RALEIGH, N.C. - Pre-birth exposure to a chemical widely used in plastics appears to be linked to more aggressive behavior in little girls, according to research published this week by a scientist at the University of North Carolina, Chapel Hill.
The findings, which are preliminary, are the first to connect behavior problems in humans with the chemical bisphenol A, a key component of plastic bottles, the liners inside canned goods and medical devices.
Some have called for curbs on BPA, and Canada last year became the first country to ban BPA in baby bottles. Afterward, Wal-Mart and Toys R Us announced they would stock only BPA-free baby bottles, toys and baby food containers. Earlier this year, Suffolk became the first county in the United States to ban the use of BPA in baby bottles and sippy cups.
BPA leaches from plastic and is detectable at some level in nearly everyone's system. Scientists began to raise concerns about BPA because of its tendency to mimic estrogen, a hormone that plays a key role in establishing the sex differences in the brains of developing fetuses.
Studies in mice have shown fetal BPA exposure can abolish or reverse inherent behavioral differences between the sexes - specifically, females act more aggressively - and those studies prompted questions about what the chemical does to humans.
The American Chemistry Council and BPA plastics manufacturers in Europe and Japan cite studies showing the chemical additive is safe. The groups note BPA doesn't appear to cause cancer, and that "the potential human exposure to BPA from polycarbonate plastic and epoxy resin food contact applications is minimal and poses no known risk to human health."
Joe Braun, a doctoral student in epidemiology at the UNC Gillings School of Global Public Health and one of the authors of the aggression study published in the journal Environmental Health Perspectives, said researchers began examining the effects of BPA two years ago with a group of pregnant women enrolled in a larger study into lead.
The researchers measured BPA levels in urine samples from 249 women at three different times during their pregnancies: At 16 weeks, 26 weeks and birth. Later, they observed the women's children at age 2, using a standard behavioral test.
They found women who had the highest concentrations of BPA at 16 weeks of pregnancy were inclined to have more aggressive, hyperactive 2-year-old daughters. There was no statistically significant change of behavior among the boys, although there was some evidence of heightened anxiety and depression.
"It's an intriguing finding that suggests the need for more research in this field, especially with prenatal exposure and the timing of exposures," Braun said.
Timing is especially important from a regulation standpoint. The work of Braun's team suggests the time to limit exposure is in the womb - maybe even before many women know they are pregnant.