THE GIST

- Just because a plastic product is labeled BPA-free doesn't mean its safe to put food or beverages in.

- It's possible to make plastics that don't contain hormone-disrupting chemicals, but it's impossible for consumers to tell which ones are which.

- People can protect themselves by not heating plastic containers that they're planning to eat or drink out of.

The elimination of the chemical BPA from plastic baby bottles, water bottles and other types of food and beverage packaging has given many people a sense of control over the plastics in their lives and the potential health risks involved.

But a BPA-free label doesn't mean a product is harmless, suggests a new study. When scientists conducted lab tests on more than 20 top-brand baby bottles along with more than 450 plastic food and beverage-packages, virtually all leached chemicals that acted like the hormone estrogen, even though many were free of BPA.

The new study, along with other work, suggests that the public's attention on BPA has been misguided. It now looks like there are thousands of possible chemicals in all sorts of plastics that act just like BPA. Called endocrine disruptors, these chemicals falsely tell the body's cells that the hormone estrogen is around, potentially causing all sorts of troubling developmental and reproductive consequences.

NEWS: Food Packaging Harbors Harmful Chemicals

"Baby bottles, plastic bags, plastic wrap, clamshell food containers, stand-up pouches: Just about anything you can think of that's made of plastic that food or beverages are wrapped up in, we found this activity," said study author Stuart Yaniger, vice president of research and product development at PlastiPure, a technology company that works on developing safe plastics but gets most of its funding from government agencies. "It was shocking to us."

"The message is not anti-plastic," he said, adding that it is very easy to make plastic without estrogenic properties. "Plastics are good, but they can be made safer."

Because of its shape and size, BPA manages to fit into the receptors in our bodies that recognize estrogen, kind of like a counterfeit key fitting into a loose lock. Estrogen is a key hormone in the development of young bodies and reproductive systems, which is why the chemical has been banished from baby products in many places. But if BPA can fool estrogen receptors so easily, scientists have long suspected that many other chemicals probably do the same thing.

As part of a systematic look into plastic consumer products that might harbor such endocrine disruptors, Yaniger and colleagues bought hundreds of plastic food and beverage containers at Target, Wal-Mart, Trader Joe's, Whole Foods and other major retailers. Their purchases included all categories of plastic -- including rigid containers, flexible wraps, deli containers and plastic bags. Some contained food. Some were empty.

Some plastic containers are safe, others aren't. And there's currently no way to know which are which. iStockPhoto

The researchers cut each item into pieces, put them into liquids that simulated foods and drinks and then subjected the pieces to stresses that mimic normal use, such as microwaves, boiling water and ultraviolet light. Finally, they applied the resulting solutions to a certain kind of breast cancer cell that multiplies rapidly when exposed to estrogenic chemicals.

Results showed that more than 90 percent of the products leached estrogenic chemicals before they were even put through stresses, the team reported this month in the journal Environmental Health Perspectives. After being stressed, nearly all of the plastics showed estrogenic activity when applied to the cancer cells.

The researchers didn't analyze the solutions to see exactly which chemicals might be the culprits. But the paper pointed out that some of the chemicals that are used to replace BPA have been shown to have even more estrogenic activity than BPA does.

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"This is certainly very startling and unexpected," said Arnold Schecter, a public health physician at the University of Texas School of Public Health in Dallas, who has published a series of studies on chemicals in our food supply -- many of which point to packaging as the main source of those chemicals.

Still, it is too soon to panic or banish all plastic from your life, said Schecter, who offered some caveats about the new work. It was a lab study, for one thing, so it will be important to see if other researchers can replicate the findings. It's also not yet clear what doses of chemicals could be expected actually get into people and what the real-world health implications might be.

Plenty of previous research has already shown that chemicals can leach out of plastic that is heated or otherwise stressed, added Linda Birnbaum, director of the National Institute of Environmental Health Sciences of the National Institutes of Health, and the National Toxicology Program in Research Triangle Park, N.C. The new work simply emphasizes the point that different isn't always better.

"When we move to alternatives," she said, "I think it's important that we test the alternatives to make sure we're not going to do the same thing or something worse than the compound we're removing."

For now, it is literally impossible for consumers to know which plastics might contain hormone-disrupting chemicals, so the old advice holds: Avoid heating plastics, leaving them in the sun, putting hot materials in them or putting them through other stresses if you're planning to eat or drink their contents.

Perhaps the best thing consumers can do, Yaniger said, is to put the pressure on businesses, just like they did with BPA. Instead of BPA-free, his hope is for future labels to be marked EA-free to signal a lack of all kinds of estrogenic activity.

"We recommend," he said, "that people go to retailers and manufacturers and ask them if they have tested these things for estrogenic activity and if they can provide EA-free packaging."