Atrazine is perhaps the most commonly used herbicide across the world, but its effect on non-target organisms has been poorly investigated. In October 31 Nature, Tyrone Hayes and colleagues from University of California, Berkeley, USA, show that atrazine in agricultural run-off water can cause feminization of male frogs in the wild (Nature, 419: 895-896, October 31, 2002).

Hayes et al. investigated the effects of exposure to atrazine on wild leopard frogs (Rana pipiens) in eight states across America. They observed that 10-92% of males showed gonadal abnormalities such as retarded development and hermaphroditism. In addition, when they exposed R. pipiens larvae to different concentrations of atrazine (0, 0.1 and 25 parts per billion) in the laboratory they could reproduce the observed retarded gonadal development (gonadal dysgenesis).

"In the light of growing evidence that these [frog] populations are in decline, the contribution of atrazine to...

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