Plastics have reared their controversial head again, but this time it’s no urban legend. A group of Japanese researchers found that common plastic items, like baby bottles and soup bowls, could leach a hormone-mimicking compound into the consumables they hold.
The plastic in question is polycarbonate, a polymer made by stringing together molecules of bisphenol-A (BPA). BPA has estrogen-like activity and has been shown to increase the risk of cancer and cause developmental toxicity in laboratory animals. The Japanese researchers tested ten different polycarbonate baby bottles and found that, when heated, all leached BPA into the liquids they were holding. Food cans lined with polycarbonate were also found to leach BPA.
This study raises some serious concerns for parents and consumers worried about what they’re ingesting from their plastic containers. But to date, there have only been a handful of studies investigating the effects of BPA in humans. Almost all of the toxicology data has come from laboratory and animal studies. This has resulted in serious controversy between some scientists, who say that there is enough data to confirm that BPA is a threat to human health, and the plastic industry, who contends it is perfectly safe.
I spoke by phone with Dr. Frederick S. vom Saal, a researcher at the University of Missouri-Columbia who has been studying the low dosage effects of bisphenol-A in animals. He feels that we should be taking the matter of BPA leaching very seriously, especially for baby bottles.
“While the Japanese researchers used new bottles, older, worn bottles are most likely leaching more BPA and the older a bottle is, the increased rate of leaching.”
He also notes that although the amount of BPA an adult is getting from a bottle may be below the safety limit for their weight, exposure amounts must be adjusted for body weight. For a six to nine pound baby, the levels are the same as those that cause harm in animal studies.
“From a regulatory perspective, human exposure is supposed to be, at a minimum, 1000 times lower than the amount that causes harm in lab animals. Government funded research has found that the amount humans have in their body is higher than the amount needed to stimulate abnormal cell growth in animals. Humans are being exposed to amounts that can cause harm. There is no safety margin.”
Since the researchers heated the liquid used in the studies, I wondered if room temperature liquids were enough to leach BPA from plastic products. Dr. vom Saal assured me that leaching can in fact happen at room temperature, which is about seventy degrees.
“The higher the heat, the greater the leaching. If you put hot water in a new baby bottle, you’re modeling what you’d get at room temperature for an older bottle.”
Should adults be worried too?
“BPA acts like a birth control pill in the sense that it takes over your endocrine system. Like the pill, when you remove the exogenous [foreign] compound, your own hormones kick in and your system will go back to normal. But, if you keep BPA there long enough, you increase your risk factors for cancer. So yes, it can harm adults. But a single exposure for babies can cause permanent harm.”
Dr. vom Saal notes that increased blood levels of BPA may lead to genetic abnormalities in pregnant women, which in turn, can lead to miscarriages.
Although he confirms that there have been only a couple studies to test the outcome of exposure to BPA in humans, he doesn’t feel we should wait for this evidence to accumulate before acting. He compares it to the situation with diethylstilbestrol (DES), a hormone used in the 1970s to prevent miscarriage, which was later found to cause birth abnormalities and cancer in offspring.
A quick visit to bisphenol-a.org (a website sponsored by The American Plastics Council), finds a much different slant on the evidence. The site states that human exposure to BPA is well below the levels set by governmental regulatory agencies. It decries the City of San Francisco’s December 1, 2006 decision to ban all children’s toys and products that contain BPA, saying the decision is not scientifically based.
Whether you believe the scientists or the industry, it’s clear that there are ways to avoid exposure to polycarbonate products.
“There are alternative plastics for baby bottles. Like polypropylene, polyethylene, and glass bottles which don’t break. Why would you use a plastic that has the potential to release a carcinogenic compound?” asks Dr. vom Saal.
And for adults: “Don’t eat any canned products, which can leach BPA.”
While my friend’s plastic water bottle theory was in fact an urban legend (my water bottle was made from polypropylene, which doesn’t contain BPA) I’d rather not take my chances with polycarbonate. Fresh veggies, here I come.