New data strengthen link between phthalates, problems with male genitals

In 2005, Shanna Swan of the University of Rochester published the first data in humans linking prenatal exposure to phthalates with altered genital development in baby boys. She discovered the connection in a long-term pregnancy study in which she sampled the urine of pregnant moms for phthalates, then examined their babies after birth.

Now, Swan has published updated and expanded data with analysis that highlights problems in four new areas:

• Penis size — the new analysis makes a direct link between exposure to some phthalates (metabolites of DEHP) and smaller penis size.
• Implicates more phthalates — Swan found a significant relationship between a shorter anogenital distance (a measure of feminization in boys) with five phthalates, including all metabolites of the widely used DEHP.
• Additive effects—the study shows a significant association between total phthalate exposure and shorter anogenital distance, suggesting that phthalates are having an additive effect as they do in animals.
• Undescended testes—the data link higher exposure to DEHP metabolites to a higher incidence of undescended or incompletely descended testes.

Swan writes, “These findings warrant current concerns that low dose phthalate exposures affect several markers of human male genital development.” She likens the conditions of the more exposed baby boys to those found in the “phthalate syndrome” discovered in rodents, and warns that reproductive effects in girls “are hidden and may be missed until puberty or adulthood.”

Swan’s findings were published in Environmental Research’s latest issue in an article titled "Environmental phthalate exposure in relation to reproductive outcomes and other health endpoints in humans."

Erika Schreder is a staff scientist at Washington Toxics Coalition, where she leads the Coalition’s research on toxic chemicals in children’s products. In 2005 and 2006, she led the research for the Toxic-Free Legacy Coalition’s Pollution in People study. She has a Masters in Resource Ecology and Management from the University of Michigan and a B.S. in molecular biology from MIT.