Daily News Archive
From April 16, 2002

Atrazine Causes Mutations in Frogs

California researchers have discovered that male frogs exposed to even very low doses of atrazine, a common herbicide, can develop multiple sex organs, sometimes both male and female, according to an Associated Press article.

Atrazine is the most commonly used weed killer in North America and can be found in rainwater, snow runoff and ground water, according to Tyrone B. Hayes of the University of California at Berkeley. "There is virtually no atrazine-free environment," Hayes said.

Hayes' team found that frogs were affected by atrazine at doses as small as 0.1 parts per billion (ppb), though up to 3ppb is permitted in drinking water by the Environmental Protection Agency (EPA). As the amount of atrazine increased, up to 20 percent of frogs exposed during their early development produced multiple sex organs or had both male and female organs. Many also had small, feminized larynxes.

The research team concluded that the effect on the frogs results from atrazine causing cells to produce the enzyme aromatase, which is present in vertebrates and converts the male hormone testosterone to the female hormone estrogen. Effects on frogs in the study occurred at exposure levels more than 600 times lower than the dose that has been seen to induce aromatase production in human cells.

When asked if atrazine is also a threat to people at low levels, Hayes said he did not know, adding that, unlike frogs, "we're not in water all the time."

"I'm not saying its safe for humans. I'm not saying it's unsafe for humans. All I'm saying is it makes hermaphrodites of frogs, "he said.

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