Proposed Re-evaluation Decision PRVD2016-02, Methomyl

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Pest Management Regulatory Agency
15 January 2016
ISSN: 1925-0967 (PDF version)
Catalogue number: H113-27/2016-2E-PDF (PDF version)

This page is a summary of the consultation document. If you would like to comment, please request the full consultation document.

To obtain a full copy of Proposed Re-evaluation Decision PRVD2016-02, Methomyl please contact our publications office.

Should you require further information please contact the Pest Management Information Service.

Summary

Table of Contents

Proposed Re-evaluation Decision for Methomyl

Health Canada's Pest Management Regulatory Agency (PMRA) has now completed the risk and value assessments for methomyl. This revised assessment is based on consideration of the comments and submitted data in response to REV2009-02, changes to the use pattern outlined in REV2010-08 and any regulatory changes in other countries. Under the authority of the Pest Control Products Act, the PMRA is proposing continued registration of certain uses of methomyl in Canada.An evaluation of available scientific information found that:

  • Non-food uses of methomyl continue to have value and do not present an unacceptable risk to human health or the environment, when used according to revised label directions. Non-food uses include application to balsam fir and spruce in Christmas tree plantations, farm woodlots and rights-of-way, and as granular baits in barns, poultry houses, feedlots and kennels.
  • Based on the human health risk assessment,food and feed uses of methomyl, including use on tobacco,are being proposed for cancellation and all established maximum residue limits (MRLs) for methomyl are proposed for revocation.

This proposal affects all end-use products containing methomyl registered in Canada. Once the final re-evaluation decision is made, the registrants will be instructed on how to address any new requirements.

Proposed Re-evaluation Decision PRVD2016-02, Methomyl is a consultation document that summarizes the science evaluation for methomyl and presents the reasons for the proposed re-evaluation decision. It also proposes additional risk-reduction measures to further protect human health and the environment.

The information in Proposed Re-evaluation Decision PRVD2016-02, Methomyl is presented in two parts. The Overview describes the regulatory process and key points of the evaluation, while the Science Evaluation provides detailed technical information on the assessment of methomyl.

The PMRA will accept written comments on this proposal up to 60 days from the date of publication of PRVD2016-02, Methomyl. Please forward all comments to Publications.

What Does Health Canada Consider When Making a Re-evaluation Decision?

The key objective of the Pest Control Products Act is to prevent unacceptable risks to people and the environment from the use of pest control products. Health or environmental risk is considered acceptable if there is reasonable certainty that no harm to human health, future generations or the environment will result from use of or exposure to the product under its conditions or proposed conditions of registration. The Act also requires that products have value when used according to the label directions. Conditions of registration may include special precautionary measures on the product label to further reduce risk.

To reach its decisions, the PMRA applies hazard and risk assessment methods as well as policies that are rigorous and modern. These methods consider the unique characteristics of sensitive subpopulations in both humans (for example, children) and organisms in the environment (for example, those most sensitive to environmental contaminants). These methods and policies also consider the nature of the effects observed and the uncertainties present when predicting the impact of pesticides. For more information on how the PMRA regulates pesticides, the assessment process and risk-reduction programs, please visit the Pesticides and Pest Management section of Health Canada's website.

For more details on the information presented in this overview, please refer to the Science Evaluation of Proposed Re-evaluation Decision PRVD2016-02, Methomyl.

What is Methomyl?

Methomyl is a carbamate insecticide, used to control a broad range of insect pests on a wide variety of sites including forests and woodlots, ornamental spruce and fir trees, terrestrial feed and food crops, industrial oilseed and fibre crops, and structures (in other words, farm buildings). It is applied using conventional ground and aerial application equipment by farmers, farm workers and professional applicators.

Health Considerations

Can Approved Uses of Methomyl Affect Human Health?

Non-food uses of methomyl are unlikely to affect your health when used according to the revised label directions. Based on the human health risk assessment, all food and feed uses of methomyl, including use on tobacco, are being proposed for cancellation.

Potential exposure to methomyl may occur through the diet (in other words, food and drinking water), when applying the product or by entering treated sites. When assessing health risks, two key factors are considered:

  • the levels at which no health effects occur in animal testing and
  • the levels to which people may be exposed.

The dose levels used to assess risks are established to protect the most sensitive human population (for example, children and nursing mothers). Only uses for which the exposure is well below levels that cause no effects in animal testing are considered acceptable for registration.

In laboratory animals, the technical grade active ingredient methomyl was of high acute toxicity by the oral route. It was of low acute toxicity dermally and of moderate toxicity through inhalation exposure. Methomyl was non-irritating to eyes and skin, but highly toxic via the eyes. Methomyl did not cause an allergic skin reaction.

Short- and long-term (lifetime) animal toxicity tests were assessed for the potential of methomyl to cause neurotoxicity, immunotoxicity, chronic toxicity, cancer, reproductive and developmental toxicity, and various other effects. The most sensitive endpoint used for risk assessment was the effect on the nervous system (decreased cholinesterase activity). When methomyl was given to young animals, effects on cholinesterase activity indicated that the young were more sensitive to methomyl than the adult animal. The risk assessment takes this sensitivity into account in determining the allowable level of human exposure to methomyl.

Residues in Water and Food

Based on the human health risk assessment, all food and feed uses of methomyl, including use on tobacco, are being proposed for cancellation.

Reference doses define levels to which an individual can be exposed over a single day (acute) or lifetime (chronic) and expect no adverse health effects. Generally, dietary exposure from food and drinking water is acceptable if it is less than 100% of the acute reference dose or chronic reference dose (acceptable daily intake). An acceptable daily intake (ADI) is an estimate of the level of daily exposure to a pesticide residue that, over a lifetime, is believed to have no significant harmful effects.

Human exposure to methomyl was calculated based on residues in treated crops and drinking water. Exposure was determined for the general population, as well as various subpopulations including children. Residue estimates in food were mostly based on monitoring data from the United States Department of Agriculture (USDA) Pesticide Data Program as well as the Canadian Food Inspection Agency (CFIA) National Chemical Residue Monitoring Program. Residues in drinking water were based on modelling data.

Acute risk concerns were identified from exposure to food only as well as exposure from drinking water only. The acute exposure from food was 79% of the acute reference dose for the general population and ranged from 47% to 211% for the various subpopulations. Of note, acute exposures were 174, 211 and 152% for infants (less than 1 years of age), children aged 1 to 2 years, and children aged 3 to 5 years, respectively. Acute exposure from drinking water exceeded 100% of the acute reference dose for the general population and all subpopulations. Chronic exposure from food only was less than 8% of the ADI for the general population and all subpopulations. Chronic exposure from drinking water exceeded 100% of the ADI for one population subgroup: infants at 158% of the ADI.

Aggregate risk due to exposure from both food and drinking water combined was not assessed, as potential concerns were identified from the individual pathways of exposure.

The Food and Drugs Act prohibits the sale of adulterated food; that is, food containing a pesticide residue that exceeds the established maximum residue limit (MRL). Pesticide MRLs are established for Food and Drugs Act purposes through the evaluation of scientific data under the Pest Control Products Act. Each MRL value defines the maximum concentration in parts per million (ppm) of a pesticide allowed in/on certain foods. Food containing a pesticide residue that does not exceed the established MRL does not pose an unacceptable health risk.

Canadian MRLs for methomyl are currently established for apple, blueberry, cabbage, celery, citrus fruit, grape, lettuce, strawberry and sweet corn kernel plus cob with husks removed. Residues in all other agricultural commodities, including those approved for treatment in Canada but without a specific MRL, are regulated under subsection B.15.002(1) of the Food and Drugs Regulations, which requires that residues not exceed 0.1 ppm. Additional details regarding MRLs can be found in the Science Evaluation of Proposed Re-evaluation Decision PRVD2016-02, Methomyl. Since all food uses of methomyl are being proposed for cancellation, established MRLs for methomyl are being proposed for revocation. This will ensure that residues in food do not pose any health risk concerns.

Risks in Residential and Other Non-Occupational Environment

Residential risks are not of concern.

As methomyl is currently registered for use on apple trees, potential residential exposure may occur following application by commercial applicators to apple trees in residential areas. No residential risks of concern were identified for this use. Since all food and feed uses are proposed for cancellation, this scenario is not expected to occur.

Potential exposure may also occur from "Pick Your Own" facilities or commercial farming operations that allow public access for harvesting in large-scale fields or orchards treated with commercially labelled methomyl products. However, since all food uses are proposed for cancellation, exposure in Pick Your Own facilities is not expected to occur and was not included in this assessment.

Occupational Risks

Occupational risks to handlers are not of concern provided additional risk reduction measures are observed.

Occupational risk assessments for handlers consider exposure to workers who mix, load and apply methomyl. For the uses proposed for continued registration (in other words, application to balsam fir and spruce in Christmas tree plantations, farm woodlots and rights-of-way, and as granular baits in barns, poultry houses, feedlots and kennels), handler risks are not of concern with risk mitigation measures. These measures include personal protective equipment and limits on amount of product handled per day. These measures are needed to minimize potential exposure and protect workers' health.

Postapplication risks are not of concern provided additional risk reduction measures are observed.

Postapplication occupational risk assessments consider exposures to workers entering treated sites. For the uses proposed for continued registration, postapplication risks are not of concern. A restricted-entry interval of 12 hours is required for postapplication activities that may occur following application to balsam fir and spruce in Christmas tree plantations, farm woodlots and rights-of-way.

Environmental Considerations

What Happens When Methomyl Is Introduced into the Environment?

When used according to the label directions, methomyl is not expected to pose an unacceptable risk to the environment.

Methomyl can enter non-target terrestrial and aquatic habitats through spray drift and can enter aquatic habitats through run-off and leaching. It is slightly persistent in some soils, but is not expected to accumulate over time. Methomyl is soluble in water and can move through the soil profile, and potentially reach ground water. In aquatic environments, methomyl is non-persistent and does not accumulate. It is not likely to accumulate in plant and animal tissues.

Under controlled laboratory conditions, methomyl can be toxic to some non-target species such as bees, beneficial insects, birds, wild mammals, aquatic invertebrates, amphibians and fish.

If methomyl is used at labelled application rates without any risk reduction measures, it may cause adverse effects in the organisms listed above. Therefore, mitigation measures are required in order to reduce potential exposure of non-target organisms and reduce environmental risks.

When methomyl is used in accordance with the label and the mitigation measures have been applied, the reduced environmental exposure is deemed adequate and the risk is considered to be acceptable.

Value Considerations

What is the Value of Methomyl?

Methomyl is absorbed by the host plant in addition to providing contact action.

Methomyl is effective in two ways: (a) as a contact insecticide, killing target insects upon direct contact, and (b) as an insecticide that works by killing target insects upon ingestion of treated plants. Methomyl is absorbed and transported throughout the plant, imparting protection to the entire plant. It is effective against insects with piercing-sucking mouthparts, such as aphids and thrips, since it moves within the vascular tissues where aphids feed and into cells where thrips feed.

Methomyl is effective for the control of pests such as:

  • chewing insects once they enter the host plants: corn earworm and European corn borer larvae tunnel into the midrib of the leaf and migrate into the stalk of the plant, or husk of the ear
  • insects, such as thrips, beet armyworm and slugs that hide within the developing plant leaves while feeding and are protected from direct contact with insecticidal sprays

Methomyl has a unique application method for the control of slugs on Brussels sprouts

There are few registered alternatives to methomyl for control of slugs on this crop. Methomyl is registered to control slugs on Brussels sprouts as a spray. In contrast, the alternative active ingredients to methomyl are formulated for use as baits, which may not be as effective when alternate food sources are available, such as when crops are mature.

Methomyl is of value for pest management in agriculture in Canada.

There are no viable alternatives to methomyl for the control of beet webworm and clover cutworm on canola in Eastern Canada. Resistance management is a concern for these pests in Western Canada since deltamethrin (MoA group 3) is the only registered alternative active ingredient to methomyl and is registered for this use in Western Canada only.

There are few viable alternatives to methomyl for the control of alfalfa looper on peas and canola; bertha armyworm on flax; and for the control of thrips on barley, oats and wheat.

Methomyl (MoA group 1A) is required for rotation with insecticides with a different mode of action to delay the development of resistance. Examples are as follows:

  • Acetamiprid (MoA group 4) is the only viable alternative active ingredient to methomyl for the control of aphids on sweet corn
  • Chlorantraniliprole (MoA group 28) is the only active ingredient with local systemic available for rotation with methomyl for the control of corn earworm on sweet corn

Proposed Measures to Minimize Risk

Registered pesticide product labels include specific instructions for use. Directions include risk-reduction measures to protect human and environmental health. These directions are required by law to be followed.

Risk mitigation measures affecting the use pattern of methomyl were implemented in REV2010-08. These included (a) removal of the use of methomyl on strawberries and in residential areas and parks, as these uses were no longer supported by the registrant, (b) clarification of the maximum number of applications per season, and (c) inclusion of restricted-entry intervals.

Based on the health risk assessment, the PMRA proposes to cancel all food and feed uses of methomyl. Consequently, all MRLs are proposed for revocation. Continued registration with additional risk mitigation measures is proposed for non-food uses: application to balsam fir and spruce in Christmas tree plantations, farm woodlots and rights-of-way, and granular baits in barns, poultry houses, feedlots and kennels.

Risk reduction measures are being proposed to address potential risks identified in this assessment. These measures, in addition to those already identified on existing methomyl product labels, are designed to further protect human health and the environment. The following additional key risk-reduction measures are being proposed for non-food uses of methomyl.

Human Health

To protect mixer/loader/applicators:

  • Ensure they wear additional personal protective equipment.
  • Limit the amount of product used per day when using mechanically pressurized handguns.

To protect workers entering treated sites:

  • A Restricted-entry interval of 12 hours for balsam fir and spruce in Christmas tree plantations, farm woodlots and rights-of-way.

To protect the general public and bystanders:

  • A statement clarifying that bait products are limited to agricultural use (in other words, not for use in residential areas).
  • A statement to promote best management practices to minimize human exposure from spray drift or spray residues resulting from drift.

To reduce the potential for accidental ingestion of granular bait products:

  • A statement clarifying that bait products should not be used where children or pets are likely to be present.

Environment

  • Advisory statements to inform users that methomyl is toxic to non-target organisms including bees, beneficial insects, birds, mammals, aquatic invertebrates, fish, frogs and other amphibians.
  • Advisory statements to minimize spray drift to areas where bees might be present.
  • Advisory statements to inform users of conditions that may favour run-off and leaching.
  • Spray buffer zones to protect aquatic habitats from drift.
  • A statement advising that methomyl could potentially reach groundwater, particularly in areas where soils are permeable and/or the depth to the water table is shallow.

Next Steps

Before making a final re-evaluation decision on methomyl, the PMRA will consider any comments received from the public in response to Proposed Re-evaluation Decision PRVD2016-02, Methomyl. A science-based approach will be applied in making a final decision on methomyl. The PMRA will then publish a Re-evaluation Decision that will include the decision, the reasons for it, a summary of comments received on the proposed decision and the PMRA response to these comments.

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