A new study finds that exposure to bisphenol A before birth may lead to behavior problems in girls by age 3. The findings, published in Pediatrics, promise to heat up the debate over the safety of BPA, the ubiquitous chemical found in water bottles, linings of cans and even on the register receipts we get at the checkout stand.
Led by Joe Braun, a research fellow at the Harvard School of Public Health, the study suggests that exposure to BPA, especially in developing fetuses, may be long-lasting. Among a group of 244 mothers and their 3-year-olds whose BPA levels were measured in their urine, moms who had higher BPA levels during pregnancy were more likely to have children who were aggressive, anxious and hyperactive and showed poor emotional control, compared with moms with lower levels of BPA. The children’s own BPA levels did not have an effect on their behavior patterns.
The results highlight how important the pregnancy period is to early brain development, and suggest that there are critical windows during which exposure to chemicals like BPA can perhaps permanently influence a child’s emotional and behavioral state. “It’s possible that the brain is more vulnerable to the effects of BPA during certain parts of pregnancy, such as the early stages, and not as vulnerable later,” says Braun. “Certain events take place in the brain, and once they take place, they are done.”
Earlier studies in animals have linked BPA exposure in the womb to aggressive and anxious behavior among offspring, and studies in young children have linked the chemical to asthma.
The scientists tested pregnant women for BPA at 16 and 26 weeks gestation and at birth. Their children were tested annually until age 3. About 97% of the moms and children showed some BPA in their urine, confirming previous data from the Centers for Disease Control and Prevention, which show that nearly all Americans have a measurable amount of the chemical in their systems.
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The results held strong even after the researchers adjusted for other possible contributors to the children’s behavior, such as breast-feeding, mother’s education, depression and marital status, and possible study confounders such as differences in the strength of the urine samples. The results were the first to look at how BPA may affect executive functions of the brain, which regulate reasoning and planning as well as control of emotions. For every 10-fold increase in the mothers’ gestational BPA concentrations, the children showed a 9-to-12-point increase in impulsivity and a lack of emotional control.
“The data suggest that at exposures that humans are typically exposed to, there seems to be an effect of BPA on behavior,” says Braun.
The effect was more striking in girls than in boys, which hints at differences in the hormonal factors that may regulate development of executive and behavioral activities of the brain. Girls in the study were more than twice as likely as boys to show anxiety and depression if their mothers had been exposed to BPA. It’s possible that BPA may be boosting levels of the hormone estradiol in female fetuses, disrupting the normal sexual differentiation of the brain, leading it to become more masculine. In animal studies, the female hormone estradiol has been shown to convert to testosterone in males, resulting in masculinization.
Braun says it’s not exactly clear yet why BPA may affect girl and boys differently, but he is hoping to investigate these results further to find out. More studies will also reveal whether there is a threshold level of BPA that triggers these changes in fetal brain development.
In the meantime, how should an expectant mom reduce her exposure to BPA? The Food and Drug Administration stands by its claim that current use of the chemical in food packaging is safe, but Braun says moms-to-be may reduce their exposure by avoiding canned and packaged foods. Whether or not pregnant women should also avoid handling thermal register receipts is less clear; there’s a study currently underway that is investigating whether day-to-day handling of these receipts can significantly increase exposure. “To be precautionary,” Braun says, especially for those who work at registers, “it’s reasonable to wear gloves.”