WASHINGTON — With scientists at odds over the safety of a chemical found in plastic baby bottles, metal cans and other food packaging, consumers got minimal guidance Tuesday about how to protect themselves.
At a scientific hearing, the Food and Drug Administration defended its assessment that bisphenol A— or BPA—is safe, even as the first major study of health effects in people linked it with possible risks for heart disease and diabetes. The debate could drag on for years.
‘‘Right now, our tentative conclusion is that it’s safe, so we’re not recommending any change in habits,’’ said Laura Tarantino, head of the FDA’s office of food additive safety. But she acknowledged, ‘‘there are a number of things people can do to lower their exposure.’’
For example, consumers can avoid plastic containers imprinted with the recycling number ’7,’ as many of those contain BPA. Or, said Tarantino, they can avoid warming food in such containers, as heat helps to release the chemical.
More than 90 percent of Americans have traces of BPA in their bodies, but the FDA says the levels of exposure are too low to pose a health risk, even for infants and children.
However, a study released Tuesday by the Journal of the American Medical Association suggested a new concern about BPA. Because of the possible public health implications, the results ‘‘deserve scientific follow-up,’’ the study authors said. Using a health survey of nearly 1,500 adults, they found that those exposed to higher amounts of BPA were more likely to report having heart disease and diabetes.
But the study is preliminary, far from proof that the chemical caused the health problems. Two Dartmouth College analysts of medical research said it raises questions but provides no answers about whether the ubiquitous chemical is harmful.
FDA officials said they are not dismissing such findings, and conceded that further research is needed. ‘‘We recognize the need to resolve the concerning questions that have been raised,’’ said Tarantino. But the FDA is arguing that the studies with rats and mice it relied on for its assessment are more thorough than some of the human research that has raised doubts.
The FDA has asked an outside panel for a second opinion on its BPA safety assessment, and the medical journal article was released to coincide with the advisers’ hearing.
The FDA has the power to limit use of BPA in food containers and medical devices but last month released its internal report concluding that BPA exposure is not enough to warrant action.
Since then, another government agency released a separate report concluding that risks to people, in particular to infants and children, cannot be ruled out.
Past animal studies have suggested reproductive and hormone-related problems from BPA. The JAMA study is the largest to examine possible BPA effects in people and the first suggesting a direct link to heart disease, said scientists Frederick vom Saal and John Peterson Myers, both longtime critics of the chemical.
Still, they said more rigorous studies are needed to confirm the results.
Vom Saal is a biological sciences professor at University of Missouri who has served as an expert witness and consultant on BPA litigation. Myers is chief scientist at Environmental Health Sciences, a Charlottesville, Va., nonprofit group. They wrote an editorial accompanying the JAMA study.
BPA is used in hardened plastics in a wide range of consumer goods including food containers, eyeglass lenses and compact discs. Many scientists believe it can act like the hormone estrogen, and animal studies have linked it with breast, prostate and reproductive system problems and some cancers.
Researchers from Britain and the University of Iowa examined a U.S. government health survey of 1,455 American adults who gave urine samples in 2003-04 and reported whether they had any of several common diseases.
Participants were divided into four groups based on BPA urine amounts; more than 90 percent had detectable BPA in their urine.
A total of 79 had heart attacks, chest pain or other types of cardiovascular disease and 136 had diabetes. There were more than twice as many people with heart disease or diabetes in the highest BPA group than in the lowest BPA group. The study showed no connection between BPA and other ailments, including cancer.
No one in the study had BPA urine amounts showing higher than recommended exposure levels, said co-author Dr. David Melzer, a University of Exeter researcher.
Drs. Lisa Schwartz and Steven Woloshin of the Dartmouth Institute for Health Policy and Clinical Practice said the study presents no clear information about what might have caused participants’ heart disease and diabetes.
‘‘Measuring who has disease and high BPA levels at a single point in time cannot tell you which comes first,’’ Schwartz said.
The study authors acknowledge that it’s impossible to rule out that people who already have heart disease or diabetes are somehow more vulnerable to having BPA show up in their urine.
The American Chemistry Council, an industry trade group, said the study is flawed, has substantial limitations and proves nothing.
But Dr. Ana Soto of Tufts University said the study raises enough concerns to warrant government action to limit BPA exposure.
‘‘We shouldn’t wait until further studies are done in order to act in protecting humans,’’ said Soto, who has called for more restrictions in the past.
An earlier lab experiment with human fat tissue found that BPA can interfere with a hormone involved in protecting against diabetes, heart disease and obesity. That study appeared online last month in Environmental Health Perspectives, a monthly journal published by the National Institutes of Health.
Government toxicology experts have also studied BPA and recently completed their own report based on earlier animal studies. They found no strong evidence of health hazards from BPA, but said there was ‘‘some concern’’ about possible effects on the brain in fetuses, infants and children.
Several states are considering restricting BPA use, some manufacturers have begun promoting BPA-free baby bottles, and some stores are phasing out baby products containing the chemical. The European Union has said that BPA-containing products are safe, but Canada’s government has proposed banning the sale of baby bottles with BPA as a precaution.