EPA Proposes Interim Registration Review Decision for Malathion

Background

Malathion, first registered in the United States in 1956, is used to control a variety of insect pests on agricultural crops, residential areas, and public health mosquito control programs. The EPA has now updated its assessment to incorporate the latest scientific methodologies and public feedback.

Key Findings from the Review

Human Health Risks

The updated human health risk assessment used the latest scientific approaches, including a human lifestage physiologically based pharmacokinetic-pharmacodynamic (PBPK-PD) model. This model simulates the absorption, distribution, metabolism, and excretion of malathion and its metabolite, malaoxon, which is the active moiety inhibiting the enzyme acetylcholinesterase (AChE). The assessment concluded that:

• Dietary Risks: No risk concerns were identified for acute and steady-state dietary exposures from food and drinking water.
• Residential Handler Risks: No risks of concern were found for adult residential handlers of malathion.
• Aggregate Risks: Combined exposures from food, water, and residential settings were below the level of concern.
• Cumulative Risks: Ongoing assessments will further evaluate the cumulative risks of malathion and other organophosphates.

Ecological Risks

The ecological risk assessment highlighted potential risks to various taxa:

• Terrestrial Risks: Risks of concern were identified for mammals, birds, reptiles, terrestrial-phase amphibians, and invertebrates. However, new mitigation measures, including updated spray drift management and pollinator protection, aim to reduce these risks.
• Aquatic Risks: Acute risks were identified for freshwater and estuarine/marine fish, but chronic risks were not a concern. Aquatic invertebrates and plants may also be at risk, but mitigations are expected to alleviate these concerns.

Proposed Mitigation Measures

To address the identified risks, the EPA proposes several risk mitigation measures, including:

• Personal Protective Equipment: Enhanced requirements for handlers to reduce exposure.
• Spray Drift Management: Improved practices to minimize off-target movement.
• Application Restrictions: Updated guidelines on application rates and timing to protect sensitive areas.
• Label Changes: Clarifications and updates to product labels to ensure proper usage and safety measures.

Next Steps

The EPA invites public comments on the Proposed Interim Decision for malathion. Stakeholders and interested parties can submit their feedback during the 60-day public comment period. The Agency will review the comments and incorporate necessary changes before finalizing the registration review decision.

The full document, including detailed risk assessments and proposed mitigation measures, is available on the EPA's regulations.gov website under Docket Number EPA-HQ-OPP-2009-0317.