Tyrone Hayes catching frogs for study.

Tyrone Hayes is on a frog hunt. Around the world, at least 20 frog species have become extinct and many surviving populations are suffering. Clues to some of these disappearances may be appearing in the American heartland where northern leopard frog populations are declining dramatically. Trudging through marshes and ponds, Hayes and his students have been collecting frogs and bringing them back to the lab. There, they have revealed bizarre anomalies inside the frog's reproductive organs. Some of the male frogs have eggs growing inside their testes instead of sperm – they are hermaphrodites.

At the same time, US farms are producing about one trillion ears of corn every year often using manmade chemicals like Atrazine, which can reach the world's waterways by wind and rain. Hayes's research suggests that this chemical, Atrazine, can cause the male hormone testosterone to turn into the female hormone estrogen. This extra estrogen can cause males to not only grow eggs but even develop ovaries. A frightening finding is how little Atrazine is needed to induce this dramatic effect. According to Hayes, "Point one micrograms per liter. That's the weight of one-one-thousandth of a grain of salt that causes this hermaphroditism." While tiny doses caused deformities, larger doses appear less harmful. Big amounts may trigger the body's defenses, while small doses can sneak in under the radar. Hayes's results raise doubts about chemical safety laws and regulations that often assume bigger doses are always worse.

Tyrone Hayes analyzing his findings in the lab.

Hayes's work is part of a growing body of research identifying how some manmade chemicals can significantly affect reproductive development of organisms. When these chemicals, known as endocrine disruptors, are absorbed into the body they either mimic or block hormones and disrupt the body's normal functions. This disruption can happen through altering normal hormone levels, halting or stimulating the production of hormones or changing the way hormones travel through the body, thus affecting the functions that these hormones control.

References
»	For more information on Hayes' frog research and the endocrine disruptor Atrazine see this San Francisco Chronicle article by Carl Hall (4 Nov 2002) entitled "From Boyhood Curiosity to Scientific Discovery Biologist Tyrone Hayes Links Pesticides to Amphibian Deformities."
»	Check out more in-depth information on the methodology used by Hayes in his study of frogs and Atrazine.

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