Introduction:

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

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

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

Preliminary Work Plan in the Summary Document, which was posted in the initial 

registration review docket, or any other comments concerning 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 new registration review program, and plans to 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 

that 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/. 

Methiocarb is an N-methyl carbamate insecticide, acaricide, molluscicide and avian 

repellent registered for use to control snails, slugs, mites and insects on ornamentals, 

lawns, and non-bearing deciduous and nut trees. There are no food or feed uses for 

methiocarb. The wettable powder formulations of methiocarb are restricted use 

pesticides available only to professional applicators and are applied by broadcast, foliar 

spray, and soil incorporation to ornamental plants and non-bearing deciduous and nut 

trees. One formulation of methiocarb is a general use pesticide sold as solid bait 

products, which can be used by homeowners and which are sprinkled over ornamental 

plant and non-bearing tree foliage, or applied to soil around plants grown in greenhouses, 

nurseries, or residential gardens. Potential metabolites of concern are methiocarb 

sulfoxide (MSO), methiocarb phenol (MP), and methiocarb sulfoxide phenol (MSOP).

Methiocarb is a member of the N-methyl carbamate (NMC) class of chemicals that share 

a common mechanism of toxicity and inhibit acetylcholinesterase by carbamylation of 

the serine hydroxyl group located in the active site of the enzyme. The “Revised NMethyl Carbamate Cumulative Risk Assessment” was completed in September 2007 

(available in the docket EPA-HQ-OPP-2007-0935). 

Comments Received on Preliminary Work Plan:

The Agency received three comments on the methiocarb docket during the 60-day public 

comment period, which began on June 23, 2010 and ended on August 23, 2010. The 

comments received do not change the data and risk assessment needs or the timeline 

detailed in the Methiocarb PWP. An overview of comments is presented in the 

“Summary of Comments and Agency Responses” section of this document. This 

document finalizes the work plan for the methiocarb registration review process. 

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Anticipated Risk Assessment and Data Needs:

The Agency anticipates conducting comprehensive human health and ecological risk 

assessments, including an endangered species assessment, for all uses of methiocarb and 

its metabolites of concern. Below is a summary of the issues relevant to the registration 

review process for methiocarb. 

Ecological Risk: 

• The most recent comprehensive ecological risk assessment for registered uses of 

methiocarb was conducted in 1994 in support of the Methiocarb Reregistration 

Eligibility Decision (RED). Acute levels of concern (LOC) were exceeded for 

birds, reptiles, mammals, and invertebrates, and chronic risk LOC were exceeded 

for birds, fish, and aquatic-phase amphibians. 

• The degradation of methiocarb in soils is not well-defined, and more data are 

needed on aerobic soil metabolism. 

• Data are needed for aerobic and anaerobic aquatic metabolism because use on 

‘field grown ornamentals’ is not precluded by current methiocarb labels, and 

therefore must be assumed. 

• A fish accumulation data requirement (Guideline 850.1730) was previously 

waived because methiocarb and its degradates were assumed to kill fish before 

toxic residues could bioaccumulate. Based on new guideline requirements, this 

study is anticipated to be required as part of the registration review process. 

• Toxicity data for methioicarb degradates (methiocarb sulfoxide (MSO), 

methiocarb phenol (MP), methiocarb sulfoxide phenol (MSOP), methiocarb 

sulfone (MSO2), and methiocarb sulfone phenol (MSO2P) are lacking. The 

residues of concern for exposure and risk assessment will be reconsidered prior to 

analysis. In the absence of confirmatory data indicating low toxicity concerns for 

the major degradates of methiocarb, they will be assumed of equal toxicity as the 

parent. 

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

endangered species determination for methiocarb. The ecological risk assessment 

planned during registration review will allow the Agency to determine whether 

methiocarb’s use has “no effect” or “may affect” federally listed threatened or 

endangered species (listed species) or their designated critical habitat. 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.

• The Agency needs the following data in order to conduct a complete 

environmental fate and ecological risk assessment for parent methiocarb and its 

degradates, including a complete endangered species assessment. 

Environmental Effects Studies: 

o Guideline 850.1730 - Fish Bioconcentration Study

o Guideline 850.2300 - Avian Reproduction Test (Bobwhite Quail)

o Guideline 850.3030 - Honeybee Toxicity of Residues on Foliage

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o Guidelines 850.1075, 850.1025 and 850.1035, 850.1045, or 850.1055 - 

Estuarine/Marine Fish & Invertebrate Acute Toxicity Tests

o Guidelines 850.1300 & 850.1350 - Freshwater & Estuarine/Marine 

Invertebrate Life Cycle Toxicity Test

o Guideline 850.1400 - Freshwater & Estuarine/Marine Fish Early Life 

Stage Toxicity Test

o Guidelines 850.4100 & 850.4150 - Terrestrial Plant Toxicity Tests (Tier I)

o Guideline 850.4400 - Aquatic Vascular Plant Growth (Tier I)

o Guideline 850.5400 - Aquatic Non-vasular Plant Growth (Tier I)

Environmental Fate Studies: 

These studies are needed to provide information on how, or by what mechanism, 

the pesticide degrades, the rate at which it degrades, where it goes, and what 

transformation products are formed once the compound is applied in the 

environment. 

o Guideline 835.4100 - Aerobic soil metabolism study

o Guideline 835.4300 - Aerobic aquatic metabolism study

o Guideline 835.4400 - Anaerobic aquatic metabolism study

o Guidelines 835.1230 & 1240 - Leaching and adsorption/desorption

 (for methiocarb, methiocarb phenol, methiocarb sulfoxide, methiocarb 

 sulfoxide phenol).

o Guideline 835.6100 (Footnote 7) - Environmental chemistry analytical 

method in soil and independent laboratory validation

o Guideline 835.6200 (Footnote 7) - Environmental chemistry analytical 

method in water and independent laboratory validation

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

Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water 

Exposure Assessments for Methiocarb in the methiocarb registration review 

docket (EPA-HQ-OPP-2010-0278).

 Human Health Risk: 

• The most recent dietary and drinking water risk assessments for methiocarb were 

conducted for the February 1994 RED for methiocarb. 

• The toxicology database for methiocarb is not considered complete for the 

purposes of registration review because of data gaps for a comparative ChE study 

in adults and offspring and an immunotoxicity study. 

• A 2-generation reproduction study has been submitted and will be reviewed 

during registration review. 

• Both acute and subchronic neurotoxicity studies were previously identified as data 

gaps in the RED. However, information about N-methyl carbamate neurotoxicity 

is now known from the EPA National Health and Environmental Effects Research 

Laboratory (NHEERL) studies and from the carbamate cumulative assessment. 

Consequently, the Agency will require an acute comparative cholinesterase study 

for methiocarb, but does not anticipate requiring acute and subchronic 

neurotoxicity studies, or a developmental neurotoxicity study.

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• A drinking water exposure assessment for groundwater and surface water has not 

been conducted and will be included during registration review. 

• Since there are no food or feed uses for methiocarb, dietary exposure from food is 

not expected. However, a decision on residues of concern in drinking water has 

not yet been made, and an updated drinking water assessment, as well as 

aggregate risk assessment (due to potential residential exposure), may be 

conducted to support the registration review of methiocarb.

• Both residential handler and residential postapplication exposure are possible and 

neither has been quantitatively assessed. Residential handler exposure could 

occur from application of bait formulation to lawns and (non-food) gardens. 

Residential postapplication exposure could occur from: 1) contact with 

commercially grown nursery plants previously treated with methiocarb; 2) dermal 

and incidental oral exposure to children from contact with treated garden plants; 

and 3) dermal and incidental oral exposure to children through contact with or 

ingestion of pellets or granules of the bait treatment. Both residential handler and 

postapplication exposures will be assessed during registration review. 

• The Agency anticipates conducting a revised occupational handler exposure 

assessment and a postapplication assessment for methiocarb for all handler 

exposures, except the egg treatment use pattern, to reflect updates in Agency 

occupational/residential exposure assessment methodologies.

• The Agency will require the following studies in order to conduct a complete 

human health assessment: 

o Special Study - Comparative Cholinesterase Assay 

o Guideline 870.7800 - Immunotoxicity 

• Prior to a final registration review decision for methiocarb, the Agency will 

determine if there is any new information, such as new hazard or exposure data or 

information on changes to the use pattern, which could affect the 2007 Revised 

NMC Cumulative Risk Assessment. If so, the Agency will revisit the cumulative 

risk assessment. 

• Please refer to the Methiocarb. Human Health Assessment Scoping Document in 

Support of Registration Review in the methiocarb registration review docket 

(EPA-OPPTS-OPP-2010-0278) for a detailed discussion of previous human 

health assessments. 

Other Anticipated Data Needs: 

• Guideline 830.7050 UV/Visible Light Absorption – this study is a new data 

requirement under 40 CFR part 158 (Product Chemistry Data Requirements) for 

registration of a pesticide (food and non-food uses). The Agency will be 

requiring this study to obtain basic information about the compound’s 

identity/composition and the wavelengths at which the compound may be 

susceptible to photochemical degradation.

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Endocrine Disruptor Screening Program (EDSP): 

As required under FFDCA section 408(p), EPA has developed the Endocrine Disruptor 

Screening Program (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 quantitative 

relationship between the dose and the E, A, or T effect. 

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. This list of chemicals was selected based on the potential for human 

exposure through pathways such as food and water, residential activity, and certain postapplication agricultural scenarios. This list should not be construed as a list of known or 

likely endocrine disruptors. 

Methiocarb was one of several pesticides removed from the initial list of pesticides to be 

screened because changes in their use and application methods eliminated the potential 

for exposure in one or more pathways. Specifically, the remaining agricultural uses for 

methiocarb are granular applications in nurseries and greenhouses, and current 

registrations no longer include use on food crops. Although methiocarb is only present in 

two exposure pathways (water and residential), under FFDCA sec. 408(p) the Agency 

must screen all pesticide chemicals. Accordingly, EPA anticipates issuing future EDSP 

orders/data call-ins for all Registration Review cases, including those for which EPA has 

already opened a Registration Review docket for a pesticide active ingredient. 

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

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

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

Timeline: 

EPA has created the following estimated timeline for the completion of the methiocarb 

registration review. 

Registration Review for Methiocarb – Projected Registration Review Timeline

Activities Estimated Date 

Opening the docket 

Open Docket and Public Comment Period 2010 – June 

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Close Public Comment 2010 – August 

Case Development 

Final Work Plan 2010 – December 

Issue DCI 2011 – Jul.-Sept. 

Data Submission 2013 – Jul.-Sept. 

Open Public Comment Period for Preliminary Risk Assessments 2015 – Jan.-Mar. 

Close Public Comment Period 2015 – Apr.-Jun. 

Registration Review Decision 

Open Public Comment Period for Proposed Registration Review 

Decision 

 2015 – Jul.-Sept. 

Close Public Comment Period 2015 – Oct.-Dec. 

Final Registration Review Decision and Begin Post-Decision 

Follow-up 

 2016 

Total (years) 6 

Summary of Comments Received During Docket Opening:

The Agency received comments from the Physicians Committee for Responsible 

Medicine (PCRM), the American Bird Conservancy (ABC), and the FIFRA Endangered 

Species Task Force (FESTF) relating to the environmental fate and ecological risk 

problem formulation for the Registration Review of methiocarb. 

PCRM Comments 

PCRM commented that the Agency could reduce the number of animals tested by 

following a “limit test” approach, and could use a Quantitative Structure Activity 

Relationship (Q)SAR data in addition to laboratory data. 

EPA Response 

The Agency agrees that a limit test approach could be used to fulfill the requirement if 

conducted according to guideline 850.1075 and classified as acceptable. The Agency is 

actively working with other agencies to develop a (Q)SAR guidance document and will 

consider its final recommendations when conducting ecological risk assessments. 

ABC Comments 

ABC commented that that the Agency should require several additional avian studies, 

including studies with passerine species and with degradates of the parent methiocarb 

compound. ABC also commented that backyard uses and the egg use of methiocarb 

should be suspended to protect birds.

EPA Response 

The Agency believes that the data it is requiring with avian species will be adequate for 

assessing potential risks of methiocarb to this taxa. The Agency concurs with ABC that 

an avian reproduction study is needed for quail, and this requirement was included in 

both the Preliminary and Final Work Plans. In addition, the Agency will review relevant 

databases and open literature for any additional data or information that addresses 

concerns raised by the ABC, (such as avian developmental effects or the toxicity of any 

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of the methiocarb degradates). In the absence of confirmatory data, the Agency will 

consider methiocarb degradates to be of equal toxicity to parent methiocarb. 

The registration review schedule is designed to allow EPA to obtain and review pertinent 

new information in order to make a thorough and informed decision regarding the 

benefits of the use of compounds weighed against the risks to all non-target species. The 

schedule also allows the Agency to conduct an assessment for any endangered species 

which might be at risk from the use of this compound. 

Regarding ABC’s comment to suspend certain uses of methiocarb, FIFRA gives EPA the 

authority to suspend use of pesticide under very specific circumstances which are: (1) 

imminent hazard [section 6(c)] or (2) failure to submit additional data [3(c)(2)(B)]. EPA 

did not review ABC’s incident database during the development of the RED, but the 

Agency did review other bird incident databases during that period. Although ABC 

requested suspension for the use of methiocarb, ABC did not provide, nor does EPA 

have, any new information that supports an imminent hazard finding, or a basis for 

suspending methiocarb registrations under the authority of section 3(c)(2)(B). 

Comments from the FIFRA Endangered Special Task Force (FESTF) 

FESTF suggested the Agency use FESTF data for its endangered species assessment of 

methiocarb, and made an additional comment regarding cost sharing for development of 

data on endangered species. 

EPA Response: The Agency thanks FESTF for its comments, and will consider this 

information as it conducts the registration review and makes its decision. 

Finally, in the Preliminary Work Plan, EPA solicited comments 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. 

Next Steps: 

A Data Call-In will be developed regarding data gaps listed under the “Risk Assessment 

and Data Needs” section. An ecological risk assessment, which includes an endangered 

species assessment, will be conducted. A drinking water assessment, as well as an 

aggregate risk assessment may be conducted, and the Agency anticipates assessing both 

residential handler and postapplication exposure during registration review. 

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