WHITE PAPER Information in Suppport of Chlorothalonil Use in the Western United States relative to Endangered Salmonid Species. (revised) AUTHOR

Chlorothalonil is a broad spectrum protectant fungicide with a unique multi-site mode of action, widely used in agriculture (Bravo) and on turf (Daconil). Chlorothalonil because of its mode of action is a critical tool in fungicide resistance management. This document contains Syngenta Crop Protection, Inc.'s assessment concerning risk to federally listed threatened and endangered salmonids and their critical habitat in the Western United States from the use of chlorothalonil. Chlorothalonil is classified as very highly toxic to fish based on laboratory studies and a screening level assessment, such as that performed by EPA in the Chlorothalonil Reregistration Eligibility Decision (US EPA 1999), indicates concerns for acute risk to fish. However, chlorothalonil rapidly dissipates in aquatic systems resulting in no potential for chronic exposure. Also higher tier effects data indicate that in the environment exposure and thus acute toxicity is substantially mitigated and any acute effects on fish are unlikely in aquatic ecosystems. In a screening level assessment, risk to organisms which may act as a food source could also raise concerns, however higher tier data indicate that chlorothalonil does not pose an adverse risk to these food organisms nor does it affect any other components of critical habitat. This absence of effects are explained by the fact chlorothalonil rapidly dissipates in aquatic environments. Of the 26 listed threatened and endangered Evolutionary Significant Units (ESUs) of Pacific salmon and steelhead, assessments based on ESU habitat and chlorothalonil use concluded that chlorothalonil will have no effect.