MICHELE NORRIS, host:
Many of you have been clearing your house of baby bottles and other plastic products because they're made with the chemical BPA. Research has shown that BPA can act like the hormone estrogen, at least in mice and in rats.
Now, as NPR's Jon Hamilton reports, a new study finds that even plastics without BPA can release estrogen-like chemicals.
JON HAMILTON: Before you toss out your Tupperware, it's worth noting that scientists still don't know whether people are harmed by any of the chemicals coming from plastics. It's just not clear. And the new study doesn't look at health risks. It simply asks whether common plastic products release estrogen-like chemicals other than BPA.
That's something George Bittner, a biologist at the University of Texas in Austin, had been wondering for a long time. So he sent a research team to stores, including Wal-Mart and Whole Foods. Their mission: buy a whole bunch of stuff made of plastic, the kind of stuff that might come in contact with food.
Mr. GEORGE BITTNER (Biologist, University of Texas at Austin): Baby bottles, deli packaging, flexible bags.
HAMILTON: The team came back with more than 450 products. Then CertiChem, a testing company that Bittner founded, chopped up pieces of each product and soaked them in either salt water or alcohol to see what leeched out. Bittner says the tests made one thing clear.
Mr. BITTNER: Most plastic products on the market today release chemicals having easily detectible estrogenic activity.
HAMILTON: Estrogenic activity means they act like estrogen. Bittner says about 70 percent of the stuff the lab tested released these chemicals, and Bittner says that was before they exposed the stuff to real-world conditions: simulated sunlight, dishwashing and microwaving.
Mr. BITTNER: Then, you greatly increase the probability that you're going to get chemicals having estrogenic activity released, in fact, maybe somewhere between 95 to 98 percent.
HAMILTON: But what about all those things marketed as BPA-free - you know, dog bowls, bento boxes?
Mr. BITTNER: In particular, we've concentrated on baby bottles and water bottles. We've tested them and all of them released chemicals having estrogenic activity.
HAMILTON: Sometimes even more than products known to contain BPA. The testing didn't show which chemicals are to blame. That's likely to be frustrating to manufacturers, but Bittner says consumers should be encouraged that at least some plastic products had no estrogen-like activity. He says that shows it can be done.
Early reaction to the study was mixed. Some scientists wondered about the test's reliability. Others noted that wine and many vegetables also have estrogenic activity. And they note that Bittner has a financial interest in the testing lab and in a plastics company.
But groups that have warned about BPA in the past seemed to welcome the new research.
Ms. SONYA LUNDER (Senior Analyst, Environmental Working Group): This is really helpful because they took a look at very common products.
HAMILTON: Sonya Lunder is from the Environmental Working Group. She says the results suggest the concerns about plastics can't be solved by worried consumers at the checkout counter. It's a problem for government.
Ms. LUNDER: Regulatory agencies like the FDA need to study the effect of chemicals leeching out of plastic. We know the EPA first proposed its hormone disrupter screening program 15 years ago and has made virtually no progress.
HAMILTON: Lunder says that until there are more definitive answers, worried consumers can follow the old advice to avoid putting those baby bottles in dishwashers or microwaves.
Ms. LUNDER: See, we've long cautioned consumers to avoid extreme heat and cooling for plastics, to discard scratched and worn plastics, and we feel like this validates one of our many concerns.
HAMILTON: The new study appears in the online edition of the journal Environmental Health Perspectives.
Jon Hamilton, NPR News.