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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 diclosulam. This work plan addresses public comments received concerning the 

Preliminary Work Plan (PWP), which was posted in the diclosulam registration review docket (EPAHQ-OPP-2015-0285). Diclosulam is a broad spectrum herbicide and is a member of the 

triazolopyrimidine sulfonamide class of pesticides. It is formulated as a water dispersible granular 

(WDG) in water soluble packets (WSP), and is currently registered for use on peanuts and soybeans; and 

used in impregnated dry bulk fertilizers. 

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 

website.1

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 registration review planned data 

needs, risk assessments expected to be conducted, and the projected registration review timeline for 

diclosulam. Lastly, there is a discussion of next steps. 

UPDATES SINCE THE PWP WAS ISSUED 

The Agency published a Federal Register Notice on June 16, 2015 (80 FR 34408), announcing a 

proposal to voluntarily cancel the section 24(c) registrations, MO040001 and TN040005. These 

registrations are the only diclosulam registrations for use on cottonwood plantings. 

SUMMARY OF COMMENTS AND AGENCY RESPONSES 

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

June 24, 2015 and closed on August 24, 2015, the Agency received three public comments. Comments 

were submitted by Dow AgroSciences LLC, the Center for Biological Diversity (CBD), and the FIFRA 

Endangered Species Task Force (FESTF), LLC. The comments do not address the timeline described in 

the PWP, but they do 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. 

 

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 http://www2.epa.gov/pesticide-reevaluation 
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This section does not capture every comment made about the PWP nor all of the Agency’s responses. 

Summarized below are public comments that are of a broader regulatory nature. Public comments and 

EPA responses in their entirety are located in the docket, EPA-HQ-OPP-2015-0285. Summarized public 

comments and Agency responses related to the anticipated ecological risk assessment or data needs are 

in the Response to Public Comments on: “Registration Review – Problem Formulation for 

Environmental Fate, Ecological Risk and Endangered Species for Diclosulam (06/09/15; PC Code 

129122; DP Barcode 424568).” 

Comments submitted by FESTF in EPA-HQ-OPP-2015-0285-0013. 

1. Comment: FESTF previously submitted data necessary to support the analysis of diclosulam use and 

listed species locations and potential exposure. In addition, FESTF commented that the technical 

registrant of diclosulam is a member of the FESTF (or a company having met its data compensation 

obligations) and is entitled to rely on FESTF data. 

Response: The Agency thanks FESTF for its comment and will take this under consideration. 

Comments submitted by CBD in EPA-HQ-OPP-2015-0285-0011. 

2. Comment: Under the Endangered Species Act, it is EPA’s duty to consult with the U.S. Fish and Wildlife 

Service and National Marine Fisheries Service on the registration review of diclosulam and approval of 

all diclosulam end-use product labels. In addition, the EPA must make defensible “Not Likely to 

Adversely Affect” and “Likely to Adversely Affect” determinations as a prerequisite for defensible 

“Jeopardy” and “No Jeopardy” determinations. EPA and the services must assess the adverse impacts 

of diclosulam in critical habitat.

Response: EPA has reviewed the comments from CBD on the registration review docket opening 

for diclosulam and plans to address many of the concerns raised by CBD as part of the 

implementation plan for assessing the risks of pesticides to listed species based on the 

recommendations of the April 2013 National Academy of Sciences (NAS) report. EPA will address 

concerns specific to diclosulam in connection with the development of its final registration review 

decision for this pesticide.

In November 2013, the EPA, along with the Services and the USDA, released a summary of their 

joint Interim Approaches for assessing risks to endangered and threatened (listed) species from 

pesticides. The Interim Approaches were developed jointly by the agencies in response to the NAS 

recommendations and reflect a common approach to risk assessment shared by the agencies as a way 

of addressing scientific differences between the EPA and the Services. The NAS report outlines 

recommendations on specific scientific and technical issues related to the development of pesticide 

risk assessments that EPA and the Services must conduct in connection with their obligations under 

the ESA and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on November 15, 

2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 Pesticide 

Program Dialogue Committee (PPDC) and State-FIFRA Issues Research and Evaluation Group 

(SFIREG) meetings. The agencies also held stakeholder workshops in April and October 2014, 

allowing additional opportunities for stakeholders to comment on the Interim Approaches. 
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Additional workshops are planned to enhance stakeholder involvement. As part of a phased, iterative 

process for developing the Interim Approaches, the agencies will also consider public comments on 

the Interim Approaches in connection with the development of upcoming registration review 

decisions. The details of the joint Interim Approaches are contained in the white paper, Interim 

Approaches for National-Level Pesticide Endangered Species Act Assessments Based on the 

Recommendations of the National Academy of Sciences April 2013 Report, dated November 1, 2013. 

Given that the agencies are continuing to develop and work toward implementation of the Interim 

Approaches to assess the potential risks of pesticides to listed species and their designated critical 

habitat, the ecological problem formulation supporting this Final Work Plan for diclosulam does not 

describe the specific ESA analysis, including effects determinations for specific listed species or 

designated critical habitat, to be conducted during registration review. In the ecological problem 

formulation document for diclosulam, EPA described the screening-level risk assessment to 

determine the potential effects of diclosulam on all taxa of non-target wildlife and plants, which will 

assume that listed species and their designated critical habitats may be present in the vicinity of the 

application of diclosulam. This screening-level assessment will allow EPA to focus its future 

evaluations on the types of species where the potential for effects exists once the scientific methods 

being developed by the agencies have been fully vetted. While the agencies continue to develop a 

common method for ESA analysis, the planned screening-level risk assessment for the registration 

review of diclosulam will describe the level of ESA analysis completed for this particular 

registration review case. Once the agencies have fully developed and implemented the scientific 

methods necessary to complete risk assessments for endangered and threatened (listed) species and 

their designated critical habitats, these methods will be applied to subsequent analyses for 

diclosulam as part of completing this registration review. 

PLANNED DATA NEEDS 

Table 1 below summarizes the planned data needs for diclosulam based on the Registration Review: 

Problem Formulation for Environmental Fate, Ecological Risk and Endangered Species for Diclosulam 

and the Response to Public Comments on: “Registration Review – Problem Formulation for 

Environmental Fate, Ecological Risk and Endangered Species for Diclosulam (06/09/15; PC Code 

129122; DP Barcode 424568).” The planned data needs have not changed from what was included in 

the PWP, but the estimated timeframe for the aerobic soil metabolism study and the test material for the 

three field and semi-field pollinator studies have been revised. 
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Table 1: Planned Data Needs for the Diclosulam Registration Review 

Guideline 

Number2 Study Title2 Test Material 

Estimated Timeframe 

(Months from receipt of 

DCI) 

835.4100 Aerobic Soil Metabolism3 TGAI 24 

850.2300 Avian reproduction toxicity test, mallard 

duck 

TGAI 24 

850.1350 Invertebrate Lifecycle Toxicity test with 

a marine/estuarine invertebrate species 

TGAI 12 

850.1400 Fish Early Life Stage Toxicity Test with 

a marine/estuarine fish species 

TGAI 12 

850.1400 Fish Early Life Stage Toxicity Test with 

a freshwater fish species 

TGAI 12 

Non-Guideline* Acute oral toxicity to adult honey bees TGAI 12 

Non-Guideline* Acute oral toxicity to larval honey bees TGAI 12 

Non-Guideline* Chronic oral toxicity to larval honey bees TGAI 12 

Non-Guideline* Chronic oral toxicity to adult honey bees TGAI 12 

Non-Guideline** Field trial of residues in pollen and nectar TEP 24 

Non-Guideline** Semi-field testing for pollinators TEP 24 

850.3040** Field testing for pollinators TEP 24 

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

*Tier 1 (Laboratory-based studies) 

**Tier 2 and 3 (Semi-field and full field colony-level studies) The need for a higher tier test for pollinators will be 

determined based upon lower-tiered tests and/or other lines of data and the need for a refined pollinator risk assessment.

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 diclosulam. For human health, EPA 

evaluated the status of the human health risk assessments for diclosulam and determined that sufficient 

data are available to complete the risk assessment. In the Diclosulam: Human Health Assessment 

Scoping Document and Preliminary Human Health Risk Assessment in Support of Registration Review, 

summarized in Table 2 below, the Agency evaluated the hazard and exposure data and conducted 

occupational and residential exposure assessments, as needed, to estimate the risk to human health that 

will result from the currently registered uses of pesticides. 

 

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

including renumbering and other designations or changes 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=EPAHQ-OPPT-2009-0154-0028 3

 Aerobic soil metabolism data are required for four soils, but are currently only available for three. In addition to the need for 

data from an additional soil, there is uncertainty about the identity of unextracted residues in the three studied soils. 

Depending on results from the additional soil, further data may be needed for other soils. Guidance available at 

http://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/guidance-addressing-unextracted-pesticide-residues

should be followed (particularly the use of a range of solvent systems) in order to properly evaluate residues that were not 

extracted from soils in the previous studies. 
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Table 2 summarizes the planned registration review risk assessments based on the Problem Formulation 

for Environmental Fate, Ecological Risk and Endangered Species for Diclosulam and the completed 

registration review human health risk assessment based on the Diclosulam: Human Health Assessment 

Scoping Document and Preliminary Human Health Risk Assessment in Support of Registration Review. 

Table 2 has not changed from what was included in the PWP. 

Table 2: Planned Risk Assessments for the Diclosulam 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 Additional data are required in order to conduct the ecological risk assessment. 

Incidents Will check 

for 

updates 

For a discussion of reported ecological incidents for diclosulam, see page 18 of the 

Problem Formulation. 

Human Health 

Dietary 

Food Completed In support of Registration Review, an updated chronic dietary (food and drinking water) 

exposure and risk assessment was conducted. The chronic dietary (food and drinking 

water) exposure estimates are below the level of concern (<100% cPAD) for the general 

U.S. population and all population subgroups (<1% of the cPAD), except all infants at 

1.2%. Therefore, the chronic dietary diclosulam risk estimates are not of concern. A dose 

and endpoint of concern attributable to a single dose were not observed; therefore, an 

acute point of departure was not selected and an acute dietary exposure assessment is not 

required for diclosulam. 

Drinking water Completed 

Occupational 

Handlers 

(mixers, 

loaders, 

applicators) 

Completed In support of Registration Review, an updated occupational exposure assessment for 

diclosulam was conducted for mixers/loaders of WSP formulations, mixer/loaders for 

impregnation of dry bulk fertilizers, and for applicators of spray and dry bulk fertilizer 

containing diclosulam. The assessment was based on the maximum registered application 

rates. Occupational handlers are anticipated to have short- and intermediate-term dermal 

and inhalation exposures. No short- or intermediate-term dermal toxicological endpoints 

were identified so a quantitative dermal risk assessment was not conducted; dermal risk is 

not of concern. The occupational handler exposure and risk estimates indicate that the 

short- and intermediate-term inhalation margins of exposure (MOEs) are not of concern 

(i.e., an MOE > the LOC of 100) at baseline personal protective equipment (PPE; i.e., no 

respirator). 
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Post-application Completed The Agency did not conduct a quantitative post-application inhalation risk assessment for 

performing post-application activities in previously treated fields. The Agency will 

determine in future assessments whether data (i.e., flux studies, route-specific inhalation 

toxicological studies) or further analyses are required for specific chemicals. In addition, 

the Agency is continuing to evaluate the available post-application inhalation exposure 

data generated by the Agricultural Reentry Task Force. 

An inhalation exposure assessment was performed for occupational/commercial handlers, 

and MOEs are not of concern. Handler exposure resulting from application of pesticides 

outdoors is likely to result in higher exposure than post-application exposure. Therefore, 

it is expected that these handler inhalation exposure estimates would be protective of 

most occupational post-application inhalation exposure scenarios. 

No short- or intermediate-term dermal toxicological endpoints were identified for 

diclosulam, so a quantitative dermal post-application risk assessment was not conducted; 

dermal risk is not of concern. 

Residential 

Handlers No There are no proposed or registered products containing diclosulam that would result in 

Post-application No residential exposure. Therefore, a residential exposure assessment was not performed. 

Bystander/Spray 

drift 

Completed A quantitative spray drift assessment was conducted for diclosulam. Incidental oral risk 

estimates were evaluated. The incidental oral margins of exposure (MOEs) for children 1 

to <2 years old were >270,000 at the field’s edge, and are not of concern. 

Other 

Aggregate Completed An acute aggregate risk assessment was not performed because an endpoint of concern 

attributable to a single oral dose was not selected for any population subgroup (including 

infants and children). Short- and intermediate-term aggregate risk assessments were not 

performed because there are no registered residential non-food uses. Since there are no 

residential uses, the chronic dietary (food and water) exposure estimates represent 

chronic aggregate exposure. Therefore, the chronic aggregate risk estimates are not of 

concern to EPA. 

Cumulative No Unlike other pesticides for which EPA has followed a cumulative risk approach based on 

a common mechanism of toxicity, EPA has not made a common mechanism of toxicity 

finding as to diclosulam and any other substances and diclosulam does not appear to 

produce a toxic metabolite produced by other substances. 

Tolerances Yes According to EPA’s Interim Guidance on Tolerance Expressions, the tolerance 

expressions for diclosulam should be revised as follows: 

Under 40 CFR §180.543(a): “Tolerances are established for residues of diclosulam, 

including its metabolites and degradates, in or on the commodities in the table below. 

Compliance with the tolerance levels specified in the table is to be determined by 

measuring only diclosulam [N-(2,6-dichlorophenyl)-5-ethoxy-7-fluoro[1,2,4] 

triazolo[1,5-c]pyrimidine-2-sulfonamide] in or on the following commodities: 

Tolerance Summary for Diclosulam (40 CFR §180.543) 

Commodity Established Tolerance (ppm) Comments 

40 CFR §180.543: diclosulam [N-(2,6-dichlorophenyl)-5-ethoxy-7-fluoro[1,2,4] 

triazolo[1,5-c]pyrimidine-2-sulfonamide] 

Peanut 0.02 

Soybean, seed 0.02 
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Incidents Will check 

for 

updates 

For a discussion of reported human incidents for diclosulam see page 11 of the Scoping 

Document and the Diclosulam: Tier I Review of Human Incidents. 

TIMELINE

EPA has created the following estimated timeline for the completion of the diclosulam registration 

review in Table 3 below. The projected timeline has not changed since the PWP. 

Table 3: Registration Review for Diclosulam – Projected Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and 60-day Public Comment Period June 2015 – 

Completed 

Close Public Comment August 2015 – 

Completed 

Case Development 

Final Work Plan December 2015 – 

Completed 

Issue DCI January-March 2016 

Data Submission January-March 2018 

60-day Public Comment Period for Draft Ecological Risk Assessment4 July-September 2019 

Registration Review Decision 

60-day Public Comment Period for Proposed Registration Review Decision October – December 

2020 

Registration Review Decision and Begin Post-Decision Follow-up 2021 

Total (years) 6 

NEXT STEPS 

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

studies for diclosulam through a Data Call-In Notice, expected to be issued in 2016. 

 

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 The regulations governing Registration Review generally require the Agency to provide a public comment period of at least 

30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the Agency plans to 

provide a 60 calendar day public comment period generally for draft risk assessments.