Harvard Men's Health Watch

Medical memo: Insecticides, testosterone, and fertility

Medical memo

Insecticides, testosterone, and fertility

Insecticides have produced major benefits for America's farmers and businessmen, as well as for gardens and homes just like yours. But because they are toxins, the chemicals that kill unwanted critters also have the potential to affect human health. And a study from the Harvard School of Public Health and the Centers for Disease Control and Prevention suggests that one insecticide may reduce the levels of male reproductive hormones and impair sperm quality.

The chemical in question is chlorpyrifos, an insecticide that is toxic to a wide range of organisms rather than a single species. Although it is classified as "nonpersistent," when applied indoors or tracked in from outdoors, it can persist for extended periods. In one case, for example, it was found in household air four years after it was applied in the home.

In 1999, some 13 to 19 million pounds of chlorpyrifos were applied in the U.S. The Environmental Protection Agency subsequently restricted residential use, but a 1999""2000 survey reported that over 90% of American men had traces of TCPY, a metabolite of chlorpyrifos, in their urine. And a related insecticide, carbaryl (Sevin) is still widely applied to lawns and gardens, which is why over 75% of American men have traces of its metabolite, 1N, in their urine.

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