It's a chemical that has never been proven to cause health problems in humans in low doses. And it's one that the U.S. Food and Drug Administration has said is safe.
But an announcement last Wednesday by a research and advocacy group that the chemical Bisphenol-A was found in the inner lining of infant formula cans has a number of public health experts worried that babies consuming the formula could experience long-term developmental effects.
Bisphenol-A, or BPA for short, is a chemical mostly used in the production of certain types of plastics and resins used to coat metal. Because the chemical is so widely used, about 93 percent of people in the United States show signs of exposure to it, according to the Centers for Disease Control and Prevention.
No human study has ever shown that this level of exposure causes harm. But the Environmental Working Group raised a red flag Monday with a report that the chemical was found in the inner linings of infant formula cans — possibly increasing babies' BPA exposure.
Some public health experts stopped short of labeling the chemical a definite threat — though they noted the matter still warrants investigation.
"While no one knows for sure, the better science right now is on the side of concern, rather than reassurance," said Dr. Alan Ducatman, chair of community medicine at the West Virginia University School of Medicine in Morgantown.
But some are more adamant in their concerns.
"Those of us who do research on brain and behavioral development believe the public needs to be concerned," said Dr. Bernard Weiss, professor in the department of environmental medicine at the University of Rochester School of Medicine and Dentistry.
Part of the problem, Weiss said, is that the FDA is "behind current science and relies on old criteria." The approaches currently used are not adequate to determine whether a real threat exists, he says.
Frederick vom Saal, curators' professor at the University of Missouri Division of Biological Sciences in Columbia, agreed.
"Current statements by the FDA that BPA is safe are reminiscent of the response of the FDA to new findings concerning Vioxx, which were ignored by FDA officials until a whistle-blower went public that the FDA was unwilling to acknowledge that there was evidence that Vioxx posed a significant threat to human health," he said.
But food manufacturers, who admit to using the chemical to line cans, maintain that studies have thus far shown that exposure to the chemical at certain levels is safe. In fact, a summary review of several independent panels' conclusions, supported by the American Council on Science and Health, suggests any risks are small.
"It is … very unlikely that humans, including infants, will suffer any adverse consequences, including endocrine-related effects, from current exposures to BPA in food, drink, or other consumer products," the review concludes.
But it is known through animal studies that at certain levels, the chemical mimics hormones such as estrogen — a quality that some suggest may affect on the development of children who are exposed to it.
"BPA acts like an estrogen, and infants are being exposed to this hormonelike chemical at a particularly sensitive time, when estrogen-dependent development is occurring rapidly," said Dr. Shanna Swan, director of the Center for Reproductive Epidemiology at the University of Rochester School of Medicine and Dentistry in New York.
"The consensus of a group of scientists recently invited to participate in an NIH/EPA sponsored conference was that BPA, at levels currently found in people in the USA, has the potential to pose a threat to human health, and that this risk is greatest for the fetus and young infant."
Larry Glickman, section head of clinical epidemiology at Purdue University's School of Veterinary Medicine in West Lafayette, Ind., said animal studies he has conducted also suggest the possibility of other effects of BPA exposure.
In 2004, Glickman and his colleague Dr. Charlene Edinboro warned the FDA about the potential dangers of the BPA lining in food cans. Their study involved cats, not humans. But what they found was that an increase in the use of cat food in BPA-lined cans coincided with a dramatic spike in hyperthyroidism in cats.
They also found that kittens fed from these cans had a 4.5 times greater risk of hyperthyroidism later in life.
"As an epidemiologist and a consumer, I think parents should be very alarmed by this finding," he said. "Based on our findings, we suggested that cat owners limit the feeding of foods packaged in lined food cans. It seems like this recommendation should be extended to human foods, especially for babies and young children."
Still, Dr. John Spangler, professor of family medicine at Wake Forest University School of Medicine in Winston-Salem, N.C., noted that there is a big difference between how animals and humans are affected by the chemical.
"Low-dose animal studies have been reassuring," he said, adding that humans may metabolize BPA more rapidly than many animals. "This means that peoples' bodies would be exposed to the chemical for a shorter period of time than would the animals', implying that rodent studies might overestimate harm to humans."
But because the health of children is the issue at hand, Spangler added, consumers will be likely to react to any risk.
"These issues also keep surfacing because children, as a group, are exceptionally sensitive to environmental toxins," Spangler said. "One can reasonably ask: 'If there is any level of risk, and if a chemical alternative can be found that is safer, should children ever be exposed to BPA?'"
"As an epidemiologist, I would say the likelihood of risk to children is very small. As a parent, I would say that I want BPA-free food cans for my family."
Swan agreed, noting that for the time being, concerned parents can take steps to ensure that their children's exposure to BPA is minimal.
"I would recommend that mothers breast-feed whenever possible," she said. "If this is not possible, I would suggest they use powdered formula, reconstituted with filtered water, and feed this to their baby in glass or BPA-free bottles."
"While it may take time to fully understand the health implications of these exposures, parents who can make these changes are likely to reduce risk and will not increase harm."