MONDAY, Oct. 24, 2011 (HealthDay News) -- Girls who are exposed to high levels of bisphenol A (BPA) while in their mother's womb may be more likely to show signs of behavioral and emotional problems as toddlers, new research finds.
BPA is a chemical widely used in plastic and other household products. In the study, 244 mothers gave urine samples that were tested for BPA while they were pregnant and shortly after giving birth. Their children's urine was tested for BPA at ages 1, 2 and 3.
The vast majority of had some level of BPA in their urine, including 85 percent of moms and more than 96 percent of the children.
Researchers found no connection between girls' or boys' levels of BPA in early childhood and their behavior. Nor did they find a link between the mothers' BPA levels during pregnancy and boys' behavior.
However, researchers did find that the higher the moms' BPA concentration levels during pregnancy, the more likely their daughters were to have higher scores on measures of anxiety, depression and hyperactivity, and poorer emotional control and inhibition at age 3.
None of the girls' behavior, which was described by their mothers in questionnaires, was out of the range of normal, noted study author Joe Braun, a research fellow in environmental health at Harvard School of Public Health.
"What we found was that the mothers' concentrations of BPA in urine during pregnancy were associated with behavioral problems in daughters at 3 years of age, but we didn't find this relation between mothers' BPA and the boys, and we also didn't observe any relationship between the child's BPA concentrations and behavioral problems," Braun said. "These results suggest that the girls may be more vulnerable to the effects of gestational BPA exposures and there is this unique window of brain development that is susceptible to BPA exposures."
The study is published in the Oct. 24 online edition of the journal Pediatrics.
BPA is used to make polycarbonate plastic (hard, clear plastic) and epoxy resin. While BPA is beginning to be phased out in the manufacture of baby bottles and other children's products, it's still widely used in many other applications, including electronic and medical equipment, cars, sports safety equipment, and food and drink containers.
Virtually everyone living in an industrialized nation is exposed to some amount of BPA, according to the study.
Most human exposure to BPA is believed to occur when the chemical leaches into food and drink from packaging, particularly from the liners of canned foods, experts say. Thermal receipts used in many cash registers are also a source of BPA.
In recent years, concern about the effects of BPA, particularly on fetuses and young children, have been growing. Animal studies have shown BPA can cause reproductive abnormalities to both males and females by disrupting the endocrine system. Other research has linked BPA to an increased risk of diabetes, cancer and heart arrhythmias.
Dr. Hugh Taylor, chief of the division of reproductive endocrinology and infertility at Yale University School of Medicine praised the new research, adding the caveat that the findings show an association, but not causality.
"This is an important study that follows BPA-exposed children to 3 years of age. It proves that the effects of BPA on behavior are long-lasting, and implies that these effects will be there for the life of the exposed individual," Taylor said. "BPA is a hormone-like chemical that interferes with estrogen action. The effects were more pronounced in girls; this is not surprising, as estrogens play an important role in brain development in both boys and girls, however, testosterone is converted to estrogen in the brain, so the boys likely had enough to protect against the BPA."
The fetus, he added, may be especially vulnerable to harmful chemicals.
"We are just starting to appreciate that exposures in the womb may have subtle lasting deleterious effects that are not immediately apparent at birth," Taylor said. "Behavior and reproduction are often affected by hormones in the environment and adverse effects in these areas are not apparent at birth."
Chemical industry representatives, however, said the study has "significant shortcomings" and that other research has found BPA does not cause ill health effects at typical exposure levels.
"The study released in Pediatrics has significant shortcomings in study design and the conclusions are of unknown relevance to public health," a statement released by the American Chemistry Council said. "The researchers themselves acknowledge that it had statistical deficiencies, including its small sample size and the potential for the results being due to chance alone."
For pregnant women worried about reducing exposure to BPA, experts advised avoiding canned foods, plastics that contain BPA and cash register receipts.
Braun and his team plan to continue following the children in the study to see if the symptoms of depression and anxiety seen in some girls develop into full-blown depressive or anxiety disorders as they get older.
The U.S. National Institute of Environmental Health Sciences has more on bisphenol A.