By Brenda Goodman, MA
WebMD Health News
Reviewed by Arefa Cassoobhoy, MD, MPH
Feb. 3, 2015 -- Are goods labeled "BPA-free" healthier? Maybe not. Two new studies found that some chemicals replacing BPA in plastics, food packaging, and other products might also disrupt hormones, changing how the brain works and affecting fertility.
In the first study, scientists exposed growing zebra fish to very small amounts of BPA and its chemical cousin called bisphenol-S, or BPS. Zebra fish share 80% of their genes with humans and are often used as a model for human brain development. They are so well-studied that scientists can tell whether the fish are acting normally or not.
For example, in the fish exposed to BPA and BPS, scientists observed bursts of fast swimming and darting with quick turns, which they believe points to anxiety and hyperactivity. The fish that were introduced both chemicals also grew more brain cells called neurons during a critical stage of development, which may explain their behavior. And those exposed to BPS grew more neurons than those exposed to BPA.
In the second study, French researchers exposed small pieces of tissue taken from developing mouse and human testes to BPA and two of its replacements, BPS and bisphenol-F, or BPF. All the chemicals lowered the production of testosterone in these tissues, and BPS proved to be a more potent testosterone-blocker than BPA.
The American Chemistry Council, a trade group that represents companies that make and use BPA and BPS, says it's wrong to draw conclusions about human health from studies on animals and tissue samples.
The group says in a written statement that "it is well-known that humans, including pregnant women, efficiently convert BPA to a substance with no known biological activity and quickly eliminate it from the body."
It also says regulatory agencies in the U.S. and Europe have concluded that at the small amounts most people are exposed to, BPA is safe.
The council declined to comment on BPS, though.
For help understanding what all this means, WebMD spoke to Laura Vandenberg, PhD, an assistant professor of environmental health sciences at the University of Massachusetts, Amherst; Cassandra Kinch, a University of Calgary PhD candidate who led the zebra fish study; and Frederick vom Saal, a professor of biology at the University of Missouri who has been studying BPA since the 1970s.
Recent studies have suggested that bisphenol-S, which is sometimes used in plastics labeled "BPA-free," might have some of the same effects in the body as bisphenol-A. What's the concern?
Vandenberg: The concern is that these chemicals might mimic the actions of the hormone estrogen, disrupting development of the male and female reproductive tracts, the mammary gland, and the brain, among other things.
Even at very low doses, hormones -- or compounds that mimic or interfere with the actions of hormones -- can have very dramatic effects on development. We mostly consider fetuses, infants, and children to be the most sensitive to these compounds. … But more and more science suggests that adults, too, might be affected by them.
The FDA and its European equivalent, the European Food Safety Authority, or EFSA, have said that people are exposed to levels of these chemicals that are too low to harm health. Do you agree?
Kinch: The dose that we used [in the zebra fish study] is lower than what's found in the blood of babies still in the womb. It's the same dose that's found in the rivers around Alberta (in Canada). It's the equivalent of being 1,000-fold less than the limit for humans set by Health Canada and the U.S. EPA. And it's about 100-fold less than the new limit set by the EFSA.
I was extremely surprised that we found these effects at this very low dose. It's a dose you wouldn't even consider.
How is BPS different than BPA?
Vandenberg: Chemically, these compounds are very similar. BPS differs from BPA by one special chemical "group," but the overall "shapes" of these chemicals are quite similar. Even to a non-chemist like me, when you look at these compounds, you might think that they would have similar actions. One reason we worry about BPA is that its chemical "shape" allows it to bind to the estrogen receptor, and then act like estrogen in the body. Since BPS looks similar, it isn't a big leap to think that it also would act like estrogen -- and it does.
Vom Saal: BPS is just as bad or even worse than BPA. BPA may spend up to a month or so in the environment; it doesn't persist for decades like some other chemicals. BPS, on the other hand, sticks around -- for instance, if it gets into ocean water. It doesn't degrade. And it acts similar to estrogen (the scientific term is "estrogenic"). We have research we're going to be publishing showing that in human breast cells, it's just slightly less estrogenic than BPA. In other systems it can have equal potency to BPA and to other estrogens.
Why do manufacturers add bisphenols to plastics?
Vandenberg: BPA makes pretty awesome plastic! You want to have shatter-resistant plastic that is also see-through for products like your car's windshield. … Similarly, the BPA epoxy resins used to line cans have great properties for separating food from the can itself, preventing unwanted interactions between the metal can and what you eat.
Bisphenols are also very inexpensive to make, and that is a huge factor in an industry's choice of chemicals and compounds. For years, there were claims that these compounds 1) didn't act like estrogen and 2) didn't leach from packaging into consumer products. We know without a doubt that the second claim is wrong, and evidence is building that these chemicals can stand in for estrogen.
If companies have swapped BPA for BPS, how can you tell?
Vom Saal: You couldn't. All plastics today are complex mixtures of substances that are protected under U.S. law by product confidentiality legislation. Sometimes companies don't even know what's in the plastics that they're using.
If you're going to say something is BPA-free, it really should be, or you can get into trouble with the FDA over mislabeling a product. So you would assume that somebody has tested that. But the problem is that BPA-free today means likely BPS or some other cocktail that's likely to be as bad or worse than BPA.
How do we avoid these chemicals?
Vandenberg: We have to keep in mind that there are estrogenic compounds in a wide range of products, including food packaging, personal care products (like soaps, deodorant), pesticides used on our crops, in homes, and in yards, and so on.
There are also "natural" estrogens found in some plants like carrots, although these phytoestrogens have been found in human diets for millions of years. It is therefore not possible to entirely avoid exposures to these chemicals. Making good choices where possible -- like buying organic when you can, and buying fresh vegetables instead of canned when you can, and looking into the ingredients on your personal care products -- is really the best you can do.
Since these compounds are really hard to avoid, you can't "shop your way out" of this problem. Instead, change is needed at a much higher level -- how we regulate chemicals. [Editors note: Chemicals are currently not tested for safety before they're used in everyday products. They're only regulated after they've been shown to cause harm, a process that can take years.] And individuals can do something about this, by asking their legislators to support appropriate action.
Vom Saal: My levels of these chemicals are very low because I do things that are based on everything I know, accepting that there are lots of things I don't know, so I'm never going to go down to zero.
I don't drink any kind of soda out of a can. I don't eat any kind of canned product.
Whenever I go to the store and it isn't absolutely essential that I need the receipt, I'll say, "Throw the receipt away." [BPA coats the thermal paper that's used to print some retail receipts.]
If I need the receipt, I'll fold it so I'm only touching the back and not the print face, which is where the coating of BPA is.
And I wash my hands after handling them. The problem of trying to wash this off your skin is that the components of soap actually drive BPA through your skin, but it's still better to do that than leave it on there. And best not to touch the receipt at all.
We assume that all plastics have chemicals in them that are potentially harmful, particularly under heat. So I'll put food that needs to be frozen into plastic containers, but never take those containers out and heat them up. I take the food out of it. I don't even put those containers in a dishwasher because they degrade.
My assumption is that all plastics have some kind of chemicals in them that, particularly under heat, will increase the migration of these chemicals out of the plastic.
Kinch: The advice I give my friends, especially my friends who are pregnant, is be careful when you're cooking with plastic, especially microwaving. And be careful with canned foods. And if you don't need to take a receipt, just say no to the receipt.
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SOURCES: Laura Vandenberg, PhD, assistant professor of environmental health sciences, The University of Massachusetts at Amherst, Amherst, MA. Cassandra Kinch, PhD candidate, The University of Calgary, Alberta, Canada. Frederick vom Saal, professor, department of biology, University of Missouri, Columbia, MO. Prepared statement, American Chemistry Council.
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