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INTRODUCTION

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) for 

the registration review of rimsulfuron. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in rimsulfuron’s registration 

review docket (EPA-HQ-OPP-2012-0178). Rimsulfuron is a selective herbicide registered for 

use to control broadleaf and grassy weeds on various agricultural and non-agricultural food and 

non-food sites. There are no registered residential uses.

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency’s website1

.

The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency’s responses to those comments. This section is followed by 

rimsulfuron’s registration review planned data needs, risk assessments expected to be conducted, 

and the projected registration review timeline. Lastly, there is a discussion of next steps.

UPDATES SINCE THE PWP WAS ISSUED

Changes have been made to the data requirements anticipated in the PWP. Please see the Planned 

Data Needs section below.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the rimsulfuron Preliminary Work Plan, which 

opened on September 26, 2012 and closed on November 26, 2012, the Agency received one 

public comment, a submission by technical registrant Dupont. The comment does not address the 

timeline described in the PWP, but it does address the planned ecological risk assessment and 

data requirements. In the PWP, EPA also solicited comments on the specific topics of 

environmental justice, water quality concerns, and trade irritants, but no comments or 

information were received on those issues.

This section does not capture every comment made on the PWP nor all of the Agency’s 

responses. Summarized below is a public comment that resulted in a change to the anticipated

registration review data needs. Public comments and EPA responses in their entirety are located 

in the docket, EPA-HQ-OPP-2012-0178. Summarized public comments and Agency responses 

related to the anticipated ecological risk assessment or data needs are in the February 25, 2013

 1 http://www.epa.gov/oppsrrd1/registration_review/
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Registration Review: Response to Comments on Preliminary Problem Formulation for 

Environmental Fate, Ecological Risk, Endangered Species, and Human Health Drinking Water 

Exposure Assessments for Rimsulfuron.

Comments submitted by DuPont in EPA-HQ-OPP-2012-0178-0009.

1. Comment: DuPont believes that further characterization of secondary metabolites in the 

submitted anaerobic aquatic metabolism study should not be warranted based on OPPTS 

guideline 835.4400 and the facts below:

1. The overall mass balance was 101.1±3.9% (the data summarized from Table VI, VII, and

VIII in MRID #48332004).

2. All major metabolites (IN-70942, IN-70941, IN-J0290, and IN-E9260) were well identified 

by HPLC method and confirmed by the secondary TLC method, which is consistent with 

other rimsulfuron aerobic and anaerobic degradation studies. 

3. Unknown 1 from the combined amount of sediment and water phases (as shown in Tables 

IX, X, XIII, and XIV in MRID #48332004) was indicated greater than 10%. However, 

Unknown 1 was not a single metabolite; rather it was the sum of multiple polar components 

not retained by original HPLC method. Unknown 1 was separated into 4 distinct 

approximately equal peaks by modified HPLC as demonstrated in Figure 17 from MRID 

#48332004. Therefore, no single component was indicated greater than 10% or even 5%.

Response: The Agency has reviewed the information cited in DuPont’s response and agrees 

in principle with each of the points made. However, DuPont did not in their response discuss 

the identity of unextracted residues or the possibility of attempting further extraction steps to 

release these residues. The level of unextracted residues is high – for example, in Table VI on 

page 42 it is shown that the unextracted residues in nonsterile Canadian pond water and 

sediment at 25 C increased steadily over time (e.g., about 19% at 14 days and 71% of the 

applied radioactivity at 3 months after application). The Agency reviewed the submitted 

report (MRID 48332004) and notes while the fraction of bound residues observed under 

nonsterile conditions is quite high, the registrant did extract the sediment three times with 2:1 

acetonitrile:water and then three times with a methanol phosphate buffer system before 

declaring the remaining radioactivity as unextractable. Some characterization of the large 

amount of radiolabeled residues in the sediment was conducted by fractionation into humin, 

fulvic acid, and humic acid fractions. The fractionation procedure needs to be described in 

more detail as only a citation of a Federal Register notice is given as a reference. 

Normally, the high degree of unextracted residues observed in the anaerobic aquatic 

metabolism study would be a basis for requesting an additional study, or, at the very least, 

necessitate more conservative assumptions in risk assessments (e.g., assuming that the 

unextracted residues were part of the total toxic residues.). Somewhat reducing these 

concerns is that much of the formation and decline of parent to and from residues such as IN70941, IN-70942, IN-J0290, and IN-E9260 occurs prior to most of the rise in the amount of 

unextracted radiolabeled residues. Therefore most of the residues which become bound to 

soil organic matter or colloids would more likely be secondary metabolites of less 
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toxicological concern. A special sediment toxicity study could further address whether any 

of the unextracted residues are of toxicological concern and, if it were to show these residues 

to be non-toxic, might allow less conservative exposure assumptions to be made in future 

risk assessments.

It is also relevant to note that unextracted residues while generally less than 25% in the 

aerobic soil metabolism studies, did appear to be rising when these studies were terminated 

after about four months incubation (MRID 48332003; study under review). The Agency will 

not include the anaerobic soil metabolism data requirement in the data call-in for the 

registration review of rimsulfuron.
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PLANNED DATA NEEDS

The table below summarizes the planned data needs for rimsulfuron based on the September 13, 

2012 Registration Review: Preliminary Problem Formulation for Environmental Fate, 

Ecological Risk, Endangered Species, and Human Health Drinking Water Exposure Assessments 

for Rimsulfuron, as well as the February 25, 2013 Registration Review: Response to Comments 

on Preliminary Problem Formulation for Environmental Fate, Ecological Risk, Endangered 

Species, and Human Health Drinking Water Exposure Assessments for Rimsulfuron. The table 

has been updated since the PWP to reflect the public comment that resulted in removal of the 

anaerobic aquatic metabolism data requirement. Also, a terrestrial plant reproduction toxicity 

study has been added to the list below and will be included in the Data Call-in. The study has 

been typically required of all sulfonyl urea herbicides. However, the Agency has determined that 

generation of new non-guideline plant reproduction studies for each sulfonyl urea herbicide is 

unnecessary. Since this determination was made based on plant reproduction data submitted by 

a registrant, the plant reproduction data requirement is being added to the Data Call-in for all 

SU’s for data compensation purposes.

Planned Data Needs for Rimsulfuron’s Registration Review

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

835.6100 Terrestrial field dissipation study2 TGAI and 

degradates 12

835.6200 Aquatic field dissipation study2 TGAI and 

degradates 12

850.1350 Aquatic invertebrate life-cycle (marine)3 TGAI 12

850.1400 Estuarine/marine fish early life stage3 TGAI 12

850.4100 Terrestrial plant toxicity, seedling emergence, 

Tier II TEP 12

850.4150 Terrestrial plant toxicity, vegetative vigor, Tier 

II TEP 12

Nonguideline Terrestrial plant reproduction toxicity4 TGAI 24

 2 See footnote 7 of 40 CFR 158.1300. EPA is requiring only the environmental chemistry analytical methods and 

independent laboratory (ILV) portions of this guideline for soil and water, rather than the full field dissipation 

study. 3 Results from the review of the submitted freshwater studies may negate the need for additional data.

4 Based in part on a review of previously submitted data for another sulfonyl urea herbicide, the Agency has 

determined that generation of new non-guideline plant reproduction studies for each sulfonyl urea herbicide is 

unnecessary. The previously submitted data provide sufficient information for EPA to characterize potential 

impacts of the sulfonyl urea herbicides on plant reproduction. Therefore, to satisfy this requirement, registrants may 

wish to consider citing these existing data in response to the DCI.
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Planned Data Needs for Rimsulfuron’s Registration Review

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

The studies listed below were previously required and are under review. They will NOT be 

included in the anticipated Registration Review DCI. However, if the studies are not 

determined to be acceptable, the registrants will have to resubmit or upgrade them.

835.4100 Aerobic Soil Metabolism TGAI and 

degradates In review

835.4300 Aerobic aquatic metabolism TGAI and 

degradates In review

850.1300 Aquatic invertebrate life-cycle (freshwater) TGAI In review

850.1400 Freshwater fish early life-stage TGAI In review

TGAI = technical grade active ingredient; TEP = typical end-use product;
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RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of rimsulfuron. For human health, EPA 

will conduct revised residential and occupational risk assessments during registration review. If 

toxicological endpoints or points of departure are revised based on the data that are required for 

registration review, they will be considered in the new assessments, as well as any changes to the

standard operating procedures or default exposure assumptions.

The table below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document and the planned assessments have not 

changed from what was included in the PWP.

Planned Risk Assessments for Rimsulfuron’s Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate

Comprehensive ecological 

(species to be assessed 

include terrestrial and aquatic 

organisms), including 

endangered species 

Y

Incidents Y For a discussion of rimsulfuron’s reported ecological 

incidents, see page 22 of the Problem Formulation.

Human Health

Dietary

Food N

Drinking water N

Occupational

Handlers (mixers, loaders, 

applicators)

Y Occupational handler exposure and risk assessments 

are anticipated for the following uses: golf course, sod 

farms athletic fields, industrial and commercial lawns 

and similar nonresidential areas; agricultural food 

crops including soybeans, potatoes, field corn, 

tomatoes, grapes, various tree fruits, and tree nuts.

Post-application Y Occupational post-application exposure and risk 

assessments are anticipated for the following uses: 

soybeans, potatoes, field corn, tomatoes, grapes, 

various tree fruits, tree nuts, and golf course turf.

Residential

Handlers N

Post-application Y Based on the current use patterns, there is only 

potential for post-application dermal exposure for 

recreational golfers. Therefore, a new risk assessment 

is anticipated for the existing golf course turf use. 

Other
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Aggregate Y A new aggregate assessment may be needed to 

include the short-term dermal exposure for the 

recreational golfer.

Cumulative N

Tolerances N

Incidents Y For a discussion of rimsulfuron’s reported human 

incidents, see page 7 of the Scoping Document.

TIMELINE

EPA has created the following estimated timeline for the completion of rimsulfuron’s

registration review. The projected timeline has been updated to reflect changes to the planned 

data needs.

Registration Review for Rimsulfuron – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period 2012 – Sept. – Completed

Close Public Comment 2012 – Nov. – Completed

Case Development

Final Work Plan 2013 - March – Completed

Issue DCI 2013 – Oct.-Dec.

Data Submission 2014 – Oct. – Dec.

Open 60-day Public Comment Period for Draft Risk Assessments 2016 – April – June

Registration Review Decision

Open 60-day Public Comment Period for Proposed Registration Review 

Decision 

2016 – Oct. – Dec.

Registration Review Decision and Begin Post-Decision Follow-up 2017

Total (years) 5

NEXT STEPS

As noted previously, the Agency plans to require environmental fate and ecological effects 

studies for rimsulfuron through a data call-in, expected to be issued in 2013.