Oct. 6, 2009 -- New research suggests a link between prenatal exposure to the chemical bisphenol A (BPA) and increased aggression in girls, but not boys, at age 2.
The finding is far from conclusive, but the study is the first human trial to attempt to examine whether BPA exposure in the womb influences behavior in early childhood.
BPA has been used for more than three decades to make plastic bottles and other products shatter resistant and clear. It is also used in the lining of many canned foods and in a wide range of other commercial goods.
The chemical was found in the urine of more than 90% of Americans in a random sample conducted by CDC researchers in 2007.
For close to a decade, scientists have debated whether exposure to BPA through commercial products poses a health threat to humans. Hundreds of animal studies suggest it might, but only a few human studies have been published.
BPA and Behavior
In the newest one, researchers followed 249 women during pregnancy until their children were 2 years old.
BPA concentrations were measured in the urine of the moms-to-be in their 16th and 26th weeks of pregnancy and soon after delivery.
When the children turned 2, the mothers completed a widely used behavior survey designed to assess their child's personality with emphasis on internalizing and externalizing behaviors.
Internalizing behaviors include being depressed, nervous, or withdrawn. Externalizing behaviors include aggression and hyperactivity.
Researchers concluded that the girls exposed to the highest levels of BPA earlier in pregnancy tended to exhibit more externalizing behaviors at age 2 than girls exposed to lower levels of the chemical.
Boys whose moms had the highest BPA levels exhibited slightly more internalizing behaviors, but the association was not as strong as that seen in girls, study researcher Joe M. Braun tells WebMD.
In most cases, the behaviors did not reach the level of clinical concern.
"For most of the children, behavior was in the normal range," he says. "But I was surprised by the magnitude of the effect we saw."
Braun, who is a research assistant at the University of North Carolina at Chapel Hill, says the finding needs to be confirmed in separate studies.
The study appears today online in the journal Environmental Health Perspectives.
"These findings suggest that BPA exposure may impact children's development, but more research is needed to prove this," he says.
The federal government's National Toxicology Program has initiated research that should provide a clearer picture of the effects, if any, of BPA on health, National Toxicology Program Associate Director John R. Bucher, PhD, tells WebMD.
Last fall, the National Toxicology Program issued a report examining the potential health impact of BPA exposure from commercial products, concluding that there was cause for "some concern" about the effects of current exposures on the brain, behavior, and prostate gland development of fetuses, infants, and children.
The National Toxicology Program concluded that while the human studies were lacking, many of the almost 1,000 animal studies showed that BPA exposure at relatively low levels can influence certain aspects of fetal development.
But American Chemistry Council executive director of the polycarbonate/BPA global group Steve Hentges, PhD, calls the research as a whole "reassuring."
"The weight of the evidence continues to indicate that trace levels of bisphenol A are not a health risk," he says.
Hentges tells WebMD that one major problem with the newly published study, and with all human studies, is that there is no consensus on how to best measure BPA in the body.
BPA comes from the foods we eat, so over the course of the day levels can vary dramatically, making it difficult to assess exposure with a single measurement.
He says the study's small sample size may have also influenced the findings. And he points out that the behavioral differences seen in the children were small.
"Even if you took at face value that there is an association, it is not clear what the clinical or medical significance would be since these children did not meet the standard for behavior problems," he says.