ecological risk assessments in support of Registration Review. This document also recommends 

studies that should be included in a data call-in (DCI) to address uncertainties surrounding the 

environmental fate and potential ecological effects of prosulfuron.
1 

 

Problem Formulation for the 

Environmental Fate and Ecological Risk, Endangered 

Species, and Drinking Water Assessments in Support 

of the Registration Review of Prosulfuron 

N-(((4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino)carbonyl)-2-(3,3,3-

trifluoropropyl)benzenesulfonamide 

CAS No. 94125-34-5 

PC Code 129031

Prepared by:

Karen Milians, Ph.D., Chemist 

Scott Glaberman, Ph.D., Biologist 

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

Jim Carleton, Ph.D., Senior Scientist 

Thomas Steeger, Ph.D., Senior Biologist 

Marietta Echeverria, Branch Chief 

April 17, 2012 


4 

1. Purpose 

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

and ecological effects of the registered uses of prosulfuron (N-(((4-methoxy-6-methyl-l,3,5-

triazin-2-yl)amino)carbonyl)-2-(3,3,3-trifluoropropyl)benzenesulfonamide). Prosulfuron is a 

selective herbicide registered for weed control on field corn (grown for grain, silage, or seed), 

popcorn, grain sorghum (milo), wheat, barley, rye, oats, triticale, proso millet, and small grain 

harvest (Pesticide Registration Division label data report as of 10/21/2011). This document will 

provide a plan for analyzing data relevant to prosulfuron and for conducting environmental fate 

and ecological risk, endangered species, and drinking water assessments for its registered uses. 

Additionally, this problem formulation is intended to identify data gaps, uncertainties, and 

potential assumptions used to address those uncertainties relative to characterizing the ecological 

risk associated with the registered uses of prosulfuron. 

2. Problem Formulation 

2.1. Nature of Regulatory Action 

The Food Quality Protection Act of 1996 mandated the Environmental Protection Agency (EPA) 

to implement a new program for assessing the risks of pesticides, i.e., Registration Review1. 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 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 prosulfuron continues to meet the FIFRA standard for 

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

chapter in support of the registration review is intended for the initial docket opening the public 

phase of the review process. 

2.2. Previous Risk Assessments 

The Agency conducted a human health drinking water assessment in 2006 in support of two new 

uses: small grains and corn (USEPA, 2006). Estimated drinking water concentrations (EDWCs) 

in surface water were 1.87, 0.58 and 0.31 μg/L for acute, chronic and lifetime exposure, 

respectively. The groundwater acute and chronic value was 0.655 μg/L. 

 

1

 http://www.epa.gov/oppsrrd1/registration_review 
5 

3. Stressor Source and Distribution 

3.1. Mechanism of Action 

Prosulfuron belongs to the sulfonylurea (SU) herbicide family, and it inhibits the activity of the 

acetolactate synthase (ALS) enzyme in plants which is important for synthesis of branched chain 

amino acids (leucine, isoleucine, and valine). Prosulfuron is absorbed by leaves and roots of 

susceptible plants. In general, SU herbicides are less toxic to animals than plants (USEPA, 

2009). 

3.2. Overview of Pesticide Usage 

Prosulfuron was registered in 1995, and is a selective herbicide applied as a post-emergence 

treatment to control broad leaf weeds in corn, grain sorghum, winter wheat, spring wheat, barley, 

rye, oats, triticale, and proso millet. Prosulfuron is applied after emergence of both crop and 

weeds for the control of broadleaf weeds on all registered crops, and postemergence to weeds 

following small grain harvest. In addition, preemergence applications can be used in some areas 

for broadleaf weed control in sorghum. Prosulfuron is applied via ground and aerial spray. The 

maximum application rate is 0.0356 lbs active ingredient (ai) per acre on corn and sorghum. 

Based on market usage data from 2000-2010 (USEPA, 2011), usage averaged approximately 

20,000 lbs ai for 1.6 million acres treated. In addition, the average application rate over this time 

period was 0.013 lbs ai/acre. A summary of current registered products of prosulfuron is 

presented in Table 1. Table 2 depicts screening levels estimated of agricultural uses of 

prosulfuron (SLUA report, 2011). Corn represented the highest percent national use followed by 

sorghum and wheat for grain. 

Table 1. Summary of currently registered products of prosulfuron. 

Site 

Description Reg# ai % Product Name 

Max App 

Rate (lb 

ai/A) 

Application 

Method 

Application 

Method Timing 

Disallowed 

Geo Areas 

Barley 100-763 57 Peak®

Herbicide 0.0178* Aerial Postemergence 

Barley 100-763 57 Peak®

Herbicide 0.0178* Ground Postemergence 

Corn field 100-763 57 Peak®

Herbicide 0.0356* Aircraft Postemergence 

Corn field 100-763 57 Peak®

Herbicide 0.0356* Ground Postemergence 

Corn field 100-774 28.5 Exceed®

Herbicide 0.0178** Aircraft Postemergence New York 

Corn field 100-774 28.5 Exceed®

Herbicide 0.0178** Ground Postemergence 

Corn field 100-911 14.2 Spirit®

Herbicide 0.00888** Aircraft Postemergence New York 

Corn field 100-911 14.2 Spirit®

Herbicide 0.00888** Ground Postemergence 
6 

Site 

Description Reg# ai % Product Name 

Max App 

Rate (lb 

ai/A) 

Application 

Method 

Application 

Method Timing 

Disallowed 

Geo Areas 

Corn pop 100-774 28.5 Exceed

®

Herbicide 0.0178** Aircraft Postemergence New York 

Corn pop 100-774 28.5 Exceed

®

Herbicide 0.0178** Ground Postemergence 

Corn pop 100-911 14.2 Spirit

®

Herbicide 0.00888** Aircraft Postemergence New York 

Corn pop 100-911 14.2 Spirit

®

Herbicide 0.00888** Ground Postemergence 

Corn (silage) 100-774 28.5 Exceed

®

Herbicide 0.0178** Aircraft Postemergence New York 

Corn (silage) 100-774 28.5 Exceed

®

Herbicide 0.0178** Ground Postemergence 

Corn (silage) 100-911 14.2 Spirit

®

Herbicide 0.00888** Aircraft Postemergence New York 

Corn (silage) 100-911 14.2 Spirit

®

Herbicide 0.00888** Ground Postemergence 

Oats 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 

Oats 100-763 57 Peak

®

Herbicide 0.0178* Ground Postemergence 

Proso Millet 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 

Proso Millet 100-763 57 Peak

®

Herbicide 0.0178* Ground Postemergence 

Rye 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 

Rye 100-763 57 Peak

®

Herbicide 0.0178* Ground Postemergence 

Small grains 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 

Small grains 100-763 57 Peak

®

Herbicide 0.0178* Ground Postemergence 

Sorghum 100-763 57 Peak

®

Herbicide 0.0356* Aircraft Postemergence 

Sorghum 100-763 57 Peak

®

Herbicide 0.0356* Aircraft Preemergence 

Sorghum 100-763 57 Peak

®

Herbicide 0.0356* Ground Postemergence 

Sorghum 100-763 57 Peak

®

Herbicide 0.0356* Ground Preemergence 

Triticale 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 

Triticale 100-763 57 Peak

®

Herbicide 0.0178* Ground Postemergence 

Wheat 100-763 57 Peak

®

Herbicide 0.0178* Aircraft Postemergence 
7 

Site 

Description Reg# ai % Product Name 

Max App 

Rate (lb 

ai/A) 

Application 

Method 

Application 

Method Timing 

Disallowed 

Geo Areas 

Wheat 100-763 57 Peak®

Herbicide 0.0178* Ground Postemergence 

The formulation for these uses is water dispersable granules/dry flowable. 

*The label does not specify the number of applications. 

**Only a single application is allowed. 

Table 2. Screening Level Estimates of Agricultural Uses of Prosulfuron (129031) 

Sorted Alphabetically 

Percent Crop Ttd. 

Crop Lbs. A.I. Avg. Max. 

Barley <500 <1 <2.5 

Corn 8000 <2.5 5 

Sorghum 7,000 5 10 

Wheat 4,000 <1 <2.5 

 *SLUA report, 2011. 

3.3. Environmental Fate and Transport 

Summary 

The environmental fate database for prosulfuron is mostly complete in terms of laboratory and 

field dissipation data. The studies suggest that prosulfuron could be persistent and mobile. In 

addition, hydrolytic degradation is dependent on pH, with neutral and alkaline media favoring 

persistence. Photolysis is not an important degradative route for prosulfuron. Long aerobic and 

anaerobic soil metabolism half-lives were found when compared to aerobic and anaerobic 

aquatic metabolism. Prosulfuron has the potential to leach and/or be transported by runoff. The 

major degradates of prosulfuron are those formed primarily by cleavage of the sulfonylurea 

bridge, but a desmethyl analog is also a common degradate. Degradates formed by opening of 

the triazine ring have been identified in laboratory studies and in the field. Although, limited 

environmental fate data are available for degradates, the data imply that the degradate CGA159902 {2-(3,3,3-trifluoropropyl)-benzenesulfonamide}, as well as CGA-150829 and CGA300406 are likely to impact water sources due to the large percentage of residues found in 

laboratory studies. Degradate fate data are reviewed later in this section as well as in Appendix 

A. 

Fate Description 

Chemical-physical properties of prosulfuron are summarized in Table 3. Table 4 summarizes 

the environmental fate properties of prosulfuron. Laboratory data indicate that, like many 

sulfonylurea (SU) herbicides, prosulfuron is likely to be persistent and mobile. Chemical 

(abiotic) hydrolysis and microorganism-mediated processes are the major routes of degradation 

of prosulfuron. Degradation is favored in acidic media compared to neutral or alkaline 

conditions. The half-life of abiotic hydrolysis at pH 5 ranged from 3 to 15 days (average from 
8 

two radiolabels: triazine and phenyl); at pH 7 and 9 prosulfuron was stable during the 30-day 

duration of the study. 

Photodegradation (in water and soil) is not an important degradation route for prosulfuron. The 

electronic absorption spectra (UV-Vis) of the major degradates indicate that they are not prone to 

direct photolysis. 

Both the degradation and dissipation kinetics in soil and in water/sediment systems were 

reported as biphasic and monophasic (or single first order; SFO) processes. The aerobic soil 

metabolism half-lives of prosulfuron are 121, 211, 138 and 155 days calculated by SFO, primary 

half-lives ranging from 69 to 152 days and secondary half-lives ranging from 155 to 539 days for 

the triazine and phenyl label, respectively. Dissipation half-lives observed under field conditions 

ranged from 5.7 to 19.3 days (SFO). In addition, the anaerobic aquatic metabolism data showed 

that the rate of degradation is increased by the presence of water, as reflected in the shorter halflives (13 days and 20 to 25 days, for the primary and secondary half-lives, respectively; SFO 

half-lives are 17.2 and 16.4 days). From the data in the anaerobic aquatic metabolism study, 

there is evidence that most of the degradation may occur in the aqueous phase. However, 

anaerobic soil metabolism data in which the soil was not flooded showed longer half-lives, 

which indicate that reactions occurring in the aqueous phase are major contributors to 

degradation. Information of the degradates in these studies were capture in Appendix A3.

Prosulfuron has a high potential to leach to groundwater and to be transported to surface water 

via runoff and spray drift. This was observed in a field dissipation study (MRID 433877-24), 

where substantial amounts of radioactivity (mostly parent) was observed in the overflow water 

(at 15 days) following heavy rainfall events, which suggests potential for runoff. In some field 

situations (i.e. acidic soils) significant degradation might occur via hydrolysis, but generally 

prosulfuron is expected to be persistent. Prosulfuron is classified as mobile in soils by the FAO 

mobility classification criteria, with sorption coefficient (Kd) values ranging from 0.074 to 0.293 

L/kg, and organic carbon-normalized partition coefficient (Koc) values ranging from 15.2 to 41.3 

L/kgoc. However, application rates of the chemical are low, and it may be difficult to detect 

movement of the chemical from its application site. 

The low vapor pressure (<2.6 x10-8) and high water solubility of prosulfuron (43,000 mg/L at pH 

7.7) suggest that volatilization is not a major route of dissipation. The major degradates of 

prosulfuron are those formed primarily by cleavage of the sulfonylurea bridge due to hydrolysis, 

but the desmethyl analogue is also a common degradate. Degradates formed by opening of the 

triazine ring have been identified in laboratory studies and in the field. 

Prosulfuron’s octanol/water partition coefficient (Kow) decreases with increasing pH, and 

parallels the compound’s increasing water solubility in going from acidic (87 mg/L at pH 5) to 

more environmentally relevant pHs (43,000 mg/L at pH 7.7). The low octanol water partition 

coefficient (log Kow range -0.21 - 1.5) suggests the compound is unlikely to bioaccumulate in 

fish, although no bioconcentration data are available for any organism. The major degradates of 

prosulfuron are also very soluble in water, and therefore unlikely to bioaccumulate. 

Parent prosulfuron and its major degradates do not bind strongly to soils, but appear to bind 
9 

irreversibly based on the 24 hours batch equilibrium studies. Prosulfuron has the characteristics 

of a potential leacher and/or of a chemical that could be transported by dissolved runoff. 

Freundlich adsorption coefficients (Kf) of parent prosulfuron is less than 1.0 L/Kg in four 

different soils (Table A1). The appearance of high amounts of prosulfuron in leachates in soil 

column leaching studies with un-aged prosulfuron indicates a high potential for leaching. 

However, the Freundlich desorption constants are much higher than the corresponding 

adsorption constants suggesting that adsorption/desorption is not a reversible process. Moreover, 

soil column leaching with aged prosulfuron showed a significant decrease in the amount of 

prosulfuron present in the leachate and a significant increase in the amount of prosulfuron in the 

top 0 to 6 cm of the column. In the field studies, residues of prosulfuron also tend to stay in the 

top 0 to 6 inches of soil, while it undergoes degradation. 

Prosulfuron has a pKa of 3.76. Therefore, with increasing pH of the medium, the amount of the 

anionic form of prosulfuron increases. The increased predominance of anionic prosulfuron would 

reflect in an increase in its leaching and runoff potential. 

The major degradates of prosulfuron in the environmental fate laboratory studies are (formation 

exceeded 10% of applied radioactivity): CGA-159902, CGA-150829, CGA-325030, CGA188838, G-28533, CGA-325025, CGA-325028, and CGA-300406 (See Appendix A3 for 

chemical structures). The degradate G-28533 appears to be the most mobile of the degradates. 

Refer to Table A3 for further details about maximum applied radioactivity found for the 

degradates. In addition, some of these degradates are likely to impact water resources (CGA159902, CGA-150829 and CGA-300406) due to leaching and runoff potential. All major and 

minor transformation products considered as degradates of concern in the upcoming Registration 

Review Ecological Risk assessment due to structural similarity to the parent and the potential to 

occur in terrestrial and/or aquatic environments. The proposed approach and rational for 

including the aforementioned degradates in risk assessment is outlined later in this document 

(Section 7.1). 

Table 3. Summary of physical-chemical properties of prosulfuron

Parameter Value and Units Source and/or Comment

PC Code 129031 None 

CAS Number 094125-34-5 EPISuite V 4.1 

SMILES Code C(F)(F)(F)CCc1ccccc1S(=O)(=O)NC(=O)Nc2nc(C)n

c(OC)n2 

EPISuite V 4.1 

Chemical Name 1-(4-methoxy-6-methyl-triazin-2-yl)-3-(2-(3,3,3-

trifluoropropyl)-phenylsulfonyl)-urea MRID 42685247 

Empirical Formula C15H16F3N5O4S EPIsuite V 4.1 

Molecular Weight 419.38 EPISuite V 4.1 

Melting Point in °C 155 MRID:43387710 

Density at 20°C 

(g/cm3

) 1.45 MRID:43387710 
10 

Parameter Value and Units Source and/or Comment

UV/Visible Absorption 

(nm) 

pH 5: 201 and 238 

pH:7 242 (possible peak at 198) 

pH9: 242 (possible peak at 196) 

MRID:43387710 

Water Solubility 

at 25°C in mg/L 

pH 5: 87 

pH 6.8: 4000 

pH 7.7: 43000 

MRID:43387710 

Solubilities of degradates: 

CGA-150829 (pH 5.7), 300 ppm

CGA-159902 (pH 6.7), 270 ppm

CGA-300406 (pH 5.8), 400 ppm 

(unstable) 

G-28533 (pH 7), > 1000 ppm 

Vapor Pressure 

25°C in torr 

<2.6x10-8 MRID:43387710 

Henry’s Law constant Not available None 

Log Dissociation 

Constant (pKa) 

25°C 

3.76 MRID:43387710 

Log Kow 

25°C 

pH 5: 1.5 

pH 6.9: -0.21 

pH 9: -0.76 

MRID:43387710 

Table 4. Summary of other environmental fate and transport properties of prosulfuron 

Parameter Value(s) and Units 

Source (Study 

Classification; 

(A)=acceptable, 

(S)=supplemental)

Comments 

Hydrolysis 

half-life 

(at 25-30°C, in 

days) 

pH 5: 3-15 days range 

pH 7: stable 

pH 9: stable 

MRIDs: 42685246 (A),

42685247 

(A) 

Major degradation products at pH 5 

were: 

CGA-159902, CGA 150829, CGA325030, CGA-300406, and G28533. 

Aqueous Photolysis 

Half-life (days) 

Stable 

(<10 to 15% degradation in 

30 days, pH 9 only) 

MRIDs: 46685248 (A), 

42685249 (A), 

43387710 (A), 

43387711(A) 

These studies (43387710 and 

43387711) are additional data on 

the electronic absorption spectra of 

several degradates in pH 5, 7 and 9.

Soil Photolysis 

Half-life (days) 

Stable (<16 to 21% 

degradation in 30 days) 

MRIDs: 43159327 (A), 

43159328 (A) None 

Aerobic Soil 

Metabolism Halflife (days)1 121, 211, 138 and 155 days 

MRIDs: 42685250 (A), 

42685251(A), 

43387712(A) and 

43387713(A) 

None 

Anaerobic Soil 

Metabolism Halflife (days) 

 89 to123 days for 

Huntington soil; 137 to 138 

Kickapoo soil 

MRIDs: 42685252(A), 

42685253(A), 43387714 

(A), 43387715 (A) 

None

Anaerobic Aquatic 

Metabolism 17.2 and 16.4 MRIDs: 43387717 (A), 

43387716 (A) None 
11 

Parameter Value(s) and Units 

Source (Study 

Classification; 

(A)=acceptable, 

(S)=supplemental)

Comments 

Aerobic Aquatic 

Metabolism Halflife (days) 

59.5 to 68.4 MRIDs: 43387718 (A) 

and 43387719 (A) None 

Soil Partitioning 

Coefficient 

 (Kd, L/kg) 

 Huntington: loamy sand, 

0.420 %OC, pH 7.7 and 

0.07 L/kg (Kd) 

Huntington: sandy loam, 

1.79 %OC, pH 7.8 0.27 

L/kg (Kd) 

Amour: Silt loam1.58, 1.58 

%OC, pH 6.5 and 0.29 L/kg 

(Kd) 

Salvisa silty clay loam, 

0.610 %OC, pH 6.9 and 

0.252 L/kg (Kd) 

MRIDs: 42685257 (A) 

Degradates: 43159329 

(A), 43159330 (S), 

43387720 (A) and 

41656209 (A). 

The mobility of prosulfuron 

decreased with increasing soil 

organic matter. 

Organic Carbon 

Partitioning 

Coefficient (Koc, 

L/kg) 

23.2 (average of 17.6, 15.2, 

18.6 and 41.3) 

Soil Column 

Leaching 

In the unaged study 

prosulfuron was found in 

the leachate in loamy sand 

(6.6), sandy loam (pH 6.6), 

and loam (pH 6.7) with a 

radioactivity greater than 

88%. 

MRID: 42685254 (A) 

The column leaching studies 

indicate that prosulfuron adsorb 

irreversible to soils. 

Mobility appears to decrease with 

increasing soil organic matter. 

Aged Column 

Leaching 

A 30 days study indicated a 

significant reduction in the 

amount of radioactivity of 

prosulfuron recovered in the 

leachates (34-61% of the 

applied radioactivity). 

 None 
12 

Parameter Value(s) and Units 

Source (Study 

Classification; 

(A)=acceptable, 

(S)=supplemental)

Comments 

Terrestrial 

Field Dissipation 

Half-life 

(days) 

Radiolabeled studies

(Top 3 inches)

Kentucky, Silt loam, pH 

5.6, 1.9% OM, t1/2 =11.6 

(triazine) to 17.3 (phenyl) 

North Carolina, Loamy 

sand, pH 4.8, <1% OM, 

t1/2 =5.7 (phenyl) to 7.3 

(triazine) 

Cold studies (Top 6 inches)

Iowa, Sandy loam, pH 5.4, 

2.3% OM 

 Georgia, Loamy sand, pH 

7.3, 0.9% OM 

bare ground 

 Iowa, monophasic 10.2 

biphasic: primary 6.2, 

secondary 31.5 

Georgia, monophasic 10.3 

biphasic: primary 4.1 

secondary 15.0 

Corn 

Iowa, monophasic 19.3 

biphasic: primary 7.8 

secondary 43.3 

Georgia, monophasic 8.8 

biphasic: primary 4.2 

secondary 13.9 

 (4 study sites) 

MRIDs: 43159331 (A), 

43159332 (A), 

43387721 (A), 

43387722 (A), 

43387723 (A) 

Pipe studies with 

radiolabeled prosulfuron

43387724 (A), 

43387725 (A), 

43387726 (A) and 

43387727 (A) 

These studies showed much shorter 

half-lives than laboratory studies 

with no evidence of parent 

prosulfuron moving below the 12 

inch depth of soil. 

Degradates: CGA-159902, CGA150829 and CGA-300406. 

Steady State 

Bioconcentration 

Factor 

No data Not available None 

1

The “half-lives” values presented here represent the best fit for the disappearance times for each test soil 

(Huntington sandy loam and Kickapoo sandy loam). For each soil both phenyl- and triazine-ring labeled prosulfuron 

were tested; the values presented are the average of the results for each of the two soils. There was some evidence of 

two-compartment adsorption resulting in some modest increase in persistence (relative to the first order kinetics 

model) over the 365-days study period.

Identified transformation products resulting from environmental degradation of prosulfuron; N-

[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenesulfonamide are: 

• 4-methoxy-6-methyl-1,3,5-triazin-2-amine; CGA-150829 (s-triazine ring cleavage 

product)-This degradate can produce further degradation products such as 6-methyl1,3,5-triazine-2,4(1H,3H)-dione (G-28533) 

• 4-amino-6-methyl-1,3,5-triazin-2(1H)-one; CGA-188838 
13 

• 2-(3,3,3-trifluoropropyl)-benzenesulfonamide; CGA-159902 (phenyl ring cleavage 

product) 

• N-[[(4-hydroxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenesulfonamide; desmethyl prosulfuron; desmethyl CGA-152005; CGA-300406 

• N-[[(4-amino-6-methyl-1,3,5-triazin-2-yl)-amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenefulfonamide; desmethoxyamino prosulfuron; desmethoxyamino CGA-152005; 

CGA-325025 

• N-[[[[[[[[2-(3,3,3-trifluoropropyl)phenyl]sulfonyl]amino]carbonyl]amino]-

carbonyl]amino]carbonyl]acetamide; Polyimide Acetate; CGA-325030 

• N-[[[[(aminocarbonyl)amino]carbonyl]amino]carbonyl-2-(3,3,3-trifluoropropyl); CGA325028; phenyl ring with sulfonulurea bridge to open triazine chain 

• N-[[aminocarbonyl)amino]carbonyl]-2-(3,3,3-trifluoropropyl); CGA-325026; phenyl ring 

with sulfonylurea bridge to fragment of triazine 

• N-(aminocarbonyl)-2-(3,3,3-trifluoropropyl); CGA-325027 

• N-[[[4-hydroxymethoxymethyl)-6-methoxy-1,3,5-triazin-2-yl)amino]carbonyl]-2-(3,3,3-

trifluoropropyl); CGA-273437 

• N-[[aminocarbonyl)amino]carbonyl]-N-acetyl-2-(3,3,3-trifluoropropyl); NANC-CGA159902 

Chemical structures of these degradation products are shown in Appendix A3, along with details 

on the maximum amounts observed in laboratory fate studies. 

Two major types of degradates can be formed from prosulfuron: those in which the sulfonylurea 

bridge cleaves, producing degradates containing a single ring and those in which the sulfonylurea 

bridge remains intact. The latter type comprises degradates bearing both the phenyl and the 

triazine ring and degradates in which the triazine ring opens to form aminocarbonyl chains of 

variable length. 

 The major bridge-cleavage degradates are CGA-159902 and CGA-150829. The latter is a 

common degradate with triasulfuron and can produce further degradation products such as 

G28533. The degradates CGA-159902 and CGA-150829 have been identified in all laboratory 

and field studies (except hydrolysis and photolysis at pH 7 and 9). The bridge intact CGA300406 have been identified in water and soil, including field studies as well as CGC-325025. It 

appears that once these degradates form then the sulfonylurea bridge cleaves afterwards. 

Opening of the triazine ring was evident in the hydrolysis and photolysis studies at pH 5, in 

which a degradate consistent with a “polyimide acetate” group was identified (CGA325030).Other triazine-open degradates with variable lengths of aminocarbonyl chains have been 

identified, primarily in soil and sediment; CGA-325026 and CGA-325027. The degradate 

tentatively identified as “NANC-CGA-159902” in the aquatic metabolism studies has also been 

detected in the lysimeter. 

Monitoring Data 

There are only limited monitoring data on prosulfuron, available in a series of publications from 

the U.S. Geological Survey (Battaglin et al., 2000, 2001; Steinheimer et al., 2000). These 

publications report that prosulfuron was detected in samples from several Midwestern streams, at 
14 

a maximum concentration of 0.036 μg/L. They also report an absence of detections in 

groundwater at 25 monitored sites (minimum detection limit for the samples was 0.01 μg/L). 

The following databases and sources were searched for monitoring information on prosulfuron 

on January 15, 2012: 

• The United States Environmental Protection Agency (USEPA) STORET Database 

(http://www.epa.gov/storet/dbtop.html) 

• The United States Geological Survey (USGS) National Water-Quality Assessment 

(NAWQA) Program Data Warehouse 

(http://infotrek.er.usgs.gov/traverse/f?p=NAWQA:HOME:1405517206944567) 

• The USGS National Stream Quality Accounting Network (NASQAN) program 

(http://water.usgs.gov/nasqan/) 

• Sampling for Pesticides Residues in California Well Water Cumulative Report; EEH03-

08; December 2003 (http://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/eh0308.pdf) 

• California Department of Pesticide Regulation (DPR) Surface Water Database 

(http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm) 

No monitoring data are available as none of the databases reported looking for prosulfuron. 

4. Receptors 

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

assessment for prosulfuron will rely on a surrogate species approach. Toxicological data 

generated from surrogate test species, which are intended to be representative of broad groups of 

organisms, are used to extrapolate potential effects on a variety of species (receptors) within 

these groups. Categories of organisms evaluated include: fish, arthropods (insects, crustaceans), 

mollusks, birds, mammals, aquatic vascular and nonvascular plants, and terrestrial plants. 

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

studies available in the open literature, will be used to evaluate the potential direct and indirect 

effects of prosulfuron on aquatic and terrestrial receptors. This includes toxicity of the technical 

grade active ingredient, degradates, and formulated products (e.g. “six-pack” acute toxicity 

studies). Open literature studies are identified using EPA’s publically available ECOTOX 

database2

, which employs a literature search engine for locating chemical toxicity data for 

aquatic life, terrestrial plants, and wildlife. The evaluation of both data sources may also provide 

insight into the direct and indirect effects of prosulfuron usage on biotic communities from loss 

of sensitive species and from changes in community structure or function. 

The most sensitive endpoint for each group of organisms is used in risk assessment. 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. A brief summary of the aquatic and terrestrial toxicity data available for prosulfuron is 

provided in Sections 4.1 and 4.2, respectively. A more complete summary of the available data 

is presented in Appendix B. In addition, a summary of ecological incidents associated with 

 

2

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15 

prosulfuron and a description of ecosystems potentially at risk are provided in Sections 4.3 and 

4.4, respectively. Information on degradate toxicity is discussed in the proposed analysis section 

(Section 7.1). 

Toxicity to fish and aquatic invertebrates is categorized using the system shown in Table 5 (US 

EPA, 2004). Toxicity to terrestrial fauna (birds and mammals) is categorized using the system 

shown in Table 6. Toxicity categories for plants have not been defined. 

Table 5. Categories of Acute Toxicity for Aquatic Animals 

LC50 (m) Toxicity Category 

< 0.1 Very highly toxic 

> 0.1 - 1 Highly toxic 

> 1 - 10 Moderately toxic 

> 10 - 100 Slightly toxic 

> 100 Practically nontoxic 

Table 6. Categories of Acute Toxicity for Terrestrial Animals 

LD50 (mg/kg) LC50 (ppm) Toxicity Category 

<10 <50 Very highly toxic 

10-50 50-500 Highly toxic 

51-500 501 - 1000 Moderately toxic 

501-2000 1001 - 5000 Slightly toxic 

>2000 >5000 Practically nontoxic 

4.1. Effects to Aquatic Organisms 

The most sensitive aquatic toxicity endpoints for each group of organisms (e.g., fish, aquatic 

plants, etc.) from registrant-submitted studies are provided in Table 7. These endpoints will be 

used in quantitative risk assessment of prosulfuron. No aquatic toxicity studies were available in 

ECOTOX as of January 18, 2012 besides those submitted by the registrant. A more detailed 

summary of all aquatic toxicity studies can be found in Appendix B. 

Prosulfuron is practically non-toxic to aquatic animals based on acute limit tests with the 

technical grade active ingredient (TGAI). All acute toxicity endpoint values (i.e., LC50/EC50) 

were estimated to be greater than the limit concentration since less than 50% of prosulfurontreated animals died in each test. For chronic toxicity tests, no statistically significant effects 

were observed for growth, survival, or reproduction endpoints at any treatment level in either of 

the aquatic animals tested, i.e., fathead minnows (Pimephales promelas) and daphnids (Daphnia 

magna). Therefore, the NOAEC for chronic tests are equal to the highest concentration tested. 

The most sensitive aquatic plant toxicity values are also presented in Table 7. In several studies 

with aquatic nonvascular plants, less than 50% inhibition in cell growth occurred at the limit 

concentration or highest concentration tested, resulting in non-definitive (“greater than”) EC50
16 

values. Conversely, definitive toxicity values for the nonvascular freshwater green algae 

(Pseudokirchneriella subcapitata) and the vascular freshwater duckweed (Lemna gibba) are 

several orders of magnitude lower (more toxic) compared to aquatic animals. 

Table 7. Most Sensitive Aquatic Toxicity Endpoints for Prosulfuron 

Species Measured 

Effect Duration Endpoint Toxicity Value μg ai/L 

Test 

Substance 

% ai 

MRID 

(Study 

Classification) 

Freshwater Fish 

Lepomis 

macrochirus 

(Bluegill sunifsh) 

Mortality 96 hours LC50

>155,000*†

(Practically 

non-toxic)

99.1% 426852-09 

(Acceptable) 

Pimephales 

promelas 

(Fathead Minnow) 

Growth, 

Survival, 

Hatchability 

37 days NOAEC 149,000 99.1% 429497-07 

(Acceptable) 

Freshwater Crustaceans 

Daphnia magna 

(Water flea) 

Immobility 48 hours EC50

>120,000*†

(Practically 

non-toxic) 

99.1 426852-11 

(Acceptable) 

Growth, 

Survival, 

Reproduction

21 days NOAEC 148,000 99.1 429497-08 

(Acceptable) 

Estuarine/Marine Fish 

Cyprinodon 

variegatus 

(Sheepshead 

minnow) 

Mortality 96 hours LC50

>155,000*†

(Practically 

non-toxic) 

99.1% 429497-06 

(Acceptable) 

Estuarine/Marine Crustaceans 

Americamysis bahia 

(Mysid shrimp) Mortality 96 hours LC50

>150,000*†

(Practically 

non-toxic) 

99.1% 432126-01 

(Supplemental) 

Estuarine/Marine Mollusks 

Crassostrea 

virginica 

(Eastern oyster) 

Shell 

deposition 96 hours EC50

>125,000*†

(Practically 

non-toxic) 

99.1% 432126-02 

(Acceptable) 

Aquatic Plants 

Lemna gibba 

(duckweed) Frond number 14 days EC50 1.22 98.7% 429497-13 

NOAEC 0.83 (Acceptable) 

Pseudokirchneriella 

subcapitata 

(green algae) 

Tier II Study

Cell density 5 days 

EC50 10.6 

98.7% 429497-14 

NOAEC 2.78 (Acceptable) 

* Non-definitive study endpoint; cannot be used for risk estimation. 

†

 Single concentration limit test. 

4.2. Effects to Terrestrial Organisms 

The most sensitive toxicity endpoint values associated with prosulfuron exposure to terrestrial 

organisms are shown in Table 8. These endpoints will be used in quantitative risk assessment of 

prosulfuron. More detailed descriptions of these studies are provided in Appendix B. No toxicity 
17 

studies with terrestrial organisms were available in ECOTOX as of January 18, 2012 besides 

those submitted by the registrant. 

In general, available ecotoxicity data indicate that prosulfuron exhibits low toxicity to mammals, 

birds, and honeybees. Prosulfuron is characterized as being slightly toxic to birds on an acute 

oral exposure basis, and is practically non-toxic to mammals on an acute oral exposure basis and 

to birds on a subacute dietary exposure basis. Prosulfuron is also practically non-toxic to young 

adult honey bees (Apis mellifera) on an acute contact exposure basis. A chronic study in mallard 

ducks revealed decreased hatch success in birds treated with prosulfuron as compared to 

controls. Mammal chronic feeding and reproductive toxicity studies resulted in significant 

decreases in body weight or body weight gain in parental rats and their offspring. 

Prosulfuron is highly toxic to terrestrial plants, which is expected given its use as an herbicide. It 

should be noted that all plant studies were carried out with prosulfuron technical. Therefore, 

effects due to other ingredients used in formulations are unknown. Terrestrial plant toxicity 

endpoints from studies with the TGAI will not be used in quantitative risk assessment, but may 

be used for risk characterization. Appendix B contains descriptions of terrestrial plant toxicity 

studies and endpoints. 

Table 8. Most Sensitive Terrestrial Toxicity Endpoints for Prosulfuron 

Species Measured effect Endpoint Test 

Duration

Toxicity Value 

(Acute Toxicity 

Category) 

Test 

Substance 

% ai 

MRID 

(Study 

Classification)

Birds

Anas 

platyrhynchos 

(mallard duck) 

Mortality LD50 14 days 1094 mg ai/kg-bw 

(Slightly toxic) 99.2% 426852-05 (Acceptable) 

Mortality LC50 8 days 

>5000 mg ai/kg-diet* 

(Practically nontoxic) 99.1% 426852-07 

(Acceptable) 

Hatching success NOAEC 25 weeks 28 mg ai/kg-diet 99.2% 429497-02 

(Acceptable) 

Mammals

Rattus 

norvegicus 

(laboratory rat) 

Mortality LD50 14-days 546 mg/kg-bw

(females) 99.1% 

426852-15 

(Acceptable: 

Reviewed by 

HED) 

Body weight, 

body weight gain 

(subchronic 

feeding study) 

NOAEL 3 months 50 mg/kg-diet (males) 

(3.1 mg/kg/day) 96% 

426852-32 

(Acceptable: 

Reviewed by 

HED) 

Terrestrial Arthropods

Apis mellifera

(Honeybee) Mortality LD50 48 hours >100 μg ai/bee 99.1% 426852-12 

(Acceptable) 

* Non-definitive study endpoint; cannot be used for risk estimation. 

4.3. Incident Database Review 

A search of the EIIS (Environmental Incident Information System) database for ecological 

incidents (run on January 25, 2012) identified 78 incidents that may involve exposures to 

prosulfuron. Incidents included in EIIS are defined by a certainty index associated with the 
18 

likelihood that the pesticide application described resulted in the observed incident. The 

certainty index defines incidents as unrelated, unlikely, possible, probable and highly probable. 

One note of uncertainty associated with this data base is the nature of reporting of incidents. 

Many more incidents may have occurred due to prosulfuron exposures but may not have been 

reported due to various factors, such as a lack of reporting, or a lack of witnessing of effects. 

All 78 incidents identified by EIIS report plant damage. Sixty-five of these incidents were listed 

as a potential result of direct treatment of prosulfuron to specific crops or agricultural areas. All 

except one of the 78 incidents are classified as “probable” in terms of identification of 

prosulfuron as the causative agent. In 27 cases, incidents are known to have occurred after a 

registered use of the pesticide, while in six other cases, products containing prosulfuron were 

misused or accidentally misapplied. 

A search of OPP’s aggregate incident report database revealed a total of 37 minor plant incidents 

between 1998 and 2009 that were attributed to prosulfuron (Appendix C). 

The Avian Monitoring Information System (AIMS)3

, which is maintained by the American Bird 

Conservancy, was also searched on January 25, 2012, and revealed no incidents to birds 

associated with prosulfuron. 

During the risk assessment associated with Registration Review of prosulfuron, these databases 

will be checked again and any additional incidents will be evaluated to determine if they 

represent current use patterns of prosulfuron. 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). It should be noted that incident 

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

damage. Sublethal effects in organisms such as abnormal behavior, reduced growth and/or 

impaired reproduction are rarely reported, except for phytotoxic effects in terrestrial plants. 

4.4. Ecosystems Potentially At Risk 

The ecosystems at risk are often extensive in scope, and as a result it may not be possible to 

identify specific ecosystems during the development of a baseline risk assessment. However, in 

general terms, terrestrial ecosystems potentially at risk could include the treated field and areas 

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

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

grasslands, woodlands, riparian habitats and other uncultivated areas. 

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

treated field and might 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. 

5. Assessment Endpoints 

 

3

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19 

Assessment endpoints are defined as "explicit expressions of the actual environmental value that 

is to be protected." Selection of the assessment endpoints is based on valued entities (e.g., fish, 

birds), the ecosystems potentially at risk (e.g., water bodies, riparian vegetation, and upland 

habitats), the migration pathways of prosulfuron (e.g., runoff, drift, etc.), and the routes by which 

ecological receptors are exposed to prosulfuron (e.g., direct contact, etc.). Assessment endpoints 

for prosulfuron include direct adverse effects on the survival, reproduction, and growth of the 

receptors, as well as indirect effects, such as reduction of the prey base or modification of 

habitat. Each assessment endpoint requires one or more "measures of ecological effect," defined 

as changes in the attributes of an assessment endpoint or changes in a surrogate entity or attribute 

in response to exposure to a pesticide. Specific measures of ecological effect are generally 

evaluated based on acute and chronic toxicity information from registrant-submitted guideline 

tests that are performed on a limited number of organisms. Additional ecological effects data 

from the open literature will also be considered. 

6. Conceptual Model 

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

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

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

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

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

The conceptual model for prosulfuron provides a written description and visual representation of 

the predicted relationships between prosulfuron and degradates, potential routes of exposure, and 

the predicted effects for the assessment endpoint. A conceptual model consists of two major 

components: risk hypothesis and a conceptual diagram (USEPA, 1998). 

6.1. Risk Hypothesis 

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

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

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

assessment: 

Given the uses of prosulfuron and its environmental fate properties, there is a likelihood of 

exposure to non-target terrestrial and/or aquatic organisms. When used in accordance with the 

label, prosulfuron and its degradates may result in adverse effects upon the survival, growth, 

and reproduction of non-target terrestrial and/or aquatic organisms. These non-target 

organisms may include Federally-listed threatened and endangered species. 

Prosulfuron is both persistent and mobile in soil and may pose a risk to terrestrial plants near 

the site of application. Moreover, prosulfuron is known to be toxic to non-target terrestrial 

plants based on available data. 
20 

Prosulfuron and its degradates are mobile and may occur in aquatic systems. In addition, 

prosulfuron is stable in aquatic environments (except at low pHs). Therefore prosulfuron and its 

degradates may pose a risk to aquatic organisms. Toxicity studies suggest that this risk may be 

greatest to aquatic plants. 

The available data do not suggest that prosulfuron is particularly toxic to aquatic animals. 

However, the chemical's persistence and effect on aquatic and terrestrial plants could affect 

primary productivity and, in turn, have secondary effects on the entire animal community. 

6.2. Conceptual Diagram 

The conceptual model depicts the potential pathways for ecological risk associated with the use 

of prosulfuron for the control of weeds in corn, popcorn, grain sorghum (milo), wheat, barley, 

rye, oats, triticale, proso millet, and small grains. The conceptual model provides an overview of 

the expected exposure routes for terrestrial and aquatic organisms. 

The potential exposure pathways and effects of prosulfuron on aquatic environments are depicted 

in Figure 1 and for terrestrial environments in Figure 2. Figure 3 depicts potential exposure 

from drinking water and inhalation to terrestrial vertebrates and invertebrates. Stressors of 

concern for aquatic and terrestrial organisms include prosulfuron and the following degradates: 

CGA-159902, CGA-150829, CGA-300406, CGA-325025, CGA-325030, CGA-325028, 

CGA-325026, CGA-325027, CGA-188838, NANC-CGA-159902, and G-28533. Solid arrows 

depict the most likely routes of exposure and effects; dashed lines depict potential routes of 

exposure that are not considered likely. 

Prosulfuron will enter the environment via direct application to terrestrial environments when it 

is applied to field crops. It may move off site via spray drift, runoff, and leaching. Volatilization 

from moist soils is not expected to be a major route of exposure because the vapor pressure of 

prosulfuron is less than 10-8 Torr. Additionally, the Screening Tool for Inhalation Risk (STIR)4

 

version 1.0 (run January 26, 2012) indicates that exposure via inhalation is not likely to be a risk 

concern for birds and mammals (see Section 7.2 and Appendix D for further discussion). These 

results combined with the estimated atmospheric half-life of less than two days indicate that long 

range transport in the vapor phase is not an exposure pathway of concern. 

The low Kow indicates that prosulfuron is not likely to bioconcentrate or bioaccumulate in 

aquatic or terrestrial organisms. The Koc values range from 15.2 to 41.3 L/kg, and Kd values 

range from 0.074 to 0.293 L/kg, indicating that prosulfuron is mobile. Because it is also 

persistent, prosulfuron has the potential to leach to groundwater and to reach surface water by 

runoff and spray drift. 

The Screening Imbibition Program (SIP)6 version 1.0 (run January 26, 2012) indicates that 

prosulfuron has the potential to be present in drinking water at high enough concentrations to 

result in acute and chronic risks of concern for both birds and mammals (Appendix E for results 

output). This is a highly conservative evaluation since estimated drinking water exposure is 

unrelated to applications rate; rather, SIP assumes that concentrations in drinking water could be 

 

4

 http://www.epa.gov/oppefed1/models/terrestrial/index.htm 
21 

at the level of solubility. 

Finally, surface and shallow ground water contaminated with prosulfuron have the potential to be 

used as irrigation water, which may result in exposure to terrestrial plants. Prosulfuron is toxic 

to terrestrial plants and there are also incident data substantiating potential for risks to terrestrial 

plants.

Figure 1. Conceptual model depicting stressors, exposure pathways, and potential effects 

to aquatic organisms from the use of prosulfuron on crops. 
22 

Figure 2. Conceptual model depicting stressors, generic exposure pathways, and potential 

effects to terrestrial organisms (terrestrial plants, terrestrial invertebrates, and dietary 

routes of exposure for terrestrial vertebrates) from the use of prosulfuron on various crops. 
23 

Figure 3. Conceptual model depicting stressors, drinking water and inhalation exposure 

pathways, and potential effects to terrestrial animals from the use of prosulfuron on crops. 

7. Analysis Plan 

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

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

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

concentration to effects concentration) approach. Although risk is often defined as the likelihood 

and magnitude of adverse ecological effects, the risk quotient-based approach does not provide a 

quantitative estimate of likelihood and/or magnitude of an adverse effect. However, as outlined 

in the Overview Document (USEPA, 2004), the likelihood of effects to individual organisms 

from particular uses of prosulfuron is estimated using the probit dose-response slope and either 

the level of concern (discussed below) or actual calculated risk quotient value. 

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

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

prosulfuron. 
24 

7.1. Identification of Stressors of Concern 

The Health Effects Division (HED) did not identify any degradates of human health concern in 

its latest risk assessment of prosulfuron (USEPA, 2009). In EFED’s upcoming Registration 

Review Ecological Risk Assessment of prosulfuron, all 11 major and minor degradates of 

prosulfuron described in section 3.3 will be considered potential stressors of concern for the 

following reasons (see Appendix A3 for structure, identity, and fate information on 

transformation products). Based on environmental fate data, it is possible that both parent and 

degradates may move to adjacent terrestrial areas or surface waters near the site of application, 

creating the potential for non-target organisms to be exposed. In addition, all degradates retain 

one or more of the major structural properties of the parent (e.g., SU bridge; triazine heterocyclic 

ring structure) and therefore may exhibit similar toxicity to the parent. No new data is currently 

recommended to better understand the potential ecological effects of degradates. Instead, a total 

toxic residues (TTR) approach will be employed during risk assessment, where exposure values 

(i.e., EECs) of parent and degradates will be summed and subsequently compared to toxicity 

endpoints for the parent in order to estimate a cumulative risk values (called “risk quotients”) for 

parent plus degradates. The risk quotient will then be compared to Agency levels of concern 

(LOCs) for the appropriate group of organisms (see Appendix F for LOC values). The specific 

set of degradates that will be used in the TTR approach will depend on the organismal group 

being examined as outlined below. 

No toxicity data are available in EPA databases or in the open literature for any of the 

prosulfuron degradates identified in environmental fate studies. Therefore, information on 

degradate molecular structure as well as quantitative structure-activity relationships (QSAR) 

were used to determine whether additional toxicity data are needed for transformation products 

to address critical uncertainties. 

Terrestrial Plants 

 In the absence of laboratory toxicity data, any degradate containing the intact SU bridge (i.e., 

-NH-CO-NH-SO2-) would ideally be included as part of a TTR approach for terrestrial plants. 

This includes the following degradates: CGA-300406, CGA-325025, CGA-325026, 

CGA-325028, CGA-325030, NANC-CGA-159902, CGA-273437. Degradates not containing the 

SU bridge are assumed to be non-toxic and would not be included in risk estimation. Although 

several triazine-type products do result from breakdown of the parent, these degradates do not 

have the two n-alkyl groups that are characteristic of herbicidally active triazine compounds 

(e.g., atrazine). Under the TTR scenario laid out, combined EECs would be calculated for parent 

and SU degradates and then compared to terrestrial plant toxicity endpoints in order to calculate 

risk quotients. However, EFED does not currently have a method for calculating terrestrial EECs 

for degradates. Therefore, the TTR approach for terrestrial plants will only be employed if 

methods become available prior to the upcoming Registration Review risk assessment. 

 

Aquatic Plants 

QSAR analysis was conducted in ECOSAR (version 1.00)5

 and indicates that degradates 

 

5

 http://www.epa.gov/oppt/newchems/tools/21ecosar.htm 
25 

retaining the SU bridge may be toxic to green algae (Table 9). In the absence of additional 

toxicity data for degradates, transformation products identified as SUs will be assumed to be as 

toxic as the parent to both vascular and nonvascular aquatic plants. Thus, a TTR approach will 

be applied in a similar manner as described for terrestrial plants. It should be noted that there is 

uncertainty associated with structure-activity estimates for green algae since calculations in 

ECOSAR were based on empirical EC50 values from only three SU chemicals6. However, 

empirical and predicted EC50 values for the parent compound are similar (0.01 and 0.05 mg ai/L, 

respectively), providing some support for using QSAR to predict toxicity to aquatic plants. 

Degradates not falling into the SU category (CGA-159902; CGA-325027; G-28533; CGA18838) will not be included in risk estimation of aquatic plants. European Union (EU) data 

available through the FOOTPRINT database7

 on toxicity of CGA-159902 (does not retain SU 

bridge) to green algae suggests that it is several orders of magnitude less toxic (EC50 86 mg/L) 

than the parent. 

Aquatic Animals 

For aquatic animals (i.e., fish, daphnids), QSAR appears to overestimate the toxicity of 

prosulfuron by several orders of magnitude relative to empirical data regardless of compound 

class (Table 9). Consequently, toxicity predictions from ECOSAR may not be reliable for 

prioritizing degradates. Given this uncertainty, a TTR approach will be applied to aquatic 

animals across all prosulfuron degradates unless additional toxicity data becomes available. The 

use of a TTR approach across degradates for aquatic animals is justified for several reasons. 

First, all 11 degradates under consideration fall into at least one of the three chemical 

classifications of the parent (i.e., triazines, amides, sulfonyl ureas). Second, ECOSAR 

predictions do not suggest that any degradate is markedly more toxic than the parent. Finally, 

empirical toxicity data from the EU FOOTPRINT database7 for transformation products CGA159902, CGA-150829, CGA-300406, and CGA-349707 report fish and/or daphnid EC50 values 

ranging from 16 to 200 mg/L, which are all within one order of magnitude of empirical endpoint 

values from the parent compound. There is some uncertainty regarding acute toxicity of 

degradate CGA-150829 to daphnids (EC50 16 mg/L) based on EU data, which is substantially 

lower than parent toxicity for the same species (EC50 >120 mg/L); however, since the peak water 

column EEC for CGA-150829 is likely to be more than 20 times lower than 16 mg/L, it is 

unlikely that additional aquatic animal data for CGA-150829 would trigger risks of concern (i.e.,

exceed aquatic animals listed species LOC of 0.05). 

Table 9. ECOSAR Quantitative Structure-Activity Relationship (QSAR) Toxicity 

Predictions for Prosulfuron and Degradates 

Compound 

(compounds class 

used by ECOSAR) 

Estimated Toxicity Endpoint (mg/L) 

96-hr FW fish 

EC50/LC50

48-hr 

Daphnid 

LC50

96-hr EC50

Green Algae 

Fish Chronic 

Value 

Daphnid 

Chronic 

Value 

EMPIRICAL TOXICITY DATA 

Prosulfuron Parent 

(measured) >155 >120 0.0106 149 148 

 

6

 ECOSAR v1.00 User Guide provides a list of all data points used to generate QSAR estimates 

7

 EU data has not been evaluated by EPA and is only used here for degradate prioritization. 

http://sitem.herts.ac.uk/aeru/footprint/en/ 
26 

Compound 

(compounds class 

used by ECOSAR) 

Estimated Toxicity Endpoint (mg/L) 

96-hr FW fish 

EC50/LC50

48-hr 

Daphnid 

LC50

96-hr EC50

Green Algae 

Fish Chronic 

Value 

Daphnid 

Chronic 

Value 

ECOSAR TOXICITY PREDICTIONS 

Prosulfuron (Parent) 

Triazines 2.3 4.6 3.8 1.4 0.97 

Amides 3.1 3.0 0.34 0.019 0.040 

Sulfonyl Ureas N/A 7.9 0.047 N/A 0.84 

CGA-159902 

Amides 18 12 0.46 0.11 0.15 

CGA-150829 

Anilines: Aromatic 

Amines 49 1.9 7.7 0.21 0.036 

Triazines 474 171 31 44 12 

CGA-300406 

Phenols 26 11 48 2.2 (30-days) 

0.012 (60days) 2.1 

Triazines 42 39 16 11 5.0 

Amides 21 14 0.64 0.12 0.18 

Sulfonyl Ureas N/A 42 0.045 N/A 4.2 

Phenol Amines 9.9 1.9 4.5 0.33 0.29 

CGA-325025 

Anilines: Aromatic 

Amines 31 3.0 17 0.074 0.039 

Triazines 40 37 15 10 4.8 

Amides 20 13 0.63 0.12 0.18 

Sulfonyl Ureas N/A 40 0.045 N/A 4.1 

CGA-325028 

Imides 13 16 2.1 1.2 1.5 

Amides 5.5 4.7 0.39 0.033 0.062 

Sulfonyl Ureas N/A 13 0.043 N/A 1.3 

CGA-325026 

Imides 96 105 5.1 9.4 8.5 

Amides 42 24 0.74 0.25 0.32 

Sulfonyl Ureas N/A 76 0.038 N/A 7.4 

CGA-325027 

Amides 49 26 0.71 0.29 0.35 

G-28533 

Triazines 1235 334 48 83 20 

Phenols 54 383 1.4 20 153 

NANC-CGA-159902 

Imides 69 78 4.6 6.8 6.5 

Amides 30 19 0.69 0.18 0.25 

Sulfonyl Ureas N/A 58 0.041 N/A 5.7 

CGA-18838 

Anilines: Aromatic 

Amines 157 2.7 8.8 1.1 0.072 

Phenols 388 69 376 16 (30day) 

0.004 (60-day) 13 

Triazines 8264 1331 122 317 59 

Phenol Amines 24 1.4 10 2.2 1.1 

CGA-325030 

Imides 7.4 9.3 1.7 0.71 0.94 
27 

Compound 

(compounds class 

used by ECOSAR) 

Estimated Toxicity Endpoint (mg/L) 

96-hr FW fish 

EC50/LC50

48-hr 

Daphnid 

LC50

96-hr EC50

Green Algae 

Fish Chronic 

Value 

Daphnid 

Chronic 

Value 

Amides 3.2 3.1 0.34 0.019 0.040 

Sulfonyl Ureas N/A 8.0 0.047 N/A 0.85 

CGA-273437 

Triazines 142 96 30 26 10 

Benzyl Alcohols 98 22 N/A 6.5 7.2 

Amides 47 27 0.90 0.28 0.36 

Sulfonyl Ureas N/A 86 0.049 N/A 8.5 

7.2. Measures of Exposure 

In order to estimate risks of prosulfuron exposure in aquatic and terrestrial environments, all 

exposure modeling and resulting risk conclusions will be based on maximum application rates 

and methods cited in Table 1 and will be estimated for each use of prosulfuron. Measures of 

exposure are based on aquatic and terrestrial models that predict estimated environmental 

concentrations (EECs) of prosulfuron. 

Concentrations of prosulfuron in surface waters (EECs) will be estimated using PRZM (Pesticide 

Root Zone Model version 3.12.2; May 12, 2005) and EXAMS (Exposure Analysis Modeling 

System version 2.98.04.06; April 25, 2005). The PRZM model simulates pesticide movement 

from and transformation on an agricultural field following application. The EXAMS model 

simulates resulting concentrations in a receiving water body. The PRZM and EXAMS models 

and their user manuals may be downloaded from the EPA Water Models web-page (US EPA, 

2006). Percent Cropped Area (PCA) adjustment factors are used to account for the maximum 

fractional area within a watershed that may be planted with a modeled crop, and are used to 

modify drinking water concentrations predicted by PRZM and EXAMS (US EPA, 2010). 

Concentrations of prosulfuron in ground water will be estimated using EFED's Tier I aquatic 

model SCIGROW (Screening Concentration In Ground Water, version 2.3; 8/8/2003). 

SCIGROW is a regression model used as a screening tool to estimate pesticide concentrations 

found in ground water used as drinking water. The output of SCIGROW represents 

concentrations that might be expected in shallow unconfined aquifers under sandy soils, and 

therefore represents ground water that is most potentially vulnerable to pesticide contamination. 

The SCI-GROW model and user’s manual may also be downloaded from the EPA Water Models 

web-page (US EPA, 2006). 

In addition to modeling estimates, available monitoring data will be evaluated. Monitoring data 

will include those collected/reported by states as well as other federal departments/agencies (e.g., 

USGS National Water Quality Assessment; http://water.usgs.gov/nawqa). 

A downstream dilution model (under development) may be used to identify areas downstream 

from a use area that may have EECs high enough to result in a risk concern. This analysis will 

be used to define the potential area of effects for endangered species. 
28 

Exposure estimates for terrestrial animals assumed to be in the target area or in an area exposed 

to spray drift are derived using the T-REX model (version 1.4.1, 10/09/2008)4

. This model 

incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), which is based on a 

large set of field residue data. The upper-limit values from the nomograph represent the upper 

bound of residue values from actual field measurements (Hoerger and Kenaga, 1972). The 

Fletcher et al. (1994) modifications to the Kenaga nomograph are based on measured field 

residues from 249 published research papers, including information on 118 species of plants, 121 

pesticides, and 17 chemical classes (Fletcher et al., 1994). Based on these data, T-REX assumes 

a 35-day foliar dissipation half-life in the absence of other data. 

EECs for terrestrial plants inhabiting dry and wetland areas are derived using the program 

TERRPLANT (version 1.2.2, 12/26/2006)4. This model uses estimates of pesticides in runoff 

and spray drift to calculate EECs. EECs are based upon solubility, application rate and 

minimum incorporation depth. AgDRIFT may also be used to assess exposure to spray drift. 

In order to determine if inhalation is a potential pathway of concern for terrestrial organisms, the 

Screening Tool for Inhalation Risk (STIR v.1.0) was used to calculate an upper-bound estimate 

of exposure using prosulfuron’s vapor pressure and molecular weight for vapor phase exposure 

as well as the maximum application rate and method of application for spray drift. STIR 

incorporates results from several toxicity studies including acute oral (MRID 426852-15; LD50

546 mg/kg-bw) and inhalation (MRID 426852-17; LC50 5.5 mg/L) rat toxicity endpoints 

obtained from the "six-pack" of core studies submitted to OPP’s Registration Division for 

technical and formulated products of a pesticide as well as the most sensitive acute oral avian 

toxicity endpoint. Based on the results of the STIR model, inhalation exposure alone was not 

determined to be a potential pathway of concern for avian or mammalian species on an acute 

exposure basis (STIR program inputs/outputs for prosulfuron are provided in Appendix D). The 

analysis of the inhalation route in STIR does not consider that aggregation with other exposure 

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

potential for effects to non-target animals. However, the Agency does consider the relative 

importance of other routes of exposure in situations where data indicate that pesticide exposures 

through other routes may be potentially significant contributors to wildlife risk (USEPA, 2004). 

The risk assessment will discuss the impact of consideration of other routes of exposure that 

have been identified as potentially important and the degree of certainty associated with 

screening-level risk assessment conclusions. Detailed information about STIR v.1.0, as well as 

the tool, can be found on the EPA's website.8

The Screening Imbibition Program (SIP v.1.0) was used to calculate an upper-bound estimate of 

exposure based on the solubility of prosulfuron as well as the most sensitive acute and chronic 

avian and mammalian toxicity endpoints (see Table 8). Drinking water exposure was determined 

to be a potential pathway of concern for both avian and mammalian species on an acute and 

chronic exposure basis (SIP program inputs/outputs for prosulfuron are provided in Appendix 

E). As stated previously, this is a highly conservative evaluation since estimated drinking water 

exposure is unrelated to applications rate; rather, SIP assumes that concentrations in drinking 

water could be at the level of solubility. This pathway will be explored further with the 
29 

development of SIP v.2.0 in the risk assessment for prosulfuron. Detailed information about the 

SIP v.1.0 as well as the tool can be found on EPA's website.8

Two spray drift models, AgDISP and AgDRIFT, are used to assess exposures of aquatic and 

terrestrial organisms to prosulfuron deposited in terrestrial and aquatic habitats by spray drift. 

AgDrift (version 2.01; dated 5/24/2001) is the model most commonly used to simulate spray 

drift into terrestrial and aquatic environments. AgDISP (version 8.13; dated 12/14/2004) (Teske 

and Curbishley, 2003) is used when a parameter needs to be modeled that is not available in 

AgDRIFT. Spray drift analysis will be an important part of the analysis in defining the potential 

area of effects for endangered species. 

7.3. Measures of Effects 

Ecological effects data are used as measures of direct and indirect effects to biological receptors. 

Effects data are obtained from registrant-submitted studies or from literature studies identified by 

the ECOTOX database. The acute measures of effect used for animals in this 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 kil1 50% 

of the test organisms. EC stands for "Effect Concentration" and the EC50 is the concentration of a 

chemical that is estimated to produce a specific effect in 50% of the test organisms. Endpoints 

for chronic measures of exposure for listed and non-listed animals are the NOAEL/NOAEC. 

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-Effect-Concentration") is the highest test concentration at 

which none of the observed effects were statistical1y different from the control. 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. 

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

studies wil1 be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

lethargy and changes in coloration). However, quantitative assessments of risks are limited to 

those endpoints that can be directly linked to the Agency's assessment endpoints of impaired 

survival, growth and reproduction. 

In the absence of taxa-specific data, the assessment of risk for direct effects to non-target 

organisms makes the assumption that toxicity of prosulfuron to birds is similar to terrestrialphase amphibians and reptiles. The same assumption is made for fish and aquatic-phase 

amphibians. In the absence of data for either acute or chronic effects, the conservative 

assumption wil1 be to presume that prosulfuron is toxic. 

 

8

 http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial 
30 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterizations to 

determine the potential ecological risk from the registered uses of prosulfuron and the likelihood 

of direct and indirect effects to non-target organisms in aquatic and terrestrial habitats. The 

exposure and toxicity (effects) data are integrated in order to evaluate the risks of adverse 

ecological effects on non-target species. For the assessment of prosulfuron, the risk quotient 

(RQ) method is used to compare exposure and measured toxicity values. EECs are divided by 

acute and chronic toxicity values. The resulting RQs are then compared to the Agency's Levels 

of Concern (LOCs) (USEPA 2004) (Appendix F). These criteria are used to indicate when 

prosulfuron use, as directed on the labels, has the potential to cause adverse direct or indirect 

effects to non-target organisms. In addition, incident data from the EIIS will be considered as 

part of the risk characterization. 

7.5. Deterministic and Probabilistic Assessment Methods 

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

(RQ) based approach described in the risk assessment. Depending on the extent of refinement 

needed by the risk manager, risk estimates may be further refined using probabilistic tools that 

the Agency has developed. These tools have been reviewed by FIFRA Scientific Advisory 

Panels9

 and have been deemed as an appropriate means of refining assessments where 

deterministic approaches have identified risks. Newer tools may be available to assess the routes 

of exposure and will be applied as appropriate in Registration Review. 

7.6. Endocrine Disruptor Screening Program 

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its reregistration decision, EPA reviewed these data and selected 

the most sensitive endpoints for relevant risk assessment scenarios from the existing hazard 

database. However, as required by FFDCA section 408(p), Prosulfuron is subject to the 

endocrine screening part of the Endocrine Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

 

9

 http://vvww.epa.gov/scipoly/sap/index.htm 
31 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. Prosulfuron is 

not among the group of 58 pesticide active ingredients on the initial list to be screened under the 

EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data callins, requiring the submission of EDSP screening assays for Prosulfuron. For further information 

on the status of the EDSP, the policies and procedures, the list of 67 chemicals, future lists, the 

test guidelines and the Tier 1 screening battery, please visit our website: 

http://www.epa.gov/endo/. 

7.7. Endangered Species Assessment 

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 prosulfuron. 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 area 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 prosulfuron 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 US and its territories is to ensure that the 

initial area of consideration encompasses all areas where prosulfuron 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 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 
32 

critical habitat may be affected or modified via endpoints associated with reduced survival, 

growth, or reproduction. 

7.8. Drinking Water Assessment 

In order to bring the drinking water exposure assessment up to date with current data, models 

and simulation model guidance, a new drinking water assessment will be conducted to support 

future human health dietary risk assessments of prosulfuron. The drinking water exposure 

assessment will be conducted for the maximum labeled use rate in support of the human health 

dietary risk assessment. The drinking water assessment will incorporate model estimates of 

prosulfuron alone in surface water and ground water including any residues that are determined 

to be of toxicological concern (see Section 7.1). Concentrations of prosulfuron in surface water 

(EDWCs) will be estimated using PRZM 3.12.2 (dated May 12, 2005) and EXAMS 2.98.04.06 

(dated April 25, 2005) coupled through the input shell PE 5.0 (US EPA, 2006). An EDWC of 

prosulfuron in ground water will be estimated using SCIGROW 2.3 (dated August 8, 2003). 

8. Preliminary Identification of Data Gaps 

8.1. Environmental Fate 

The studies submitted to fulfill environmental fate data requirements for prosulfuron are fairly 

complete and therefore, additional studies are not necessary at this time. However, there is 

limited environmental fate data on degradates that can potentially impact water sources (CGA159902, CGA-150829, CGA-325030, CGA-188838, G-28533, CGA-325025, CGA-325026, 

CGA-325027, CGA-325028, NANC-CGA-159902, and CGA-300406) due to leaching and/or 

runoff potential. Table 9 summarizes the fate data requirements for prosulfuron. 

 

Table 10. Summary of Submitted Environmental Fate Studies, Study Classifications and 

Data Gaps for Prosulfuron and Its Degradates 

Guideline

MRID 

(part of the 

molecule that 

was 

radiolabeled)

Study 

Classification

Comments on Study 

Classification 

Data 

Gap Comments 

Hydrolysis 

835.2120 

(161-1) 

42685246 

(triazine) Acceptable None 

No 

42685247 

(phenyl) 

Acceptable None 

Aqueous 

Photolysis 

835.2370 

(161-2) 

42685248 

(triazine) Acceptable None 

No 

The proposed 

degradation pathway 

was not reported. 42685249 

(phenyl) Acceptable None 

Soil Photolysis 

835.2410 

43159327 

(phenyl) Acceptable None No None 
33 

Guideline

MRID 

(part of the 

molecule that 

was 

radiolabeled)

Study 

Classification

Comments on Study 

Classification 

Data 

Gap Comments 

(161-3) 43159328 

(triazine) Acceptable None 

Aerobic Soil 

Metabolism 

835.4100 

(162-1) 

42685250 

(triazine) Acceptable None 

No None 

42685251 

(phenyl) Acceptable None 

43387712 

(triazine) Acceptable None 

43387713 

(phenyl) Acceptable None 

Anaerobic Soil 

Metabolism 

835.4200 

(162-2) 

42685252 

(triazine) Acceptable None 

No None 

42685253 

(phenyl) Supplemental 

Deficiencies were found 

in the study. Degradates 

isolated from soil (6.6% 

of the applied 

radioactivity) were not 

identified. In addition, the 

concentration of the 

individual compounds 

isolated using HPLC do 

not sum the concentration 

of total residues in the 

soil extracts determined 

using Liquid Scintillation 

Counting. 

43387714 

(triazine) Acceptable None 

43387715 

(phenyl) Acceptable None 

Aerobic Aquatic 

Metabolism 

835.4300 

(162-4) 

43387718 

(triazine) Acceptable None 

No None 

43387719 

(phenyl) Acceptable None 

Anaerobic 

Aquatic 

Metabolism 

835.4400 

(162-3) 

43387716 

(triazine) Acceptable None 

No None 

43387717 

(phenyl) Acceptable None 

Adsorption/deso

rption batch 

42685257 

(triazine) Acceptable Conducted on parent 

compound No None 
34 

Guideline

MRID 

(part of the 

molecule that 

was 

radiolabeled)

Study 

Classification

Comments on Study 

Classification 

Data 

Gap Comments 

equilibrium 

835.1230 

43159329 

(phenyl) Acceptable Conducted on degradate 

CGA-159902 

43159330 

(phenyl) Supplemental 

Conducted on degradate 

CGA-300406. The 

concentration of CGA300406 used in the test 

solutions (0.25 to 0.99 

μg/mL) had a four-fold 

range. In order for 

Freundlich values to be 

accurately assessed a tenfold of concentrations 

should be tested 

43387720 

(triazine) Acceptable Conducted on degradate 

G-28533 

Aged Column 

Leaching 

835.1240 

(163-1) 

42685255 

(triazine) Acceptable None 

No None 

42685256 

(phenyl) Acceptable None 

Soil Column 

Leaching 

(unaged) 

42685257 

42685254 

(triazine) Acceptable None No None 

Terrestrial; Field 

Dissipation 

835.6200 

Terrestrial; Field 

Dissipation 

835.6200 

43159331 Acceptable Cold study conducted in 

Iowa 

No None 

43159332 Acceptable Cold study conducted in 

Georgia 

43387721 

Acceptable 

(supplement to 

MRID 

43159331) 

Cold study conducted in 

Iowa 

43387722 

Acceptable 

(supplement to 

MRID 

431593332) 

Cold study conducted in 

Georgia 

43387724 Acceptable Radiolabeled study 

performed in Kentucky 

43387725 Acceptable No None 

Radiolabeled study 

performed in North 

Carolina 

43387726 Acceptable Storage stability 

(Kentucky) 
35 

Guideline

MRID 

(part of the 

molecule that 

was 

radiolabeled)

Study 

Classification

Comments on Study 

Classification 

Data 

Gap Comments 

43387727 Acceptable Storage stability (North 

Carolina) 

44449202 Not reviewed The study was submitted 

April 7, 1998 --- 

Dissipation of 

Prosulfuron in Soil 

Under Field Conditions 

With and Without 

Winter Wheat in Kansas

Bioconcentration 

Factor 

850.1730 Not applicable None No None 

8.2. Ecological Effects 

Several ecological effects studies on prosulfuron are needed to better assess the potential risk of 

exposure to non-target organisms. Tables 10 and 11 summarize the data that have been 

submitted for the parent compound and highlight existing data gaps. The following studies are 

recommended to decrease uncertainty in risk estimation and characterization of prosulfuron: 

• Tier II Terrestrial Plant Seedling Emergence (850.4225) and Vegetative Vigor 

(850.4250) Toxicity Studies with TEP [2 Studies] 

In the Tier II terrestrial plant studies that were previously conducted (MRIDs 429747-01; 

429497-10), plants were exposed to technical grade active ingredient (TGAI) instead of a typical 

end-use product (TEP), which is recommended in 40 CFR Part 158 and in OCSPP terrestrial 

plant toxicity test guidelines. Formulated products may contain adjuvants and/or surfactants 

which are intended to increase the efficacy of the compound, but may also increase exposure 

and/or toxicity to non-target organisms as well. Therefore, it is recommended that additional 

tests be conducted with TEP. 

• Special Study for Non-Target Plant Reproductive Toxicity (Non-Guideline) for TEP 

[1 Study] 

Terrestrial plants are typically very sensitive to sulfonylurea urea herbicide exposure. There is 

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

below effects on vegetative growth or visual injury (Fletcher et al., 1993). Uncertainty regarding 

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

in the environmental fate and effects assessment supporting the Reregistration Eligibility 

Decision (RED) for chlorsulfuron (US EPA, 2003). 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 
36 

are dependent on plant reproduction as a source of food and habitat. A solid understanding of the 

potential risks to plants is therefore essential. To the extent that terrestrial plant reproduction is 

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

underestimated in the risk assessment. Additional information on the reproductive toxicity of 

prosulfuron to terrestrial plants is necessary to address this uncertainty. 

• Avian Acute Oral Toxicity Test with a Passerine Species (850.2100) [1 Study] 

According to 40 CFR 158.630, acute oral toxicity data are now required for a passerine species. 

No acute oral toxicity data related to prosulfuron have been identified in the scientific literature 

(using ECOTOX). Although available acute oral toxicity data for birds indicate that prosulfuron 

is classified as slightly toxic to practically non-toxic to other bird species, several mortalities 

and/or sublethal effects were observed in acute oral toxicity studies with other avian species 

(MRIDs 426852-05, 426852-06). Since passerines may potentially be more sensitive to 

prosulfuron than other avian taxa, an acute oral toxicity study is recommended. 

Table 11. Summary of Submitted Aquatic and Terrestrial Animal Effects Studies and 

Data Gaps for Parent Prosulfuron. 

Guideline Description—Test Substance MRID(s) Study 

Classification

Data 

Gap Comments 

Avian and Mammalian Testing 

850.2100 Avian acute oral toxicity, 

waterfowl—TGAI 426852-05 Acceptable No 

850.2100 

Avian acute oral toxicity, 

upland game bird species—

TGAI 

426852-06 Acceptable No 

Non-definitive endpoint is 

acceptable at current 

maximum application rate 

of 0.0356 lbs ai/A†

850.2100 Avian acute oral toxicity, 

passerine species—TGAI None N/A Yes 

Part of data requirements as 

of December 2007 to 

address passerine 

sensitivity concerns 

850.2200 Avian dietary toxicity, 

waterfowl species—TGAI 426852-07 Acceptable No 

Non-definitive endpoint is 

acceptable at current 

maximum application rate 

of 0.0356 lbs ai/A†

850.2200 Avian dietary toxicity, upland 

game bird—TGAI 426852-08 Acceptable No 

Non-definitive endpoint is 

acceptable at current 

maximum application rate 

of 0.0356 lbs ai/A†

850.2300 Avian reproduction, waterfowl 

species—TGAI 429497-01 Acceptable No 

850.2300 Avian reproduction, upland 

game bird species—TGAI 429497-02 Unacceptable No Data requirement 

previously waived 

850.2400 Wild mammal toxicity—TGAI None N/A No 

Not triggered based on 

ecotoxicity data, predicted 

EECs, fate properties, and 

use pattern criteria.
37 

Guideline Description—Test Substance MRID(s) Study 

Classification

Data 

Gap Comments 

850.2500 Simulated or actual field 

testing—TEP None N/A No 

Not triggered based on 

ecotoxicity data, predicted 

EECs, fate properties, and 

use pattern criteria. 

Aquatic Animal Testing 

850.1010 Freshwater invertebrate, acute 

toxicity—TGAI 426852-11 Acceptable No 

Non-definitive endpoint is 

acceptable since no 

mortalities or sublethal 

effects occurred 

850.1025 Estuarine/Marine Mollusk acute 

toxicity—TGAI 432126-02 Acceptable No 

Non-definitive endpoint is 

acceptable since no 

mortalities or sublethal 

effects occurred 

850.1035 Estuarine/Marine crustacean 

acute toxicity—TGAI 432126-01 Acceptable No 

Although mortality was 

observed during limit test, 

additional data are not 

recommended 

850.1075 Freshwater fish, acute toxicity, 

warm water species—TGAI 426852-09 Acceptable No 

Non-definitive endpoint is 

acceptable since no 

mortalities or sublethal 

effects occurred 

850.1075 Freshwater fish, acute toxicity, 

cold water species—TGAI 426852-10 Acceptable No 

Non-definitive endpoint is 

acceptable since no 

mortalities or sublethal 

effects occurred

850.1075 Estuarine/Marine fish acute 

toxicity—TGAI 429497-06 Acceptable No 

850.1300 Freshwater invertebrate, 

reproduction test—TGAI 429497-08 Acceptable No 

850.1350 Estuarine/marine invertebrate, 

reproduction test—TGAI None N/A No 

A chronic invertebrate lifecycle toxicity test is not 

triggered according to 40 

CFR 158 

850.1400 Freshwater fish, early life stage 

test—TGAI 429497-07 Acceptable No 

850.1400 Saltwater fish, early life stage 

test—TGAI None N/A No 

A fish early life stage 

toxicity test is not triggered 

according to 40 CFR 158 

850.1500 Freshwater fish life cycle test None N/A No 

Data requirement not 

triggered 

EEC <0.1 of NOAEC from 

freshwater fish ELS and 

daphnid life cycle tests 
38 

Guideline Description—Test Substance MRID(s) Study 

Classification

Data 

Gap Comments 

850.1500 Estuarine/marine Fish life cycle 

test None N/A No 

Data requirement not 

triggered 

EEC <0.1 of NOAEC from 

freshwater fish ELS and 

daphnid life cycle tests 

850.1950 Simulated or actual field testing 

for aquatic organisms None N/A No 

Higher tier testing to 

address risk uncertainties 

have not been identified at 

this time 

Sediment Testing 

850.1735 Whole sediment 10-d 

freshwater invertebrate—TGAI None N/A No 

Data requirement not 

triggered 

Half life >10 days 

Kd <50 

Log KOW <3 

KOC <1,000 

850.1740 

Whole sediment 10-d 

estuarine/marine invertebrate—

TGAI 

None N/A No 

Data requirement not 

triggered 

Half life >10 days 

Kd <50 

Log KOW <3 

KOC <1,000 

Agencywide 

guideline 

Whole sediment chronic 

freshwater and/or marine 

invertebrate—TGAI 

None N/A No 

Data requirement not 

triggered: 

Kd <50 

Log KOW <3 

KOC <1,000 

Benthic EEC <0.01 of 

acute LC50/EC50 values 

Insect Pollinator Testing 

850.3020 Honeybee acute contact 

toxicity—TGAI 430800-47 Acceptable No 

850.3030 Honeybee toxicity of residues 

on foliage—TEP None N/A No Data requirement not 

triggered 

850.3040 Field testing for pollinators None N/A No 

Higher tier testing to 

address risk uncertainties 

have not been identified at 

this time 

†

 These non-definitive endpoint values prohibit the ability to determine a definitive risk value. However, given the 

current maximum application rate (0.0365 lbs ai/A), dietary- and dose-based EECs calculated using TREX ver. 

1.4.1, would be lower than these values, and the potential for acute risk is considered low. If higher outdoor spray 

application rates are identified, the adequacy of these non-definitive values to support a determination of low 

potential for acute risk would need to be re-evaluated. 
39 

Table 12. Summary of Submitted Aquatic and Terrestrial Plant Effects Studies and Data 

Gaps for Parent Prosulfuron. 

Guideline Description MRID Study 

Classification 

Data 

Gap Comments 

850.4225 

Tier II 

Seedling emergence (10 

species)—TGAI 429747-01 Supplemental† Yes 

TGAI was used; TEP is 

recommended for terrestrial plant 

toxicity studies. 

850.4250 

Tier II 

Vegetative vigor (10 

species)—TGAI 429497-10 Supplemental† Yes 

TGAI was used; TEP is 

recommended for terrestrial plant 

toxicity studies. 

N/A Seed germination (10 

species)—TGAI 429497-09 Acceptable No 

TGAI was used; TEP is 

recommended for terrestrial plant 

toxicity studies 

Nonguideline Terrestrial Plant 

Reproduction Study—TEP N/A None Yes Special study; see justification. 

TEP should be used. 

850.4400 

Tier I 

and/or II 

Tier II Aquatic plant 

growth, vascular plant — 

TGAI 

429497-13 Acceptable No 

850.5400 

Tier I 

and/or II 

Tier II Aquatic Plant, 

freshwater green alga 

species—TGAI 

429497-14 Acceptable No 

850.5400 

Tier I 

and/or II 

Tier II Aquatic Plant, 

freshwater diatom—TGAI 429497-15 Supplemental† No 

This study is downgraded to 

supplemental because of high 

variability in the data and a low 

starting cell count. However, a 

new study is not recommended. 

850.5400 

Tier I 

and/or II 

Tier I Aquatic Plant, 

marine diatom — TGAI 429497-12 Acceptable No 

<50% reduction in growth 

observed a limit dose. Also, the 

maximum peak EEC is more than 

10 times lower than the limit 

concentration tested. Tier II testing 

is not recommended. 

850.5400 

Tier I 

and/or Tier 

II 

Tier II Aquatic Plant, 

cyanobacterium — TGAI 429497-11 Acceptable No 

<50% reduction in growth 

observed a limit dose. Also, the 

maximum peak EEC is more than 

10 times lower than the limit 

concentration tested. Tier II testing 

is not recommended. 

†

Studies recently downgraded to “supplemental” based on current Agency standards.

Rationale for studies not being requested:

An avian reproduction study with the bobwhite quail (MRID432635-01) was previously 

submitted to EPA for review and deemed “unacceptable.” The study was primarily rejected due 

to high control mortality in the parental birds. This study was later waived on the grounds that 

prosulfuron exhibits low toxicity to birds, and also because application rates of the chemical at 

the time were low. Since application rates have not increased since the waiver was granted and 

no new data or incidents have been reported to demonstrate avian toxicity, it is recommended 
40 

that the waiver for this data requirement be extended into the current registration review period. 

However, additional data may be recommended in the future if proposed application rates 

increase from those currently on the labels. 

An acute toxicity test with the estuarine/marine crustacean, Americamysis bahia (Mysidae), was 

previously submitted and considered “acceptable” (MRID 432126-01). However, it should be 

noted that multiple mortalities occurred in the treatment group exposed to prosulfuron. While 

there was less than 50% mortality at the limit dose, the study indicates that there is a potential of 

mortality to non-target crustaceans from the exposure to this pesticide. Based on the Agency’s 

current guidance, additional data is typically recommended when any mortality is recorded 

during a limit test. However, since the highest preliminary surface water EEC value for 

prosulfuron (1.71 μg ai/L) is more than four orders of magnitude below the non-definitive LC50

value (150,000 μg ai/L), it is unlikely that additional study data would result in risks of concern 

for mysids at current application rates. Therefore, a definitive test on mysid acute toxicity is not 

requested at this time, but may be recommended in the future if proposed application rates 

increase from those currently on the labels. 

An aquatic nonvascular plant toxicity test (MRID 429497-15) with the freshwater diatom 

Navicula pelliculosa was recently downgraded from “acceptable” to “supplemental” and is not 

suitable for quantitative use in risk assessment. However, a new study is not being recommended 

at this time based on the following rationale: Coefficients of variation in day 5 cell density 

ranged from 17 to 101 in treatment groups versus 59 in the control. This precludes the ability to 

detect significant effects even when the deviation from the control is substantial (approximately 

20-25% inhibition at the two highest concentrations tested were not statistically significant). 

However, the benefit of an additional study with the same species is likely to be low. A 

definitive NOAEC and EC50 have been established for another freshwater species, 

Pseudokirchneriella subcapitata, and these values are expected to be lower (more sensitive) than 

any endpoints derived from an additional data submission for N. pelliculosa. 

9. References 

9.1. Data Submitted To Support Registration 

Avian Single Dose Oral Toxicity 

42685205 Pedersen, C. (1992) CGA-152005 Technical: 14-Day Acute Oral LD50 Study in Mallard Ducks: Lab 

Project Number: 102-019-04. Unpublished study prepared by Bio-Life Assoc. Ltd. 48 p. 

42685206 Pedersen, C. (1991) CGA-152005 Technical: 21-Day Acute Oral LD50 Study in Bobwhite Quail: Lab 

Project Number: 102-004-03. Unpublished study prepared by Bio-Life Assoc. Ltd. 36 p. 

Avian Dietary Toxicity 

42685207 Pedersen, C. (1991) CGA-152005 Technical: 8-Day Acute Dietary LC50 Study in Mallard Ducklings: 

Lab Project Number: 102-002-02. Unpublished study prepared by Bio-Life Assoc. Ltd. 60 p. 

42685208 Pedersen, C. (1991) CGA-152005 Technical: 8-Day Acute Dietary LC50 Study in Bobwhite Quail: Lab 

Project Number: 102-018-01. Unpublished study prepared by Bio-Life Assoc. Ltd. 63 p. 

Avian Reproduction 
41 

42949701 Pedersen, C.; DuCharme, D. (1993) CGA-152005 Technical: Toxicity and Reproduction Study in 

Mallard Ducks: Lab Project Number: BLAL NO. 102-017-08. Unpublished study prepared by Bio-Life 

Associates, Ltd. 948 p. 

42949702 Pedersen, C.; DuCharme, D. (1993) CGA-152005 Technical: Toxicity and Reproduction Study in 

Bobwhite Quail: Lab Project Number: BLAL NO. 102-016-07. Unpublished study prepared by Bio-Life 

Associates, Ltd. 708 p. 

43263501 Hosmer, A. (1994) Response to EPA Data Evaluation Record for the Study: CGA-152005 Toxicity and 

Reproduction Study in Bobwhite Quail: Lab Project Number: ABR/94044. Unpublished study prepared 

by Ciba-Geigy Corp. 44 p. 

Acute Toxicity to Freshwater Fish 

42685209 Boeri, R.; Ward, T. (1991) Acute Flow-through Toxicity of CGA 152005 (Technical) to the Bluegill 

Sunfish, (Lepomis macrochirus): Lab Project Number: 90163-CG. Unpublished study prepared by 

Envirosystems, Div. of Resource Analysts, Inc. 25 p. 

42685210 Boeri, R.; Ward, T. (1991) Acute Flow-through Toxicity of CGA 152005 (Technical) to the Rainbow 

Trout, (Oncorhynchus mykiss): Lab Project Number: 900164-CG. Unpublished study prepared by 

Envirosystems, Div. of Resource Analysts, Inc. 24 p. 

42949703 Boeri, R.; Ward, T. (1991) CGA-152005 Technical: Acute Flow-Through Toxicity of CGA-152005 to 

the Bluegill Sunfish, (Lepomis macrochirus): Lab Project Number: 90163-CG. Unpublished study 

prepared by Envirosystems Division. 25 p. 

42949704 Boeri, R.; Ward, T. (1991) CGA-152005 Technical: Acute Flow-Through Toxicity of CGA-152005 to 

the Rainbow Trout, (Oncorhynchus mykiss): Lab Project Number: 90164-CG. Unpublished study 

prepared by Envirosystems Division. 24 p. 

Acute Toxicity to Freshwater Invertebrates 

42685211 Boeri, R.; Ward, T. (1991) Acute Flow-through Toxicity of CGA 152005 (Technical) to the Daphnid, 

(Daphnia magna): Lab Project Number: 90165-CG. Unpublished study prepared by Envirosystems, Div. 

of Resource Analysts, Inc. 24 p. 

42949705 Ciba-Geigy Corp. (1993) CGA-152005 Technical: A Supplement to Acute Flow-Through Toxicity of 

CGA 152005 to the Daphnid, Daphnia Magna: MRID No. 42685211. Unpublished study. 15 p. 

Acute Toxicity to Estuarine/Marine Organisms 

42949706 Boeri, R.; Ward, T. (1991) CGA-152005: Acute Flow-through Toxicity of CGA 152005 to the 

Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: 9199-CG. Unpublished study 

prepared by Ciba-Geigy Corp. 23 p. 

43212601 Boeri, R.; Ward, T. (1991) Acute Flow-Through Toxicity of CGA-152005 to the Mysid, Mysidopsis 

bahia: Lab Project Number: 9198-CG. Unpublished study prepared by Envirosystems Division, 

Resource Analysts, Inc. 23 p. 

43212602 Boeri, R.; Ward, T. (1991) Acute Flow-Through Toxicity of CGA-152005 to the Eastern Oyster, 

Crassostrea virginica: Lab Project Number: 91100-CG. Unpublished study prepared by Envirosystems 

Division, Resource Analysts, Inc. 24 p. 

Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 

42949707 Ward, T. (1992) CGA-152005: Early Life-Stage Toxicity of CGA-152005 to the Fathead Minnow, 

Pimephales Promelas: Lab Project Number: 91133-CG. Unpublished study prepared by Envirosystems 

Division. 39 p. 

42949708 Ward, T.; Boeri, R. (1992) CGA-152005: Chronic Toxicity of CGA-152005 to the Daphnid, Daphnia 
42 

Magna: Lab Project Number: 91134-CG. Unpublished study prepared by Envirosystems Division. 36 p. 

Acute oral toxicity in rats 

42685215 Glaza, S. (1991) Acute Oral Toxicity Study of CGA-152005 Technical in Rats: Lab Project Number: 

10302700. Unpublished study prepared by Hazleton Wisconsin, Inc. 46 p. 

Subchronic Oral Toxicity: 90-Day Study 

42685232 Chow, E.; Morrissey, R. (1991) 90-day Dietary Rangefinding Study with CGA-152005 Technical in 

Rats: Final Report: Lab Project Number: F-00057. Unpublished study prepared by Ciba-Geigy Corp., 

Env. Health Ctr. 268 p. 

2-generation repro in rata 

43159319 Greci, L.; Turnier, J. (1993) Final Report: A Two-Generation Reproduction Study in Rats with CGA152005 Technical: Lab Project Number: F-00082. Unpublished study prepared by Environmental Health 

Center. 882 p. 

Aquatic plant growth 

42949711 Hughes, J.; Alexander, M. (1993) The Toxicity of CGA-152005 to Anabaena flos-aquae: Growth and 

Reproduction of Aquatic Plants, Tier 1: Lab Project Number: B267-54-2. Unpublished study prepared 

by Malcolm Pirnie, Inc. 61 p. 

42949712 Hughes, J.; Alexander, M. (1993) The Toxicity of CGA-152005 to Skeletonema costatum: Growth and 

Reproduction of Aquatic Plants, Tier 1: Lab Project Number: B267-54-5. Unpublished study prepared 

by Malcolm Pirnie, Inc. 61 p. 

Seed germination/seedling emergence and vegetative vigor 

42949709 Chetram, R. (1992) CGA-152005: Tier 2 Seed Germination Non-Target Phytotoxicity Study Using 

CGA-152005: Lab Project Number: BL91-448. Unpublished study prepared by Pan-Agricultural Labs, 

Inc. 108 p. 

42949710 White, T. (1992) CGA-152005: Tier 2 Vegetative Vigor Non-Target Phytotoxicity Study Using CGA152005: Lab Project Number: BL91-450. Unpublished study prepared by Pan-Agricultural Labs, Inc. 

263 p. 

42974701 Canez, V. (1992) Tier 2 Seedling Emergence Non-Target Phytotoxicity Study Using CGA-152005: Lab 

Project Number: BL91-449: 0805A4AH(MG-REPORTS): AL-91-126. Unpublished study prepared by 

Pan-Agricultural Labs, Inc. 273 p. 

Aquatic plant growth 

42949713 Hughes, J.; Alexander, M. (1993) The Toxicity of CGA-152005 to Lemna gibba G3: Growth and 

Reproduction of Aquatic Plants, Tier 2: Lab Project Number: B267-54-4. Unpublished study prepared 

by Malcolm Pirnie, Inc. 37 p. 

42949714 Hughes, J.; Alexander, M. (1993) The Toxicity of CGA-152005 to Selenastrum capricornutum: Growth 

and Reproduction of Aquatic Plants, Tier 2: Lab Project Number: B267-54-1. Unpublished study 

prepared by Malcolm Pirnie, Inc. 38 p. 

42949715 Hughes, J.; Alexander, M. (1993) The Toxicity of CGA-152005 to Navicula pelliculosa: Growth and 

Reproduction of Aquatic Plants, Tier 2: Lab Project Number: B267-54-3. Unpublished study prepared 

by Malcolm Pirnie, Inc. 35 p. 

Honey bee acute contact 
43 

42685212 Brantly, T. (1991) Contact Toxicity of CGA-152005 to the Honeybee (Apis mellifera): Lab Project 

Number: 109/21492/001: 109-001. Unpublished study prepared by Auburn Environmental Consulting & 

Testing. 13 p. 

Hydrolysis 

42685245 Phelps, W. (1993) Environmental Chemistry of CGA-152005: Lab Project Number ABR-93019. 

Unpublished study prepared by Ciba-Geigy Corp. 18 p. 

42685246 Kesterson, A. (1993) Hydrolysis of (carbon 14)Triazine CGA-152005 at pH 5,7,9: Lab Project Number: 

524: 3-91. Unpublished study prepared by PTRL East, Inc. 190 p. 

42685247 Kesterson, A. (1993) Hydrolysis of (carbon 14)Phenyl CGA-152005 at pH 5,7, and 9: Lab Project 

Number: 551: 22-91. Unpublished study prepared by PTRL East, Inc. 121 p. 

Photodegradation-water 

42685248 Kesterson, A. (1993) Solution Photolysis of (Carbon 14)Triazine CGA-152005 in Natural Sunlight: Lab 

Project Number: 570: 69-91. Unpublished study prepared by PTRL East, Inc. 127 p. 

42685249 Kesterson, A. (1993) Solution Photolysis of (carbon 14)Triazine CGA-152005 in Natural Sunlight: Lab 

Project Number: 569: 68-91. Unpublished study prepared by PTRL East, Inc. 125 p. 

43387710 Cruz, S. (1994) Measurement of the Ultraviolet Absorbance of CGA-152005 Degradates: Lab Project 

Number: ARB-94026: 184-94. Unpublished study prepared by Ciba-Geigy Corp. 60 p. 

Photodegradation-soil 

43159327 Atkins, R. (1994) Soil Surface Photolysis of Phenyl (carbon 14) CGA-152005 in Natural Sunlight: Lab 

Project Number: 573: 70-91. Unpublished study prepared by PTRL East, Inc. 87 p. 

43159328 Atkins, R. (1994) Soil Surface Photolysis of Triazine (carbon 14) CGA-152005 in Natural Sunlight: Lab 

Project Number: 574: 67-91. Unpublished study prepared by PTRL East, Inc. 88 p. 

Aerobic soil metabolism 

42685250 Atkins, R. (1993) Aerobic Metabolism of (Carbon 14)Triazine CGA-152005 in Sandy Loam Soil: Lab 

Project Number: 585: 88-91. Unpublished study prepared by PTRL East, Inc. 156 p. 

42685251 Atkins, R. (1993) Aerobic Metabolism of (carbon 14)Phenyl-CGA-152005 in Sandy Loam Soil: Lab 

Project Number: 583: 86-91. Unpublished study prepared by PTRL East, Inc. 175 p. 

43387712 Atkins, R. (1994) Aerobic Metabolism of Triazine-(Carbon 14)-CGA-152005 in Soil at Approximately 

pH 6: Lab Project Number: 636: 158-91. Unpublished study prepared by PTRL East, Inc. 212 p. 

43387713 Atkins, R. (1994) Aerobic Metabolism of Phenyl-(Carbon 14)-CGA-152005 in Soil at Approximately 

pH 6: Lab Project Number: 635: 157-91. Unpublished study prepared by PTRL East, Inc. 225 p. 

Anaerobic soil metabolism 

42685252 Atkins, R. (1993) Anaerobic Metabolism of (carbon 14)Triazine-CGA-152005 in Sandy Loam Soil: Lab 

Project Number: 586: 87-91. Unpublished study prepared by PTRL East, Inc. 103 p. 

42685253 Atkins, R. (1993) Anaerobic Metabolism of (carbon 14)Phenyl-CGA-152005 in Sandy Loam Soil: Lab 

Project Number: 584: 85-91. Unpublished study prepared by PTRL East, Inc. 103 p. 

43387714 Atkins, R. (1994) Anaerobic Metabolism of Triazine-(Carbon 14)-CGA-152005 in Soil at 

Approximately pH 6: Lab Project Number: 638: 155-91. Unpublished study prepared by PTRL East, 

Inc. 128 p. 

43387715 Atkins, R. (1994) Anaerobic Metabolism of Phenyl-(Carbon 14)-CGA-152005 in Soil at Approximately 
44 

pH 6: Lab Project Number: 637: 156-91. Unpublished study prepared by PTRL East, Inc. 157 p. 

Anaerobic aquatic metab. 

43387716 Atkins, R. (1994) Anaerobic Aquatic Metabolism of Triazine-(Carbon 14)-CGA-152005: Lab Project 

Number: 640: 163-91. Unpublished study prepared by PTRL East, Inc. 351 p. 

43387717 Atkins, R. (1994) Anaerobic Aquatic Metabolism of Phenyl-(Carbon 14)-CGA-152005: Lab Project 

Number: 625: 162-91. Unpublished study prepared by PTRL East, Inc. 352 p. 

Aerobic aquatic metab. 

43387718 Atkins, R. (1994) Aerobic Aquatic Metabolism of Triazine-(Carbon 14)-CGA-152005: Lab Project 

Number: 639: 160-91. Unpublished study prepared by PTRL East, Inc. 161 p. 

43387719 Atkins, R. (1994) Aerobic Aquatic Metabolism of Phenyl-(Carbon 14)-CGA-152005: Lab Project 

Number: 624: 161-91. Unpublished study prepared by PTRL East, Inc. 150 p. 

Leach/adsorp/desorption 

42685254 Kesterson, A. (1992) Column Leaching of (carbon 14)Triazine-CGA-152005 in Four Soil Types: Lab 

Project Number: 533: 7-91. Unpublished study prepared by PTRL East, Inc. 194 p. 

42685255 Atkins, R. (1993) Column Leaching of (carbon 14)Triazine-CGA-152005 in Four Soil Types following 

30 Days of Aerobic Aging: Lab Project Number: 534: 8-91. Unpublished study prepared by PTRL East, 

Inc. 215 p. 

42685256 Atkins, R. (1993) Column Leaching of (Carbon 14)Phenyl CGA-152005 in Four Soil Types Following 

30 Days of Aerobic Aging: Lab Project Number: 535: 9-91. Unpublished study prepared by PTRL East, 

Inc. 214 p. 

42685257 Kesterson, A. (1992) Soil Adsorption/Desorption of Triazine Labelled (Carbon 14) CGA-152005 by the 

Batch Equilibrium Method: Lab Project Number: 531: 6-91. Unpublished study prepared by PTRL East, 

Inc. 69 p. 

43159329 Kesterson, A. (1993) Soil Adsorption/Desorption of (carbon 14) CGA-159902 by the Batch Equilibrium 

Method: Lab Project Number: 532: 10-91. Unpublished study prepared by PTRL East, Inc. 60 p. 

43159330 Atkins, R. (1993) Soil Adsorption/Desorption of Phenyl-(carbon 14)-CGA-300406 by the Batch 

Equilibrium Method: Lab Project Number: 702: 114-92. Unpublished study prepared by PTRL East, Inc. 

78 p. 

43387720 Nixon, W. (1994) Soil Adsorption/Desorption of (Carbon 14)-G-28533 by the Batch Equilibrium 

Method: CGA-152005: Lab Project Number: 816: 326-93. Unpublished study prepared by PTRL East, 

Inc. 76 p. 

Terrestrial field dissipation 

43159331 Rice, F.; Wiepke, T. (1994) Dissipation of CGA-152005 in Soil under Field Conditions with and without 

Corn in Iowa: Final Report: Lab Project Number: 40198: CIGNC01G-2: 85-92. Unpublished study 

prepared by ABC Laboratories, Inc.; ALTA Analytical Laboratory, Inc. 420 p. 

43159332 Rice, F.; Wiepke, T. (1993) Dissipation of CGA-152005 in Soil under Field Conditions with and without 

Corn in Georgia: Final Report: Lab Project Number: 40199: CG-9202: 86-92. Unpublished study 

prepared by ABC Laboratories, Inc.; Enseco-Cal Lab. 277 p. 

43387721 Rice, F.; Wiepke, T. (1994) Dissipation of CGA-152005 in Soil Under Field Conditions with and 

without Corn in Iowa: Amendment Number 1 to Final Report: Lab Project Number: 40198A: 85-92. 

Unpublished study prepared by ABC Labs, Inc. and ALTA Analytical Labs, Inc. 111 p. 
45 

43387722 Rice, F.; Wiepke, T. (1994) Dissipation of CGA-152005 in Soil Under Field Conditions with and 

without Corn in Georgia: Amendment No. 1 to Final Report: Lab Project Number: 40199A:: 86-92. 

Unpublished study prepared by ABC Labs, Inc. and Enseco-CAL Lab. 81 p. 

43387724 Coody, P. (1994) Soil Dissipation of (Carbon 14)-CGA-152005 Under Actual Field Conditions in 

Kentucky: Lab Project Number: 696: 95-92. Unpublished study prepared by Ciba Plant Protection and 

PTRL East, Inc. 474 p. 

43387725 Coody, P. (1994) Soil Dissipation of (Carbon 14)-CGA-152005 Under Actual Field Conditions in North 

Carolina: Lab Project Number: 715. Unpublished study prepared by PTRL East, Inc. 425 p. 

44449202 Wiepke, T.; Judy, D.; Irrig, H. (1997) Final Report: Dissipation of Peak (Prosulfuron) on Soil Under 

Field Conditions with and without Winter Wheat in Kansas: Lab Project Number: 21-96: 43065. 

Unpublished study prepared by ABC Laboratories, Inc., and Novartis Crop Protection, Inc. 468 p. 

44449203 Purdy, J. (1995) Soil Dissipation Study at Three Trial Sites with CGA 152005 75WG: (Final Report): 

Lab Project Number: CER 01007/93: E3-06-065: 644-97. Unpublished study prepared by Envirotest 

Labs., and Novartis Crop Protection, Inc. 109 p. 

44538301 Wiepke, T. (1998) Final Report Amendment No.1: Dissipation of Peak (Prosulfuron) in Soil Under Field 

Conditions with and without Winter Wheat in Kansas: Lab Project Number: 21-96: 43065: 168002. 

Unpublished study prepared by ABC Labs., Inc. and Novartis Crop Protection, Inc. 32 p. 

 

Non-Guideline Study 

42974700 Ciba-Geigy Corp. (1993) Submission of Ecological Effects Data in Response to EPA Request for Data 

in Support of Experimental Use Permit for CGA-152005 Herbicide (Exceed) on Corn. Transmittal of 1 

Study. 

9.2. Open-literature Citations

Battaglin, W.A., Furlong, E.T., Burkhardt, M.R., and Peter, C.J., 1999, Occurrence of 

sulfonylurea, imidazolinone, and other herbicides in Midwestern rivers, reservoirs, and 

ground water, 1998, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological 

Survey Toxic Substances Hydrology Program--Proceedings of the Technical Meeting, 

Charleston, South Carolina, March 8- 12, 1999--Volume 2 of 3--Contamination of 

Hydrologic Systems and Related Ecosystems: U.S. Geological Survey Water-Resources 

Investigations Report 99-40 18B, p.2 15-226. 

Battaglin, W.A., Furlong, E.T., Burkhardt, M.R., and Peter, C.J., 2000, Occurrence of 

sulfonylurea, sulfonamide,imidazolinone, and other herbicides in rivers, reservoirs and 

ground water in the Midwestern United States, 1998:The Science of the Total 

Environment, v. 248, no. 2-3, p. 123-133.

Battaglin, W.A., Furlong, E.T., and Burkhardt, M.R. 2001, Concentration of selected 

sulfonylurea, sulfonamide, and imidazolinone herbicides, other pesticides, and nutrients 

in 71 streams, 5 reservoir outflows, and 25 wells in the midwestern United States, 1998: 

U.S. Geological Survey Water-Resources Investigations Report 00-4225, 123 p. 

Fletcher, J. S., Nellessen, J. E., & Pfleeger, T. G. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on 

plants. Environmental Toxicology and Chemistry, 13(9), 1383-1391. 
46 

Fletcher, J. S., Pfleeger, T. G., & Ratsch, H. C. 1993. Potential environmental risks associated 

with the new sulfonylurea herbicides. Environmental Science and Technology, 27(10), 

2250-2252. 

Hoerger, F., & Kenaga, E. E. 1972. Pesticide Residues on Plants: Correlation of Representative 

Data as a Basis for Estimation of their Magnitude in the Environment. In F. Coulston & 

F. Korte (Eds.), Environmental Quality and Safety: Chemistry, Toxicology, and 

Technology (Vol. 1, pp. 9-28). New York: Academic Press. 

SLUA report. Prosulfuron. Screening Level Usage Analysis. Environmental Protection Agency, 

Biological and Economic Analysis Division, Office of Pesticide Programs, United States 

Environmental Protection Agency. September 1, 2011. 

Steinheimer, T.R., Pfeiffer, R.L., Scoggin, K.D., and Battaglin, W.A., 2000, Reconnaissance 

survey of sulfonamide. sulfonylurea and imidazolinone herbicides in surface streams and 

groundwater of the Midwestern United States, in Steinheimer, T.R., Ross, L.J., and 

Spittler, T.D., eds., Agrochemical Fate and Movement--Perspective and Scale of Study: 

American Chemical Society Symposium series 75 1, p. 248-271. 

Teske, M. E., & Curbishley, T. B. 2003. AGDISP Version 8.07 User Manual. Prepared For 

United States Department of Agriculture Forest Service. C.D.I. Technical Note No. 02-

06. June 2003. 

USEPA. 1995. Review of data submitted towards registration of the new herbicide prosulfuron 

and end-products PEAK and EXCEED for uses on corn. DP barcode: D189457, 

D205396, D205400, D208195, D208196 and D212748. Memo From Akiva D. 

Abramovitch To Robert J. Taylor and Edward Allen. Environmental Fate and Effects 

Division. Office of Pesticide Programs, United States Environmental Protection Agency. 

April 28, 1995. 

USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. United States 

Environmental Protection Agency (USEPA). Risk Assessment Forum. Office of 

Research and Development. Available at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=12460 

USEPA. 2003. Registration Eligibility Decisions: Environmental Fate and Ecological Effects 

Risk Assessment for Chlorsulfuron (DP Barcode: D290034). 

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

Programs. United States Environmental Protection Agency (USEPA). Environmental 

Fate and Effects Division. Office of Pesticide Programs. Available at 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf (Accessed June 19, 2009). 

USEPA. 2005. PRZM 3.12.2: Users Manual. Online at: 

http://www.epa.gov/oppefed1/models/water/#przm 
47 

USEPA. 2005. EXAMS 2.98.04.06: Users Manual. Online at: 

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

USEPA. 2006. Water models PE Version 5: User Manual. Online at: 

http://www.epa.gov/oppefed1/models/water/pe5_user_manual.htm 

USEPA. 2006. Drinking Water Exposure Assessment for Prosulfuron Usage on Small Grains 

and Corn. DP barcode 326831. Memorandum From Michael Barrett to Vickie Walters 

and Jim Tompkins. Environmental Fate and Effects Division, Office of Pesticide 

Programs, United States Environmental Protection Agency. November 20, 2006. 

USEPA. 2009. Prosulfuron. REVISED Human Health Risk Assessment for the Proposed 

Establishment of Permanent Tolerances for Uses in/on Cereal Grains (Crop Group 15), 

Except Rice. Memorandum From Breann Hanson to Christina Swartz and Kathryn 

Montague. Alternative Risk Integration and Assessment (ARIA) Team Risk Integration 

Minor Use and Emergency Response Branch (RIMUERB) Registration Division. 

October 20, 2009. 

USEPA. 2010. Development and Use of Percent Cropped Area Adjustment Factors in Drinking 

Water Exposure Assessments. U.S. Environmental Protection Agency, Office of chemical 

Safety and Pollution Prevention, Office of Pesticide Programs, Environmental Fate and 

Effects Division, September 9, 2010. Online at: 

http://www.epa.gov/oppefed1/models/water/pca_adjustment_dwa.html

USEPA. 2011 BEAD Chemical Profile for Registration Review: Prosulfuron (129031)

Memorandum From Sunil Ratnayake, Sepehr Haddad, and Stephen Smearman to Andrea 

Mojica. Biological and Economic Analysis Division, Office of Pesticide Programs, 

United States Environmental Protection Agency. October 12, 2011. 

USFWS/NMFS. 1998. Endangered Species Consultation Handbook: Procedures for Conducting 

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

Final Draft. United States Fish and Wildlife Service (USFWS) and National Marine 

Fisheries Service (NMFS). Available at: 

http://www.fws.gov/endangered/consultations/s7hndbk/s7hndbk.htm 

Willis, G.H. and L.L. McDowell. 1987. Pesticide Persistence on Foliage in Reviews of 

Environmental Contamination and Toxicology. 100:23-73.
48 

Appendix A. Supplemental Environmental Fate Information

A1. Sorption Coefficients and Mobility 

Table A1 summarizes the sorption coefficients measured for prosulfuron. Freundlich adsorption 

coefficients ranged from 0.75 to 2.78 and Freundlich desorption coefficients ranged from 0.0 to 

7.95. It was apparent that the mobility of prosulfuron and its degradates decreased with 

increasing soil organic matter. Limited data are available to understand the influence of pH on 

sorption and thus a full analysis of the influence of various soil/sediment constituents cannot be 

fully understood. 

Table A1. Summary of measured sorption coefficients for prosulfuron degradates at 25o

C. 

Soil, 

% OC

pH

KF

ads

(L/kg-soil)a

KF

des

(L/kg-soil)b

KOC

(L/kg-OC)c nads/ndes d

Prosulfuron (MRID:42685257)

Loamy sand, 

0.42%

pH 7.7 

0.074 1.15 17.60 1.22/1.14 

Sandy Loam, 

1.79%

 pH 7.8 

0.273 1.78 15.3 1.17/1.02 

Silt Loam 

1.58% 

pH 6.5 

0.293 7.95 18.6 1.16/0.80 

Silty Clay Loam

0.61%

pH 6.5 

0.252 2.37 41.3 1.16/1.27 

CGA-159902 (MRID: 43159329)

Loamy Sand 

0.42% 

pH 7.7 

0.400 3.10 95.4 1.08/0.96 

Sandy Loam 

1.79% 

pH 7.8 

1.24 4.95 69.5 1.20/1.10 

Silt Loam 

1.58% 

pH 6.5 

0.765 4.71 48.4 1.24/1.09 

Silty Clay Loam 

0.61% 

pH 6.9 

0.587 2.97 96.2 1.06/1.09 

CGA-150829 (MRID: 41656209)e

Sand 0.230 1.07 78 1.15/1.03 

Sandy Loam 2.78 1.41 163 0.98/1.12 

Silt Loam Soil 

0.96 1.84 64 1.18/1.14 
49 

Soil, 

% OC

pH

KF

ads

(L/kg-soil)a

KF

des

(L/kg-soil)b

KOC

(L/kg-OC)c nads/ndes d

Silty Clay Loam 1.2 2.96 200 1.22/1.08 

CGA-300406 (MRID: 43159330) 

Loamy Sand 

0.42% 

pH 6.5 

0.53 6.05 126 0.81/0.76 

Sandy Loam 

1.00% 

pH 6.8 

0.490 2.80 49 1.15/0.96 

Loam 

1.11% 

pH 6.7 

0.470 3.60 43 1.13/0.89 

Silty Clay Loam 

2.59 % 

pH 6.4 

1.27 4.30 49 1.07/1.00 

G-28533 (MRID: 43387720) 

Sandy Loam 

1.00% 

pH 6.8 

0.124 0.00 12.4 1.02/-0.013 

Loam 

0.42% 

pH 6.7 

0.076 0.597 18.1 0.959/1.09 

Sand 

1.11% 

pH 6.5 

0.208 0.554 18.7 0.984/1.11 

Silty Clay Loam 

1.67 % 

pH 6.8 

0.273 1.27 16.3 0.991/1.08 

a

 KF

ads -Freundlich adsorption coefficient (Kd) 

b KF

des -Freundlich desorption coefficient c

 KOC = regressed Kd *100/% OC

d n=1/slope of the adsoption or desorption of linear regression of Freundlich equation x/m=(1/n)(lnCe) + ln Kd e DER and study cannot be located therefore the percent of organic carbon and pH were not found. 

Both the batch equilibrium adsorption/desorption studies and the soil column leaching studies 

suggest that parent prosulfuron somewhat irreversibly adsorbs to soils (that is, once sorbed it 

does not desorb readily). However, both Freundlich sorption constants for parent prosulfuron 

(less than 1.0 in each of four different soils), and the appearance of high amounts of prosulfuron 

in leachates in soil column leaching studies with unaged prosulfuron, indicate high potential for 

leaching of prosulfuron and its degradates to groundwater.

Table A2. Summary of Storage Stability Studies 

Parameter Value(s) and Units Source Comments 

Storage Stability Prosulfuron and its degradates have been 

shown to be relatively stable in frozen 

soil after storage for a year at -20 °C 

43387726 None 
50 

Parameter Value(s) and Units Source Comments 

Prosulfuron and its degradates were 

shown to be stable in water during frozen 

storage for up to 422 days. 

Concentrations of parent compound 

remained unchanged. 

43387724 None 

No evidence of degradation for 

prosulfuron or its degradates in frozen 

conditions after 342 days. 

43387727 None 

Table A3. Structures of Prosulfuron and Its Environmental Transformation Products. 

Code Name/ Synonym/ 

Chemical Name/ Formula/MW/ SMILES Chemical Structure 

Prosulfuron, CGA-152005 

IUPAC: 1-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-3-[2-

(3,3,3-trifluoropropyl)phenylsulfonyl]urea 

CAS: N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-

yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenesulfonamide 

CAS No.: 094125-34-5 

Formula: C15H16F3N5O4S 

MW: 419.38 

SMILES:

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C

2=NC(=NC(=N2)OC([H])([H])[H])C)[H])[H] 

CGA-159902 

IUPAC: 2-(3,3,3-trifluoropropyl)phenyl sulfonamide 

CAS: 2-(3,3,3-trifluoropropyl)-benzenesulfonamide 

CAS No.: 

Formula: C9H10F3N1O2S1 

MW: 253.24 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N([H])[H] 

CGA-150829 

IUPAC: 4-methoxy-6-methyl-1,3,5-triazin-2-amine 

Formula: C5H8N4O1

MW: 140.15 

SMILES: N(C1=NC(=NC(=N1)C)OC)([H])[H] 
51 

Code Name/ Synonym/ 

Chemical Name/ Formula/MW/ SMILES Chemical Structure 

CGA-300406 

IUPAC: N-[[(4-hydroxy-6-methyl-1,3,5-triazin-2-

yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenesulfonamide 

CAS: N-[[(1,4-dihydro-6-methyl-4-oxo-1,3,5-triazin-2-

yl)amino]carbonyl]-2-(3,3,3-

trifluoropropyl)benzenesulfonamide] 

Other: O-desmethyl triasulfuron

Formula: C14H14 F3N5O4S1 

MW: 405.35 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C

2=NC(=NC(=N2)C)O[H])[H])[H] 

CGA-325025 

CAS: N-[[(4-amino-6-methyl-1,3,5-triazin-2-yl)-

amino]carbonyl]-2-(3,3,3-trifluoropropyl)-

benzenefulfonamide 

Other: Desmethoxyamino CGA-152005 

Formula: C14H15F3N6O3S1

MW: 404.37

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)NC(=O)NC2=

NC(=NC(=N2)N([H])[H])C 

CGA-325028 

CAS: N-

[[[[(aminocarbonyl)amino]carbonyl]amino]carbonyl-2-

(3,3,3-trifluoropropyl)

Formula: C12H13F3N4O5S1

MW: 382.32 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C(

=O)N(C(=O)N([H])[H])[H])[H])[H] 

 

CGA-325026 

CAS: N-[[aminocarbonyl)amino]carbonyl]-2-(3,3,3-

trifluoropropyl) 
52 

Code Name/ Synonym/ 

Chemical Name/ Formula/MW/ SMILES Chemical Structure 

Formula: C11H12F3N3O4S1

MW: 339.29 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C(

=O)N([H])[H])[H])[H] 

CGA-325027 

CAS: N-(aminocarbonyl)-2-(3,3,3-trifluoropropyl) 

MW: 296.27 

Formula: C10H11F3N2O3S1 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N([H

])[H])[H] 

G-28533 

CAS: 6-methyl-1,3,5-triazine-2,4(1H,3H)-dione 

MW: 127.10 

Formula: C4H5N3O2

SMILES: C1(=NC(=NC(=N1)C)O[H])O[H] MOL FOR: 
53 

Code Name/ Synonym/ 

Chemical Name/ Formula/MW/ SMILES Chemical Structure 

NANC-CGA-159902

CAS: N-[[aminocarbonyl)amino]carbonyl]-N-acetyl-2-

(3,3,3-trifluoropropyl)

MW: 338.30

Formula: C12H13F3N2O4S1

SMILES: 

C1=CC=CC(=C1CC(F)(F)F)S(=O)(=O)N(C(N(C(=O)N([

H])[H])[H])=O)C(=O)C 

CGA-188838 

CAS: 4-amino-6-methyl-1,3,5-triazin-2(1H)-one 

MW: 126.12 

Formula: C4H6N4O1

SMILES: N(C1=NC(=NC(=N1)C)O[H])([H])[H] 

CGA-325030 

CAS: N-[[[[[[[[2-(3,3,3-

trifluoropropyl)phenyl]sulfonyl]amino]carbonyl]amino]-

carbonyl]amino]carbonyl]acetamide 

Other: Polyimide Acetate 

MW: 424.35

Formula: C14H15F3N4O6S1

SMILES:

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C(

=O)N(C(=O)N(C(C)=O)[H])[H])[H])[H] 

CGA-273437 

CAS: N-[[[4-hydroxymethoxymethyl)-6-methoxy-1,3,5-

triazin-2-yl)amino]carbonyl]-2-(3,3,3-trifluoropropyl) 

MW: 435.38

Formula: C15H16F3N5O5S1 

SMILES: 

C(F)(F)(F)CCC1=C(C=CC=C1)S(=O)(=O)N(C(=O)N(C

2=NC(=NC(=N2)C(O[H])([H])[H])OC)[H])[H] 

MW =molecular weight. 
54 

Table A4. Summary of Maximum Amount of Transformation Products Observed in Fate 

Laboratory Studies. 

Transformation 

Product Study Type MRID Maximum %AR (day) Final %AR (study length)

CGA-150829 

Hydrolysis 42685246 

(triazine) 

46.1 (30, pH 5, 25o

C) 

0.8 (15, pH 7, 25o

C) 

0.5 (30, pH 9, 25o

C) 

46.1 (30, pH 5, 25o

C) 

0.7 (30, pH 7, 25o

C) 

0.5 (30, pH 9, 25o

C) 

Photodegradation 

 in water 

42685248 

(triazine) 

0.7 (30, pH 9, 25o

C, dark) 

2.5 (30, pH 9, 25o

C, 

irradiated) 

0.7 (30, pH 9, 25o

C, dark) 

2.5 (30, pH 9, 25o

C, irradiated)

Photodegradation 

 in soil 

43159328 

(triazine) 

4.4 (30, pH 7.2, 23.5o

C, dark) 

5.2 (30, pH 7.2, 23.2oC, 

irradiated) 

4.4 (30, pH 7.2, 23.5oC, dark) 

5.2 (30, pH 7.2, 23.2oC, 

irradiated) 

Aerobic soil 

42685250 

(triazine) 11.9 (366) 11.9 (366) 

43387712

 (triazine) 31.0 (366) 31.0 (366) 

Anaerobic soil 

42685252 

(triazine) 8.3 (90) 8.3 (90) 

43387714 

(triazine) 8.6 (60) 4.7 (90) 

Anaerobic Aquatic 

Metabolism 

43387716 

(triazine) 37.0 (90) 18.6 (365) 

Aerobic Aquatic 

Metabolism 

43387718 

(triazine) 9.0 (30) 9.0 (30) 

CGA-159902 

Hydrolysis 42685247 

(phenyl) 

64.4 (24 days, pH 5, 25o

C) 

0.9 (30 days, pH 7, 25o

C) 

1.3 (24 days, pH 9, 25o

C) 

58.5 (30 days, pH 5, 25 o

C) 

0.9 (30 days, pH 7, 25 oC) 

0.8 (30 days, pH 9, 25o

C) 

Photodegradation 

 in water 

42685249 

(phenyl) 

1.5 (30, pH 9, 25o

C, dark) 

1.4 (30, pH 9, 25o

C, 

irradiated) 

1.5 (30, pH 9, 25o

C, dark) 

1.4 (30, pH 9, 25oC, irradiated)

Photodegradation 

 in soil 

43159327 

(phenyl) 

4.9 (30, pH 7.2, 23.5o

C, dark) 

6.8 (30, pH 7.2, 23.2o

C, 

irradiated) 

4.9 (30, pH 7.2, 23.5o

C, dark) 

6.8 (30, pH 7.2, 23.2o

C, 

irradiated) 

Aerobic soil 

42685251 

(phenyl) 49 (366) 49 (366) 

43387713 

(phenyl) 47.8 (274) 47.6 (366) 

Anaerobic soil 

42685253 

(phenyl) 22.4 (92) 22.4 (92) 

43387715

(phenyl) 7.5 (90) 7.5 (90) 

Anaerobic Aquatic 

Metabolism 

43387717 

(phenyl) 60.1(91) 58.6 (364) 

Aerobic Aquatic 

Metabolism 43387719 1.3 (30) 1.3 (30) 

CGA-188838 Anaerobic Aquatic 

Metabolism 

43387716 

(triazine) 9.6 (365) 9.6 (365) 
55 

Transformation 

Product Study Type MRID Maximum %AR (day) Final %AR (study length)

G-28533 

Hydrolysis 42685246 

(triazine) 16.6 (30, pH 5, 25o

C) 16.6 (30, pH 5, 25oC) 

Anaerobic Soil 43387714 

(triazine) 1.5 (90) 1.5 (90) 

Anaerobic Aquatic 

Metabolism 

43387716 

(triazine) 24.3 (274) 19.9 (365) 

CGA-300406 

Hydrolysis 

42685246 

(triazine) 

8.6 (30, pH 5, 25o

C) 

0.5 (30, pH 7, 25o

C) 

2.6 (30, pH 9, 25o

C) 

46.1 (30, pH 5, 25o

C) 

0.5 (30, pH 7, 25o

C) 

2.6 (30, pH 9, 25o

C) 

42685247

(phenyl)

15.4 (7 days, pH 5, 25o

C) 

0.4 (24 days, pH 7, 25o

C) 

2.3 (30 days, pH 9, 25o

C) 

6.8 (30 days, pH 5, 25 oC) 

0.2 (30 days, pH 7, 25 oC) 

2.3 (30 days, pH 9, 25o

C) 

Photodegradation 

 in water 

42685248 

(triazine) 

3.3 (30, pH 9, 25o

C, dark) 

2.8 (21, pH 9, 25oC, 

irradiated) 

3.3 (30, pH 9, 25o

C, dark) 

2.6 (30, pH 9, 25oC, irradiated)

42685249

(phenyl)

3.6 (30, pH 9, 25o

C, dark) 

3.3 (30, pH 9, 25oC, 

irradiated) 

3.6 (30, pH 9, 25o

C, dark) 

3.3 (30, pH 9, 25o

C, irradiated)

Photodegradation 

 in soil 

43159328 

(triazine) 

2.6 (30, pH 7.2, 23.5o

C, dark) 

4.1 (30, pH 7.2, 23.2o

C, 

irradiated) 

2.6 (30, pH 7.2, 23.5o

C, dark) 

4.1 (30, pH 7.2, 23.2o

C, 

irradiated) 

43159327

(phenyl)

4.1 (30, pH 7.2, 23.5o

C, dark) 

4.9 (30, pH 7.2, 23.2o

C, 

irradiated) 

4.1 (30, pH 7.2, 23.5o

C, dark) 

4.9 (30, pH 7.2, 23.2o

C, 

irradiated) 

Anaerobic Soil 

43387714 

(triazine) 4.6 (90) 4.6 (90) 

42685252

(triazine) 9.1 (90) 9.1 (90) 

42685253 

(phenyl) 8.3 (92) 8.3 (92) 

43387715

(phenyl) 4.1 (90) 4.1 (90) 

Aerobic soil 

 

43387713 

(phenyl) 6.2 (184) 5.0 (366) 

43387712

(triazine) 6.0 (180) 3.8 (364) 

42685251 

(phenyl) 7.1 (184) 2.7 (366) 

42685250 

(triazine) 10.4 (90) 3.2 (366) 

Anaerobic Aquatic 

Metabolism 

43387717 

(phenyl) 14.6 (14) undetected (364) 

43387716

(triazine) 15.5 (14) undetected (364) 

Aerobic Aquatic 

Metabolism 

43387718 

(triazine) 2.6 (20) 1.9 (30) 

43387719

(phenyl) 3.0 (30) 3.0 (30) 

 43387712 5.8 (60) undetected (366) 
56 

Transformation 

Product Study Type MRID Maximum %AR (day) Final %AR (study length)

CGA-325025 

Aerobic soil (triazine) 

42685250 

(triazine) 21.6 (366) 21.6 (366) 

43387713 

(phenyl) 12.5 (122) 0.6 (366) 

Anaerobic soil 

42685252 

(triazine) 25.3 (90) 25.3 (90) 

43387714 

(triazine) 10 (90) 10(90) 

43387715

(phenyl) 18.3 (90) 18.3 (90) 

Aerobic Aquatic 

Metabolism 

43387718 

(triazine) 9.6 (20) 7.8 (30) 

Aerobic Aquatic 

Metabolism 

43387719 

(phenyl) 8.5 (30) 8.5 (30) 

CGA-325030 

Hydrolysis 

42685246 

(triazine) 22.2 (30, pH 5, 25o

C) 22.2 (30, pH 5, 25oC) 

42685247

(phenyl) 41.1 (30days, pH 5, 25o

C) 41.1 (30 days, pH 5, 25 oC) 

Anaerobic Aquatic 

Metabolism 

43387717 

(phenyl) 13.4(60) undetected (364) 

43387716

(triazine) 15.6 (30) undetected (364)

CGA-325028 

Aerobic soil 

43387712 

(triazine) 2.6 (366) 2.6 (366) 

43387713 

(phenyl) 1.9 (366) 1.9 (366) 

Anaerobic Aquatic 

Metabolism

43387717

(phenyl) 27.8 (364) 27.8 (364) 

Anaerobic Aquatic 

Metabolism

43387716

(triazine) 26.9 (273) 24.7 (365) 

CGA-325026 Anaerobic Aquatic 

Metabolism 

43387717 

(phenyl) 4.9 (273) 4.5 (364) 

CGA-325027 

Aerobic soil 43387713 

(phenyl) 2.5 (366) 2.5 (366) 

Anaerobic soil 43387715

(phenyl) 1.6 (90) 1.6 (90) 

Anaerobic Aquatic 

Metabolism

43387717

(phenyl) 4.5 (273) 4.1 (364) 

NANC-CGA159902 

Anaerobic Aquatic 

Metabolism 

43387717 

(phenyl) 2.9 (91) 2.0 (364) 

Anaerobic Aquatic 

Metabolism

43387716

(triazine) 3.0 (59) 2.9 (365)

Abbreviations: %AR=percent applied radioactivity present as the identified compound 

Hydrolysis of prosulfuron was found to be pH-dependent (MRIDs: 42685246 and 42685247 for 

triazine and phenyl label, respectively). At pH 5, hydrolysis was faster than at pH 7 and 9. At pH 

5, prosulfuron degraded with half-lives of 10 days (average of the two radiolabels; triazine and 
57 

phenyl labels). However at pH 7 and 9, prosulfuron was relatively stable during the 30 day study 

period and no major degradates were identified. Figure A5 shows the hydrolysis pathway of 

prosulfuron at pH 5. 

Figure A5. Hydrolysis Degradation Pathway of Prosulfuron (modified from MRID 

42685246 and 42685247), page 1.12 and 2.11, respectively. 

At pH 5, the major degradation products are bridge-cleavage degradates containing a single ring. 

These degradates are: 2-(3,3,3-trifluoropropyl)benzenesulfonamide (CGA-159902) and 4-

methoxy-6-methyl-l,3,5-triazin-2-amine (CGA-150829). Formation of these two degradates 

increases with time, reaching as high as 45% and 60% of the applied radioactivity for CGA150829 and CGA-159902, respectively, after 30 days. In the triazine-labeled study, another 

degradate containing an intact triazine ring was observed; this degradate was 6-methyl-1,3,5-

triazine-2,4(W, 3H)dione (G-28533) and the amount formed increased with time, reaching about 

15-16% at 30 days. 

In both the triazine- and the phenyl-labeled studies a degradate with an open triazine ring was 

isolated and characterized (IR, 13C and proton NMR, MS). The structure consistent with N-[ ( [ ( 

[([(2-[3,3,3-trifluoropropyl1phenyl)-sulfonyl]amino)carbonyl]amino)carbonyl]amino)carbonyl] 

acetamide (“polyimide acetate” or “CGA-325030”) was assigned to this degradate. Formation of 

CGA-325030 increased with time, reaching as high as 22% by 30 days. Finally, N-( [(4-

hydroxy-6-ethyl-1,3,5-triazin-2- yl)amino]carbonyl)-2(3, 3 ,3-trifluoropropyl) benzene 

sulfonamide (“desmethyl prosulfuron”, “desmethyl CGA-152005”, “CGA-300406”) have been 
58 

identified. The maximum amount of this degradate appeared at 10 days (14% of the applied), and 

decreased afterwards. Maximum concentrations of prosulfuron and transformation products 

observed in the studies are reported in Table 4. 

Two photodegradation in water studies were submitted and reviewed (MRIDs: 42685248 and 

42685249 for the triazine and phenyl labeled ring, respectively). Both studies are acceptable and 

satisfied the data requirement. In addition, the registrant submitted supplementary data on the 

electronic absorption spectra of several degradates in aqueous solutions at pHs 5, 7 and 9 

(MRIDs: 42387710 and 42387711). The electronic absorption spectra of prosulfuron and its 

major degradates are between 200 and 400 nm with no absorption at wavelength above 290 nm. 

Thus, prosulfuron nor its major degradates are likely to degrade by direct photolysis (in water 

and in soil). Similarly, the laboratory studies showed that direct photolysis is not an important 

degradative pathway for prosulfuron. Parent prosulfuron degraded slowly (10-15% degradation 

of the applied) in pH 9 buffer solutions, under both irradiated and dark conditions, during the 30-

days duration of the study. The degradates identified were similar to the hydrolysis products; 

CGA-150829, CGA-159902 and "desmethyl prosulfuron” or CGA-300406 with percentages that 

did not exceed 4.0 % of the applied in both irradiated and dark samples. More details about the 

transportation products can be found in Table A4. 

In terms of photodegradation in soils two studies were submitted and found that satisfy the data 

requirements (MRIDs: 43159327 and 43159328, phenyl and triazine labeled, respectively).The 

studies demonstrated that photodegradation on soil (sandy loam soil of the Huntington series; pH 

7.1; 13.0 to 35.3 °C; 37.52 °N, 84.20 °W), is not an important degradative pathway for 

prosulfuron. After 30 days (phenyl label) prosulfuron was recovered ~ 83.7% in the irradiated 

samples and 89.7% in the dark control samples. Between 16 to 20% parent prosulfuron degraded 

over the 30-day duration of the study in sunlight exposed samples. However, most of the 

degradation is likely to come from microbial and/or abiotic hydrolysis degradation. The 

degradates identified in this study were CGA-159902 and CGA-300406. CGA-159902 

accounted for 6.8 and 4.9% of the applied radioactivity for irradiated and dark samples, whereas 

CGA-300406 accounted for 4.9 and 4.1% of the applied, for irradiated and dark samples, 

respectively (Refer to Table 4). Two unidentified degradates were detected with maximum 

radioactivity of 2.7% of the applied radioactivity. The half-lives were estimated to be 130.9 and 

260.9 days for the irradiated and dark control samples, respectively. The volatiles never 

exceeded 1.1%. 

In the triazine label study, after 30 days prosulfuron was recovered ~ 93.8 % in the irradiated 

samples and 93.8% in the dark control samples. The degradates identified in this study were 

CGA-150829 and CGA-300406. CGA-150829 accounted for 5.2 and 4.4% of the applied 

radioactivity for irradiated and dark samples, whereas CGA-300406 accounted for accounted for 

4.1 and 2.6 % of the applied radioactivity in irradiated and dark samples respectively. Three 

unidentified degradates were detected in both irradiated and dark samples with maximum 

radioactivity of 2.3% of the applied radioactivity one of which was identified as CGA-325025. 

The half-lives were estimated to be 110.5 and 310.7 days for the irradiated and dark control 

samples, respectively. The volatiles never exceeded 0.4% of the applied radioactivity. 

In these studies, between 16 to 20% parent prosulfuron degraded over the 30-day duration of the 

study in sunlight exposed samples. However, most of the degradation is likely to come from 

microbial and/or abiotic hydrolysis degradation. The results of these studies indicated that 
59 

photolysis would contribute to the environmental degradation of prosulfuron although it is not 

anticipated to be a dominant mechanism. The degradation pathway was not provided in the 

studies. 

Four studies have been submitted and found acceptable performed in two different soils for 

aerobic soil metabolism. The first two studies were conducted using the Huntington series (sandy 

loam) with pH of 6.6, 1.17 %OC (MRIDs: 42685250 and 42685251 for triazine- and phenyllabeled studies, respectively). In the triazine study, prosulfuron degradated with an initial halflife of 152.0 days (calculated from 0 to 123 DAT by the registrant) and secondary half-life of 

279.7 (calculated from 123 to 364 DAT by the registrant). Including all the data points (0 to 364 

days) the half-life of prosulfuron was 211 days. Prosulfuron was 98.6-100.8% of the applied 

radioactivity immediately after treatment, 54.1-60.7% at 4 months, 49.1-53.5% at 6 months, 

39.2-39.2% at 9 months and 26.7-36.7% at 12 months. Three degradates were identified in the 

soils: CGA-150829, CGA-300406 and CGA-325025 with a maximum applied radioactivity of 

11.9 %, 10.4% and 21.6% at 12 months, respectively. At the end of the study CO2 totaled 3.1-

3.5% of the applied radioactivity and other volatiles totaled <0.4%. 

In the phenyl ring labeled from the Huntington series prosulfuron degraded with an initial 

registrant-calculated half-life of 69.7 days (regression from Day 0-Day 62) and a secondary halflife of 155 days (regression from Day 62-Day 365). In addition, all the data was included in the 

regression for a half-life of 121.1 days (although some evidence of two compartment model 

degradation was observed). Prosulfuron was 100.6-130.6% of the applied immediately posttreatment, 57.4-58.7% at 2 months, 46.2-49.6% at 3 months, 25.6-30.9% at 9 months and 14.6-

15.1% at 12 months. Trace amounts of a compound tentatively identified as CGA-352025 were 

also isolated. At the end of the study CO2 totaled 1.4-2.0% of the applied radioactivity and other 

volatiles totaled ≤0.1%. The degradates found in this study were CGA-159902 to a maximum of 

49% and CGA-300406 with 7.1%. Two unknown peaks were reported. Peak “A” which 

comprised up to 14.6% of the applied radioactivity was determined to consist of to 4 compounds; 

none present at >6.2% of the applied and the other unknown peak did not generate more than 

1.5% of the applied radioactivity at the end of the study. 

 

The registrant conducted two new studies with Kickapoo series at pH 6.1, 1.49 %OC (MRIDs: 

43387712 and 43387713, triazine- and phenyl-labeled studies, respectively) in an attempt to 

elucidate the discrepancy in half-lives from the Huntington series studies aforementioned. In the 

triazine labeled study, prosulfuron contained an initial half-life of 112.2 (regression from Day 0-

Day 123) and a secondary half-life of 159.7 days (regression from Day 123-Day 364). Using all 

the data points for the regression the half-life obtained was 138.3 days and showed fair first order 

fit with some evidence of two-compartment model degradation. Prosulfuron was 101.8%-

103.2% of the applied radioactivity immediately post treatment, 56.9-61.6% at 3 months, 45.3-

47.9% at 4 months, 20.5-20.4 at 9 months and 16.9-18.4% at 12 months. Five degradates were 

identified in the soil: CGA-150829 (31%), CGA-300406 (3.8%), CGA-325025 (≤0.2%), CGA325028 (2.6%) and G-28533 (≤4.4%). At the end of the study CO2 totaled 9.6% of the applied 

and other volatiles totaled <0.2%. 

In the phenyl labeled study, the initial registrant-calculated half-life of 138.4 days and a 

secondary half-life of 539.1 days for the parent. The regression with all the data points generated 
60 

a half-life of 154.6 days. Prosulfuron was 97.6-99.5% of the applied radioactivity immediately 

posttreatment, 52.5-59.2% at 4 months, 40.2-40.3% at 6 months, 22.0-24.9% at 9 months and 

20.5-21.2% at 12 months. Five degradates were identified in this study: CGA-159902 (47.8%), 

CGA-300406 (<0.6%), CGA- 325025 (5%), CGA-325027 (2.5%) and CGA-325028 (1.9%). At 

the end of the study the CO2 totaled 0.5% of the applied radioactivity and other volatiles totaled 

< 0.2%. 

 These discrepancies in half-lives can be attributed to the poor use of first order kinetics (by the 

registrant) using a “biphasic” first order model. In this analysis, we reported the best fit of the 

single first order and calculating the 90th percentile of the mean of the half-lives which resulted 

in a half-life of 188 days for prosulfuron. However, there was some evidence of twocompartment adsorption resulting in some modest increase in persistence (relative to the first 

order kinetics model) over the 365-days study period (USEPA 2006). In all aerobic soil 

metabolism studies the major degradates were CGA-150829 and CGA-159902, which increased 

with time and reached above 30% of the applied after 12 months incubation (See Figure A6 for 

aerobic degradation pathway). Formation of volatile degradates was negligible. 

Figure A6. Aerobic Soil Degradation Pathway of Prosulfuron (adapted from MRIDs: 

43387713), page 2.25. 

The studies submitted for anaerobic soil metabolism for the triazine and phenyl labeled were 

performed using the Huntington (MRIDs: 42685252 and 42685253, respectively) and Kickapoo 

(MRIDs: 43387714 and 43387715) series. Sandy loam of the Huntington was used with a pH of 

6.6 and 1.17%OC. In the triazine labeled study, prosulfuron degraded with a half-life of 123.4 

days that was incubated for 60 days under anaerobic conditions (nitrogen gas) following 30 days 

of incubation under aerobic conditions. Prosulfuron was 98.6-100% of the applied radioactivity 

immediately posttreatment, 86.5-88.7% at 30 days, 70.2-73.0% at 61 days and 53.6-67.7% at 90 

days. Three degradates were identified in the soil CGA-150829 (8.3%), CGA-300406 (9.1%) and 
61 

CGA-325025 (25.3%). Volatiles totaled ~ 0.4% of the applied radioactivity (0.3% CO2 and 

others <0.1%). The phenyl labeled study, prosulfuron degraded with a half-life of 89.0 days. 

Prosulfuron was 100.6-130.6% of the applied immediately posttreatment, 74.8-75.5 at 31 days, 

58.7-59.5% at 62 days and 53.5-59.6% at 92 days. Two degradates were identified in the soils: 

CGA-159902 (22.4%) and CGA-300406 (8.3%). At the end of the study the CO2 totaled 3.5% 

and other volatiles totaled <0.4%. 

Similarly, sandy loam of the Kickapoo was used with a pH of 6.1 and 1.49%OC. In the triazine 

study, prosulfuron degradated with a half-life of 137.9 days. Parent compound was 101.8-

103.2% of the applied immediately after treatment, 78.9-82.3% at 30 days, 71.9-73.2% at 60 

days and 64.1-64.3% at 90 days. Four degradates were identified in this study: CGA-150829 

with 8.6% of the applied radioactivity at 90 days, CGA-300406 (4.6%), CGA-325025 (10%) and 

G-28533 with (1.5%). The total amount of volatiles was 0.6% (CO2~ 0.4% and other <0.2%). 

The studies using the phenyl ring labeled prosulfuron generated a half-life of 136.8 days. 

Prosulfuron was 97.9-99.5% of the applied radioactivity immediately after treatment, 83.2-

85.7% at 30 days, 76.5-77.8 at 59 days and 60.462.4% at 90 days. Four degradates were 

identified in the soils (applied radioactivity at 90 days): CGA-159902 (7.5%), CGA300406 

(4.1%), CGA-325025 (18.3%) and CGA-325027 (1.6%). At the end of the study CO2 totaled 

0.3% and other volatiles totaled 0.1%. 

 

The average of the four soils resulted in a half-life of 121.8 days for the parent compound. 

Mineralization in these studies was minimal. In addition, samples from these studies were 

storaged at 4 °C for 18 months for re-analyses (the 90 days samples) and found that no 

significant degradation occurred during storage. 

On the other hand, the aerobic and anaerobic aquatic metabolism studies show shorter half-lives 

than those from the soil metabolism studies indicating the important role that abiotic hydrolysis 

plays in the degradation of prosulfuron as discussed below. 

The anaerobic aquatic metabolism studies were conducted using flooded silt loam sediment 

obtained from a pond in Fayette County, Kentucky; incubated in the dark at 24-26 °C for 12 

months (pH 7.0). Radioactivity partitioned predominantly into the aqueous phase, but 

partitioning into the sediment phase increased with time. In the triazine ring labeled study 

(MRID: 43387716), prosulfuron degraded (in a biphasic pattern) with an initial half-life of 13.3 

days (regression from 0-30 days), a secondary half-life of 25.8 days (regression from 30-120 

days) and a monophasic degradation of 16.4 days (regression from 0-365 days). Prosulfuron was 

95.3-98.9% of the applied immediately after treatment, 74.1-77.2% at 7 days, 46.6-53.3% at 14 

days, 16.4-17.8% at one month, 6.1-9.5% at two months, and between ≤2.2% between 3-12 

months. Seven degradates were identified primarily occurring in the water phase (applied 

radioactivity at 12 months): G-28533 (24.3%), CGA-188838 (9.6%), CGA-150829 (18.6%), 

NANC-CGA-159902 (2.9%), CGA-325028 (26.9%), CGA-300406 (undetected after 4 months), 

and CGA-325030 (≤0.2%). At the 12 months treatment, CO2 totaled 4.4% of the applied and 

other volatiles totaled <03%. The ratio of total prosulfuron residues in the water and sediment 

was approximately 1:1 at 12 months. 
62 

In the phenyl study, (MRID: 43387717) prosulfuron degraded with an initial half-life of 20.1 

days (regression from 0-30 days), secondary half-life of 20.1 days (regression from 30-120), a 

monobasic half-life of 17.2 days (regression from 0-364 days). Prosulfuron was 96.0-97.3% of 

the applied immediately post-treatment, 68.4-69.9% at 7 days, 46.0-52.2% at 14 days, 16.4-

20.7% at one month, 5.1-8.6% at two months, and ≤1.2% between 3 and 12 months. Seven 

degradates were identified in the sediments (applied radioactivity at 364 days): NANC-CGA159902 (<2.9%), CGA-325030 (≤0.7%), CGA-325028 (27.8%), CGA-325027 (4.5%), CGA325026 (4.9%), CGA-300406 (<0.8%) and CGA-159902 (58.6%). At 12 months post-treatment 

CO2 totaled <0.1% of the applied and others volatiles ranged from 0.4 to 3.1%. The ratio of total 

residues in the water and sediment was approximately 6:1 at 9 and 12 months. 

Total prosulfuron was less than 2% of the applied by 12 months. Prosulfuron degraded in a 

biphasic pattern with average half-life of 13.5 days for the primary (90th percentile 13.9 days) 

and a secondary half-life of 23.0 days (a 90th percentile of 31.7 days). A monophasic degradation 

calculation produced an average half-life of 16.8 days (90th percentile of 18.0 days). The 

aforementioned half-lives were calculated by the registrant however, in the last DWA (USEPA 

2006), more conservative estimation method was used (treating the two studies as one) and the 

half-life reported was 52.5 days (based upon the 3x mean half-life for two studies using one 

sediment source). The 90th percentile upper confidence interval of the mean half-life of the two 

studies (phenyl- and triazine-labeled) prosulfuron applied in separate studies for pond sediment 

taken from Fayette Co. KY) was 20.1 days (regression was done from 0-182 days, after the 

DT50 was apparent). Therefore, more conservative estimation method treating these studies as 

one study (EFED was not sure that this sediment gave typical results given the fact that the 

anaerobic soil metabolism half-lives were significantly longer in a different rest soil/sediment). 

The proposed degradation pathway of prosulfuron in sediment under anaerobic aquatic 

conditions is shown in Figure A7. The degradation shown in Figure A7 was a combination of 

the two radiolabeled studies performed on prosulfuron (MRIDs: 43387717 and 43387716). The 

degradate NANC-CGA-159902 was first detected in this study and a tentative structure was 

assigned to it. The registrant has indicated that they will be conducting a batch equilibrium 

(adsorption/desorption study) with the degradate tentatively identified as NANC-159902 once 

this chemical species is synthesized and fully characterized, however, no more studies for this 

chemical has been submitted. No more studies have been submitted regarding this degradate. 

Refer to Table A4 for more information about transformation products. 
63 

Figure A7. Anaerobic Aquatic Metabolism Degradation Pathway of Prosulfuron (adapted 

from MRIDs: 43387717 (phenyl label) and 43387716 (triazine label), page 6.27 and 5.26, 

respectively). 

The aerobic aquatic metabolism studies were conducted using phenyl and triazine labeled 

prosulfuron (MRIDs: 43387718 and 43387719, respectively). Although prosulfuron is not 

intended for aquatic uses, the registrant conducted these studies in support of the petitioned 

terrestrial use. Parent prosulfuron applied to loam/water sediment (pH 6.5-7.7) declined from 

100% to 69-83% of the applied radioactivity after 30 day incubation in the flooded system. Total 

radioactivity partitioned predominantly into the water phase. The half-lives found in the studies 

were 59.5 and 68.4 days for triazine and phenyl labels, respectively. The average half-life was 64 

days and the 90th percentile was 77.6 days. However, it is uncertain if first order kinetics it’s a 

good fit for the data since appeared that studies have a short duration time with few samples that 

resulted to accurately calculate persistence for subset time periods. A more conservative value 

was reported in the last DWA (USEPA, 2006) that both studies were treated as one study (halflife= 3x the half-life value). Three degradates were identified in the studies were CGA-300406, 

CGA-150829 and CGA-159902 but none of them were major degradates (Refer to Table A4). 

All of the column leaching studies submitted are acceptable. In the unaged study, greater than 

86% of the radioactivity was found in the leachate as parent prosulfuron, except in the silty clay 

loam column (54%). However, when prosulfuron was aged aerobically for 30-days with the 

incubated soil placed on top of the columns a significant reduction in the amount of radioactivity 
64 

(in terms of parent prosulfuron) was recovered in the leachates. This reduction was observed for 

both the triazine (MRID:42685255) and the phenyl (MRID:42685256) labeled aged prosulfuron. 

Moreover, a significant increase in parent prosulfuron was observed in the 0 to 6 inches depths in 

all cases when compared with the amount of prosulfuron in the same depth in the unaged study. 

Below the 6 inch depth, parent prosulfuron was essentially equally distributed in all segments. 

Although the appearance of parent prosulfuron in the leachates decreased upon aging, the 

amount of parent prosulfuron present in the leachates was still significant (34 to 57%). The 

bridge-cleavage degradates CGA-159902 and CGA-150829 were also present in the leachates 

(maximum of 3.35% CGA-159902 in the loamy sand column with CGA-300406 less than 2% of 

the applied radioactivity). 

The batch equilibrium adsorption/desorption studies were performed with the parent 

(prosulfuron, MRID: 42685257) and some degradates: CGA-159902, CGA-150829, CGA300406 and G-28533 (MRIDs: 43159329, 41656209, 43159330 and 43387720, respectively). 

Four soils coming from Fayette County were utilized. The texture, soil characteristics and soils 

series names are included in the appendix. The adsorption/desorption values are summarized on 

Appendix A1. The adsorption/desorption data in Appendix A1 are expressed in terms of 

Freundlich sorption constants. 

In all the four studies parent prosulfuron and its degradates adsorbed weakly. However, 

desorption data suggest that adsorption may be irreversible and that, once adsorbed, the tendency 

to desorbs may decrease. 

For prosulfuron, the amount adsorbed ranged between 3.8 and 21.5% and the percent desorbed 

ranged between 7.6 and 46.5% of the amount that had been adsorbed. The adsorption/desorption 

coefficients (Kd values) for triazine labeled were determined to be 0.074/1.146 for loamy sand, 

0.273/1.777 for sandy loam, 0.293/7.953 for silt loam and 0.2519/2.377 for silty clay loam. 

The organic carbon adsorption/desorption coefficients (Koc values) were determined to be 

17.60/272.79 for loamy sand, 15.25/99.25 for sandy loam, 18.56/503.34 for silt loam and 

41.30/389.62 for silty clay loam. 

Based on the use of Koc values to predict leaching potential where Koc values greater than 5,000 

denote immobility of a chemical in soil and Koc values between 0 to 50 denote mobility in soil, 

prosulfuron is predicted to have mobility in each of the four soil types. This mobility was also 

evident with the degradates studied. 

The degradate G-28533 adsorbed weakly and desorbed readily (reversible 

adsorption/desorption). However, irreversibility between adsorption/desorption was also noted 

with the degradates CGA-159902 and CGA-300406, although in both cases adsorption was 

weak. For CGA-300406 irreversible adsorption was noted in the loamy sand soil as well as for 

CGA-150829. Adsorption and desorption was linear for all degradates except for CGA-300406 

in loamy sand soil where n was equal or below 0.8 (n= 1/slope of the linear regression). For more 

information about the adsorption/desorption values for the degradates see Appendix A1. 

Both the batch equilibrium adsorption/desorption studies and the soil column leaching studies 

suggest that parent prosulfuron somewhat irreversibly adsorbs to soils (that is, once adsorbed it 
65 

does not desorbs readily). However, since current adsorption/desorption studies are not designed 

to study the kinetics of adsorption/desorption, there is no information or, the rate at which 

prosulfuron adsorbs to (or desorbs from) soils. Additionally, Freundlich adsorption constants for 

parent prosulfuron (all below 1 in four different soils) and the appearance of high amounts of 

prosulfuron in leachates in soil column leaching studies with unaged prosulfuron indicates a high 

potential for leaching for prosulfuron. However, the Freundlich desorption constants are much 

higher than the corresponding adsorption constants, suggesting that adsorption/desorption is not 

a reversible process (MRID: 42685257). Finally, the mobility of the prosulfuron and CGA159902 decreased with increasing soil organic matter content. 

Four studies were conducted for terrestrial field dissipation. Two of the studies were 14C-labelled 

studies conducted in Kentucky (MRID: 43387724) and in North Carolina (MRID: 43387725). 

The other two studies were "cold" studies conducted with and without corn crop; one of the 

studies was conducted in Iowa (MRIDs: 43159331 and 43387721) and the other in Georgia 

(MRIDs: 43159332 and 4338772). 

In the studies, residues were primarily concentrated in the 0 to 6 inch depth, with sporadic 

movement to the 6 to 12 inches. No residues were detected below 12 inches in any of the sites at 

any sampling time. In the Iowa study, the soil used was flager sandy loam pH 5.4 and 1.3%OC. 

Total prosulfuron residues were sporadically detected in the 6 to 12 inch soil depth at up to 1.1 

ppb; prosulfuron residues were not detected (<0.50 ppb) in soils collected from below the 12 

inches depth. The half-life for the monophasic was 10.2 and 19.3 days for the bare ground and 

corn, respectively (0 to 6 inches). Biphasic half-lives were 6.2 and 7.8 days for the primary and 

31.5 and 43.3 days for the secondary for the bare ground and corn, respectively. No residues of 

parent prosulfuron were found into the 6 to 15 inch depth. 

The degradate moving to the 6 to 12 inches depth was CGA-300406 during the first to second 

week. While formation of this degradate increased in the 0 to 6 inch depth during the earlier part 

of the study, it declined to non-detectable levels after one month; a decline in this degradate 

usually reflected an increase in the amount of degradates CGA-159902 and CGA-150829. The 

degradate CGA-159902 was only detected in the 6-12 inches depth (at 0.6 ppb) at 302 and 358 

post-treatment of the bare ground and corn studies, respectively and again at 496 day (bare 

ground). Parent prosulfuron declined from 13 to 7 ppb at day zero to 3 to 4 ppb at 14 days, to 

0.86 ppb by 45 days, to undetectable levels at 358 days. 

In the more porous, less acidic, low organic matter content of Georgia site (Fuquay loamy sand 

series, pH 7.3, 0.52% OC) the movement of parent prosulfuron to the 6 to 12 inches depth was 

observed in samples collected at 3, 7, 14, 21, and 30 days (corn) at 1, 3, 7, 14, 44 21, 30, 45, 60, 

90, and 120 days (bare ground). The half-life for the monophasic was 10.3 and 8.8 days for the 

bare ground and corn, respectively (0 to 6 inches). Biphasic half-lives were 4.1 and 4.2 days for 

the primary and 15.0 and 13.9 days for the secondary for the bare ground and corn, respectively. 

The degradates CGA-300406, CGA-159902, and CGA-150829 were predominantly located in 

the 0 to 6 inches depth. The only movement of degradates to the 6 to 12 inches depth was with 

CGA- 300406 at 7 days (corn) and 21 days (bare ground), CGA-159902 and CGA-150829 at 436 

days (corn). Parent prosulfuron declined from 13 to 15 ppb by day 45, to undetectable levels by 

360 days. 
66 

In addition, two radiolabeled studies were submitted, one of the studies (MRIDs: 43387724; 

43387726 (storage stability) was conducted in Kentucky (KY); the other study (MRIDs: 

43387725; 43387727 (storage stability) was conducted in North Carolina (NC) for 365 days (See 

Appendix A2). 

The soil at the KY site (0-3 inches depth) was characterized as silty clay loam (18% sand, 54% 

silt, 28% clay, 1.9 % OC and pH 5.68). Considerable radioactivity was detected in the overflow 

water of the KY study (6.7 to 39%), which was associated with the heavy rainfall events. 

Prosulfuron and degradates (CGA-159902, CGA-150829, CGA-300406 and NANC-CGA159902) were detected in the overflow water at various concentrations during the course of the 

study. However, most of the radioactivity was confined to the 0 to 3 inches top layer, with slow 

movement to the 3 to 6 inches and only sporadic movement to the 6 to 9 inches depth. This 

suggests that soil characteristics coupled with site topology and heavy rainfall events following 

application may lead to run-off. On the other hand, there is evidence that prosulfuron appears to 

adsorb irreversibly to soils, which may cause prosulfuron to move off-target with eroded soil 

particulates prior to degradation. 

Total residues recovered in the entire length (36 inches) of the soil column treated with phenyl 

ring labeled prosulfuron were 84.9-101.6% of the applied through 7 DAT, 43.9-73.5% between 

15 and 91 DAT and 33.8-49.2% between 182 and 365 DAT. No overflow or surface water was 

recovered prior to 15 DAT. Residues recovered in the overflow water after 15 days ranged from 

10.9 to 39% of the applied radioactivity and residues recovered in the surface water after 15 days 

were ≤6.86%. At 365 DAT accumulated residues in the column leachates totaled 0.11-0.40% of 

the applied. 

The triazine labeled study resulted in total residues (entire length of the soil column) of 95.5-

110% of the applied radioactivity through 7 DAT (with the exception of one lysimeter collected 

at 3 DAT); 57.1-72.6% between 15 and 91 days, and 36.4-50.1% at 365 DAT. No overflow or 

surface water was recovered prior to 15 DAT; the residues recovered in the flow water after 15 

DAT ranged from 6.68 to 34.9% of the applied radioactivity and residues were ≤6.01% of the 

applied radioactivity. At 365 DAT accumulated residues in the column leachates totaled 0% of 

the applied radioactivity. 

Prosulfuron and its degradates were shown to be stable in water during frozen storage conditions. 

Aliquots of the overflow water from control lysimeters were treated with phenyl label 

prosulfuron, CGA-300406 and CGA-159902 or with triazine ring labeled prosulfuron and CGA150829. The treated samples were stored frozen (-20°C) for up to 422 days and then analyzed by 

HPLC. The relative concentrations in the water remained unchanged during storage. 

In the North Carolina study, total radioactivity in the leachates averaged 5.3 ppb or 0.26% of the 

applied radioactivity in lysimeters remaining in the ground for one year. The half-lives of 

prosulfuron in the phenyl and triazine studies (reported by the registrant) were: 5.7 and 7.3 days 

respectively. The total residues half-lives were 10-10.6 and secondary half-lives of 258 and 299 

days for the phenyl and the triazine label studies, respectively. Parent prosulfuron was not 

detected in the leachates, except in two lysimeters after 13 days. Five degradates were isolated 
67 

from the soil: CGA-300406, CGA-NANC-159902, CGA-159906, CGA-150829 (phenyl labeled 

study only) and CGA-273437 (phenyl labeled study only).The degradates CGA-159902, CGA150829, CGA-300406 were detected in the leachate, of which CGA-159902 had the highest 

detection (2.44 ppb or 0.28% of the dose) by day 63. In the top 0 to 3 inches layer, the degradates 

CGA-159902, CGA-150829, CGA-300406 and NANC-CGA-159902 together with parent, were 

detected. The amount of parent decreased with time. 

Total residues recovered in the entire length (36 inches) of the soil column treated with phenyl 

labeled prosulfuron were 91.5-113% of the applied through 3 DAT; 68.5-77.4% at 14 through 56 

DAT and 44.8-57.9% at 278 and 365 DAT. No surface water was recovered during the study. At 

365 DAT accumulated residues in the column leachates totaled 2.7-7.5% of the applied. 

Residues in the leachates consisted of prosulfuron, CGA-300406, CGA-159902, CGA 325028, 

NANC-CGA-159902, and three unidentified compounds. 

Similarly, total residues recovered in the entire length of the soil column treated with triazine 

ring-labeled prosulfuron were 84.2-104.7% of the applied radioactivity through 3 DAT, 70.8-

87.7 between 8 and 56 DAT; 58.9-75.0% between 91 and 278 DAT and 53.5-60% at 365 DAT. 

Surface water was recovered once, at 1.27% of the applied radioactivity in one sample at 14 

DAT. At 365 DAT accumulated residues in the column leachates were composed of prosulfuron 

CGA-300406, NANC-CGA-159902 and two unidentified compounds. 

As in the study performed with KY soil, prosulfuron and its degradates have been shown to be 

relatively stable in frozen soil in NC with no evidence of degradation of prosulfuron or its 

degradates during storage (283 days). Figure A8 show the field metabolism pathway for 

prosulfuron. 
68 

Figure A8: Field Metabolism Pathway for CGA-152005, adapted from USEPA, 1995. 

The laboratory data suggest that, like most sulfonylurea (SU) herbicides, prosulfuron could be 

persistent and mobile. Degradation is dependent on pH, with neutral and alkaline media favoring 

persistence. Photolysis is not an important degradative route for prosulfuron. The long aerobic 

soil metabolism half-lives are in contrast with the much shorter dissipation half-lives observed 

under field conditions. In addition, the shorter half-lives observed under anaerobic and aerobic 

aquatic metabolism studies are indicative of the important role that abiotic hydrolysis plays in the 

degradation of prosulfuron. Therefore, prosulfuron would be expected to degrade/dissipate more 

rapidly in areas where irrigation and/or rainfall is common. On the other hand, in drier areas 

(particularly in areas of cool weather) prosulfuron is likely to degrade at a slower rate. Parent 

prosulfuron and its major degradates do not bind strongly to soils, but appear to bind irreversibly. 

Adsorption appears to increase with time, but no data on adsorption/desorption kinetics are 

available to support this observation. The low vapor pressure and high water solubility of 

prosulfuron makes it unlikely for prosulfuron to dissipate from soil and/or from water by direct 

volatilization. The major degradates of prosulfuron are those formed primarily by cleavage of the 

sulfonylurea bridge, but the desmethyl analogue is also a common degradate. Degradates formed 

by opening of the triazine ring have been identified in laboratory studies and in the field. 

The rate of prosulfuron degradation/dissipation would be influenced by the characteristics of the 

use area, with cold temperature and dry climates increasing the persistence of prosulfuron. The 

soil characteristics (well drained versus poorly drained), the topology of the site and its 
69 

hydrological characteristics are needed when evaluating the environmental impact of prosulfuron 

at specific sites. 

The low octanol water partition coefficient of prosulfuron makes it unlikely to bioaccumulate in 

fish. The octanol/water partition coefficient decreases with increasing pH and parallels the 

increase water solubility in going from acidic to alkaline pHs. Although prosulfuron is relatively 

stable to abiotic hydrolysis at neutral and alkaline pHs, biotic degradation in aqueous media 

contributes to reduce the amount of prosulfuron available for bioaccumulation. The major 

degradates of prosulfuron are also very soluble in water and are not likely to bioaccumulate. 

Table A4 shows the maximum amount of applied radioactivity observed for each identified 

transformation product. Many of the maximums were observed at the final sampling interval 

with few unknowns and unextracted residues may have been found, so it is likely that some of 

these maximum percentages would slightly increase. In the dissipation studies in soil conducted 

in KY and NC four degradates were found: CGA-159902, CGA-300406, NAC-CGA-159902 

and CGA-150829. 
70 

Appendix B. Summary of available effects studies 

Aquatic Organisms 

Table B1 contains all available aquatic toxicity endpoints from registrant-submitted studies. The 

most sensitive endpoints that will be used in quantitative risk assessment are highlighted in bold. 

Below is a brief summary of available aquatic toxicity studies. 

Fish

A 96-hour acute toxicity study (MRID 426852-09) was also carried out with the bluegill sunfish 

(Lepomis macrochirus) at a limit concentration of 155 mg ai/L (mean measured) of prosulfuron 

technical. No mortality or sublethal effects were observed in either the control or treatment 

groups resulting in an LC50 of >155 mg ai/L. Therefore, prosulfuron is considered practically 

nontoxic to bluegill sunfish on an acute exposure basis. 

A 96-hour acute toxicity study (MRID 426852-10) was also carried out with the rainbow trout 

(Oncorhynchus mykiss) at a limit concentration of 160 mg ai/L (mean measured) of prosulfuron 

technical. No mortality or sublethal effects were observed in either the control or treatment 

groups resulting in an LC50 of >160 mg ai/L. Therefore, prosulfuron is considered practically 

nontoxic to rainbow trout on an acute exposure basis. 

In a 96-hour acute toxicity limit test (MRID 429497-06) with the sheepshead minnow 

(Cyprinodon variegatus), no mortality or sublethal effects resulted from exposure to prosulfuron 

technical. Since the limit concentration was 155 mg ai/L, the LC50 for this study is >155 mg ai/L. 

Therefore, prosulfuron is considered practically non-toxic to the sheepshead minnow on an acute 

exposure basis. 

A 37-day early life-stage toxicity test (MRID 429497-07) was conducted with fathead minnows 

(Pimephales promelas) at mean-measured prosulfuron concentrations of 21.1, 35.8, 58.8, 84.9, 

and 149.1 mg ai/L. No significant differences were observed between control and exposure 

concentrations for any endpoint (survival, hatchability, length, wet and dry weight). Therefore, 

the NOAEC for the fathead minnow was 149.1 mg ai/L. It should be noted that the test was 

extended from 36 to 37 days because of a diluter control malfunction on day 28 that may have 

affected test substance concentration values during that portion of the experiment. 

Crustaceans

A 48-hour acute toxicity study (MRID 426852-11) was carried out with the freshwater 

crustacean Daphnia magna at a limit concentration of 120 mg ai/L. No mortality or sublethal 

effects were observed in either the control or treatment groups resulting in an LC50 of >120 mg 

ai/L. Therefore, prosulfuron is considered practically non-toxic to D. magna on an acute 

exposure basis. 

A 96-hour acute toxicity study (MRID 432126-01) was conducted with a saltwater mysid species 

(Americamysis bahia) at a limit concentration of 150 mg ai/L. There were seven mortalities as 
71 

well as four individuals exhibiting lethargy in the group treated with prosulfuron. Since less than 

50% mortality was observed in the treatment group, the LC50 for this study is >150 mg ai/L. 

Therefore, prosulfuron is considered practically non-toxic to A. bahia on an acute exposure basis. 

A 21-day chronic toxicity test (MRID 429497-08) was performed with D. magna at mean 

measured concentrations of 18, 33, 56, 86, and 148 mg ai/L. No statistically significant 

difference in any measured endpoint (adult survival, number of young per reproductive day, 

pooled dry weight per replicate) occurred at any treatment level as compared to the control 

group. Therefore, the NOAEC for this study is the highest concentration tests, i.e., 148 mg ai/L 

Mollusks

In a 96-hour shell deposition study (MRID 432126-02) with the eastern oyster (Crassostrea 

virginica), no mortality or statistically significant effects on shell deposition were recorded at the 

limit concentration of 125 mg ai/L, resulting in an EC50 of >125 mg ai/L. Therefore, prosulfuron 

is considered practically non-toxic to C. virginica on an acute exposure basis. 

Vascular Plants

A 14-day tier II growth and reproduction test (MRID 429497-13) with the aquatic vascular plant 

species Lemna gibba was performed at mean-measured concentrations of 0.210, 0.407, 0.827, 

1.70 and 3.40 μg ai/L of prosulfuron technical. In the three lowest treatment groups, slight 

stimulation of frond production was observed (6-9%), while at the two highest treatment levels, 

marked inhibition of frond production of 84% (1.70 μg ai/L) and 97% (3.40 μg ai/L) was 

reported. The NOAEC and EC50 for this study is 0.83 and 1.22 μg ai/L, respectively. 

Nonvascular Plants

A 5-day tier II aquatic nonvascular plant toxicity study (MRID 429497-14) was carried out with 

the green alga Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) at 

prosulfuron mean-measured concentrations of 1.17, 2.78, 4.84, 10.3, and 19.5 μg ai/L. Exposure 

to concentrations ≥4.84 μg ai/L had significant inhibitory effects on alga; cell density resulting in 

a NOAEC of 2.78 μg ai/L. The 5-day EC50 for this study is 10.6 μg ai/L (95% CI: 8.84-12.7 μg 

ai/L). 

Another 5-day tier II aquatic nonvascular plant toxicity study (MRID 429497-15) was carried out 

with the freshwater diatom Navicula pelliculosa at prosulfuron mean-measured concentrations of 

6.25, 12.6, 23.0, 46.4, and 83.6 μg ai/L. Exposure to concentrations ≤23.0 μg ai/L had a 

significant stimulatory effect on cell density, while exposure to the two highest concentrations 

was slight inhibitory (but not statistically significant). Therefore the NOAEC for this study is 

83.6 μg ai/L. The 5-day EC50 for this study was determined to be greater than the highest 

concentration tested (i.e., >83.6 μg ai/L). It should be noted that variance in the study data was 

high. At the highest test level (83.6 μg ai/L), the mean and standard deviation in cell density was 

597,750 and 332,000 cells/mL, respectively. At the second highest test level (46.4 μg ai/L), the 

mean and standard deviation in cell density was 576,000 and 582,000 cells/mL, respectively. 

Therefore, even large reductions were not statistically discernable. Consequently, this study is 
72 

downgraded to supplemental and will not be used quantitatively in risk assessment. 

Two tier I aquatic nonvascular plant toxicity studies (MRIDs 429497-11; 429497-12) were 

carried out with the cyanobacterium Anabaena flos-aquae and the marine diatom Skeletonema 

costatum at limit concentrations of 27.2 and 28.6 μg ai/L, respectively. 5-day cell density was 

significantly reduced by 22.5% in prosulfuron treated A. flos-aquae cultures as compared to 

controls, while mean cell density in S. costatum was slightly elevated at the limit concentration 

as compared to controls. Since less than 50% mortality was observed during both tests, the EC50

value is greater than the limit concentration. 

Table B1. Aquatic Toxicity Profile for Prosulfuron 

Species Measured 

Effect Duration Endpoint Toxicity Value μg ai/L 

Test 

Substance 

% ai 

MRID 

(Study 

Classification) 

Freshwater Fish 

Lepomis 

macrochirus 

(Bluegill sunifsh) 

Mortality 96 hours LC50

>155,000†‡

(Practically 

non-toxic)

99.1% 426852-09 

(Acceptable) 

Oncorhynchus 

mykiss 

(Rainbow trout) 

Mortality 96 hours LC50

>160,000†‡

(Practically 

non-toxic) 

99.1% 426852-10 

(Acceptable) 

Pimephales 

promelas 

(Fathead Minnow) 

Growth, 

Survival, 

Hatchability 

37 days NOAEC 149,000* 99.1% 429497-07 

(Acceptable) 

Freshwater Crustaceans 

Daphnia magna 

(Water flea) 

Immobility 48 hours EC50

>120,000†‡

(Practically 

non-toxic) 

99.1 426852-11 

(Acceptable) 

Growth, 

Survival, 

Reproduction

21 days NOAEC 148,000* 99.1 429497-08 

(Acceptable) 

Estuarine/Marine Fish 

Cyprinodon 

variegatus 

(Sheepshead 

minnow) 

Mortality 96 hours LC50

>155,000†‡

(Practically 

non-toxic) 

99.1% 429497-06 

(Acceptable) 

Estuarine/Marine Crustaceans and Mollusks 

Americamysis bahia 

(Mysid shrimp) Mortality 96 hours LC50

>150,000†‡

(Practically 

non-toxic) 

99.1% 432126-01 

(Supplemental) 

 

Crassostrea 

virginica 

(Eastern oyster) 

Shell 

deposition 96 hours EC50

>125,000†‡

(Practically 

non-toxic) 

99.1% 432126-02 

(Acceptable) 

Aquatic Plants 

Lemna gibba 

(duckweed) Frond number 14 days EC50 1.22* 98.7% 429497-13 

NOAEC 0.83* (Acceptable) 

Pseudokirchneriella 

subcapitata 

(green algae) 

Tier II Study

Cell density 5 days 

EC50 10.6* 

98.7% 429497-14 

NOAEC 2.78* (Acceptable) 
73 

Species Measured 

Effect Duration Endpoint Toxicity Value μg ai/L 

Test 

Substance 

% ai 

MRID 

(Study 

Classification) 

Navicula pelliculosa 

(freshwater diatom) 

Tier II Study 

Cell density 5 days 

EC50 >83.6†

99.1% 429497-15 

NOAEC 83.6 (Supplemental) 

Anabaena 

flos-aquae 

(cyanobacterium) 

Tier I Study 

Cell density 5 days 

EC50 >27.2†‡

98.7% 429497-11 

NOAEC <27.2 (Acceptable) †‡

Skeletonema 

costatum 

(marine diatom) 

Tier I Study 

Cell density 5 days 

EC50 >28.6†‡

98.7% 429497-12 

NOAEC 28.6 (Acceptable) †‡

* Bold values represent most sensitive endpoint and will be used for risk estimation. 

†

 Non-definitive study endpoint; cannot be used for risk estimation. 

‡

 Single concentration limit test. 

Terrestrial Organisms 

Table B2 contains all available terrestrial toxicity endpoints from registrant-submitted studies. 

The most sensitive endpoints that will be used in quantitative risk assessment are highlighted in 

bold. Below is a brief summary of available terrestrial toxicity studies. 

Birds

A 14-day acute oral toxicity study (MRID 426852-05) with prosulfuron technical was conducted 

with mallard ducks (Anas platyrhynchos) at doses of 100, 215, 464, 1000, and 2150 mg ai/kgbw. Two mortalities occurred in the highest dosage group (2150 mg ai/kg-bw), while five 

mortalities occurred in the second highest dosage group (1000 mg ai/kg-bw). Since the pattern of 

mortality was not dose-responsive, an LD50 value of 1094 mg ai/kg-bw (95% CI: 943-1269 mg 

ai/kg-bw) was calculated by omitting the highest dosage group. This led to a lower (i.e., more 

conservative) endpoint value than if the highest dosage group was used in the analysis. 

Prosulfuron is classified as slightly toxic to mallard duck on an acute oral exposure basis. 

Clinical signs of toxicity noted during the study included lethargy and stumbling in the 464 mg 

ai/kg-bw group, lethargy in the 1000 mg ai/kg-bw group, and bloody excreta and lethargy in the 

highest dosage group (2150 mg ai/kg-bw). All surviving birds returned to normal by test day 4. 

Reduced feed consumption was noted in the four highest dosage groups during test days 1 

through 3. 

A 21-day acute oral toxicity study (MRID 426852-06) with prosulfuron technical was conducted 

with the bobwhite quail (Colinus virginianus) at doses of 1470 and 2150 mg ai/kg-bw. No 

mortalities occurred in the control or treatment groups; therefore the LD50 was determined to be 

>2150 mg ai/kg-bw. Prosulfuron is classified as practically nontoxic to bobwhite quail on an 

acute oral exposure basis. Clinical signs of toxicity noted during the study included ataxa, 

anorexia, and chalky diarrhea. Based on feed consumption data, anorexia was noted in the 1470 

mg ai/kg-bw dosage group and slightly reduced feed consumption was noted in the 2150 mg 

ai/kg-bw group. Out of a random subset of twelve birds selected for necropsy, one bird at the 
74 

1470 mg ai/kg-bw level had a friable liver. In the 2150 mg ai/kg-bw group, a growth was found 

attached to the gizzard of one male; one male had friable testis, and one female had resorbed 

eggs and a reddened enlarged liver. 

In an 8-day dietary toxicity study with the mallard duck (MRID 426852-07), dosage levels 

consisted of 312, 625, 1250, 2500, and 5000 mg ai/kg-diet. No mortality or abnormal behavior 

was observed in control or treatment groups and the dietary LC50 was determined to be >5000 

mg ai/kg-diet. Prosulfuron is classified as practically nontoxic to mallard duck on an acute 

dietary exposure basis. 

In an 8-day dietary toxicity study with the bobwhite quail (MRID 426852-08), dosage levels 

consisted of 312, 625, 1250, 2500, and 5000 mg ai/kg-diet. No mortality or abnormal behavior 

was observed in control or treatment groups and the dietary LC50 was determined to be >5000 

mg ai/kg-diet. Prosulfuron is classified as practically nontoxic to bobwhite quail on an acute 

dietary exposure basis. 

A chronic reproductive toxicity study (MRID 429497-01) was carried out with mallard ducks at 

prosulfuron dietary concentrations of 28, 100, and 350 mg ai/kg-diet (16 male and 16 female 

birds per treatment level). Birds were fed appropriate treated diet for 22 weeks followed by 

untreated feed during a three week recovery period. There were no treatment-related deaths or 

adverse behavioral signs recorded at any concentration throughout the study. There was a 

significant decrease in female body weight compared to control birds during week 22 of the test. 

There was a significant decrease in the number of eggs laid per hen at 350 mg ai/kg-diet 

compared to controls. There was a significant decrease in the number of 14-day-old survivors of 

eggs set at 100 mg ai/kg-bw, and a slight (but non-significant) decrease in hatchling survival at 

350 mg ai/kg-diet; effects at both test levels were considered to be treatment-related resulting in 

a study NOAEC of 28 mg ai/kg-diet. Reduced offspring survival was attributed to reduced 

hatching success rather than reduced hatchling survival rate. 

Mammals

A 14-day acute oral toxicity study (MRID 426852-15) was performed with Sprague Dawley rats 

at test substance doses ranging from 400 to 1,000 mg/kg. Clinical signs that were possibly 

compound related included dose-related increase in staggered gait, lacrimation in females, and 

hypersensitivity to touch and sound. The LD50 for this study was 546 mg/kg for female rats, 949 

mg/kg for males, and 986 mg/kg for combined sexes. 

A 3-month sub-chronic oral toxicity study (MRID 426852-32) was carried out in Sprague 

Dawley rats at dietary levels of 5, 50, 500, 4,000 and 8,000 mg/kg-diet. In male rats, body weight 

and body weight gain were reduced by 9 and 13% respectively at the 500 mg/kg-diet level, 

resulting in a study NOAEL of 50 mg/kg-diet (3.1 mg/kg/day). 

In a multi-generation reproduction study (MRID 431593-19) in rats, treatment groups received 

dietary concentrations of 10, 200, 2,000, or 4,000 mg/kg-diet of the test substance. At 2,000 and 

4,000 mg/kg-diet, parental mean body weights were significantly lower than controls, resulting 

in a parental (systemic) toxicity NOAEL of 200 mg/kg-diet. In the F1 and F2 offspring, pup 
75 

weights were also reduced at the same test concentrations as adults. Thus, the reproductive 

toxicity NOAEL was also 200 mg/kg-diet. 

Terrestrial Arthropods

A 48-hour acute contact toxicity test (MRID 426852-12) was conducted with 14-to-21-day-old 

honeybees at prosulfuron treatment concentrations of 6.25, 12.5, 25, 50 and 100 μg ai/bee. 

Prepared dosing solutions were applied to the dorsal thorax or abdomen of immobilized bees. 

Mortality in treatments groups and controls ranged from 0 to 2% and all deaths were attributed to 

handling. No sublethal effects were observed among treated bees. The LD50 value for honeybees 

is therefore greater than the highest concentration tested (>100 μg ai/bee). 

Terrestrial Plants

A 21-day tier II seedling emergence study (MRID 429747-01) was performed with prosulfuron 

technical on six species of dicotyledonous plants (soybean, lettuce, radish, tomato, cucumber, 

cabbage) and four species of monocotyledonous plants (corn, oat, ryegrass, onion) at application 

rates of 0.0025, 0.0050, 0.010, 0.020, and 0.040 lbs ai/A. A continuation study was also carried 

out at application rates of 0.00001 and 0.0025 lbs ai/A. Percent emergence, percent survival, 

phytotoxicity, plant height, and plant dry weight were evaluated. The most sensitive dicot species 

endpoint was dry weight for lettuce with corresponding EC25 and NOAEC values of 7.1 x 10-5

and 8.0 x 10-5 lbs ai/A, respectively. The most sensitive monocot species endpoint was plant 

height for onions with corresponding EC25 and NOAEC values of 2.6 x 10-4 and 1.6 x 10-4 lbs 

ai/A, respectively. 

A 21-day tier II vegetative vigor study (MRID 429497-10) was performed with prosulfuron 

technical on six species of dicotyledonous plants (soybean, lettuce, radish, tomato, cucumber, 

cabbage) and four species of monocotyledonous plants (corn, oat, ryegrass, onion) at application 

rates of 0.0025, 0.0050, 0.010, 0.020, and 0.040 lbs ai/A. A continuation study was also carried 

out at application rates of 7.8 x 10-5 and 0.0025 lbs ai/A. Percent survival, phytotoxicity, plant 

height, and plant dry weight were measured. The most sensitive dicot NOAEC was 1.6 x 10-4 lbs 

ai/A for soybean dry weight and phytoxicity index measure. The lowest dicot EC25 value was 4.6 

x 10-4 lbs ai/A for soybeans. The most sensitive monocot NOAEC was 3.1 x 10-4 lbs ai/A for 

onion dry weight and plant height. The lowest monocot EC25 value was 4.1 x 10-4 lbs ai/A for 

onions. 

A tier II seed germination phytotoxity test (MRID 429497-09) was carried out with prosulfuron 

technical on six species of dicotyledonous plants (soybean, lettuce, radish, tomato, cucumber, 

cabbage) and four species of monocotyledonous plants (corn, oat, ryegrass, onion). The test 

material was applied at rates of 0.0027, 0.0054, 0.011, 0.022, and 0.043 lbs ai/A and seed 

germination rates were measured. No significant differences in percent germination existed for 

any of the test species except for ryegrass, which demonstrated an 11% decrease in germination 

at the highest treatment level. Therefore, the NOAEC for ryegrass is 0.022 lbs ai/A, while the 

NOAEC for all other plant species is 0.043 lbs ai/A. Since less than 50% inhibition occurred for 

all plants and treatment groups, the EC25 is non-definitive and is estimated to be greater than the 
76 

highest concentration tested (i.e., >0.043 lbs ai/A). It should be noted that the 0.043 lbs ai/A is 

higher than the current maximum registered use rate of prosulfuron of 0.0356 lbs/A. 

Investigations/studies have indicated that a small percentage of the label application rate of low 

dose, high-potency herbicides such as prosulfuron may impact the reproduction of non-target 

terrestrial plants (Asghari and Evans, 1992a, 1992b; Bhatti et al., 1995; Boutin et al., 2000; 

Fletcher et al., 1993; Fletcher et al., 1996a, 1996b; Pfleeger et al., 2011). However, there are no 

available data on adverse reproductive impacts to terrestrial plants from prosulfuron residues due 

to spray drift. 

Table B2. Terrestrial Toxicity Profile for Prosulfuron 

Species Measured effect Endpoint Test 

Duration 

Toxicity Value 

(Acute Toxicity 

Category) 

Test 

Substance 

% ai 

MRID 

(Study 

Classification)

Birds

Anas 

platyrhynchos 

(mallard duck) 

Mortality LD50 14 days 1094 mg ai/kg-bw* 

(Slightly toxic) 99.2% 426852-05 (Acceptable) 

Mortality LC50 8 days >5000 mg ai/kg-diet†

(Practically non-toxic) 99.1% 426852-07 (Acceptable) 

Hatching success NOAEC 25 weeks 28 mg ai/kg-diet* 99.2% 429497-02 

(Acceptable) 

Colinus 

virginianus

(Northern 

Bobwhite 

Quail) 

Mortality LD50 21 days >2150 mg ai/kg-bw†

(Practically non-toxic) 99.1% 426852-06 (Acceptable) 

Mortality LC50 8-days >5000 mg ai/kg-diet†

(Practically non-toxic) 99.1% 426852-08 (Acceptable) 

Mammals

Rattus 

norvegicus 

(laboratory rat) 

Mortality LD50 14-days 546 mg/kg-bw* 

(females) 99.1% 

426852-15 

(Acceptable: 

Reviewed by HED) 

Body weight, body 

weight gain 

(subchronic feeding 

study) 

NOAEL 3 months 50 mg/kg-diet (males)* 

(3.1 mg/kg/day) 96% 

426852-32 

(Acceptable: 

Reviewed by HED) 

Parental weight, F1

and F2 pup weights NOAEL 

2-

generation 

test 

200 mg/kg-diet 

(13.3 mg/kg-day; adult 

males) 

99.1% 

431593-19 

(Acceptable: 

Reviewed by HED) 

Terrestrial Arthropods

Apis mellifera

(Honeybee) Mortality LD50 48 hours >100 μg ai/bee 99.1% 426852-12 

(Acceptable) 

Terrestrial Plants

Monocots 

(onion) Seedling 

emergence study: 

% emergence % 

survival; 

phytotoxicity; 

height; dry weight 

EC25

21 days 

0.00026 lbs ai/A 

99.1%

(TGAI) 

429747-01 

(Supplemental)‡

Monocots 

(onion) NOAEC 0.00016 lbs ai/A 

Dicots 

(lettuce) EC25 0.000071 lbs ai/A 

Dicots 

(lettuce) NOAEC 0.00008 lbs ai/A 

Monocots 

(onion) 

Vegetative vigor 

study: % survival; EC25 21 days 0.00041 lbs ai/A 99.1%

(TGAI) 

429497-10 

(Supplemental)‡
77 

Species Measured effect Endpoint Test 

Duration 

Toxicity Value 

(Acute Toxicity 

Category) 

Test 

Substance 

% ai 

MRID 

(Study 

Classification)

Monocots 

(onion) 

phytotoxicity; 

height; dry weight NOAEC 0.00031 lbs ai/A 

Dicots 

(soybean) EC25 0.00046 lbs ai/A 

Dicots 

(soybean) NOAEC 0.00016 lbs ai/A 

Monocots 

(multiple 

species) 

Seed germination 

study: % seed 

germination 

EC25

6 days 

>0.43 lbs ai/A 

99.1%

(TGAI)

429497-09 

(Acceptable) 

Monocots 

(ryegrass) NOAEC 0.022 lbs ai/A 

Dicots 

(multiple 

species) 

EC25 >0.43 lbs ai/A 

Dicots 

(multiple 

species) 

NOAEC 0.043 lbs ai/A 

* Bold values represent most sensitive endpoint and will be used for risk estimation. 

† Non-definitive study endpoint; cannot be used for risk estimation. 

‡

 Tier II plant studies recently downgraded to “supplemental” because they were not performed with TEP 
78 

Appendix C. Output from OPP Aggregate Incident Database for Prosulfuron 

Aggregate Incident Report for EFED

Prosulfuron

PC Code:129031

Total Count of Minor Incidents from Aggregated Reports

Minor Fish and Wildlife Incidents (W-B): 0

Minor Plant Incidents (P-B): 37

Minor "Other Nontarget" Incidents (ONT): 0

Date Range Package Seq # Product Sum W-B P-B ONT

11/1/1998 - 009573 052 EXCEED HERBICIDE 1 0 1 0

11/1/1998 - 009573 054 SPIRIT HERBICIDE 2 0 2 0

11/1/1999 - 010837 096 SPIRIT HERBICIDE 12 0 12 0

11/1/1999 - 010837 091 EXCEED HERBICIDE 2 0 2 0

11/1/1999 - 010837 094 PEAK HERBICIDE 2 0 2 0

11/1/2000 - 012499 091 SPIRIT 1 0 1 0

11/1/2001 - 013554 067 SPIRIT 1 0 1 0

11/1/2002 - 014597 057 SPIRIT 2 0 2 0

11/1/2003 - 015713 113 EXCEED 2 0 2 0

11/1/2004 - 016903 054 PEAK CUSTOM PAK 3 0 3 0

11/1/2004 - 016903 057 SPIRIT 2 0 2 0

11/1/2006 - 019130 103 SPIRIT 2 0 2 0

11/1/2007 - 020283 142 PEAK 4 0 4 0

11/1/2009 - 021500 088 SPIRIT 1 0 1 0
79 

Appendix D. STIR Results for Evaluate Potential for Inhalation Risk to Birds and 

Mammals 
80 

Appendix E. SIP Results for Evaluate Potential Risk to Birds and Mammals from Drinking 

Water Exposure. 
81 

Appendix F. Agency risk quotient (RQ) metrics and levels of concern (LOC) for Federallylisted (listed) threatened/endangered and non-listed species per risk class. 

Risk Class Risk Description RQ LOC 

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from 

acute exposures Peak EEC/LC501

 0.5 

Acute Restricted 

Use 

Potential for effects to animals from acute 

exposures 

Risks may be mitigated through restricted use 

classification 

Peak EEC/LC501

 0.1 

Acute Listed 

Species 

Listed species may be potentially affected by 

acute exposures Peak EEC/LC501

 0.05 

Chronic Potential for effects to non-listed and listed 

animals from chronic exposures 

60-day EEC/NOEC (fish) 

1 21-day EEC/NOEC 

(invertebrates) 

Terrestrial Animals (mammals and birds) 

Acute Potential for effects to non-listed animals from 

acute exposures 

EEC2

/LC50 (Dietary) 

0.5 

EEC/LD50 (Dose) 

Acute Restricted 

Use 

Potential for effects to animals from acute 

exposures 

Risks may be mitigated through restricted use 

classification 

EEC2

/LC50 (Dietary) 

0.2 

EEC/LD50 (Dose) 

Acute Listed 

Species 

Listed species may be potentially affected by 

acute exposures 

EEC 2

/LC50 (Dietary) 

0.1 

EEC/LD50 (Dose) 

Chronic Potential for effects to non-listed and listed 

animals from chronic exposures EEC 2

/NOAEC 1 

Plants 

Non-Listed Potential for effects to non-target, non-listed 

plants from exposures EEC/ EC25

1 

Listed Plant Potential for effects to non-target, listed plants 

from exposures 

EEC/ NOEC 

1 

EEC/ EC05
82 

Appendix G. Justification for Special Study on Plant Reproduction 

Guideline Number: Non-guideline 

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. 

prosulfuron) may impact the reproduction of non-target terrestrial plants. However, there are no 

available data on adverse reproductive impacts to terrestrial plants from prosulfuron residues due 

to spray drift. Terrestrial plant reproductive toxicity data would help to screen for potential plant 

risks associated with prosulfuron 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? 

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 prosulfuron 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 prosulfuron may pose. If the data indicate that prosulfuron poses significant risks to these nontarget 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 prosulfuron 

which may otherwise be avoided, or which are unnecessarily severe.