Frogs Take on EPA and Atrazine — and Lose

The Environmental Protection Agency says that amphibians are safe around the herbicide atrazine. The company that makes atrazine paid for EPA’s studies. Independent researchers dispute the findings. The U.S. Environmental Protection Agency says that the herbicide atrazine doesn’t feminize amphibians and may continue to be used on crops, despite the findings of a number of independent studies showing that the chemical causes extensive and varied impacts on amphibians.

EPA is also reviewing numerous cancer studies on the possible effects of atrazine in humans. Atrazine is implicated — but not convicted — in several human cancers: prostate, lung, bladder, non-Hodgkin lymphoma and multiple myeloma. EPA says, however, “Atrazine is not likely to cause cancer in humans.”

Atrazine is an endocrine disruptor, which means that it has the potential to lower sperm count and fertility.

EPA reregistered atrazine in October 2006, but at the time it required additional studies about the herbicide’s impact on frogs. An EPA scientific advisory panel this week confirmed EPA’s conclusion that “atrazine does not adversely affect amphibian gonadal development based on a thorough review of 19 laboratory and field studies.”

Paonia, Colo.-based zoologist Theo Colborn, the world’s leading authority on endocrine disrupting chemicals, said of the decision, “I was so appalled, I could not believe it.”

Atrazine is manufactured by Swiss agribusiness giant Syngenta. Syngenta spokeswoman Sherry Ford counters, “Pesticides had never really been tested on frogs before … We are on the front edge of the science.”

Depending on how its counted, atrazine is either the most widely used or the second most widely used herbicide in the world. It is heavily applied in Colorado, especially by farmers in the northeast quadrant of the state, and along the Front Range. According to research by Michael Rupert of the U.S. Geological Survey, atrazine or its breakdown products were detected in water from from 61 percent of the wells in the South Platte River Basin. Nationally, atrazine is detected in about 38 percent of all sampled wells.

The controversy about atrazine arises from the potential linkage of two controversial issues — endocrine disrupting chemicals and the widespread disappearance of amphibians around the globe. Research beginning in 1998 in the field and in 2002 in the laboratory indicated that atrazine “feminized” some species of amphibians, causing excess estrogen production in genetic males.

In addition to the feminizing issues of atrazine, other problems with amphibians have been linked to the herbicide, including limb deformities, changes in population structure, desiccation , increased susceptibility to disease, and direct mortality.

Although the potential hazards from atrazine are broad, EPA’s question about it was narrow: Does it affect gonadal development?

The pioneer researcher and lead expert on this topic is UCLA biologist Tyrone Hayes. Hayes did his original pioneering work when he discovered this connection under a contract from Syngenta. The company was not too pleased with this discovery. Hayes exited from the Syngenta contract in 2000.

Tyrone Hayes
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Hayes vigorously disputes EPA’s finding that atrazine’s impact on amphibians is unproven. His work has shown an effect even at very low doses — 0.1 parts per billion. If this conclusion is correct, there would be almost no safe alternative to a banning of the herbicide.

In an interview, Hayes said:

“We’ve got now, after eight years and three generations, we’ve got genetic males that were exposed to atrazine that are complete fertile females. I originally consulted for Syngenta on this issue. The original work — some of which they reported to EPA, some of which they did not — was conducted by me and paid for by Syngenta.

Hayes says that the scientists subsequently hired by Syngenta also showed the same results, “but they reported in the press that they couldn’t repeat my work.”  Japanese researchers in 2003, Miyahara et al. sponsored by the Japanese government, confirmed that exposure to as little as 1 ppb of atrazine caused estrogen production in frogs, specifically the species Xenopus laevis (African clawed frog), which is the same one on which EPA’s recent conclusions are based. This Japanese paper is not mentioned in the EPA white paper on its findings.

In the December 2004 journal Bioscience, Hayes produces a graph listing all the studies done up to that time attempting to answer the question “Does atrazine affect frog gonads?” He lists 15 studies, nine of which were sponsored by Syngenta, and six sponsored by other independent sources. Every study paid for by Syngenta concludes that atrazine has no effect. Every study paid for by someone else shows that atrazine does affect amphibian gonads.

In its 2007 white paper on the atrazine findings, EPA lists 19 papers that address the questions. The same pattern holds. Those papers sponsored by Syngenta found no impact. Those papers with research paid for by others found significant impact.

After reviewing this published research, EPA found:

“Overall, the weight-of-evidence based on these studies does not show that atrazine produces consistent, reproducible effects across the range of exposure concentrations and amphibian species tested. In laboratory studies where environmental and animal husbandry factors were controlled, atrazine exposures did not affect time to or size at metamorphosis, sex ration, or gonadal development.”

The agency concluded no further testing is needed.

Syngenta spokeswoman Ford said:

“You’ve got to start somewhere. EPA’s 2003 Scientific Advisory Panel agreed that the first thing that needed to be done was to determine if atrazine was affecting the sexual malformation of frogs. That was our starting point. That was our charge. So that’s what we did.

“What the 2007 Scientific Advisory Panel told us at the end and throughout the meeting was that they agreed with the results that the study showed, that atrazine did not affect gonadal development on Xenopus laevis.

Jason Rohr, a biologist at the University of South Florida who has studied the effects of atrazine on amphibians, though not specifically on gonadal development said:

“One of the rules in ecotoxicology is that there is going to be a tremendous amount of variation in response to any substance. Just because its shown that one frog responds this way to one substance doesn’t mean that all frogs will. Its very possible that some frogs are very sensitive but die before we even get to them.”

Andrew Storfer, a biologist at Washington State University, has also published extensively on atrazine and amphibians. He said his work shows that atrazine compromises the immunity of tiger salamanders, increasing their disease risk. He said of EPA’s decision:

“We need to be cautious. Whenever we look at a pesticide it can have many effects on animals, which include gonadal deformities. It can also include effects on their growth rate — we saw negative effects of atrazine on growth rate. It can also have negative effects on the immune system — and we showed that with tiger salamanders.

“And in conjunction with other stressors, because no animal receives just one stressor in the environment, we need to be cautious when we start looking at pesticides, that we consider many different environmental variables that animals are facing in nature before we say they are safe or not.”