2

Metolachlor and S-Metolachlor Preliminary Work Plan – Table of Contents 

OVERVIEW ................................................................................................................................... 4

ANTICIPATED DATA NEEDS .................................................................................................... 5

STATUTORY AND REGULATORY AUTHORITY ................................................................... 7

CHEMICAL FACTS ...................................................................................................................... 7

USE AND USAGE INFORMATION ............................................................................................ 8

RECENT ACTIONS ..................................................................................................................... 10

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW .............................. 10

TIMELINE .................................................................................................................................... 13

NEXT STEPS ............................................................................................................................... 13

Appendix – Additional Areas Considered in the Metolachlor and S-Metolachlor Registration 

Review ...................................................................................................................................... 14 

References:

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

based on the following documents: 

1. Registration Review Problem Formulation for Metolachlor and S-Metolachlor. Sternberg, 

Koper. December 3, 2014. 

2. Metolachlor and S-Metolachlor. Human Health Scoping Document in Support of 

Registration Review. Kidwell, Hummel, Nieves. November 19, 2014. 

3. Metolachlor: Tier I Review of Human Incidents. Evans, Recore, Christensen. September 

16, 2014. 

4. BEAD Chemical Profile (BCP) for Registration Review: Metolachlor Case [S-metolachlor 

(108800) and Metolachlor (108801)]. Yourman, Alsadek, Hill. November 6, 2014.

5. Metolachlor (108801) Screening Level Usage Analysis (SLUA). April 21, 2014.
3

6. S-Metolachlor (108801) Screening Level Usage Analysis (SLUA). April 24, 2014.

7. EFED Table 1 Report, Metolachlor (108801). August 12, 2014

8. EFED Table 1 Report, S-Metolachlor (108800). September 16, 2014

9. HED Master Label Spreadsheet, Metolachlor (108801). August 12, 2014.

10. HED Master Label Spreadsheet, S-Metolachlor (108800). September 16, 2014.

These and other supporting documents for the metolachlor and S-metolachlor registration review 

case may be found in the docket EPA-HQ-OPP-2014-0772 at http://www.regulations.gov.
4

OVERVIEW 

The docket for metolachlor and S-metolachlor is now open, initiating the first public comment 

period for this registration review (docket number 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. This 

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

knows about metolachlor and S-metolachlor, 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 

metolachlor and S-metolachlor. 

 

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 metolachlor and S-metolachlor and what 

types of new data or other information would be helpful for the Agency to receive as it moves 

toward a decision on metolachlor and S-metolachlor. 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 metolachlor and Smetolachlor. 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 metolachlor and Smetolachlor. 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. 

 
5

ANTICIPATED DATA NEEDS 

Table 1 below summarizes anticipated data needs for metolachlor and S-metolachlor. For 

additional discussion of the anticipated data needs, see the Registration Review Problem 

Formulation for Metolachlor and S-Metolachlor and Human Health Scoping Document in 

Support of Registration Review. 

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

Registration Review 

Guideline 

Number1 Study Title1 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

Anticipated 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 

850.7100 ECM/ILV: method and independent validation in 

soil and independent validation in water TGAI 12 

NonGuideline Whole sediment: chronic invertebrates, 

freshwater and marine TGAI 12 

NonGuideline Honey bee adult chronic oral toxicity TGAI 12 

NonGuideline 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 

Anticipated Data Needs for the S-Metolachlor

850.4100 Seedling emergence and seedling growth (four 

species of dicots) TEP 12 

850.4150 Vegetative vigor (four species of dicots) TEP 12 

875.2100 Turf Transferable Residue TGAI 12 

 

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 
6

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

Registration Review 

Guideline 

Number1 Study Title1 

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

Anticipated Data Needs for Metolachlor 

870.3465 28-day inhalation toxicity study TGAI 24 

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

850.4100 Seedling emergence and seedling growth 

(ryegrass, tomato, and carrot) TGAI 12 

Anticipated 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; 

 
7

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 metolachlor and S-metolachlor. 

CHEMICAL FACTS 

Table 2 provides a summary of the chemical facts for metolachlor and S-metolachlor. 

Table 2: Chemical Facts for Metolachlor and S-Metolachlor

PC code 108801 (metolachlor) and 108800 (S-metolachlor) 

Case Number 0001 

CAS Number 51218-45-2 (metolachlor) and 87392-12-9 (S-metolachlor) 

Year first registered 1976 (metolachlor) and 2004 (S-metolachlor) 

Pesticide Type Broad spectrum herbicide 

Chemical class Chloroacetanilide 

Reregistration Eligibility 

Decision (RED) 

A RED was completed for metolachlor in April 1995. Because Smetolachlor was registered after November 1984 it was not 

subject to reregistration. 

Tolerance Reassessment 

Eligibility Decision 

(TRED) 

A TRED was completed for metolachlor in June 2002. No TRED 

was done for S-metolachlor. 

 

2

 http://www.epa.gov/oppsrrd1/registration_review/ 
8

Table 2: Chemical Facts for Metolachlor and S-Metolachlor

Cumulative group Not applicable. Metolachlor and S-metolachlor have not been 

identified as members of a cumulative group that shares a 

common mechanism of toxicity. 

40 CFR Citation Tolerances for metolachlor and S-metolachlor are established in 

§180.368. 

Dual-use Metolachlor and S-metolachlor are registered for conventional 

pesticidal uses only and have no registered antimicrobial or 

biopesticidal uses. 

Non-pesticidal uses There are no identified non-pesticidal uses of metolachlor and Smetolachlor. 

Pesticide Re-evaluation 

Division, Chemical 

Review Manager 

Steven Snyderman, snyderman.steven@epa.gov, 703-347-0249 

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 metolachlor and S-metolachlor. Please 

see the BEAD Chemical Profile (BCP) for Registration Review: Metolachlor Case [Smetolachlor (108800) and Metolachlor (108801)] in the registration review docket for more 

details. 

Table 3: Metolachlor and S-Metolachlor Use and Usage Information

Summary of Use Metolachlor and S-metolachlor are chloroacetamide herbicides, 

used to control grasses and some broadleaf weeds prior to weed 

emergence. They may be used preplant or post-plant on some 

crops to inhibit pre-emerged grasses. 

For many crops, seeds can be planted immediately after herbicide 

treatment. Additionally, for cotton production, they can be used 

later in the season as layby herbicides, which can provide 

effective control of pre-emerged weeds, especially in combination 

with a post-emergence herbicide. 

Use Sites Agricultural Use Sites 

S-metolachlor: blueberries, citrus fruits, tree nuts, stone fruits, 

root and tuber vegetables, bulb vegetables, fruiting vegetables, 

legume vegetables, stem vegetables, seeds and sugar beets. 

Metolachlor: blueberries, citrus, stone fruits, figs, cilantro, ginger, 

melons, leafy vegetables, cole crops, bulb crops, root crops, pod 

crops, seed crops, grain crops, cotton, Christmas trees, and fruit 

trees. 
9

Table 3: Metolachlor and S-Metolachlor Use and Usage Information

Non-agricultural Use Sites 

S-metolachlor: grasses, ornamentals, airports, recreation areas, 

athletic fields and roadsides. 

Metolachlor: airports, grasses, nurseries, ornamentals, turf, 

recreation areas and roadsides. 

Summary of Usage Based on private market usage data from 1998-2012, Smetolachlor usage averaged approximately 28 million pounds 

active ingredient (a.i.) applied annually on approximately 24 

million acres treated. The average typical rate applied over this 

time period was 1.2 pounds a.i./acre. S-metolachlor was applied 

mostly on corn. 

During that same time frame metolachlor usage averaged 

approximately 9 million pounds a.i. applied annually on 

approximately 6 million acres. The average typical rate applied 

over this time period was 1.50 pounds a.i./acre. Metolachlor was 

found to be applied mostly on corn. 

Formulation Type(s) Granular, emulsifiable/flowable/soluble concentrate, solutionready to use and as pressurized liquid. 

Application Method(s) Metolachlor products are applied aerially (fixed wing and rotary 

aircraft) and low volume application through water spray while Smetolachlor products are applied both on the ground and aerially. 

Technical Registrant(s) Metolachlor: Makhteshim-Agan of North America Inc., Drexel 

Chemical Company, and Sipcam Agro USA, Inc. 

S-metolachlor: Syngenta Crop Protection, LLC 

No. of Registrations Metolachlor: 35 Section 3 products3 (of which 3 technical 

registrations) and 2 Special Local Needs (SLNs) 

S-metolachlor: 46 Section 3 products (of which 3 technical 

registrations) and 105 SLNs 

Restricted Use No 

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. 

 Usage information would be helpful on crops where metolachlor and S-metolachlor is 

registered but not surveyed, such as lentils (S-metolachlor), triticale (S-metolachlor), and 

figs (metolachlor) and non-agricultural use sites such as grasses. This may improve future 

assessments conducted by the Agency related to the use and importance of metolachlor 

and S-metolachlor. 

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

application methods and equipment; maximum application rates; frequency of 

 

3

 Section 3 product labels can be obtained from the Pesticide Product Label System (PPLS) website 

(http://oaspub.epa.gov/pestlabl/ppls.home). 
10

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 metolachlor and Smetolachlor to the US market. 

RECENT ACTIONS 

A new use on corn, field, forage and stover (increased tolerance); corn, pop, stover; and corn, 

sweet, forage and stover (increased tolerance) was added for S-metolachlor in April 2014 (79 FR 

17436). 

ANTICIPATED RISK ASSESSMENTS FOR REGISTRATION REVIEW 

The most recent comprehensive human health risk assessment for metolachlor was completed in 

2003 in preparation for the Tolerance Reassessment Eligibility Decision (TRED) and for Smetolachlor was completed in 2013 to establish higher tolerances for corn forage and stover. 

The most recent ecological and environmental fate risk assessment for metolachlor and Smetolachlor was completed in 2012 for a new use registration of S-metolachlor on cilantro and 

garden beet leaves. Findings and conclusions from these risk assessments are summarized in the 

Registration Review Problem Formulation for Metolachlor and S-Metolachlor and Metolachlor 

and S-metolachlor: Human Health 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 

metolachlor and S-metolachlor. For human health, EPA anticipates the need to conduct revised 

dietary, occupational, residential, aggregate, 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. 
11

Table 4: Anticipated 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 anticipated 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 anticipated data 

requirements. An updated post-application exposure 

assessment may be needed during registration review 

dependent upon the information received in the 

anticipated 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 
12

Table 4: Anticipated Risk Assessments for the Metolachlor and S-Metolachlor 

Registration Review 

Type of Risk Assessment Conduct? Notes 

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. 

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). 

 Label clarification is needed on some labels that includes the absence of a maximum 

single application rate, minimum application intervals, maximum number of applications 

allowed per year (and crop cycle, if applicable), a maximum annual application rate (in 

lbs a.i./year), ornamental band treatment use application rate in lb ai/A, and application 

method on labels. The absence of this information on the labels may result in 

conservative assumptions and maximum exposure scenarios for the given uses in the risk 

assessment. 
13

TIMELINE 

EPA has created the following estimated timeline for the completion of the metolachlor and Smetolachlor registration review in Table 5 below. 

Table 5: Projected Metolachlor and S-Metolachlor Registration Review Timeline

Activities Estimated Date

Opening the Docket 

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

Close Public Comment 2015 – February 

Case Development 

Final Work Plan 2015 – May 

Issue DCI 2015 July – Sept. 

Data Submission 2017 July – Sept. 

60-day Public Comment Period for Draft Risk 

Assessments4

2019 Jan. - March 

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 

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 metolachlor and S-metolachlor. 

 

 

4

 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. 
14

Appendix – Additional Areas Considered in the Metolachlor and SMetolachlor 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: 

Metolachlor and S-metolachlor are not identified as a cause of impairment for any water bodies 

listed as impaired under section 303(d) of the Clean Water Act.5

 In addition, no Total Maximum 

Daily Loads (TMDL) have been developed for metolachlor and S-metolachlor.6 More 

information on impaired water bodies and TMDLs can be found at the Agency’s website.7 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 Process8 in 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 metolachlor and S-metolachlor 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.

 

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

6

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

group_name=PESTICIDES 7 http://www.epa.gov/owow/tmdl/

8 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
15

ENDANGERED SPECIES: 

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

conducted for metolachlor and S-metolachlor. The ecological risk assessment planned during 

registration review will allow the Agency to determine whether use of metolachlor and Smetolachlor 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. 

On June 5, 2013, the Center for Biological Diversity and the Pesticide Action Network North 

America filed an amended complaint in its lawsuit in the United States District Court for the 

Northern District of California, against the EPA for allegedly failing to undergo consultation 

with the United States Fish and Wildlife Service and the National Marine Fisheries Service 

regarding the effects of over 50 pesticides, including metolachlor and S-metolachlor, on over 100 

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.). 

A previous endangered species assessment was conducted for metolachlor and S-metolachlor in 

2006 through a litigation assessment for 26 evolutionarily significant units of listed salmonids in 

the Pacific Northwest, 2007 as part of litigation assessments for the Barton Springs salamander 

and California red legged frog, and a 2010 litigation assessment for the San Francisco Bay area 

species, delta smelt and California tiger salamander. 

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 most recent registration decision for metolachlor and Smetolachlor, 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), metolachlor and S-metolachlor are 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 
16

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, 20139

 and 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. 

Metolachlor is on List 1 for which EPA has received all the required Tier 1 assay data. The 

Agency is currently reviewing all of the assay data received for the appropriate List 1 chemicals 

and planning to make the conclusions of those reviews available in early 2015. The degradates 

metolachlor-ESA and metolachlor-OA are on List 2. List 2 represents the next set of chemicals 

for which EPA intends to issue test orders/data call-ins in the near future. S-metolachlor is not 

among the group of 58 pesticide active ingredients on the initial list to be screened under the 

EDSP nor List 2. Accordingly, as part of registration review, EPA will issue future EDSP 

orders/data call-ins, requiring the submission of EDSP screening assays for S-metolachlor. 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.10

HUMAN STUDIES: 

Occupational 

Past metolachlor and S-metolachlor 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) 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. 

 

9

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

chemicals. 10 http://www.epa.gov/endo/