The herbicide atrazine, one of the world's most widely used pesticides, screws up the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females, according to a new study by UC Berkeley's Tyrone Hayes. By Robert Sanders. Hayes, professor of integrative biology. The 10 percent or more that turn from males into females β something not known to occur under natural conditions in amphibians β can successfully mate with male frogs but, because these females are genetically male, all their offspring are male.
Though the experiments were performed on a common laboratory frog, the African clawed frog Xenopus laevis , field studies indicate that atrazine, a potent endocrine disruptor, similarly affects frogs in the wild, and could possibly be one of the causes of amphibian declines around the globe, Hayes said. Some 80 million pounds of the herbicide atrazine are applied annually in the United States on corn and sorghum to control weeds and increase crop yield, but such widespread use also makes atrazine the most common pesticide contaminant of ground and surface water, according to various studies.
More and more research, however, is showing that atrazine interferes with endocrine hormones, such as estrogen and testosterone β in fish, amphibians, birds, reptiles, laboratory rodents and even human cell lines at levels of parts per billion.
Recent studies also found a possible link between human birth defects and low birth weight and atrazine exposure in the womb. As a result of these studies, the Environmental Protection Agency EPA is reviewing its regulations on use of the pesticide. Several states are considering banning atrazine, and six class action lawsuits have been filed seeking to eliminate its use.
The European Union already bars the use of atrazine. Working with the African clawed frog, Hayes and his colleagues showed in that tadpoles raised in atrazine-contaminated water become hermaphrodites β they develop both female ovaries and male testes gonads. This occurred at atrazine levels as low as 0. Subsequent studies showed that native leopard frogs Rana pipiens collected from atrazine-contaminated streams in the Midwest, including from areas up to 1, miles from where atrazine is applied, often had eggs in their testes.
