Common Weedkiller Causes Feminization of Frogs, Study Says
Male frogs exposed to atrazine, an herbicide commonly found in U.S. waters, can become completely feminized by the time they are adults,
a new study says. The hormonal reversal can be so complete, in fact,
that these frogs can mate with other male frogs and lay eggs, according
to the report published in the Proceedings of the National Academy of Sciences.
The weed killer, produced by Swiss-based Sygenta, was re-approved for
use by the U.S. Environmental Protection Agency in 2006. But recent 
studies show the chemical may interfere with the hormone systems of
fish, birds, rats, and frogs. The most recent research, conducted by
scientists at the University of California at Berkeley, examined the
effects on 40 African clawed frogs exposed to the chemical as tadpoles.
While all of the frogs carried male chromosomes initially, about 10
percent became “functionally female” as they developed, and were able to
produce viable eggs after mating, said Tyrone Hayes, the lead author.
The other 90 percent retained male characteristics, but often had lower
testosterone levels. “It’s a chemical… that causes hormone havoc,” Hayes
said.
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The African clawed frog
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