An article on the website of the Sierra Club has given new life to the Internet rumor that plastic water bottles are a health hazard, possibly the cause of birth defects such as Down Syndrome. Years of studies on the purported culprit chemical, bisphenol-A (BPA), have not shown any health effects on humans, but one study showing minor effects on mouse egg cells, led by Dr. Patricia Hunt at Case Western Reserve University, has provided the grain of truth leading to the latest excessive fear.
In this experiment conducted by Hunt and co-workers, BPA was fed to female mice and the oocytes that they produced were examined. The results suggested BPA caused an increase in chromosomal abnormalities in these oocytes. However:
- The study has not been replicated by other scientists.
- Comprehensive, large-scale studies (while they may in theory have failed to detect increased oocyte chromosomal abnormalities) have not shown any increase in actual birth defects.
- Previous studies appearing to show BPA effects have not been reproducible.
- The single study by Hunt is unlikely to change the prevailing weight of scientific evidence, which the FDA and other scientific bodies say show no risk from "environmental endocrine disruptors."
- Health effects in humans are probably even less likely than health effects in mice, since a recent study (by Volkel et al) suggests that BPA is far more rapidly and completely metabolized in humans than in rodents, decreasing the odds of it doing damage by lingering in the body.
- Humans are not routinely exposed to the large amounts of the chemical that the mice were.
Still, the single mouse oocyte study has rapidly grown legs, mutating into an increasingly scary tale as it was retold by first the Sierra Club and then multiple college newspapers, which picked up on the story. Dr. Hunt's tendency to hyperbole has made things easy for the activists: the Sierra Club quotes her saying "we have been stunned by what we have seen" and "If we wait for really hard evidence in humans, it will be too late."
The Sierra Club article quickly segues from Hunt's limited study to discussion of the more radical claims of Theo Colborn, author of Our Stolen Future, who calls widespread endocrine disrupters in the environment a "very, very sticky problem...that's everywhere, and in everything." Colborn warns of risks to pregnant women, newborns, young children, and women who might get pregnant, advising people to switch to other types of containers.
Subsequent newspaper articles have tended to gloss over the multiple steps of supposition and speculation that led to plastiphobia: if the single oocyte study is replicated, if the oocyte effects are real, if the oocyte effects translate into developmental abnormalities, if BPA has the same effect on humans, if the minuscule amounts of BPA available in plastic water bottles were leaching out in amounts large enough to effect humans none of which has yet been shown and if the resultant hypothetical risk to humans were large enough to warrant changing our behavior (not every risk is or we'd avoid everything), there might be reason to worry. In the meantime, there is, in all likelihood, just one more in the endless series of unnecessary chemical scares and, inevitably, a few newspaper articles that skip over all the maybes and logical leaps and simply say: a chemical may be leaking out of your water bottle and causing Down Syndrome!
People's default reaction to any manmade chemical these days is fear though manmade chemicals have not been shown to be any more likely than naturally-occurring ones to have health effects on humans, despite the widespread public assumption to the contrary. We've been using plastic water bottles and studying chemicals of the sort used in them for decades without any sign of ill effects on humans. The FDA says that Hunt's lone study is insufficient to reverse the conclusion that such plastics are safe. Don't let the Sierra Club frighten you into going thirsty.
March 17, 2004
Perhaps the folks who are so concerned about plastic bottles should just go back to drinking tap water out of glasses (or drinking fountains) instead of paying manufacturer for a totally unnecessary product. Then, at least, their irrational assessment of risks will help them avoid a very real risk to their pocketbook. Last time I looked, 12 oz. of perfectly healthy tap water was less than 1/8 of a penny and a bottle of water from the Coke folks was $1.25.
And thanks again to ACSH for trying to direct people's fears away from the microscopic and toward the more important such as smoking and overeating.
David C. Griffith