 mg/kg/day), based on decreased parental and offspring body weight gain, 

mortality in the parental males, and urinary tract pathology in parental generation observed at a 

concentration of 20,000 mg/kg (1,312.8 mg/kg/day) (LOAEL). 

5.1.4.1 Mammalian Metabolism Data

A metabolism study, with rats using radiolabelled sulfosulfuron (MON 37500) (98% a.i.) was 

available (MRID 44295765). More than 90% of the administered radioactivity was excreted by 

72 hrs post-dosing (mean total recovery ranged from 97% to 101%). Between 77 to 87% was 

excreted in the urine in the low doses, whereas feces were the major route of elimination at the 

high dose (55-63%). In all dose groups, minimal radioactivity was retained in tissues (less than 

0.07%) or carcass (less than 0.17%). Metabolism of MON 37500 in all groups was minimal and 

most was excreted unmetabolized (for example, it represented more than 90% of the total 

radioactivity excreted in the urine). MON 37500 was metabolized primarily via ring 

hydroxylation of the a-position carbon of the pyrimidine ring, or demethylation of the methoxy 

group at the 4- or 6-position of the pyrimidine ring. In addition, a limited amount of cleavage of 

the sulfonamide bond into sulfonamide or other imidazopyridine compounds and pyrimidine 

compounds was observed. Major metabolites identified in urine and feces were desmethyl MON 

37500 (3.6% or greater of administered dose), 5-hydroxy MON 37500 (1.9% or greater) and 

sulfonamide (2.6% or greater). A fourth, Feces 488 (ND-1.68%; feces only), was partially 
21

characterized as a desmethylated metabolite. Other minor metabolites, 1 imidazopyridine and 3 

pyrimidine metabolites, were also found at low levels (<1%) in the feces. 

5.1.5 Terrestrial Invertebrate Toxicity, Acute

The acute contact honeybee LD50 value is reported to be >25 μg a.i./bee (MRID 44295788). 

There were a few reported incidences of sublethal effects observed (i.e., loss of equilibrium, 

immobility) in the two highest treatment groups, but these incidences and overall mortality in the 

treatment groups was less than the controls. Therefore, the NOAEL is reported to be 25 μg 

a.i./bee.

An acute oral toxicity test with the honeybee is also available (MRID 44295789) for 

sulfosulfuron. The 48-hour acute oral LD50 was >29.6 μg a.i./bee. The NOAEL is reported as 

29.6 μg a.i./bee, as there was mortality observed at the highest dose tested, but was lower than 

reported in the negative control. The doses tested in this study were not adjusted for 

sulfosulfuron purity (98.5%), and the DER did not adjust the reported values for purity. 

Therefore, the doses were adjusted for purity and the toxicity values reported in this document 

reflect this change.

5.1.6 Terrestrial Plant Toxicity

Both a seedling emergence and a vegetative vigor study using sulfosulfuron were 

submitted by the registrant (MRID 44295783 and 44295784). These studies were conducted 

using technical grade sulfosulfuron (98.4%) which was dissolved in deionized water. Terrestrial 

plant studies conducted using a typical end-use product (TEP) were not available, and as 

sulfosulfuron is a herbicide there is uncertainty in how the other ingredients in the formulations 

may influence the overall toxicity to terrestrial plants. As such, the submitted studies were 

reclassified from Acceptable to Supplemental, and additional studies conducted using a TEP are 

requested. 

Based on the most sensitive species and endpoints reported, sulfosulfuron is more toxic to 

dicot terrestrial plants in the vegetative vigor study compared to the seedling emergence study. 

However, monocots appear to be more sensitive in the seedling emergence test than the 

vegetative vigor study. The seedling emergence EC25 for the most sensitive dicot (radish) and 

monocot (onion) are 7.1 x 10-4and 7.7x10-4lb a.i./A, respectively. The corresponding NOAEC 

or EC05 for these species is 1.0 x 10-4and 0.001 lb a.i./A, respectively. There is uncertainty in 

the EC25 value for the dicot, radish, as the data for the most sensitive endpoint, dry weight, did 

not provide a reliable EC25 value as it was lower than the calculated NOAEC value. As such, 

this uncertainty also contributed to the reclassification of the seedling emergence study. The dry 

weight values for onion and radish were re-calculated using Nuthatch and presented in a memo 

from EFED on March 4, 1999 (Erickson), and these values were used for reporting the EC25 and 

NOAEC/EC05 values..
22

The vegetative vigor EC25 for the most sensitive dicot (radish) and monocot (ryegrass) 

are 8.4 x 10 -5 and 0.0034 lb ai/A, respectively. The corresponding NOAEC for these species is 

3.1 x 10-5and 0.002 lb a.i./A, respectively. The dry weight EC25 and NOAEC/EC05 values for 

radish and ryegrass were re-calculated using the model Nuthatch. The guideline seedling 

emergence and vegetative vigor studies reported non-lethal effects of sulfosulfuron exposure on 

plants such as chlorosis, stunting, restriction of leaf expansion and apical meristem growth.

5.2 Aquatic Organism Toxicity Data

Table 9 summarizes the most sensitive ecological toxicity endpoints based on currently 

available data for aquatic organisms. A brief summary of submitted data considered relevant to 

this ecological risk assessment is presented below.
23

Table 9. Most Sensitive Aquatic Organism Toxicity Values for Sulfosulfuron Based on 

Available Data

Assessment 

Endpoint 

Measures of 

Effect 

Species Toxicity Value MRID Number; 

Reference; and 

Study 

Classification 

Survival and 

reproduction of 

individuals and 

communities of 

freshwater fish

Freshwater fish 

acute 96-hr LC50

Rainbow trout 

(Oncorhynchus 

mykiss)

LC50 > 93.6 mg a.i./L (1)

NOAEC = 93.6 mg a.i./L

44295774; 

Graves and 

Swigert, 1994; 

Acceptable

Freshwater fish 

early life-stage 

NOAEC

Rainbow trout 

(Oncorhynchus 

mykiss)

NOAEC = 100 mg a.i./L; highest 

concentration tested

44295779; 

Graves, Mank and 

Swigert, 1996; 

Acceptable

Survival and 

reproduction of 

individuals and 

communities of 

freshwater 

invertebrates 

Freshwater 

invertebrate 

acute 48-hr LC50

Water flea 

(Daphnia 

magna)

EC50 > 94.6 mg a.i./L (1)

NOAEC = 94.6 mg a.i./L

44295776; 

Graves and 

Swigert, 1994; 

Acceptable

Freshwater 

invertebrate 

reproductive 

NOAEC

Water flea 

(Daphnia 

magna)

NOAEC = 102 mg a.i./L; highest 

concentration tested

44295780; 

Graves, Mank and 

Swigert, 1996; 

Acceptable

Survival and 

reproduction of 

individuals and 

communities of 

estuarine and 

marine fish 

Estuarine and 

marine acute 

fish 96-h LC50

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

LC50 > 101 mg a.i./L

NOAEC = 101 mg a.i./L

44309304; 

Graves and 

Swigert, 1995; 

Acceptable

Estuarine and 

marine fish 

reproductive 

NOAEC

No Data Available; Using acute to chronic ratio (ACR):

NOAEC = 8.78 mg a.i./L (2); ECOSAR Fish Chronic Value = 20.9 mg/L

Survival and 

reproduction of 

individuals and 

communities of 

estuarine and 

marine 

invertebrates 

Estuarine and 

marine 

invertebrate 

acute

96-hr LC50

Mysid Shrimp 

(Mysidopsis 

bahia)

LC50 > 106 mg a.i./L 

NOAEC = 106 mg a.i./L

44295777; 

Graves and 

Swigert, 1995; 

Supplemental

Estuarine and 

marine 

invertebrate 

reproductive 

NOAEC

No Data Available; Using acute to chronic ratio (ACR) from other SU 

data: NOAEC = 5.73 mg a.i./L; Using ACR using ECOSAR Daphnia 

data: NOAEC = 9.8 mg/L (3)

Standing crop or 

biomass and 

growth of aquatic 

plants 

Freshwater 

green algae, 

cyanobacteria or 

diatom 120-h 

IC50 for biomass.

Green algae 

(Selenastrum 

capricornutum)

IC50 = 0.310 mg a.i./L 

(310 μg a.i./L) (4)

NOAEC = 0.093 mg a.i./L 

(93 μg a.i./)

Based on endpoint of area under 

the curve

44295785; 

Thompson and 

Swigert, 1995; 

Supplemental (not 

for quantitative use 

in risk assessment)

Vascular aquatic 

plants

Duckweed

(Lemna gibba)

EC50 ≈ 9.85 x 10-4 mg a.i./L 

(0.985 μg a.i./L) (5)

NOAEC = 4.9 x 10-4 mg a.i./L 

(0.49μg a.i./L) 

Based on Frond Number

44295787; 

Thompson and 

Swigert, 1996; 

Supplemental (not 

for quantitative use 

in risk assessment)
24

1 Technical Grate Active ingredient reported to be >98.5 % (Rainbow trout) or 98.5% (Daphnia); reviewer adjusted reported 

value for purity.

2 ECOSAR values for Imidazoles were Fish 96 hr LC50 – 240 mg/L and Fish Chronic Value of 20.9 mg/L; ACR = 240 ÷ 20.9 = 

11.5.

3 Acute to chronic ratio calculated using endpoints for ECOSAR value for Sulfonyl ureas were Daphnia 48-hr LC50 value of 558 

mg/L and a Daphnia Chronic Value of 51.6 mg/L; ACR = 558 ÷ 51.6 = 10.8; 106 ÷10.8 = 9.8 mg/L. ACR using 

chlorsulfuron (PC 118601) acute and chronic data: acute EC50 = 370 ppm (MRID 00035262) and chronic NOAEC = 20 

ppm (MRID 41976404), ACR = 370 ÷ 20 = 18.5; 106 ÷ 18.5 = 5.73 ppm

4 Technical Grate Active ingredient reported to be >98.5 %; reviewer adjusted reported value for purity. Most sensitive endpoint 

was area under the curve. Four out of the six concentrations tested were not analyzed during the study due to being below 

the LOQ, therefore nominal concentration were used. Therefore IC50 and NOAEC values fall within the range of 

concentrations that were not analyzed.

5 Technical Grate Active ingredient reported to be >98.5 %; reviewer adjusted reported value for purity (98.5). Most sensitive 

endpoint was frond number; dry weight was not reported. Frond number inhibition at highest concentration tested compared 

to the control was 50%, therefore there is uncertainty in the reliability of the EC50 value. All concentrations tested were not 

analyzed during the study due to being below the LOQ, therefore nominal concentration were used. Stock used to make test 

solutions analyzed but this stock was 1000 times greater than test concentrations. Therefore EC50 and NOAEC values based 

on concentrations that were not analyzed.

5.2.1 Fish Toxicity Data, Acute

Available acute toxicity data for freshwater and estuarine-marine fish indicate that 

sulfosulfuron is essentially practically non-toxic on an acute exposure basis (MRID 44295774, 

4429575, and 44309304). The practically non-toxic classification include LC50 values greater 

than 100 mg/L; however, for freshwater fish, there was no mortality observed at concentrations 

of 93.6 mg a.i./L or greater, therefore, sulfosulfuron classification is considered to be essentially 

practically non-toxic to freshwater fish. The LC50 values for the freshwater rainbow trout and 

bluegill sunfish are > 93.6 and 94.6 mg a.i./L, respectively. The LC50 value for the estuarinemarine sheepshead study was > 101 mg a.i./L. No sublethal effects were observed in any of the 

freshwater or estuarine-marine studies. The study report nor the DER adjusted the test 

concentrations for purity of sulfosulfuron for the rainbow trout or bluegill sunfish studies 

(98.5%), therefore, the reported toxicity values in this assessment are adjusted for purity. 

5.2.2 Fish Toxicity Data, Chronic

An early-life stage toxicity test was available for the freshwater fish, rainbow trout ( MRID 

44295779). The 60-day post hatch early-life cycle study resulted in a NOAEC value of 100 mg 

a.i./L, the highest concentration tested, as no adverse effects were observed. 

Chronic toxicity data for estuarine-marine fish was not available. As such, the acute to 

chronic ratio (ACR) method was used to estimate chronic toxicity for estuarine-marine fish. 

However, for sulfosulfuron, as a non-definitive acute toxicity value was reported for the rainbow 

trout in which a chronic NOAEC value was reported, the use of this toxicity data to establish an 

ACR is not appropriate. A search of toxicity data for other sulfonylureas was conducted using 

the EFED Ecotoxicity database, but no other chemical had both appropriate acute and/or chronic 

data (e.g., acute non-definitive toxicity values and/or no chronic data). The quantitative structure 

activity relationship model ECOSAR v1.00 (EPI suite, EPA 2008) was used to try to estimate 
25

chronic fish toxicity7. Using the acute sheepshead minnow data and an ECOSAR ACR of 11.5, 

an estimated chronic toxicity value for estuarine marine fish was 8.78 mg/L.8 This chronic value 

calculated using an ACR may be conservative as there was no mortality observed in the acute 

toxicity test at the limit dose, which was used in the derivation of the ACR, for the sheepshead 

minnow. Therefore, this acute limit dose does not accurately reflect a definitive LC50 value. 

5.2.3 Aquatic Invertebrate Toxicity Data, Acute

Both freshwater and estuarine-marine acute toxicity data was available (MRID 44295776, 

44297577 and 44295778). The reported freshwater, Daphnia magna, acute EC50 value was 

>94.6 mg a.i/L. The estuarine-marine, mysid shrimp, acute LC50 value was >106 mg a.i./L. 

Again, as with the fish, sulfosulfuron is considered to be classified as practically non-toxic to 

aquatic invertebrates. No sublethal effects were reported in either study. The exact age of the 

organisms used in the mysid shrimp study were not reported, rather that they were juveniles. As 

such, this study is classified as Supplemental, but could be upgraded with submission of 

acceptable information. In addition, for the Daphnia study, neither the study authors nor the 

DER adjusted the toxicity values for purity (98.5%); the toxicity value reported in this document 

has been adjusted for purity. An oyster shell growth study was also available (MRID 44295778). 

No effect on shell growth was observed at the limit concentration of 116 mg a.i./L compared to 

the control. No sublethal effects were reported.

Sediment organism acute (short-term) toxicity data was not available.

5.2.4 Aquatic Invertebrate Toxicity Data, Chronic

A chronic toxicity study with Daphnia magna was available (MRID 44295780). The 

reported NOAEC was 102 mg a.i./L, the highest concentration tested.

No chronic toxicity data was available for estuarine-marine invertebrates. As such, a similar 

approach was used as described above for estuarine-marine fish. The freshwater invertebrate data 

for sulfosulfuron is not appropriate to calculate an ACR due to the non-definitive acute toxicity 

value for the Daphnia. A review of toxicity data for other sulfonylureas indicated that the 

chemical, chlorsulfuron (PC 118601) had definitive acute and chronic freshwater toxicity data.9 

The estimated estuarine-marine invertebrate chronic toxicity value using the acute toxicity data 

and the chlorsulfuron ACR is 5.73 mg/L. The model ECOSAR was also used to evaluate chronic 

 

7 Based on the SMILES data for sulfosulfuron, ECOSAR returned fish toxicity data for two classes : imidazole (an 

aromatic heterocyclic diazole (five-membered ring consisting of three carbon atoms and two nitrogen atoms)) and 

amides (carbonyl group (R-C=O) linked to a nitrogen atom). The imidazole fish data was used to report chronic fish 

toxicity and calculate ACR. The chronic fish toxicity data reported in ECOSAR was predicted using an ACR.

8 The chronic fish toxicity value reported was 20.9 mg/L. The fish 96-hr acute LC50 value reported was 240 mg/L; 

ACR = 240 ÷ 20.9 = 11.5.

9 The acute 48-hr EC50 value is 370 mg/L (MRID 00035262), and the 21-day chronic NOAEC value is 20 mg/L 

(MRID 41976404); ACR = 370 ÷ 20 = 18.5
26

toxicity to estuarine-marine invertebrates. The estimated chronic toxicity value for estuarinemarine invertebrates using the acute mysid LC50 and the ECOSAR ACR is 9.8 mg/L.10

 Again, 

this calculated chronic value using the ACR may be conservative for the same reasons as 

described above for the chronic sheepshead minnow value.

Sediment organism chronic (long-term) toxicity data is not available.

5.2.5 Aquatic Plant Toxicity Data

Aquatic vascular plants appear to be more sensitive than any of the aquatic nonvascular 

plants tested. The 14-day EC50 and NOAEC for the freshwater vascular plant (Lemna gibba, 

duckweed) for frond count (most sensitive endpoint reported) was approximately 0.985 and 0.49 

μg a.i./L, respectively (MRID 44295777). A significant percentage increase in the number of 

dead and chlorotic frond at the highest concentration (0.985 μg a.i./L) was observed compared to 

the control. The frond number percent inhibition at the highest concentration tested (0.985 μg

a.i./L) was 50% compared to the control; therefore, there is uncertainty regarding the precision in 

the EC50 value. These toxicity values are based on nominal test concentration as none of the test 

concentrations were analyzed for sulfosulfuron due to the test levels being below the LOQ (0.75 

mg a.i./L). The stock (1.0 mg a.i./L) used to prepare the test solutions was analyzed at test 

initiation and was 97 – 100% of nominal. However, the same 1.0 mg a.i./L solution which was 

retained for 14 days to evaluate stability was 66% of nominal on Day 14. The test solutions were 

not renewed during the 14 day test duration. This stock solution is 1000 times greater than the 

highest concentration tested (1.0 μg/L; 0.985 μg a.i./L), therefore there is great uncertainty in the 

actual concentrations in the test system in which the duckweed where exposed to. In addition, 

dry weight was not reported which may have been a sensitive endpoint. As neither the study 

author nor the DER adjusted the test concentrations for purity, the reported values in the problem 

formulation were adjusted. Given the uncertainties in the actual exposure concentrations and the 

EC50 value, this study was reclassified as Supplemental, for qualitative use only. An additional 

study using Lemna gibba is requested.

Toxicity data was available for four different non-vascular plant species for sulfosulfuron 

(MRIDs: 44295781, 82, 85 and 86). The green-algae, Selenastrum capricornutum, was the 

reported most sensitive non-vascular plant tested with EC50 and NOAEC values of 310 and 93

μg a.i./L, respectively, based on the area under the curve endpoint. Four out of the six 

concentrations tested were not analyzed during the study due to being below the LOQ, therefore 

nominal concentration were used for these concentrations. The EC50 and NOAEC values fall 

within the range of test concentrations that were not analyzed. The measured concentrations for 

the two highest concentrations tested were 82 and 83% at test initiation and 64 and 86% at test 

termination. The DER reported the toxicity based on cell density alone and did not verify 

growth rate, area under the curve and yield. Therefore, these endpoints were analyzed using the 

EFED Nuthatch model. In addition, neither the study author nor the DER adjusted the test 

concentrations for purity; therefore the reported values in the problem formulation were adjusted. 

 

10 The acute 48-hr LC50 value for Daphnia for the sulfonyl urea class in ECOSAR was 558 mg/L and the chronic 

value was 51.6 mg/L; ACR = 558 ÷ 51.6 = 10.8.
27

Although, the measured test concentrations for the two highest concentrations were within 80-

120% of nominal at test initiation, given the stability at the highest concentration and relative 

instability at the next lower concentration there is uncertainty in the actual exposure 

concentrations in the remaining lower concentrations. Therefore, there is uncertainty in which 

approach is appropriate when determining how to report the exposure concentrations used for 

statistical analysis. As such this study is reclassified as Supplemental, for qualitative use only 

and an additional study is requested.

There were three other non-vascular toxicity studies conducted using sulfosulfuron. The 

reported EC50 value for the marine diatom, Skeletonema costatum, and the freshwater diatom, 

Navicula pelliculosa, is >103 and > 87 mg a.i./L, respectively. Particulates were observed in the 

solution used to make the test solutions for both studies and an effort to remove these particulates 

prior to analysis was not reported. Therefore, there is uncertainty in the actual exposure 

concentrations. The toxicity values for these studies will be reported as mg a.i. (total)/L to 

indicate the possibility of the measured values reporting both dissolved and undissolved test 

material. These studies were reclassified as Supplemental. However, given the large difference 

between the observed toxicity (>200 fold difference) in these two studies compared to the green 

algae or cyanobacteria, additional studies are not requested at this time. 

The final non-vascular aquatic plant study was conducted on cyanobacteria (blue-green 

algae), Anabaena flos-aquae, with a reported EC50 and EC05 value of 0.56 and 0.038 mg a.i./L or 

560 and 38 μg a.i./L, respectively, based on area under the curve endpoint. The DER reported the 

toxicity based on cell density alone and did not verify growth rate, area under the curve and 

yield. Therefore, these endpoints were analyzed using the EFED Nuthatch model. As with the 

two diatom studies, particulate matter was observed in the stock solution used to prepare the test 

concentrations, and methods to remove this material prior to analysis was not reported; therefore, 

the toxicity values will be reported as mg a.i. (total)/L. In addition, the two lowest test 

concentrations were not analyzed as they were below the LOD (1.0 mg a.i./L), and as such, both 

the calculated EC50 and EC05 fall within the concentration range that was not analyzed. The 

measured concentrations for the remaining test concentrations ranged from 100 to 106% of 

nominal, suggesting the sulfosulfuron was stable in the test system. As there was observed 

particulate matter, no measurement of the all test concentrations, and the most sensitive EC50 

value is close to the reported EC50 value of the most sensitive non-vascular species test, an 

additional tested with Anabaena flos-aquae is requested. This is to better ensure that the most 

sensitive endpoint for the most sensitive non-vascular species is used in the risk assessment. 

This study was reclassified as Supplemental.

6.0 Evaluation of Non-definitive Toxicity Values

All of the acute terrestrial and aquatic animal studies resulted in non-definitive toxicity 

values. In an effort to determine whether additional data is needed to evaluate risk to these taxa, 

a comparison of the non-definitive toxicity value to either an aquatic EEC or terrestrial EEC was 

conducted. According the current registered sulfosulfuron labels, the maximum annual 

application rate is 0.125 lb a.i./A (EPA Reg # 524-534, 524-500, and 524, 533). This is slightly 

more than the maximum single application rate of 0.094 lb a.i./A (EPA Reg # 524-534 and 524-
28

500). Although the maximum annual rate is slightly higher, it will provide conservative EEC 

values to compare to the toxicity data.

GENEEC2 (US EPA, 2001) was used to estimate the parent sulfosulfuron concentrations in 

surface water for aquatic exposure to fish and invertebrates. GENEEC2 estimates the peak value 

which occurs on the day of the single large rainstorm as well as multiple day averages over 

periods of 4, 21 and 60 days. These averages are appropriate for comparison with toxicity tests 

currently performed. A single application rate of 0.125 lb a.i./A was used as the application 

input. The Tier I EECs for parent sulfosulfuron are 6.8, 5.2, and 4.6 μg a.i./L, the peak, the 21-

day and the 60-day averages, respectively. The output file is presented in Appendix D.

The lowest acute non-definitive toxicity values for freshwater fish (rainbow trout) and 

estuarine-marine fish (sheepshead minnow) are 93.6 and 101 mg a.i./L, respectively. The lowest 

non-definitive toxicity values for freshwater invertebrates (Daphnia magna) and estuarinemarine invertebrates (mysid shrimp) are 94.6 and 106 mg a.i./L, respectively. No sublethal 

effects were observed at these concentrations. The calculated peak EEC concentration is 6.8 μg 

a.i./L. As such, the non-definitive toxicity values for fish and invertebrates are > 10,000 times 

the peak EEC.11

For terrestrial animals, the model T-REX v1.4.1 (US EPA, 2008) was used to model 

sulfosulfuron residues on terrestrial plants and insects. A single application rate of 0.125 lb 

a.i./A was used as the input application rate. The maximum upper-bound dietary based EEC for 

birds and mammals is 30 mg a.i./kg-diet. The maximum upper-bound dose based EEC for birds 

(20-g) is 34.17 mg a.i./kg-bw; the maximum upper-bound dose based EEC for mammals (15-g) 

is 28.60 mg a.i./kg-bw. The upper-bound EEC for small insects is 16.88 mg a.i./kg. The output 

file is presented in Appendix E.

The lowest acute non-definitive values for birds are 2,250 mg a.i./kg-bw for acute oral and 

5,110 mg a.i./kg-diet for subacute dietary; the corresponding NOAEL or NOAEC values for 

these studies is 810 mg a.i./kg-bw and 3,000 mg a.i./kg-diet, respectively. The acute nondefinitive value for mammals is 5,000 mg a.i./kg-bw. As the acute oral toxicity values are based 

on body weight, the NOAEL value for the avian acute oral and the non-definitive mammal value 

were entered into T-REX to obtain the adjusted toxicity value for the small weight bird or 

mammal assessed in T-REX. The adjusted toxicity value for birds (20-g) is 584 mg a.i./kg-bw, 

and for mammals (15-g) is 10,989 mg a.i./kg-bw. The acute toxicity values for birds and 

mammals are at least 17 times the EEC.12

The non-definitive acute contact honeybee value is presented in μg a.i./bee and therefore can 

not be directly compared to the EECs. The toxicity value was converted to mg/kg by dividing 

the value by the weight of one bee (0.128 g) which calculates to a toxicity value of 195 mg 

a.i./kg (Mayer and Johansen, 1990). This toxicity value is approximately 11.5 times the EEC. 

The acute oral toxicity study with honeybees also resulted in a non-definitive endpoint. 

Currently, there is not a formalized process in EFED by which to evaluate risk from oral 

pesticide exposure to honeybees or other terrestrial invertebrates. One approach to evaluate risk 

 

11 For the lowest acute aquatic value of 93.6 mg a.i./L (rainbow trout): 93,600 ÷ 6.8 = 13,765

12 For the lowest ratio for acute terrestrial animals (acute avian oral): 584 ÷ 34.2 = 17
29

to at least terrestrial invertebrates that consume plants is to convert the reported toxicity value 

from μg a.i./bee to a dietary based endpoint (mg a.i./kg) by using the sucrose solution that the 

bees fed upon. In this study, 300 mg of test material was added to obtain a final volume of 100 

mL in a 50% sucrose solution. Therefore, the concentration was 300 mg/100 mL or 3,000 

mg/kg. If adjusted for purity (98.5%), the value is 2,955 mg a.i./kg. A comparison of this value 

to the residue concentration for short grass, (highest EEC) could be conducted. The calculated 

short grass EEC, based on current application rates, is 30 mg a.i./kg. The calculated toxicity 

value is approximately 100 times greater than the calculated EEC. 

Therefore, based on these comparisons of toxicity values to calculated EECs using the 

currently registered labels, additional toxicity data for these endpoints is not requested at this 

time. If application rates change in the future, then this may need to be re-evaluated.

7.0 Uncertainties Associated with Lack of Data or Acceptable 

Studies

7.1 Parent Sulfosulfuron

Terrestrial plants appear to be very sensitive to sulfosulfuron 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 

evidence to suggest plant reproduction may be affected by sulfonylurea herbicides at levels 

below effects on vegetative growth or visual injury (Asghari and Evans, 1992; 1993; Bhatti et. 

al., 1995; Boutin et. al. 2000; Fletcher, 1993, 1995, 1996). Uncertainty regarding the potentially 

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

environmental fate and effects assessment for chlorsulfuron (US EPA, 2005). Although there is 

no firm evidence for sulfosulfuron causing reproductive impairment, reproductive impairment 

cannot be discounted without data. Therefore, to the extent that terrestrial plant reproduction are 

more sensitive to sulfosulfuron than growth endpoints, risks to terrestrial plants may be 

underestimated if risks are based solely on growth endpoints. Additional information on the 

reproductive toxicity of sulfosulfuron to terrestrial plants would help address this uncertainty.

In addition, both of the registrant submitted vegetative vigor and seedling emergence tests 

were conducted using the technical grade active ingredient only and not a typical end-use 

product (TEP). Current guidance (40 CFR Part 158.660) requires terrestrial plant toxicity testing 

to be conducted using a TEP as plants may be exposed to other components in a TEP as well as 

the active ingredient. Furthermore, as sulfosulfuron is a herbicide, there is concern and 

uncertainty in how the other ingredients in the TEP may influence or affect the toxicity to 

terrestrial plants. Therefore, additional Tier II vegetative vigor and seedling emergence toxicity 

studies using a TEP are requested. This additional data will be used to help refine the risk to 

terrestrial plants by evaluating toxicity from exposure to a sulfosulfuron typical end-use product.

Acceptable acute avian oral toxicity data were not submitted for a passerine species exposed 

to sulfosulfuron. The available acute oral toxicity data for mallard ducks and bobwhite quails, 

when compared to estimated environmental concentrations, indicate that levels of concern are 

not exceeded for birds on an acute basis. Because passerine species have higher metabolic rates 
30

due to their smaller sizes than either waterfowl or upland game bird species and because they 

may utilize different metabolic pathways, they may be more sensitive to sulfosulfuron. In 

addition, for the acute oral study with bobwhite quail, signs of toxicity were observed at the two 

highest test doses and an effect on body weight gain at the highest dose. Therefore, there were 

some effects on birds observed after acute oral exposure to sulfosulfuron. In order to 

characterize risk to passerines, an avian oral toxicity test is required for passerine birds. This 

additional data will be used to refine the screening-level risk assessment by determining whether

there are differences in avian species sensitivity to sulfosulfuron between passerine and currently 

tested upland game and/or waterfowl species that are beyond the simple allometric predictions 

currently employed in the absence of such passerine data. The current extrapolation method may 

be under- or over-estimating risks to passerines.

There is uncertainty in the available toxicity data for aquatic vascular and non-vascular 

plants. For the aquatic vascular plant toxicity data (i.e., Lemna gibba), none of the test 

concentrations were analyzed; therefore, there is uncertainty in the actual exposure 

concentration. In addition, at the highest concentration tested, only 50% inhibition was observed 

therefore, the EC50 value is an approximate value. For the reported most sensitive non-vascular 

aquatic species, the green algae, the EC50 and the NOAEC values fall within the range of test 

concentrations that were not analyzed. In addition, for the cyanobacteria species, Anabaena flosaquae, particulate matter was observed, the EC50 and EC05 values fall within range of test 

concentrations that were not measured. Therefore, again, there is uncertainty in the actual 

exposure concentrations for these two non-vascular studies. As the EC50 value for cyanobacteria 

is close to the EC50 value for green algae, there is uncertainty in which species may be more 

sensitive to sulfosulfuron exposure. Due to the fact that aquatic vascular and non-vascular plant 

species are sensitive to sulfosulfuron exposure, and sulfosulfuron is applied in many different 

scenarios where drift or runoff is expected to enter aquatic ecosystem, there is uncertainty in 

whether the reported toxicity data are appropriate for evaluating risk.

If the registration review risk assessment, including listed species assessments, is performed 

without these data discussed above, the Agency would have to assume that sulfosulfuron “may 

affect” these taxa directly (and listed species from other taxa indirectly), and use of sulfosulfuron

and its formulated products may need to be restricted in areas where listed species could be 

exposed. The lack of these data will limit the flexibility the Agency and registrants have in 

complying with the Endangered Species Act and could result in restrictions for sulfosulfuron use 

that might prove to be unnecessarily severe, therefore this data is requested to address this area 

of uncertainty.

Chronic toxicity data was not available for estuarine-marine fish and invertebrates, and given 

that sulfosulfuron is registered for use in turf areas (e.g., golf courses and hotel properties), 

application of sulfosulfuron may occur near estuarine-marine ecosystems. Risk to these taxa 

from chronic exposure to sulfosulfuron were calculated using acute to chronic ratios using data 

from ECOSAR for the fish and invertebrates and from sulfonylurea chemical specific 

information for the invertebrates. For the chronic fish toxicity value, there is uncertainty in using 

this modeled data as it was from the imidazole chemical class (an aromatic heterocyclic diazole 

(five-membered ring consisting of three carbon atoms and two nitrogen atoms). While 

sulfosulfuron contains a five-membered ring with two nitrogen atoms, it is attached to a six 
31

membered ring, therefore, there is some uncertainty in whether the imidazole class is wholly 

appropriate. However, it was deemed to be sufficiently appropriate and therefore was used for 

evaluating chronic risk to estuarine-marine fish. Based on the available toxicity data, risk to 

estuarine-marine fish and invertebrates is expected to be low and chronic toxicity data is not 

requested at this time. This is based on several lines of evidence. First, toxicity to freshwater 

fish and invertebrates from chronic exposure to sulfosulfuron is expected to be low based on the 

chronic toxicity data for these taxa and the estimated environmental concentrations, as the 

NOAEC values are at least 19,000 times greater than the EECs. Second, using data from other 

chemicals and/or the ECOSAR model to estimate chronic toxicity values for estuarine-marine 

fish and invertebrates also show that these estimated toxicity values are at least 1000 times 

greater than the EECs. Finally, there is no additional evidence at this time that would indicate 

that estuarine-marine fish and invertebrates are expected to be more sensitive to chronic 

sulfosulfuron exposure than freshwater fish and invertebrates. In the absence of this data, the 

chronic toxicity values for the freshwater fish and invertebrate may be used for estuarine-marine 

animals.

In addition, toxicity data for sediment-dwelling organisms is also not available. However, 

risk to these organisms is expected to be low. Although the fate data indicates that the half-life 

of sulfosulfuron in soil and the aquatic environment is expected to be greater than 10 days (40 

CFR Part 158 trigger for chronic sediment testing), sulfosulfuron is not expected to partition to 

the sediment but rather is expected to be mobile (Koc = 33.2 mL/g; Kads = 0.29 mL/g). In 

addition, sulfosulfuron is not expected to bioaccumulate as the Log Kow values range from -1.37 

to 0.81. Therefore, sediment toxicity testing is not triggered under 40 CFR Part 158. Also, 

sulfosulfuron is classified as acutely practically non-toxic to other aquatic animals and the 

chronic toxicity data also indicates low toxicity based on available data.

7.2 Degradate/Metabolites of Sulfosulfuron

Degradate or metabolite toxicity data were not available for any taxa. Several metabolites 

have been identified as residues of concern by HED; sulfonamide metabolite, sulfonic acid, and 

sulfone (Section 3.1). Sulfosulfuron and the residues of concern (metabolites) were all 

considered and converted to the common ethyl sulfone moiety, 2-(ethylsulfonyl)-imidazo[1,2-

a]pyridine. The sulfonamide (2-(ethylsulfonyl)-imidazo[1,2-a]pyridine-3-sulfonamide) was 

identified as both a major degradate and a residue of concern for human health, and limited fate 

data is available for this residue. Therefore, this total toxic residue (TTR) approach is 

anticipated to be undertaken by EFED when assessing exposure to non-target aquatic animals. 

Although there are no degradate/metabolite toxicity data available, additional toxicity data 

for these residues is not requested at this time for terrestrial or aquatic animals. Sulfosulfuron is 

classified as practically non-toxic on an acute basis for terrestrial and aquatic animals. The 

registrant submitted acute toxicity studies resulted in non-definitive acute toxicity 

LD50/LC50/EC50 values and a comparison of these non-definitive values for acute values or 

chronic NOAEC values to predicted exposure concentrations demonstrated that in these toxicity 

values were substantially greater than the EECs (fish and invertebrates – approximately 14 times

on an acute basis and 20 times on chronic basis; birds – at least 47 times on an acute basis and 8 
32

times on a chronic basis; mammals approximately 380 times on an acute basis and at least 24 

times on a chronic basis). 

However, sulfosulfuron is observed to be quite toxic to terrestrial and aquatic plants. 

Therefore, there is uncertainty in whether the observed degradates may also cause adverse effects 

to terrestrial and aquatic plants. Therefore, the structure and their percent formation in 

environmental fate studies were examined. Degradates/metabolites/residues that retained all or 

part of the sulfonyl urea (SU) moiety and were formed at 10% or greater (potential major 

degradate) in one or more environmental fate studies were examined and are presented along 

with their percent formation in various fate studies (Table 7).

Non-target organisms may be exposed to parent sulfosulfuron and its degradates/metabolites 

through spray drift and/or runoff. Environmental processes such as hydrolysis, photolysis and 

aerobic metabolism may facilitate the generation of sulfosulfuron degradates/metabolites that 

may then be present in runoff and/or in spray drift and expose non-target areas such as adjacent 

fields and water systems. Based on the information in Table 7, it appears that the processes of 

hydrolysis and aquatic photolysis as well as aerobic soil metabolism generate the majority of the 

major degradates (>10%). Several degradates were observed in the anaerobic aquatic 

metabolism study; however, the degradates formed under this process are anticipated to be less 

environmentally relevant for the taxa of concern. 

The calculated aqueous photolysis half-life of parent sulfosulfuron is reported to be 2.5 days 

and several major degradates are formed. While photolysis of sulfosulfuron on leaf surfaces of 

terrestrial plants could be expected to occur, the rapid rate of absorption of the parent compound 

into the plant is anticipated to mitigate the formation of photolysis degradates. 

The calculated aqueous photolysis half-life of parent sulfosulfuron is reported to be 2.5 days, 

Several major degradates were observed in the aqueous photolysis study. Formation of any 

degradates greater than 10% was not observed until at least the 24 hour sampling period. 

In the aquatic environment, plants may be exposed to the photo-degradates. Six degradates 

that formed at ≥ 10% were observed in laboratory aqueous photolysis studies with a range of 

formation from 10 to 28%. The first observance of the majority of the degradates at ≥ 10% 

occurred between 24 and 72 hours during the 6 day study. Formation of several of these 

degradates were still increasing at the end of the study. For the degradate aminopyrimidine, 

formation of 10% was measured at 48 hours and increasing to 28% by the end of the study. For 

sulfamic acid, formation was 13.8% at 48 hours and 21% at day 6; for oxamic acid formation of 

11% was measured at 96 hours and increased to 15.6% at test termination. For sulfone, 

formation of 14.3% was measured at 24 hours and was 21% at test termination with a peak 

measurement of 28.3% at 96 hours. For the other two degradates formation greater than 10% 

occurred for either 48 or 72 hours and peaked during the duration of the test, (sulfonic acid 

12.7% at 72 hours, 14.6% at 96 hours and 13.3% at day 6; N-hydroxy urea 13.3% at 24 hours, 

15% at 48 hours and 11.3% at 72 hours). Therefore, with the possibility of exposure to these 

photodegradates, further investigation was warranted for aquatic plants.
33

An evaluation of the potential toxicity of these degradates to aquatic plants was examined 

using the QSAR program ECOSAR. Green algae toxicity values can typically be obtained using 

ECOSAR. ECOSAR gave toxicity values for the classes of: anilines13, amides14, phenols15 and 

neutral organics – acid. It also listed imidazoles however, green algae toxicity values were not 

listed for this ECOSAR class. The 96- hour EC50 green algae toxicity values for the other groups 

ranged from 1.9 to 74 mg/L. The report also indicated that for the anilines, N-substituted 

anilines are less toxic than predicted by these SARs, which would correspond to these 

degradates. Furthermore, in a study by Liping Wei et. al., 1998, three sulfonyl ureas and their 

main degradates were tested using green algae in 96 hour assays. The study reported that the 

parent sulfonyl ureas were more toxic than the degradates by about 2 to 3 orders of magnitude. 

Therefore, based on this paper and the ECOSAR data it appears that for non-vascular plants the 

degradates may not be as toxic as parent sulfosulfuron.

However, as discussed above for parent sulfosulfuron there is uncertainty as to whether the 

chemical classes in ECOSAR are appropriate when trying to evaluate plant toxicity from 

sulfosulfuron degradates as these classes contain relatively basic chemical structures found in 

some of the degradates but do not fully represent the structure of the degradates. Moreover than 

the ECOSAR compatibility, based on the Lemna study, aquatic vascular plants are more 

sensitive to sulfosulfuron than non-vascular plants (i.e. green algae). Therefore, there is 

uncertainty on whether the evaluation of green algae toxicity data is adequate to bridge to aquatic 

vascular plants..

For three of the observed degradates in the aqueous photolysis study the percent formation 

was still increasing when the study was terminated; aminopyyrimidine, sulfamic acid and oxamic 

acid; therefore it is unknown what the maximum percentage formed under these conditions may 

have been. In addition, for sulfone, formation of greater than 10%, with a peak of 28%, was 

observed for five of the six days suggesting that this degradate may be persistent enough to be 

available for uptake by aquatic plants. Toxicity data for aquatic vascular plants (Lemna) is 

requested for these four degradates. If toxicity data are not available when the risk assessment is 

prepared, a total toxic residue (TTR) approach is anticipated to be undertaken for aquatic 

vascular plants. As the percent formation for the other two degradates, sulfonic acid and Nhydroxy urea, ranged from 11.3 to 14.6% for 48 or 72 hours and peaked during the assays, these 

degradates are not anticipated to impact the overall exposure and toxicity to aquatic vascular 

plants; therefore toxicity data for these degradates are not requested at this time

For the desmethyl degradate, it is structurally very similar to parent sulfosulfuron. In the 

aerobic aquatic metabolism study, 14 and 13% formation was observed at 30 days, with less than 

10% observed at the 14 and 61 sampling periods. Given the time between sampling periods it is 

not known how long or at what percentage this degradate was present in the system. As this 

degradate is very similar to the parent, it may exhibit similar toxicity to aquatic vascular plants. 

As such, an aquatic vascular plant toxicity test for this degradates is requested. As stated above 

if this data is not available, then a TTR approach is expected to be undertaken.

 

13 Anilines (aromatic amines) – phenyl group attached to an amino group

14 Amides – carbonyl group (R-C=O) linked to a nitrogen group

15 Phenols – phenol bonded to a hydroxyl group
34

The additional studies requested for each of the degradates is described in Section 16.0.

8.0 Incident Database Review

A preliminary review was made on March 22, 2011 of the Ecological Incident Information 

System (EIIS, version 2.1), which is maintained by the Agency’s Office of Pesticide Programs, 

and the Avian Monitoring Information System (AIMS), which is maintained by the American 

Bird Conservancy. No incidents were found in the EIIS or AIMS database. 

In addition to possible incidents recorded in EIIS, additional incidents may be reported to the 

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

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 sulfosulfuron, 

no minor incidents were reported in the database (accessed March 22, 2011).

In the risk assessment, these databases will be checked again and any incidents reported will 

be further evaluated to determine if the reported incidents represent current patterns of use for 

sulfosulfuron. 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 incident(s).

9.0 Monitoring Data

The US Geological Survey (USGS), reports that sulfosulfuron has been detected in the 

drinking water facilities at four locations (see Table 10). The data show the percent of the total 

number of samples in which the herbicide was detected and the maximum concentration 

observed at that location. 
35

Table 10. Detection Frequency and Maximum Concentration of Sulfosulfuron at Four 

Drinking Water Facilities 

Reservoir Location Concentration at 

Water-supply Intake

Concentration at 

Reservoir Outflow 

Site

Concentration of 

Treated Effluent

Detection 

%

Max 

Conc. 

(ppb)

Detection 

%

Max 

Conc. 

(ppb)

Detection 

%

Max 

Conc. 

(ppb)

Indianapolis Water 

Co., IN

- - - - 5 0.04

Higginsville 

Reservoir, MO

11 0.018 10 0.026 - -

East Fork Lake, OH 47 0.05 36 0.021 - -

Lake Mitchell, SD 5 0.021 11 0.023 9 0.026

Source: USGS Open file report 01-456 (Pesticides in Selected Water-Supply Reservoirs and Finished 

Drinking Water, 1999-2000: Summary of results from a Pilot Monitoring Program)

The National Water-Quality Assessment (NAWQA) Program database was searched (July 

2010) for the latest surface and groundwater monitoring results for sulfosulfuron. Sulfosulfuron 

has been monitored for in 42 states where there have been 82 samples where the herbicide has 

been found to be above detection limits. In these incidences the concentrations have ranged from 

0.010 to 0.870 ppb. There is no sulfosulfuron water concentration data listed in the USEPA 

STORET database.

10.0 Clean Water Act

Sulfosulfuron is not identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5. In addition, no Total Maximum Daily Loads (TMDL) has been developed for sulfosulfuron, 

based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES. More information on impaired water bodies and 

TMDLs can be found at http://www.epa.gov/owow/tmdl/.

The Agency invites submission of water quality data for this pesticide. To the extent 

possible, data should conform to the quality standards in Appendix A of the OPP Standard 

Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in 

OPP’s Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments. 
36

11.0 Ecosystems Potentially at Risk

The ecosystems 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 down stream from 

the treated field and could include impounded bodies such as ponds, lakes and reservoirs, or 

flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also 

includes marine ecosystems, including estuaries. 

12.0 Assessment Endpoints

Assessment endpoints are defined as “explicit expressions of the actual environmental value 

that is to be protected.” Defining an assessment endpoint involves two steps: 1) identifying the 

valued attributes of the environment that are considered to be at risk; and 2) operationally 

defining the assessment endpoint in terms of an ecological entity (i.e., a community of fish and 

aquatic invertebrates) and its attributes (i.e., survival and reproduction). Therefore, selection of 

the assessment endpoints is based on valued entities (i.e., ecological receptors), the ecosystems 

potentially at risk, the migration pathways of pesticides, and the routes by which ecological 

receptors are exposed to pesticide-related contamination. The selection of clearly defined 

assessment endpoints is important because they provide direction and boundaries in the risk 

assessment for addressing risk management issues of concern. Changes to assessment endpoints 

are typically estimated from the available toxicity studies, which are used as the measures of 

effects to characterize potential ecological risks associated with exposure to a pesticide, such as 

sulfosulfuron.

To estimate exposure concentrations, the ecological risk assessment considers applications at 

maximum rates. If multiple applications are allowed, the maximum amount per application and 

minimum interval between applications are used – provided that maximum total annual 

application amounts are also included in this configuration. Several EFED exposure models 

(e.g., PRZM-EXAMS, T-REX) are used to estimate likely high-end exposure to sulfosulfuron. 

The most sensitive toxicity endpoints are used from surrogate test species to estimate treatmentrelated direct effects on acute mortality and chronic reproductive, growth and survival 

assessment endpoints. Toxicity tests are intended to determine effects of pesticide exposure on 

birds, mammals, fish, terrestrial and aquatic invertebrates, and plants. These tests include shortterm acute, sub-acute, and reproduction studies and are typically arranged in a hierarchical or 

tiered system that progresses from basic laboratory tests to applied field studies. The toxicity 

studies are used to evaluate the potential of a pesticide to cause adverse effects, to determine 

whether further testing is required, and to determine the need for precautionary label statements 

to minimize the potential adverse effects to non-target animals and plants.
37

13.0 Conceptual Model

The conceptual model depicts the potential pathways for ecological risk associated with 

sulfosulfuron use. The conceptual model provides an overview of the expected exposure routes 

for terrestrial and aquatic organisms. 

The potential exposure pathways and effects of sulfosulfuron on terrestrial environments are 

depicted in Figure 3 and for aquatic environments in Figure 4. Figure 5 depicts exposure from 

drinking water and inhalation to terrestrial vertebrates and invertebrates. Solid arrows depict the 

most likely routes of exposure and effects; dashed lines depict potential routes of exposure that 

are not considered likely for sulfosulfuron. 
* See Figure 4 for drinking water and inhalation exposure pathways for terrestrial vertebrates and ingestion of residues in dew by terrestrial invertebrates. 

Stressor

Source

Attribute

Change

Sulfosulfuron applied to use site by ground or aerial application

Direct

application

Spray drift

Terrestrial 

vertebrates*

Terrestrial 

Inverts*

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in prey and food

Modification of PCEs

related to prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related

to habitat

Terrestrial plants

grasses/forbs, fruit, seeds 

(trees, shrubs)

Runoff

Terrestrial 

vertebrates* 

Exposure Media 

& Receptors Soil

Ingestion

Ingestion

Dermal uptake/Ingestion

Atmospheric 

transport

Root uptake/contact

Wet/dry deposition

Ingestion

Leaching to

Groundwater

Irrigation 

water

From 

Ingestion

Figure 3. Conceptual Model Depicting Potential Risks to Terrestrial Animals and Plants from the Use of Sulfosulfuron
39

Stressor

Source

Receptors

Attribute

Change

Sulfosulfuron and/or degradates applied to use site by ground or aerial 

application

Spray drift

Aquatic animals

Invertebrates 

Vertebrates 

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in algae and 

vascular plants

Reduction in prey

Modification of PCEs

related to prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related to 

habitat

Surface water/

Sediment

Runoff

Aquatic Animals

Invertebrates

Vertebrates

Exposure

Media

Uptake/gills 

or integument

Ingestion Ingestion

Atmospheric 

transport

Wet/dry deposition

Soil Leaching to

Groundwater

Uptake/gills 

or integument

Aquatic Plants

Non-vascular

Vascular

Uptake/cell, 

roots, leaves Riparian plants

terrestrial 

exposure 

pathways see 

Figure 2

Through changes in 

plants

Direct 

effects

Figure 4. Conceptual Model Depicting Potential Risks to Aquatic Animals and Plants from the Use of Sulfosulfuron
40

Stressor

Source

Attribute

Change

Sulfosulfuron and/or degradates applied to use site by ground or aerial 

application

Direct

application

Spray drift

Terrestrial 

vertebrates

Terrestrial 

invertebrates

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in prey and food

Modification of PCEs

related to prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related

to habitat

Runoff

Exposure Media Dew (formed on 

terrestrial plants)

Atmospheric 

transport

Receptors

Puddles (formed 

on treated fields)

Inhalation Ingestion

Air

Through 

ingestion

Figure 5. Conceptual Model Depicting Potential Risks to Terrestrial Vertebrates and Invertebrates from Inhalation and Drinking 

Water Exposure from the Use of Sulfosulfuron
14.0 Risk Hypothesis

Based on an examination of the physical/chemical properties of sulfosulfuron, its fate and 

disposition in the environment, and its mode of application, a conceptual model was developed 

that represents the possible relationships between this pesticide as a stressor, ecological 

receptors, and the assessment endpoints. 

Although transport of the compound through runoff and/or erosion is likely to be limited by 

low application rates, sulfosulfuron is mobile and is expected to be transported to surface and 

groundwater by run-off or leaching. Laboratory and field studies indicate that sulfosulfuron will 

persist for sufficient periods (days to weeks) to be available for transport off-site. 

Figure 3 indicates that the greatest potential exposure to aquatic plants and animals is most 

likely through spray drift and runoff. Depending on the extent of spray drift contamination, 

plants in aquatic environments will likely be affected. Because sulfosulfuron is classified as 

practically nontoxic to aquatic animals on an acute basis and rate of application is very low, 

minimal adverse effects are anticipated to aquatic animals; based on current application rates and 

available data, the acute toxicity values are at least 10,000 times greater than the parent 

sulfosulfuron EECs. Chronic adverse effects are not anticipated for aquatic animals because the 

low application rates are not likely to result in sufficient exposure to be a concern to aquatic 

animals. Based on the lowest chronic NOAEC value for fish and invertebrates identified above, 

8.78 and 5.73 mg a.i./L, respectively, and the 60-day and 21-day EEC values of 4.6 and 5.2 μg 

a.i./L, respectively, the chronic toxicity values are at least 1000 times greater than the parent 

sulfosulfuron EEC values. Due to the low application rates and low chronic toxicity endpoints, 

chronic effects to freshwater fish and aquatic invertebrates are not expected to occur from 

exposure to sulfosulfuron.

Figure 4 indicates that the greatest potential exposure to terrestrial plants and animals is most 

likely through direct application, spray drift and runoff. Sulfosulfuron is practically non-toxic to 

birds and mammals on an acute exposure basis, and the application rates are relatively low. As a 

result, direct acute risk to terrestrial animals has not exceeded concern levels in previous 

assessments. Based on the available data, chronic risk to birds and mammals potentially is 

expected to be minimal, except potentially from drinking water (see discussion below). Using 

the toxicity data identified in Section 5.1.2 and 5.1.4 and the calculated TREX EECs, the toxicity 

values are at least 8 times greater than the EECs. However, data in passerine species are being 

requested to address data gaps in the acute avian database. Therefore, no definitive risk 

conclusions can be made with respect to birds until those data are submitted. A comparison 

between the non-definitive acute contact honeybee study and the EEC indicate that the toxicity 

value is at least 11.5 times greater than the EEC. While no formalized process for evaluating 

potential for risk from oral exposure currently exists, if no formal approach exists when 

conducting the risk assessment, the approached discussed in Section 6.0 will be used.

In addition, exposure to piscivorous birds and mammals via the food chain is another 

potential exposure route to animals. However, given that sulfosulfuron is not expected to 
42

bioaccumulate based on the Log Kow of -1.37 to 0.81, risk to these animals from this exposure 

route is not expected, and therefore, this exposure route is not reflected in Figure 4.

Exposure through drinking water is another potential exposure route and is presented in 

Figure 5. The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to 

calculate an upper bound estimate of exposure using Sulfosulfuron’s solubility (1627 ppm, pH 

7), the most sensitive acute and chronic avian toxicity endpoints (Bobwhite Quail with LD50

>2250 mg/kg-bw and mallard duck NOAEC = 250 ppm, respectively) and the most sensitive 

acute and chronic mammalian toxicity endpoints (Rat LD50 >5000 mg/kg-bw and NOAEL = 312

mg/kg-bw, respectively). Based on the output, exposure through drinking water alone is 

potential acute and chronic risk to small birds and a potential chronic risk to small mammals.

Although, due to the use of the non-definitive acute values where no mortality was observed at 

those reported levels, the potential for acute risk is expected to be quite conservative. The output 

generated by SIP v.1.0 is presented in Appendix F.

Inhalation is another potential exposure route for terrestrial vertebrates. Based on the vapor 

pressure of sulfosulfuron, volatilization is not expected, and therefore risk from inhalation is not 

expected. The 4-hr LC50 inhalation study using rats was a non-definitive value in that no 

mortality was observed at 3.0 mg/L (MRID 44295745). The STIR model (Screening Tool for 

Inhalation Risk) was used to evaluate inhalation risk to birds. The non-definitive acute oral 

values for both birds and mammals were used in the model. Based on STIR , risk to birds from 

inhalation alone is not expected. The STIR input and output are presented in Appendix G. 

Based on the available toxicity data, sulfosulfuron appears to be very toxic to plants. When 

used in accordance with the label, sulfosulfuron may move off-site of application by spray drift 

and/or runoff. This may result in potential risk to the survival, growth, and reproduction of 

terrestrial non-target plants inhabiting adjacent or nearby acreage to the site of application. 

Sulfosulfuron is expected to move to surface waters adjacent to application sites by spray drift 

and/or runoff where it may affect both vascular and nonvascular aquatic plants. 

Since sulfosulfuron is very phytotoxic to plants and has the potential to leach into ground 

water, irrigation from shallow ground water aquifers may adversely impact non-target sensitive 

crops. In addition, surface waters contaminated with runoff or spray drift residues of 

sulfosulfuron when used to irrigate non-target crops may adversely impact non-target sensitive 

crops.

Because adverse effects to non-target terrestrial and aquatic plants can be expected, terrestrial 

and aquatic animals may be indirectly affected through the reductions in primary productivity 

and habitat.

Based on the above information, the following risk hypothesis is used for sulfosulfuron:

Based on the application methods, mode of action, persistence and mobility of 

sulfosulfuron, direct deleterious effects to non-target terrestrial and aquatic plant 

communities and indirect effects to both aquatic and terrestrial species through habitat 
43

modification are likely. Direct acute and chronic toxic effects to animals are expected to 

be limited, although without submission of additional avian information there is 

uncertainty in risk conclusions.

15.0 Analysis Plan 

In registration review, pesticide ecological risk assessments will follow the Agency’s 

Guidelines for Ecological Risk Assessment, will be in compliance with the paper titled 

“Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. 

Environmental Protection Agency” (“Overview Document”) (January 2004), and will be done in 

accordance with Section 7 of the Endangered Species Act (US EPA, 2004).

Previously completed screening level risk assessments and exceedances of Agency levels of 

concern indicate a need to further examine and refine phytotoxic risk to aquatic and terrestrial 

plant species. Analysis of potential indirect effects on listed species (both aquatic and terrestrial) 

is also required. This analysis plan will be revisited and may be revised depending upon the data 

available in the open literature and the information submitted by the public in response to the 

opening of the Registration Review docket.

15.1Ecological Measures of Exposure

In order to assess risk to terrestrial birds and mammals, the model used to predict terrestrial 

EECs on food items is Terrestrial Residue Exposure (T-REX) model. The model used to derive 

EECs relevant to terrestrial and wetland plants is TerrPlant. This model uses estimates of 

pesticides in runoff and in spray drift to calculate EECs. EECs are based upon solubility, 

application rate and minimum incorporation depth. The spray drift model, AgDRIFT is used to 

assess exposures of sulfosulfuron deposited on terrestrial habitats by spray drift. These models 

are parameterized using relevant reviewed registrant-submitted environmental fate data.

Use information will be retrieved from registration labels and used as inputs for estimating 

exposure concentrations from the various use scenarios. Sulfosulfuron’s use patterns (aerial 

application) suggest potential risk concerns to non-target aquatic and terrestrial plants. The 

range of potential exposure to sulfosulfuron to non-target plants can vary on application method 

(aerial or ground), application rate, and use pattern. 

Specific environmental fate related activities necessary to complete an aquatic ecological risk 

assessment of sulfosulfuron may include the following:

Environmental concentrations will be modeled using PRZM-EXAMS. When there 

are multiple crop use scenarios for sulfosulfuron modeling using PRZM-EXAMS, 

and EFED will choose conservative surrogate scenarios that are likely to generate 

high-end EECs. In addition, the potential for contaminated irrigation water to 

adversely affect sensitive agricultural crops will be assessed. 

As metabolites and a degradate were identified as residues of concern, aquatic EECs 

will be modeled using the total toxic residue approach. 
44

Exposure from drinking water pathway will be explored further with the development of SIP 

v.2.0 in the Ecological Risk Assessment for sulfosulfuron. 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.

Non-target crops may be exposed to contaminated irrigation waters from surface water or 

shallow ground water containing sulfosulfuron. The potential risks to plants when exposed to 

irrigation water contaminated with sulfosulfuron will be estimated for both ground water and 

surface water irrigation sources. The EEC for ground water will be calculated using the Tier 1 

SCIGROW model while that for surface water will be calculated using PRZM/EXAMS from the 

scenario yielding the highest EECs. Comparisons will be made to the most sensitive endpoint 

from vegetative vigor study assuming that runoff of irrigation water does not occur.

15.2Drinking Water Measures of Exposure

The Environmental Fate and Effects Division (EFED) was requested to prepare a human 

health drinking water risk assessments for the proposed new use of sulfosulfuron on grass forage, 

fodder, and hay (Crop Group 17) which includes Bermuda and Bahia grass pastures. Estimated 

drinking water concentrations (EDWCs) for surface and ground water were derived from the 

EFED Tier 1 screening models, FIRST and SCI-GROW, respectively. This document presented 

a Tier 1 drinking water assessment (DWA) which was prepared for the Health Effects Division 

(HED) as part of Human Risk Assessment and Tolerance Petition for the proposed new use of 

sulfosulfuron (DP Barcode: D327364, May 24, 2007). Previous drinking water assessments 

(D304290, D304476, D304659) have resulted in estimated drinking water concentrations 

(EDWCs) which were below the HED level of concern (LOC). A summary of the environmental 

fate data for sulfosulfuron which were used in the previous drinking water assessments are 

presented in Table 6. 

Both the parent and sulfonamide moiety degradation products are being considered for the 

Registration Review drinking water assessment as well as for ecological risk assessment. 

Calculated Residues of Concern (ROC) chemical properties for this assessment are also 

presented in Table 6.

15.3Measures of Effect

The acute measures of effect used for animals in this screening-level assessment are the 

LD50, LC50 and EC50. LD stands for "Lethal Dose", and LD50 is the amount of a material, given 

all at once, that is estimated to cause the death of 50% of the test organisms. LC stands for 

“Lethal Concentration” and LC50 is the concentration of a chemical that is estimated to kill 50% 

of the test organisms. EC stands for “Effective Concentration” and the EC50 is the concentration 

of a chemical that is estimated to produce a specific effect in 50% of the test organisms. 
45

Endpoints for chronic measures of exposure for listed and non-listed animals are the 

NOAEL/NOAEC and NOEC. NOAEL stands for “No Observed-Adverse-Effect-Level” and 

refers to the highest tested dose of a substance that has been reported to have no harmful 

(adverse) effects on test organisms. The NOAEC (i.e., “No-Observed-Adverse-EffectConcentration”) is the highest test concentration at which none of the observed effects were 

statistically different from the control. The NOEC is the No-Observed-Effects-Concentration. 

For non-listed plants, only acute exposures are assessed (i.e., EC25 for terrestrial plants and EC50

for aquatic plants); for listed plants, either the NOAEC or EC05 is used. 

15.4Uncertainties in the Analysis Plan

Due to fate characteristics, use patterns, and the lack of data there are uncertainties with risk 

potential to; 1) passerine birds, 2) growth, survival and reproductive effects to terrestrial plants, 

3) vascular and non-vascular aquatic plants. Available toxicity data indicate that sulfosulfuron is 

practically non-toxic to avian species on an acute oral basis, and passerine species may be more 

or less sensitive to sulfosulfuron than waterfowl or upland game birds. In the absence of data on 

passerine species, risk will be presumed to exceed concern levels. Given the uncertainties in the 

terrestrial and aquatic plant toxicity data, the current toxicity values may be underestimating 

toxicity to these taxa; therefore, direct risk to plants and potential indirect effects as well as the 

overall effect area may be underestimated. 

15.5 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 (listed) species from 

registered uses of sulfosulfuron. 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 action area is used to identify all listed (threatened and endangered) species and 

designated critical habitat that could be affected by the Federal action. The Federal action is the 

authorization or registration of pesticide use or uses as described on the label(s) of pesticide 

products containing a particular active ingredient. The action area is defined by the Endangered 

Species Act as, “all areas to be affected directly or indirectly by the Federal action and not 

merely the immediate are involved in the action” (50 CFR §402.2). Based on an analysis of the 

Federal action, the action area is defined by the actual and potential use of the pesticide.

In the case of nationwide ecological risk assessment conducted for sulfosulfuron under 

Registration Review, the action area will encompass the entire United States and its territories. 

The purpose of defining the action area as the entire United States and its territories is to ensure 

that the initial area of consideration encompasses all areas where sulfosulfuron may be used now 

and in the future, including the potential for off-site transport via spray drift and downstream 

dilution. Additionally, the concept of a nationwide action area takes into account the potential 

for direct and indirect effects and any potential modification to critical habitat based on 
46

ecological effect measures associated with reduction in survival, growth, and reproduction, as 

well as the full suite of sublethal effects available in the effects literature. It is important to note 

that the nationwide action area does not imply that direct and/or indirect effects and critical 

habitat modification are expected to or are likely to occur over the full extent of the action area, 

but rather to identify all listed species and critical habitat that may potentially be affected by the 

action. The Agency will use more rigorous analysis including consideration of available land 

cover data, toxicity data, and exposure information to determine areas where individual listed 

species and designated critical habitat may be affected or modified via endpoints associated with 

reduced survival, growth, or reproduction.

 

16.0 Anticipated Data Needs

The Agency does foresee requiring additional fate and ecological effects studies prior to 

conducting the planned assessments. Table 11 to Table 13 presents the ecological effects studies 

currently available as well as any potential data gaps. Data gaps, uncertainties and potential 

paths forward for the assessment of sulfosulfuron are described below.

Table 11. Available Ecological Effects Data for Terrestrial Animals Exposed to 

Sulfosulfuron and Remaining Data Gaps.

Guideline Description MRID Classification Data Gap? Comments

850.2100 Avian oral toxicity 44295768 Acceptable

Partial*

* There is no passerine 

species data available, 

passerine species may be 

more sensitive to 

sulfosulfuron than either 

waterfowl or upland game 

species.

44295769 Acceptable

850.2200 Avian dietary 

toxicity 

44295770 Acceptable

No

44295771 Acceptable

850.2300 Avian reproduction 44295772 Acceptable

No

44295773 Acceptable

850.3020 Honeybee acute

contact toxicity 44295788 Acceptable No

Table 12. Available Ecological Effects Data for Aquatic Animals Exposed to Sulfosulfuron 

and Remaining Data Gaps.

Guideline Description MRID Classification Data Gap? Comments

850.1075 Freshwater fish – acute 

toxicity

44295774

44295775

Acceptable

Acceptable No *Although data is 

not currently 

available, based on a 

screening level 

analysis, this data is 

not being requested 

at this time.

850.1400 Freshwater fish –

early life stage test 44295779 Acceptable No

850.1010 Freshwater invertebrates –

Acute toxicity 44295776 Acceptable No
47

Guideline Description MRID Classification Data Gap? Comments

850.1300 Freshwater invertebrate –

life cycle test 44295780 Acceptable No

850.1075 Saltwater fish –

Acute toxicity 44309304 Acceptable No

850.1025

850.1035

850.1045

850.1055

Saltwater invertebrates –

Acute toxicity 

44295777 Supplemental

No

44295778 Acceptable

850.1400 Saltwater fish –

early life stage test

No Data 

Submitted -- No*

850.1350 Saltwater invertebrates – 

life cycle test

No Data 

Submitted -- No*

Table 13. Available Ecological Effects Data for Plants Exposed to Sulfosulfuron and 

Remaining Data Gaps.

Guideline Description MRID Classification Data 

Gap? Comments

850.4225

Terrestrial Plant toxicity: 

seedling emergence 

(Tier 2)

44295783 Supplemental Yes*

* Seedling emergence and 

vegetative vigor study was 

conducted using TGAI, 

therefore, Tier II tests are 

requested using a TEP. 

**For the green algae 

study, the EC50 and 

NOAEC values fall within 

concentrations not analyzed 

due because they were 

<LOQ. For cyanobacteria, 

precipitate was observed 

without removal prior to 

analysis and the EC50 and 

EC05 values fall within 

concentrations not analyzed 

due to <LOD.

***All concentrations were 

based on nominal because 

they were below the LOQ.

- Data is also needed to 

evaluate risk from exposure 

to the major degradates to 

aquatic non-target vascular 

plant species.

850.4250

Terrestrial Plant toxicity: 

vegetative vigor 

(Tier 2)

44295784 Supplemental Yes*

850.5400 Aquatic Plant Growth: 

algae 

(Tiers 1 and 2)

44295781

44295782

44295785

44295786

Supplemental

Supplemental

Supplemental

Supplemental

Partial**

850.4400 Aquatic Plant Growth: 

vascular plants 

(Tier 2)

44295782 Supplemental Yes***
48

Table 14. Degradates and Requested Studies

Degradate 

Common 

Name

(CAS #, if 

available)

Study 

requested

Comment

Sulfamic acid 850.4400

Aquatic plant 

(duckweed, 

Lemna)

These degradates form 

via photolysis in 

aquatic environments 

(parent degradation 

half-life of approx 2.5 

days) or via aerobic 

aquatic metabolism. 

An aquatic vascular 

plant study is needed to 

determine whether 

these degradates present 

a risk. 

Sulfone

Oxamic acid

Aminopyrimidine

Desmethyl 

sulfosulfuron

16.1Environmental Fate

835.6100 (Environmental Chemistry Method and Independent Laboratory Validation 

Only) for soil methods

835.6200 (Environmental Chemistry Method and Independent Laboratory Validation 

Only) for water methods

16.2Ecological Effects

Several toxicity studies are needed to better assess the potential risk of sulfosulfuron

exposure to non-target organisms. The studies listed below should be submitted to increase 

certainty in the risk estimation.

850.2100, Acute Avian Oral Toxicity Test (with a Passerine species). A protocol for 

Agency review is requested prior to conducting study;

850.4225, Nontarget Area Phytotoxicity Tier II, Seedling Emergence (tested using a 

Typical End-use Product);

850.4250, Nontarget Area Phytotoxicity Tier II, Vegetative Vigor (tested using a Typical 

End-use Product);

850.4400, Nontarget Area Phytotoxicity Tier II, Aquatic Plant Growth (Vascular Plants), 

using Lemna spp., (using TGAI);

850.5400, Nontarget Area Phytotoxicity Tier II, Aquatic plant Growth (Algal Plants) 

(with a green algal, Pseudokirchneriella subcapitata (formerly known as Selenastrum 

capricornutum) and a cyanobacteria, Ananabaena flos-aquae); 
49

Guideline Number: none, Special Non-Target Plant Reproductive Toxicity Study to 

determine the EC25 and NOAEC. A protocol for Agency review is requested prior to 

conducting study. 

850.4400, Nontarget Area Phytotoxicity Tier I/II, Aquatic Plant Growth (Vascular 

Plants), using Lemna spp., (using degradates listed in Table 14);

If the registration review risk assessment, including listed species assessments, is performed 

without these data, the Agency would have to assume that sulfosulfuron “may affect” these taxa 

directly (and listed species from other taxa indirectly), and use of sulfosulfuron and its 

formulated products may need to be restricted in areas where listed species could be exposed. 

The lack of these data will limit the flexibility the Agency and registrants have in complying 

with the Endangered Species Act and could result in restrictions for sulfosulfuron use that might 

prove to be unnecessary given data to address this area of uncertainty.

The Agency will conduct a search of the open literature to ensure that all best available science 

is utilized. The Agency uses the ECOTOX database as its mechanism for searching the open 

literature for ecological effects information. ECOTOX integrates three previously independent 

databases - AQUIRE, PHYTOTOX, and TERRETOX - into a system which includes toxicity 

data derived predominately from the peer-reviewed literature, for aquatic life, terrestrial plants, 

and terrestrial wildlife, respectively.

17.0 Other Information Needs

There is specific information that will assist the Agency in refining the ecological risk 

assessment, including any species-specific effects determinations. The Agency is very much 

interested in obtaining the following information:

1. confirmation on the following label information

a. frequency of application, application intervals, and maximum number of 

applications per season

b. geographic limitations on use

2. use or potential use distribution (e.g., acreage and geographical distribution of relevant 

crops)

3. use history

4. median and 90th percentile reported use rates (lbs. a.i./acre) from usage data – national, 

state, and county

5. application timing (date of first application and application intervals) by crop – national, 

state, and county

6. sub-county crop location data

7. usage/use information for non-agricultural uses (e.g., forestry, residential, rights-of-way)

8. directly acquired county-level usage data (not derived from state level data)

a. maximum reported use rate (lbs. a.i./acre) from usage data – county

b. percent crop treated – county

c. median and 90th percentile number of applications – county

d. total pounds per year – county

e. the year the pesticide was last used in the county/sub-county area
50

f. the years in which the pesticide was applied in the county/sub-county area

9. typical interval (days)

10. state or local use restrictions

11. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency

12. monitoring data 

The analysis plan will be revisited and may be revised depending upon the data available in 

the open literature and the information submitted by the public in response to the opening of the 

Registration review docket.

18.0 Data Call-In Tables For Fate and Ecological Effect Studies

18.1Environmental Fate Studies

Guideline Number: 835.6100 (Environmental Chemistry Method and Independent 

Laboratory Validation Only)

Study Title: Environmental Chemistry Method for Residues in Soil (and associated 

Independent Laboratory Validation)

Rationale for Requiring the Data

Independently validated analytical methods for residues in soil, water, sediment, and plant 

material (environmental chemistry methods) submitted by the registrant are used to evaluate 

analyses described in submitted environmental fate and ecological effects studies. Submitted 

analytical methods are also used by various federal, state, tribal, and local agencies to detect and 

monitor residues that are or are suspected to be in environmental compartments due to outdoor 

uses and accidental releases. Independent laboratory validations for submitted analytical 

methods are necessary to confirm that the methods are functional and to confirm the levels of 

detection and quantitation reported in registrant-prepared validations.

Use of sulfosulfuron may impact terrestrial environments due to residues of concern during the 

application process. This is especially true for poorly draining soils, erodible soils, and soils 

with shallow ground water. Therefore, outside agencies may request analytical methods with 

which to monitor for sulfosulfuron residues of concern in soils.

An independently validated environmental chemistry method for sulfosulfuron residues in soils 

has not been submitted by the registrant. If aerobic soil metabolism data indicate that 

sulfosulfuron is not transient in soils, a validated analytic method for residues in soil should be 

available. Therefore, a validated environmental chemistry method for sulfosulfuron in soil and 

an independent laboratory validation of the method are required to support monitoring for 

sulfosulfuron residues and to evaluate newly submitted environmental fate and ecological 

effects data.

Practical Utility of the Data
51

How will the data be used?

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside the 

Agency may lack chemical-specific methods for analyses in environmental compartments. 

Independently validated environmental chemistry methods will be used to evaluate newly 

submitted environmental fate and ecological effects data and will be made available for 

enforcement and monitoring purposes at the federal, state, and local levels.

How could the data change the Agency’s decision, or impact the Agency’s future decisionmaking? 

Risk assessment conclusions could be altered if they are not supported by either study data or 

environmental monitoring detections that are based on independently validated environmental 

chemistry methods. Furthermore, while not directly related to Agency decision-making, 

independently validated environmental chemistry methods are necessary to ensure the safety of 

those in proximity to releases of sulfosulfuron residues in the environment.

Guideline Number: 835.6200 (Environmental Chemistry Method and Independent 

Laboratory Validation Only)

Study Title: Environmental Chemistry Method for Residues in Water (and associated 

Independent Laboratory Validation)

Rationale for Requiring the Data

Independently validated analytical methods for residues in soil, water, sediment, and plant 

material (environmental chemistry methods) submitted by the registrant are used to evaluate 

analyses described in submitted environmental fate and ecological effects studies. A report 

containing this data has been submitted by the registrant; however, it has not been formally 

reviewed. In the interim the data has been accepted on a provisional basis but will still be 

identified as a data gap until the review is completed. Submitted analytical methods are also 

used by various federal, state, tribal, and local agencies to detect and monitor residues that are or 

are suspected to be in environmental compartments due to outdoor uses and accidental releases. 

Independent laboratory validations for submitted analytical methods are necessary to confirm 

that the methods are functional and to confirm the levels of detection and quantitation reported 

in registrant-prepared validations.

Use of sulfosulfuron may impact surface water quality due to residues of concern in runoff of 

rain water and drift of residues. This is especially true for poorly draining soils, erodible soils, 

and soils with shallow ground water. Therefore, outside agencies may request analytical 

methods with which to monitor for sulfosulfuron residues of concern in water.

An independently validated environmental chemistry method for sulfosulfuron residues in water 

has not been submitted by the registrant. If aerobic aquatic metabolism data indicate that 

sulfosulfuron is not transient in acidic, aerobic water bodies, a validated analytic method for 

residues in water should be available. Therefore, a validated environmental chemistry method 

for sulfosulfuron in water and an independent laboratory validation of the method are required 
52

to support monitoring for sulfosulfuron residues and to evaluate newly submitted environmental 

fate and ecological effects data.

Practical Utility of the Data

How will the data be used?

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside the 

Agency may lack chemical-specific methods for analyses in environmental compartments. 

Independently validated environmental chemistry methods will be used to evaluate newly 

submitted environmental fate and ecological effects data and will be made available for 

enforcement and monitoring purposes at the federal, state, and local levels.

How could the data change the Agency’s decision, or impact the Agency’s future decisionmaking? 

Risk assessment conclusions could be altered if they are not supported by either study data or 

environmental monitoring detections that are based on independently validated environmental 

chemistry methods. Furthermore, while not directly related to Agency decision-making, 

independently validated environmental chemistry methods are necessary to ensure the safety of 

those in proximity to releases of sulfosulfuron residues in the environment.

18.2Ecological Effects Studies

Guideline Number: 850.2100 

Study Title: Avian Acute Oral Toxicity Test

Test Substance: TGAI

Rationale for Requiring the Data

Acceptable acute avian oral toxicity data were not submitted for a passerine species exposed to 

sulfosulfuron, which is now required under the 40 CFR Part 158 (CFR 40 2008) data requirements for 

conventional pesticides. The revised Part 158 data requirements specify that acute avian oral toxicity 

data be submitted for either one waterfowl or one upland game species and one passerine species. 

Although available acute oral toxicity data for mallard ducks and bobwhite quails, when compared to 

estimated environmental concentrations, indicate that levels of concern are not exceeded for birds on an 

acute basis, however, in the acute oral study with bobwhite quail signs of toxicity were observed at the 

two highest test doses and an effect on body weight gain at the highest dose. Because passerine species 

have higher metabolic rates due to their smaller sizes than either waterfowl or upland game bird species 
53

and because they may utilize different metabolic pathways, they may be more sensitive to 

sulfosulfuron. In order to properly characterize risk to passerines, an avian oral toxicity test is required 

for passerine birds. A passerine study protocol must be submitted for review by the Agency prior to 

initiation of the study.

Practical Utility of the Data

How will the data be used?

Acute avian oral toxicity data for passerine species will be used to refine the screening-level risk 

assessment by determining whether there are differences in avian species sensitivity to sulfosulfuron

between currently tested passerine and upland game and/or waterfowl species that are beyond the 

simple allometric predictions currently employed in the absence of such passerine data. The current 

extrapolation method may be under- or over-estimating risks to passerines.

How could the data impact the Agency’s future decision-making?

If future risk assessments, including listed species assessments, are performed without these data, the 

Agency would have to assume that sulfosulfuron “may affect” listed birds directly (and listed species 

from other taxa indirectly), and use of sulfosulfuron and its formulated products may need to be 

restricted in areas where listed species could be exposed. The lack of these data will limit the flexibility 

the Agency and registrants have in complying with the Endangered Species Act and could result in 

restrictions for sulfosulfuron use that might prove to be unnecessary given data to address this area of 

uncertainty.
54

Guideline Number: 850.4225 and 850.4250

Test Substance: Sulfosulfuron Typical End-use Product (TEP)

Study Title: Non-target Area Phytotoxicity (Tier II) Seedling Emergence and Vegetative Vigor

Test Species: Corn, soybeans, and a root crop, plus seven other species (six species of at least 

four families of dicots and four species of at least two families of monocots)

Rationale for Requiring the Data

Seedling emergence and vegetative vigor toxicity test with technical grade sulfosulfuron were 

submitted. Current guidance (40CFR Part 158) requires a Tier II terrestrial plant toxicity testing 

to be conducted using a TEP as plants are likely to be exposed to other components in a TEP as 

well as the active ingredient. Furthermore, as sulfosulfuron is a herbicide, there is concern and 

uncertainty in how the other ingredients in the TEP may influence or affect the toxicity to 

terrestrial plants. The current toxicity values for seedling emergence and vegetative vigor, when 

compared to the estimated environmental concentrations, indicate that the level of concern for 

terrestrial plants is exceeded.

Practical Utility of the Data

How will the data be used?

Data from Tier II seedling emergence and vegetative vigor toxicity studies using a TEP will be 

used to quantitatively estimate potential risks to terrestrial plants associated with the use of 

sulfosulfuron. These data will be used to define an action area for endangered species and 

explore risk mitigation strategies. The data will reduce uncertainties associated with the risk 

assessment for terrestrial plants and will improve the Agency’s understanding of the potential 

effects of sulfosulfuron on terrestrial plants. 

How could the data impact the Agency’s future decision-making?

The value of these seedling emergence and vegetative vigor studies would be in quantifying and 

potentially refining risks to non-target terrestrial plants. Primary producers (i.e. plants) provide 

oxygen, food and habitat vital to ecological processes. Therefore, a solid understanding of the 

potential risks to plants is essential in order to assess the environmental risks the use of 

sulfosulfuron may pose. Defining an action area for endangered species and exploring risk 

mitigation strategies may be underestimated without these data. Without TEP terrestrial plant 

toxicity data for sulfosulfuron, the Agency may underestimate the direct adverse effects to 

terrestrial plants and indirect effects (e.g., via loss of habitat/cover, riparian vegetation effects, 

etc.). The lack of these data could limit the knowledge and flexibility the Agency and registrants 

have in coming into compliance with the Endangered Species Act and could result in 

underestimating mitigation for sulfosulfuron. 
55

Guideline Number: 850.4400

Test Substance: TGAI

Study Title: Aquatic Plant Growth Toxicity Study using Lemna spp.

Rationale for Requiring the Data

A study using Lemna sp., was submitted by the registrant. However, none of the concentrations were 

analyzed during the study due to the concentration being lower than the reported limit of detection; 

therefore, there is uncertainty in the actual exposure concentrations. In addition, at the highest 

concentration tested, only 50% inhibition was observed, therefore, the EC50 value is an approximate 

value. Based on this approximate EC50 value when compared to estimated environmental concentrations 

the level of concern is exceeded for aquatic vascular plants. 

Practical Utility of the Data

How will the data be used? 

The data will be used to estimate potential risks to non-target aquatic plants, including the likelihood of 

potential risks to endangered species, either by direct effects or by indirect effects, and to reduce 

uncertainties associated with the current ecological risk assessment. By refining the assessment, the 

Agency will be able to determine whether current labeling is appropriate and whether further mitigation 

is necessary.

How could the data impact the Agency’s future decision-making?

The value of these data would be in quantifying and potentially refining risks to non-target aquatic plants. 

These data, once submitted, will allow the Agency to further characterize the risk of sulfosulfuron to 

aquatic ecosystems. Primary producers (i.e. plants) provide oxygen, food and habitat vital to ecological 

processes. Therefore, a solid understanding of the potential risks to plants is essential in order to assess 

the environmental risks the use of sulfosulfuron may pose. Defining an action area for endangered 

species and exploring risk mitigation strategies may be underestimated without these data. The lack of 

these data could limit the knowledge and flexibility the Agency and registrants have in coming into 

compliance with the Endangered Species Act and could result in underestimating mitigation for 

sulfosulfuron.

Guideline Number: 850.5400, 122-2

Study Title: Aquatic Plant-Marine Green Algae Pseudokirchneriella subcapitata (formerly known as 

Selenastrum capricornutum)

Guideline Number 850.5400, 122-2

Study Title: Aquatic Plant-Cyanobacteria Anabaena flos-aquae

Test Substance: TGAI (both studies)

Rationale for Requiring the Data

 

For the reported most sensitive non-vascular aquatic species, the green algae, the EC50 and the NOAEC 

values fall within the range of test concentrations that were not analyzed. In addition, for the 

cyanobacteria species, Anabaena flos-aquae, particulate matter was observed, the EC50 and EC05 values 

fall within range of test concentrations that were not measured. Therefore, there is uncertainty in the 

actual exposure concentrations for these two non-vascular aquatic studies. As the EC50 value for 

cyanobacteria is close to the EC50 value for green algae, there is uncertainty in which species may be 

more sensitive to sulfosulfuron exposure. Due to the fact that aquatic vascular and non-vascular plant 

species are sensitive to sulfosulfuron exposure, and sulfosulfuron is applied in many different scenarios 

where drift or runoff is expected to enter aquatic ecosystem, there is uncertainty in whether the reported 
56

toxicity data are appropriate for evaluating risk.

Practical Utility of the Data

How will the data be used? 

The data will be used to estimate potential risks to non-target aquatic plants, including the likelihood of 

potential risks to endangered species, either by direct effects or by indirect effects, and to reduce 

uncertainties associated with the current ecological risk assessment. By refining the assessment, the 

Agency will be able to determine whether current labeling is appropriate and whether further mitigation is 

necessary.

How could the data impact the Agency’s future decision-making?

If future risk assessments, including listed species assessments, are performed without these data, the 

Agency would have to assume that sulfosulfuron “may affect” listed aquatic non-target plants directly 

(and listed species from other taxa indirectly), and use of sulfosulfuron and its formulated products may 

need to be restricted in areas where listed species could be exposed. These data, once submitted, will 

allow the Agency to further characterize the risk of sulfosulfuron to aquatic ecosystems. Primary 

producers (i.e. plants) provide oxygen, food and habitat vital to ecological processes. Therefore, a solid 

understanding of the potential risks to plants is essential in order to assess the environmental risks the use 

of sulfosulfuron may pose. Defining an action area for endangered species and exploring risk mitigation 

strategies may be underestimated without these data. The lack of these data could limit the knowledge 

and flexibility the Agency and registrants have in coming into compliance with the Endangered Species 

Act and could result in underestimating mitigation for sulfosulfuron.
57

Guideline Number: none

Study Titles: Special Study for Non-Target Plant Reproductive Toxicity

Rationale for Requiring the Data

As stated in the Problem Formulation, investigations/studies have indicated a small percentage of the label 

application rate of low dose high potency herbicides such as sulfonylureas (e.g. sulfosulfuron) may impact 

the reproduction of non-target terrestrial plants. However, there are no available data on adverse 

reproductive impacts to terrestrial plants from sulfosulfuron residues due to spray drift. Terrestrial plant 

reproductive toxicity data would help to screen for potential plant risks associated with sulfosulfuron use. 

Plants form the basis of most habitats and contribute significantly to overall environmental quality. The 

loss of plant reproductive output could potentially have an adverse effect on animals, both invertebrates 

and vertebrates, as many are dependent on plant reproduction for a food source and for habitat quality and 

structure. A solid understanding of the potential risks to plants is therefore essential for sound 

environmental management. A study protocol must be submitted for review and approved by the Agency 

prior to initiation of the study.

Practical Utility of the Data

How will the data be used? 

Guideline Number: 850.4400 

Study Titles: Aquatic Vascular Plant Growth (Lemna gibba) – Tiers I/II

Test Substance: Major degradates –, sulfamic acid, sulfone, oxamic acid, aminopyrimidine and 

desmethyl sulfosulfuron 

Rationale for Requiring the Data

No toxicity data are currently available to assess the risk of the sulfosulfuron major degradates sulfamic 

acid, sulfone, oxamic acid, aminopyrimidine and desmethyl sulfosulfuron to aquatic vascular plants.

Sulfosulfuron is applied in many different scenarios where drift is expected to enter aquatic ecosystems. 

Sulfamic acid, sulfone, oxamic acid and aminopyrimidine form via aqueous photolysis (21, 28, 15.6 and 

28%, respectively) and there is a likelihood of movement of the parent to the aquatic environment via 

spray drift and subsequent formation of these degradates. Desmethyl sulfosulfuron formed in the aerobic 

aquatic metabolism study (14%) and may form after spray drift exposure of parent to aquatic systems. 

Given the high likelihood of exposure to the degradates and the lack of any data evaluating the toxicity of 

these degradates, there is a likelihood that degradates may retain the phytotoxic properties of the parent. 

Tier I testing is required, followed by Tier II if required by Tier I results as specified in Tier I guidelines, 

to allow for a determination of whether or not the major degradates sulfamic acid, sulfone, oxamic acid, 

aminopyrimidine and desmethyl sulfosulfuron are toxic to aquatic vascular plants. 

Practical Utility of the Data

How will the data be used? 

The data will be used to estimate potential risks to aquatic vascular plants, including the likelihood of 

potential risks to endangered species, either by direct effects or by indirect effects, and to reduce 

uncertainties associated with the current ecological risk assessment. By refining the assessment, the 

Agency will be able to determine whether current labeling is appropriate and whether further mitigation 

is necessary. 

How could the data impact the Agency’s future decision-making?

Because aquatic vascular plants form the basis of the food chain for aquatic habitats and significantly 

contribute to overall water quality, a solid understanding of the potential risks to aquatic plants is 

essential for sound environmental risk management decision-making. These data, once submitted, will 
58

The data will be used to estimate potential reproductive risks to non-target terrestrial plants, including the 

likelihood of potential risks to endangered species, either by direct effects or by indirect effects, and to 

reduce uncertainties associated with the current ecological risk assessment. By refining the assessment, 

the Agency will be able to determine whether current labeling is appropriate and whether further 

mitigation is necessary. In the absence of this data, risks to terrestrial plants will be presumed.

How could the data impact the Agency’s future decision-making?

These data, once submitted, should allow the Agency to characterize the risk posed to plant reproductive 

processes from sulfosulfuron in terrestrial ecosystems. Primary producers (i.e. plants) provide food and 

habitat vital to ecological processes. Therefore, a solid understanding of the potential risks to non-target 

plants is essential in order to assess the environmental risks the use of sulfosulfuron may pose. If the data 

indicate that sulfosulfuron poses significant risks to these non-target plant species, the Agency may 

explore additional decision options to minimize the risks to these species. The lack of these data will limit 

the flexibility the Agency and registrants have in complying with the Endangered Species Act and could 

result in use restrictions for sulfosulfuron which may otherwise be avoided, or which are unnecessarily 

severe.

allow the Agency to better characterize the risk of sulfosulfuron’s metabolites to aquatic ecosystems. 

Primary producers (i.e. plants) provide oxygen, food and habitat vital to ecological processes. Therefore, 

a solid understanding of the potential risks to aquatic plants is essential in order to assess the 

environmental risks the use of the sulfosulfuron, as a sulfonylurea herbicide, and its resulting metabolites,

may pose. If the data indicates that sulfosulfuron’s degradates poses a significant risk to aquatic vascular 

plants inhabiting water bodies, the Agency may explore additional decision options to minimize the risk 

of sulfosulfuron to aquatic vascular plants. The lack of these data will limit the flexibility the Agency 

and registrants have in complying with the Endangered Species Act and could result in use restrictions for 

sulfosulfuron which may otherwise be avoided, or which are unnecessarily severe. 

19.0 References

Asghari, J.B. and J.O. Evans. 1992a. Dyer’s woad (Isatis tinctoris L.) pollen viability is reduced 

by metsulfuron methyl application. Research Progress Report of the Western Society of 

Weed Science. Meeting March 9-12, 1992. Salt Lake City, UT. pp. VI-4-VI-5.

Asghari, J.B. and J.O. Evans. 1992b. Effect of metsulfuron methyl on seed formation and 

viability of Dyer’s woad (Isatis tinctoria L.) in the field.. Research Progress Report of the 

Western Society of Weed Science. Meeting March 9-12, 1992. Salt Lake City, UT. Pp. III178-II-179.

Asghari, J.B., J.O. Evans, and S.A. Dewey. 1993. Dyer’s woad seed production and 

germinability reduced by sulfonylurea herbicides.

Bhatti, M.A., K. Al-Khatib, A.S. Felsot, R. Parker, S. Kadir. 1995. Effects of simulated 

chlorsulfuron drift on fruit yield and quality of sweet cherries (Prunus avium L.). 

Environmental Toxicology and Chemistry 14(3): 537-544.
59

Boutin, C., H.B. Lee, E.T. Peart, P.P. Batchelor, and R.J. Maguire. 2000. Effects of the 

sulfonylurea herbicide metsulfuron methyl on growth and reproduction of five wetland and 

terrestrial plant species. Environmental Toxicology and Chemistry 19(10): 2532-2541.

Fletcher J.S., T. G. Pfleeger and H.C. Ratsch 1993. Potential Environmental Risks Associated with 

the New Sulfonylurea Herbicides. Environ. Sci. Technol. 27(10): 2250-2252.

Fletcher, J.S., T.G. Pfleeger, and H.C. Ratsch. 1995. Chlorsulfuron influence on garden pea 

reproduction. Physiologia Plantarum 94: 261-267.

Fletcher, J.S., T.G. Pfleeger, H.C. Ratsch, and R.Hayes. 1996. Potential impact of low levels of 

chlorsulfuron and other herbicides on growth and yield of nontarget plants. Environmental 

Toxicology and Chemistry 7: 1189-1196.

Liping Wei,Hongxia Yu, Yue Sun, Jianfang Fen, and Liansheng Wang. 1998. The Effects of 

Three Sulfonylurea Herbicides and Their Degradation Products on the Green Algae Chlorella 

pyrenoidosa. Chemosphere 37 (4): 747-751.

Mayer, D. and C. Johansen. 1990. Pollinator Protection: A Bee & Pesticide Handbook.Wicwas 

Press. Cheshire, Conn. p. 161.

U.S. Environmental Protection Agency. 1998. Guidelines for Ecological Risk Assessment. 

Risk Assessment Forum, Office of Research and Development, Washington, D.C. 

EPA/630/R-95/002F. April 1998.

United States Environmental Protection Agency (EPA). 2004. Overview of the Ecological Risk 

Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection 

Agency, Endangered and Threatened Species Effects Determination. Office of Prevention, 

Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C., January 

23, 2004.

United States Environmental Protection Agency (EPA). 2005. Environmental Fate and Effects 

Division, May 10, 2005. Revised Environmental Fate and Ecological Risk Assessment of 

Chlorsulfuron. DP Barcode. D330621.
60

Appendix A. MRID Bibliography

Guideline: 61-1 Chemical Identity

MRID: 44295702 Itoh, S.; Tabuchi, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 1 of 3: 

Product Identity and Composition: Final Report: Lab Project Number: TKM-19-PC: RD 1353. Unpublished study 

prepared by Takeda Chemical Industries, Ltd. 155 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 61-2 Description of Beginning Materials and Manufacturing Proces

MRID: 44295702 Itoh, S.; Tabuchi, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 1 of 3: 

Product Identity and Composition: Final Report: Lab Project Number: TKM-19-PC: RD 1353. Unpublished study 

prepared by Takeda Chemical Industries, Ltd. 155 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 61-3 Discussion of Formation of Impurities

MRID: 44295702 Itoh, S.; Tabuchi, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 1 of 3: 

Product Identity and Composition: Final Report: Lab Project Number: TKM-19-PC: RD 1353. Unpublished study 

prepared by Takeda Chemical Industries, Ltd. 155 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 62-1 Preliminary Analysis

MRID: 44295703 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 2 of 3: Analysis and 

Certification of Product Ingredients: Lab Project Number: TKM-19-PC: MSL 14299: 6155-104. Unpublished study 

prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 390 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 62-2 Certification of limits
61

MRID: 44295703 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 2 of 3: Analysis and 

Certification of Product Ingredients: Lab Project Number: TKM-19-PC: MSL 14299: 6155-104. Unpublished study 

prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 390 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 62-3 Analytical Method

MRID: 44295703 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 2 of 3: Analysis and 

Certification of Product Ingredients: Lab Project Number: TKM-19-PC: MSL 14299: 6155-104. Unpublished study 

prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 390 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

Guideline: 63-0 Reports of Multiple phys/chem Characteristics

MRID: 44295702 Itoh, S.; Tabuchi, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 1 of 3: 

Product Identity and Composition: Final Report: Lab Project Number: TKM-19-PC: RD 1353. Unpublished study 

prepared by Takeda Chemical Industries, Ltd. 155 p. 

MRID: 44295703 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 2 of 3: Analysis and 

Certification of Product Ingredients: Lab Project Number: TKM-19-PC: MSL 14299: 6155-104. Unpublished study 

prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 390 p. 

MRID: 44295704 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 3 of 3: Physical and 

Chemical Characteristics: (Final Report): Lab Project Number: TKM-19-PC: MSL 14299: 6155-102. Unpublished 

study prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 354 p. 

MRID: 44295705 Triebe, F. (1996) Product Chemistry Study for MON 37532 Herbicide Formulation: Lab Project 

Number: RD 1353: MSL 14563: PC13-96-1. Unpublished study prepared by Monsanto Co. and Notox B. V. 114 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

Guideline: 63-17 Storage stability

MRID: 44295704 Yanai, T. (1996) Product Chemistry Data for TKM-19 (MON37500): Part 3 of 3: Physical and 

Chemical Characteristics: (Final Report): Lab Project Number: TKM-19-PC: MSL 14299: 6155-102. Unpublished 

study prepared by Takeda Chemical Industries, Ltd.; Monsanto Co.; and Hazleton Wisconsin, Inc. 354 p. 

MRID: 45116101 Triebe, F. (2000) Product Chemistry Data to Support the Registration of MON 37525 Herbicide: 

Lab Project Number: PC13-99-06-0: MSL-16481: 1500. Unpublished study prepared by Monsanto Company. 50 p. 

MRID: 45411301 Triebe, F. (2001) Product Chemistry Data for MON 37525 Herbicide: Storage Stability and 

Corrosion Characteristics: Lab Project Number: PC13-99-06-D: MSL-16974. Unpublished study prepared by 

Monsanto Company. 25 p. {OPPTS 830.6317 and 830.6320} 

MRID: 45643401 Van Rijsbergen, L. (1998) Determination of the Stability of MON 37532 Over 2 Years Under 

Ambient Conditions: Lab Project Number: 161854: 55512: 1542. Unpublished study prepared by Notox B.V. 54 p. 

Guideline: 63-20 Corrosion characteristics
62

MRID: 45411301 Triebe, F. (2001) Product Chemistry Data for MON 37525 Herbicide: Storage Stability and 

Corrosion Characteristics: Lab Project Number: PC13-99-06-D: MSL-16974. Unpublished study prepared by 

Monsanto Company. 25 p. {OPPTS 830.6317 and 830.6320} 

Guideline: 71-1 Avian Single Dose Oral Toxicity

MRID: 44295768 Campbell, S.; Beavers, J. (1994) MON 37500: An Acute Oral Toxicity Study with the Northern 

Bobwhite: Final Report: Lab Project Number: WL-94-070: 139-386: RD 1353. Unpublished study prepared by 

Wildlife International Ltd. 28 p. 

MRID: 44295769 Campbell, S.; Beavers, J. (1995) MON 37500: An Acute Oral Toxicity Study with the Mallard: 

(Final Report): Lab Project Number: WL-94-217: 139-389: RD 1353. Unpublished study prepared by Wildlife 

International Ltd. 27 p. 

Guideline: 71-2 Avian Dietary Toxicity

MRID: 44295770 Campbell, S.; Beavers, J. (1994) MON 37500: A Dietary LC50 Study with the Northern 

Bobwhite: (Final Report): Lab Project Number: WL-94-068: 139-384: RD 1353. Unpublished study prepared by 

Wildlife International Ltd. 36 p. 

MRID: 44295771 Campbell, S.; Beavers, J. (1994) MON 37500: A Dietary LC50 Study with the Mallard: (Final 

Report): Lab Project Number: WL-94-069: 139-385: RD 1353. Unpublished study prepared by Wildlife 

International Ltd. 37 p. 

Guideline: 71-4 Avian Reproduction

MRID: 44295772 Frey, L.; Chafey, K.; Jacobs, R.; et al. (1996) MON 37500: A Reproduction Study with the 

Northern Bobwhite (Colinus virginianus): (Final Report): Lab Project Number: WL-95-117: 139-410: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 159 p. 

MRID: 44295773 Frey, L.; Chafey, K.; Jacobs, R.; et al. (1996) MON 37500: A Reproduction Study with the 

Mallard (Anas platyrhynchos): (Final Report): Lab Project Number: WL-95-232: 139-411: RD 1353. Unpublished 

study prepared by Wildlife International Ltd. 157 p. 

Guideline: 72-1 Acute Toxicity to Freshwater Fish

MRID: 44295774 Graves, W.; Swigert, J. (1994) MON 37500: A 96-Hour Static Acute Toxicity Test with the 

Rainbow Trout (Oncorhynchus mykiss): (Final Report): Lab Project Number: WL-94-080: 139A-167: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 40 p. 

MRID: 44295775 Graves, W.; Swigert, J. (1994) MON 37500: A 96-Hour Static Acute Toxicity Test with the

Bluegill (Lepomis macrochirus): (Final Report): Lab Project Number: WL-94-081: 139A-168: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 40 p. 

Guideline: 72-2 Acute Toxicity to Freshwater Invertebrates

MRID: 44295776 Graves, W.; Swigert, J. (1994) MON 37500: A 48-Hour Static Acute Toxicity Test with the 

Cladoceran (Daphnia magna): (Final Report): Lab Project Number: WL-94-082: 139A-169: RD 1353. Unpublished 

study prepared by Wildlife International Ltd. 40 p. 

Guideline: 72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID: 44295777 Graves, W.; Swigert, J. (1995) MON 37500: A 96-Hour Static Acute Toxicity Test with the 

Saltwater Mysid (Mysidopsis bahia): (Final Report): Lab Project Number: WL-94-391: 139A-181: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 39 p. 
63

MRID: 44295778 Graves, W.; Swigert, J. (1995) MON 37500: A 96-Hour Shell Deposition Test with the Eastern 

Oyster (Crassostrea virginica): (Final Report): Lab Project Number: WL-94-393: 139A-180: RD 1353. Unpublished 

study prepared by Wildlife International Ltd. 39 p. 

MRID: 44309304 Graves, W.; Swigert, J. (1995) MON 37500: A 96-Hour Static Acute Toxicity Test with the 

Sheepshead Minnow (Cyprinodon variegatus): Lab Project Number: WL-94-392: 139A-182: RD 1353. Unpublished 

study prepared by Wildlife International Ltd. 39 p. 

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

MRID: 44295779 Graves, W.; Mank, M.; Swigert, J. (1996) MON 37500: An Early Life-Stage Toxicity Test with 

the Rainbow Trout (Oncorhynchus Mykiss): (Final Report): Lab Project Number: WL-95-252: 139A-192: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 82 p. 

MRID: 44295780 Graves, W.; Mank, M.; Swigert, J. (1996) MON 37500: A Static-Renewal Life-Cycle Toxicity 

Test with the Cladoceran (Daphnia magna): (Final Report): Lab Project Number: WL-96-043: 139A-194: RD 1353. 

Unpublished study prepared by Wildlife International Ltd. 77 p. 

Guideline: 81-1 Acute oral toxicity in rats

MRID: 44295737 Bonnette, K. (1993) Acute Oral Toxicity Study in Rats with MON 37500: (Final Report): Lab 

Project Number: SB-92-480: 3044. 391: RD 1353. Unpublished study prepared by Springborn Laboratories, Inc. 

19 p. 

MRID: 44295738 Blaszcak, D. (1995) Acute Oral Toxicity Study in Rats with MON 37532: (Final Report): Lab 

Project Number: PL-95-030: 95-1156: RD 1353. Unpublished study prepared by Pharmaco LSR. 20 p. 

MRID: 45116102 Blaszcak, D. (1999) MON 37525: Acute Oral Toxicity Study in Rats: Lab Project Number: HU99-174: 99-0529: 1500. Unpublished study prepared by Huntingdon Life Sciences. 28 p. {OPPTS 870.1100} 

Guideline: 81-2 Acute dermal toxicity in rabbits or rats

MRID: 44295739 Bonnette, K. (1993) Acute Dermal Toxicity Study in Rats with MON 37500: (Final Report): Lab 

Project Number: SB-92-480: 3044.392: RD 1353. Unpublished study prepared by Springborn Laboratories, Inc. 17 

p. 

MRID: 44295740 Blaszcak, D. (1995) Acute Dermal Toxicity Study in Rats with MON 37532: Lab Project 

Number: PL-95-031: 95-1157: RD 1353. Unpublished study prepared by Pharmaco LSR. 21 p. 

MRID: 45116103 Blaszcak, D. (1999) MON 37525: Acute Dermal Toxicity Study in Rats: Lab Project Number: 

HU-99-175: 99-0530: 1500. Unpublished study prepared by Huntingdon Life Sciences. 26 p. {OPPTS 870.1200} 

Guideline: 81-3 Acute inhalation toxicity in rats

MRID: 44295745 Bechtel, C. (1994) (Amended) Report for Acute Inhalation Study (in Rats) of MON 37500 

Herbicide: Lab Project Number: ML-94-003: EHL 94004: RD 1353. Unpublished study prepared by Monsanto Co. 

41 p. 

MRID: 44295746 Bechtel, C. (1995) Acute Inhalation Study (in Rats) of MON 37532: Lab Project Number: ML95-035: EHL 95012: RD 1353. Unpublished study prepared by Monsanto Co. 40 p. 

MRID: 45116104 Bechtel, C. (2000) Acute Inhalation Study of MON 37525 in Rats: Lab Project Number: MSE-N 

99057: ML-99-166: MSL-16575. Unpublished study prepared by Monsanto Company, Metabolism and Safety 

Evaluation-Newstead. 43 p. {OPPTS 870.1300} 

Guideline: 81-4 Primary eye irritation in rabbits
64

MRID: 44295741 Bonnette, K. (1993) Primary Eye Irritation Study in Rabbits with MON 37500: (Final Report): 

Lab Project Number: SB-92-480: 3044.393: RD 1353. Unpublished study prepared by Springborn Laboratories, 

Inc. 19 p. 

MRID: 44295742 Blaszcak, D. (1995) Primary Eye Irritation Study in Rabbits with MON 37532: Lab Project 

Number: PL-95-032: 95-1159: RD 1353. Unpublished study prepared by Pharmaco LSR. 24 p. 

MRID: 45116105 Blaszcak, D. (1999) MON 37525: Primary Eye Irritation Study in Rabbits: Lab Project Number: 

HU-99-176: 99-0532: 1500. Unpublished study prepared by Huntingdon Life Sciences. 33 p. {OPPTS 8700.2400} 

Guideline: 81-5 Primary dermal irritation

MRID: 44295743 Bonnette, K. (1993) Primary Skin Irritation Study in Rabbits with MON 37500: (Final Report): 

Lab Project Number: SB-92-480: 3044.394: RD 1353. Unpublished study prepared by Springborn Laboratories, 

Inc. 16 p. 

MRID: 44295744 Blaszcak, D. (1995) Primary Dermal Irritation Study in Rabbits with MON 37532: Lab Project 

Number: PL-95-033: 95-1158: RD 1353. Unpublished study prepared by Pharmaco LSR. 20 p. 

MRID: 45116106 Blaszcak, D. (1999) MON 37525: Primary Dermal Irritation Study in Rabbits: Lab Project 

Number: HU-99-177: 99-0531: 1500. Unpublished study prepared by Huntingdon Life Sciences. 27 p. {OPPTS 

870.2500} 

Guideline: 81-6 Dermal sensitization

MRID: 44295747 Bonnette, K. (1993) Dermal Sensitization Study in Guinea Pigs with MON 37500--Modified 

Buehler Design: Lab Project Number: SB-92-481: 3044.395: RD 1353. Unpublished study prepared by Springborn 

Laboratories, Inc. 22 p. 

MRID: 44295748 Blaszcak, D. (1995) Guinea Pig Maximization Test with MON 37532: Lab Project Number: PL95-034: 95-1160: RD 1353. Unpublished study prepared by Pharmaco LSR. 31 p. 

MRID: 45116107 Blaszcak, D. (1999) MON 37525: Skin Sensitization in Guinea Pigs (Buehler Method): Lab 

Project Number: HU-99-178: 99-0533: 1500. Unpublished study prepared by Huntingdon Life Sciences. 32 p. 

{OPPTS 870.2600} 

Guideline: 81-8 Acute neurotoxicity screen study in rats

MRID: 44295749 Branch, D.; Thake, D.; Kaempfe, T.; et al. (1997) Acute Neurotoxicity Study of MON 37500 in 

Sprague-Dawley Rats: Lab Project Number: EHL 95100: MSL 14959: RD 1353. Unpublished study prepared by 

Monsanto Co. 292 p. 

Guideline: 82-1 Subchronic Oral Toxicity: 90-Day Study

MRID: 44295750 Naylor, M.; Thake, D. (1995) Pilot Three Month Study of MON 37500 Administered in Feed to 

Sprague-Dawley Rats: Lab Project Number: ML-93-63: EHL 93002: RD 1353. Unpublished study prepared by 

Monsanto Co. 486 p. 

MRID: 44295751 Naylor, M.; Thake, D. (1996) Three Month Study of MON 37500 Administered by Capsule to 

Beagle Dogs: Lab Project Number: ML-94-324: EHL 94108: RD 1353. Unpublished study prepared by Monsanto 

Co. 339 p. 

Guideline: 82-2 21-day dermal-rabbit/rat

MRID: 44295752 Naylor, M.; Thake, D. (1997) Rangefinding and One Month Dermal Study of MON 37500 in CD 

Rats: Lab Project Number: ML-96-115: EHL 96050: EHL 96051. Unpublished study prepared by Monsanto Co. 

260 p. 
65

MRID: 44443701 Naylor, M. (1997) Addendum to: Rangefinding and One Month Dermal Study of MON 37500 in 

CD Rats: Lab Project Number: ML-96-115: EHL 96050/96051: MSL 15001. Unpublished study prepared by 

Monsanto Co. 12 p. 

Guideline: 82-7 Subchronic Neurotoxicity

MRID: 44295753 Kaempfe, T.; Thake, D.; Branch, D.; et al. (1997) Subchronic Neurotoxicity Study of MON 

37500 Administered in Feed to Sprague-Dawley Rats: Lab Project Number: ML-96-045: EHL 96012: MSL 14915. 

Unpublished study prepared by Monsanto Environmental Health Lab. 389 p. 

Guideline: 83-1 Chronic Toxicity

MRID: 44295754 Naylor, M.; Ruecker, F. (1997) One Year Study of MON 37500 Administered by Capsule to 

Beagle Dogs: Lab Project Number: ML-95-199: EHL 95042: MSL 15007. Unpublished study prepared by 

Monsanto Co. and Experimental Pathology Laboratories, Inc. 446 p. 

MRID: 44295759 Naylor, M.; Ruecker, F. (1997) Combined Chronic Toxicity/Oncogenicity Study of MON 37500 

Administered in the Diet to Sprague-Dawley Rats: Lab Project Number: ML-94-118: EHL 94051: RD 1353. 

Unpublished study prepared by Monsanto Co. 2309 p. 

MRID: 44443702 Naylor, M. (1997) Addendum to: Combined Chronic Toxicity/Oncogenicity Study of MON 

37500 Administered in the Diet to Sprague-Dawley Rats: Lab Project Number: ML-96-118: EHL 94051: 82166. 

Unpublished study prepared by Monsanto Co. 8 p. 

MRID: 44532801 Naylor, M. (1998) Addendum to: One Year Study of MON 37500 Administered by Capsule to 

Beagle Dogs: Lab Project Number: ML-95-199: EHL 95042. Unpublished study prepared by Monsanto Co. 8 p. 

MRID: 45079602 Dubelman, S. (2000) Determination of Sulfosulfuron Concentration in Rat Bladder Calculi 

(Addendum to: Combined Chronic Toxicity/Oncogenicity Study of Mon 37500 Administered in the Diet to CD-1 

Sprague-Dawley Rats): Lab Project Number: ML-94-118: EHL 9051: MSL-14843. Unpublished study prepared by 

Monsanto Co. 51 p. 

Guideline: 83-2 Oncogenicity

MRID: 44295755 Naylor, M.; Thake, D. (1997) Oncogenicity Study of MON 37500 Administered in Diet to CD-1 

Mice for 18 Months: Lab Project Number: ML-94-119: EHL 94052: MSL 15013. Unpublished study prepared by 

Monsanto Co. and Experimental Pathology Laboratories, Inc. 1726 p. 

MRID: 44295759 Naylor, M.; Ruecker, F. (1997) Combined Chronic Toxicity/Oncogenicity Study of MON 37500 

Administered in the Diet to Sprague-Dawley Rats: Lab Project Number: ML-94-118: EHL 94051: RD 1353. 

Unpublished study prepared by Monsanto Co. 2309 p. 

MRID: 44443702 Naylor, M. (1997) Addendum to: Combined Chronic Toxicity/Oncogenicity Study of MON 

37500 Administered in the Diet to Sprague-Dawley Rats: Lab Project Number: ML-96-118: EHL 94051: 82166. 

Unpublished study prepared by Monsanto Co. 8 p. 

MRID: 44532803 Naylor, M. (1998) Addendum to: Oncogenicity Study of MON 37500 Administered in Diet to 

CD-1 Mice for 18 Months: Lab Project Number: ML-94-119: EHL 94052. Unpublished study prepared by 

Monsanto Co. 24 p. 

MRID: 45079601 Hard, G. (1999) Expert Report on Renal Histopathologic Changes in a Mouse Study with MON 

37500 (Sulfosulfuron): Addendum to Oncogenicity Study of Mon 37500 Administered in Diet to CD-1 Mice for 18 

Months: Lab Project Number: ML-94-119: MSL 15013: 1503. Unpublished study prepared by Monsanto Co. 10 p. 

MRID: 45079602 Dubelman, S. (2000) Determination of Sulfosulfuron Concentration in Rat Bladder Calculi 

(Addendum to: Combined Chronic Toxicity/Oncogenicity Study of Mon 37500 Administered in the Diet to CD-1 
66

Sprague-Dawley Rats): Lab Project Number: ML-94-118: EHL 9051: MSL-14843. Unpublished study prepared by 

Monsanto Co. 51 p. 

MRID: 46950601 Naylor, M.; Thake, D. (1997) Oncogenicity Study of MON 37500 Administered in Diet to CD-1 

Mice for 18 Months. Unpublished study prepared by University of Nebraska. 7 p.

Guideline: 83-3 Teratogenicity -- 2 Species

MRID: 44295756 Holson, J. (1994) A Developmental Study of MON 37500 in Rats: Lab Project Number: WI-93-

261: WIL-50226: RD 1353. Unpublished study prepared by WIL Research Laboratories, Inc. 277 p. 

MRID: 44295757 Holson, J. (1994) A Developmental Study of MON 37500 in Rabbits: Lab Project Number: WI94-002: WIL-50227: RD 1353. Unpublished study prepared by WIL Research Laboratories, Inc. 279 p. 

MRID: 44532802 Holson, J.; Naylor, M. (1998) Addendum to: A Developmental Study of MON 37500 in Rabbits: 

Lab Project Number: WI-94-002: WIL-50227. Unpublished study prepared by WIL Research Labs., Inc. 118 p. 

Guideline: 83-4 2-generation repro.-rat

MRID: 44295758 Naylor, M.; Thake, D. (1996) Two Generation Reproduction Study of MON 37500 

Administered in the Diet to Albino Rats: Lab Project Number: ML-94-120: EHL 94053: RD 1353. Unpublished 

study prepared by Monsanto Co. and Experimental Pathology Laboratories, Inc. 1194 p. 

Guideline: 84-2 Interaction with Gonadal DNA

MRID: 44280201 Yoshida, N. (1996) Chromosomal Aberration Test of TKM-19 Using Cultured Mammalian 

Cells: Final Report: Lab Project Number: T95-2337: T-4500: K06-0494. Unpublished study prepared by Hita 

Research Labs. 28 p. 

MRID: 44295760 Stegeman, S.; Warren, J.; Kier, L. (1995) Ames/Salmonella Mutagenicity Assay of MON 37500: 

Lab Project Number: ML-94-004: EHL 94002: RD 1353. Unpublished study prepared by Monsanto Co. 59 p. 

MRID: 44295761 Stegeman, S.; Kier, L.; Asbury, K.; et al. (1996) CHO/HGPRT Gene Mutation Assay of MON 

37500: Lab Project Number: ML-95-200: EHL 95054: RD 1353. Unpublished study prepared by Monsanto Co. 64 

p. 

MRID: 44295762 Murli, H. (1996) Chromosome Aberration Study in Human Whole Blood Lymphocytes with a 

Confirmatory Assay with Multiple Harvests with MON 37500: Revised Final Report: Lab Project Number: HL-95-

201: 17146-0-449CO: RD 1353. Unpublished study prepared by Monsanto Co. and Corning Hazleton Inc. 66 p. 

MRID: 44295763 Stegeman, S.; Kier, L.; Garrett, S.; et al. (1995) Mouse Bone Marrow Micronucleus Assay of 

MON 37500: Lab Project Number: ML-94-005: EHL 94003: RD 1353. Unpublished study prepared by Monsanto 

Co. 56 p. 

MRID: 44295764 Stegeman, S.; Kier, L.; Albin, L.; et al. (1996) Mouse Bone Marrow Assay of (carbon 14) 

Radiolabeled MON 37500: Lab Project Number: ML-95-289: EHL 95106: RD 1353. Unpublished study prepared 

by Monsanto Co. 20 p. 

Guideline: 85-1 General metabolism

MRID: 44295765 Lau, H.; Kinnett, M.; Albin, L.; et al. (1996) The Absorption, Distribution, Elimination, and 

Metabolism of MON 37500 in Sprague Dawley Rats Following Oral and Intravenous Administration: Lab Project 

Number: MSL 14300: EHL 93041: RD 1353. Unpublished study prepared by Monsanto Co. 504 p. 

Guideline: 122-2 Aquatic plant growth
67

MRID: 44295781 Thompson, S.; Swigert, J. (1996) MON 37500: A 5-Day Toxicity Test with the Marine Diatom 

(Skeletonema costatum): (Final Report): Lab Project Number: WL-94-346: 139A-179: RD 1353. Unpublished study 

prepared by Wildlife International Ltd. 46 p. 

MRID: 44295782 Thompson, S.; Swigert, J. (1996) MON 37500: A 5-Day Toxicity Test with the Freshwater 

Diatom (Navicula pelliculosa): (Final Report): Lab Project Number: WL-94-347: 139A-176: RD 1353. Unpublished 

study prepared by Wildlife International Ltd. 45 p. 

Guideline: 123-1 Seed germination/seedling emergence and vegitative vigor

MRID: 44295783 Chetram, R.; Cone, C. (1997) Tier 2 Seed Germination/Seedling Emergence Nontarget 

Phytotoxicity Study Using MON 37500: Lab Project Number: MSL 14477: 94434: RD 1353. Unpublished study 

prepared by ABC Laboratories, Pan-Ag Division. 250 p. 

MRID: 44295784 Chetram, R.; Cone, C. (1995) Tier 2 Vegetative Vigor Nontarget Phytotoxicity Study Using 

MON 37500: Lab Project Number: MSL 14478: 94435: RD 1353. Unpublished study prepared by ABC 

Laboratories, Pan-Ag Division. 249 p. 

Guideline: 123-2 Aquatic plant growth

MRID: 44295785 Thompson, S.; Swigert, J. (1995) MON 37500: A 5-Day Toxicity Test with the Freshwater Alga 

(Selenastrum capricornutum): Lab Project Number: WL-94-096: 139A-173: RD 1353. Unpublished study prepared 

by Wildlife International Ltd. 56 p. 

MRID: 44295786 Thompson, S.; Swigert, J. (1996) MON 37500: A 5-Day Toxicity Test with the Freshwater Alga 

(Anabaena flos-aquae): (Final Report): Lab Project Number: WL-94-348: 139A-177: RD 1353. Unpublished study 

prepared by Wildlife International Ltd. 48 p. 

MRID: 44295787 Thompson, S.; Swigert, J. (1996) MON 37500: A 14-Day Toxicity Test with Duckweed (Lemna 

gibba G3): (Final Report): Lab Project Number: WL-94-216: 139A-174: RD 1353. Unpublished study prepared by 

Wildlife International Ltd. 45 p. 

Guideline: 141-1 Honey bee acute contact

MRID: 44295788 Palmer, S.; Beavers, J. (1994) MON 37500: An Acute Contact Toxicity Study with the Honey 

Bee: (Final Report): Lab Project Number: WL-94-071: 139-382A: RD 1353. Unpublished study prepared by 

Wildlife International Ltd. 19 p. 

Guideline: 161-1 Hydrolysis

MRID: 44295720 Mayo, B.; Langford-Pollard, A. (1994) The Hydrolysis of (carbon 14)-MON 37500: Lab Project 

Number: MSL 13700: MTO 34/932281: RD 1353. Unpublished study prepared by Huntingdon Research Centre 

Ltd. 124 p. 

Guideline: 161-2 Photodegradation-water

MRID: 44295721 Kurtzweil, M. (1993) Aqueous Photolysis Studies of MON 37500: Lab Project Number: MSL 

12898: RD 1353: 92-13-M33. Unpublished study prepared by Monsanto Co. 137 p. 

Guideline: 161-3 Photodegradation-soil

MRID: 44295722 Estigoy, L.; Shepler, K. (1996) Photodegradation of (carbon14)MON 37500 in/on Soil by 

Natural Sunlight: Lab Project Number: MSL 14021: 482W: RD 1353. Unpublished study prepared by PTRL West, 

Inc. 112 p. 

Guideline: 162-1 Aerobic soil metabolism
68

MRID: 44295723 McMullan, P.; Lundry, D. (1995) Aerobic Soil Metabolism of MON 37500: Lab Project 

Number: MSL 13750: RD 1353: 93-13-M1. Unpublished study prepared by Monsanto Co. 205 p. 

MRID: 44295724 Mayo, B.; McEwen, A. (1996) The Aerobic Soil Metabolism of (carbon 14)-MON 37500: Lab 

Project Number: MSL 14019: MTO 35/942911: RD 1353. Unpublished study prepared by Huntingdon Life 

Sciences Ltd. 119 p. 

Guideline: 162-3 Anaerobic aquatic metab.

MRID: 44295725 Skinner, W. (1997) Anaerobic Aquatic Metabolism of (carbon 14)-MON 37500: Lab Project 

Number: MSL 14022: 460W: RD 1353. Unpublished study prepared by PTRL West, Inc. 194 p. 

Guideline: 162-4 Aerobic aquatic metab.

MRID: 44295726 Voelkel, W. (1996) MON 37500: Degradation and Metabolism in Aerobic Aquatic Systems: Lab 

Project Number: MSL 14023: 379642: RD 1353. Unpublished study prepared by RCC Umweltchemie Ag. 202 p. 

Guideline: 163-1 Leach/adsorp/desorption

MRID: 44295727 Mayo, B.; McEwen, A. (1995) The Soil Column Leaching of Aged Residues: MON 37500: Lab 

Project Number: MSL 13702: MTO 37/942626: RD 1353. Unpublished study prepared by Huntingdon Research 

Centre Ltd. 87 p. 

MRID: 44295728 Mayo, B.; McEwen, A. (1995) (Carbon 14)-MON 37500: The Adsorption/Desorption on Soil: 

Lab Project Number: MSL 13701: MTO 38/942137: RD 1353. Unpublished study prepared by Huntingdon 

Research Centre Ltd. 108 p. 

MRID: 44295729 Atkins, R. (1996) Soil Adsorption/Dessorption of (carbon 14)-CP 180422 by the Batch 

Equilibrium Method: Lab Project Number: MSL 14409: 974: RD 1353. Unpublished study prepared by PTRL East, 

Inc. 92 p. 

MRID: 44295730 Atkins, R. (1996) Soil Adsorption/Dessorption of (carbon 14)-CP 147937 by the Batch 

Equilibrium Method: Lab Project Number: MSL 14410: 975: RD 1353. Unpublished study prepared by PTRL East, 

Inc. 91 p. 

MRID: 44309303 Nadeau, R.; Sidhu, R. (1997) Adsorption/Desorption Studies of 4,6-Dimethoxy-2-

aminopyrimidine, A Soil Metabolite of MON 37500: Lab Project Number: MSL 14437: RD 1353. Unpublished 

study prepared by Monsanto Co. 85 p. 

Guideline: 164-1 Terrestrial field dissipation

MRID: 44295731 Mayo, B.; McEwen, A. (1995) Degradation of (carbon 14)-MON 37500 on Three Soils: Lab 

Project Number: MSL 14020: MTO 40/943154: RD 1353. Unpublished study prepared by Huntingdon Research 

Centre Ltd. 136 p. 

MRID: 44295732 McMullan, P. (1996) Terrestrial Field Dissipation Study with (carbon 14)-MON 37500: Lab 

Project Number: RD 1353: MSL 14371. Unpublished study prepared by Monsanto Co., PTRL-West, Inc. and Plant 

Sciences, Inc. 521 p. 

MRID: 44295733 Steinmetz, J. (1996) Terrestrial Field Soil Dissipation of MON 37500 (1995 Use Season): Lab 

Project Number: MSL 14192: RD 1353: 95-13-R-1. Unpublished study prepared by Monsanto Co. 286 p. 

Guideline: 165-1 Confined rotational crop

MRID: 44295735 Kurtzweil, M. (1996) Confined Rotational Crop Study with MON 37500: Lab Project Number: 

MSL 14130: 474W-1: RD 1353. Unpublished study prepared by Monsanto Co. and PTRL West, Inc. 367 p. 
69

MRID: 45096402 Kunda, U. (1998) Stability of MON 37500 Residues in Rotation Crops During Frozen Storage: 

Lab Project Number: MSL-14577: RD 1504: RES-082-94. Unpublished study prepared by Monsanto Co. 80 p. 

{OPPTS 860.1380} 

Guideline: 165-2 Field rotational crop

MRID: 44821802 Kunda, U. (1998) Magnitude of the Residues of MON 37500 in Field Rotational Crops: Lab 

Project Number: MSL-14367: 95-13-R-5: RD1474. Unpublished study prepared by Monsanto Company and Qualls 

Agricultural Labs. 352 p. {OPPTS 860.1900} 

Guideline: 171-4B Residue Analytical Methods

MRID: 44295710 Lyle, T. (1997) Independent Laboratory Method Validation for the Determination of MON 

37500 Residues in Wheat Matrices According to EPA Notice PR 96-1 using Monsanto Method No. RES-082-94, 

Version No. 2: (Final Report): Lab Project Number: MSL 14948: 95-0076: RD 1353. Unpublished study prepared 

by EN-CAS Analytical Laboratories. 86 p. 

MRID: 44295711 Davis, K. (1996) Independent Laboratory Validation per PR Notice 96-1 of Monsanto Method 

No. RES-095-96, Version O (Determination of MON 37500 Residues in Meat/Milk Tissues): (Final Report): Lab 

Project Number: MSL 14836: 43589: RD 1353. Unpublished study prepared by ABC Laboratories, Inc. 93 p. 

MRID: 44295712 Lyle, T.; Baldi, B. (1996) Independent Method Validation Ruggedness Trial for the 

Determination of MON 37500 and Sulfonamide in Water using Monsanto Method No. RES-093-95, Version No. O, 

Entitled Analytical Method for the Determination of MON 37500 and its Metabolites in Water: (Final Report): Lab 

Project Number: MSL 14535: 95-0077: RES-093-95. Unpublished study prepared by EN-CAS Analytical 

Laboratories. 76 p. 

MRID: 44295713 Nandihalli, U. (1997) FDA Multi-Residue Method for Testing of MON 37500 and Sulfonamide 

Metabolite (CP 147937): Lab Project Number: MSL 14955: CHW 6103-198: RD 1353. Unpublished study 

prepared by Corning Hazleton, Inc. 90 p. 

MRID: 44309301 Lyle, T.; Baldi, B. (1996) Independent Method Validation Ruggedness Trial for the 

Determination of MON 37500 in Wheat Matrices using Monsanto Method No. RES-082-94, Version No. 2, Entitled 

"Analytical Method for the Determination of MON 37500 and Its Metabolites in Wheat": Lab Project Number: MSL 

14536: 95-0076: RD 1353. Unpublished study prepared by EN-CAS Analytical Laboratories. 60 p. 

MRID: 44821801 Kunda, U.; Habibi-Goudarzi, S. (1998) Confirmatory Method for MON 37500 RAC Regulatory 

Enforcement Methods: Lab Project Number: MSL-14962: 97-13-R-1: RD 1474. Unpublished study prepared by 

Monsanto Company. 138 p. 

Guideline: 171-4C Magnitude of the Residue [by commodity]

MRID: 44295714 Allan, J. (1996) Stability of MON 37500 Residues in Wheat Raw Agricultural Commodities 

During Frozen Storage: Lab Project Number: MSL 14394: RD 1353: 94-13-R-2. Unpublished study prepared by 

Monsanto Co. 69 p. 

MRID: 44295715 Sidhu, R. (1997) Stability of MON 37500 Residues in Dairy Cow Milk and Meat Tissues During 

Frozen Storage: Lab Project Number: MSL 14602: RD 1353: 96-13-R-3. Unpublished study prepared by Monsanto 

Co. 110 p. 

MRID: 44295716 Kunda, U.; Mueth, M. (1997) Magnitude of the Residues of MON 37500 in Wheat Raw 

Agricultural Commodities: Lab Project Number: MSL 14396: RD 1353: 94-13-R-4. Unpublished study prepared by 

Monsanto Co. 597 p. 
70

MRID: 44295717 Kunda, U. (1997) Magnitude of the Residues of MON 37500 in Wheat Processed Commodities: 

Lab Project Number: MSL 14436: RD 1353: 94-13-R-5. Unpublished study prepared by Monsanto Co., American 

Agricultural Services, Inc. and Crop Guard Research, Inc. 147 p. 

MRID: 44295718 Sidhu, R. (1997) Magnitude of MON 37500 Residues in Milk and Edible Tissues of Lactating 

Dairy Cattle: Lab Project Number: MSL 14559: 95128B: RD 1353. Unpublished study prepared by Monsanto Co. 

and Southwest Bio-Labs., Inc. 329 p. 

Guideline: 171-4A2 Nature of the Residue in Plants

MRID: 44295707 Nadeau, R.; Kurtzweil, M. (1994) Metabolism of MON 37500 in Wheat: Lab Project Number: 

MSL 13043: 408W: RD 1353. Unpublished study prepared by Monsanto Co. 285 p. 

Guideline: 171-4A3 Nature of the Residue in Livestock

MRID: 44295708 Nadeau, R.; Kinnett, M.; Chott, R.; et al. (1996) Metabolism of MON 37500 in Laying Hens: 

Final Report: Lab Project Number: MSL 14000: EHL 95020: RD 1353. Unpublished study prepared by Monsanto 

Co. 203 p. 

MRID: 44295709 Nadeau, R.; Fujiwara, H.; Solsten, R.; et al. (1995) Metabolism of MON 37500 in Lactating 

Goats: (Final Report): Lab Project Number: MSL 14001: 41713: RD 1353. Unpublished study prepared by 

Monsanto Co. 228 p. 

Guideline: 830.1700 Preliminary analysis

MRID: 47156801 Ha, S. (2005) Analysis of Sulfosulfuron and Production Impurities in Sulfosulfuron Technical. 

Project Number: RD/1688, V/28134A. Unpublished study prepared by Valent Dublin Laboratory. 166 p.

Guideline: 860.1500 Crop field trials

MRID: 46753801 Moran, S. (2005) Magnitude of the Residues of Sulfosulfuron and Its Metabolites in Grasses 

From Pastures and Rangelands After Treatment with MON 37503. Project Number: 04/13/R/1, MSL/19348, 1661. 

Unpublished study prepared by Carringers, Inc., Monsanto Company and Agricultural Systems Associates. 283 p.

Non-Guideline Study

MRID: 44280200 Citation: Monsanto Co. (1997) Submission of Toxicology Data in Support of FIFRA 6(a)(2) for 

MON 37500 Experimental Herbicide. Transmittal of 1 Study. 

MRID: 44295700 Citation: Monsanto Co. (1997) Submission of Product Chemistry, Toxicity, Residue, 

Environmental Fate, Exposure, and Risk Data in Support of the Application for Registration of MON 37500 

Herbicide, MON 37503NC Herbicide for Non-Crop Uses, MON 37503W Herbicide for Wheat and for Tolerances 

for MON 37500 (Sulfosulfuron) in Wheat Raw Agricultural Commodities and Animal Products. Transmittal of 90 

Studies. 

MRID: 44295701 Citation: Dirks, R. (1997) Reduced Risk Pesticide Rationale for Sulfosulfuron: Lab Project 

Number: RD 1353. Unpublished study prepared by Monsanto Co. 234 p. 

MRID: 44295706 Citation: Singh, H.; Nadeau, R. (1997) Overview of the Residue Chemistry Studies of MON 

37500: Lab Project Number: MSL 15046: RD 1353. Unpublished study prepared by Monsanto Co. 25 p. 

MRID: 44295719 Citation: Moran, S. (1997) The Environmental Fate of MON 37500: A Review of Laboratory 

and U. S. Field Studies: Lab Project Number: MSL 15045: RD 1353. Unpublished study prepared by Monsanto Co. 

24 p. 

MRID: 44295734 Citation: Allan, J. (1996) Stability of Residues of MON 37500 and its Major Metabolite in Soil 

During Frozen Storage: Lab Project Number: MSL 14395: RD 1353: RES-090-95. Unpublished study prepared by 

Monsanto Co. 72 p. 
71

MRID: 44295736 Citation: Naylor, M. (1997) MON 37500: Toxicology Overview and Risk Assessment: Lab 

Project Number: RD 1353. Unpublished study prepared by Monsanto Co. 28 p. 

MRID: 44295766 Citation: Cowell, J. (1996) Pesticide Handlers Exposure Assessment for Uses of MON 37500 

Herbicide: Lab Project Number: RD 1353. Unpublished study prepared by Monsanto Co. 15 p. 

MRID: 44295767 Citation: McKee, M.; Gustafson, D.; Roloff, M.; et al. (1997) MON 37500: Ecotoxicology 

Overview and Risk Assessment: Lab Project Number: RD 1353. Unpublished study prepared by Monsanto Co. 14 

p. 

MRID: 44295789 Citation: Palmer, S.; Beavers, J. (1995) MON 37500: An Acute Oral Toxicity Study with the 

Honey Bee: (Final Report): Lab Project Number: WL-94-083: 139-390: RD 1353. Unpublished study prepared by 

Wildlife International Ltd. 21 p. 

MRID: 44295790 Citation: Dirks, R. (1997) FQPA Supplemental Information for Sulfosulfuron: Lab Project 

Number: RD 1379. Unpublished study prepared by Monsanto Co. 11 p. 

MRID: 44309300 Citation: Monsanto Co. (1997) Submission of Residue, Environmental Fate and Toxicity Data 

in Support of the Registration and Petition for MON 37500 (Sulfosulfuron) Herbicide. Transmittal of 4 Studies. 

MRID: 44309302 Citation: Lyle, T.; Baldi, B. (1996) Independent Method Validation Ruggedness Trial for the 

Determination of MON 37500 and Sulfonamide in Soil Using Monsanto Method No. RES-090-95, Version No. O, 

Entitled "Analytical Method for the Determination of MON 37500 and Its Metabolites in Soil": Lab Project 

Number: MSL 14534: 95-0075: RD 1353. Unpublished study prepared by EN-CAS Analytical Laboratories. 78 p. 

MRID: 44443700 Citation: Monsanto Co. (1997) Submission of Toxicology Data in Support of the Application 

for Registration of MON 37500 Technical, MON 37503W and MON 37503NC Herbicide. Transmittal of 2 Studies. 

MRID: 44532800 Citation: Monsanto Co. (1998) Submission of Toxicity Data in Support of the Application for 

Registration of MON 37503W Herbicide and Mon 37503NC Herbicide and Petition for Tolerance of MON 37500 

(Sulfosulfuron) Technical on Wheat. Transmittal of 3 Studies. 

MRID: 44636200 Citation: Monsanto Company (1998) Submission of Environmental Fate Data in Support of the 

Application for Registration of MON 37500 and MON 37503. Transmittal of 1 Study. 

MRID: 44636201 Citation: Dirks, R.; Moran, S. (1998) MON 37500 (Sulfosulfuron) Metabolite Herbicidal 

Activity: Lab Project Number: RD 1432. Unpublished study prepared by Monsanto Company. 10 p. 

MRID: 44665100 Citation: Monsanto Company (1998) Submission of Public Interest Documents in Support of 

the Application for Registration of Maverick Herbicide, and MON 37500 Technical, and the Petition for Tolerance 

of MON 37500 in/on Wheat RAC's and Animal Products. Transmittal of 3 Studies. 

MRID: 44665101 Citation: Dirks, R. (1998) Public Interest Document for Maverick (MON 37500) Herbicide: 

Volume I: Agro-Econonmic Benefits: Lab Project Number: RD 1442. Unpublished study prepared by Monsanto 

Company. 57 p. 

MRID: 44665102 Citation: Dirks, R. (1998) Public Interest Document for Maverick (MON 37500) Herbicide: 

Volume 2: Appendices: Lab Project Number: RD 1442: RD 1353: MSL-15046. Unpublished study prepared by 

Monsanto Company. 252 p. 

MRID: 44665103 Citation: Dirks, R. (1998) Public Interest Document for Maverick (MON 37500) Herbicide: 

Volume 3: References: Lab Project Number: RD 1442. Unpublished study prepared by Monsanto Company. 433 p. 

MRID: 44763100 Citation: Monsanto Company (1999) Submission of Pesticide Use Data in Support of the 

Applications for Registration of Mon 37503 and Mon 37500 Technical and the Petition for Tolerance of 

Sulfosulfuron in/on Wheat Raw Agricultural Commodities and Animal Products. Transmittal of 1 Study. 
72

MRID: 44763101 Citation: Honegger, J.; Dirks, R. (1999) Information in Support of the Aerial Application of 

Maverick Herbicide: Lab Project Number: RD 1465. Unpublished study prepared by Monsanto Company. 94 p. 

MRID: 44821800 Citation: Monsanto Company (1999) Submission of Residue Chemistry Data in Support of the 

Applications for Registration of MON 37503 and MON 37500 Technical and the Petition for Tolerance of 

Sulfosulfuron in/on Wheat, RACs, and Animal Products. Transmittal of 2 Studies. 

MRID: 45079600 Citation: Monsanto Company (2000) Submission of Toxicity Data in Support of the 

Registration of Sulfosulfuron. Transmittal of 2 Studies. 

MRID: 45096400 Citation: Monsanto Co. (2000) Submission of Residue Data in Support of the Registration of 

MON 37500. Transmittal of 2 Studies. 

MRID: 45096401 Citation: Mannion, R.; Moran, S. (2000) Responses to Agency Questions on Sulfosulfuron 

Limited Field Rotation Crop Study: Lab Project Number: 1504. Unpublished study prepared by Monsanto Co. 8 p. 

{OPPTS 860.1900} 

MRID: 45116100 Citation: Monsanto Company (2000) Submission of Product Chemistry and Toxicity Data in 

Support of the Registration of MON 37525 Herbicide. Transmittal of 7 Studies. 

MRID: 45362800 Citation: Monsanto Company (2001) Submission of Toxicity Data in Support of the 

Registration of Sulfosulfuron. Transmittal of 1 Study. 

MRID: 45362801 Citation: Healy, C. (2001) Studies on the Relevance of Kidney and Urinary Bladder Tumors in 

Chronic Studies with Sulfosulfuron: Lab Project Number: 1536. Unpublished study prepared by Monsanto 

Company. 15 p. 

MRID: 45411300 Citation: Monsanto Company (2001) Submission of Product Chemistry Data in Support of the 

Registration of MON 37525W Herbicide and MON 37525NC Herbicide. Transmittal of 1 Study. 

MRID: 45643400 Citation: Monsanto Company (2001) Submission of Product Chemistry Data in Support of the 

Registrations of Maverick Herbicide and Outrider Herbicide. Transmittal of 1 Study. 

MRID: 45643600 Citation: Monsanto Company (2001) Submission of Toxicity Data in Support of the Amended 

Registrations of Maverick Herbicide, Outrider Herbicide and Maverick Pro Herbicide. Transmittal of 1 Study. 

MRID: 45643601 Citation: Cohen, S.; Arnold, L. (2001) Effects of Dietary Sulfosulfuron on Urinary Parameters 

and the Bladder in Male Sprague-Dawley Rats: Lab Project Number: 220: 080100: 1536. Unpublished study 

prepared by University of Nebraska Medical Center. 112 p. 

MRID: 46004100 Citation: Monsanto Company (2003) Submission of Environmental Fate and Residue Data in 

Support of the Registration of Halosulfuron-Methyl. Transmittal of 3 Studies. 

MRID: 46004102 Citation: Allan, J. (2002) Validation of a Multiresidue Method For Sulfosulfuron and 

Halosulfuron Herbicides In Water Using LC/MS/MS. Project Number: 00-13-R-3, MSL-17534. Unpublished study 

prepared by Monsanto Agricultural Co. 420 p.

MRID: 46004103 Citation: Allan, J. (2002) Validation of a Multiresidue Method for Sulfosulfuron and 

Halosulfuron Herbicides in Soil Using LC/MS/MS. Project Number: 00/13/R/2, MSL/17569, ES/ME/405/03. 

Unpublished study prepared by MONSANTO COMPANY. 353 p.

MRID: 46005900 Citation: Monsanto Company (2003) Submission of Environmental Fate Data in Support of 

Sulfosulfuron and Halosulfuron. Transmittal of 2 Studies.
73

MRID: 46005901 Citation: Allan, J. (2002) Validation of a Multiresidue Method for Sulfosulfuron and 

Halosulfuron Herbicides in Water Using LC/MS/MS. Project Number: 00/13/R/3, MSL/17534, ES/ME/0404/02. 

Unpublished study prepared by Monsanto Company. 420 p.

MRID: 46005902 Citation: Allan, J. (2002) Validation of a Multiresidue Method for Sulfosulfuron and 

Halosulfuron Herbicides in Soil Using LC/MS/MS. Project Number: 00/13/R/2, MSL/17569, ES/ME/0405/03. 

Unpublished study prepared by Monsanto Company. 353 p.

MRID: 46753800 Citation: Monsanto Company (2006) Submission of Residue Data in Support of the Amended 

Registration of Maverick Herbicide and the Petition for Tolerance of Sulfosulfuron on Grass Forage, Fodder and 

Hay. Transmittal of 1 Study. 

MRID: 46950600 Citation: Monsanto Co. (2006) Submission of Toxicity Data in Support of the Registrations of 

Maverick Herbicide and Maverick C/A Herbicide. Transmittal of 1 Study.

MRID: 47156800 Citation: Monsanto Company (2007) Submission of Product Chemistry Data in Support of the 

Registration of MON 37500 Technical. Transmittal of 1 Study.

MRID: 47438900 Citation: Monsanto Company (2008) Submission of Residue Data in Support of the Amended 

Registration of Maverick Herbicide. Transmittal of 1 Study.

MRID: 47438901 Citation: Moran, S. (2008) Sampling of Bermudagrass Forage from Comparison Trial with and 

without Surfactant for Sulfosulfuron Residue Analysis. Project Number: REG/07/187, MSL0021114. Unpublished 

study prepared by Monsanto Company. 44 p.
74

Appendix B. Summary of Structure, Chemical Formulas and Common Names 

Table 1. Chemical and Common Name of Sulfosulfuron and its degradation products.

Chemical Name Common Name

N-[[(4,6-Dimethoxy-2-

pyrimidinyl)amino]carbonyl]-2-

(ethylsulfonyl)imidazo[1,2-a]pyridine-3-

sulfonamide

Sulfosulfuron

(MON 37500)

N-[[(4-Hydroxy-6-dimethoxy-2-

pyrimidinyl)amino]carbonyl]-2-

(ethylsulfonyl)imidazo[1,2-a]pyridine-3-

sulfonamide

Desmethyl metabolite

N-[[(Aminoiminomethyl)amino]carbonyl]-2-

(ethylsulfonyl)imidazo[1,2-a]pyridine-3-

sulfonamide

Guanidine metabolite

[[(4,6-Dimethoxy-2-

pyrimidinyl)amino]carbonyl]sulfamic acid

Sulfamic acid metabolite

(4,6-Dimethoxy-2-pyrimidinyl)urea Urea metabolite

2-(Ethylsulfonyl)imidazo[1,2-a]pyridine-3-

sulfonamide

Sulfonamide metabolite

4,6-Dimethoxy-2-pyrimidinamine Aminopyrimidine metabolite

2-Imino-α-oxo-1-(2H)-pyridineacetic acid Oxamic acid metabolite

N-(4,6-dimethoxy-2-pyrimidinyl)-N’-hydroxyureaN-hydroxy urea

2-(ethylsulfonyl)-imidazo[1,2-a]pyridine-3-

sulfonic acid

Sulfonic acid

2-(ethylsulfonyl)-imidazo[1,2-a]pyridine Sulfone
75
76

Appendix C. Summary of Toxicity Studies for Sulfosulfuron

Table 1 Affect of Sulfosulfuron on Birds

Chemical/Guideline No. / 

Study Type / Test Material Toxicological Effects(a) Source / Study Classification/ Exposure Groups

Sulfosulfuron/71-1 (850.2100)/

Avian Single Dose Oral 

Toxicity –

Bobwhite Quail (Colinus 

virginianus), 35 wks old (182

to 243 grams), intubation /

Technical Sulfosulfuron 

(>98.5%)

14-d LD50 = >2,250 mg a.i./kg-bw

NOAEL = 810 mg a.i./kg-bw

(No mortality observed, clinical signs of 

toxicity two highest dose, decrease body 

weight at highest dose)

Classified as practically nontoxic 

MRID 44295768 Campbell & 

Beavers, 1994 (Unpublished) / 

Acceptable/ nominal

0 (corn oil, 0.6mL/100g), 292, 486, 

810, 1350, 2250 mg a.i./kg-bw, 10

birds (5 males, 5 females) per group

Sulfosulfuron/71-1 (850.2100)/

Avian Single Dose Oral 

Toxicity –

Mallard duck (Anas 

platyrhynchos), 25 wks old

(771 to 1309 grams), intubation 

/

Technical Sulfosulfuron 

(>98.5%)

14-d LD50 = >2,216 mg a.i./kg-bw

NOAEL = 2,216 mg a.i./kg-bw

(No mortality observed, no effects on food 

consumption or body weight observed)

Classified as practically nontoxic 

MRID 44295769 Campbell & 

Beavers, 1995 (Unpublished) / 

Acceptable/ nominal

0 (corn oil, 0.6mL/100g), 288, 479,

798, 1330, 2216mg a.i./kg-bw, 10

birds (5 males, 5 females) per group

Sulfosulfuron/71-2 (850.2200)/

Avian Dietary Toxicity –

Northern Bobwhite (Colinus 

virginianus), 10-day old chicks 

/

Technical Sulfosulfuron

(>98.5%)

8-d LC50

(b)

> 5,570 mg a.i./kg-diet

NOAEC = 5,570 mg a.i./kg-diet

(No mortality observed, no effects on food 

consumption or body weight observed)

Classified as practically nontoxic

MRID 44295770 Campbell & 

Beavers, 1994 (Unpublished) / 

Acceptable/

Mean measured: 0 (2% corn oil), 

540, 961, 1725, 3060, 5570 mg 

a.i./kg-diet; 10 birds per group; 

Sulfosulfuron/71-2 (850.2200)/ 

Avian Dietary Toxicity –

Mallard duck (Anas 

platyrhynchos), 10-day old 

chicks /

Technical Sulfosulfuron

(>98.5%)

8-d LC50

(b)

> 5,110 mg a.i./kg-diet

NOAEC = 3,000 mg a.i./kg-diet

(no mortalities observed, no effects on food 

consumption; reduction in body weight at 

highest conc.)

Classified as practically nontoxic

MRID 44295771 Campbell & 

Beavers, 1994 (Unpublished) / 

Acceptable/

Mean measured: 0 (2% corn oil), 

521, 953, 1695, 3000, 5110 mg 

a.i./kg-diet; 10 birds per group; 

SULFOSULFURON/850.2300/

Avian Reproduction Toxicity –

Northern Bobwhite (Colinus 

virginianus), 19-wk old , 21-

wk test duration/

Technical Sulfosulfuron 

(98.5%)

NOAEC at least 1229 mg a.i./kg-diet, 

highest concentration tested

(No treatment-related effects were observed 

on any adult or offspring parameter at any 

treatment level)

MRID 44295772 Frey, et.al., 1996

(Unpublished) / Acceptable

Mean measured: 0, 46.9, 247 and 

1229 mg ai/kg-diet; 16 pairs (1 male 

and 1 female)
77

Chemical/Guideline No. / 

Study Type / Test Material Toxicological Effects(a) Source / Study Classification/ Exposure Groups

SULFOSULFURON/850.2300/

Avian Reproduction Toxicity –

Mallard duck (Anas 

platyrhynchos), 19-wk old , 22-

wk test duration/

Technical Sulfosulfuron 

(98.5%)

NOAEC = 245 mg a.i./kg-diet

LOAEC = 1221 mg a.i./kg-diet

(Reduced body weight in 14-d old 

hatchlings)

MRID 44295773 Frey, et.al., 1996

(Unpublished) / Acceptable

Mean measured: 0, 46.3, 245 and 

1221 mg ai/kg-diet; 16 pairs (1 male 

and 1 female)

(a) Effect levels are expressed in terms of the chemical.: mg/kg-bw is milligrams of the test material per kilogram of 

body weight; mg ai/kg-bw is milligrams of Sulfosulfuron per kilogram of body weight; mg ai/kg-diet is milligrams 

of Sulfosulfuron per kilogram of diet..

(b) 5-day exposure and 3-day post-exposure

Table 2 Affect of Sulfosulfuron on Mammals

Chemical/Guideline No. / 

Study Type / Test Material Toxicological Effects Source / Study Classification / Exposure Groups

SULFOSULFURON/ 81-1

(870.1100)/ Acute Oral – Rat 

(Sprague-Dawley), young 

adult/

Technical Sulfosulfuron

(98.9%)

14-d LD50 > 5,000 mg Sulfosulfuron/kg-bw

(No mortality observed, soft or mucoid stools 

on Days 1-3 post dosing in limit dose)

MRID 44295737 (Unpublished) 

Bonnette, 1993/ Acceptable/ 0 (corn 

oil), 5000 mg/kg; 10 rats (5 females, 

5 males) per dose

SULFOSULFURON/ 81-1

(870.1100) Acute Oral – Rat

(Sprague-Dawley), 9-12 wk 

old/

Formulation MON 37532

73.7% Sulfosulfuron

14-d LD50 > 5,000 mg/kg-bw

(No mortality or clinical signs of toxicity 

observed)

MRID 44295738 (Unpublished) 

Blaszak, 1995/ Acceptable/ 0 , 5000 

mg/kg; 10 rats (5 females, 5 males) 

per dose

SULFOSULFURON/ 81-1 

(870.1100) Acute Oral – Rat

(Sprague-Dawley) /

Formulation MON 37525

23.7% Sulfosulfuron

14-d LD50 > 5,000 mg/kg-bw

(No mortality observed; no clinical signs of 

toxicity observed in females; decreased 

activity, irregular gail and unformed stool 

observed in males during first 24 hr)

MRID 45116102 (Unpublished) 

Blaszak, 1999/ Acceptable/ 0 , 5000 

mg/kg; 10 rats (5 females, 5 males) 

per dose

SULFOSULFURON/81-2 

(870.1200) Acute Dermal 

toxicity – Rat

(Sprague-Dawley), young 

adult

Technical Sulfosulfuron

(98.9%)

LD50 > 5,000 mg/kg MRID 44295739 (Unpublished) 

Bonnette, 1993/ Acceptable/ 0, 5000 

mg/kg

SULFOSULFURON/81-5

(850.2500) Primary Skin 

Irritation – Rabbit (New 

Zealand)

Technical Sulfosulfuron

(98.9%)

Non-irritant MRID 44295743 (Unpublished) 

Bonnette, 1993/ Acceptable/ 0.5 

g/rabbit, 6 rabbits (2 males, 4 

females)
78

Chemical/Guideline No. / 

Study Type / Test Material Toxicological Effects Source / Study Classification / Exposure Groups

SULFOSULFURON/81-4 

(870.2400) Primary Eye 

Irritation – Rabbit (New 

Zealand)

Technical Sulfosulfuron

98.9%

Moderate Eye Irritant MRID 44295741 (Unpublished) 

Bonnette, 1993 / Acceptable/ 0.084 

g/eye, 6 rabbits (5 male, 1 female)

SULFOSULFURON/81-3 

(870.1300) Acute Inhalation 

Toxicity – Rat (SpragueDawley) /

Technical Sulfosulfuron

(>98.5%)

LD50 > 3.0 mg/L

(4-hour exposure, 14 d-observation period; 

clinical signs observed during or immediately 

after exposure. Transient lack of weight gain 

in females. Enlarged liver in two males) 

MRID 44295745 (Unpublished) 

Bechtel, 1994 / Acceptable/ 3.0 

mg/L, 10 exposed (5 male, 5 female)

SULFOSULFURON/83-4 

(870.3800) Reproduction 2 –

generation – rat (SpragueDawley)/

Technical Sulfosulfuron

(98.4%)

NOAEL = 312.1 mg/kg/day (5000 ppm)

LOAEL = 1312 mg/kg/day (20,000 ppm)

(Decreased weight gain in parental and 

offspring, mortality in males, and increased 

incidence of urinary tract pathology)

MRID 44295758 (Unpublished) 

Naylor & Thake, 1996/ 0, 50, 500, 

5000, 20,000 ppm, 30 

rats/sex/dose/generation 

SULFOSULFURON/83-5 

Chronic Toxicity –

Carcinogenicity rat/ 

Technical Sulfosulfuron 

(98.4%)

At 5,000 ppm urinary bladder transitional cell 

carcinoma and papilloma were observed in 

females

MRID 44295759 (Unpublished) 

Naylor & Ruecker, 1997 / 0, 50, 

500, 5000, & 20000 ppm

SULFOSULFURON/83-5 

Chronic Toxicity –

Carcinogenicity mouse/ 

Technical Sulfosulfuron 

(98.4%)

The LOEL is 3,000 ppm (393.6 mg/kg/day), 

based on gross and microscopic effects related 

to urinary calculus formation in the urinary 

bladder of males.

MRID 44295755 (Unpublished) 

Naylor & Thake, 1997 / 0, 30, 700, 

3000, and 7000 ppm

Table 3 Affect of Sulfosulfuron on Terrestrial Invertebrates

Chemical/Guideline No. / 

Study Type / Test Material Toxicological Effects Source / Study Classification/Exposure Groups

SULFOSULFURON/141-1 

(850.3020) Honey bee Contact 

Test – Honey bee (Apis 

mellifera carnica L.), 1-7 d 

old/

Technical Sulfosulfuron 

(>98.5)

48-h LD50 > 25 μg a.i./bee

(Mortality and clinical signs of toxicity in all 

treatment groups comparable to control)

MRID 44295788 Palmer & 

Beavers,1994 / Acceptable/

Nominal 0, 0 (acetone), 1.6, 3.1, 6.3, 

12.5 and 25 μg a.i./bee

50 bees/ concentration

SULFOSULFURON/ not 

applicable/Honey bee Oral 

Test – Honey bee (Apis 

mellifera carnica L.), 1-5 d old

Technical Sulfosulfuron 

(>98.5)

48-hr LC50 > 29.6 μg ai/bee

(Mortality and clinical signs of toxicity in all 

treatment groups comparable to control)

MRID 44295789 Palmer & Beavers,

1995 / Acceptable/

Nominal 0, 1.85, 3.69, 7.39, 14.8, 

29.6 μg a.i./bee

60 bees/ concentration

Table 4 Affect of Sulfosulfuron on Freshwater and Estuarine/Marine Fish
79

Chemical/Guideline No. / Study 

Type / Test Material Toxicological Effects

Source /

Study Classification / Exposure 

Groups

SULFOSULFURON /72-1

(850.1075) Acute Toxicity to 

Freshwater Fish –

Rainbow trout (Oncorhynchuss 

mykiss), ca. 79-d old, static test /

Technical Sulfosulfuron

(>98.5%)

96-h LC50 >93.6 mg a.i./L

96-h NOAEC = 93.6 mg a.i./L

(no mortality or sublethal effects 

observed for test groups)

Classified as practically non-toxic 

MRID 44295774 Graves & Swigert, 

1994 (Unpublished) / Acceptable/

Mean measured 0 (<10) and 93.6 mg 

a.i./L, 30 fish per treatment

SULFOSULFURON /72-

1(850.1075) Acute Toxicity to 

Freshwater Fish –

Bluegill Sunfish (Lepomis 

macrochirus), juvenile (22-29 mm), 

static test /

Technical Sulfosulfuron

(98.5%)

96-h LC50 > 94.6 mg a.i./L

96-h NOAEC = 94.6 mg a.i./L

(no mortality or sublethal effects 

observed for test groups)

Classified as practically non-toxic 

MRID 44295775 Graves & Swigert, 

1994 (Unpublished) /Acceptable/

Mean measured 0 (<10), and 94.6 mg 

a.i./L, 30 fish per treatment

SULFOSULFURON/72-3 

(850.1075) Acute Toxicity to 

Estuarine and Marine Organisms –

Sheepshead minnow (Cyprinodan 

variegatus), juvenile (23-29 mm), 

static) /

Technical Sulfosulfuron

(>98.5%)

96-hr LC50 > 101 mg a.i./L

96-hr NOAEC = 101 mg a.i./L

(no mortality or sublethal effects 

observed for test groups)

Classified as practically non-toxic

MRID 44309304 Graves & Swigert, 

1995 (Unpublished) /Acceptable/

Mean measured 0 (<10), and 101 mg 

a.i./L, 30 fish per treatment

SULFOSULFURON /850.1400/

Fish early-life stage toxicity test–

Rainbow trout (Oncorhynchuss 

mykiss), <24-hr old, flow-through 

test, 60-d post hatch duration /

Technical Sulfosulfuron

(98.5%)

NOAEC = 100 mg a.i./L

(No effect on survival, growth, 

hatching or swim-up at any treatment 

group compared to control)

MRID 44295779 Graves, Mank & 

Swigert, 1995 (Unpublished) / 

Acceptable/

Mean measured 0 (<2.5), 6.2, 13, 24, 

49 and 100 mg a.i./L

Table 5 Affect of Sulfosulfuron on Freshwater and Estuarine or Marine Invertebrates

Guideline No. / Study Type / Test 

Material Toxicological Effects Source / Study Classification/Exposure Groups

SULFOSULFURON/72-2 

(850/1010) Acute Freshwater 

Invertebrate toxicity test –

Waterflea (Daphnia magna), <24-h 

old, static test,/

Technical Sulfosulfuron

(98.5%)

48-h EC50 > 94.6 mg a.i./L

48-h NOAEC = 94.6 mg a.i./L

(No immobility or sublethal effects 

observed for any treatment group)

Classified as practically non-toxic 

MRID 44295776 Graves & Swigert,

1994 (Unpublished) / Acceptable/

Mean measured 0 (<10) and 94.6 

mg a.i./L

30 daphnia per test concentration
80

SULFOSULFURON/72-3

(850.1035) Acute Estuarine and 

Marine Organisms toxicity test –

Mysid shrimp (Mysidopsis bahia), 

juveniles, static test /

Technical Sulfosulfuron

(>98.5%)

96-h LC50 >106 mg a.i./L

96-h NOAEC = 106 mg a.i./L

(No mortality or sublethal effects 

observed for any treatment group; exact 

age of organisms not reported)

Classified as moderately toxic 

MRID 44295777 Graves & Swigert,

1995 (Unpublished) / 

Supplemental/

Mean measured 0 (<10) and 106 mg 

a.i./L

30 mysid per test concentration

SULFOSULFURON/72-3

(850.1025) Acute Estuarine and 

Marine Organisms toxicity test –

Shell deposition (Crassostrea 

virginica), juveniles (34-44 mm), 

static test/ 

Technical Sulfosulfuron

(>98.5%)

96-h IC50 > 116 mg a.i./L

96-h NOAEC = 116 mg a.i./L

(No effect on shell deposition at limit 

concentration; no sublethal effects 

observed)

Classified as moderately toxic 

MRID 44295778 Graves & Swigert,

1995 (Unpublished) / Acceptable/

Mean measured 0 (<10) and 116 mg 

a.i./L

30 oysters per test concentration

SULFOSULFURON/72-4

(850.1300) Chronic Freshwater 

Invertebrate toxicity test –

Waterflea (Daphnia magna), <24-h 

old, static-renewal test (3 

times/weekly), 21-d duration / 

Technical Sulfosulfuron

(98.5%)

NOAEC = 102 mg a.i./L

(No effect on survival, growth, or 

reproduction at any treatment group 

compared to control)

MRID 44295780 Graves, Mank & 

Swigert, 1996 (Unpublished) / 

Acceptable/

Mean measured 0 (<2.5), 6.5, 13, 

27, 53 and 102 mg a.i./L

10 daphnia per test concentration

Table 6 Affect of Sulfosulfuron on Aquatic Plants

Chemical/Guideline No. / 

Study Type / Test Material

EC50/IC50

Endpoint Affected

NOAEC 

Endpoint Affected

Source / Study 

Classification/ Exposure 

Groups

Nonvascular

SULFOSULFURON/122-2 

(Tier I) (850.5400) Algal 

toxicity test marine diatom 

Skeletonema costatum, static

Technical Sulfosulfuron

(>98.5%)

120-hr EC50 > 103 mg 

a.i. (total)/L

(particulates observed 

in test solution; no 

effort to remove prior to 

analysis reported)

120-hr NOAEC = 103 mg 

a.i. (total)/L

(based on cell density, 

yield, growth rate)

MRID 44295781 Thompson & 

Swigert, 1996 / Supplemental/

Mean measured 0 (<7.36) and 

103 mg a.i. (total)/L

SULFOSULFURON/122-2 

(Tier I) (850.5400) Algal 

toxicity test freshwater diatom 

Navicula pelliculosa, static /

Technical Sulfosulfuron

(>98.5%)

120-hr IC50 > 87 mg a.i. 

(total)/L

(particulates observed 

in test solution; no 

effort to remove prior to 

analysis reported)

120-hr NOAEC = 87 mg 

a.i. (total)/L

(based on cell density, 

yield, growth rate)

MRID 44295782 Thompson & 

Swigert, 1996 / Supplemental/

Mean measured 0 (<7.36) and 

87 mg a.i. (total)/L
81

Chemical/Guideline No. / 

Study Type / Test Material

EC50/IC50

Endpoint Affected

NOAEC 

Endpoint Affected

Source / Study 

Classification/ Exposure 

Groups

SULFOSULFURON/122-3

(850.5400) (Tier II) Algal 

toxicity test green algae 

Selenastrum capricornutum , 

static/

Technical Sulfosulfuron

(>98.5%)

120-hr IC50 = 0.310 mg 

a.i./L (310 μg a.i/L)

(based on area under 

curve)

(only 2 highest 

concentrations 

analyzed; NOAEC and 

EC50 value fall within 

range of unmeasured 

test concentrations)

120-hr NOAEC = 0.0926 

mg a.i./L (92.6μg a.i/L)

(based on area under 

curve)

MRID 44295785 Thompson & 

Swigert, 1995 / Supplemental/

Nominal 46.3, 92.6, 185, 369 

μg a.i./L; mean measured 542 

and 1251 μg a.i./L

SULFOSULFURON/122-3

(850.5400) (Tier II) Algal 

toxicity test blue-green algae 

Anabaena flos-aquae, static /

Technical Sulfosulfuron

(>98.5%)

120-hr IC50 = 0.560 mg 

a.i./L (560 μg a.i/L)

(based on area under 

curve)

(2 lowest test 

concentrations not 

analysted; NOAEC and 

EC50 value fall within 

range of unmeasured 

test concentrations)

120-hr IC05 = 0.038 mg 

a.i./L (38 μg a.i/L)

(based on area under 

curve)

MRID 44295786 Thompson & 

Swigert, 1996 / Supplemental/

Nominal 0.31, 0.63 mg a.i./L; 

mean measured 1.3, 2.5, 5.3 

mg a.i./L

Vascular

SULFOSULFURON/123-2 

(850.4400) (Tier II) Toxicity 

test duckweed Lemna gibba

freshwater, static

Technical Sulfosulfuron

(>98.5%)

14-d EC50 ≈ 0.985 μg 

a.i./L

(based on frond count)

(test solutions not 

analyzed)

14-d NOAEC =0.49 μg 

a.i./L 

(based on frond count)

MRID 44295787 Thompson & 

Swigert, 1996 / Supplemental/

Nominal 0.031, 0.062, 0.13, 

0.25, 0.49 and 0.985 μg a.i./L
82

Table 7 Affect of Technical Sulfuron (98.4%) on Terrestrial Plant Vegetative Vigor*

Species EC25 (lbs ai/A)1

Most Sensitive Endpoint 

Affected

NOAEC (lbs ai/A)1

Endpoint Affected

Dicot - Cabbage 0.0013 – Dry Weight 0.005 – Dry Weight

Dicot - Cucumber 0.0246 – Dry Weight 0.0078 – Dry Weight

Dicot - Lettuce 0.0043 – Dry Weight 0.002 – Dry Weight

Dicot - Radish 0.000084 – Dry Weight 0.000031 – Dry Weight

Dicot - Soybean 0.00063 – Dry Weight 0.00005 – Dry Weight (EC05)

Dicot - Tomato 0.051 – Dry Weight 0.032 – Dry Weight

Monocot - Corn 0.0074 – Dry Weight 0.0029 – Dry Weight (EC05)

Monocot - Oat 0.0054 – Dry Weight 0.0039 – Dry Weight

Monocot - Onion 0.0041 – Dry Weight 0.0039 – Dry Weight

Monocot - Rye 0.0034 – Dry Weight 0.0020 – Dry Weight

*Source: Results are MRID # 44295784 Chetram & Cone 1995 (Unpublished); Study classification: Supplemental

Bold values are the most sensitive endpoints for either the monocot or dicot

Table 8 Affect of Technical Sulfuron (98.4%) on Terrestrial Plant Seedling Emergence*

Species EC25 (lbs ai/A)1

Most Sensitive Endpoint Affected

NOAEC (lbs ai/A)1

Endpoint Affected

Dicot - Cabbage 0.0014 – Dry Weight 0.0010 – Dry Weight

Dicot - Cucumber 0.0012 – Dry Weight 0.0010 –Height

Dicot - Lettuce 0.0027 – Dry Weight 0.0010 – Height

Dicot - Radish 0.0007 – Dry Weight 0.001 – Dry Weight

0.000091 – Dry Weight (EC05)

Dicot - Soybean 0.0066 – Dry Weight 0.0020 –Height

Dicot - Tomato 0.0105 – Dry Weight 0.0020 – Dry Weight

Monocot - Corn 0.0053 – Dry Weight 0.001 –Height 

Monocot - Oat 0.0138 – Dry Weight 0.0079 – Dry Weight

Monocot - Onion 0.00077 – Dry Weight 0.0001 – Dry Weight (EC05)

Monocot - Rye 0.0078 – Dry Weight 0.0020 – Dry Weight

*Source: Results are MRID # 44295783 Chetram & Cone 1997 (Unpublished); Study classification: Supplemental

Bold values are the most sensitive endpoints for either the monocot or dicot
83

Appendix D. GENEEC2 Output

 RUN No. 1 FOR Sulfosulfuron ON NativeGras * INPUT VALUES * 

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

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE NO-SPRAY INCORP

 ONE(MULT) INTERVAL Kd (PPM ) (%DRIFT) ZONE(FT) (IN)

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

 .125( .125) 1 1 .2 1627.0 AERL_B( 13.0) .0 .0

 FIELD AND STANDARD POND HALFLIFE VALUES (DAYS) 

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

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

 (FIELD) RAIN/RUNOFF (POND) (POND-EFF) (POND) (POND) 

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

 243.89 2 N/A 2.47- 306.28 45.90 39.92

 GENERIC EECs (IN MICROGRAMS/LITER (PPB)) Version 2.0 Aug 1, 2001

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

 PEAK MAX 4 DAY MAX 21 DAY MAX 60 DAY MAX 90 DAY

 GEEC AVG GEEC AVG GEEC AVG GEEC AVG GEEC

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

 7.33 7.23 6.67 5.60 4.93
84

Appendix E. T-REX Output
85

Acute and Chronic RQs are based on the Upper Bound 

Kenaga Residues.

Chemical Name: The maximum single day residue estimation is used for 

 Use both the acute and reproduction RQs.

 Formulation

Application Rate 0.125 lbs a.i./acre RQs reported as "0.00" in the RQ tables below should be noted as

Half-life 35 days <0.01 in your assessment. This is due to rounding and significant

Application Interval 0 days figure issues in Excel.

Maximum # Apps./Year 1

Length of Simulation 1 year

Bobwhite quail LD50 (mg/kg-bw) 810.00

Mallard duck) LC50 (mg/kg-diet) 3000.00

Mallard duck NOAEL(mg/kg-bw) 0.00

Mallard duck NOAEC (mg/kg-diet) 245.00

5000.00

0.00

312.00

5000.00

Kenaga

Values

Short Grass 30.00

Tall Grass 13.75

Broadleaf plants/sm Insects 16.88

Fruits/pods/seeds/lg insects 1.88

Avian Results

Avian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g) (g bw/day) (g/day) consumed (kg-diet/day)

Small 20 5 23 114 2.28E-02

Mid 100 13 65 65 6.49E-02

Large 1000 58 291 29 2.91E-01

20 5 5 25 5.06E-03

Granivores 100 13 14 14 1.44E-02

1000 58 65 6 6.46E-02

Avian Body Adjusted LD50

Weight (g) (mg/kg-bw)

20 583.55

100 742.89

1000 1049.35

small mid large

20 100 1000 20 100 1000

Short Grass 34.17 19.48 8.72

Tall Grass 15.66 8.93 4.00

Broadleaf plants/sm Insects 19.22 10.96 4.91

Fruits/pods/seeds/lg insects 2.14 1.22 0.55 0.47 0.27 0.12

20 100 1000

Short Grass 0.06 0.03 0.01

Tall Grass 0.03 0.01 0.00

Broadleaf plants/sm insects 0.03 0.01 0.00

Fruits/pods/seeds/lg insects 0.00 0.00 0.00

Seeds (granivore) 0.00 0.00 0.00

Acute Chronic

Short Grass 0.01 0.12

Tall Grass 0.00 0.06

Broadleaf plants/sm Insects 0.01 0.07

Fruits/pods/seeds/lg insects 0.00 0.01

Avian Acute RQs

Dose-based RQs Size Class (grams)

(Dose-based EEC/adjusted LD50)

Dietary-based RQs RQs

(Dietary-based EEC/LC50 or 

NOAEC)

0

Dose-based EECs 

(mg/kg-bw) 

Endpoints

LC50 (mg/kg-diet)

Avian

Granivores(grams)

Avian Classes and Body Weights (grams)

 Upper Bound Kenaga Residues For RQ Calculation

Dietary-based EECs (ppm)

NOAEL (mg/kg-bw)

NOAEC (mg/kg-diet)

Mammals

LD50 (mg/kg-bw)

sulfosulfuron

0
86

sulfosulfuron 0 Upper bound Kenaga Residues

Mammalian Results

Mammalian Body Ingestion (Fdry) Ingestion (Fwet) % body wgt FI

Class Weight (g bwt/day) (g/day) consumed (kg-diet/day)

15 3 14 95 1.43E-02

Herbivores/ 35 5 23 66 2.31E-02

insectivores 1000 31 153 15 1.53E-01

15 3 3 21 3.18E-03

Grainvores 35 5 5 15 5.13E-03

1000 31 34 3 3.40E-02

Mammalian Body Adjusted Adjusted

Class Weight LD50 NOAEL

15 10989.15 685.72

Herbivores/ 35 8891.40 554.82

insectivores 1000 3845.80 239.98

15 10989.15 685.72

Grainvores 35 8891.40 554.82

1000 3845.80 239.98

15 35 1000 15 35 1000

Short Grass 28.60 19.77 4.58

Tall Grass 13.11 9.06 2.10

Broadleaf plants/sm Insects 16.09 11.12 2.58

Fruits/pods/seeds/lg insects 1.79 1.24 0.29 0.40 0.27 0.06

15 grams 35 grams 1000 grams

Acute Chronic Acute Chronic Acute Chronic

Short Grass 0.00 0.04 0.00 0.04 0.00 0.02

Tall Grass 0.00 0.02 0.00 0.02 0.00 0.01

Broadleaf plants/sm insects 0.00 0.02 0.00 0.02 0.00 0.01

Fruits/pods/lg insects 0.00 0.00 0.00 0.00 0.00 0.00

Seeds (granivore) 0.00 0.00 0.00 0.00 0.00 0.00

Acute Chronic

Short Grass #DIV/0! 0.006

Tall Grass #DIV/0! 0.00

Broadleaf plants/sm insects #DIV/0! 0.00

Fruits/pods/seeds/lg insects #DIV/0! 0.00

Dietary-based RQs 

(Dietary-based EEC/LC50 or 

NOAEC)

Mammal RQs

Small mammal Medium mammal Large mammal Dose-based RQs 

(Dose-based EEC/LD50 or NOAEL)

Granivores(grams)

Mammalian Classes and Body weight

Dose-Based EECs 

(mg/kg-bw)

Herbivores/ insectivores (grams)
87

Appendix F. SIP Output

Table 1. Inputs

Parameter Value

Chemical name sulfosulfuron

Solubility (in water at 25oC; mg/L) 1627

Mammalian LD50 (mg/kg-bw) 5000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 312

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2250

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 250

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

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 279.8440 279.8440

Adjusted toxicity value (mg/kg-bw) 3845.8028 239.9781

Ratio of exposure to toxicity 0.0728 1.1661

Conclusion*

Drinking water exposure 

alone is NOT 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) 1317.8700 1317.8700

Adjusted toxicity value (mg/kg-bw) 1620.9664 12.4031

Ratio of exposure to acute toxicity 0.8130 106.2529

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.
88

Appendix G. STIR Input and Output

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 sulfosulfuron

Enter Chemical Use non-ag and ag

Is the Application a Spray? (enter y or n) y

If Spray What Type (enter ground or air) air

Enter Chemical Molecular Weight (g/mole) 470.79

Enter Chemical Vapor Pressure (mmHg) 2.22E-10

Enter Application Rate (lb a.i./acre) 0.125

Toxicity Properties

Bird

Enter Lowest Bird Oral LD50 (mg/kg bw) 2250

Enter Mineau Scaling Factor 1.15

Enter Tested Bird Weight (kg) 0.178

Mammal

Enter Lowest Rat Oral LD50 (mg/kg bw) 5000

Enter Lowest Rat Inhalation LC50 (mg/L) 3

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) 5.62E-06

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 7.07E-07

Adjusted Inhalation LD50 7.53E+00

Ratio of Vapor Dose to Adjusted Inhalation LD50 9.39E-08 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.20E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 1.60E-03 Exposure not Likely Significant

Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation 

(mg/m3) 5.62E-06
89

Maximum 1-hour Vapor Inhalation Dose (mg/kg) 8.89E-07

Adjusted Inhalation LD50 1.79E+02

Ratio of Vapor Dose to Adjusted Inhalation LD50 4.98E-09 Exposure not Likely Significant

Maximum Post-treatment Spray Inhalation Dose (mg/kg) 1.51E-02

Ratio of Droplet Inhalation Dose to Adjusted Inhalation 

LD50 8.45E-05 Exposure not Likely Significant