A study published Aug. 28 in the scientific journal Chemistry & Biology gives no definitive answers about the role of bisphenol A in breast cancer, but researchers believe they have discovered a biological mechanism by which BPA concentrates in tumor cells.
While the study notes questions remain about whether the results in animal models are accurate and whether the results can be extrapolated to humans, ``there seems to be a consensus that there is a potential for deleterious effects from exposure to BPA ... and further study is needed.''
In the past, some experts have assumed BPA might be harmless, since healthy cells don't absorb its metabolized form readily - but tumor cells can, according to the study conducted by biochemists and scientists at Indiana University and the University of California at Berkeley.
According to lead researcher biochemist Theodore Widlanski from Indiana University, the study does not show the process necessarily works the same in humans.
And Steve Hentges, executive director of the polycarbonate business unit of the American Plastics Council in Arlington, Va., said the study underscores the importance of not looking at the results of any one study ``in isolation.''
``The report is just not terribly relevant for human health because it doesn't tell you whether BPA causes anything in people,'' said Hengtes. ``To suggest that BPA causes cancer is impossible from this study.''
Hentges said that typical levels of BPA found in the human body are 1,000-10,000 times lower than the concentration levels used in the study. Widlanski said his group used high concentrations to simulate the cumulative effects of low BPA concentrations over the course of a human lifetime.
``We have only demonstrated a possible mechanism that explains what people have been speculating about for years,'' Widlanski said in a news release. ``It doesn't mean that your bottled water is any less safe today than it was yesterday. It just means that if it isn't safe, we might be able to explain why.''
Widlanski said he always has been a skeptic of claims that BPA causes or speeds the development of cancer and birth defects. ``All along we set out to show the opposite - that BPA is not harmful. If any of the answers to our questions had been `no,' then we would have concluded BPA was not dangerous. But we can't do that, or we can't do it yet.''
Governmental bodies globally - the German Federal Institute for Risk Assessment, the U.S. Food and Drug Administration, Health Canada, the Japanese Ministry of the Environment and the U.S. Consumer Product Safety Commission - all have deemed BPA not harmful in the past three years.
In addition, an evaluation of more than 70 animal studies published in the peer-reviewed journal Critical Reviews in Toxicology said in February that the weight of evidence ``does not support the hypothesis that low doses of BPA adversely affect human reproductive and development health.''
Despite that, a ban on the sale, manufacture and distribution of polycarbonate baby bottles containing BPA is scheduled to go into effect Dec. 1 in San Francisco - the first ban of its type in the U.S. The ban also will cover pacifiers, toys and raincoats that contain phthalates and are intended for children under the age of 3.
About 6 billion pounds of BPA are produced globally, with about 25 percent manufactured in the U.S. In addition to toys, hard plastic baby bottles and pacifiers, BPA is used to make CDs, DVDs, electrical and electronic equipment, sports safety equipment including bike helmets, reusable food-storage and drink containers. It also is used to produce epoxy resins for dental sealants and as protective liners on metal cans to protect food from contamination.
A recent U.S. Center for Disease Control and Prevention study found trace amounts of BPA in 95 percent of urine samples collected from American adults.