Are plastic's safety claims shatterproof?

The synthetic chemical bisphenol A has long been found in many household products, but it's just starting to become a household name.

Not to mention a hot topic in the scientific community.

"Papers about it are being published at the rate of about one a day," says John Bucher, associate director for the National Toxicology Program, an agency of the National Institutes of Health.

Produced in vast quantities every year -- more than 2 billion pounds in the United States, more than 6 billion pounds worldwide -- bisphenol A, or BPA, is the basic ingredient in hard, clear polycarbonate plastics (number 7 in the recycling code) and epoxy resins, which are used to make such things as water bottles and baby bottles and the corrosion-preventing lining of tin cans.

BPA-based products don't weigh much, don't cost much and don't break if you drop them on the floor. That's the good news.

The possibly bad news is that BPA doesn't always stay put. The chemical acts a lot like estrogen if it's introduced into the body -- and evidence now shows that this happens to just about everybody every day.

Especially at high temperatures in, say, microwave ovens or dishwashers, BPA can leach out of those cans and bottles -- and wind up inside the people who consume the contents. More than 90% of people 6 and older have detectable levels of BPA in their bodies, according to a 2003-04 survey conducted by the Centers for Disease Control and Prevention.

A draft report issued last month by the National Toxicology Program raised new red flags -- and consumer alarm -- about the potential harm BPA may do.

The report, based on a review of nearly 1,000 papers, expressed "some concern" that in fetuses, infants and children, typical human exposure may cause changes in behavior, in the brain, in the prostate and mammary glands, and in the age at which females reach puberty. Of the five possible levels of concern the report might have chosen -- from "serious" to "negligible" -- "some" is the third, or middle, level.

The concern was based on evidence from a number of studies with laboratory animals at BPA exposures similar to human exposures. About the same time that the toxicology program released its draft report, Health Canada, Canada's national public health department, released a report of its own calling BPA "a potentially harmful chemical" -- becoming the first regulatory body worldwide to do so. (The toxicology program in the United States is not a regulatory body.) The agency is on course to ban BPA in baby bottles if, after a 60-day period for comment, no one presents a good reason not to.