Based on the current use profile, exposures can be expected to occur via the dietary, 

(food and drinking water) and occupational (handler and post-application) routes for 

methomyl. Also, there is a potential for residential handler and post-application 

exposure. 

As with other NMCs, methomyl causes rapid acetylcholinesterase (AChE) inhibition, 

typically within 30-60 minutes, at low dose levels and across species. Reactivation of the 

enzyme and therefore recovery of AChE activity occurs within hours for methomyl as is 

typical for the NMCs. Acute exposure, therefore, is the main duration of concern for 

methomyl. Toxicity studies that evaluate AChE inhibition are available via the oral and 

dermal route. Methomyl is classified as “not likely” to be a human carcinogen based on 

carcinogenicity studies in rats and mice. A comparative cholinesterase study (CCA) is 

available, which evaluates AChE activity at the time of peak effect in both adult and 

juvenile rats as well as recovery of AChE activity. Benchmark dose (BMD) analyses of 

the brain and RBC AChE data from oral toxicity studies were updated for methomyl in 

2006. 

An acute inhalation study with both the time to peak effect as well as dose-response is 

required for methomyl. In addition, an immunotoxicity study is required for methomyl 

based on the revised Part 158 guidelines. Once these studies have been received and 

reviewed; HED will reevaluate the points of departure and uncertainty factors for the 

dietary, aggregate, and occupational assessments. 

A highly refined acute dietary risk assessment (F. Fort, D340694, 06/19/2007) was 

conducted using new estimated environmental concentrations (EECs) in conjunction with 

the NMC CRA. The last drinking water assessment for methomyl was completed by the 

Environmental Fate and Effects Division (EFED) during this time as well (D. Young, 

05/02/2007). Seventeen separate drinking water scenarios were modeled. Based on the 

current knowledge of the mode of action for methomyl (i.e., rapid reactivation of 

recovery), like other NMCs, chronic dietary risk assessments are not warranted. An 

updated dietary risk assessment may be required during the registration review process to 

further revise residues in drinking water and food, percent crop treated information and 

any revised points of departure (PoD) or uncertainty factors. 

The residue chemistry database for methomyl is adequate to support the registration 

review process with the exception of the deficiencies that were noted in the 1998 HED 

RED chapter (F. Fort, D245742, 05/05/1998). The registrant has submitted multiple 

studies and waiver requests that are currently under review by HED. 

Methomyl is a restricted use pesticide (based on percent active ingredient) and there are 

currently no homeowner uses for methomyl. However, certain low percentage a.i. 

formulations exist that are not designated as restricted use. Therefore, there is a potential 

for residential handler and post-application exposure. In addition, a residential postapplication assessment will be required due to the use of methomyl on sod farms 

There is a potential for exposure to methomyl during mixing, loading, and applying 

activities. However, as stated previously, acute exposure is the duration of concern for 

methomyl. Since the last risk assessment application rates have been reduced and 

Page 2 of 25 
handheld equipment was prohibited during application. Occupational postapplication 

exposure can occur via the dermal and/or inhalation route. An updated occupational 

assessment will be required based on the most current toxicity data and Agency policies. 

Due to the rapid onset and recovery of AChE effects from methomyl, a new acute 

aggregate risk assessment is the only appropriate aggregate assessment required to 

support registration review. This acute assessment would incorporate any new PoDs or 

uncertainty factors identified for methomyl. 

As part of the revised NMC CRA, the registrant voluntarily cancelled uses of methomyl 

on grapes, and which will be effective in 2010. Use on strawberry had previously been 

voluntarily cancelled by the registrant due to overtolerance residues issues. Additionally, 

mitigation measures in the Methomyl RED also resulted in a reduction in the maximum 

seasonal rate for broccoli, cabbage, cauliflower, celery, Chinese cabbage, sweet corn, 

head lettuce, and tomato. Reductions in the maximum single application rates were made 

for peaches and commercial sod farms. 

Prior to a final registration review decision for methomyl, the Agency will determine if 

there is any new information, such as new hazard or exposure data or changes to the use 

pattern, which would affect the NMC cumulative risk assessment. Should the Agency 

determine that new information on methomyl is available that could potentially impact 

the cumulative risk assessment and result in a risk of concern, the Agency will revisit the 

cumulative risk assessment. 

Introduction 

Methomyl is a broad-spectrum carbamate insecticide registered for use on a wide range of 

field crops, vegetables, fruits, and ornamentals. HED has reviewed the most recent 

exposure and risk assessments (including the N-Methyl carbamate cumulative) for 

methomyl, as well as toxicity data, exposure and usage databases, and the latest Agency 

science policy and risk assessment methodologies to determine if sufficient data are 

available and if updates are needed to support registration review. Additionally, the 

Team conducted a screening-level literature search for any information that would aid in 

assessing human health risks to methomyl. 

Chemical Identity 

Methomyl [S-methyl N-[(methylcarbamoyl)oxy] thioacetimidate] is a broad-spectrum 

carbamate insecticide registered for use on a variety of food and feed crops. Tolerances 

are established under 40 CFR §180.253 for residues of the insecticide methomyl, 

including its metabolites and degradates, in or on a variety of food and feed crops. 

Compliance with the tolerance levels specified is to be determined by measuring only the 

sum of methomyl [S-methyl N-[(methylcarbamoyl)oxy] thioacetimidate] and its oxime 

metabolite (S-methyl N- hydroxythioacetimidate), calculated as the stoichiometric 

equivalent of methomyl, in or on the commodity. The chemical structure and 

nomenclature of methomyl and the physicochemical properties of technical grade 

methomyl are presented in Tables 1 and 2. 

Hazard Identification/Toxicology 

Methomyl is a member of the N-methyl carbamate (NMC) cumulative risk assessment 

(CRA) sharing a common mode of action with other NMC pesticides (inhibition of the 

Page 3 of 25 
acetylcholinesterase enzyme (AChE)). The NMCs react differently than the 

organophosphates (OPs) in that NMCs bind loosely with the enzyme thus allowing 

reactivation of the enzyme. The acute inhibition of acetylcholinesterase (AChE), 

therefore, is the main exposure duration of concern. Moreover, a more sophisticated 

cholinesterase assay methodology has been developed in order to measure enzyme 

inhibition before reactivation occurs. As part of the data requirements from the 1998 

RED as well as the NMC CRA, additional AChE data for methomyl has been submitted 

to the Agency (Table 3A). 

An updated oral benchmark dose (BMD) analysis was performed that utilized all of the 

appropriate AChE data for the methomyl dietary assessment (F. Fort, D340694, 

06/19/2007). This AChE data provides specific information for the refinement of the 

single chemical methomyl assessment for registration review. 

A 21-day dermal toxicity study that evaluates cholinesterase at the critical time is 

available for methomyl. A BMD analysis, however, will need to be performed during the 

registration review process.

Since inhalation exposure is anticipated based on the use profile, an acute inhalation 

study is required. This acute inhalation study would provide AChE data showing the 

time to peak AChE inhibition as well as the dose-response of AChE inhibition at the peak 

inhibition. A study protocol should be provided to the Agency for review before the 

onset of such study. 

Methomyl is classified as “not likely” to be a human carcinogen based on carcinogenicity 

studies in rats and mice. This classification is supported by the lack of mutagenic 

activity. 

A comparative cholinesterase assay is available for methomyl and was included in the 

NMC CRA. Therefore, the FQPA factor is based on a data-derived approach as 

consistent with other NMCs. The current BMD analyses for methomyl are shown in 

Table 3B. It is important to note that PoDs and uncertainty factors (UFs) may change 

during the registration review process when the BMD results and toxicity data are 

reviewed for methomyl. 

An immunotoxicity study is required as a part of new data requirements in the 40 CFR 

Part 158 for conventional pesticide registration. Because the immune system is highly 

complex, studies not specifically conducted to assess immunotoxic endpoints are 

inadequate to characterize a pesticide’s potential immunotoxicity. While data from 

hematology, lymphoid organ weights, and histopathology in routine chronic or 

subchronic toxicity studies may offer useful information on potential immunotoxic 

effects, these endpoints alone are insufficient to predict immunotoxicity. In the absence 

of required studies, EPA may use a database uncertainty factor of up to 10X. An 

immunotoxicity study on methomyl should be conducted (refer to Table 4). Once all data 

have been received and reviewed, the methomyl registration review team recommends 

that the points of departure and safety factors used for risk assessment purposes be 

reexamined and a new risk assessment done, if necessary. 

Page 4 of 25 
Endocrine Disruption

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, and 

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. 

 

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. 

Methomyl is among the group of 58 pesticide active ingredients on the initial list to be 

screened under the EDSP. The Agency will review the EDSP Tier 1 data and any “other 

scientifically relevant information” submitted in response to test orders. Based on this 

review the Agency will determine the need for additional testing. 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/. 

Residue Chemistry 

Methomyl [S-methyl N-[(methylcarbamoyl)oxy] thioacetimidate] is an insecticide 

registered for use on numerous crops. Methomyl is manufactured by E. I. du Pont de 

Nemours & Company, Inc., the basic producer, under the trade name Lannate®. 

Methomyl formulations registered for use on food/feed crops include soluble concentrate 

(SC/C or L) formulations. These products may be applied to crop plants as 

postemergence broadcast applications using ground or aerial equipment. 

The existing residue chemistry database for methomyl is adequate for risk assessment 

purposes with the exceptions noted below. The qualitative nature of the residue(s) of 

methomyl in plants and animals has been adequately identified/characterized and is 

understood. The residue of concern in plants and animals is methomyl. Tolerances are 

established under 40 CFR §180.253 for residues of the insecticide methomyl, including 

its metabolites and degradates, in or on a variety of food and feed crops. Compliance 

with the tolerance levels specified below is to be determined by measuring only the sum 

of methomyl [S-methyl N-[(methylcarbamoyl)oxy] thioacetimidate] and its oxime 

metabolite (S-methyl N- hydroxythioacetimidate), calculated as the stoichiometric 

equivalent of methomyl, in or on the commodity. Adequate methods are available for the 

enforcement of established tolerances, as currently defined. No tolerances have been 

Page 5 of 25 
established or are currently required for any animal commodities. Adequate analytical 

methods exist for data collection and tolerance enforcement. Adequate storage stability, 

processed food, and magnitude of the residue in data exist with the exceptions noted 

below.

Multiple residue chemistry deficiencies were outlined in the 1997 residue chemistry 

chapter (C. Eiden, D303039 and D230187, 02/11/1997). The registrant subsequently 

submitted waiver requests as well as multiple studies to fulfill these deficiencies. 

Depending upon the outcome of these reviews, additional data may be required to support 

registration review. 

 830.7050 U/V Visible Absorption (MRID 45013201) 

 860.1300 Nature of the Residue – Plants (Tomato MRID 46387701) 

 860.1340 Residue Analytical Method (MRID 45297106) 

 860.1380 Storage Stability 

o Bean seed, potato tubers, peanut nutmeat (MRID 45297101) 

o Dry bulb onions (MRID 45297102) 

o Sorghum grain (MRID 45297103) 

 860.1500 Crop Field Trials 

o Bermudagrass and Sorghum Forage (Waiver Request)

o Cotton gin trash (MRID 45297104) 

o Turnip tops (MRID 45297105) 

 860.1850 Confined Rotational Crop Study (Waiver Request)

Dietary Exposure and Risks 

A highly refined acute dietary risk assessment (F. Fort, D340694, 06/19/2007) was 

conducted using new estimated environmental concentrations (EECs) in conjunction with 

the NMC CRA. The last drinking water assessments for methomyl were completed by 

the Environmental Fate and Effects Division (EFED) during this time as well (D. Young, 

05/02/2007). Seventeen separate drinking water scenarios were modeled. Based on the 

current knowledge of the mode of action for methomyl (i.e., rapid reactivation of 

recovery), like other N-Methyl carbamates, chronic dietary risk assessments are not 

warranted. An updated dietary risk assessment may be required during the registration 

review process to further revise residues in drinking water and food, percent crop treated 

information and any revised points of departure (PoD) or uncertainty factors. 

Drinking Water

The Environmental Fate and Effects Division (D. Young, 5/2/07) used Tier-II modeling 

to generate estimated environmental concentrations (EECs) in surface water. Seventeen 

drinking water scenarios were modeled. Only surface water values were used in the 

assessment as these represent upper bound concentrations that would be expected in 

drinking water. Specifically, the Pesticide Root Zone Model and Exposure Analysis 

Model System (PRZM/EXAMS) Index Reservoir was used to generate surface water 

EECs for drinking water. The model is used by OPP to estimate pesticide concentrations 

that may be in surface water due to pesticide use and runoff. The PRZM/EXAMS 

estimates of potential pesticide levels in surface water incorporate pesticide-specific 

properties, simulation of multiple years to reflect climatic variations, and modeling on a 

crop-specific basis. The model and its description are available at the EPA internet site: 

http://www.epa.gov/oppefed1/models/water/. 

Page 6 of 25 
In the dietary assessment, a distribution of estimates of possible concentrations in 

drinking water were used. Approximately 11000 values were generated based on the 

methomyl use pattern. The values were adjusted for regional percent crop area (PCA) 

and represent the complete daily 36 year PRZM EXAMS output distribution with acute 

concentrations ranging from 2.5 to 99 ppb. These results have been characterized as 

conservative, though not unreasonable estimates of possible concentrations in drinking 

water. For the acute assessment, a RDF file was created using these values for the two 

commodities “Water, direct, all sources” and “Water, indirect, all sources” in the residue 

file editor for DEEM-FCID. 

Acute Dietary Exposure (Food Only) and Risk 

The dietary risk analyses were conducted using the Dietary Exposure Evaluation Model 

DEEM-FCIDTM, Version 2.03 which uses food consumption data from the U.S. Department 

of Agriculture’s Continuing Surveys of Food Intakes by Individuals (CSFII) from 1994-1996 

and 1998. HED calculated anticipated residues (ARs) for methomyl based on USDA 

Pesticide Data Program (PDP) and field trial data for multiple commodities. Acute dietary 

exposure assessments were conducted for the general US population and population 

subgroups including all infants (<1 year old), children 1-2, children 3-5, children 6-12, youth 

13-19, adults 20-49, females 13-49, and adults 50+ years old. 

The results of the 2007 analysis indicated that estimated acute dietary exposure and risk (food 

only) exceeded HED's level of concern [i.e., <100 % of the acute population adjusted dose 

(aPAD)] for the population subgroups, children 1 to 2 years old and children 3 to 5 years old, 

at the 99.9th percentile of exposure. The estimated food only dietary exposure and risk for 

the general U.S. population at the 99.9th percentile exposure was 0.001063 or 71% aPAD. 

For children 1 – 2 years old, the most highly exposed population subgroup, and children 3 to 

5 years old, dietary exposure was 0.002234 mg/kg/day or 149% aPAD and 0.001946 

mg/kg/day or 130% of the aPAD, respectively. 

An analysis was also conducted to determine the foods or food forms which contribute the 

most to the exposure estimates. For children 1 to 2 years old, residues in grapes were the 

most significant source of dietary exposure. When grapes are excluded from the dietary 

assessment, the estimated dietary exposure and risk for the general U.S. population at the 

99.9th percentile exposure was 0.000837 or 56% aPAD. For children 1 to 2 years old, the 

most highly exposed population subgroup, dietary exposure was 0.001269 mg/kg/day, or 

85% aPAD. 

Acute Dietary Exposure (Drinking Water Only) and Risk 

Using the DEEM dietary model, the data indicate that drinking water acute risks (from 

surface water sources) are of concern for fourteen of the seventeen drinking water scenarios 

modeled. Risk estimates ranged from 10 to 264% of the aPAD for children 1-2 years old and 

23 to 622% of the aPAD for infants (<1 years old) (see Table 4). These risk estimates are 

considered conservative since the food diaries used by Dietary Exposure Evaluation ModelFood Consumption Intake Database (DEEM-FCID Version 2.03) are based on total daily 

intake. The estimated risks are overestimates to the extent that food and drinking water are 

consumed throughout the day, rather than during only one event, and this assessment does 

not account for recovery of cholinesterase between exposure events. Consequently, HED 

further refined the acute risk from drinking water by incorporating the time and amounts 

consumed for each eating occasion from the USDA CSFII food diaries to estimate exposures 

Page 7 of 25 
and risks for each eating occasion throughout the day and factoring in the cholinesteraseinhibition half-life related to methomyl exposure. The resulting estimated risks at the per 

capita 99.9th percentile are below the level of concern for all but one drinking water scenario. 

For infants, the estimated risks at the per capita 99.9th percentile exceed the level of concern 

under the Illinois corn scenario (101% - 176% of the aPAD). 

Chronic

Due to the rapid recovery of AChE activity for methomyl, the acute exposure from 

methomyl is the main duration of concern.

Conclusions 

The use on grapes is being deleted from methomyl labels due to dietary risk concerns and 

will be effective in 2010. An updated dietary risk assessment has not been conducted 

since that time, but will be required during the registration review process to further 

revise residues in drinking water and food, percent crop treated information and any 

revised acute oral point of departure (PoD) or uncertainty factors. 

Residential Exposure and Risks 

Methomyl is a restricted use pesticide (based on percent active ingredient) and there are 

currently no homeowner uses for methomyl. However, certain low percentage a.i. 

formulations exist that are not designated as restricted use. Therefore, there is a potential 

for residential handler and post-application exposure. In addition, a residential postapplication assessment will be required due to the use of methomyl on sod farms. 

Residential exposure was most recently assessed in the Revised N-methyl Carbamate 

Cumulative Risk Assessment (NMC CRA, 2007). The assessment included only 

drinking water and dietary assessment for methomyl as part of the cumulative risk 

assessment. The last occupational/residential human health risk assessment (J. Leahy, 

D230188, 3/21/1997 and J. Leahy, D237093, 3/25/1998) was completed for the 1998 

Registration Eligibility Document. 

Residential Handlers

There are currently no registered homeowner uses for methomyl, however, because the 

methomyl scatter bait, bait station, and paste formulations (Reg no. 270-255, 2724-274, 

7319-6, and 53871-3) are not designated as restricted use pesticides, these potential 

handler exposure scenarios should be assessed for both dermal and inhalation exposure 

and risk as part of registration review. 

Residential Postapplication

The three post-application scenarios discussed in the 1998 Occupational and Residential 

Exposure Assessment (J. Leahy, D230188, 03/21/1997 and J. Leahy, D237093, 

03/25/1998) were (1) post-application dermal for “U-pick” peaches, (2) incidental dermal 

exposure for pelleted baits in public places, and (3) ingestion of bait pellets. HED had 

determined that there is potential for post-application exposure to children who come into 

contact with pellets in public places through the dermal and incidental oral routes of 

exposure. The MOEs for post-application dermal “U-pick” did not exceed HED’s level 

of concern (MOEs > 100). At the time of the assessment, HED concluded that dermal 

exposure to pelleted baits would be less of an exposure than the “U-pick” scenario, and 

therefore, exposure would be below that which would present a concern. The incidental 

Page 8 of 25 
oral exposure to pelleted baits was not quantitatively assessed but HED concluded if 

proper application measures are taken, potential incidental oral exposure should not 

present significant risk. Inhalation exposure was not assessed in this previous assessment 

based on the low vapor pressure of methomyl. However, the need for an inhalation 

assessment will be re-visited based upon the most current standards, guidance, and 

policies at the time of registration review. 

The most recent labels suggest that methomyl is not to be used inside or around homes or 

any other places where children are likely to be present and residential use of the product 

is prohibited. The most current registered labels for methomyl use on agricultural crops 

(Reg no. 5742-2, 352-342, and 352-384) also prohibit use of methomyl on any 

commercial crop turned into a “U-pick”, “pick your own”, or similar operation. 

An updated residential post-application exposure assessment may be necessary due to use 

of methomyl on sod farms. Application to turf grass will likely warrant adult and child 

post-application dermal and inhalation exposure assessment along with a child incidental 

oral (hand-to-mouth) assessment. 

Conclusions

The three residential post-application exposure scenarios presented previously resulted in 

risks that did not quantitatively or qualitatively exceed HED’s level of concern (MOEs > 

100). No additional uses have been registered for residential use since the previous 

assessment. Based on the restricted use sites for the scatter bait, bait station, and paste 

formulations of methomyl a residential post-application assessment for those particular 

exposure scenarios may not be necessary, however, the application of methomyl on sod 

farms to turf does warrant a post-application residential exposure assessment. In addition, 

current use patterns will require reassessment of all exposure and risk estimates if 

additional guidelines, policies, and standard operating procedures change at the time of 

registration review. 

Aggregate Risk Assessment 

The aggregate risk assessment evaluates the combined risk from dietary exposure (food 

and water) and any non-occupational (residential) uses. Due to the non-restricted status 

of certain uses, a new acute aggregate assessment will be required combining food, 

drinking water, and any residential exposures, as appropriate. As noted above, a revised 

acute aggregate dietary exposure assessment (food plus drinking water) resulted in risks 

above HED’s level of concern for only the Illinois corn drinking water scenario. Once any 

new data have been reviewed and the appropriate exposure assessments have been 

completed, a new aggregate risk assessment will be needed to support the registration 

review of methomyl. 

Aggregate Exposure and Risk (Food plus Drinking Water)

An acute aggregate assessment was also conducted combining food and drinking water. 

Since food alone exceeds HED’s level of concern, the aggregate assessment was performed 

without grapes, the major food driver. Additionally, as discussed above, drinking water risks 

alone without the incorporation of eating occasions also exceeds our level of concern. 

Therefore, HED refined the aggregate (food plus drinking water) assessment by considering 

eating occasions. The analyses again showed that the estimated risk at the 99.9th percentile of 

exposure exceeds our level of concern for only the Illinois corn drinking water scenario. 

Page 9 of 25 
Risks for this scenario for infants and children were 176 and 116% respectively. Sensitivity 

analyses showed that drinking water was the major risk driver. 

Occupational Exposure and Risks

Methomyl is a broad spectrum insecticide used in agricultural and commercial settings on 

a wide variety of food and non-food sites and on livestock and foodpreparation/processing premises. Methomyl is formulated as a composition product (92 

% active ingredient), a liquid (29 % active ingredient), a wettable powder (90% active 

ingredient), a bait station, paste, and scatter bait (1% active ingredient), and as a granular 

(5% active ingredient). 

For agricultural use sites, methomyl can be applied with chemigation (overhead and drop 

irrigation), aerial equipment, groundboom sprayers, standard granular ground broadcast 

and banded spreaders, granular row planters, airblast sprayers. Handheld equipment is 

prohibited. The bait station and scatter bait formulations are applied via hand dispersion 

or directly from the shaker can. The paste formulation is applied via brush. Application 

rates vary from 0.0025 to 1 lb active ingredient per acre depending upon the application 

scenario. For bait stations and scatter bait, the maximum application rate is 0.25 lbs 

product per 500 ft2

. Methomyl can be applied to a variety of food, feed, and fiber crops, 

animal facilities, food/feed processing and preparation facilities, and commercial sites. 

There is a potential for short- and intermediate-term exposure to methomyl during 

mixing, loading, and applying activities. Fifteen exposure scenarios were assessed in the 

previous human health risk assessment (F. Fort, D245742, 05/05/1998). An additional 3 

scenarios were not assessed due to lack of data: dust application, mixing pelleted baits 

with water to form the paste formulation, and flagging aerial bait applications. All 

scenarios that were quantitatively assessed did not exceed HED’s level of concern 

(MOEs > 100) with varying levels of personal protective equipment (i.e., double layer 

clothing, chemical resistant gloves, dust/mist respirators) and/or engineering controls 

(i.e., water soluble bags). 

Post-application exposure and risk was calculated using a study (MRID No. 410323-01) 

based on an airblast application to grapes. The study looked at both foliage and soil 

dislodgeable residue as well as worker reentry exposure measurements. High and low 

exposure crops were assessed with a range of transfer coefficients to evaluate potential 

post-application dermal exposure for workers. Post-application exposures following 

applications of dusts, baits, and pastes using aerial, ground equipment, and paint brushes 

were not assessed due to lack of data. Post-application inhalation exposure was not 

assessed due to the low vapor pressure of methomyl. 

Occupational Handlers

Table 4 summarizes the occupational uses (agricultural and non-agricultural) along with 

exposure scenarios and application rates for methomyl as determined from the most 

current labels. As part of the NMC CRA (2007) application rates for the following crops 

were reduced: broccoli, cabbage, cauliflower, celery, Chinese cabbage, corn (sweet), 

head lettuce, tomato, peaches, and commercial sod farms. However, the maximum 

application rate on the current product labels is reflected in the range of application rates 

that were assessed in the 1998 risk assessment. The risks based on the previous risk 

assessment do not exceed HED’s level of concern (MOEs > 100) with varying levels of 

Page 10 of 25 
personal protective equipment (PPE) (i.e., double layer clothing, chemical resistant 

gloves, dust/mist respirators) and/or engineering controls (i.e., water soluble bags). The 

degree of PPE or engineering controls necessary to mitigate exposure may be reduced 

based on the lowered application rates. 

Conclusions

Since the last human health exposure and risk assessment (F. Fort, D245742, 05/05/1998) 

the crop use sites and application scenarios have remained the same with the exception of 

the cancellation of methomyl use on strawberries (2007) and grapes (2010) and the 

restriction on handheld devices (the belly grinder scenario previously assessed is no 

longer allowed). The reduction in application rates are reflected in the range of 

applications that were assessed previously. 

An updated exposure and risk assessment may be necessary during registration review to 

reflect the reduction in application rate and corresponding mitigation measures. Updated 

assessments may also be necessary to incorporate the most current unit exposures and 

potential exposure from the inhalation route. Additionally, any changes in standards, 

guidelines, and/or policies will need to be considered during registration review. 

Occupational Postapplication

Occupational postapplication exposure can occur via the dermal and/or inhalation route. 

Post-application exposure and risk was calculated using a study (MRID No. 410323-01) 

based on an application to grapes at a rate of 0.9 lb ai/acre using an airblast sprayer. The 

study looked at both foliage and soil dislodgeable residue as well as worker reentry 

exposure measurements. High and low exposure crops were assessed with a range of 

transfer coefficients to calculate potential post-application dermal exposure and risk 

estimates for workers. Specific restricted entry intervals (REI) were determined for 

certain crops and activities for which MOEs do not reach 100 on day zero after treatment. 

The most current label establishes the following REIs: grapes = 7 days, peaches = 4 days, 

apple, cotton, grapefruit, lemon, nectarine, orange, tangelo, tangerine = 3 days, and all 

other worker protection standard (WPS) uses = 48 hours. Because methomyl is an acute 

toxicity category I for primary eye irritation, the minimum of a 48 hour REI is 

appropriate. 

Post-application exposures following applications of dusts, baits, and pastes using aerial, 

ground equipment, and paint brushes were not assessed due to lack of data. 

Conclusions

There are many cultural practices which require hand labor that may lead to the exposure 

of fieldworkers such as harvesting, irrigation, scouting or weeding. Exposure and risk 

estimates will need to be updated with the most current transfer coefficient values that 

will be developed based on the study specific data or data from the Agricultural Reentry 

Task Force and as discussed at the 2008 meeting of the FIFRA Scientific Advisory Panel 

meeting on this issue. Additionally, the inhalation route of exposure will need to be 

considered contingent upon the most current standards, guidance, and policies at the time 

of registration review. 

Public Health and Pesticide Epidemiology Data 

Page 11 of 25 
An updated review of methomyl incident reports was recently prepared by HED (S. 

Winfield, D376770, 05/20/2010). For this evaluation, both the OPP Incident Data 

System (IDS) and the Centers for Disease Control and Prevention/National Institute for 

Occupational Safety and Health (CDC/NIOSH) Sentinel Event Notification System for 

Occupational Risk-Pesticides (SENSOR) database were consulted for pesticide incident 

data on the active ingredient methomyl. 

For IDS 43 cases were reported for methomyl in the United States from 2002 to the 

present. Of these cases, thirteen were reviewed because in these cases methomyl was 

used as a single chemical only and therefore these cases provide more certain information 

about the potential effects of methomyl exposure. Five of the incidents involved 

intentional ingestion/misuse of the product. Six incidents involved agricultural handlers 

using methomyl: four in seemingly typical ways and two where equipment 

malfunctioned/leaked (all of these resulted in moderately severe symptoms). The 

symptoms most often reported were neurological (27%) followed by gastrointestinal 

(23%) and ocular (20%). 

For NIOSH SENSOR from 1998 to 2006, there are 60 cases reported for methomyl in the 

database. Of these cases, 21 were reviewed because, in these cases, methomyl was used 

as a single chemical only and had a certainty classification of definite, probable, or 

possible, as these cases provide more certain information about the potential effects of 

methomyl exposure. All of the reviewed cases were classified as low or moderate 

severity. The health effects reported include: neurological (81%), gastrointestinal (71%), 

ocular (24%), respiratory (19%), cardiovascular (19%), dermal (14%), and genitourinary 

(5%). Ten cases were exposed in an occupational handler setting, including mixing, 

loading and applying methomyl. The health effects most often reported for these cases 

include: neurological (80%) and gastrointestinal (80%). 

Tolerance Assessment and International Harmonization 

Tolerances are established for residues of the insecticide methomyl, including its 

metabolites and degradates, in or on the commodities in Table 7. The Codex 

Alimentarius Commission and Canada have established maximum residue limits (MRLs) 

for methomyl but some are not harmonized with all US tolerances. The Codex MRLs are 

based on sum of methomyl and thiodicarb, expressed as methomyl (methomyl is a 

metabolite of thiodicarb). MRLs related to methomyl and thiodicarb are combined into a 

single list. Mexico has not currently established MRLs for methomyl. Any methomyl 

tolerances reassessed during the registration review process will be considered for 

possible harmonization with international MRLs. 

Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered 

in this human health risk assessment, in accordance with U.S. Executive Order 12898, 

"Federal Actions to Address Environmental Justice in Minority Populations and LowIncome Populations," 

http://www.epa.gov/compliance/resources/policies/ej/exec_order_12898.pdf. The Office 

of Pesticide Programs (OPP) typically considers the highest potential exposures from the 

legal use of a pesticide when conducting human health risk assessments, including, but 

not limited to, people who obtain drinking water from sources near agricultural areas, the 

Page 12 of 25 
variability of diets within the U.S., and people who may be exposed when harvesting 

crops. Should these high exposures indicate potential risks of concern, OPP will further 

refine the risk assessments to ensure that the risk estimates are based on the best available 

information. 

Cumulative Risk Assessment 

The Food Quality Protection Act (FQPA) requires the Agency to consider the cumulative 

risks of chemicals sharing a common mechanism of toxicity. Methomyl is a member of 

the N-methyl carbamate common mechanism group. The most recent cumulative risk 

assessment for the NMC carbamates was issued for comment on September 26, 2007 and 

is available at http://www.epa.gov/oppsrrd1/REDs/nmc_revised_cra.pdf. 

Prior to a final registration review decision for methomyl, 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 would affect the cumulative risk assessment. Should 

the Agency determine that new information on methomyl is available that could 

potentially impact the cumulative risk assessment and result in a risk of concern, the 

Agency will revisit the cumulative risk assessment. 

Human Studies 

Methomyl risk assessments rely in part on data from studies in which adult human 

subjects were intentionally exposed to a pesticide or other chemical. An oral human 

study with methomyl was considered to be ethically conducted and scientifically valid by 

the Human Studies Review Board (HSRB) in 2006. Studies such as those from the 

Pesticide Handlers Exposure Database (PHED), the Outdoor Residential Exposure Task 

Force (ORETF), and the Agricultural Reentry Task Force (ARTF) database have been 

reviewed by the Agency and found on the basis of available evidence to have been 

neither fundamentally unethical nor significantly deficient relative to standards of ethical 

research conduct prevailing when they were conducted. There is no barrier in EPA's 

"Protection of Human Subjects" regulation to reliance on these studies. 

Data Requirements

HED does not anticipate that additional residue chemistry, toxicology or 

occupational/residential exposure data will be required for the methomyl registration 

review process, with the exception of the following studies listed below: 

 Immunotoxicity Study (OPPTS 870.7800) (See Table 5A for more details). 

 Non-guideline Acute Inhalation Study (See Table 5B for more details). 

 Multiple residue chemistry deficiencies were outlined in the 1997 residue 

chemistry chapter (C. Eiden, D303039 and D230187, 02/11/1997). The registrant 

subsequently submitted waiver requests as well as multiple studies to fulfill these 

deficiencies. Depending upon outcome of these reviews, additional data may be 

required to support registration review. 

Page 13 of 25 
Table 1. Methomyl Nomenclature 

Compound: Parent Chemical Structure 

N

O N

H

3CH CH3

S

CH3

O

Common name Methomyl 

IUPAC name S-methyl (EZ)-N-(methylcarbamoyloxy)thioacetimidate 

CAS name methyl N-[[(methylamino)carbonyl]oxy]ethanimidothioate 

CAS # 16752-77-5 

Empirical Formula C5H10N2O2S 

End-use product/EP Lannate

Table 2. Physicochemical Properties of Methomyl 

Parameter Value Reference 

Appearance white, crystalline solid with 

a slightly sulfurous odor 

Melting point/range 78-79°C 

Water solubility (g/100 g) 5.8 

Organic solvents (g/100 g) methanol: 100 

acetone: 72 

ethanol: 42 

isopropanol: 22 

Toluene: 3 

Methomyl Product Chemistry Chapter (C. 

Eiden, D203039 and D230187, 02/11/1997) 

Vapor pressure at 25°C 6.65 mPa http://extoxnet.orst.edu/pips/methomyl.htm

Table 3A: New studies available since the time of the 1998 methomyl RED 

Study MRID Route AchE Data 

Comparative Cholinesterase Assay (CCA) 46646401 oral brain, RBC 

Reversibility Study 44472001 oral brain, RBC 

Acute Neurotoxicity Study 44487501 oral Brain, RBC 

Human RBC AChE Study 44721401 oral RBC 

NHEERL NA oral brain, RBC 

Subchronic Neurotoxicity Study 44666201 oral brain, RBC 

Page 14 of 25 
Table 3B: Bench Mark Dose Analysis Results for Methomyl1

Brain RBC Route of Exposure BMD10 (mg/kg) BMDL10 (mg/kg) BMD10 (mg/kg) BMDL10 (mg/kg)

Oral2 NA NA 0.04 mg/kg 0.03 mg/kg

Dermal BMD analysis to be performed as part of registration review 

Inhalation Inhalation study required as part of registration review 1

Brain ChE data not available since a human study provides only RBC ChE data. 

2

The 2007 revised aPAD was based on AChE data of 0.0015 mg/kg/day, based on a RBC PoD of 0.03 

mg/kg with 10x intraspecies factor, 1x interspecies factor, and 2x FQPA RBC factor. 

Table 4. Summary of Representative Occupational Use Patterns, Formulations, and Application 

Rates for Methomyl 

Product Formulation Application 

Equipment Use Sites Maximum Application Rates

Farnam Die FlyTM 

(EPA Reg No 270-255) 

Granular 

1% 

Hand dispersal of 

scatter bait and bait 

stations 

Where children are 

not present, Feed 

lots, Dairies, Stables, 

Broiler houses, Hog 

houses, Livestock 

barns, Meat and 

poultry processing 

establishments, 

Beverage plants, 

Canneries, Food 

processing 

establishments, On 

walkways of caged 

layer houses. Other 

additional 

commercial (nonresidential) use sites 

are allowed when 

using bait stations 

0.0025 lb ai/500 sq ft 

Golden Marlin RF® 128 Fly 

Killer 

(EPA Reg No 2724-274) 

Granular 

1% 

Shaker can and bait 

stations 

Scatter Bait: Certain 

commercial 

agricultural 

production facilities 

where children are 

not present, feedlots, 

broiler houses, 

livestock barns, 

outside of canneries, 

beverage plants, meat 

and poultry 

processing plants, 

food processing 

plants, commercial 

refuse dumpsters 

Bait Stations: secured 

4 feet above the 

ground in stables, 

outside of milking 

parlors, kennels, fast 

food establishments, 

restaurants, 

commissaries, 

bakeries, 

supermarkets, refuse 

dumpsters, and 

warehouses 

0.0025 lb ai/500 sq ft 

Lurectron® Scatterbait Granular Hand dispersal, bait Scatter bait: Outside 0.0025 lb ai/500 sq ft

Page 15 of 25 
(EPA Reg No 7319-6) 1% stations, and brush on 

paste 

of feed lots, poultry 

houses, livestock 

barns, canneries, 

beverage plants, meat 

and poultry 

processing 

establishments, food 

processing plants, 

and commercial 

refuse dumpsters, on 

walkways in caged 

layer houses 

Bait stations: secured 

4 feet above the 

ground in stables, 

outside of feed lots, 

poultry houses, 

livestock barns, 

canneries, beverage 

plants, meat and 

poultry processing 

establishments, food 

processing plants, 

kennels, and refuse 

dumpsters, in fenced 

areas around 

restaurants, 

supermarkets, and 

bakeries, and in 

caged layer houses. 

Paste: apply paste on 

walls, windowsills, 

and support beamson 

the outside of 

livestock barns and 

poultry houses 

Stimukil Fly Bait 

(EPA Reg No 53871-3) 

Granular 

1% 

Hand dispersal, bait 

stations, and brush on 

paste 

Bait Station: Do not 

use around or inside 

homes or other places 

where children are 

likely to be present. 

Hang Fly Bait out of 

reach of food 

producing animals or 

pets (at least 4 feet 

off the ground). Do 

not place bait station 

in reach of children. 

Use around the 

outside of broiler 

houses, kennels, 

canneries, beverage 

processing plants, 

meat and poultry 

processing plants, 

food processing 

plants and refuse 

dumpsters, associated 

with these 

establishments, and 

inside of caged layer 

houses. May also be 

used in fenced or 

otherwise enclosed 

areas inaccessible to 

0.0025 lb ai/500 sq ft 

Page 16 of 25 
children, and around 

the outside of 

restaurants, 

supermarkets, 

commissaries, and 

bakeries. 

Scatter bait: limited 

solely to the outside 

of certain 

commercial 

establishments where 

children will not be 

present, such as feed 

lots, poultry houses, 

livestock barns, 

canneries, beverage 

plants, meat and 

poultry processing 

establishments, 

commercial refuse 

dumpters, which are 

fenced or enclosed, 

and food processing 

plants. 

Paste: apply paste on 

walls, windowsills, 

and support beams 

where flies usually 

land such that 

children, poultry, 

cattle, or other 

animals cannot come 

into contact with the 

paste. 

Methomyl 5G Granules 

(EPA Reg No 57242-2) 

Granular 

5% 

Ground equipment 

EXCLUDING 

handheld equipment 

Corn 0.15 lb ai/A 

Dupont Lannate® SP 

(EPA Reg No 352-342) 

Water soluable powder in 

water soluable bags 

90% 

Ground, aerial, and 

chemigation, 

EXCLUDING 

handheld equipment 

Alfalfa, Anise, 

Asparagus, Avocado, 

Barley, Beans, Beets, 

Bermudagrass, 

Blueberries, 

Broccoli, Brussels 

sprouts, Cabbage, 

Carrot, Cauliflower, 

Celery, Chicory, 

Chinese cabbage, 

Collards, Corn, 

Cotton, Cucumber, 

Eggplant, Endive, 

Garlic, Grapefruit, 

Grapes, Horseradish, 

Leafy green 

vegetables, Lemon, 

Lentils, Lettuce, 

Melons, Mint, 

Nectarine, Oats, 

Onions, Oranges, 

Peaches, Peanuts, 

Pears, Peas, Pecans, 

Peppers, 

Pomegranates, 

Potato, Sorghum, 

Soybeans, Spinach, 

Sugar beet, Summer 

0.9 lb ai/A1

Page 17 of 25 
squash, Tangelo, 

Tangerine, Tobacco, 

Tomato, Turf, Wheat 

DuPont Lannate® LV 

(EPA Reg No 352-384) 

Water soluable liquid 

29% 

Ground, aerial, and 

chemigation, 

EXCLUDING 

handheld equipment 

 Alfalfa, Anise, 

Apple, Asparagus, 

Avocado, Barley, 

Beans, Beets, 

Bermudagrass 

pasture, Blueberries, 

Broccoli, Brussels 

sprouts, Cabbage, 

Carrot, Cauliflower, 

Celery, Chicory, 

Chinese cabbage, 

Collards, Corn, 

Cotton, Cucumber, 

Eggplant, Endive, 

Garlic, Grapefruit, 

Grapes, Horseradish, 

Leafy green 

vegetables, Lemon, 

Lentils, Lettuce, 

Melons, Mint, 

Nectarine, Oats, 

Onions, Oranges, 

Peaches, Peanuts, 

Pears, Peas, Pecans, 

Peppers, 

Pomegranates, 

Potato, Rye, 

Sorghum, Soybeans, 

Spinach, Sugar beets, 

Summer squash, 

Tangelo, Tangerine, 

Tobacco, Tomato, 

Turf, Wheat 

0.9 lbs ai/A2

1 Application rate is calculated based on the assumption that the ai is 90% of the dry weight of the total product. 

2 Application rate is calculated based on the assumption that the water soluble liquid formulation contains 2.4 lbs active 

ingredient pre gallon. 

Page 18 of 25 
Table 5A: Guideline Number: 870.7800 

Study Title: Immunotoxicity on Methomyl

Rationale for Requiring the Data 

This is a new data requirement under 40 CFR Part 158 as a part of the data 

requirements for registration of a pesticide (food and non-food uses). 

The Immunotoxicity Test Guideline (OPPTS 870.7800) prescribes functional 

immunotoxicity testing and is designed to evaluate the potential of a repeated 

chemical exposure to produce adverse effects (i.e., suppression) on the immune 

system. Immunosuppression is a deficit in the ability of the immune system to 

respond to a challenge of bacterial or viral infections such as tuberculosis (TB), 

Severe Acquired Respiratory Syndrome (SARS), or neoplasia. Because the 

immune system is highly complex, studies not specifically conducted to assess 

immunotoxic endpoints are inadequate to characterize a pesticide’s potential 

immunotoxicity. While data from hematology, lymphoid organ weights, and 

histopathology in routine chronic or subchronic toxicity studies may offer useful 

information on potential immunotoxic effects, these endpoints alone are insufficient 

to predict immunotoxicity. 

Practical Utility of the Data 

How will the data be used? 

Immunotoxicity studies provide critical scientific information needed to 

characterize potential hazard to the human population on the immune system from 

pesticide exposure. Since epidemiologic data on the effects of chemical exposures 

on immune parameters are limited and are inadequate to characterize a pesticide’s 

potential immunotoxicity in humans, animal studies are used as the most sensitive 

endpoint for risk assessment. These animal studies can be used to select endpoints 

and doses for use in risk assessment of all exposure scenarios and are considered a 

primary data source for reliable reference dose calculation. For example, animal 

studies have demonstrated that immunotoxicity in rodents is one of the more 

sensitive manifestations of TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) among 

developmental, reproductive, and endocrinologic toxicities. Additionally, the EPA 

has established an oral reference dose (RfD) for tributyltin oxide (TBTO) based on 

observed immunotoxicity in animal studies (IRIS, 1997). 

How could the data impact the Agency's future decision-making? 

If the immunotoxicity study shows that the test material poses either a greater or a 

diminished risk than that given in the interim decision’s conclusion, the risk 

assessments for the test material may need to be revised to reflect the magnitude of 

potential risk derived from the new data. 

 

If the Agency does not have this data, a 10X database uncertainty factor may be 

applied for conducting a risk assessment from the available studies.

Page 19 of 25 
Table 5B.: Non-guideline 

Study Title: Acute Inhalation Toxicity of Methomyl 

Rationale for Requiring the Data 

This acute inhalation toxicity study evaluates cholinesterase (ChE) inhibition of an N-methyl 

carbamate (NMC) pesticide at the time of peak inhibition and recovery as well as provides 

dose-response ChE data. This study is critical for NMCs with a use pattern in which there is 

potential for inhalation (e.g., professional applicators, green house, residential use etc) 

exposure. The study design is critical to the mode of action of the NMCs (i.e., rapid ChE 

inhibition and reactivation). In this two part study, animals are first exposed (nose only/whole 

body) to a concentration of the test material for 8 hours and ChE activity measured 

periodically during exposure and post-exposure to ascertain the time of peak RBC and brain 

ChE inhibition as well as the time required for recovery of ChE activity. The second part of 

the study involves exposing the animals (M&F) to varying concentrations (including controls) 

for 8 hours with ChE activity measured at the time of peak inhibition. Concentrations should 

be established to determine approximately a 10% ChE inhibition level (RBC and brain) from 

control animals. A detailed toxicological examination including the histopathology of the 

respiratory system is not required due to the specific mode of action of the NMCs. This 

route-specific study would provide ChE data for hazard characterization, dose response 

assessment, and a dose and endpoint for assessing potential risks via the inhalation route for 

methomyl. 

Practical Utility of the Data 

How did the Agency make its re-registration decision without these data? 

This acute inhalation study provides critical scientific information needed to characterize 

potential hazard (i.e., ChE inhibition) to the human population from methomyl exposure. In 

the case of methomyl, an acute inhalation study that provides ChE inhibition data is currently 

unavailable. An oral study that provided ChE data was used in lieu of the acute inhalation 

study. An additional Uncertainty Factor was not applied to the 1998 inhalation assessment. 

At that time, it was believed that oral studies would be protective of the inhalation route of 

exposure. However, based on the current knowledge of the mode of action for the NMCs, the 

oral study currently used may underestimate the amount of ChE inhibition from an acute 

inhalation exposure. This non-guideline acute inhalation study will characterize hazard and 

provide specific mode of action (i.e., ChE) data for an inhalation assessment that is protective 

for registration review. 

How will the data be used? 

This study will identify hazard (i.e., ChE inhibition) following an acute inhalation exposure at 

the determined time of peak ChE inhibition. This ChE data will be used as the point of 

departure in the single chemical occupational/residential risk assessments, and may result in a 

lower point of departure. 

If the Agency does not have this data, a 10X database uncertainty factor may be applied for 

conducting a risk assessment from the available studies. 

Page 20 of 25 
Methomyl: Maximum Residue Limits (MRL) Table 

Table 6. Summary of US and International Tolerances and Maximum Residue Limits 

US Canada Mexico2 Codex3 

Residue Definition: 

40 CFR 180.253 Methomyl (S -methyl N 

-[(methylcarbamoyl)oxy] thioacetimidate) 

S-methyl-N-

(methylcarbamoyloxy) 

thioacetimidate

sum of 

methomyl and 

thiodicarb, 

expressed as 

methomyl. 

MRLs related 

to methomyl 

and (154) 

thiodicarb are 

combined into 

a single list. 

Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg) 

Commodity US Canada Mexico2 Codex 

Alfalfa, forage 10 Alfalfa 

fodder 20

Alfalfa, hay 10

Apple 1 0.5 0.3

Asparagus 2 2

Avocado 2

Barley, grain 1 2

Barley, hay 10

Barley, straw 10

Straw of 

cereal grains

10

Bean, dry, seed 0.1(N) 0.05

Bean, forage 10 Bean, fodder 

10

Bean, succulent 2

1 (except 

broad bean 

and soya 

bean)

Beet, garden, tops 6

Bermudagrass, forage 10

Bermudagrass, hay 40

Blueberry 6 6.0

Broccoli 3 7

(proposed)

Brussels sprouts 2 7

(proposed)

Cabbage 5 5.0 7

(proposed)

Cabbage, Chinese, bok choy 5 7

(proposed)

Page 21 of 25 
Table 6. Summary of US and International Tolerances and Maximum Residue Limits 

US Canada Mexico2 Codex3 

Cabbage, Chinese, napa 5 7

(proposed)

Cauliflower 2 7

(proposed)

Celery 3 0.5 3

(proposed)

Collards 6

Corn, field, forage 10

Corn, field, grain 0.1 0.02 (*) 

Corn, field, stover 10

Corn, pop, grain 0.1

Corn, pop, stover 10

Corn, sweet, forage 10

Corn, sweet, kernel plus cob 

with husks removed 0.1(N)

Corn, sweet, stover 10

Cotton, undelinted seed 0.1(N) 0.2

Cucurbits 0.2(N) 0.1

Dandelion, leaves 6 30

Endive 5 30

Grape 5 4.0 0.3

Grapefruit 2 Citrus fruits

1.0

Citrus fruits

1

Hop, dried cones1 12

Kale 6 7

Leek 3.0

Lemon 2 Citrus fruits

1.0

Citrus fruits

1

Lentil, seed 0.1

Lettuce 5 2.0 Head, leaf 

0.2

Mustard greens 6 7

Nectarine 5

Oat, forage 10

Oat, grain 1

Oat, hay 10

Oat, straw 10

Straw of 

cereal grains

10

Onion, green 3

Orange, sweet 2 1.0 1

Parsley, leaves 6 30

Page 22 of 25 
Table 6. Summary of US and International Tolerances and Maximum Residue Limits 

US Canada Mexico2 Codex3 

Pea 5

Pods and 

succulent=im

mature seeds 

5

Pear (Regional Registration) 4

Pea, field, vines 10

Peach 5 0.2

Peanut 0.1(N)

Pecan 0.1

Pepper 2 0.7

Peppermint, tops 2

Pomegranate 0.2(N)

Rye, forage 10

Rye, grain 1

Rye, straw 10

Straw of 

cereal grains

10

Sorghum, forage 1

Sorghum, grain 0.2(N)

Soybean 0.2(N) Dry, 0.2

Soybean, forage 10 Fodder, 0.2

Spearmint, tops 2

Spinach 6 30

Strawberry 2 1.0

Swiss chard 6 30

Tangerine 2 Citrus fruits

1.0

Citrus fruits

1

Tomato 1 1

Turnip, greens 6

Vegetable, brassica, leafy, 

group 5 6.0 30(proposed)

Vegetable, fruiting 0.2(N) 0.1

Vegetables, leafy [exc. beet 

(tops), broccoli, Brussels 

sprouts, cabbage, cabbage, 

Chinese, cauliflower, celery, 

collards, dandelions, endive 

(escarole), kale, lettuce, 

mustard greens, parsley, 

spinach, Swiss chard, turnip, 

greens (tops), and watercress] 

0.2(N)

30 (including 

Brassica 

leafy)

(proposed).

See lettuce.

Vegetable, root 0.2(N)

Watercress 6

Wheat, forage 10 Straw and 

fodder, dry 5

Page 23 of 25 
Table 6. Summary of US and International Tolerances and Maximum Residue Limits 

US Canada Mexico2 Codex3 

Wheat, grain 1 2

Wheat, hay 10

Wheat, straw 10 5

MRLs with no US equivalent 

Beans, except broad bean and 

soya bean 

1

Citrus pulp, Dry 3

Common bean (pods and/or 

immature seeds) 

1

Cotton seed, hulls 0.2

Cotton seed, meal 0.05

Cotton seed oil, Edible 0.04

Edible offal (mammalian) 0.02 (*)

Eggs 0.02 (*)

Maize oil, edible 0.02 (*)

Meat (from mammals other 

than marine mammals) 

0.02 (*)

Milks 0.02 (*)

Mint hay 0.5

Onion, bulb 0.2

Plums 1

Potato 0.02 (*)

Poultry meat 0.02 (*)

Poultry, edible offal 0.02 (*)

Rape seed 0.05

Soya bean hulls 1

Soya bean meal 0.2

Soya bean oil, crude 0.2

Soya bean oil, refined 0.2

Straw, fodder (dry) and hay of 

cereal grains and other grass 

like plants 

10

Wheat bran, unprocessed 3

Wheat flour 0.03

Wheat germ 2

1

There are no U.S. registrations for use of methomyl on hop, dried cone, as of February 14, 1990. 

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes. 

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP 

= processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be 

measured on the fat portion of the sample. MRLs indicated as proposed have not been finalized by the 

CCPR and the CAC. 

Page 24 of 25 
Page 25 of 25 

Table 7: HED Memoranda Relevant to Registration Review 

Author Barcode/TXR # Date Title 

S. Winfield D376770 05/20/2010 Methomyl Incident Report 

F. Fort D340694 06/19/2007 Acute, Probabilistic Aggregate Dietary 

(Food and Drinking Water) Exposure and 

Risk Assessment for the Reregistration 

Eligibility Decision. 

F. Fort D245742 05/05/1998 The HED Chapter of the Reregistration 

Eligibility Decision Document (RED) for 

Methomyl. 

J. Leahy D237093 03/25/1998 Revised OCCUPATIONAL AND 

RESIDENTIAL EXPOSURE 

ASSESSMENT 

AND RECOMMENDATIONS FOR THE 

REREGISTRATION 

ELIGIBILITY DECISION DOCUMENT 

FOR METHOMYL 

J. Leahy D230188 02/21/1997 OCCUPATIONAL AND RESIDENTIAL 

EXPOSURE ASSESSMENT 

AND RECOMMENDATIONS FOR THE 

REREGISTRATION 

ELIGIBILITY DECISION DOCUMENT 

FOR METHOMYL 

C. Eiden D303039 and D230187 02/11/1997 Methomyl Residue and Product 

Chemistry Chapters.