TAMPA — With the EPA taking a hard look at the popular weed killer atrazine, two University of South Florida biologists say there's evidence it harms fish and frogs.
In Florida, atrazine is widely used on lawns, golf courses and sugarcane fields.
But the USF researchers say study after scientific study shows that atrazine alters or interferes with the development, behavior and the immune, hormone and reproductive systems of aquatic animals.
"There are clear, consistent effects of atrazine on freshwater fish and amphibians … and many of those effects are on vital systems," said Jason Rohr, an assistant professor in USF's department of integrative biology.
Rohr and postdoctoral fellow Krista A. McCoy looked at more than 100 scientific studies of the controversial herbicide. They published their conclusions in the journal Environmental Health Perspectives.
In response, atrazine's manufacturer defends it as a "mainstay of American agriculture" with "wide margins of safety."
"Atrazine is one of the most closely examined herbicides in the marketplace," Sherry Duvall Ford, a spokeswoman for Syngenta Crop Protection, said in an e-mail to the St. Petersburg Times.
Studies worldwide have concluded that atrazine has been used safely for 50 years, she said. She noted that in 2006, the U.S. Environmental Protection Agency reviewed atrazine and concluded that it poses no harm to infants, children or adults.
More recently, the EPA has said it might revisit the issue.
"The Obama EPA will take a hard look at atrazine and other substances," according to a statement from Steve Owens, the agency's assistant administrator for the Office of Prevention, Pesticides and Toxic Substances.
"New scientific developments" will help "determine whether a change in our regulatory position is appropriate," Owens said.
In August, the EPA said it is doing an "intensive" program to look for atrazine residue in the drinking water of about 150 communities, mostly in the Midwest, where it is used to help grow corn.
Syngenta says federal standards for atrazine in drinking water are so conservative that a 150-pound adult could safely drink 21,000 gallons of water containing 3 parts per billion of atrazine — the federal limit — every day for 70 years.
Syngenta also said it has commissioned scientific studies of atrazine and frogs. Those experiments show no effect on the normal development of frogs, the company says.
But it was Syngenta's role in some of the science surrounding atrazine that prompted Rohr to review the literature himself. He said Syngenta and its corporate predecessors had commissioned four previous reviews of scientific studies on atrazine.
His analysis found patterns of effects that those earlier reviews did not, he said.
"I think this offers perhaps a more objective synthesis of the literature that might be useful to the regulatory process as well as to direct future scientific research," he said.
Rohr and McCoy offer no conclusions about whether the EPA should enact new restrictions on the use of atrazine. Rather, they say the effects on wildlife should be weighed against its benefits.
Europe banned atrazine in 2003, but it remains the second most commonly used pesticide in the United States.
While atrazine typically does not kill amphibians and freshwater fish, the USF report said it did:
• Reduce the size of amphibians at or near metamorphosis in 19 of 19 studies.
• Make amphibians and fish more active in 12 of 14 studies but reduced behaviors used to evade predators in six of seven studies.
• Alter at least one aspect of male frogs' reproductive development in eight of 10 studies.
• Reduce the functioning of animals' immune systems and often put them at risk of infection.
Atrazine's effect on frogs has been a hot topic since 2002.
That's when scientists at University of California at Berkeley reported in the journal Nature that male frogs in water polluted with atrazine were turning into hermaphrodites.
Researchers said then that the finding might help explain why scores of amphibian species had gone extinct or become endangered in recent decades.
While Rohr cautioned against extrapolating his study's findings to humans, he said the study of creatures like frogs is important.
Changes in an ecosystem's biodiversity can reduce its ability to produce clean water and food and to buffer people from disease, he said.
Second, he said, "amphibians are considered good indicators of threats to other organisms, canaries in the coal mine."
Richard Danielson can be reached at Danielson@sptimes.com or (813) 226-3403
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