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Next, an update on the plastic additive known as bisphenol-A, or BPA. Government scientists have spent several years trying to figure out whether BPA in food poses a risk to consumers. Well, now those scientists say they've found little to suggest that the chemical is harming us.

NPR's Jon Hamilton reports.

JON HAMIILTON, BYLINE: Scientists agree that in large doses, BPA can act a bit like the hormone estrogen. But there's been a lot of debate about whether the tiny amounts found in people have the potential to cause problems.

Daniel Doerge, a research chemist with the Food and Drug Administration, says it's an important question because the chemical leaches out of so many products, including plastic water bottles and food containers.

DANIEL DOERGE: Nearly everyone in the U.S. will have traces of BPA in their urine, indicating this low level of exposure through food.

HAMIILTON: So Doerge and his colleagues at FDA's National Center for Toxicological Research have been working with scientists from the National Toxicology Program at the NIH, to see if there are any effects from this low-level exposure. In a new study, published in the journal Toxicological Sciences, the team exposed rats to BPA. The exposure began a few days after conception and continued through sexual maturity at 90 days. Some rats got a little BPA. Others got a lot.

Doerge says even the lowest amount was much greater than the amount a typical American gets through their diet.

DOERGE: It's about 70 times higher at this lowest dose. So it's, you know, millions of times higher at the highest dose.

HAMIILTON: So what did you find?

DOERGE: Not much.

HAMIILTON: Doerge says even when rats got more than 70,000 times what a typical American ingests, there was no change in body weight or reproductive organs or hormone levels.

DOERGE: In the low-dose range, there really were no biologically significant changes observed at all. It was only at the two highest doses where there were effects on reproductive tissues and other endpoints.

HAMIILTON: It took millions of times the dose consumers get to produce effects similar to those of the body's own sex hormones. To double check those results, the scientists looked at how BPA was interacting with estrogen receptors, the part of a cell that usually responds to estrogen. And once again, it was only the highest doses that produced interactions. The results bolster previous studies by government researchers, showing that people's exposure to BPA is lower than previously estimated. They also found that the human body is really good at inactivating and eliminating BPA.

So what does all this mean for consumers? Doerge puts it this way.

DOERGE: The results both support and extend the conclusion from the U.S. Food and Drug Administration that BPA is safe as currently used. And I should point out that a similar conclusion was just recently reached by the European Food Safety Authority.

HAMIILTON: The results are at odds with some smaller and less rigorous academic studies. And some of the scientists who did those studies have already called the new government research flawed. They say it failed to look at things like brain development.

David Ropeik, a Harvard instructor and consultant in risk perception, says that sort of response is pretty typical in the debate over BPA and other hormone-like chemicals known as endocrine disruptors.

DAVID ROPEIK: The endocrine disruption issue has evoked some of the most visceral and ugly attacks among scientists of any scientific issue recently.

HAMIILTON: Ropeik says a recent experience in Europe shows how these attacks often ignore the science underlying regulatory decisions.

ROPEIK: The European Food Safety Administration did what the FDA did: reviewed all the science and said at the doses we get it, BPA is probably not the risk that some people fear. At which point, the endocrine disruption movement said: Oh, my God, they're all corrupt. They're all taking corporate money.

HAMIILTON: Ropeik says that sort of allegation may undermine trust in regulatory agencies and their scientists. But it doesn't help consumers understand what chemicals like BPA are actually doing in the body.

Jon Hamilton, NPR News.

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