A new study suggests exposure to bisphenol-A  (BPA) is actually much greater than previously thought, and its authors urge the federal government to act quickly to regulate the chemical that is in baby bottles, food-storage containers and many household products.

The peer-reviewed study, published Sept. 20 in the online NIH journal Environmental Health Perspectives, also says BPA exposure is likely coming from many sources–including some  still unknown.

Researchers at the University of Missouri Division of Biological Sciences, Veterinary Medical Diagnostic Lab and the department of Biomedical Sciences, working with scientists at the University of California-Davis and Washington State University, co-authored the study.

One of the researchers, Frederick vom Saal, professor of biological sciences at the University of Missouri, said in a news release that the study “provides convincing evidence” that BPA is dangerous and that “further evidence of human harm should not be required for regulatory action to reduce human exposure to BPA.”

Connecticut, Massachusetts, Washington, New York and Oregon now have limits on BPA, particularly in products used by children, but the California legislature recently rejected a BPA ban.  Similar legislation has been proposed in Congress, where it is a distinctly partisan issue.  The effort by Sen. Dianne Feinstein (D-CA) to add a BPA ban to the Food Safety Modernization Act has been met with dogged resistance from Republicans. 

Two years ago Canada announced it would be the first country to ban plastic bottles made with BPA and recently took the first step toward making good on that promise – placing BPA on a toxic-substance list under the Canadian Environmental Protection Act, a move that should be final by November.

But the controversy over BPA has raged on in the United States, with one side dismissing a multitude of studies as flawed and arguing that the chemical is not only safe but beneficial, for myriad uses such as can liners, thermal paper and dental sealants.  Immediately after this latest research was published, some critics questioned the researchers’ impartiality and charged that the study was just another scare tactic.

Environmentalists and others who want BPA banned contend the chemical is an endocrine disrupter that may be a factor in infertility, certain cancers and immune disorders.

Julia Taylor, lead author of the new study and associate research professor at the University of Missouri, said, “For years, BPA manufacturers have argued that BPA is safe and have denied the validity of more than 200 studies that showed adverse health affects due to exposure in very low doses of BPA.”  But “we know that BPA leaches out of products that contain it, and that it acts like estrogen in the body.”

The research led by Taylor used BPA-exposed mice and monkeys and compared the findings with prior published data for women.  The researchers discovered that women, female monkeys and female mice metabolize the chemical in similar ways and argue for the validity of animal studies in assessing how BPA affects humans.

The researchers say estimates vary widely of just how much people are exposed to BPA daily and they question the commonly held belief that most exposure comes from food-storage containers or other plastic products. 

Pat Hunt, professor in the Washington State University School of Molecular Biosciences and one of the study’s co-authors, said, “We’ve assumed we’re getting BPA from ingestion of contaminated food and beverages.  This indicates there must be a lot of other ways in which we’re exposed to this chemical and we’re probably exposed to much higher levels than we have assumed.”

The U.S. Environmental Protection Agency, which last year rated the potential effects of low doses of BPA as “negligible” or “of some concern,” says daily exposure of up to 50 micrograms of BPA per kilogram of body weight is safe.  But the University of Missouri research suggests people are exposed to at least eight times that amount.

With nearly 8 billion pounds manufactured each year,  BPA is one of the highest-volume chemicals ever produced.  The Centers for Disease Control and Prevention estimate that the compound is present in more than 90 percent of the U.S. population.

Consumer skepticism about BPA has been building and so far has been more influential in limiting it than regulation.  Wal-Mart, Whole Foods and Sears are among the retailers who have promised to stop selling items like baby bottles and sippy cups made with BPA and customer complaints have prompted some manufacturers to switch to BPA-free materials.

The authors of the new study say that BPA is likely to be in so many things that the government should require the chemical industry to identify all products that contain it.