Last week, University of California-Berkeley Professor Tyrone Hayes published a new study on the effects of the herbicide Atrazine,  saying the chemical changes some male frogs into females and chemically castrates others. But the maker of the drug fired back, calling Hayes’ science unsound. The company said Hayes is an activist, not a scientist.

The article was published in the online edition of the Proceedings of the National Academy of Sciences on March 1, and will be published in the next edition of the print magazine. Hayes has published research in the past about Atrazine’s affects on amphibian larvae, and the March 1 issue of  The Chronicle reported on Hayes’ contention that Atrazine may be carcinogenic. His newest study links Atrazine to the global decline of frogs.

But Syngenta, the Swiss company that manufactures the drug, said Hayes’ new study was moot.

“The issue of whether or not Atrazine affects frogs has already been determined,” said Steven Goldsmith, a spokesman for Syngenta. “Atrazine does not cause any problems with frog development.”

According to Goldsmith, the Environmental Protection Agency, which he called the “independent arbitrator of these issues,” reviewed Hayes’ work and called his data insufficient and methods flawed. Goldsmith and an attorney for Syngenta pointed repeatedly to the EPA’s assessment of Atrazine to disprove Hayes’ research.

A 2003 decision by the agency found Atrazine was “not likely” to cause cancer in humans. But the report is not as definitively pro-Atrazine as Syngenta contends.

“There is sufficient evidence to formulate a hypothesis that Atrazine exposure may impact gonadal development in amphibians, but there are currently insufficient data to confirm or refute the hypothesis,” the EPA’s decision reads.

The EPA’s findings are filled mostly with wait-and-see statements. The agency deemed the herbicide safe because there was not sufficient evidence to condemn it, but the 16-page document is filled with statements of need for more studies.

“The 2003 decision by the EPA was made in part by a guy named Kloas Vernor,” Hayes said. “His decision was ‘more research needs to be done.’ Within a day of that decision Kloas Vernor was on the Syngenta payroll … now Syngenta is publishing the guy that was supposed to be regulating them.”

According to Goldsmith, the matter is closed.

“The EPA believes there is no reason to investigate this any further,” he said.

But in late 2009, the agency opened a new review of Atrazine. The agency could not be reached for comment.

“One of [EPA] Administrator [Lisa] Jackson’s top priorities is to improve the way EPA manages and assesses the risk of chemicals including pesticides, and as part of that effort, we are taking a hard look at the decision made by the previous administration on Atrazine,” said Steve Owens, assistant administrator for the EPA’s Office of Prevention, in a press release in October.

Goldsmith said he thinks the agency is wasting time and money starting a new review of the herbicide.

“The EPA has spent a lot of time and a lot of years reviewing the science,” Goldsmith said. “We think that three years later, after the EPA already made a decision, for the new political appointees to come in and say, ‘No we need to do this again,’ is really a waste of time and taxpayers’ money.”

According to Hayes’ new study, Atrazine is one of the most commonly applied herbicides in the world, and it is the most commonly detected herbicide contaminant of ground, surface and drinking water. The study, authored by Hayes and ten other scientists, found that Atrazine-exposed male frogs were both chemically castrated and completely feminized as adults, and ten percent of the exposed males developed into functional females that copulated with unexposed adult males. The study concludes that Atrazine likely played a role in global amphibian decline.

But Goldsmith said Hayes’ study brings nothing new to the table because it “has so many issues” with methodology and is based on “bad data.”.

“That’s a complete fabrication,” Hayes said in response.

Hayes said Syngenta was fabricating claims about his research because they had no answer for the serious issues his studies raise

Yale University Professor David Skelly studied Hayes’ work and conducted his own research on frogs. He found the same sexual mutations, but his study linked the mutations to pollution and wastewater and not necessarily Atrazine.

Hayes said he stands by his work, and had a sharp response to Syngenta’s claim that he is biased.

“As far as me being an activist, as a scientist I have information, I have access to information and I have the capacity to interpret and explain that information, that’s my professional responsibility,” Hayes said. “As a person and as a professional, I have a social responsibility to provide my expertise especially in an area where I see that there’s a risk to our future.”

Hayes’ research was originally funded by Syngenta, until he broke with the company over issues regarding his negative findings about Atrazine.

“If I had stayed with Syngenta … I would have been set for life, all I had to do was lose my integrity, and that’s not something I was willing to do,” Hayes said.

Goldsmith said the issue was not whether or not Atrazine was harmful, but if we could survive without it.

“Forty percent of the world’s food would not exist without crop protection chemicals like Atrazine,” Goldsmith said. “There are lots of people in the world who don’t like chemicals of any kind …   but how are we going to feed a world that has nine billion people in it by 2050 if we can’t use  technology to grow that food?”