Plastic chemical makes boys act like girls

By Sheilah Downey

A pilot study released Monday showed that when phthalates in a woman's prenatal urine are elevated, their sons are less likely to play the traditional boy games, such as fire trucks and pretend fighting.

Phthalates, chemicals used to soften plastics, have been shown in previous studies to alter male genital development, according to the study from the University of Rochester Medical Center. They have also been associated with genital defects, metabolic abnormalities and reduced testosterone in babies and adults.

Scientists in this study are concerned that fetal exposure to phthalates has the potential to alter male brain development, because testosterone produces the masculine brain, according to lead author Dr. Shanna H. Swan, professor of obstetrics and gynecology and director of the URMC's Center for Reproductive Epidemiology.

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

The study focused on a small sample of mothers in the federally-funded Study for Future Families program, run by Dr. Swan since 1998. Swan looked at mothers who delivered children between 2000 and 2003 and analyzed their urine samples at the 28th week of pregnancy.

Swan hypothesized that phthalates may lower fetal testosterone production during a critical window of development when the testes begin to function and may alter brain sexual differentiation.

The major source of human exposure to two phthalates of most concern, DEHP and DBP, is through food, according to recent studies. Those phthalates are used primarily in polyvinyl chloride, PVC, so anything stored, processed, packaged or heated using PVC-containing products can introduce them into the food chain, said the study.