“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,” shrieked USA Today this week.
Steady, USA Today (search). Underwear, rather than pesticides, is a more probable explanation.
McNews had the wool pulled over its eyes by University of Missouri-Columbia eco-activist researcher Shanna Swan (search), who has been crusading since the mid-1990s to link pesticides with supposed reduced sperm counts.
The latest chapter in Swan’s crusade began in April when she reported that a small sample of men from Boone County, Mo., had lower sperm quality than similarly small samples of men from Los Angeles, Minneapolis and New York City.
Based on further “analysis,” Swan now reports in a study published in the June 18 Environmental Health Perspectives (search), the 50 Missouri men had higher levels of metabolites of widely used pesticides (search) (alachlor, diazinon, atrazine and others) in their urine than the 50 Minneapolis men.
Swan concluded: “This is the first population-study to demonstrate links between specific biomarkers of environmental exposures and biomarkers of male reproduction in humans. Given the current widespread use of these pesticides, if further study confirms these findings, the implications for public health and agricultural practice could be considerable.”
In the first place, I’m not quite sure what the dreaded “implications” of Swan’s data are since all men in the study were fertile. They were, in fact, the partners of pregnant women recruited at prenatal clinics.
Secondly, there’s no known biological support for Swan’s idea that pesticides affect sperm quality. Tests do not indicate that alachlor, diazinon and atrazine, for example, produce toxic effects in the reproductive systems of laboratory animals.
A reproductive biologist from the Environmental Protection Agency (search) told USA Today that rodent studies suggest that even the highest pesticide levels found in Swan’s subjects would have been too low to affect sperm quality.
And just because the Missouri men had lower sperm counts and higher pesticide exposure than the Minneapolis men doesn’t automatically mean that pesticides have anything to do with sperm production.
A University of Virginia fertility expert told The Associated Press that he was skeptical of the findings because of the lack of historical documentation of the effect of toxins on sperm.
Sperm counts are known to vary geographically. There is no certain explanation for the phenomenon, although some studies indicate that men in colder regions seem to have higher sperm counts than men in warmer areas.
And it’s really not surprising that men from the agricultural Boone County, Mo., would have more pesticide exposure than an urban area such as Minneapolis.
Swan’s data simply aren’t unexpected and her tenuous conclusions aren’t surprising given her track record of eco-activist, anti-pesticide “research.”
Though anti-pesticide activists (search) have tried for years to link pesticides with declining sperm counts, one key fact stands in their way -- there’s no evidence that sperm counts are even declining, much less that pesticides are involved.
In 1999, researchers published in the Journal of Urology (search) a review of all 29 studies from 1938 to 1996 reporting semen analyses of fertile men. They concluded, “there appears to be no significant change in sperm counts in the U.S. during the last 60 years.”
Sperm counts (search) and quality depend on many factors. One that Swan overlooked in her study was the effect of tight-fitting underwear.
In 1996, Dutch researchers reported in the British medical journal The Lancet (search) the results of their study of the effect of underwear on sperm quality and quantity.
They reported that men who wore tight-fitting underwear produced 50 percent less sperm than men who wore loose-fitting underwear. Sperm motility was reduced by two-thirds among the men who wore tight-fitting underwear.
Maybe the Missouri men in Swan’s study wore tighter underwear than their Minneapolis counterparts. I don’t know. Neither does Swan -- she didn’t check.
I do know that Swan has absolutely no evidence that implicates pesticides and exculpates all other potential factors. Regardless of the explanation for Swan’s reported observations, sperm quality differences apparently did not affect anyone’s fertility.
Perhaps it’s time for Swan to spend time reconsidering the quality of her crusade.
Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author ofJunk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).