By Janet Raloff
New studies of male frogs in the wild link trace exposures to common weed killers with partial sex reversal. The findings suggest one possible factor behind declining amphibian populations worldwide.
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Atrazine, the nation’s most widely used herbicide, is nearly ubiquitous. Some U.S. rainwater carries up to 0.4 part per billion of the chemical. Earlier this year, scientists at the University of California, Berkeley reported bending the gender of male frogs by incubating tadpoles in as little as 0.1 ppb atrazine (SN: 4/20/02, p. 243: Feminized Frogs: Herbicide disrupts sexual growth). Affected animals grew extra testes and sometimes, ovaries.