Docket Number EPA-HQ-OPP-2009-0624 

www.regulations.gov

Sulfentrazone Final Workplan 

Registration Review 

March 2010 

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Approved by:

Date:

Sulfentrazone Final Work Plan

Registration Review

March 2010

Case Number 7231

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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 sulfentrazone. This FWP includes the expected registration review 

timeline. This work plan also addresses public comments received concerning the Preliminary 

Work Plan in the Summary Document, which was posted in the sulfentrazone registration 

review docket (EPA-HQ-OPP-2009-0624), and any other comments concerning the initial 

docket postings. The sulfentrazone Summary Document provided information on what EPA 

knows about the pesticide and what additional risk analysis data or information the Agency 

believes are needed to make a registration review decision. 

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 ensure that, as the ability to assess risk evolves and as 

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

The public phase of 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 and commit to a final work plan and 

schedule for the registration review of sulfentrazone. 

Sulfentrazone is an aryl triazolinone herbicide registered for use to control a variety of broadleaf 

weeds, and is a member of the light-dependent peroxidizing herbicide (LDPH) class of weed 

control chemicals. It was first registered with the Agency in February 1997 and, therefore, was 

not subject to the reregistration requirements of FIFRA. Sulfentrazone is registered for use on 

several agricultural crops, ornamental turf/plant products, residential lawns, and recreational 

areas, such as golf courses. Several new uses have been proposed for sulfentrazone and are 

currently under Agency review, they are: Brassica, head and stem, Subgroup 5A; Brassica, Leafy 

greens, Subgroup 5B; Melon, Subgroup 9A; Fruiting Vegetable, Group 89 and Okra; Pea, 

Succulent; Flax; Strawberry; and Tuberous and corm Vegetable, Subgroup 1C. 

Updates Since the Summary Document:

Endocrine Disruptor Screening Program 

As required under FFDCA section 408(p), EPA has developed the Endocrine Disruptor 

Screening Program (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 

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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 quantitative relationship between the dose and the E, A, or T effect. 

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. 

This list of chemicals was selected based on the potential for human exposure through pathways 

such as food and drinking water, residential activity, and certain post-application agricultural 

scenarios. This list should not be construed as a list of known or likely endocrine disruptors. 

Sulfentrazone is not among the group of 58 pesticide active ingredients on the initial list to be 

screened under the EDSP. Under FFDCA sec. 408(p) the Agency must screen all pesticide 

chemicals. Accordingly, EPA anticipates issuing future EDSP orders / data call-ins for all 

registration review cases, including those for which EPA has already opened a registration 

review docket for a pesticide active ingredient. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 

chemicals, the test guidelines and the Tier 1 screening battery, please visit EPA’s website: 

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

Agricultural Health Study 

Sulfentrazone is among several agricultural chemicals included in the Agricultural Health Study 

(AHS). The AHS began in 1993 and is a collaboration of the National Institute of 

Environmental Health Sciences (NIEHS), the National Cancer Institute (NCI), the EPA, and the 

National Institute for Occupational Safety and Health (NIOSH). Designed as a large long-term 

epidemiological study, the AHS collects and analyzes data on the health and work practices of 

nearly 90,000 farmers and their families in Iowa and North Carolina who enrolled in the study 

before any disease developed. The study focuses particularly on farmers' exposure to 50 

chemicals including many of the most widely used pesticides. Sulfentrazone is not one of the 50 

chemicals explicitly referenced in the AHS Phase 1 questionnaire. However, it was included in a 

set of chemicals that were not explicitly referenced, but which "were used by 300 or more 

respondents (approximately 1% of respondent applicators).” Exposure to these chemicals is also 

considered in the AHS.

As data are collected over a period of years, scientists can compare overall health outcomes for 

people who differ in whether they have had exposure to various chemicals. While these 

comparisons cannot conclusively demonstrate how exposure affects health, they can show some 

statistical associations. More information on the AHS can be found at: 

http://aghealth.nci.nih.gov. EPA is monitoring the results of the AHS and will consider this 

study in the registration review of sulfentrazone as appropriate. 

Data Call In Status 

In January 2006, EPA issued a data call-in (DCI) to a group of registrants who hold technical 

registrations for the LDPHs requiring submission of Guideline number 850.1400, fish early life4
stage toxicity test, to measure how different wavelengths of light affect the toxicity of the 

LDPHs on aquatic organisms. FMC Corporation, the technical registrant for sulfentrazone, 

requested a waiver for this data requirement, which the Agency denied in December 2009. In 

January 2010, FMC joined the LDPH industry work group which submitted a modified protocol 

for Guideline 850.1400, as required by EPA, to detect phototoxicity in fish in the presence of the 

LDPHs. The protocol has been reviewed and approved by EPA, and pilot testing for the study 

was initiated in November 2009 with submission of the data expected in late 2010. 

Comments Received on Preliminary Work Plan

The sulfentrazone docket received three comments during the 60-day public comment period. 

Two of these comments, from the FIFRA Endangered Species Task Force (FESTF) and FMC 

Corporation, are relevant to sulfentrazone. The other comment, from G. Whitten, was about a 

different pesticide chemical, Rhozol, which is not related to sulfentrazone. Therefore, the 

comment from G Whitten has been moved to the appropriate docket. 

The Agency believes that the comments received do not in any way change the data and risk 

assessment needs or the timeline provided in the Sulfentrazone Preliminary Workplan. 

Therefore, this document finalizes the work plan for the sulfentrazone registration review 

process. An overview of the comments and EPA’s response are presented in the Summary of 

Comments section of this document. 

Risk Assessment and Data Needs

The Agency will be updating and revising the ecological risk assessment for sulfentrazone 

(including an endangered species risk assessment) and updating and revising the occupational, 

residential, and aggregate portions of the human health risk assessment. Additional data that the 

Agency needs to complete these assessments are specified below. 

Ecological Risk: 

• The most recent ecological risk assessment was conducted in July of 2008. Ecological 

fate and effects data have been submitted to support sulfentrazone registrations. 

• The environmental fate database for sulfentrazone is largely complete; however, data 

gaps have been identified. The following environmental fate data requirements have not 

been fulfilled: anaerobic soil metabolism and aerobic aquatic metabolism. In addition, 

the Agency does not have Environmental Chemistry Methods (ECM) and Independent 

Laboratory Validation (ILV) studies to support sulfentrazone. The Agency will require 

these studies for registration review. 

• Four ground water monitoring studies have been submitted, and the Agency is in the 

process of reviewing these studies. 

• The ecological effects database is largely complete and adequate for risk assessment 

purposes. Because sulfentrazone is a light-dependent peroxidizing herbicide (LDPH), the 

Agency has required a phototoxicity study to determine if animals exposed to LDPHs and 

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intense light (similar to sunlight) show increased toxicity relative to controls exposed to 

sulfentrazone and low intensity light via a group data call in for LDPH (GDCI-129081-

26293). The Agency has not received this study for sulfentrazone. 

 

• The Agency has not conducted a risk assessment that supports a complete endangered 

species determination. The ecological risk assessment planned during registration review 

will allow the Agency to determine whether sulfentrazone 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. 

• EPA will issue a data call in (DCI) requiring the following additional guideline studies in 

order to conduct a complete ecological risk assessment for the registration review of 

sulfentrazone: 

o GDLN 835.4200 – Anaerobic soil metabolism 

o GDLN 835.4300 – Aerobic aquatic metabolism 

o GDLN 835.61001

 – Environmental Chemistry Analytical Methods – Soil 

o GDLN 835.62002 – Environmental Chemistry Analytical Methods – Water 

• Please refer to the September 9, 2009 document “EFED Problem Formulation for 

Sulfentrazone Registration Review” in the registration review docket (EPA-HQ-OPP2009-0624) for a detailed discussion of the anticipated risk assessment needs. 

Human Health Risk: 

• The most recent human health risk assessment on sulfentrazone was conducted in May of 

2003 in order to support the registration of sulfentrazone use on several agricultural 

crops, ornamental turf/plant products, residential lawns, and non-crop land areas. In 

addition, a human health risk assessment is currently underway for the recently proposed 

new agricultural uses of sulfentrazone. 

• The toxicity database for sulfentrazone is largely complete, with the exception of an 

immunotoxicity study (870.7800), which is required as a part of new data requirements in 

the 40 CFR Part 158 for conventional pesticide registration. This study will be included 

in the upcoming DCI. 

As part of the ongoing risk assessment for the proposed new uses of sulfentrazone, . the Agency 

is considering revision of the hazard assessment to include changes to the point of departure and 

uncertainty factors, based on the Agency’s review of a published developmental neurotoxicity 

study (DNT) study. 

 

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 EPA will require only the analytical method portion of OPPTS GDLN 835.6100, terrestrial field dissipation. 

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 EPA will require only the analytical method portion of OPPTS GDLN 835.6200, aquatic field dissipation. 

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• The dietary exposure database is adequate to support existing registration. The Agency 

does not anticipate requiring any additional dietary exposure data during registration 

review. 

• The most recent acute and chronic dietary exposure (food and drinking water) 

assessment, conducted in May 2003, identified no risks of concern. As part of the 

ongoing risk assessment for the proposed uses of sulfentrazone, however, a revised acute 

and chronic dietary assessment is underway. The Agency does not anticipate revising the 

drinking water assessment for this current dietary assessment. However, the Agency will 

reconsider the need for a new drinking water and dietary assessment based on the results 

of the four groundwater studies currently under review and other outstanding data 

requirements. 

• No residential handler scenarios have previously been assessed by the Agency. 

Although the May 2003 risk assessment includes turf use on lawns and gof courses, the 

products registered for this use were labeled for use only by Professional Lawn Care 

Operators. Therefore, handler exposure to homeowners was not expected. A recent 

review of sulfentrazone labels, however, identified labels that allow for homeowner 

application of these products to residential areas. Therefore, the Agency determined that 

residential handlers are likely to be exposed to sulfentrazone residues via dermal and 

inhalation routes during mixing, loading, and applying activities. The Agency will 

conduct a residential handler assessment. 

• A residential post-application risk assessment was conducted in May 2003; however, the 

assessment only considered liquid applications of sulfentrazone at a maximum 

application rate of 0.03 lb ai/A. There are other formulations available, such as dry 

flowables and granular, and higher registered application rates for residential turf use 

(0.375 lb ai/A). The Agency intends to update the risk assessment to account for these 

additional formulations and the higher application rate. 

• The most recent aggregate exposure assessment was conducted in May 2003. The 

aggregate assessment is being revised as part of the ongoing risk assessment for proposed 

new uses, and will consider the possible changes to the hazard assessment and the 

residential handler and post-application assessments. 

• The most recent occupational handler and post-application exposure assessments were 

conducted in May 2003. Since the last assessment, additional formulations, such as dry 

flowables and granulars, have been registered. Based on these new scenarios, as well as 

the changes being considered for the hazard assessment, some handler and postapplication scenarios may need to be reassessed. 

• In summary, EPA will issue a DCI requiring the following guideline study: 

o GDLN 870.7800 – Immunotoxicity Study 

• Please refer to the September 9, 2009 “Sulfentrazone. Human Health Assessment 

Scoping Document in Support of Registration Review” in the registration review docket 

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(EPA-HQ-OPP-2009-0624) for a detailed discussion of the anticipated risk assessment 

needs. 

Other Data Needs 

• 830.7050 UV/Visible Light Absorption – this study is a new data requirement under 40 

CFR part 158 (Product Chemistry Data Requirements) for registration of a pesticide 

(food and non-food uses). The Agency will be requiring this study to obtain basic 

information about the compound’s identity/composition and the wavelengths at which the 

compound may be susceptible to photochemical degradation. 

Timeline:

EPA has created the following estimated timeline for the completion of the sulfentrazone 

registration review. 

Registration Review for Sulfentrazone – Projected Registration Review Timeline

Activities Estimated 

Month/Year 

Phase 1: Opening the docket 

Open Docket and Public Comment Period Sept. 2009 

Close Public Comment Nov. 2009 

Phase 2: Case Development 

Develop Final Work Plan (FWP) March 2010 

Issue Data Call-In Oct – Dec. 2010 

Data Submission Oct – Dec. 2012 

Open Public Comment Period for Preliminary Risk Assessments April – June 2014 

Close Public Comment Period July – Sept. 2014 

Phase 3: Registration Review Decision 

Proposed Registration Review Decision Oct. – Dec. 2014 

Close Public Comment Period Jan. – March 2015 

Final Registration Review Decision and Begin Post-Decision Follow-up 2015 

Total (years) 6 

Summary of Comments 

(1) FIFRA Endangered Species Task Force (FESTF) 

Comment: FMC corporation is a member of FESTF and is entitled to rely on the FESTF 

information management system (IMS) and NatureServe data to fulfill the requirements of 

Pesticide Registration Notice 2000-2. 

Response: The Agency thanks FESTF for its comment and will consider this information as it 

conducts the registration review and makes its registration review decisions.

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(2) FMC Corporation 

FMC Corporation, the sulfentrazone registrant, submitted several comments to the sulfentrazone 

registration review docket on a variety of topics. A summary of these comments and EPA’s 

responses is provided below. None of these comments change the Agency’s proposed workplan 

or anticipated data needs for sulfentrazone. 

Comment: FMC disagrees with anticipated environmental fate data requirements, and cites the 

Code of Federal Regulations (CFR, 40 CFR ). 

Response: FMC cited the CFR section pertaining to antimicrobial pesticides, not conventional 

pesticides such as sulfentrazone. Therefore, EPA does not intend to change the anticipated data 

requirements for sulfentrazone. 

Comment: FMC cites several environmental fate and groundwater studies submitted to the 

Agency. FMC believes that these studies will inform the ecological risk assessment for 

sulfentrazone. 

Response: EPA will review these studies and consider them when conducting the ecological risk 

assessment for sulfentrazone. 

Comment: FMC cites a fish early life stage for another chemical that it believes satisfies the 

outstanding data requirement for phototoxicity from the LDPH group DCI. 

Response: EPA has re-evaluated the cited study and determined that it will not satisfy the data 

requirement. FMC has since agreed to join an industry work group which is sharing the cost of 

developing phototoxicity data. 

Comment: FMC disagrees with the Agency’s interpretation of a developmental neurotoxicity 

study from the published literature and the proposed use of this study in human health risk 

assessment for sulfentrazone. FMC submits an expert opinion containing a critical review of this 

study as an addendum to its comments. 

Response: EPA is reviewing the expert opinion and will consider it in the human health risk 

assessment for sulfentrazone. 

Comment: FMC requests clarification on a residue chemistry data gap identified for flax and 

tomato processing studies. 

Response: EPA considers this a data gap because of deficiencies in the submitted studies. 

Comment: FMC disputes the maximum single and seasonal application rate of 2.25 lbs ai/A 

cited by EPA in the Summary Document. 

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Response: EPA has verified that FMC is correct and that the maximum application rate is 0.375 

lb ai/A. 

Next Steps

The Agency plans to develop and issue a Data Call-In Notice (DCI) for the studies identified in 

this document by December 31, 2010. 

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