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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 chlorothalonil. This work plan addresses public comments received 

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

review docket (EPA-HQ-OPP-2011-0840). Chlorothalonil is registered for a variety of 

conventional uses, including food and ornamental crops in both agricultural and residential sites. 

Additional conventional uses include non-residential turf and forest nursery trees. Chlorothalonil 

is also registered as an antimicrobial pesticide for use as an industrial and consumer wood 

preservative, in the manufacture of fungicidal/mildewcidal/agalcidal paints, stains, and coatings, 

and in many industrial and building products such as caulks, sealants, adhesives, coatings, 

concrete blocks and surfaces, emulsions, grouts, plaster and stucco.

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 

chlorothalonil’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

The PWP list of data requirements for antimicrobial uses included some incorrect guideline 

numbers, which have been corrected in this FWP. The PWP included guideline numbers 

850.3110, 850.3220, 850.3240, and 850.3280. The correct guideline numbers are 835.3110, 

835.3220, 835.3240, and 835.3280.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

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

opened on March 28, 2012 and closed on May 29, 2012, the Agency received eleven public 

submissions. Comments were submitted by several concerned citizens, several California water 

quality control groups, the California Rural Legal Assistance Foundation (CRLAF), FIFRA 

Endangered Species Task Force, Pesticide Action Network of North America (PANNA), as well 

as two registrants, Sipcam Agro USA and Syngenta Crop Protection. The comments do not 

 

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http://www.epa.gov/oppsrrd1/registration_review/
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address the timeline described in the PWP, but they do address the planned ecological and 

human health risk assessments and data requirements, as well as general concern over the effects 

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

environmental justice, water quality concerns, trade irritants and impurities. Water quality 

concerns were raised by the California Central Valley Regional Water Quality Control Board, 

California Stormwater Quality Association, and San Francisco Bay Regional Water Control 

Board, as well as some concerned citizens. Environmental justice concerns were raised by 

CRLAF.

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

responses. Summarized below are public comments that resulted in changes to the anticipated

registration review data needs, risk assessments, or timeline, or are of a broader regulatory nature

and not captured in the separate EPA response documents. Public comments and EPA responses 

in their entirety are located in the docket, EPA-HQ-OPP-2011-0840. Summarized public 

comments and Agency responses related to the anticipated ecological risk assessment, data 

needs, and water quality concerns are in the Chlorothalonil Registration Review Problem 

Formulation—Environmental Fate and Effects Division's Response to Public Comments, while 

those relevant to the anticipated human health risk assessment, data needs, and environmental 

justice concerns are in the Chlorothalonil: Response to Comments on the Human Health 

Assessment Scoping Document and Preliminary Work Plan. 

Comments submitted by Sipcam Agro USA, Inc. in EPA-HQ-OPP-2011-0840-0015

1. Comment: Sipcam believes that spraying and dipping of pressure treated lumber is rare 

and uneconomical. The registrant also provides other additional information on their 

understanding of chlorothalonil used as a wood preservative.

Response: The Agency is required to reevaluate all registered uses associated with each 

active ingredient undergoing registration review. To minimize the potential for EPA to 

overestimate risk, registrants are encouraged to submit requests to amend labeling that

reflects only supported uses. Upon receiving amended labels, the Agency can reconsider 

the anticipated risk assessment needs for the wood preservative use patterns.

2. Comment: Sipcam provided citations for existing public literature studies on the leaching 

of chlorothalonil from treated wood and requested guidance with regards on the methods 

and substrates that should be used to conduct the leaching studies anticipated to be 

required.

Response: The Agency encourages the registrants to submit relevant studies and 

applicable waivers in response to the data call-in associated with this registration review. 

At that time, the Agency will review the information to determine if the wood leaching 

data requirement is adequately met and can be waived. In the event the literature studies 

are not sufficient, the Agency recommends that the registrant conduct the study according 

to the AWPA E11-06 method for addressing leaching from wood submerged in water. 

The Agency has clarified the recommended study method in this FWP.
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3. Comment: “The levels of HCB in currently registered technical products are well 

established: current technical products are produced to a specification of <40ppm HCB. 

Sipcam Agro USA, Inc. has chlorinated dioxin/furan data for its registered sources of 

chlorothalonil tech and intends to submit this data to the Agency, at the latest, at the time 

of Data Call In (DCI).”

Response: The Agency encourages the registrants to submit relevant information at any 

time or, at the very latest, at the time of the data call-in associated with this registration 

review. 

Comment submitted by FIFRA Endangered Species Task Force (FESTF) in EPA-HQOPP-2011-0840-0016

4. Comment: The FIFRA Endangered Species Task Force (FESTF) submitted a comment

that the Agency should ensure any company who is a registrant for chlorothalonil, but 

not a member of FESTF (or a company having met its data compensation obligations)

provide a formal offer-to-pay to FESTF in conjunction with their support of the active

ingredient. 

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

as it conducts the registration review process and makes its registration review decision.
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PLANNED DATA NEEDS

The table below summarizes the planned data needs for chlorothalonil based on the March 22, 

2012 Registration Review – Preliminary Problem Formulation for the Ecological Risk 

Assessment and Drinking Water Exposure Assessment of Chlorothalonil and March 13, 2012

Chlorothalonil - Human Health Assessment Scoping Document in Support of Registration 

Review. The planned data needs have not changed from what was included in the PWP.

Planned Data Needs for the Registration Review of Chlorothalonil

Conventional and Antimicrobial Uses

Guideline 

Number Study Title

Test Material

Estimated 

Timeframe

(Months 

from receipt 

of DCI)

835.1230 Adsorption/desorption batch equilibrium TGAI 12

835.1240 Soil column leaching TGAI 12

835.2120 Hydrolysis TGAI 12

835.2240 Aqueous photolysis TGAI 12

835.4100 Aerobic soil metabolism TGAI 24

835.4200 Anaerobic soil metabolism TGAI 24

835.4300 Aerobic aquatic metabolism TGAI 24

835.4400 Anaerobic aquatic metabolism TGAI 24

850.1075 Saltwater fish acute toxicity TGAI 12

850.1350 Saltwater invertebrates life cycle TGAI 12

850.1400 Saltwater fish early life stage TGAI 12

850.1735 Freshwater invertebrate acute whole sediment 

toxicity TGAI 12

850.1740 Saltwater invertebrate acute whole sediment 

toxicity TGAI 12

870.3465 90-day inhalation toxicity (rat) TGAI 24

Planned Data Needs for the Registration Review of Chlorothalonil

Conventional Uses Only

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Measured 

in Months 

from DCI 

Receipt)

835.2370 Air photolysis TGAI 12

835.6100 Terrestrial field dissipation TGAI 24

835.8100 Field volatility TGAI 12
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850.4100 Seedling emergence, Tier II TGAI 12

850.4150 Vegetative Vigor, Tier II TGAI 12

850.2100 Acute avian oral, passerine2 TGAI 12

860.1360 Multiresidue method recovery data SDS-3701 12

870.6200 Acute neurotoxicity TGAI 12

870.7800 Immunotoxicity TGAI 12

Nonguideline 

study

(Special 

Study)

Avian acute inhalation3

TGAI

12

Planned Data Needs for the Registration Review of Chlorothalonil

Antimicrobial Uses Only

Guideline 

Number Study Title Test Material

Estimated 

Timeframe

(Measured 

in Months 

from DCI 

Receipt)

835.1110 Activated sludge sorption isotherm TGAI 12

835.3110 Ready biodegradation4 TGAI 12

850.6800 Modified activated sludge respiration 

inhibition4 TGAI 12

835.3220 Porous pot4 TGAI 12

835.3240 Simulation tests—aerobic sewage treatment: 

A. activated sludge4 TGAI 12

835.3280 Simulation tests to assess the biodegradability 

of chemicals discharged to wastewater4 TGAI 12

 

2 The anticipated DCI will provide that a protocol must be submitted for review and approval by the Agency prior to 

initiating this study.

3 The anticipated DCI will provide that a protocol must be submitted for review and approval by the Agency prior to 

initiating this study.

4 The results of the Activated Sludge Respiration Inhibition Test (ASRI) expected to be required will determine 

which of these four biodegradation tests would be anticipated to be required. If the ASRI test EC50 is less than or 

equal to 20 mg/L, then either the (i)Biodegradation in Activated Sludge Study or (ii) Simulation Test – Aerobic 

Sewage Treatment: A. Activated Sludge Units or (iii) the Porous Pot Test would be anticipated to be required. If the 

ASRI test EC50 is greater than 20 mg/L, then the DCI expected to be issued would provide that the registrant would 

choose to conduct either: (i) Ready Biodegradability or (ii) a) Biodegradation in Activated Sludge or b) Simulation 

Test – Aerobic Sewage Treatment: A. Activated Sludge Units or c) the Porous Pot Test. If the Ready 

Biodegradability study is conducted and passes, then no further testing would be expected to be required. If, 

however, the antimicrobial fails the Ready Biodegradability study, then the a) Biodegradation in Activated Sludge or 

b) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or c) the Porous Pot study would be 

expected to be required.
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875.1400 Indoor inhalation exposure5 TGAI/TEP 12

875.1600 Exposure monitoring data reporting TGAI/TEP 12

875.1700 Product Use Information TGAI/TEP 12

875.2300 Surface residue dissipation6 TGAI/TEP 24

Nonguideline 

study

(Special 

Study)

Wood leaching study(AWPA E11-06)7 TEP 24

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 chlorothalonil. 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

March 22, 2012 Registration Review – Preliminary Problem Formulation for the Ecological Risk 

Assessment and Drinking Water Exposure Assessment of Chlorothalonil and the March 13, 2012

Chlorothalonil. Human-Health Assessment Scoping Document in Support of Registration 

Review. The planned assessments have not changed from what was included in the PWP.

Planned Risk Assessments for the Registration Review of Chlorothalonil – Conventional 

and Antimicrobial Uses

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

 

5 The Agency anticipates the need to require inhalation exposure studies for the following scenarios: open-pour 

liquids during material preservation; open-pour wettable powders during material preservation; brush/roller 

application of treated paints; airless sprayer application of treated paints; and dip, spray, and pressure treatment of 

wood.

6 Anticipated to be required to assess residential exposure to pressure-treated wood. The anticipated DCI will 

provide that a protocol must be submitted for review and approval by the Agency prior to initiating this study.

7 The Agency recommends that the registrant conduct the wood leaching study according to AWPA E11-06 method 

for addressing leaching from wood submerged in water. The anticipated DCI will provide that a protocol must be 

submitted for review and approval by the Agency prior to initiating this study.
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Incidents Y For a discussion of chlorothalonil’s reported 

ecological incidents, see page 69 of the 

Problem Formulation.

Human Health

Dietary

Food TBD If there are no changes to the estimated 

drinking water concentrations (EDWCs),

toxicological endpoints or points of 

departure, then results from the last dietary 

assessment will be used for registration 

review.

Drinking water TBD If there are no changes to the EDWCs, 

toxicological endpoints or points of 

departure, then results from the last dietary 

assessment will be used for registration 

review.

Occupational

Handlers (mixers, loaders, 

applicators)

Y

Post-application Y

Residential

Handlers Y

Post-application Y

Other

Aggregate TBD Evaluates the combined risk from dietary 

and residential exposures. If there are no 

changes to toxicological endpoints or points 

of departure or EDWCs, then results from 

the last dietary assessment will be used for 

registration review.

Cumulative N

Tolerances Y The Agency anticipates revising the 

tolerance expression for chlorothalonil in 40 

CFR §180.275(a)(1) and §180.275(a)(2) 

during registration review to ensure that it 

appropriately covers the metabolites and 

degradates of chlorothalonil and that it 

specifies the residues to be measured in each 

commodity.

Incidents Y For a discussion of chlorothalonil’s reported 

human incidents, see page 20 of the Scoping 

Document.
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TIMELINE

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

registration review. The projected timeline has not changed since the PWP.

Registration Review for Chlorothalonil– Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period 2012 – March -

Completed

Close Public Comment 2012 – May -

Completed

Case Development

Final Work Plan 2012 – Aug. –

Sept. -

Completed

Issue DCI 2013 – April –

June

Data Submission 2015 – April –

June

Open 30-day Public Comment Period for Draft Risk Assessments 2016 – Oct. –

Dec.

Close Public Comment Period 2017 – Jan. –

March

Registration Review Decision

Open 60-day Public Comment Period for Proposed Registration 

Review Decision 

2017 – April –

June

Close Public Comment Period 2017 – July –

Sept.

Registration Review Decision and Begin Post-Decision Follow-up 2018

Total (years) 6

NEXT STEPS

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

and human health studies for chlorothalonil through a data call-in, expected to be issued in 2013.