Chlorothalonil

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.^[1] Including non-agricultural uses, the EPA estimates that on average almost 15 million lbs were used in annually from 1990-1996.^[2]

Additional recommended knowledge

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Uses

In the US, chlorothalonil is used predominantly on peanuts, potatoes, tomatoes. It also used on golf courses and lawns and as an additive in some paints.^[2]

Health effects

According to the United States Environmental Protection Agency, chlorothalonil is a Category I "severe" eye irritant. It is not considered to be acutely toxic by ingestion (its oral LD₅₀ is greater than 10,000 mg/kg), but is toxic when inhaled. In animal tests, long term chlorothalonil exposure resulted in kidney damage. Chlorothalonil is a class B2 "probable carcinogen", based on observations of cancers and tumors of the kidneys and forestomach in laborotory animals fed diets containing chlorothalonil.^[2]

Chlorothalonil is highly toxic to fish and aquatic invertabrates, but not toxic to birds.^[3]

Chemistry

Chlorothalonil can by produced by the direct chlorination of isophthalonitrile or by treating tetrachloroisophthaloyl amide with phosphoryl chloride. It breaks down under basic conditions but is stable in neutral and acidic media.^[3] Technical chlorothalonil contains traces of dioxins and hexachlorobenzene,^[2] a persistent organic pollutant banned under the Stockholm Convention.

References