Docket Number: EPA-HQ-OPP-2010-0923 

www.regulations.gov

Chlorpropham Final Work Plan 

Registration Review 

June 2011 

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CHLORPROPHAM FINAL WORK PLAN 

Introduction: 

This is the Environmental Protection Agency’s (EPA’s) Final Work Plan for the 

registration review of chlorpropham. This work plan includes the expected registration 

review timeline. The work plan also addresses public comments received concerning the 

Preliminary Work Plan (PWP) in the Summary Document, which was posted in the 

chlorpropham registration review docket (EPA-HQ-OPP-2010-0923), and any other 

comments concerning the initial docket postings. The Summary Document provided 

information on what EPA knows about the pesticide and what additional risk analyses 

and data or information the Agency believes are needed to make a registration review 

decision. 

The Agency is implementing the registration review program and will review each 

registered pesticide every 15 years to determine whether it continues to meet the Federal 

Insecticide, Fungicide, and Rodenticide Act (FIFRA) standard for registration. Changes 

in science, public policy, and pesticide use practices will 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 at: 

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

Chlorpropham (Case 0271) is a carbamate plant growth regulator registered for use for 

sprout control on post-harvest, stored potatoes. Chlorpropham is not an N-methyl 

carbamate and does not share a common mechanism of toxicity with the N-methyl 

carbamate group. Also, Special Local Need (SLN) registrations for chlorpropham allow 

chlorpropham use to prevent bud formation on ginkgo trees in Washington, D.C. and to 

prevent bud formation and control Botrytis on Easter lilies in California and Oregon. 

There are currently no residential uses for chlorpropham. The Reregistration Eligibility 

Decision (RED) for Chlorpropham was completed in October 1996 and the Report of 

FQPA Tolerance Reassessment Progress and Interim Risk Management Decision 

(TRED) for Chlorpropham was completed in September 2002.

Updates since Preliminary Work Plan was Issued: 

After further review of the existing ecological data available for chlorpropham, the 

Agency has determined that environmental chemistry methods and associated 

independent laboratory validations for soil and water are necessary to complete the 

forthcoming ecological risk assessment for registration review. These data requirements 

were not specified in the Preliminary Work Plan or in the Registration Review: 

Preliminary Problem Formulation for Environmental Fate and Ecological Risk, 

Endangered Species, and Drinking Water Exposure Assessments for Chlorpropham, 

dated November 4, 2010. These additional data requirements are reflected in this Final 

Work Plan. 
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For further details regarding changes to the data requirements refer to the Followup to 

EFED’s Response to Comments on Chlorpropham: Outstanding Data Gaps, dated May 

26, 2011, which can be located in the chlorpropham registration review docket (EPAHQ-OPP-2010-0923). 

Comments Received on Preliminary Work Plan: 

The chlorpropham registration review docket was open for a 60-day comment period 

beginning on December 22, 2010. During the public comment period the Agency 

received multiple comments from Keim Aerosol Technologies and by Technology 

Sciences Group, Inc. The comments received did not change the planned risk 

assessment, data needs or the timeline detailed in the chlorpropham Preliminary Work 

Plan (PWP). EPA also solicited comments, through the PWP, on three specific topics: 

environmental justice, water body impairment, and trade irritants. No comments or 

information were received during the comment period concerning these issues. Further, 

this document makes final the work plan for the chlorpropham registration review 

process. 

A general overview of the comments and the Agency’s responses to the comments are 

presented in the Summary of Comments and Agency Responses section of this document. 

Risk Assessment and Data Needs: 

The Agency will conduct a comprehensive ecological risk assessment, including an 

endangered species assessment, and intends to update the existing human health risk 

assessments for all uses of chlorpropham. The Agency will require data in order to 

conduct the planned human health and ecological risk assessments. Below is a summary 

of the ecological and human health issues relevant to the registration review of 

chlorpropham: 

Ecological Risk: 

• The most recent ecological assessment for chlorpropham was completed in 1996 

in support of the chlorpropham Reregistration Eligibility Decision (RED). 

• An ecological risk assessment of all registered uses of chlorpropham will be 

conducted during registration review. The new assessment will incorporate the 

most up-to-date modeling methodologies, updated toxicological endpoints, and 

data submitted under the anticipated registration review data call-in. 

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

endangered species determination for chlorpropham. The ecological risk 

assessment planned during registration review will allow the Agency to determine 

whether chlorpropham 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 
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listed species or its designated critical habitat, the Agency will consult with the 

U.S. Fish and Wildlife Service and/or National Marine Fisheries Services (the 

Services), as appropriate. 

• The Agency will require the following data in order to conduct the planned 

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

uses: 

 Guideline No. 835.1230 – Sediment and Soil Absorption/Desorption 

 Guideline No. 835.1240 – Soil Column Leaching 

 Guideline No. 835.4100 – Aerobic Soil Metabolism 

 Guideline No. 835.6100 – Environmental chemistry method and 

associated independent laboratory validation for soil 

 Guideline No. 835.6200 – Environmental chemistry method and 

associated independent laboratory validation for water 

 Guideline No. 850.1300 – Daphnid Chronic Toxicity 

 Guideline No. 850.1400 – Fish Early-Life Stage Toxicity, freshwater 

 Guideline No. 850.2100 – Avian Acute Oral Toxicity, Passerine 

 Guideline No. 850.2300 – Avian Reproduction

 Guideline No. 850.4100 – Nontarget Area Phytotoxicity Tier II, Seedling 

emergence

 Guideline No. 850.4150 – Nontarget Area Phytotoxicity Tier II, 

Vegetative vigor

 Guideline No. 850.4400 – Nontarget Area Phytotoxicity Tier II, Aquatic 

Plant Growth (Vascular plants) 

 Guideline No. 850.5400 – Nontarget Area Phytotoxicity Tier II, Aquatic 

Plant Growth (Algal plants) 

• Please refer to the Registration Review: Preliminary Problem Formulation for 

Environmental Fate and Ecological Risk, Endangered Species, and Drinking 

Water Exposure Assessments for Chlorpropham, dated November 4, 2010; the 

Followup to EFED’s Response to Comments on Chlorpropham: Outstanding 

Data Gaps, dated May 26, 2011; and the Environmental Fate and Effects Division 

Response to Comments on Registration Review Problem Formulation for 

Chlorpropham, dated April 14, 2011, located in the registration review docket 

(EPA-HQ-OPP-2010-0923) for a detailed discussion of the risk assessment and 

data needs. 

Human Health Risk: 

• The most recent human health risk assessment, including an updated drinking 

water assessment, was completed in 2002 in support of the chlorpropham TRED. 

• During registration review, the Agency will conduct a new drinking water 

assessment for the Easter lily use and the amount of chlorpropham that deposits 

from the aerial release into the environment from the stored potato use. 
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• The Agency will conduct a new dietary risk assessment, incorporating refined 

estimated drinking water concentrations (EDWCs), updated anticipated residues, 

and Pesticide Data Program (PDP) data. 

• The chlorpropham tolerance expression will be reviewed during registration 

review to ensure that it appropriately covers the metabolites and degradates of 

chlorpropham and that it specifies the residues to be measured for each 

commodity. 

• The residue chemistry database is sufficient to support the current registrations; 

however, there are some outstanding data requirements concerning the analytical 

methods. These data were required by a previous Data Call-In (DCI) for 

chlorpropham issued in April 1994. These data, when submitted and found 

acceptable, will complete the residue chemistry data requirements for 

chlorpropham. The, outstanding data are: 

 Guideline No. 171-4d – Residue Analytical Method - Animal: A revised 

analytical method for tolerance enforcement in stored potato commodities. 

The Agency is currently reviewing data submitted to fulfill the 

requirement for Residue Analytical Method – Animal. If this data is 

found acceptable, no further submissions will be necessary to fulfill this 

requirement. 

 Guideline No. 171-4j – Magnitude of Residue in meat/milk/poultry/egg: 

Independent laboratory validation for the enforcement method to detect 

chlorpropham and its 4-HAS metabolite in meat and milk. 

 For the Magnitude of Residue in meat/milk/poultry/egg data requirement, 

an analytical detection method was submitted to the Agency and found to 

be scientifically acceptable. However, the method did not include an 

independent laboratory validation (ILV). The data requirement will be 

considered fulfilled when an acceptable ILV is submitted. The technical 

registrants for chlorpropham have been made aware of this deficiency. 

• Occupational exposures have not been previously assessed for airblast application 

to ginkgo trees and for the post-application use on Easter lilies. In addition, the 

previously assessed occupational handler exposure scenarios did not include 

estimates of inhalation exposure. Therefore, the Agency will be conducting a 

revised occupational exposure assessment during registration review. 
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• The toxicity database is complete with the exception of the following studies, 

which the Agency will be requiring in order to conduct a complete human health 

assessment: 

 Guideline No. 870.3465 – 90-day Inhalation-Toxicity 

 Guideline No. 870.6200 – Acute and Subchronic Neurotoxicity 

 Guideline No. 870.7800 – Immunotoxicity 

Please refer to the Chlorpropham. Human-Health Assessment Scoping Document in 

Support of Registration Review, dated November 2, 2010; and the Chlorpropham. Public 

Comments Regarding the Health Effects Division’s (HED’s) Human-Health Assessment 

Scoping Document in Support of Registration Review of 02-NOV-2010. HED’s Response 

to Public Comments, dated May 17, 2011, located in the registration review docket (EPAHQ-OPP-2010-0923) for a detailed discussion of the 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 

reregistration decision, EPA reviewed these data and selected the most sensitive 

endpoints for relevant risk assessment scenarios from the existing hazard database. 

However, as required by FFDCA section 408(p), chlorpropham 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 
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of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. 

Chlorpropham is not among the group of 58 pesticide active ingredients on the initial list 

to be screened under the EDSP. Accordingly, as part of registration review, EPA will 

issue future EDSP orders/data call-ins, requiring the submission of EDSP screening 

assays for chlorpropham. 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: 

EPA has created the following timeline for completion of the registration review for 

chlorpropham. 

Registration Review for Chlorpropham – Registration Review Timeline

Activities Estimated Date 

Opening the Docket 

Open Docket and Public Comment Period 2010 – December 

Close Public Comment 2011 – February 

Case Development 

Final Work Plan 2011 – June 

Issue DCI 2012 – Jan. – March 

Data Submission 2014 – Jan. – March 

Open Public Comment Period for Draft Risk Assessments 2015 – July – Sept. 

Close Public Comment Period 2015 – Oct. – Dec. 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

 2016 – Jan. – March 

Close Public Comment Period 2016 – April – June 

Registration Review Decision and Begin Post-Decision Follow-up 2016 

Total (years) 6 

Summary of Comments & Agency Responses: 

The chlorpropham registration review docket was open for a 60-day comment period 

beginning on December 22, 2010. During the comment period, multiple comments were 

submitted by Keim Aerosol Technologies (Keim) and by Technology Sciences Group, 

Inc. (TSG). The comments received do not change the risk assessment, data needs or the 

timeline detailed in the chlorpropham Preliminary Work Plan (PWP). A general 

summary of these comments and the Agency’s response to comments are provided 

below. 

For a detailed description of the comments received and the Agency’s response to these 

comments please refer to the following two documents: Chlorpropham. Public 

Comments Regarding the Health Effects Division’s (HED’s) Human-Health Assessment 

Scoping Document in Support of Registration Review 02-NOV-2010. Chlorpropham. 
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Public Comments Regarding the Health Effects Division’s (HED’s) Human-Health 

Assessment Scoping Document in Support of Registration Review of 02-NOV 2010. 

HED’s Response to Public Comments, dated May 17, 2011; and Environmental Fate and 

Effects Division Response to Comments on Registration Review Problem Formulation for 

Chlropropham, dated April 14, 2011. These documents are available in the 

chlorpropham docket (EPA-HQ-OPP-2010-0923). 

Keim Aerosol (Keim) Technologies

Keim Comments on Ecological Risk: 

Concerning ecological risk, Keim’s comments dealt primarily with the Agency’s 

assumption that chlorpropham may be released into the environment after use in sealed 

potato storage facilities. 

Agency Response: 

Currently, the Agency assumes that some chlorpropham may be released into the 

environment as a result of the stored potato use. However, if submitted, the Agency will 

consider monitoring data on releases of chlorpropham following the indoor stored potato 

use. 

Keim Comments on Human Health Risk: 

Concerning human health risk, Keim Aerosol’s comments dealt primarily with the 

Agency’s assumptions concerning worker risk, dietary exposure to chlorpropham 

residues, and current application methodologies. Keim asserts that current assessment 

assumptions are inadequate to address the human health risks posed by chlorpropham. 

Additionally, Keim commented on the need for chlorpropham product labels to provide 

guidance on how to prevent fires and explosions during treatment in potato storage 

facilities. 

Agency Response: 

For a detailed discussion of the Agency’s response to Keim’s comments please refer to 

the Chlorpropham. Public Comments Regarding the Health Effects Division’s (HED’s) 

Human-Health Assessment Scoping Document in Support of Registration Review of 02-

NOV 2010. HED’s Response to Public Comments, dated May 17, 2011, located in the 

chlorpropham registration review docket. In its response document, the Agency 

addresses the deficiencies Keim claims exist in the Agency’s assessment assumptions and 

methodologies. Detailed descriptions of how the Agency assesses various facets of 

dietary and occupational risk are also provided. Additionally, the Agency clarifies label 

use directions and describes the reliability of common sources of data used for risk 

assessment, such as the USDA Pesticide Data Program. 
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In response to Keim’s comment regarding product label guidance, the Agency notes that 

during the Agency’s review process for product labels, those products whose chemistry 

data indicate a potential flammability concern are required to include precautionary 

language on their labels. Additional information is available in Chapter 9 in the EPA 

Label Review Manual (http://www.epa.gov/oppfead1/labeling/lrm/chap-09.pdf).

Technology Sciences Group Inc. (TSG)

TSG Comments on Ecological Risk: 

Concerning ecological risk, TSG questioned the Agency’s assumption that chlorpropham 

may be released into the environment after use in sealed potato storage facilities. TSG 

also noted that their members do not have chlorpropham products registered for any uses 

other than the indoor potato use. TSG did not believe that any of the fate and ecological 

data requirements described in the PWP were applicable to assessment of ecological risk 

resulting from the potato use. 

Agency Response:

The Agency thanks TSG for their comments; however, they do not alter the Agency’s 

assumption that the indoor potato storage use of chlorpropham may result in release of 

chlorpropham into the environment, and, therefore, the identified fate and ecological data 

outlined in this Final Work Plan are required in order to support the planned ecological 

risk assessment. However, if submitted, the Agency will consider monitoring data on 

releases of chlorpropham following the indoor potato storage use. 

TSG Comments on Human Health Risk: 

Concerning human health risk, TSG’s comments dealt with the Agency’s proposed data 

requirements and worker exposure assumptions. TSG cited several studies they felt may 

address data gaps identified in the PWP. Additionally, TSG commented that, since their 

products are only registered for use indoors on stored potatoes, several of the studies 

were unnecessary to assess risk for the potato use. 

Agency Response: 

Due to the potential for occupational exposure from the stored potato use, the data that 

the Agency plans to require for the human health assessment did not change as a result of 

the comments. TSG cited several studies which may provide some information on 

neurotoxicity and immunotoxicity. However, studies not specifically conducted to assess 

these toxcicological endpoints may be inadequate to characterize a pesticide’s potential 

neurotoxicity or immunotoxicity. The Agency plans to require the toxicological data 

described in the PWP. 
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Next Steps: 

The Agency plans to develop a Data Call-In Notice for this pesticide and plans to issue it 

in early 2012. This new information will be used to conduct risk assessments for 

chlorpropham uses. 

Summary of Data Gaps – Chlorpropham:

The table below summarizes all data needs for chlorpropham identified in the Ecological 

Risk and Human Health Risk sections of this Final Work Plan document, the Registration 

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

Endangered Species, and Drinking Water Exposure Assessments for Chlorpropham,

dated November 4, 2010, the Followup to EFED’s Response to Comments on 

Chlorpropham: Outstanding Data Gaps, dated May 26, 2011, and the Chlorpropham. 

Human-Health Assessment Scoping Document in Support of Registration Review, dated 

November 2, 2010. 

Guideline 

Number Data Needs 

Test 

Material 

Estimated 

Timeframe 

(Measured in 

Months from 

DCI Receipt) 

REGISTRATION REVIEW DCI STUDIES 

835.1230 Sediment and soil absorption/desorption for parent and 

degradates TGAI1

 12 

835.1240 Soil Column Leaching TEP2 12 

835.4100 Aerobic Soil Metabolism TGAI 24 

835.6100 Environmental chemistry method and associated 

independent laboratory validation for soil 3 TGAI 12 

835.6200 Environmental chemistry method and associated 

independent laboratory validation for water 3 TGAI 12 

850.1300 Daphnid Chronic Toxicity TGAI 12 

850.1400 Fish Early-Life Stage Toxicity, freshwater TGAI 12 

850.2100 Avian Acute Oral Toxicity, passerine TGAI 12 

850.2300 Avian Reproduction TGAI 24 

850.4100 Nontarget Area Phyotoxicity Tier II, Seedling 

Emergence4 TEP 12 

850.4150 Nontarget Area Phyotoxicity Tier II, Vegetative Vigor4 TEP 12 

850.4400 Nontarget Area Phyotoxicity Tier II, Aquatic Plant 

Growth (Vascular plants)4 TEP 12 

850.5400 Nontarget Area Phyotoxicity Tier II, Aquativ Plant 

Growth (Algal Plants)4 TGAI or 12 

 

1 Technical Grade Active Ingredient.

2 Typical End use Product.

3 See footnote 7 of 40 CFR 158.1300. EPA will require only the environmental chemistry analytical method portion of 

GLNs 835.6100 ,Terrestrial field dissipation and 835.6200, Aquatic field dissipation. 4

 A Tier II study will be required. The DCI to be issued will provide that a Tier I plant study may be conducted in lieu 

of a Tier II study with the understanding that any adverse effects observed by the Tier I study would necessitate 

conduct and submission of a Tier II study as well. 
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Guideline 

Number Data Needs 

Test 

Material 

Estimated 

Timeframe 

(Measured in 

Months from 

DCI Receipt) 

TEP 

870.3465 90-Day Inhalation Toxicity5 TGAI 24 

870.6200 Acute and Subchronic Neurotoxicity TGAI 12 

870.7800 Immunotoxicity TGAI 12 

 OUTSTANDING DATA FROM GDCI-018301-17113 

171-4d Residue analytical method - animal 12 

171-4j Magnitude of residue - meat/milk/poultry/egg 18 

 

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 While the inhalation guideline calls for a 90-day study duration, a 28-day study duration will satisfy the Agency’s 

inhalation exposure data needs.