BPA are more likely to be anxious, depressed and hyperactive at age 3, according to a study in today's Pediatrics.
Boys' behaviour was unaffected by BPA, the study says.
Scientists in recent years have linked BPA, or bisphenol A, to a wide variety of health problems, from breast cancer to diabetes.
BPA is found in countless consumer products, from plastic bottles to dental sealants, medical equipment, receipt paper and the linings of metal food and drink cans.
Virtually everyone is exposed to BPA. Authors of the new study found BPA in the urine of more than 97% of the 240 pregnant women studied, as well as 97% of their children.
Being exposed to high BPA levels after birth didn't appear to affect behavior, says study author, Joe Braun, a research fellow at the Harvard School of Public Health.
That could be because BPA, like lead and other toxins, causes the greatest harm before birth, when the fetal brain is developing, says pediatrician Philip Landrigan, a professor at New York's Mount Sinai School of Medicine, who was not involved in the new study. "Parents should be concerned about these findings," Landrigan says.
About 12% of boys and 6% of girls have been diagnosed with ADHD, or attention deficit hyperactivity disorder, according to the U.S. Census Bureau.
Girls are about twice as likely as boys to be depressed or anxious, Braun says. Few kids in the study were depressed or anxious enough to meet the requirements for a clinical diagnosis, says Braun, noting that only 2% to 3% of children this age are diagnosed with these problems.
But Braun says the differences in behaviour between children in his study are comparable to the effects seen with high exposure to toxins such as lead, mercury and pesticides.
Steven Hentges, a spokesman for the American Chemistry Council, says the study's "conclusions are of unknown relevance to public health." He notes that regulators in Europe, Japan and the USA "have … reviewed hundreds of studies on BPA and repeatedly supported the continued safe use of BPA."
Yet Landrigan says studies like this are precisely why the FDA needs to act to protect people from BPA. In the meantime, he says pregnant women should try to reduce their exposure.