2

Chlorsulfuron Preliminary Work Plan – Table of Contents

Overview 3

Anticipated Data Needs 4

Statutory and Regulatory Authority 4

Chemical Facts 5

Use and Usage Information 6

Recent Actions 7

Anticipated Risk Assessments for Registration Review 8

Timeline 9

Next Steps 9

Appendix – Additional Areas Considered in Chlorsulfuron’s Registration Review 10

References:

This Preliminary Work Plan summarizes the Environmental Protection Agency's current position 

based on the following documents:

1. Registration Review – Preliminary Problem Formulation for Ecological Risk and 

Environmental Fate, Endangered Species, and Drinking Water Assessments for 

Chlorsulfuron (PC Code 118601; DP Barcode D403354). M. Clock-Rust and K. White. 

November 15, 2012.

2. Chlorsulfuron: Registration Review Scoping Document for Human Health Assessments.

M. Hawkins, S. Piper, and Y. Yung. December 6, 2012.

3. BEAD Chemical Profile for Registration Review: Chlorsulfuron. C. Doucoure, S. 

Ratnayake, and S. Smearman. June 25, 2012

4. Chlorsulfuron: Review of Human Incidents. S. Recore. July 31, 2012

5. Chlorsulfuron: Screening Level Usage Analysis. May 5, 2012

6. PRD Label Data Report: Food/Feed & Non-Food/Non-Feed Uses Considered in 

Registration Review Work Planning for Chlorsulfuron (118601) August 3, 2012

7. Chlorsulfuron: EPA and DuPont 12/6/2012 Focus Meeting Minutes. December 10, 2012.

These and other supporting documents for the chlorsulfuron registration review case may be 

found in the docket EPA-HQ-OPP-2012-0878 at http://www.regulations.gov.
3

OVERVIEW

The docket for chlorsulfuron is now open, initiating the first public comment period for this 

registration review (docket number EPA-HQ-OPP-2012-0878). Chlorsulfuron is a sulfonylurea 

herbicide that is primarily absorbed through the leaves of plants. Sulfonylurea herbicides disrupt 

the synthesis of amino acids in plants by inhibiting the enzyme acetolactate synthase (ALS). 

ALS inhibition in plants adversely affects plant growth and reproduction. Although the 

sulfonylurea herbicides all act upon the same enzyme system in plants, that system is not present 

in animals. Chlorsulfuron is registered for use on barley, oats, wheat, fallow fields, and 

ornamental turf for residential lawns, recreational areas, and golf courses. It is applied as a preemergence soil treatment and post-emergence treatment to control broadleaf weeds and certain 

grass weed species. This Preliminary Work Plan (PWP) document explains what EPA's Office 

of Pesticide Programs knows about chlorsulfuron, highlighting anticipated data and assessment 

needs, identifying the types of information that would be especially useful to the Agency in 

conducting the review, and providing an anticipated timeline for completing chlorsulfuron’s

review.

The registration review process was designed to include a public participation component to 

solicit input from interested stakeholders. The Agency intends, by sharing this information in the 

docket, to inform the public of what it knows about chlorsulfuron and what types of new data or 

other information would be helpful for the Agency to receive as it moves toward a decision on 

chlorsulfuron. The Agency encourages all interested stakeholders to review the PWP and 

Appendix and to provide comments and additional information that will help the Agency’s 

decision-making process for this chemical. In addition to general areas on which persons may 

wish to comment, there are some areas identified in the PWP and Appendix about which the 

Agency specifically seeks comments and information. Interested stakeholders could include 

environmental non-profit or interest groups; pesticide manufacturers; agricultural labor or 

commodity groups; commercial, institutional, residential, and other users of pesticides; or the 

public at large.

The Preliminary Work Plan begins by listing the anticipated data needs for chlorsulfuron. Next, 

it discusses the statutory and regulatory authority for Registration Review. Then the document 

provides chlorsulfuron’s chemical facts, use and usage information, recent actions, the 

anticipated risk assessments, and a projected registration review timeline. Finally, the Appendix 

to this document includes identification and discussion of some areas that are considered 

generally in Registration Review along with some additional chemical case-specific information.
4

ANTICIPATED DATA NEEDS

Table 1 below summarizes anticipated data needs for chlorsulfuron. For additional discussion of 

the anticipated data needs, see the Registration Review – Preliminary Problem Formulation for 

Ecological Risk and Environmental Fate, Endangered Species, and Drinking Water Assessments 

for Chlorsulfuron (PC Code 118601; DP Barcode D403354) and Chlorsulfuron: Registration 

Review Scoping Document for Human Health Assessments.

Table 1: Anticipated Data Needs for Chlorsulfuron’s Registration Review

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

835.4100 Aerobic Soil Metabolism PAIRA; TGAI 24

835.4300 Aerobic Aquatic Metabolism PAIRA; TGAI 24

835.4400 Anaerobic Aquatic Metabolism PAIRA; TGAI 24

835.6200 Aquatic (sediment) Field Dissipation Study TEP 24

850.6100

Environmental Chemistry Methods and Associated 

Independent Laboratory Validation for soil, water, 

and plants1

TGAI 12

870.7800 Immunotoxicity TGAI 12

TGAI = technical grade active ingredient; TEP = typical end-use product; PAIRA= pure active ingredient radiolabeled

STATUTORY AND REGULATORY AUTHORITY

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides distributed or sold in the United States (U.S.) generally must be registered by the 

Environmental Protection Agency (EPA or the Agency), based on scientific data showing that 

they will not cause unreasonable risks to human health or the environment when used as directed 

on product labeling. 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 of no unreasonable adverse effects to human health or 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 make 

sure that as change occurs, products in the marketplace can be used safely. Information on this 

program is provided on EPA’s website.

2

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. The regulations governing registration review begin at 40 CFR 155.40. The 

Agency will consider benefits information and data as required by FIFRA. The public phase of 

 1 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests – including 

renumbering and/or removal of the Tier designation for some guideline studies. See “Final Test Guidelines; OCSPP 850 Series;

Notice of Availability” 77 FR 38282, June 27, 2012. http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-

0154-0028 2 http://www.epa.gov/oppsrrd1/registration_review/
5

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

Agency’s opportunity to state what it knows about the pesticide and what additional risk analyses 

and data or information it believes are needed to make a registration review decision. After 

reviewing and responding to comments and data received in the docket during this initial 

comment period, the Agency will develop a Final Work Plan (FWP) and anticipated schedule for 

the registration review of chlorsulfuron.

Table 2 provides a summary of the current regulatory status of chlorsulfuron.

Table 2: CHLORSULFRON CHEMICAL FACTS

PC code 118601

Case Number 0631

CAS Number 64902-72-3

Year First Registered 1982

Pesticide Type herbicide

Chemical class sulfonylurea

Reregistration Eligibility 

Decision (RED)

2005

Tolerance Reassessment 

Eligibility Decision 

(TRED)

Not applicable. 

Cumulative group Chlorsulfuron is currently not part of a cumulative group.

EPA has not made a common mechanism of toxicity finding as to

chlorsulfuron and any other substances. In addition,

chlorsulfuron does not appear to produce a toxic metabolite

produced by other substances. For the purposes of Registration

Review, therefore, EPA has not assumed that chlorsulfuron

has a common mechanism of toxicity with other substances.

40 CFR Citation Tolerances for residues of chlorsulfuron and its metabolites in or on 

a variety of food and feed crops are established in 40 CFR 

§180.405.

Non-pesticidal uses No non-pesticidal uses of chlorsulfuron.

Pesticide Re-evaluation 

Division, Chemical 

Review Manager

Kaitlin Keller, keller.kaitlin@epa.gov, (703) 308-8172

Registration Division, 

Product Manager

Kable Davis, davis.kable@epa.gov, (703) 306-0415
6

USE AND USAGE INFORMATION

Table 3 summarizes the use and usage information for halosulfuron. Please see the BEAD 

Chemical Profile for Registration Review: Chlorsulfuron. in the registration review docket for 

more details.

Table 3: USE AND USAGE INFORMATION

Summary of Use Selective sulfonylurea herbicide registered for use as preplant, 

preemergence, and postemergence treatments to control grasses and 

broadleaf weeds.

Use Sites Chlorsulfuron is labeled for use on mung beans, barley, field corn, 

oats, proso millet, safflower, sorghum, soybeans, triticale, wheat 

cotton, pastures, rangeland, forage and fodder grasses, farm yards, 

and uncultivated agricultural areas. Non-agricultural use sites 

include ornamental lawn and turf, ditch banks, dry flood plains, 

swamps/marsh bogs/standing water (vegetation), waterway edges, 

and nonagricultural uncultivated areas. 

Summary of Usage From 2006-2010, agricultural usage of chlorsulfuron averaged 

approximately 60,000 pounds annually and was applied on average 

to 5,000,000 acres at an overall average rate of 0.012 lbs active 

ingredient per acre. Winter wheat accounts for approximately 95% 

of agricultural usage of chlorsulfuron. Chlorsulfuron is primarily 

used in Kansas, Oklahoma, and Texas. 

Limited data are available for non-agricultural uses of 

chlorsulfuron. In 2006, small amounts of chlorsulfuron were used 

by lawn care operators and in nursery and floriculture.

Formulation Type Flowable concentrate, granular, and water dispersible granules.

Application Methods Products can be applied by broadcast, low volume ground spray, 

and soil and spot treatment using aircraft, handguns, boom sprayers, 

backpacks, or hand held sprayers.

Technical Registrants E.I. DuPont de Nemours and Company (DuPont); Cheminova, Inc.

No. of Registrations 34 Section 3 products3

Restricted Use No

Guidance for Commenters: Additional areas of use and usage related information

requested for this registration review, and of particular interest to EPA, are described below.

• Certain chlorsulfuron labels are unclear with respect to use in agricultural and nonagricultural uncultivated areas. A clear definition of what sites are included or excluded 

based on these terms is needed. Unclear label terminology could lead to use of 

chlorsulfuron on areas that are not registered use sites. Information on more specific use 

sites would allow a more refined risk assessment. Defining certain use sites is important 

in determining where a product may be used, and which endangered species may be in 

proximity to locations of potential uses of chlorsulfuron. The Agency intends to work 

with registrants to address label uncertainties during registration review. 

 3 Section 3 product labels can be obtained from the Pesticide Product Label System (PPLS) website 

(http://oaspub.epa.gov/pestlabl/ppls.home).
7

• More information on chlorsulfuron use in intermittently flooded low lying sites, such as 

seasonally dry flood plains, bogs, marshes, and swamps would improve the ability to 

predict potential exposure in aquatic systems. 

• Chlorsulfuron is classified as Toxicity Category III for acute dermal toxicity and Toxicity 

Category IV for acute oral toxicity and eye irritation, which requires the Worker Protection 

Standard (WPS) Restricted-Entry Interval (REI) of 12 hours. However, several labels only 

include an REI of 4 hours. The Agency will work with registrants to resolve this issue prior 

to the risk assessment phase of registration review. 

• Confirmation of the following label information: sites of application; formulations;

application methods and equipment; maximum application rates; frequency of 

application, application intervals, and maximum number of applications per season; and 

geographic limitations on use.

• Use distribution (e.g., acreage and geographical distribution of relevant use sites)

• Median and 90th percentile reported use rates (lbs ai/A) from usage data – national, state, 

and county.

• Application timing (date of first application and application intervals) – national, state, 

and county.

• Usage/use information for non-agricultural uses.

• General market share information.

• Typical application interval (days).

• State or local use restrictions.

• Foreign technical registrants not listed above who supply technical chlorsulfuron to the 

US market.

RECENT ACTIONS

On Thursday, December 6, 2012, EPA met with representatives from Dupont for a focus meeting 

to discuss usage information, such as lb a.i./yr sold, general market share information, and 

information on typical use rates vs. maximum use rates, as well as use site clarification for 

uncultivated areas. The focus meeting discussion is summarized in Chlorsulfuron: EPA and 

DuPont 12/6/2012 Focus Meeting Minutes.

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW

The most recent comprehensive human health risk assessment for chlorsulfuron was completed 

in 2002 for a registration related new use request on pasture grasses and to support the 

chlorsulfuron Reregistration Eligibility Decision (RED). The most recent ecological and 

environmental fate risk assessment was completed 2005 in preparation for the chlorsulfuron

RED. Findings and conclusions from these risk assessments are summarized in the Registration 

Review – Preliminary Problem Formulation for Ecological Risk and Environmental Fate, 

Endangered Species, and Drinking Water Assessments for Chlorsulfuron (PC Code 118601; DP 

Barcode D403354) and Chlorsulfuron: Registration Review Scoping Document for Human 

Health Assessments.

During registration review, the Agency anticipates the need to conduct a comprehensive

ecological risk assessment, including an endangered species assessment, for all uses of

chlorsulfuron. For human health, EPA anticipates the need to conduct revised dietary, 

residential, and occupational risk assessments during registration review. If toxicological 

endpoints or points of departure are revised based on the data that are anticipated to be required 
8

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.

Table 4 below summarizes the anticipated registration review risk assessments based on the 

EFED Problem Formulation and HED Scoping Document.

The Agency plans to rely on the most recent comprehensive human health assessment in making 

its registration review decision, as there were no risks of concern at that time and changes in 

Agency models and policies that have occurred since that assessment are not expected to alter 

risk conclusions. If the results of the additional toxicity study that is expected to be required 

changes assessment endpoints or uncertainly/safety factors, the Agency will reconsider the need 

for updated risk assessments. 

Table 4: Anticipated Risk Assessments for Chlorsulfuron’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 

Yes 

Incidents No Although a formal review is not planned, the Agency

will continue to monitor incident data throughout

registration review. For a discussion of

chlorsulfuron' s reported ecological incidents,

see page 23 of the Problem Formulation. 

Human Health

Dietary

Food Yes The dietary and drinking water exposure assessments

are adequate based on current standards; however a

new exposure analysis may need to be conducted

during registration review if there are changes to the

chlorsulfuron toxicological points of

departure and estimated drinking water

concentrations.

Drinking water Yes

Occupational

Handlers (mixers, loaders, 

applicators)

Yes Due to recent occupational exposure science policy

updates, the occupational exposure assessment may

need to be updated to reflect current standard

operating procedures and to incorporate any new

endpoints or uncertainty factors selected based on the

anticipated toxicity data requirement. 

Post-application Yes

Residential

Handlers Yes Due to recent residental exposure science policy

updates, the residential exposure assessment may

need to be updated to reflect current standard

operating procedures and to incorporate any new

endpoints or uncertainty factors selected based on the

anticipated toxicity data requirement. 

Post-application Yes

Other
9

Aggregate Yes Evaluates the combined risk from dietary and 

residential exposures.

Cumulative No EPA has not assumed that chlorsulfuron has a

common mechanism of toxicity with other

substances.

Tolerances Yes EPA anticipates updating the current chlorsulfuron 

tolerance expression in 40 CFR §180.405 to reflect 

current Agency policies. 

Incidents No For a discussion of chlorsulfuron’s reported human 

incidents, see page 11 of the Scoping Document.

Guidance for Commenters: Additional ecological information requested for this 

registration review, and of particular interest to EPA, is described below.

• Ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency.

• Water quality monitoring data (see Appendix for further details).

TIMELINE

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

registration review in Table 5 below.

Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period 2012 - December

Close Public Comment 2013 - February

Case Development

Final Work Plan 2013 - May

Issue DCI 2014 – Jan – March

Data Submission 2016 – Jan – March

30-day Public Comment Period for Draft Risk 

Assessments

2017 – July – Sept.

Registration Review Decision

60-day Public Comment Period for Proposed 

Registration Review Decision

2018 – Jan – March

Registration Review Decision and Begin Post-Decision 

Follow-up

2018

Total (years) 6

NEXT STEPS

After the 60-day public comment period closes, the Agency will review and respond to any 

comments received in a timely manner and then issue a Final Work Plan for the registration 

review of chlorsulfuron.
10

Appendix – Additional Areas Considered in Chlorsulfuron’s Registration 

Review

PUBLIC COMMENTS AND FEEDBACK:

Guidance for Commenters: The areas below highlight topics of special interest to the Agency 

where your comments, data submissions, or reference to sources of additional information could 

be of particular use.

Trade Irritants:

Through the registration review process, the Agency intends to solicit information on trade 

irritants and, to the extent feasible, take steps toward facilitating irritant resolution. The Agency 

will work to harmonize tolerances and international maximum residue limits (MRLs) and may 

modify tolerance levels to do so, when possible. Growers and other stakeholders are asked to 

comment on any trade irritant issues resulting from lack of MRLs or disparities between U.S. 

tolerances and MRLs in key export markets, providing as much specificity as possible regarding 

the nature of the concern. 

Water Quality:

Chlorsulfuron is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act.

4

 In addition, no Total Maximum Daily Loads 

(TMDL) have been developed for chlorsulfuron.

5 More information on impaired water bodies 

and TMDLs can be found at the Agency’s website.

6 The Agency invites submission of water 

quality data for this pesticide. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process7 in order to ensure they can be used quantitatively or qualitatively in 

pesticide risk assessments.

Environmental Justice:

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have 

atypical, unusually high exposure to chlorsulfuron compared to the general population. Please 

comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure compared to the general population.

 4 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885 5

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES

6 http://www.epa.gov/owow/tmdl/

7 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
11

ENDANGERED SPECIES:

A risk assessment that supports a complete endangered species determination has not been 

conducted for chlorsulfuron. The ecological risk assessment planned during registration review 

will allow the Agency to determine whether chlorsulfuron’s use has “no effect” or “may affect” 

federally listed threatened or endangered species (listed species) or their designated critical 

habitats. When an assessment concludes that a pesticide’s use “may affect” a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service 

and/or National Marine Fisheries Service (the Services), as appropriate.

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 for chlorsulfuron, 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), chlorsulfuron 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 

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. Chlorsulfuron

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 

call-ins, requiring the submission of EDSP screening assays for chlorsulfuron. 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 website8.

 8 http://www.epa.gov/endo/
12

HUMAN STUDIES:

Occupational and Residential

Past chlorsulfuron risk assessments rely in part on data from studies in which adult human 

subjects were intentionally exposed to a pesticide to determine their dermal and inhalation 

exposure. Many such studies, involving exposure to many different pesticides, comprise generic 

pesticide exposure databases such as the Pesticide Handlers Exposure Database (PHED), the 

Agricultural Reentry Task Force (ARTF) Database, and the Outdoor Residential Exposure Task 

Force (ORETF) Database. EPA has reviewed all the studies supporting these multi-pesticide 

generic exposure databases, and has found no clear and convincing evidence that the conduct of 

any of them was either fundamentally unethical or significantly deficient relative to the ethical 

standards prevailing at the time the research was conducted. All applicable requirements of 

EPA’s Rule for the Protection of Human Subjects of Research (40 CFR Part 26) have been 

satisfied, and there is no regulatory barrier to continued reliance on these studies.