"A new study has found that male frogs exposed to the herbicide atrazine -- one of the most common man-made chemicals found in U.S. waters -- can make a startling developmental U-turn, becoming so completely female that they can mate and lay viable eggs.

The study, published online Monday in the Proceedings of the National Academy of Sciences, seems likely to add to the attention focused on a weedkiller that is widely used on cornfields. The Environmental Protection Agency, which re-approved the use of atrazine in 2006, has already begun a new evaluation of its potential health effects.

Its manufacturer, Swiss agri-business giant Syngenta, says research has proven that the chemical is safe for animals and for people, who could be exposed to trace amounts in drinking water.

But in recent years, a series of scientific studies have seemed to show atrazine interfering with the hormone systems that guide development in fish, birds, rats and frogs."

David A. Fahrenthold reports for the Washington Post March 2, 2010. [2]