Common Chemical Exposure May Affect Male Reproductive Development, Study Finds

June 01, 2005

In a small, preliminary study, researchers have found a possible link between abnormal male genital formation and a mother’s prenatal exposure to phthalates, a class of chemicals commonly used in household products, plastics, cosmetics, and universally present in the environment.

Previous studies have shown that phthalates emasculate male rats. Researchers set out to explore whether the chemicals might also affect human male reproductive health. The June issue of the journal Environmental Health Perspectives reports the findings of lead author Shanna H. Swan, Ph.D., professor of Obstetrics and Gynecology at the University of Rochester Medical Center, and colleagues.

Researchers analyzed urines samples from 85 expectant mothers for phthalate levels, and scored the samples as “high, “medium,” or “low.” At a mean age of 12.6 months, the resultant male children were then examined for genital characteristics that serve as markers for normal development, including anogenital distance – a measure of masculinization previously shown in rodent studies to be altered by prenatal phthalate exposure. The boys’ measurements were correlated with the mothers’ phthalate levels.

Of the 85 mother-son pairings, the 10 cases with the highest phthalate exposure scores included 9 boys who exhibited the strongest abnormalities, such as shorter anogenital distance, incompletely descended testes and smaller penises. Since the findings were consistent with the previous animal studies, Swan and colleagues believe that exposure to phthalates in the womb may be involved in suppressing male sexual development. The research is the first human study to support that hypothesis.

“We would need to follow these male babies into adulthood before we can determine what long-term effects, if any, this class of chemicals might have on their reproductive health,” Swan said.

Swan is also presenting her research on Friday, June 3, at The Forum on Endocrine Disrupting Chemicals, presented by The Endocrine Society in conjunction with its 87th annual meeting in San Diego, Calif.

Grants from the U.S. Environmental Protection Agency and the National Institutes of Health funded the study. The journal EHP is published by the National Institute of Environmental Health Sciences.

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