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INTRODUCTION

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

the registration review of metolachlor and S-metolachlor. This work plan addresses public 

comments received concerning the Preliminary Work Plan (PWP), which was posted in the

metolachlor and S-metolachlor registration review docket (EPA-HQ-OPP-2014-0772).

Metolachlor (PC Code 108801) is a racemic broad spectrum herbicide that consists of 50% each 

of the Renantiomer and the S-enantiomer, which is the herbicidally active isomer. S-Metolachlor 

(PC Code 108800) is an isomer enriched form of metolachlor, comprised of 88% S-isomer and 

12% R-isomer. Metolachlor and S-metolachlor are selective, chloroacetanilide herbicides used 

primarily for grassy weed control in many agricultural food and feed crops; residential lawns; 

commercial turf (including golf courses, sports fields, recreation areas, and sod farms); 

ornamental plants, trees, shrubs, and vines; hedge rows; and horticultural nurseries.

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency’s website.

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The FWP begins with any updates since the PWP was issued. Next is a summary of substantive 

comments received during the public comment period for the PWP concerning anticipated data 

needs, expected risk assessments, or the estimated timeline identified in the PWP, and a 

summary of the Agency’s responses to those comments. This section is followed by registration 

review planned data needs, risk assessments expected to be conducted, and the projected

registration review timeline for metolachlor and S-metolachlor. Lastly, there is a discussion of 

next steps.

UPDATES SINCE THE PWP WAS ISSUED

The Agency has reviewed the rationale submitted by Syngenta as part of the public comment 

period regarding the need for chronic sediment toxicity testing for the metolachlor/S-metolachlor 

registration review. Upon further review of the previously submitted Grade (1998) study, EPA 

does not plan on requiring the non-guideline chronic sediment toxicity study as part of 

registration review.

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the metolachlor and S-metolachlor Preliminary 

Work Plan, which opened on December 19, 2014 and closed on February 20, 2015, the Agency 

received four public comments. Comments were submitted by the FIFRA Endangered Species 

Task Force, the Center for Biological Diversity, the Metolachlor Task Force, and Syngenta Crop 

 1 http://www.epa.gov/oppsrrd1/registration_review/
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Protection, LLC. The comments do not address the timeline described in the PWP, but they do 

address the planned ecological and human health risk assessments and data requirements. 

In the PWP, EPA also solicited comments on the specific topics of environmental justice, water 

quality concerns, and trade irritants, and one comment was received by Syngenta regarding water 

quality. The comment discussed submitted data from the USGS National Water-Quality 

Assessment Program on S-metolachlor in surface and ground water, along with other state and 

federal water monitoring programs. Syngenta encouraged EPA to continue to rely on these data 

in future drinking water assessments. The Agency will continue to use a combination of 

modeling and monitoring data as appropriate. Although the U.S. Geological Survey’s National 

Water Quality Assessment (NAWQA) program has conducted some monitoring for 

metolachlor/S-metolachlor and its degradates, the NAWQA monitoring data are not targeted 

specifically to metolachlor/S-metolachlor use areas or during times of known metolachlor/Smetolachlor use; thus, the dataset does not likely reflect peak concentrations that may occur in 

surface waters when runoff events occur shortly after metolachlor/S-metolachlor is applied.

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

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

comments and EPA responses in their entirety are located in the docket, EPA-HQ-OPP-2014-

0772. Summarized public comments and Agency responses related to the anticipated ecological

risk assessment or data needs are in the Response to Public Comments on the EFED Registration 

Review Problem Formulation for Metolachlor and S-Metolachlor while those relevant to the 

anticipated human health risk assessment or data needs are in the Metolachlor and SMetolachlor. Response to Comments on the HED Human Health Scoping Document and 

pertaining the BEAD Chemical Profile and usage information in the BEAD Response to Public 

Comments in Support of Registration Review (EPA Docket ID No.: EPA-HQ-OPP-2014-0772) –

Metolachlor Case [S-metolachlor (108800) and Metolachlor (108801)]. 

Comments submitted by the Center for Biological Diversity (CBD), in EPA-HQ-OPP-2014-

0772-0014.

1. Comment: The Center for Biological Diversity’s (CBD) comments focus on the EPA’s duty to 

consult with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service 

(the Services) on the registration review of metolachlor and S-metolachlor in accordance 

with the Endangered Species Act (ESA). CBD mentions various aspects of the risk 

assessment process, including use of the best available data to develop endangered species 

risk assessments, and evaluation of effects on endangered and threatened species and their 

designated critical habitat. CBD also expressed concern regarding the rigor of the Agency’s 

preliminary determinations regarding the effects of metolachlor and S-metolachlor on 

endangered and threatened (listed) species and their designated critical habitat for the 

metolachlor and S-metolachlor registration review. 

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

opening for metolachlor and S-metolachlor and plans to address many of the concerns raised 

by CBD as part of the implementation plan for assessing the risks of pesticides to listed 

species based on the recommendations of the April 2013 National Academy of Sciences 
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(NAS) report. EPA will address concerns specific to metolachlor and S-metolachlor in 

connection with the development of its final registration review decision for this pesticide.

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

joint interim approaches for assessing risks to endangered and threatened (listed) species from 

pesticides. The interim approaches were developed jointly by the agencies in response to the 

NAS recommendations and reflect a common approach to risk assessment shared by the 

agencies as a way of addressing scientific differences between the EPA and the Services. The 

NAS report2 outlines recommendations on specific scientific and technical issues related to 

the development of pesticide risk assessments that EPA and the Services must conduct in 

connection with their obligations under the ESA and FIFRA. 

The joint interim approaches were released prior to a stakeholder workshop held on 

November 15, 2013. In addition, the EPA presented the joint interim approaches at the 

December 2013 Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues 

Research and Evaluation Group (SFIREG) meetings. The agencies also held stakeholder 

workshops in April and October 2014, allowing additional opportunities for stakeholders to 

comment on the interim approaches. Additional workshops are planned to enhance 

stakeholder involvement. As part of a phased, iterative process for developing the interim 

approaches, the agencies will also consider public comments on the interim approaches in 

connection with the development of upcoming registration review decisions. The details of 

the joint interim approaches are contained in the white paper, Interim Approaches for 

National-Level Pesticide Endangered Species Act Assessments Based on the 

Recommendations of the National Academy of Sciences April 2013 Report3

, dated November 

1, 2013. 

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

interim approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, the ecological problem formulation supporting this FWP for 

metolachlor and S-metolachlor does not describe the specific ESA analysis, including effects 

determinations for specific listed species or designated critical habitat, to be conducted during 

registration review. In the ecological problem formulation document for metolachlor and Smetolachlor, EPA described the screening-level risk assessment to determine the potential 

effects of metolachlor and S-metolachlor on all taxa of non-target wildlife and plants, which 

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

vicinity of the application of metolachlor and S-metolachlor. This screening-level assessment 

will allow EPA to focus its future evaluations on the types of species where the potential for 

effects exists once the scientific methods being developed by the agencies have been fully 

vetted. While the agencies continue to develop a common method for ESA analysis, the 

planned screening-level risk assessment for the registration review of metolachlor and Smetolachlor will describe the level of ESA analysis completed for this particular registration 

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

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

 2 http://www.nap.edu/catalog.php?record_id=18344

3 http://www.epa.gov/espp/2013/nas.html
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their designated critical habitats, these methods will be applied to subsequent analyses for 

metolachlor and S-metolachlor as part of completing this registration review.

Comments submitted by FIFRA Endangered Species Task Force (FESTF), in EPA-HQOPP-2014-0772-0015.

1. Comment: The technical registrant for metolachlor and S-metolachlor, as identified on the 

fact sheet included in the PWP, is Syngenta Crop Protection, LLC, which is a FESTF 

member and is entitled to rely on FESTF data.

Response: EPA appreciates FESTF’s comments and will consider this information during the 

registration review of metolachlor and S-metolachlor.

Comments submitted by Metolachlor Task Force in EPA-HQ-OPP-2014-0772-0016.

1. Comment: The Metolachlor Task Force provided input and comments stating that EPA has 

not been consistent when evaluating metolachlor and S-metolachlor’s relative equivalency 

when evaluating risk. The Metolachlor Task Force believes that the efficacy of both 

metolachlor’s is equal.

Response: The Agency appreciates the Metolachlor Task Force’s comments and will 

consider this information during the registration review of metolachlor and S-metolachor.

BEAD will review the information provided and consider it for future analyses of

metolachlor and S-metolachlor efficacy.

Comments submitted by Syngenta Crop Protection, LLC in EPA-HQ-OPP-2014-0772-

0017.

1. Comment: Syngenta provided several comments on the registration review Problem 

Formulation (PF) published in the docket. These comments included a discussion on end 

points from submitted studies that were referenced in the PF. Additionally, comments were 

made regarding a submitted chronic sediment toxicity study and whether that would fulfill 

the requirement for the non-guideline chronic sediment toxicity study. Lastly, Syngenta 

commented on EFED’s planned endangered species assessment for registration review.

Response: The Agency thanks Syngenta for their input and concurs with the majority of 

Syngenta’s discussed end points. Upon further review of the previously submitted Grade 

(1998) study, EPA does not plan on requiring the non-guideline chronic sediment toxicity 

study as part of registration review. Concerning the Endangered Species assessment the 

Agency is still in the process of finalizing our approach to assess the potential risks of 

pesticides to listed species and their designated critical habitat. Once this approach is 

finalized these methods will be applied to subsequent analyses of metolachlor/S-metolachlor 

as part of completing Registration Review. For a more detailed look into the Agency’s 

response on these comments please refer to Response to Public Comments on the EFED 

Registration Review Problem Formulation for Metolachlor and S-Metolachlor now in the 

metolachlor and S-metolachlor docket.
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2. Comment: Syngenta provided comments regarding the registration review Scoping 

Document. This included rational to support the fulfillment of residue data to support labeled 

directions for use for registered bulb vegetable, cotton, soybean, and tomato.

Response: The Agency and HED acknowledges receipt of this information and thanks 

Syngenta for their comment. For a more detailed look into the Agency’s response on these 

comments please refer to Metolachlor and S-Metolachlor. Response to Comments on the 

HED Human Health Scoping Document now in the metolachlor and S-metolachlor docket.

3. Comment: Syngenta provided comments regarding the BEAD Chemical Profile (BCP). This 

included a detailed use characterization for both metolachlor and S-metolachlor based on 

information in the BCP. Syngenta also provided a clearer picture of the history of the 

metolachlor registrations and it’s cancellation by Syngenta in 2001 and 2002 leading to an 

increase in S-metolachlor usage.

Response: EPA and the Biological and Economic Analysis Division appreciates the 

information provided by Syngenta and will take it into consideration as appropriate during 

the registration review process. The Agency particularly appreciates the usage clarifications 

which will help refine our view of current uses. For a more detailed look into the Agency’s 

response on these comments please refer to BEAD Response to Public Comments in Support 

of Registration Review (EPA Docket ID No.: EPA-HQ-OPP-2014-0772) – Metolachlor Case 

[S-metolachlor (108800) and Metolachlor (108801)] now in the metolachlor and Smetolachlor docket.
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PLANNED DATA NEEDS

Table 1 below summarizes the planned data needs for metolachlor and S-metolachlor based on 

the Registration Review Problem Formulation for Metolachlor and S-Metolachlor, the Human 

Health Scoping Document in Support of Registration Review, the Response to Public Comments

on the EFED Registration Review Problem Formulation for Metolachlor and S-Metolachlor, and 

Response to Public Comments on the EFED Registration Review Problem Formulation for 

Metolachlor and S-Metolachlor. The table has been updated since the PWP to reflect public 

comments which resulted in changes to the data needs.

Table 1: Planned Data Needs for the Metolachlor and S-Metolachlor

Registration Review

Guideline 

Number4 Study Title1

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

Planned Data Needs for the Parent (either metolachlor or S-metolachlor)

835.4100 Aerobic soil metabolism (2 additional soils) TGAI 24

835.4200 Anaerobic soil metabolism (3 additional soils) TGAI 24

835.4300 Aerobic aquatic metabolism (1 additional 

sediment system) TGAI 24

835.4400 Anaerobic aquatic metabolism (1 additional 

sediment system) TGAI 24

850.2100 Avian acute oral toxicity test, passerine species TGAI 12

850.6100 ECM/ILV: method and independent validation in 

soil and independent validation in water TGAI 12

NonGuideline Honey bee adult chronic oral toxicity TGAI 12

NonGuideline

(OECD 

237)

Honey bee larval acute oral toxicity TGAI 12

NonGuideline Honey bee larval chronic oral toxicity TGAI 12

NonGuideline Residues in pollen and nectar TEP 24

NonGuideline Semi-field testing for pollinators TEP 24

850.3040 Field testing for pollinators TGAI/TEP 24

 4 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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Table 1: Planned Data Needs for the Metolachlor and S-Metolachlor

Registration Review

Guideline 

Number4 Study Title1

Test Material

Estimated 

Timeframe

(Months from 

receipt of DCI)

Planned Data Needs for S-metolachlor

850.4100 Seedling emergence and seedling growth (four 

species of dicots, one of which is soybean) TEP 12

850.4150 Vegetative vigor (four species of dicots, one of 

which is soybean) TEP 12

875.2100 Turf Transferable Residue TGAI 12

Planned Data Needs for Metolachlor

870.3465 28-day inhalation toxicity study TGAI 24

Planned Data Needs for the Metolachlor Ethanesulfonic Acid (ESA) Degradate

850.4100 Seedling emergence and seedling growth 

(ryegrass, tomato, and carrot) TGAI 12

Planned Data Needs for the Metolachlor Oxanilic Acid (OA) Degradate

850.4100 Seedling emergence and seedling growth (onion) TGAI 12

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

RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of metolachlor and S-metolachlor. For 

human health, EPA will conduct revised dietary, residential, aggregate, and occupational risk 

assessments during registration review. If toxicological endpoints or points of departure are 

revised based on the data that are required for registration review, they will be considered in the 

new assessments, as well as any changes to the standard operating procedures or default 

exposure assumptions.

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document and the planned assessments have not 

changed from what was included in the PWP.
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Table 2: Planned Risk Assessments for the Metolachlor and S-Metolachlor 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 Although degradates Ethanesulfonic Acid (ESA) and 

Oxanilic Acid (OA) are less toxic than parent 

metolachlor/S-metolachlor, they are more persistent 

and are formed to a significant extent. Consequently, 

data are needed for the metolachlor degradates ESA 

and OA; these data have been listed in table 1.

Incidents Will check for 

updates

For a discussion of reported ecological incidents for 

metolachlor and S-metolachlor, see page 28 of the 

Problem Formulation.

Human Health

Dietary

Food Y The most current risk assessments do not indicate 

risk estimates of concern, however, if there are 

changes to the toxicological points of departure 

(PODs) or Uncertainty Factors (UFs) or significant 

changes to the Estimated Drinking Water 

Concentrations (EDWCs) an updated assessment will 

be needed.

Drinking water Y

Occupational

Handlers (mixers, loaders, 

applicators)

Y Though previous occupational handler and postapplication exposure assessments did not identify 

risks of concern, registration review may include 

updated estimates based on current policies and 

PODs/UFs may change based on the planned data 

requirements.

Post-application Y

Residential

Handlers Y S-metolachlor is not intended for homeowner 

purchase or use (only registered for use by 

professional/commercial applicators), therefore a 

residential handler assessment is not anticipated. 

However, registration review may include updated 

estimates based on current policies and PODs/UFs 

may change based on the planned data requirements. 

An updated post-application exposure assessment 

may be needed during registration review dependent 

upon the information received in the planned Turf 

Transferable Residue study. The need for a bystander 

assessment may also be needed and will be revisited 

at the time of the risk assessment. 

Post-application Y
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Other

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. Though no aggregate risks of 

concern were identified in the most recent 

assessment, an updated assessment may be needed to 

include any significant change that might occur for 

toxicological PODs, FQPA and uncertainty factors, 

dietary exposure estimates or EDWCs.

Cumulative N Metolachlor and S-metolachlor are not members of a 

cumulative group.

Tolerances Y No changes to tolerances are anticipated at this time, 

since the tolerance expression is in accord with 

current guidance and is compatible with the 

Canadian expression. However, U.S. tolerance levels 

are higher for certain crops and should be examined 

during registration review to determine if numerical 

harmonization is possible.

Incidents Will check for 

updates

Due to the low frequency of reported incidents there 

does not appear to be a concern at this time that 

would warrant further investigation. For a discussion 

of reported human incidents for metolachlor and Smetolachlor, see page 11 of the Scoping Document 

and the Metolachlor: Tier I Review of Human 

Incidents.

TIMELINE

EPA has created the following estimated timeline for the completion of the metolachlor and Smetolachlor registration review in Table 3 below. The projected timeline has not changed since 

the PWP.

Table 3: Registration Review for Metolachlor and S-Metolachlor – Projected 

Registration Review Timeline

Activities Estimated Date

Opening the Docket

Open Docket and 60-day Public Comment Period December 2014 – Completed

Close Public Comment February 2015 – Completed

Case Development

Final Work Plan June 2015 – Completed

Issue DCI 2015 July – Sept.

Data Submission 2017 July – Sept.

60-day Public Comment Period for Draft Risk Assessments5 2019 Jan. - March

 5 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.
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Table 3: Registration Review for Metolachlor and S-Metolachlor – Projected 

Registration Review Timeline

Activities Estimated Date

Registration Review Decision

60-day Public Comment Period for Proposed Registration 

Review Decision

2019 Oct. – Dec.

Registration Review Decision and Begin Post-Decision 

Follow-up

2020

Total (years) 6

NEXT STEPS

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

and human health studies for metolachlor and S-metolachlor through a Data Call-In Notice, 

expected to be issued in 2015.