Men exposed to pesticides widely used on crops are many times more likely to have defective sperm and low sperm counts than males with little or no exposure, according to a scientific study published today .
The study provides new evidence supporting a theory that pesticides and other chemicals which mimic estrogen or block testosterone are harming human reproductive systems. It is the first time that scientists have shown a link between environmental contaminants in men's bodies and large decreases in the number and quality of their sperm.
A team led by University of Missouri-Columbia reproductive epidemiologist Shanna Swan compared men from central Missouri who had higher concentrations of two herbicides and one insecticide in their bodies with men from Missouri and the Minneapolis area who had low levels.
"Within Missouri, the pesticide score [of the men] was strongly associated with semen quality," the authors reported in the journal Environmental Health Perspectives, which is published by the National Institute of Environmental Health Sciences.
None of the men in the new study worked at or lived next to farms, where the pesticides are most commonly used. They were most likely exposed through drinking water supplied by aquifers, Swan said.
The number of men tested for pesticides -- 50 from Missouri and 36 from Minnesota -- is considered small, but scientists said the findings warrant close attention because some of those tested were found to be 30 times more likely to have defective sperm. That degree of risk is in the same range as the odds of contracting lung cancer from a lifetime of smoking cigarettes.
All the tested men, in their 20s and 30s, were fertile and recently fathered children.
"What this means is that it's harder for these men to conceive. It takes them longer," Swan said. "We also wonder what else it is doing to these men, and what it is doing to the rest of the family, the women and children?"
Sally Perrault, a reproductive toxicologist at the U.S. Environmental Protection Agency's national research lab, said the study "really raises our antennae."
Still, she said, Swan's team "hasn't proven that [the pesticides] came from the water" and that more men should be tested before the safety of the pesticides is questioned. "We should look into this more, rather than drawing real definite conclusions now," she said.
