Docket Number EPA-HQ-OPP-2011-0840 

www.regulations.gov

Chlorothalonil 

Summary Document 

Registration Review: Initial Docket 

March 2012 

3 

TABLE OF CONTENTS 

 

I. Preliminary Work Plan (PWP) 4 

II. Fact Sheet 14 

III. Summary of Data Gaps 21 

 

This Preliminary Work Plan and Fact Sheet summarize the Environmental Protection Agency’s 

current position based on the following documents: 

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

Assessment and Drinking Water Exposure Assessment of Chlorothalonil. March 22, 

2012. 

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

Review. March 13, 2012. 

3. BEAD Chemical Profile for Registration Review: Chlorothalonil (PC Code 081901). 

October 25, 2011. 

4. Chlorothalonil (081901) Screening Level Usage Analysis (SLUA). May 7, 2011. 

5. Chlorothalonil (081901) California DPR Usage Data. October 17, 2011. 

6. PRD Appendix A: Food/Feed & Non-Food/Non-Feed Uses Considered in Registration 

Review Work Planning, Chlorothalonil (081901). September 14, 2011. 

7. Summary of Registered Antimicrobial Uses of Chlorothalonil in Support of the 

Registration Review Summary Document. March 12, 2012 

Supporting documents for the registration review of chlorothalonil are located in docket EPAHQ-OPP-2011-0840 at www.regulations.gov. 
4 

I. PRELIMINARY WORK PLAN 

Introduction

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 at: http://www.epa.gov/oppsrrd1/registration_review/. 

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 Agency will consider benefits information and data as required by FIFRA. 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 chlorothalonil. 

Chlorothalonil is a pesticide active ingredient that was first registered in the United States in 

1966 for use as a fungicide on turfgrass. The first food crop registration was in 1970 for potato 

use and the first antimicrobial use was registered in 1974 as a mildewcide in latex and solventbased paints. There are 134 registered products containing chlorothalonil at this time, 103 

conventional pesticide products and 31 antimicrobial pesticide product registrations. 

Chlorothalonil is registered for a variety of conventional uses, including food and ornamental 

crops in both agricultural and residential sites. Additional conventional uses include nonresidential 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 Reregistration Eligibility Decision (RED) for chlorothalonil was 

issued in 1999, in which the Agency concluded that a variety of mitigation measures were 

necessary to continue the registration of chlorothalonil pesticide products. 

Anticipated Risk Assessment and Data Needs

The Agency anticipates requiring data for use in conducting new ecological (including an 

endangered species) and human health risk assessments for all registered uses of chlorothalonil. 
5 

Below is a summary of the issues relevant to the registration review of chlorothalonil and the 

data the Agency anticipates requiring. 

Ecological Risk: 

 The Agency anticipates the need to conduct a new comprehensive ecological risk 

assessment for all uses of chlorothalonil for registration review. 

 The registration review ecological risk assessment for chlorothalonil will consider effects 

to non-target organisms from chlorothalonil, degradates of concern, impurities, spray 

drift, atmospheric long-range transport and runoff. Additionally, the Agency intends to 

assess risk from down-the-drain exposure (manufacturing of wood preservatives) and inuse/lifetime exposure (leaching from treated wood) from the antimicrobial uses of 

chlorothalonil.

 In the registration review ecological risk assessment, incident reports will be evaluated to 

determine if the reported incidents represent current patterns of use for chlorothalonil. 

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

species determination for all uses of chlorothalonil. The ecological risk assessment 

planned during registration review will allow the Agency to determine whether 

chlorothalonil’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 

(USFWS) and/or National Marine Fisheries Service (NMFS) (the Services), as 

appropriate. 

 On January 19, 2011, the Center for Biological Diversity and the Pesticide Action 

Network North America filed a lawsuit in the United States District Court for the 

Northern District of California, against the Environmental Protection Agency (EPA) for 

allegedly failing to undergo consultation with the USFWS and NMFS regarding the 

effects of over 350 pesticides, including chlorothalonil, on over 200 endangered and 

threatened species throughout the United States (Center for Biological Diversity, et al. v. 

EPA, et al., No. C 11-00293 (N.D.Cal.). 

 Anticipated data needs exist in the environmental fate and ecological toxicity database for 

chlorothalonil. The Agency anticipates the need to require the following data for use in 

conducting a complete ecological risk assessment, including an endangered species 

assessment, for both conventional and antimicrobial uses of chlorothalonil:

Environmental Fate Data Needs

o Guideline No. 835.1230 Adsorption/desorption 

o Guideline No. 835.1240 Soil column leaching 

o Guideline No. 835. 2120 Hydrolysis 

o Guideline No. 835.2240 Aqueous photolysis 
6 

o Guideline No. 835.4200 Anaerobic soil metabolism 

o Guideline No. 835.4300 Aerobic aquatic metabolism 

o Guideline No. 835.4400 Anaerobic aquatic metabolism 

Ecological Toxicity Data Needs

o Guideline No. 850.1075 Saltwater fish acute toxicity 

o Guideline No. 850.1350 Saltwater invertebrates life cycle 

o Guideline No. 850.1400 Saltwater fish early life stage 

o Guideline No. 850.1735 Freshwater invertebrate acute whole sediment 

toxicity 

o Guideline No. 850.1740 Saltwater invertebrate acute whole sediment 

 toxicity 

 The Agency anticipates the need to require the following data for use in conducting a 

complete ecological risk assessment, including an endangered species assessment, for 

conventional uses of chlorothalonil:

Environmental Fate Data Needs

o Guideline No. 835.4100 Aerobic soil metabolism 

o Guideline No. 835.2370 Air photolysis 

o Guideline No. 835.6100 Terrestrial field dissipation 

o Guideline No. 835.8100 Field volatility 

Ecological Toxicity Data Needs

o Guideline No. 850.2100 Avian acute oral toxicity, passerine 

o Guideline No. 850.4100 Seedling emergence, Tier II 

o Guideline No. 850.4150 Vegetative vigor, Tier II 

o Non-guideline study Avian acute inhalation 

 The Agency anticipates the need to require the following data for use in conducting a 

complete ecological risk assessment, including an endangered species assessment, for 

antimicrobial uses of chlorothalonil:

Data Needs for Assessing Activated Sludge Toxicity 

o Guideline No. 850.6800 Modified activated sludge respiration inhibition 

Environmental Fate Data Needs

o Guideline No. 835.1110 Activated sludge sorption isotherm 

o Guideline No. 850.3110 Ready biodegradation1

 

1

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

which of these three 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 Biodegradation in Activated Sludge Study or Simulation Test – Aerobic Sewage 

Treatment: A. Activated Sludge Units or the Porous Pot Test would be anticipated to be required. If the ASRI test 

EC50 is greater than 20 mg/L, then the applicant would choose to conduct either: 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 
7 

o Guideline No. 850.3220 Porous pot1

o Guideline No. 850.3240 Simulation tests—aerobic sewage treatment: A 

activated sludge1

o Guideline No. 850.3280 Simulation tests to assess the biodegradability of 

chemicals discharged to wastewater1

o Non-guideline study Wood leaching study 

 Given that there are uncertainties in the environmental fate profile for chlorothalonil 

regarding the potential for degradates/transformation products, if additional information 

becomes available, then chlorothalonil and any transformation products deemed to be of 

toxicological concern will be evaluated as part of registration review by incorporating the 

total toxic residue approach when deriving aquatic and terrestrial environmental 

concentrations. 

 The Agency is also seeking additional information on wood preservative facility 

emissions to Wastewater Treatment Plants (WWTP). Facility information that would be 

useful for estimating aquatic exposures from emissions to WWTP from the industrial 

wood preservative process include the following: 

o The number of facilities that pressure treat wood products with chlorothalonil 

o How many of these facilities have on-site and/or off-site wastewater treatment 

 

 Please refer to the March 22, 2012 Registration Review – Preliminary Problem 

Formulation for the Ecological Risk Assessment and Drinking Water Exposure 

Assessment of Chlorothalonil, located in docket EPA-HQ-OPP-2011-0840 at 

www.regulations.gov, for a more detailed discussion of the anticipated ecological risk 

assessment and data needs for chlorothalonil.

Human Health Risk: 

 An updated dietary risk assessment may be needed if there are changes to the endpoints 

as a result of new data, or if there are changes to estimated drinking water concentrations 

(EDWCs), which the Agency anticipates updating during registration review. 

 The Agency anticipates conducting an updated residential exposure assessment to include 

both conventional and antimicrobial uses that were not previously assessed. The updated 

risk assessment may also incorporate any potential changes to the Standard Operation 

Procedures (SOPs) for residential risk assessments, as well as any changes to the 

endpoints as a result of new data. 

 The Agency may conduct an aggregate (dietary food + drinking water + residential) risk 

assessment if there are changes to the toxicological endpoints. 

 Biodegradation in Activated Sludge or Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or 

the Porous Pot study would be expected to be required. 
8 

 The Agency anticipates conducting an updated occupational risk assessment to include 

updated handler exposure surrogate data, as well as formulations and use sites not 

previously assessed. The Agency may also reconsider the use of respirators for highpressure handwand uses and residential paint applications. 

 The Agency anticipates that it may set the FQPA safety factor at 3X for acute and 30X 

for repeated residential inhalation exposure scenarios for registration review due to 

uncertainty regarding inhalation toxicity. The Agency anticipates re-evaluating the FQPA 

Safety Factor based upon submission of anticipated toxicity studies including inhalation, 

acute neurotoxicity, and immunotoxicity studies. 

 The Agency anticipates the need to assess occupational handler exposure from the open 

pouring of wettable powder in the manufacture of antimicrobial products as well as 

occupational exposure that may occur during the dip, spray and pressure treatment of 

wood. 

 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. 

 The Agency intends to modify tolerance levels as needed, and work to harmonize 

tolerances/maximum residue limits (MRLs), where possible, in key export markets 

during registration review. 

 The frequency and severity of human health incidents reported for chlorothalonil may 

warrant further analysis in the registration review of chlorothalonil. 

 The Agency anticipates the need to reconsider chlorothalonil's dermal sensitization 

classification during registration review. In the 1999 RED, chlorothalonil was classified 

as not being a dermal sensitizer; however, a published literature study indicates that 

chlorothalonil may be an extremely potent contact allergen, inducing sensitization. 

 The Agency anticipates the need to require the following toxicity data for use in 

conducting a complete human health risk assessment for conventional and antimicrobial 

uses of chlorothalonil: 

o Guideline No. 870.3465 90-day inhalation toxicity (rat) 

 The Agency anticipates the need to require the following data for the conventional uses 

of chlorothalonil for use in conducting a complete human health risk assessment: 

o Guideline No. 860.1360 Multiresidue method recovery data (degradate SDS- 

 3701) 

o Guideline No. 870.6200 Acute neurotoxicity 
9 

o Guideline No. 870.7800 Immunotoxicity 

 The Agency anticipates the need to require the following human health data for the 

antimicrobial uses of chlorothalonil: 

o Guideline No. 875.1400 Inhalation exposure, indoor2

o Guideline No. 875.1600 Exposure monitoring data reporting 

o Guideline No. 875.1700 Product Use Information 

o Guideline No. 875.2300 Surface residue dissipation 

 Chlorothalonil 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. 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 chlorothalonil as appropriate. 

 Please refer to the March 13, 2012 Chlorothalonil. Human-Health Assessment Scoping 

Document in Support of Registration Review, available in docket EPA-HQ-OPP-2011-

0840 at www.regulations.gov, for a detailed discussion of the anticipated human health 

risk assessment and data needs. 

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 1999 reregistration decision for chlorothalonil, EPA reviewed 

 

2

 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. 
10 

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), chlorothalonil 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. Chlorothalonil was 

included on that list and has been issued an order to conduct the Tier 1 testing. Once all required 

Tier 1 and Tier 2 data have been received and reviewed, the endpoints and safety factors used for 

risk assessment purposes will be examined and a new risk assessment performed if necessary. 

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 

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

Timeline

 

The projected timeline for the completion of the chlorothalonil registration review is presented 

below in Table 1. 

Table 1. Projected Chlorothalonil Registration Review Timeline 

Activity Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period 2012 – March 

Close Public Comment 2012 – May 

Case Development 

Final Work Plan 2012 – August 

Issue DCI 2013 – April – June 

Data Submission 2015 – April – June 

Open Public Comment Period for Draft Risk Assessments 2016 – Oct. – Dec. 

Close Public Comment Period 2017 – Jan. – March 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

 2017 – April – June 

Close Public Comment Period 2017 – July – Sept. 
11 

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

Total (years) 6 

Guidance for Commenters

The public is invited to comment on EPA’s preliminary work plan and rationale. The Agency 

will carefully consider all comments, as well as any additional information or data provided in a 

timely manner, prior to issuing a final work plan for the chlorothalonil case. 

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. Growers and 

other stakeholders are asked to comment on any trade irritant issues resulting from lack of 

Maximum Residue Limits (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. 

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 chlorothalonil 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. 

Water Quality 

Organochlorine pesticides are identified as a cause of impairment for two water bodies listed as 

impaired under section 303(d) of the Clean Water Act as of the water body report completed in 

2010. 3 Although chlorothalonil is sometimes referred to as an organochlorine, it is unclear if 

chlorothalonil is one of the organochlorine pesticides contributing to the water body impairment. 

The two water bodies are in New York: Niagara River, upper, main stem and Niagara River, 

lower, main stem. Total Maximum Daily Loads (TMDL)4

 have not been developed for 

chlorothalonil or organochlorine pesticides. More information on impaired water bodies and 

TMDLs can be found at the Agency’s website5

. 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 

 

3

 http://iaspub.epa.gov/tmdl_waters10/attains_nation.cause_detail_303d?p_cause_group_id=885&p_cycle=2010 

4

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

5 http://www.epa.gov/owow/tmdl/
12 

Process6

 in order to ensure they can be used quantitatively or qualitatively in pesticide risk 

assessments. 

Structure Activity Relationships 

EPA must rely upon information of appropriate quality and reliability for each decision made by 

the Agency. In the Office of Pesticide Programs (OPP), the evaluation process for a pesticide 

chemical traditionally begins with the applicant’s submission of a set of studies conducted with 

the specific pesticide chemical of interest. The use of the results of such testing (measured data) 

is a logical, scientifically rigorous process that identifies the physical, chemical, and 

environmental fate properties of the pesticide, as well as the dose and endpoints at which an 

adverse effect can occur in various animal species. 

Today, there is significant interest in alternative techniques, i.e., techniques other than data 

generation that could significantly inform the Agency’s decision-making process. Recently, OPP 

has made increasing use of structure activity relationship (SAR) as part of its regulatory 

decision-making process. In the SAR process, a chemical's molecular structure is compared to 

that of other chemicals for which data are available. These structural similarities are then used to 

make predictive judgments about a chemical’s physical, chemical, and biological properties. 

Thus, the chemical’s physical, chemical, and biological properties are a function of (or directly 

related to) the chemical’s molecular structure. Quantitative SAR is referred to as QSAR. To 

develop a QSAR, a selected set of measured data on a single physical, chemical, or biological 

property is used to derive a model (an equation) to predict the value of that property. 

Since SAR assessments and QSAR modeling are another set of tools that are available to Agency 

scientists, OPP has begun a process shift that envisions shifting from the current study-by-study 

approach to an approach in which the use of predicted data, generated using validated models, is 

considered along with information from open literature and studies specifically generated under 

Part 161 requirements. All relevant information would be considered as part of a weight-of-theevidence evaluation. 

At this time, EPA believes that for certain endpoints, especially physical/chemical and fate 

properties, that SAR and QSAR might be effectively utilized to fulfill these data requirements 

for many antimicrobial pesticide chemicals. When considering biological properties, at this time, 

EPA believes that SAR and QSAR can be most effectively utilized in the evaluation of 

chemicals that exhibit lower toxicity for human health and/or ecotoxicity parameters. This is 

appropriate because the risk assessment for lower toxicity chemicals can be stream-lined, i.e., a 

screening-level assessment procedure rather than multiple tiers of assessments with progressively 

more data requirements. 

If stakeholders believe that submission of predicted data can fulfill one of the data needs for the 

Chlorothalonil Case, then the Agency invites submission of this information. The submitter 

would be expected to supply a rationale describing the utility of the information and provide 

documentation on the scientific validity of the information. The determination that the predicted 

 

6 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
13 

data fulfills the data requirement would be at the sole discretion of the Agency. Pre-submission 

consultation with the Agency is encouraged. 

Other Information 

Stakeholders are also specifically asked to provide information and data that will assist the 

Agency in refining risk assessments, including any species-specific ecological effects 

determinations for chlorothalonil. The Agency is interested in receiving the following 

information: 

1. confirmation on the following label information 

a. frequency of application, application intervals, and maximum number of 

applications per season 

b. geographic limitations on use 

2. use or potential use distribution (e.g., acreage and geographical distribution of relevant 

crops) 

3. use history 

4. median and 90th percentile reported use rates (lbs. a.i./acre) from usage data – national, 

state, and county 

5. application timing (date of first application and application intervals) by crop – national, 

state, and county 

6. sub-county crop location data 

7. usage/use information for non-agricultural uses (e.g., forestry, residential, rights-of-way) 

8. directly acquired county-level usage data (not derived from state level data) 

a. maximum reported use rate (lbs. a.i./acre) from usage data – county 

b. percent crop treated – county 

c. median and 90th percentile number of applications – county 

d. total pounds per year – county 

e. the year the pesticide was last used in the county/sub-county area 

f. the years in which the pesticide was applied in the county/sub-county area 

9. typical application interval (days) 

10. state or local use restrictions 

11. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency 

12. monitoring data, air or water 

13. amount of impurities present in technical chlorothalonil 

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 chlorothalonil.
14 

II. FACT SHEET 

Background Information

 Registration Review Case Number: 0097 

 Pesticide Chemical (PC) Code: 081901 

 Chemical Abstracts Service (CAS) Number: 1897-45-6 

 Chlorothalonil was first registered in the United States in 1966 for use as a fungicide on 

turfgrass. The first food crop registration was in 1970 for potato use and the first 

antimicrobial use was registered in 1974 as a mildewicide in latex and solvent-based 

paints. 

 The Reregistration Eligibility Decision for chlorothalonil was completed in April 1999. 

 Technical registrants (conventional with antimicrobial uses): GB Bioscience Corporation, 

Sipcam Agro USA, Inc., Vischim SRL & Celcius Property B.V. 

 Technical registrants (conventional pesticides only): Arysta LifeScience & Orion ATO 

 Technical registrants (antimicrobial only): IBC Manufacturing Corporation & GB 

Bioscience Corporation 

 Active Section 3 registrations as of February 2012 

o Conventional: 103 

o Antimicrobial: 31 

 U.S. tolerances for chlorothalonil: 40 CFR §180.275. 

 Pesticide Re-evaluation Division Chemical Review Manager (CRM): Jose Gayoso, 

gayoso.jose@epa.gov 

 Antimicrobials Division CRM: Rebecca von dem Hagen, vondemhagen.rebecca@epa.gov 

 Registration Division Product Manager (PM): Tony Kish, kish.tony@epa.gov 

 Antimicrobials Division PM: Marshall Swindell, swindell.marshall@epa.gov 

 Chemical Structure: 

 

Use and Usage Information

For additional details, please refer to BEAD Chemical Profile for Registration Review: 

Chlorothalonil (PC Code 081901), dated October 25, 2011; Chlorothalonil (081901) Screening 

Level Usage Analysis (SLUA), dated May 7, 2011; Chlorothalonil (081901) California DPR 

Usage Data, dated October 17, 2011; PRD Appendix A: Food/Feed & Non-Food/Non-Feed Uses 

Considered in Registration Review Work Planning. Chlorothalonil (081901), dated September 

14, 2011; and Summary of Registered Antimicrobial Uses of Chlorothalonil in Support of the 

Registration Review Summary Document, dated March 12, 2012, located in docket EPA-HQOPP-2011-0840 at www.regulations.gov. 
15 

 Chlorothalonil is registered for agricultural use on many food crops, including almonds, 

apples, apricots, asparagus, barley, numerous bean crops, cole crops, cucurbit/melon 

crops, mint, onions, okra, peanuts, peppers, stone fruit crops, potatoes, tomatoes, walnuts, 

and wheat. 

 Chlorothalonil is registered for a variety of non-agricultural uses. Residential uses include 

many ornamental plants (both foliar and bulbs) and home fruit and vegetable gardens. 

Residential antimicrobial uses include paints, wood preservatives, caulks, and sealants. 

 Other non-agricultural registered uses of chlorothalonil include numerous turf grass 

species (including, but not limited to, golf courses), forest nursery trees, as well as 

antimicrobial uses on various industrial and building products including adhesives, 

coatings, concrete blocks and surfaces, emulsions, grouts, irrigation systems, lumber, 

paints, plaster, polishes, stains, stucco, construction timber, and wood building materials. 

 Chlorothalonil products are formulated in solid form as dust, water dispersible granules, 

pellets, tablets, impregnated material, and wettable powder; in liquid form as 

emulsifiable, flowable, or soluble concentrates, as well as ready-to-use solutions. Some 

products are coformulated with other pesticide active ingredients. 

 The annual total agricultural usage of chlorothalonil averaged approximately 9 million 

pounds active ingredient (lbs. a.i.) for the period 1998-2010. The crops with the most use 

in terms of lbs. a.i. applied are peanuts (37%), potatoes (26%), and tomatoes (8%). The 

crops with the greatest total area treated are peanuts (42%), potatoes (31 %), and 

tomatoes (6%). 

 On average, the states with the most agricultural usage in terms of lbs. a.i. applied are 

Georgia (25%), Florida (13%), California (9%), Michigan (8%), and Alabama (7%).

 Non-agricultural annual total conventional chlorothalonil usage for the period 2000-2006 

was reported to be approximately 4.3 million lbs. a.i. The highest use was reported on 

golf courses, with approximately 3 million lbs. a.i. 

 Usage data are unavailable for antimicrobial uses of chlorothalonil, including 

paints/adhesives/caulking/coating, commercial/institutional/industrial buildings, 

composition board and concrete surfaces, and use as a wood preservative. 

Recent and Pending Actions

 There are no recent or pending new use registration actions for chlorothalonil. 

Ecological Risk Assessment Status

The following are key findings from the most recent ecological risk assessments regarding the 

environmental fate, ecological effects, and risks of chlorothalonil. Please refer to the 

Registration Review – Preliminary Problem Formulation for the Ecological Risk Assessment and 
16 

Drinking Water Exposure Assessment of Chlorothalonil, March 22, 2012, located in docket 

EPA-HQ-OPP-2011-0840 at www.regulations.gov, for a detailed discussion. 

 The most recent ecological risk assessment for conventional uses of chlorothalonil was 

conducted in 2010 to assess risk from an IR-4 petition for use on bulb vegetables, 

bushberries, and low growing berries. 

 The most recent comprehensive ecological risk assessment for all conventional uses of 

chlorothalonil was conducted in support of the 1999 Reregistration Eligibility Decision 

(RED) for chlorothalonil. 

 A quantitative ecological risk assessment for the antimicrobial uses of chlorothalonil has 

not been conducted. 

Ecological Effects: 

 The 2010 assessment concluded that the levels of concern were exceeded for all size 

classes of birds and mammals, fish, aquatic invertebrates, and non-vascular aquatic 

plants. Endangered terrestrial invertebrates were at risk from the proposed bulb vegetable 

use. 

 The 1999 RED concluded that levels of concern, especially for aquatic organisms, were 

exceeded for a number of crops, including peanuts and potatoes, as well as turf use. In 

addition, many chlorothalonil labels did not provide specific maximumapplication rate s. 

Marine/estuarine mollusks were particularly at risk. To mitigate ecological risks, the 

registrants agreed to reduce individual and seasonal maximum application rates for many 

use sites. In addition, the registrants agreed that labels would require untreated buffers 

between estuarine/marine water bodies and agricultural crops treated with chlorothalonil–

at least 150 feet for aerial and air-blast applications and 25 feet for ground applications. 

Human Health Risk Assessment Status

The following are key findings from the most recent human health risk assessments conducted 

for chlorothalonil registered uses. Please refer to Chlorothalonil. Human-Health Assessment 

Scoping Document in Support of Registration Review, March 13, 2012, located in docket EPAHQ-OPP-2011-0840 at www.regulations.gov, for a detailed discussion of the human health risk 

assessment status. 

 The most recent human health risk assessment was conducted in 2010 to assess risk from 

an IR-4 petition for use on bulb vegetables, bushberries, and low growing berries. The 

Agency was not able to make a safety finding due to residential/non-occupational and 

occupational inhalation toxicity concerns and the petition was withdrawn. The most 

recent comprehensive human health risk assessment for chlorothalonil was conducted in 

support of the 1999 RED for chlorothalonil. 
17 

Hazard Characterization: 

 The oral and inhalation routes of exposure are of the most toxicological concern with 

chlorothalonil. 

 Chlorothalonil is in acute Toxicity Category IV (the least toxic of four categories) for the 

oral route of exposure, and in Toxicity Category II for the inhalation route. For acute 

dermal effects and acute skin irritation, chlorothalonil is in Toxicity Category IV. 

Chlorothalonil produces severe eye irritation in rabbits (Toxicity Category I). The 

Agency has classified chlorothalonil as a likely human carcinogen (formerly Group B2). 

The mechanistic data, including the negative findings of all genetic toxicology testing, 

supported a non-neoplastic pathology as directly related to the eventual neoplasia and a 

non-linear mode of action for tumor production by chlorothalonil. 

 SDS-3701, the major metabolite of chlorothalonil, is in acute Toxicity Category II for the 

oral route of exposure. There is no evidence of carcinogenicity for the SDS-3701 

metabolite. 

 Hexachlorobenzene (HCB) is an impurity present in chlorothalonil and other pesticide 

products. It is classified as a B2 carcinogen. 

 In the 1999 RED, the Agency decided to remove the 10X FQPA safety factor. However, 

for registration review, the Agency anticipates updating the FQPA safety factors. 

Summary of Risks: 

Dietary

 The most recent non-cancer dietary assessment (food and water) conducted in 2010 was a 

screening level assessment and did not indicate risk estimates of concern from exposure 

to chlorothalonil and degradate SDS-3701. The dietary assessment in the RED also 

concluded that there were no dietary risks of concern from exposure to chlorothalonil and 

SDS-3701. 

 The dietary assessment conducted for the RED found that cancer risks exceeded the level 

of concern for combined dietary exposure to HCBs found in chlorothalonil and several 

other pesticide active ingredients. To mitigate this risk, the chlorothalonil registrants 

agreed to reduce the level of HCB in chlorothalonil technical and manufacturing-use 

products to 40 ppm, which is the lowest level that has been shown to be technologically 

feasible for chlorothalonil.

Residential 

 In the 2010 risk assessment, inhalation risk concerns for the short-/intermediate-term 

exposure durations were identified for residential handlers using treated paint. 

Additionally, risk concerns were identified for post-application scenarios from inhaling 

vapors from treated paint, and for bystander volatilization inhalation exposure. 
18 

 In the RED, residential handlers were estimated to be at risk from exposure to 

chlorothalonil from using certain equipment on turf. Additionally, post-application 

exposure risks were estimated for residents and children exposed to contact with treated 

lawns. To mitigate risk to residential handlers of pesticides containing chlorothalonil and 

children who are exposed to chlorothalonil after application to home lawns, the 

registrants agreed to prohibit home lawn use on chlorothalonil labels. 

Aggregate

 An aggregate (dietary food + drinking water + residential exposure) risk assessment was 

performed in support of the 2010 human health risk assessment for chlorothalonil. 

Aggregate risk was determined to be equal to dietary food + drinking water risk because 

the toxicological endpoints for dietary exposure (kidney effects) and residential 

inhalation exposure (respiratory irritation clinical signs) could not be combined. 

Occupational

 In the latest risk assessment, inhalation risk concerns for occupational handlers were 

identified for both acute and short-/intermediate-term exposures. 

 In the RED, occupational handlers were estimated to be at risk from the following 

scenarios: (1) applications of wettable powder formulations, (2) granular applications 

with tractor-drawn spreaders to turf, (3) applications with specialty air-assisted 

equipment on golf courses, and (4) professional painters using sprayers. Additionally, 

post-application exposure risk exceeded the level of concern for workers re-entering 

treated sodfarm areas to cut, roll, and harvest sod. The Agency determined that the 

restricted entry interval (REI) for agricultural applications could be reduced from 48 

hours to 12 hours, as long as additional measures were taken to protect the eyes for seven 

days after application. To mitigate the risks of concern in the RED, the registrants agreed 

to the following measures: 

o wettable powder formulations must be packaged in water-soluble bags or labeled 

for use only in closed mixing/loading systems 

o MUPs must not be formulated into a product intended as a mildewcidal paint 

additive designed for direct sale to retail customers, e.g., in a ‘pillow pack’ or 

other small volume or one-use package 

o handlers of granular formulations applied with tractor-drawn spreaders to turf 

must wear dust masks 

o applicators using specialty air-assisted application equipment on turf must wear 

chemical-resistant gloves 

o painters using airless sprayers should wear respirators 

o workers who reenter treated areas after the restricted-entry interval, but within 7 

days of treatment, must receive special notification about eye irritation hazards 

and have access to on-site eye-flushing equipment 
19 

o handlers of wettable powder, liquid flowable, and dry flowable formulations, and 

those using hand-held equipment (such as backpack sprayers ) must wear gloves 

o handlers in enclosed spaces (greenhouses) must wear respirators 

o sod treated with chlorothalonil must be harvested, rolled, and palletized 

mechanically. 

Human Studies

 Past chlorothalonil risk assessments relied 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 Pesticide Handlers Exposure 

Database (PHED), the Outdoor Residential Exposure Task Force (ORETF) Database, and 

the Agricultural Reentry Task Force (ARTF) 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. 

Incidents

Ecological Incidents: 

 The most recent review of the chlorothalonil ecological incident reports was conducted in 

November 2011. Between 1976 and 2003, there were 33 chlorothalonil incidents reported 

to the Ecological Incident Information System (EIIS) and the Avian Incident Monitoring 

System (AIMS). In one of the incidents, chlorothalonil was unlikely the cause of the 

incident. Six of the incidents involved misuses or spills. In the remaining 26 incidents, 

the legality of use was either a registered use (5) or undetermined (21) and the certainty 

index was possible (24) or highly probable (2). Of these 26 incidents, 7 involved aquatic 

animals, 4 involved terrestrial animals, and 15 involved plant damage. 

 In addition to the incidents recorded in EIIS and AIMS, 409 aggregate incidents were 

reported to the Agency from 1995 to 2011 (404 involving plants and 5 involving 

animals). 

Human Health Incidents: 

 In the Aggregate OPP Incident Data System (IDS), which contains exposures classified 

as minor, unknown, or no effects outcomes, from January 1, 2006 to November 2, 2011, 

there were 117 reported exposures involving chlorothalonil resulting in low severity. 

There were relatively few details provided on the incidents in the Aggregate IDS module 

and these incidents were of low severity. 
20 

 In the Main IDS, from January 1, 2006 to November 2, 2011, there were 22 exposures 

reported for chlorothalonil only in the database (20 exposure classified as resulting in a 

moderate outcome and 2 classified as major) and 12 additional exposures that involved 

more than one chemical. 

Tolerances and International Harmonization

 U.S. tolerances for chlorothalonil are located at 40 CFR §180.275. 

 A table listing the differences between U.S. tolerances and Canadian, Mexican, and 

CODEX Maximum Residue Limits (MRLs) for chlorothalonil is included in the 

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

Review, March 13, 2012, available in docket EPA-HQ-OPP-2011-0840 at 

www.regulations.gov. 

Labels 

 Active Section 3 labels for chlorothalonil can be obtained from the Pesticide Product 

Label System (PPLS) website: http://oaspub.epa.gov/pestlabl/ppls.home. 
21 

III. SUMMARY OF ANTICIPATED DATA NEEDS 

A summary of the anticipated data needs for the chlorothalonil registration review is presented in 

the tables below. 

Table 2. Summary of Anticipated Data Needs for both Conventional and Antimicrobial 

Uses of Chlorothalonil

Guideline Number Anticipated Data Requirement Test 

Material 

 Estimated 

Timeframe 

 (Measured 

in Months 

from DCI 

Receipt) 

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 

Table 3. Summary of Anticipated Data Needs for Only Conventional Uses of 

Chlorothalonil 

Guideline Number Anticipated Data Requirement 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 

850.4100 Seedling emergence, Tier II TGAI 12 

850.4150 Vegetative Vigor, Tier II TGAI 12 
22 

850.2100 Acute avian oral, passerine1 TGAI 12 

860.1360 Multiresidue method recovery data SDS-3701 12 

870.6200 Acute neurotoxicity TGAI 12 

870.7800 Immunotoxicity TGAI 12 

Non-guideline study 

(Special Study) Avian acute inhalation2 TGAI 12 

Table 4. Summary of Anticipated Data Needs for Only Antimicrobial Uses of 

Chlorothalonil 

Guideline Number Anticipated Data Requirement Test 

Material 

 Estimated 

Timeframe 

 (Measured 

in Months 

from DCI 

Receipt) 

835.1110 Activated sludge sorption isotherm TGAI 12 

850.6800 Modified activated sludge respiration inhibition3 TGAI 12 

850.3110 Ready biodegradation3 TGAI 12 

850.3220 Porous pot3 TGAI 12 

850.3240 Simulation tests—aerobic sewage treatment: A. activated 

sludge3 TGAI 12 

850.3280 Simulation tests to assess the biodegradability of chemicals 

discharged to wastewater3 TGAI 12 

875.1400 Indoor inhalation exposure4 TGAI/TEP 12 

875.1600 Exposure monitoring data reporting TGAI/TEP 12 

875.1700 Product Use Information TGAI/TEP 12 

875.2300 Surface residue dissipation5 TGAI/TEP 24 

 

1

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

initiating this study. 

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

which of these three 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 Biodegradation in Activated Sludge Study or Simulation Test – Aerobic Sewage 

Treatment: A. Activated Sludge Units or the Porous Pot Test would be anticipated to be required. If the ASRI test 

EC50 is greater than 20 mg/L, then the applicant would choose to conduct either: 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 

Biodegradation in Activated Sludge or Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or 

the Porous Pot study would be expected to be required. 

4

 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. 

5

 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. 
23 

Non-guideline study 

(Special Study) Wood leaching study6 TEP 24 

 

6

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

initiating this study.