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Methidathion Facts

EPA 738-F-01-007 March 2002

EPA has assessed the risks of methidathion and reached an Interim Reregistration Eligibility Decision (interim RED) for this organophosphate (OP) pesticide. Provided that risk mitigation measures are adopted, methidathion fits into its own "risk cup" -- its individual, aggregate risks are within acceptable levels. Methidathion is also eligible for reregistration, pending a full reassessment of the cumulative risk from all OPs.

Used on a variety of agricultural crops, predominantly alfalfa, citrus and cotton, methidathion residues in food and drinking water do not pose risk concerns. Methidathion has no residential uses. EPA considered the mitigation proposal submitted by the technical registrant, as well as comments and mitigation ideas from other interested parties, and has decided on a number of label amendments (restrictions) to mitigate risks of concern posed by the uses of methidathion. With the implementation of these mitigation measures, methidathion's worker and ecological risks also will be below levels of concern for reregistration.

EPA's next step under the Food Quality Protection Act (FQPA) is to consider available information on the basis of cumulative risk encompassing all of the OP pesticides, sharing a common mechanism of toxicity. The final tolerance reassessment decision for methidathion cannot be considered final until the cumulative risks for all of the OPs is considered. The Agency may need to pursue further risk management measures at that time.

EPA is reviewing the OP pesticides to determine whether they meet current health and safety standards. Older OPs need decisions about their eligibility for reregistration under FIFRA. OPs with residues in food, drinking water and other non-occupational exposures also must be reassessed to make sure they meet the new FQPA safety standard.

The methidathion interim decision was made through the OP pilot public participation process, which increases transparency and maximizes stakeholder involvement in EPA's development of risk assessments and risk management decisions. EPA has worked extensively with affected parties to reach the decisions presented in this interim RED document, which concludes the OP pilot process for methidathion.


Health Effects


Based on the data currently available, residues of only methidathion in food do not pose risk concerns. Dietary exposures from eating food crops treated with methidathion are well below the level of concern for the entire U.S. population, including infants and children. Similarly, drinking water is not a significant source of exposure.

Risk Mitigation

In order to support a reregistration eligibility decision for methidathion, the following risk mitigation measures are necessary:

To mitigate risks to agricultural workers:
To mitigate ecological risks:

The OP Pilot Public Participation Process

The organophosphates are a group of related pesticides that affect the functioning of the nervous system. They are among EPA's highest priority for review under the Food Quality Protection Act.

EPA is encouraging the public to participate in the review of the OP pesticides. Through a six-phased pilot public participation process, the Agency is releasing for review and comment its preliminary and revised scientific risk assessments for individual OPs. (Please contact the OP Docket, telephone 703-305-5805, or see EPA's web site, Pesticide Reregistration Status.)

EPA is exchanging information with stakeholders and the public about the OPs, their uses, and risks through Technical Briefings, stakeholder meetings, and other fora. USDA is coordinating input from growers and other OP pesticide users.

Based on current information from interested stakeholders and the public, EPA is making interim risk management decisions for individual OP pesticides, and will make final decisions through a cumulative OP assessment.

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