US review of fenitrothion

The US Environmental Protection Agency (EPA) has carried out a review of the organophosphate insecticide fenitrothion, first registered in the US in 1975. Because of advances in scientific knowledge, US law requires that pesticides which were first registered years ago be re-registered to ensure that they meet today’s more stringent measures. Based on the available toxicity studies, the EPA has determined that fenitrothion presents a potential acute hazard. It is of moderate to high acute toxicity and is a cholinesterase inhibitor. It has been classified as non-carcinogenic to humans and dietary risk is low. Of greater concern is the risk posed to fenitrothion mixer, loaders and/or applicators using knapsack equipment to treat ornamentals. The EPA is deferring a regulatory decision for fenitrothion products using these methods until chemical-specific worker exposure studies, due within one year, are submitted.
    In the environment, fenitrothion is slightly persistent and relatively non-mobile in soil. It is highly toxic to birds on an acute basis and causes chronic effects (reduced egg production) in reproduction studies on bobwhite quail. It is highly toxic to aquatic invertebrates, and moderately to acutely toxic to esturine organisms. It is also highly toxic to bees.
    To reduce these risks, the registrant and EPA have developed mitigation measures.

• All fenitrothion products labelled for outdoor use must be classified as restricted use pesticides.

• Fenitrothion use on Christmas tree plantation, on shade trees other than those in nurseries, and basal bark (drench) are being voluntary withdrawn. These uses pose the greatest potential for exposure to non-target species.

• For the remaining ornamental uses, significant label revisions are proposed to reduce ecological risk.

• Due to concerns about the acute toxicity of fenitrothion, the EPA is establishing baseline personal protective equipment requirements for handlers of all end-use products.

• Concerns about post-application exposure of agricultural workers has convinced the EPA to increase the restricted entry interval (REI) from 24 to 48 hours. The REI is further increased to 72 hours specifically when fenitrothion products are used outdoors in areas where the average rainfall is less than 25 inches per year.

Fenitrothion, Reregistration Eligibility Document, US EPA, July, 1995, 9pp.