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.
Frederick vom Saal, a biology professor at the University of Missouri-Columbia and one of the leading BPA researchers in the country, would go even further. He believes BPA should be banned from all products that might end up passing it along to people. "If it's hard and clear and doesn't say 'No BPA,' don't use it."
In studies of laboratory animals, Vom Saal says, BPA changes play behavior, weakens gender differences, decreases sperm count, stimulates prostate cancer and causes ADHD symptoms.
"All of this is occurring at exposures in animals that lead to blood levels that I guarantee are below what are in your body," he says. "No level has ever been found in animal experiments that doesn't cause harm."
And though most BPA research so far has been done with animals, a recent laboratory study found that it can encourage the growth of human breast cancer cells.
Babies and young children are most at risk from BPA, Vom Saal says, because once it enters their system, their bodies aren't good at getting it out. Maybe adults can metabolize and excrete BPA very quickly, but there's no question, he says, that babies can't do the same. "BPA has a very slow clearance in babies."
He adds: "There are alternatives to everything made from BPA."
These include glass baby bottles instead of polycarbonate ones -- the Glass Packaging Institute recently reported a surge in demand for these -- and natural resin for lining cans instead of epoxy. Japanese manufacturers started using natural resin in 1997, and two years later a study found that BPA levels had gone down significantly.
When Steven Hentges looks at the same BPA research as Vom Saal, he sees a very different picture. As executive director of the polycarbonate-BPA global group of the American Chemistry Council, which represents more than 100 companies, Hentges maintains, "There's no reason for the public to be alarmed. . . . People should make their food choices based on nutrition, not on packaging."
Major reviews of the scientific literature "consistently support the conclusion that there's no risk from BPA," he says, adding that the Food and Drug Administration considers BPA safe.
How to avoid BPA
So what to do?
Mel Suffet, a public health professor and environmental chemist at UCLA, doesn't know for sure how harmful BPA is or isn't. But he has no trouble figuring out what to do about it. "Why use something with a potential danger?" he asks. "It's kind of silly. Better safe than sorry."
Here are several ways to reduce exposure to BPA, as suggested by the National Toxicology Program:
* Avoid putting polycarbonate plastic food containers in the microwave or dishwasher. (By that token, you might also want to avoid putting hot food or liquid into polycarbonate plastic containers.) Heat makes BPA leach out much faster than it does otherwise.
Note: Most (but not all) plastics marked with a No. 7 recycling code are polycarbonates and therefore contain BPA.
* Eat fewer canned foods.
* Use glass, porcelain or stainless steel containers when possible, especially for hot food or drinks.
* Don't use polycarbonate baby bottles.