Oct. 24, 2011 -- Preschoolers exposed to higher levels of bisphenol A (BPA) in the womb may have more anxiety and depression and have worse self-control than those exposed to lower levels of the chemical before birth, a new study shows.
The chemical is found in a wide array of consumer products, including plastic bottles, food packaging, dental sealants, and the heat-activated paper that's used to print cash register receipts.
A spokesman for an industry group says the new study had flaws in its design, and that other studies have found BPA to be safe.
The chemical structure of BPA is similar to the hormone estrogen. That raises concerns that constant exposure could have biological effects, particularly for developing babies and young children.
Studies of animals exposed to BPA have found changes in the brain, behavior, and abnormal development of reproductive organs. So far, there has been less evidence of health effects in humans.
The new study is published in Pediatrics. It is one of the first to show that BPA exposure in the womb may be linked to behavioral effects in young children.
Researchers caution though that their study was only able to show associations between BPA and behavior. It did not prove cause and effect.
In an emailed statement, Steven G. Hentges, PhD, of the American Chemistry Council's Polycarbonate/BPA Global Group, says it is unlikely that BPA caused the behavioral effects documented in the study. "The study released in Pediatrics has significant shortcomings in study design and the conclusions are of unknown relevance to public health. Furthermore, regulators from Europe to Japan to the US have recently reviewed hundreds of studies on BPA and repeatedly supported the continued safe use of BPA."
Childhood Behavior and BPA
For the study, researchers followed 244 mothers and their babies from pregnancy through age 3. They measured BPA levels in three urine samples taken from pregnant women and three samples collected from their kids at yearly study visits.
After the children's third birthday, researchers gave parents two well-regarded psychological tests to evaluate their child's behavior and their capacity for self-control. Parents were not given information about their BPA levels before they rated their child's behavior.
While there was no association between the BPA in a child's urine and their behavior, the researchers found that moms who had higher levels of BPA in their urine during pregnancy also had 3-year-olds with more anxiety, depression, and hyperactivity.
Anxiety and depression associations were almost twice as large for girls as they were for boys.
Girls had higher scores on measures of hyperactivity while boys had lower scores for hyperactive behavior.
That was true even after researchers took into account a host of things that are known to influence a child's behavioral development, like mom's IQ and education, breastfeeding, household income, maternal depression, and exposure to tobacco smoke.
"The results suggest that these gestational exposures, or the mother's exposure, are more important than the childhood exposures," says researcher Joe Braun, MSPH, PhD, research fellow in the department of environmental health at the Harvard School of Public Health.
Braun says girls may be more susceptible to the effects of BPA during their development than boys. He's not entirely sure why, but he has a theory.
"We know that sex steroids are important in the development of masculine and feminine behaviors, and it's possible that BPA is acting like a weak estrogen," Braun says.
"In rodents, estrogen actually masculinizes the brain," he says, which could explain the sex differences they saw in hyperactivity. Hyperactivity tends to be more common in boys than girls.
"It's definitely a study that's worth paying attention to," says Amir Miodovnik, MD, an attending pediatrician at the Mount Sinai School of Medicine in New York City. "But you can't take away from it that a child exposed to BPA problems in the womb is going to have behavioral problems. It's not clear-cut like that."
Miodovnik has also studied childhood exposure to BPA and its associations with behavior, but he was not involved in the current research.
"It's important in terms of corroborating some of the animal studies that have found effects. And there are many animal studies that have found effects at low levels. And here we're finding effects at levels that are found in the normal population."
But the behavioral changes documented in the study were small, and "how that applies to an individual child is difficult to say," Miodovnik says. They may not make a real difference in a child's life, he notes, in the long run.
Another expert has a slightly different perspective.
"This study raises further concerns about the subtle, but nonetheless measurable adverse effects of BPA exposure," says Andrew Adesman, MD, chief of developmental and behavioral pediatrics at Steven and Alexandra Cohen Children's Medical Center of New York in New Hyde Park.
"Consumers in general should try to minimize exposure to this chemical," he says.
Studies have shown that most of an average person's individual exposure to BPA comes from diet. Many frozen, processed, and canned foods are contained in packaging that contains BPA.
The good news, researchers say, is that BPA is quickly eliminated from the body.
A study published in March showed that children and adults who ate only fresh, organic, and unpackaged foods for three days reduced their BPA levels by 66%.
Reducing Exposure to BPA
Until more is known, Braun says, pregnant women shouldn't drive themselves crazy trying to stay away from BPA.
"Consumers, if they're concerned, can try to reduce their exposure by reducing their exposure to packaged and canned foods but at the same time, they should still maintain a balanced and healthy diet.
"There are canned foods that are good for you," Braun tells WebMD. "Those are healthy foods and you shouldn't be replacing them with hamburgers and French fries."