Pesticides lower sperm levels, study finds
By Rita Rubin

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Scientists for the first time have shown a link between levels of widely used agricultural pesticides in men's bodies and the number and quality of their sperm.

In a study out Wednesday, researchers found that men with higher levels of three pesticides widely used in the Midwest were more likely to have below-average semen quality and sperm counts than men with lower levels of the chemicals.

The scientists studied 50 men in rural Missouri and 36 men in Minneapolis. Their wives were patients at prenatal care clinics, so they were fertile. Based on semen samples, the men were divided into two groups: those with low sperm counts and quality and those with better semen quality.

"It's interesting that even within fertile men, there's a huge range," says lead author Shanna Swan, a family and community medicine professor at the University of Missouri-Columbia.

A Centers for Disease Control and Prevention lab measured levels of the byproducts of 15 different pesticides in urine samples from the men. Men with higher levels of alachlor, atrazine and diazinon were significantly more likely to have poorer sperm quality, the researchers report in the journal Environmental Health Perspectives. All three pesticides were more likely to be found in high levels in the Missouri men than in the Minneapolis men.

Only two of the Missouri men were farmers. Swan and her coauthors speculate that the men were exposed to the pesticides through drinking water. According to the authors, usual water treatment methods cannot remove them.

Ken Gordon, a spokesman for Syngenta, which makes atrazine, says there have been more than 800 studies of its health effects. "An overwhelming body of research supports the safety of atrazine for humans and the environment," Gordon says.

Rex Hess, a reproductive toxicologist at the University of Illinois-Urbana, praised the design and execution of Swan's study. The logical next step would be to test drinking water in Missouri for the pesticides, Hess says.

Reproductive biologist Sally Perreault of the Environmental Protection Agency says rodent studies suggest that even the highest pesticide levels found in Swan's subjects would have been too low to affect sperm quality. Still, Perreault says, the new study "really does raise a flag."