Clearly concerning: do common plastics and resins carry risks?

Science News,  Sept 29, 2007  by Janet Raloff

• E-mail
• Print
• Link

It's hard to avoid bisphenol A. One of the highest-volume chemicals in commercial production, it's the starting material used to make polycarbonate plastics. Those are the hard, clear plastics used in baby bottles, flatware, watercooler bottles, and the work bowls of food processors. Bisphenol A (BPA) also serves as an essential ingredient of epoxy resins used to line food and beverage cans and even to seal cavity-prone teeth.

But BPA doesn't stay put. It inevitably leaches into foods and people's mouths, such that traces of the chemical now show up in everyone's body.

[ILLUSTRATION OMITTED]

The universal presence of BPA has raised concerns because hundreds of animal studies have shown that this largely unregulated pollutant can tinker with the development and function of a wide range of tissues. These studies show, among other effects, that BPA can alter rodents' and other lab animals' sex-specific behaviors, perturb developmentally important hormones, boost fat cell numbers and their accumulation of lipids, foster precancerous changes in cells, and induce insulin resistance, a harbinger of diabetes.

If all of this happens in animals, can any of it happen in people too?

That's what the National Institute of Environmental Health Sciences decided to investigate, explains Jerrold J. Heindel, who works at the institute in Research Triangle Park, N.C. Two years ago, its National Toxicology Program (NTP) recruited two panels of experts to review masses of data on BPA'S reproductive and developmental effects. Last month, these panels issued reports offering different--and in some ways conflicting--assessments. One panel found many areas of concern. The other turned up few.

Ultimately, NTP will issue a single report that integrates conclusions from both panels, along with any new information on BPA that comes to light during the next few months. That report probably won't emerge for at least a year, says the institutes Michael D. Shelby, whose office will prepare the final document.

In the meantime, how worried should consumers be?

Previous evaluations "support the conclusion that BPA is not a risk to human health at the extremely low levels to which consumers might be exposed," according to a statement issued last month by the American Chemistry Council, a chemical-industry group based in Arlington, Va. It interpreted a recent report on BPA by the European Food Safety Authority as indicating that "consumers are not at risk from use of products made from BPA."

Such reassurances don't satisfy a number of BPA researchers, however--among them Randy Jirtle of Duke University in Durham, N.C. He recently published a rodent study showing that fetal BPA exposure can reprogram lifelong gene activity in the agouti breed of mice and even change the animals' coat colors (SN: 8/11/07, p. 84). Those data alone prompt Jirtle to say that "if I was a woman who was pregnant--or thinking about becoming pregnant--I would try hard to avoid exposure to BPA."

The chasm between such opinions explains why NTP'S judgment is so eagerly awaited. Moreover, Heindel says, it emphasizes why human studies that can confirm or refute BPA effects seen in animals and test tubes must become a research priority.

GLASS HALF EMPTY Ample evidence exists that BPA can harm lab animals at concentrations below those already occurring in most people. That was the primary conclusion of a consensus statement published in the August-September Reproductive Toxicology by 38 scientists on one of the two NTP panels. Several additional scientists on the panel declined to sign the statement because they work for government agencies that didn't want them weighing in officially or because they professed inadequate expertise on certain topics, says Heindel.

He commissioned the group to evaluate the strength of data from more than 700 BPA studies. Participants met last fall in Chapel Hill, N.C., to review their findings and identify human-health concerns about which they were "confident" and ones they deemed "likely."

The panel labeled as "confident" its assessment that BPA at low doses has had negative effects on experimental animals.

For example, the panel concluded that BPA exposure in the womb earl permanently alter genes of animals, impair the function of organs in ways that persist into adulthood, and trigger brain, behavioral, and reproductive effects, including diminished sperm production. Effects deemed likely included a heightened sensitivity to carcinogens, impaired immunity, and diminished insulin sensitivity.

The scientists also expressed confidence that many of these effects can be explained by data from test-tube studies of the chemical's properties.

Although the panel didn't officially put the "confident" or the "likely" label on any human effects of BPA, "the consensus was that there is no reason to think that effects that occur in animals in response to low doses of BPA would not also occur in humans," says participant Frederick S. vom Saal of the University of Missouri in Columbia. Although his and others' studies have identified an animal's most critical windows of susceptibility to harm as its time in the womb and shortly after birth, he notes that the scientists agreed that BPA exposures even in adult animals can trigger adverse effects.