BPA makes plastic hard and shatterproof. (CBC)

U.S. government toxicology experts on Wednesday expressed "some concern" over bisphenol A, a chemical used in plastic baby bottles, saying it may be linked to health and developmental problems in children.

BPA makes plastic hard and shatterproof. The chemical is used to line cans and is found in water bottles and baby bottles, as well as consumer products like CDs.

The final report by the Department of Health and Human Services' National Toxicology Program does not say BPA should be banned.

"More research is clearly needed to understand exactly how these findings relate to human health and development, but at this point we can't dismiss the possibility that the effects we're seeing in animals may occur in humans," said Michael Shelby, director of the department's Center for the Evaluation of Risks to Human Reproduction, which conducted the review.

"If parents are concerned, they can make the personal choice to reduce exposures of their infants and children to BPA," he added in a release.

Earlier this month, scientists with the U.S. Food and Drug Administration said the trace amounts of bisphenol A that leach out of food containers are not a threat to infants or adults.

The report uses a five-point scale from highest to lowest for current human exposures to bisphenol A:

1. Serious concern.
2. Concern.
3. Some concern.
4. Minimal concern.
5. Negligible concern.

The report's authors said they had "some concern" for effects on the brain, behaviour and prostate gland in fetuses, infants and children.

There was "minimal concern" for effects on the mammary gland and an earlier age for puberty for females.

Whether exposure of pregnant women to bisphenol A will result in deaths of fetuses or newborns, birth defects, reduced birth weight and growth was deemed a "negligible concern."

The report also gave a "negligible concern" ranking on whether bisphenol A will cause reproductive effects in adults exposed outside the workplace. For workers exposed to higher levels at work, there is "minimal concern."

Bottles shelved

"We have concluded that the possibility that BPA may affect human development cannot be dismissed," said John Bucher, the toxicology program's associate director.

The report's conclusions are based on laboratory studies of animals, as well as a review of scientific literature and comments made by the public and peer reviewers to a draft report that was released in April.

Also in April, Canada announced a public consultation on banning the import and sale of polycarbonate baby bottles containing bisphenol A. Comments are now under review for publication on Oct. 18, Health Canada said.

Many retailers in Canada have already removed bottles and other products containing BPA from their shelves because of public concern.

The U.S. Food and Drug Administration is meeting on Sept. 16 to consider its own analysis of BPA in conjunction with Wednesday's report by the National Toxicology Program.

More effects on animals

Meanwhile, evidence of potential health effects of BPA from animal studies continues to accumulate.

In a study set to be published in this week's issue of the Proceedings of the National Academy of Sciences, Canadian and U.S. researchers concluded low doses of BPA hinder the formation of synapses in the brain that allow neurons to communicate with one another, and are important for how we interpret and remember experiences.

Biomedical science Prof. Neil MacLusky of the University of Guelph and his colleagues at Yale University used doses of BPA declared safe for daily consumption by the U.S. Environmental Protection Agency to mimic continuous environmental exposure to the chemical.

African Green monkeys exposed to BPA for a month showed less synapse density in their brains, the researchers found.

It's thought that BPA may impair how estrogen induces synapse formation, MacLusky said.

The American Chemistry Council, which represents plastics manufacturers, said studies from animals provide "limited and inconclusive evidence."