The plastics chemical bisphenol A, whose use has been restricted in Canada, may affect the behaviour of little girls, report researchers in a controversial study.
Girls exposed to higher levels of BPA while in the womb display more aggressive and hyperactive behaviours, according to the study published in the journal Environmental Health Perspectives.
Researchers, including a scientist from Simon Fraser University in British Columbia, measured the BPA levels in urine samples taken from 249 pregnant women in Cincinnati.
They measured the levels at 16 weeks pregnancy, at 26 weeks, and again when the women gave birth. The children's behavior was reported by the parents using a standardized questionnaire when the children were two years old.
Ninety-nine percent of the women had at least one urine sample with detectable levels of BPA, according to the study. They found that the daughters of women who had higher concentrations of BPA in their urine samples were more likely to have aggressive and hyperactive behaviors at age two than daughters of women with lower BPA levels.
"In other words, girls whose mothers had higher BPA exposure were more likely to act like boys than girls whose mothers had lower BPA levels, especially if the exposure was seen earlier in pregnancy," said the study's lead author Joe Braun, a doctoral student in epidemiology at the University of North Carolina Gillings School of Global Public Health.
Strangely, the study found no significant effect of maternal levels on BPA on boys. The researchers say they don't know why girls would be affected differently than boys.
Bruce Lanphear, the study's senior author and a Simon Fraser University professor of children's environmental health, said the chemical concentrations between 13 and 16 weeks of pregnancy were most strongly associated with behaviour problems in the girls.
The girls will be tested again when they're five years old, an age when children's behaviours tend to be more stable.
The researchers also said they don't what biological mechanism might be leading to an increase in aggressive behaviors after BPA exposure. But previous studies in mice have found similar results in the offspring of mothers with high BPA exposure during pregnancy.
In previous research, bisphenol A has been shown to affect hormone levels and has been linked to reproductive problems.
However, the American Chemistry Council, which represents the chemicals industry, said the research had "significant limitations" in its study design.
Steven Hentges, executive director of the polycarbonate/BPA global group at the Council noted the study was small, relied on parents' assessment of their children's behaviour and failed to show cause and effect, only associations.
"The results of this preliminary, and severely limited study cannot be considered meaningful for human health unless the findings are replicated in a more robust study," Hentges said in a statement Tuesday.
Last October, Canada became the first country in the world to ban baby bottles that contain BPA, which is used in hard, clear polycarbonate plastics as well as the epoxy linings of metal food and beverage cans.
Research has shown that the chemical can leach into food and beverages from the containers. Previous studies suggest that more than 90 per cent of people in the United States have detectable levels of BPA in their urine.
