Chlorothalonil, also known as tetrachloroisophthalonitrile, is a broad spectrum, non-systemic fungicide. Chlorothalonil containing products are sold under the names Bravo, Echo, and Daconil. It was first registered for use in the US in 1966. In 1997, the most recent year for which data is available, it was the third most used fungicide in the US, behind only sulfur and copper, with some 12 million lbs used in agricultural alone that year. Including non-agricultural uses, the EPA estimates that on average almost 15 million lbs were used in annually from 1990-1996.
Chlorothalonil is highly toxic to fish and aquatic Invertebrates, but not toxic to birds.
The main breakdown product of chlorothalonil is SDS-3701 (4-hydroxy-2,5,6-trichloroisophthalonitrile). It has been shown to be 30 times more acutley toxic than chlorothalonil and more persistent in the environment. Laboratory experiments have shown that it can thin the eggshells of birds, but there is no evidence that this is happening in the environment.
The Fungicide Chlorothalonil Is Nonlinearly Associated with Corticosterone Levels, Immunity, and Mortality in Amphibians
Aug 01, 2011; BACKGROUND: Contaminants have been implicated in declines of amphibians, a taxon with vital systems similar to those of humans....