A study finds a weed killer commonly used on Iowa crops may cause deformities in frogs. The University of California at Berkeley study found frogs developed multiple sex organs after being exposed to low levels of the corn herbicide atrazine. Study author Tyrone Hayes says the atrazine may be one cause of the worldwide decline of amphibians. He says the data suggests the look further into the possibility that atrazine affects wild populations.Hayes says the levels of atrazine causing the abnormalities in the lab tests were comparable to levels found in the environment.The finding that this affect occurs at point-one part per billion is significant because there’s hardly anyplace that has less than point-one part per billion atrazine. It can even be found in rainwater in Iowa at 40-parts per billion.