Bisphenol-A (BPA), the endocrine-disrupting chemical in plastics — and the go-to environmental health villain — has vexed public-health experts for at least a decade. Reams of inconclusive and conflicting studies on the health effects of the compound, which is found in plastic food containers, water bottles and the epoxy lining of cans, have hampered a verdict on the lingering question: Is BPA safe?
And that has further prevented environmental groups and other BPA opponents from getting the chemical banned in the United States. Meanwhile, Canada and some European countries have banned it in certain products meant for children, like baby bottles and sippy cups. And just two weeks ago, Canada went one step further, classifying BPA as a toxic substance.
Why? In short, as the New York Times explains this week in a comprehensive examination of the ongoing debate over BPA, the E.U. and Canada both subscribe to a “banned until proven innocent” approach to environmental health regulation and safety. In the U.S., the Environmental Protection Agency (EPA) and Food and Drug Administration (FDA) require conclusive evidence that a compound causes harm before they will ban it.
Not that a ban on BPA would be easy — or even possible. The chemical is ubiquitous in our packaging and plastic products, and probably every American is exposed to it. A 2004 National Institute of Environmental Health Sciences study found that 93% of urine samples from American children under the age of 6 contained the BPA. It is also present in our fat cells, umbilical-cord blood and breast milk. One of a class of toxicants that mimics the hormone estrogen, BPA has been linked to the increased risk of cancers, including breast cancer in women and prostate cancer in men, obesity, diabetes and even to the earlier onset of puberty in girls.
Problem is, these associations, which are based on animal and laboratory studies, have not not been clinically or observationally reproduced in human trials. Most connections between BPA and human illness remain hypothetical. As the Times reports:
Most of the evidence against BPA comes from studies that find harmful effects in rats and mice at low doses comparable to the levels to which people are exposed. Sometimes the results seem downright weird, indicating that low doses could be worse than higher ones. There is sharp disagreement among scientists about how to interpret some research. The disputes arise in part because scientists from different disciplines — endocrinologists versus toxicologists, academic researchers versus those at regulatory agencies — do research in different ways that can make findings hard to reconcile.
The biggest unanswered question is whether low doses — the kind to which most people are exposed — can have lasting, harmful effects in fetuses and young children. Dr. [Linda S.] Birnbaum, [director of the National Institute of Environmental Health Sciences, part of the National Institutes of Health], said it was crucial to find out for sure whether the low-dose effects in animals really occur. “We have hundreds of studies that show they do, and then some that don’t,” she said.
Joining the fray, a round-up of some of the most recent research into BPA:
- One animal study out this month in Biology of Reproduction suggested that BPA could affect fertility. When their pregnant mothers were exposed to levels of BPA comparable to average human exposure, it disrupted the development of ovaries in mouse fetuses.
- BPA may also increase testosterone levels in men, according to recent research in Environmental Health Perspectives. The compound is actually known to block the action of testosterone, but the end result of that blockage, the study’s researchers hypothesize, is to encourage the body to create more testosterone.
- BPA derivatives are an increasingly popular additive in dental sealants and the resin used to make children’s fillings, according to a Pediatrics study published on Sept. 6. The study found that BPA is detectable in saliva up to 3 hours after a child’s tooth has been filled because saliva breaks down the resin, releasing the compound. But the dental products should be safe for use, according to the study, as long as dentists make sure to wipe or rinse away residue after treatment. Pregnant women, however, are advised to wait until after delivery for treatment.
While the larger question of BPA safety remains unanswered, the use of the compound is certainly on the rise worldwide. BPA production, already at 2 million tons per year globally, is projected to grow by 6% to 10% per year, according to a new study (citing an analysis in the European Chemical News).
Most people don’t want their children to be guinea pigs, so growing concern has led several states to ban the chemical from plastics used to make children’s toys, bottles and eating implements. Connecticut, Maryland, Massachusetts, Minnesota, New York, Vermont, Wisconsin and Washington all restrict BPA this way, though a similar bill was defeated in California’s senate on Sept. 1.
New, standardized studies are underway: the Times reports that the government is currently funding analyses of all possible health consequences of BPA, including its association with obesity, diabetes, prostate and breast cancers, nervous system disorders, infertility, fetal development and immune disorders. Check back in in two years or so, when results from the new studies are expected.
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