2

Diclofop-methyl Preliminary Work Plan – Table of Contents

OVERVIEW ................................................................................................................................... 3

ANTICIPATED DATA NEEDS .................................................................................................... 4

STATUTORY AND REGULATORY AUTHORITY................................................................... 5

CHEMICAL FACTS ...................................................................................................................... 5

USE AND USAGE INFORMATION............................................................................................ 6

RECENT ACTIONS....................................................................................................................... 7

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW................................ 7

TIMELINE...................................................................................................................................... 9

NEXT STEPS ............................................................................................................................... 10

References:

This Preliminary Work Plan summarizes the Environmental Protection Agency's current position 

based on the following documents:

1. EFED Registration Review Problem Formulation for Diclofop-methyl. N.E. Federoff and 

Greg Orrick. August 28, 2014.

2. Diclofop-methyl: Human Health Assessment Scoping Document in support of Registration 

Review. Shiela Piper, Yung Yang, and Monica Hawkins. August 5, 2014.

3. Diclofop-methyl: Tier 1 Review of Human Incidents. Shanna Recore. May 29, 2014.

4. BEAD Chemical Profile (BCP) for Registration Review: Diclofop-methyl (110902). Bill 

Phillips, Jihad Alsadek, and Michelle Ranville. April 29, 2014.

5. Diclofop-methyl (110902) Screening Level Usage Analysis (SLUA). March 14, 2014.

These and other supporting documents for the diclofop-methyl registration review case may be 

found in the docket EPA-HQ-OPP-2014-0577 at http://www.regulations.gov.
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OVERVIEW

The docket for diclofop-methyl is now open, initiating the first public comment period for this 

registration review (docket number EPA-HQ-OPP-2014-0577). Diclofop-methyl is a restricted 

use, selective systemic herbicide with contact action registered for the control of wild oats and 

grassy weeds. The agricultural uses of diclofop-methyl include wheat and barley, and nonagricultural uses include golf course turf and roadsides. There are no registered residential uses.

This Preliminary Work Plan (PWP) document explains what EPA's Office of Pesticide Programs

knows about diclofop-methyl, highlighting anticipated data and assessment needs, identifying the 

types of information that would be especially useful to the Agency in conducting the review, and

providing an anticipated timeline for completing the registration review for diclofop-methyl.

The registration review process was designed to include a public participation component to 

solicit input from interested stakeholders. The Agency intends, by sharing this information in the 

docket, to inform the public of what it knows about diclofop-methyl and what types of new data 

or other information would be helpful for the Agency to receive as it moves toward a decision on 

diclofop-methyl. The Agency encourages all interested stakeholders to review the PWP and 

Appendix and to provide comments and additional information that will help the Agency’s 

decision-making process for this chemical. In addition to general areas on which persons may 

wish to comment, there are some areas identified in the PWP and Appendix about which the 

Agency specifically seeks comments and information. Interested stakeholders could include: 

environmental non-profit or interest groups; pesticide manufacturers; agricultural labor or 

commodity groups; commercial, institutional, residential, and other users of pesticides; or the 

public at large.

The Preliminary Work Plan begins by listing the anticipated data needs for diclofop-methyl. 

Next, it discusses the statutory and regulatory authority for Registration Review. Then the 

document provides chemical facts, use and usage information, recent actions, the anticipated risk 

assessments, and a projected registration review timeline for diclofop-methyl. Finally, the 

Appendix to this document includes identification and discussion of some areas that are 

considered generally in Registration Review along with some additional chemical case-specific 

information.
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ANTICIPATED DATA NEEDS

Table 1 below summarizes anticipated data needs for diclofop-methyl. For additional discussion

of the anticipated data needs, see the EFED Registration Review Problem Formulation for 

Diclofop-methy and Diclofop-methyl: Human Health Assessment Scoping Document in support 

of Registration Review.

Table 1: Anticipated Data Needs for the Diclofop-methyl Registration Review

Guideline 

Number1 Study Title1

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

Anticipated Data Needs for the Parent Diclofop-methyl (ester)

835.4300 Aerobic aquatic metabolism: two systems TGAI 24

835.4400 Anaerobic aquatic metabolism: one system TGAI 24

850.1025 Oyster acute toxicity test (shell deposition) TGAI 12

850.1035 Mysid acute toxicity test TGAI 12

850.1075 Fish acute toxicity test, marine TGAI 12

850.3020 Honeybee acute contact toxicity TGAI 12

Non GLN Pollinator acute oral toxicity (honeybee adult) TGAI 12

Non GLN Pollinator acute oral toxicity (honeybee larvae) TGAI 12

850.4500 Algal Toxicity TGAI 12

850.4550 Cyanobacteria Toxicity (Anabaena flos-aquae) TGAI 12

850.6100 Environmental chemistry method and associated 

independent laboratory validation, water TGAI 12

875.2100 Foliar dislodgeable residue dissipation – turf 

transferrable residue TGAI 24

875.2100 Foliar dislodgeable residue dissipation –

dislodgeable foliar residue (wheat, barley) TGAI 24

Anticipated Data Needs for the diclofop acid

850.6100 Environmental chemistry method and associated 

independent laboratory validation, water TGAI 12

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

 

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

– including renumbering and other designations or changes for some guideline studies. See “Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028
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STATUTORY AND REGULATORY AUTHORITY

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 on EPA’s website.

2

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 regulations governing registration review begin at 40 CFR 155.40. 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 a Final Work Plan (FWP) and anticipated schedule for 

the registration review of diclofop-methyl.

CHEMICAL FACTS

Table 2 provides a summary of the chemical facts for diclofop-methyl.

Table 2: Chemical Facts for Diclofop-methyl

PC code 110902

Case Number 2160

CAS Number 51338-27-3

Year first registered 1982

Pesticide Type Herbicide

Chemical class Aryloxphenoxypropionate

Reregistration Eligibility 

Decision (RED)

9/1/2000

Tolerance Reassessment 

Eligibility Decision 

(TRED)

Not applicable; tolerance reassessment was included in the RED

Cumulative group Not applicable; diclofop-methyl has not been identified as a 

member of a cumulative group that shares a common mechanism 

of toxicity.

 

2 http://www.epa.gov/oppsrrd1/registration_review/
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Table 2: Chemical Facts for Diclofop-methyl

40 CFR Citation Tolerances for diclofop-methyl are established in §180.385.

Dual-use Diclofop-methyl is registered for conventional pesticidal uses 

only and has no registered antimicrobial or biopesticidal uses.

Non-pesticidal uses There are no identified non-pesticidal uses of diclofop-methyl.

Pesticide Re-evaluation 

Division, Chemical 

Review Manager

Marianne Mannix, mannix.marianne@epa.gov, (703) 347-0275

Registration Division, 

Product Manager

Kathryn Montague, montague.kathryn@epa.gov, (703) 305-1243

USE AND USAGE INFORMATION

Table 3 summarizes the use and usage information for diclofop-methyl. Please see the BEAD 

Chemical Profile (BCP) for Registration Review: Diclofop-methyl (110902) in the registration 

review docket for more details.

Table 3: Diclofop-methyl Use and Usage Information

Summary of Use Diclofop-methyl is an acetyl CoA carboxylase inhibitor that can 

be applied both preemergence and postemergence to control wild 

oats and grassy weeds. 

Use Sites Agricultural use sites of diclofop-methyl include barley and 

wheat. Diclofop-methyl is registered for non-agricultural use 

sites, including golf courses and roadsides. There are no 

registered residential uses of diclofop-methyl.

Summary of Usage Between 1998 and 2012, an average of approximately 144,000 

lbs/ai of diclofop-methyl was used on approximately 236,000 

acres treated. In 2014, barley and wheat commodities had less 

than one percent crop treated (PCT) with diclofop-methyl. This 

indicates that diclofop-methyl is not heavily relied on to control 

weeds for these crops. Usage data related to the non-agricultural 

uses (golf course turf and roadways) for diclofop-methyl is 

limited and dated.

Formulation Type(s) Diclofop-methyl formulations include emulsifiable concentrate 

and liquid.

Application Method(s) Diclofop-methyl products can be applied by aerial, groundboom, 

or handheld equipment.

Technical Registrant(s) Bayer CropScience

No. of Registrations 3 active Section 3 registrations; 1 Special Local Need registration

Restricted Use Diclofop-methyl is a restricted use pesticide due to 

carcinogenicity in mice.

Guidance for Commenters: Additional areas of use and usage related information

requested for this registration review, and of particular interest to EPA, are described below.
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 Certain diclofop-methyl labels are unclear with respect to reapplication interval for use of 

diclofop-methyl on golf course turf. Without further information, EPA expects to use 

conservative assumptions to approximate these parameters in order to conduct a 

quantitative risk assessment. However, the Agency will work with registrants to clarify 

information on diclofop-methyl product labels.

 Confirmation of the following label information: sites of application; formulations;

application methods and equipment; maximum application rates; frequency of 

application, application intervals, and maximum number of applications per season; and 

geographic limitations on use.

 Use distribution (e.g., acreage and geographical distribution of relevant use sites).

 Median and 90th percentile reported use rates (lbs ai/A) from usage data – national, state, 

and county.

 Typical application timing (date of first application and application intervals) – national, 

state, and county.

 Usage/use information for non-agricultural uses.

 Typical application interval (days).

 State or local use restrictions.

 Foreign technical registrants not listed above who supply technical diclofop-methyl to the 

US market.

RECENT ACTIONS

There are no recent actions for diclofop-methyl.

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW

The most recent comprehensive human health risk assessment for diclofop-methyl was 

completed on August 10, 2000 in preparation for the Reregistration Eligibility Decision. The 

most recent ecological and environmental fate risk assessment was completed on March 22, 2000 

and updated on July 26, 2000 for the same purpose. Findings and conclusions from these risk 

assessments are summarized in the EFED Registration Review Problem Formulation for 

Diclofop-methyl and Diclofop-methyl: Human Health Assessment Scoping Document in support 

of Registration Review.

During registration review, the Agency anticipates the need to conduct a comprehensive

ecological risk assessment, including an endangered species assessment, for all uses of diclofopmethyl. For human health, EPA anticipates the need to conduct a revised dietary (drinking water 

only), residential, and occupational risk assessments during registration review. If toxicological 

endpoints or points of departure are revised based on the data that are anticipated to be 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.

Table 4 below summarizes the anticipated registration review risk assessments based on the 

EFED Problem Formulation and HED Scoping Document.
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Table 4: Anticipated Risk Assessments for the Diclofop-methyl Registration Review

Type of Risk Assessment Conduct? Notes

Ecological and Environmental Fate

Comprehensive ecological 

(species to be assessed 

include terrestrial and 

aquatic organisms), 

including endangered 

species 

Y EPA anticipates updating the ecological risk 

assessment including a complete endangered species 

determination. 

Incidents Will check for 

updates

For a discussion of reported ecological incidents for 

diclofop-methyl, see page 15 of the Problem 

Formulation.

Human Health

Dietary

Food N If the drinking water concentrations increase 

significantly, a revised dietary risk assessment may be 

needed.

Drinking water Y EPA anticipates updating the drinking water 

assessment.

Occupational

Handlers (mixers, loaders, 

applicators)

N An updated occupational handler assessment may be 

needed based on significant changes to exposure 

assessment methodology and any new data that are

submitted.

Post-application N An updated occupational post-application assessment 

may be needed based on significant changes to 

exposure assessment methodology and any new data 

that are submitted.

Residential

Handlers N EPA does not anticipate conducting a residential 

handler assessment as there are no residential uses.

Post-application Y EPA anticipates updating residential post-application 

assessment to incorporate the anticipated data using 

the 2012 residential standard operating procedures.

Other

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. EPA anticipates that updating 

the aggregate risk assessment will be required to 

incorporate updated drinking water estimates and 

revised residential post-application exposure 

estimates.

Cumulative N Diclofop-methyl has not been identified as a member 

of a cumulative group that shares a common 

mechanism of toxicity.
9

Table 4: Anticipated Risk Assessments for the Diclofop-methyl Registration Review (cont.)

Type of Risk Assessment Conduct? Notes

Tolerances Y EPA anticipates updating diclofop-methyl tolerances, 

established in 40 CFR §180.385, to align with new crop 

groups and, where possible, to harmonize with 

international MRLs. 

Incidents Will check for 

updates

For a discussion of reported human incidents for 

diclofop-methyl, see page 10 of the Scoping 

Document and the Diclofop-methyl: Tier 1 Review of 

Human Incidents.

Guidance for Commenters: Additional ecological information requested for this 

registration review, and of particular interest to EPA, is described below.

 Ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency.

 Water quality monitoring data (see Appendix for further details).

TIMELINE

EPA has created the following estimated timeline for the completion of the diclofop-methyl

registration review in Table 5 below.

Table 5: Projected Diclofop-methyl Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period September 2014

Close Public Comment November 2014

Case Development

Final Work Plan February 2015

Issue DCI April – June 2015

Data Submission April – June 2017

60-day Public Comment Period for Draft Risk 

Assessments3

October – December 2018

Registration Review Decision

60-day Public Comment Period for Proposed 

Registration Review Decision

July – September 2019

Registration Review Decision and Begin Post-Decision 

Follow-up

2020

Total (years) 6

 

3 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period generally for draft risk assessments.
10

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 diclofop-methyl.
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Appendix – Additional Areas Considered in the Diclofop-methyl Registration 

Review

PUBLIC COMMENTS AND FEEDBACK:

Guidance for Commenters: The areas below highlight topics of special interest to the Agency 

where your comments, data submissions, or reference to sources of additional information could 

be of particular use.

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. The Agency 

will work to harmonize tolerances and international maximum residue limits (MRLs) and may 

modify tolerance levels to do so, when possible. Growers and other stakeholders are asked to 

comment on any trade irritant issues resulting from lack of 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. 

Water Quality:

Diclofop-methyl is not identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act.

4

 In addition, no Total Maximum Daily 

Loads (TMDL) have been developed for diclofop-methyl.

5

 More information on impaired water 

bodies and TMDLs can be found at the Agency’s website.

6 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 Process7in order to ensure they can be used quantitatively or qualitatively in 

pesticide risk assessments.

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 diclofop-methyl 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.

 

4 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

5http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_

group_name=PESTICIDES

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

7 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
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ENDANGERED SPECIES:

A risk assessment that supports a complete endangered species determination has not been 

conducted for diclofop-methyl. The ecological risk assessment planned during registration 

review will allow the Agency to determine whether use of diclofop-methyl has “no effect” or 

“may affect” federally listed threatened or endangered species (listed species) or their designated 

critical habitats. When an assessment concludes that a pesticide’s use “may affect” a listed 

species or its designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife 

Service and/or National Marine Fisheries Service (the Services), as appropriate.

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 for diclofop-methyl, 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), diclofop-methyl

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. A second list 

of chemicals identified for EDSP screening was published on June 14, 20138and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

 

8 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals.
13

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

chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website.9

HUMAN STUDIES:

Occupational and Residential

Past diclofop-methyl risk assessments rely 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 the Pesticide Handlers Exposure Database (PHED), 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.

 

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