Common pesticide can make male frogs female, contributing to population decline

Berkeley, Calif.

-- A widely used pesticide, atrazine, has been found to affect the endocrine systems of frogs, essentially turning them into female frogs, according to a study by University of California-Berkeley biologists.

Atrazine is a endocrine disruptor, interfering with hormones such as estrogen and testosterone. It chemically castrates male frogs, eliminating the testosterone in their systems. These altered frogs are able to mate with unaffected male frogs, but all of the offspring are males. One of the authors of the study, Tyrone B. Hayes, says a chemical causing this type of sex reversal and skewing sex ratios can be more harmful to a species in the long-run than a chemical that outright kills a population because it slowly degrades the population, producing fewer and fewer females.

Atrazine affected one in 10 male frogs in the experiments. The researchers used the African clawed frog (Xenopus laevis) as their laboratory test subject. These findings likely translate to wild frog populations because field studies have shown that atrazine may be one of the causes of worldwide amphibian decline, says Hayes. The frogs are exposed to the chemical from run-off into ground and surface water. Each year, about 80 million pounds of atrazine are applied to control weeds and increase the crop yield of corn and sorghum.

The Environmental Protection Agency is now reviewing the regulations on using atrazine as a pesticide. The European Union has already banned the use of atrazine, and several U.S. states are looking to do the same.