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Bisphenol A, the controversial chemical used to make plastic, lingers far longer in the bodies of babies who ingest it than in adults because they lack a crucial liver enzyme needed to break it down, according to researchers at the University of Guelph.

The finding prompted one of the researchers to recommend that parents try to make sure their babies have no exposure to bisphenol A, and that pregnant women minimize what they ingest to protect their developing fetuses.

Len Ritter, professor at the university's department of environmental biology and the study's lead author, said infants "do appear to have significantly greater levels ... up to 11 times higher [than adults] That's not trivial."

The study, published in Environmental Health Perspectives, is likely to put further pressure on Health Canada to step up its efforts to control bisphenol A (also known as BPA), a synthetic compound that has raised concerns because it mimics estrogen.

Bisphenol A is used to make polycarbonate and the linings of most food and beverage cans. It is also an additive in many types of plastic. Because it is not tightly bound in consumer packaging, trace amounts can leach into food and drinks.

Last year, the federal agency added the chemical to Canada's toxic-substances list and announced a ban on plastic baby bottles made from it, the first country in the world to take such actions.

Health Canada also said it wanted infant formula makers to minimize the amounts seeping out of can linings, but neither the companies nor the government have finalized control measures.

Health Canada said in a statement in response to questions from The Globe and Mail that it met last month with the U.S. Food and Drug Administration, infant formula makers and canning companies to develop a North American approach to the reduction of BPA in food products.

Health Canada believes pregnant women don't need to reduce their exposure, but said in the statement that pregnant or breastfeeding women with concerns can reduce exposure by using non-polycarbonate plastic containers to heat foods or using alternatives such as glass or stainless-steel containers.

Many researchers are worried that through exposure to BPA, people are getting what amounts to an extra dose of estrogen. Animal experiments have found the chemical is associated with hormonal conditions, such as earlier onset of sexual maturity in females, and breast cancer, particularly when exposure occurs during fetal or neonatal periods.

In the new study, Dr. Ritter used models based on animal and human experiments to estimate how long it would take babies to clear the chemical from their bodies, compared with adults, when both were given equivalent doses, adjusted for their differing body weights.

Adults have a well-developed capacity to metabolize BPA into a harmless form that is quickly excreted in urine. Dr. Ritter said this capacity isn't fully developed in newborns, allowing BPA to build up in their blood to 11 times what an adult would have.

Infants gradually gain the ability to detoxify BPA, and by three months would still have about double adult levels of the chemical, he said.

Researchers don't know precisely when infants gain a fully developed capacity to metabolize BPA.