Softeners in plastics may affect masculinity in young boys, study says


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Boys born to mothers who have above-normal levels of the controversial chemicals known as phthalates in their urine are less likely to exhibit masculine behavior, a new study has found. Phthalates, which block the activity of male hormones such as androgens, could be altering masculine brain development, according to Shanna H. Swan, a professor of obstetrics and gynecology at the University of Rochester Medical Center and lead author of the new report.

Phthalates are widely used to soften plastics such as polyvinyl chloride and make them flexible. They are used in food packaging, vinyl and plastic tubing, household products and many personal care products, such as soaps and lotions. Although the Food and Drug Administration considers them safe, a 2008 federal law banned the use of six different types in toys such as teethers, bath items, soft books, dolls and plastic figures.


Swan had previously shown that some small boys and toddlers exposed to phthalates in the womb had subtle changes in the size and anatomy of their genitals. Researchers are planning to follow those boys into adulthood to determine if there are changes in their sperm count or if they have reproductive problems.

In the new study, Swan and her colleagues focused on a small group of women who gave birth between 2000 and 2003. Urine samples collected in the 28th week of pregnancy were analyzed for phthalates by the Centers for Disease Control and Prevention.

When the children were between 3½ and 6½ years of age, the team administered a standard questionnaire called the Preschool Activities Inventory or PSAI that assessed the types of toys children selected (trucks versus dolls, for example), activities such as rough-and-tumble play and other characteristics. They will report Monday in the International Journal of Andrology that the boys whose mothers had the highest levels of the chemical in their urine were the least masculine in their playtime activity. Girls were not affected.

‘Our results need to be confirmed, but are intriguing on several fronts,’ Swan said. ‘Not only are they consistent with our prior findings that link phthalates to altered male genital development, but they also are compatible with current knowledge about how hormones mold sex differences in the brain, and thus behavior. We have more work to do, but the implications are potentially profound.’

— Thomas H. Maugh II

Boys who were exposed to phthalates in the womb were less likely to exhibit masculine play, according to a new study. Credit: Los Angeles Times / Al Schaben