BPA exposure in mothers may affect unborn daughters’ behavior: Study

By Dr. Ananya Mandal, MDOct 25 2011

A new federal study revealed Monday in the journal Pediatrics shows that bisphenol A (BPA) - a chemical used widely in plastic bottles, metal cans and other consumer products could be linked to behavioral and emotional problems in toddler girls.

The researchers from Harvard School of Public Health and the Centers for Disease Control and Prevention looked at 244 Cincinnati-area mothers and their 3-year-olds and found that mothers with high levels of bisphenol A (BPA) in their urine were more likely to report that their children were hyperactive, aggressive, anxious, depressed and less in control of their emotions than mothers with low levels of the chemical. The results were based on urine samples from the mother (two during pregnancy and one at birth) and urine samples from their children taken at ages 1, 2 and 3. The mothers then filled out surveys about their children’s behavior at age 3.

There have been earlier studies linking BPA to behavioral problems in children but this is the first to suggest that that a young girl’s emotional well-being is linked to her mother’s exposure during pregnancy rather than the child’s exposure after birth. Girls were more sensitive to the chemical in the womb than boys, maybe because BPA mimics the female hormone estrogen, which is thought to play a role in behavioral development.

While the federal government has long maintained that low doses of BPA are safe, the Food and Drug Administration and other federal agencies are taking a closer look and investing in more research about the chemical’s health effects.

Authors admit however that their results could have been skewed by the eating habits of the mothers observed. For more than 40 years, BPA has been used to make plastic bottles and the lining of metal-based cans. It’s possible that mothers who ate a lot of packaged foods simply didn’t eat enough nutrients essential for brain development, said Joe M. Braun, the study’s lead author. Braun, a research fellow at the Harvard School of Public Health added that none of the children exhibited behavior outside the normal range but they behaved worse than children whose mothers had relatively low traces of BPA in their urine.

Researchers detected BPA in more than 95 percent of pregnant women who participated in the study, and each tenfold increase in BPA was associated with more behavioral and emotional problems in girls, according to the study.

“We certainly can't determine what it is doing in this study, but we have a couple of guesses,” Braun said. “Sex [hormones] are important in brain development. BPA is an endocrine-disrupting compound. It may act like an estrogen, or an anti-estrogen.” Indeed, animal studies show that BPA exposure during pregnancy affects sexual behavior in female rats. “In rats, we know that we can make their girls more masculine,” Braun said. “Boys are already masculinized by their testosterone levels.” There is evidence that BPA could interfere with dopamine, a neurotransmitter associated with regulation of behavior. BPA exposure “may be a risk factor for ADHD,” Braun said.

The American Chemistry Council, which represents the chemical industry, dismissed the study, saying it has “significant shortcomings” in design and its conclusions “are of unknown relevance to public health.” The group added that the study had a small sample population and thus culd not be definitive. Braun said it’s difficult to conduct this type of research with a larger group. Several experts who track the issue said they would like to see the study repeated with another larger group of children.

The study supports “a growing body of evidence” that BPA can affect brain development in the womb, said Shanna Swan, a professor at Mount Sinai School of Medicine. “This study finds associations between neurodevelopmental endpoints and gestational BPA, but none with exposure to BPA in childhood, confirming the sensitivity of the prenatal period to this exposure,” she said.

Whether pregnant women should attempt to avoid BPA is a personal choice, Swan said. “But avoiding obvious sources, like canned foods, is not difficult and alternatives are easily available,” she said. “That is a relatively easy change to make that should reduce exposure and, thus, may reduce risk.”

Julie Herbstman, an associate professor at the Columbia Mailman School of Public Health, also said avoiding BPA could be a good idea. “I agree with the authors' conclusions to advise concerned parents to be precautious, and to try to reduce BPA exposure during pregnancy,” she said.

Linda Birnbaum, director of the National Institute of Environmental Health Sciences, said the sample size is reasonable and its results support studies that show similar effects in animals. The challenge with observational studies such as this one, she said, is that the effects are subtle and, therefore, tougher to tease out. “These are not the kinds of effects that hit you over the head,” Birnbaum said. “We’re not looking for missing arms and legs.” Birnbaum’s group and the Environmental Protection Agency funded the study.

Due to consumer pressure, some companies have voluntarily removed the chemical from products or started offering BPA-free alternatives. A number of states and cities, including Maryland, have banned BPA in some children’s products. France has taken action to prohibit BPA uses in food packages altogether, but the ban has not yet taken effect. Earlier this month, the American Chemistry Council petitioned the FDA to ban the use of the chemical in baby bottles and sippy cups. The council however maintains that BPA is safe.

Regardless, more research is needed, Braun said. “We certainly need to confirm … the impact of mothers' exposure and children's exposure to see if these results hold,” he said. Research could also attempt to determine when during pregnancy babies' brains are most sensitive to BPA exposure, Swan said.