An herbicide that contaminates the tap water consumed by millions of Americans has been found to produce gender-bending effects in male frogs, "chemically castrating" some and turning others into females, a study shows. Frogs in the experiment were exposed to amounts of the weedkiller atrazine that are comparable to the levels allowed in drinking water by the Environmental Protection Agency, says lead researcher Tyrone Hayes of the University of California-Berkeley. The study was released Monday in the Proceedings of the National Academy of Sciences. In Hayes' earlier studies, atrazine caused male frogs to begin growing eggs in their testes. In...