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Atrazine gets an OK

Atrazine is often the poster child for links between farm chemicals and human cancer rates. Still, an extensive multiyear federal Agricultural Health Study (AHS) recently found no consistent association between atrazine and cancer rates on farmers, farm spouses, and pesticide applicators.

“This is good news,” says Tim Pastoor, a toxicologist and principal scientist with Syngenta. Findings are consistent with those from a 2006 triazine federal reregistration that was started in 1994 and included more than 6,000 scientific studies. Syngenta manufactures and sells atrazine, a compound in the triazine chemical family.

“Atrazine is one of the most tested molecules on the face of the earth,” says Pastoor. “With all the information developed on atrazine, this (AHS) gives us a greater degree of assurance about decisions made about the product. All studies augment the knowledge we have on atrazine and reaffirm that it can be used safely.”

The study

The AHS started in 1993 to investigate relationships between aspects of living and working on a farm, including hazardous substance exposures and cancer risk, and relationships with other health problems. Most of the cancer research focused on more than 20 pesticides including atrazine.

The AHS included 89,000 farmers, pesticide applicators, and spouses in Iowa and North Carolina. Federal agencies involved included the National Cancer Institute, the National Institute of Environmental Health Sciences, the Environmental Protection Agency (EPA), and the National Institute of Health.

The study examined types and frequency of pesticides that individuals had been exposed to, along with the degree of protective equipment used. Participants also submitted individual health records including cholesterol amounts, blood pressure, and disease diagnosis. Scientists statistically corrected for factors like use of smoking and chewing tobacco, factors proven to cause cancer.

“Based on all of that pulled together, they looked at the usage of a particular pesticide and relationship of adverse health effects,” says Pastoor.

The AHS findings reinforce results in previous studies that there is no consistent link between atrazine and cancer rates in humans.

The only possible concern was thyroid cancer. The study broke out degrees of exposure in four areas ranging from high to low.

“When you look at the incidence of thyroid cancer, there was an increase in the folks who were exposed to atrazine the most and those who used it the least, but not in between,” says Pastoor. “This raises an epidemiological statistical yellow flag that scientists will continue to examine.”

However, he adds, no firm relationships were established between atrazine exposure and thyroid cancer.

What's up next?

Federal regulators reregistered atrazine in 2006. In 2009, the Obama administration ordered a re-evaluation of atrazine based partially on concerns that atrazine may be related to certain human cancers.

The AHS findings bode well for atrazine safety and for the farmers who use it, says Pastoor. Even if EPA gives atrazine its blessing in its re-evaluation, though, it's not the end of federal oversight. In 2013, the routine pesticide reregistration cycle starts up again for atrazine.

For now, farmers can continue using it safely, says Pastoor. It is a popular corn herbicide often contained in herbicide mixes.

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