Simazine Analysis of Risks to Endangered and Threatened Salmon and Steelhead July 25 , 2003

Simazine is a selective herbicide used on various crops and non-crop sites. It is slightly to moderately toxic to fish and aquatic invertebrates, and it is highly toxic to aquatic vascular plants. Modeling of potential simazine estimated environmental concentrations (EECs) indicates that with the highest application rates, the most vulnerable soils, and a very high runoff potential, the upper tenth percentile EECs do not exceed any levels of concern. Federally listed Pacific salmon and steelhead occur in areas with lower application rates, typically less vulnerable soils, and less runoff potential, thus providing even a greater margin of safety than would result from the modeled EECs. I conclude that there will be no effects on any ESU of listed Pacific salmon or steelhead.