Common herbicide might affect frogs

One of the herbicides most widely used to fight a broad range of weeds in cornfields and on other cropland appears to affect the sexual development of frogs when it gets into the waterways in which they live, according to researchers at the University of Ottawa.

Their study found that when exposed to atrazine at levels comparable to those measured in the Canadian environment, fewer tadpoles reached the froglet stage, and the ratio of females to males increased.

"Atrazine is one of the top-selling herbicides used worldwide and was designed to inhibit weed growth in cornfields," the university said in a statement. "It is so widely used that it can be detected in many rivers, streams and in some water supplies. This has raised the alarm on the possibility of other serious detrimental environmental effects."

Atrazine has been banned in the European Union but not in the United States. In October, the Environmental Protection Agency announced that it would reevaluate the herbicide because of continuing concerns that its appearance in rivers, streams and other waterways was adversely affecting not only frogs but possibly also humans. Syngenta AG, which makes the herbicide, has defended its safety and said it has been valuable to farmers worldwide.

A previous study at the University of California at Berkeley also raised concerns about the effect of atrazine on the sexual development of frogs, in that case the African clawed frog.

-- Margaret Shapiro