Waiting On Science To Say If Plastic Chemical Is Safe

The FDA has promised to reassess the safety of BPA - a widely used plastic additive that can act like estrogen in the body. Currently, the agency's position is that BPA exposure is too low to cause health effects, but some major studies of the chemical's safety are just beginning.

The Food and Drug Administration has quietly delayed its review of BPA, a widely used plastic additive that can act like the hormone estrogen in the body.

FDA officials had promised an updated position on BPA, or bisphenol A, by the end of November. Now it appears that any major change in the FDA's stance will wait until the agency sees results from a host of new government-funded studies.

Some of those results will be available in a few months. Others will take years.

BPA is used in polycarbonate bottles and in the lining of many food containers. The FDA's current position is that BPA exposure from these products is too low to cause health effects.

Disagreement About BPA Exposure And Effect

Studies of rodents show that large doses of BPA can cause abnormal sexual development. But there's bitter disagreement among scientists about whether the small doses most people are exposed to pose a risk.

Just a few months ago, the FDA seemed poised to act on BPA. In June, the FDA's new chief, Margaret Hamburg, promised that the agency would reconsider its earlier conclusion that BPA is safe. And in August, the FDA's Science Advisory Board held a public hearing that included testimony from many groups that called on the FDA to ban BPA from food and beverage containers.

Then in October, something happened that changed the regulatory landscape.

Missing Information

The National Institutes of Health announced it would spend $30 million on a whole new round of BPA studies. Moreover, the new studies would be designed to address perceived shortcomings in earlier research.

That put the FDA in an awkward position.

"You want to have all the information in front of you," says Sarah Vogel of the Johnson Family Foundation. "So I think that's a difficult issue that FDA is having to weigh."

Vogel is no FDA apologist. She's one of several dozen scientists who sent a letter to the agency this fall strongly urging it act without waiting for more research. Most of the letter's authors are academic researchers. And many have done animal studies suggesting BPA can cause developmental problems.

Existing Studies' Results Aren't Clear

But Vogel says these academic scientists have generally not conducted the sort of studies that government agencies use to assess risk.

"That community has been taking part in trying to build scientific consensus," she says, "which is slightly different than going and saying, 'OK, well, do we have a study that gives us a neat dose-response relationship? And did it follow good laboratory practice and can we then use it to set a regulatory guideline?' "

In fact, regulators around the world have found it very hard to draw conclusions from these academic studies.

That's because they typically require studies that meet a long list of criteria, says Wolfgang Dekant, a toxicologist at the University of Wuerzburg in Germany and a member of a panel that reviewed BPA research a few years ago for the European Food Safety Authority.

"Your study has to be reproducible; your effects have to be consistent; your statistics have to be correct; you have to use larger group sizes," Dekant says.

Many of the academic studies did not meet the standards, Dekant says. And scientists who repeated some of the studies were unable to get the same results.

In contrast, larger studies that met the standards found no risk from BPA, even with exposures hundreds of times higher than most people get, Dekant says.

BPA critics argued that some of those larger studies couldn't be trusted because they were funded by industry. But regulators in the European Union concluded that consumers are not at risk from products containing BPA.

Comparing Risks

In both the U.S. and Europe, regulators have been unsure how to interpret studies that injected BPA into laboratory animals.

They say that's because people are exposed to BPA primarily through food and beverages, which means the digestive system has a chance to remove most of the chemical before it reaches the bloodstream.

When researchers inject BPA, "you can see effects you can't get with oral administration," says Earl Gray, a scientist with the Environmental Protection Agency.

Gray says that's why he has used oral administration in his studies of pregnant rats.

In those studies, Gray gave some of the rats BPA and some the type of estrogen used in birth control pills. His studies used large groups of rats and a wide range of BPA and estrogen doses.

Gray's studies found that estrogen produced abnormalities in the rats' offspring . But with BPA, Gray says, "We didn't find any effects."

Copyright 2009 National Public Radio. To see more, visit http://www.npr.org/.

More in U.S. / World

Comments

blog comments powered by Disqus