Is Your Water Bottle Killing You?

 
CTV News is reporting that Mountain Equipment Co-op is going to stop selling polycarbonate water bottles [Sporting goods chain drops bisphenol A products]. The bottles leach tiny amounts of a compound called bisphenol-A (BPA) and there have been reports out for many years that BPA is dangerous to your health. One of the products that's causing concern is Nalgene® water bottles with the number 7 in a triangle. These bottles are make of a type of polycarbonate called Lexan that contains BPA.

Concern about possible health problems due to BPA have been around for years. As is usually the case whenever the alarm is sounded, the environmentalist/green/healthfood movements will be the first to respond. They have been strongly opposed to plastic water bottles for some time. Their claims about chemical dangers tend to be exaggerated so it's often hard to know who to believe. (But see TheGreenGuide for a reasoned opinion [ The Bisphenol-A Debate: A Suspect Chemical in Plastic Bottles and Cans].)

Bisphenol A resembles steroid hormones such as estrogen and it may interact with estrogen receptors. Some studies have linked it to increased risk for cancer in humans. There's a long list of other possible diseases that are possibly associated with BPA including the usual suspects like autism. Many of these presumed linkages are not credible but there are enough real scientific studies to cause concern.

The Bisphenol A website is maintained by a consortium of chemical companies. They have a clear vested interest in proving that their plastics are safe. The site contains many interesting facts and figures about the controversy including this report just released by Centers for Disease Control and Prevention (CDC) scientists in Atlanta, Georgia (USA) [Exposure of the U.S. Population to Bisphenol A and 4-tertiary-Octylphenol: 2003-2004]. The study shows that 93% of the population has detectable levels of BPA but these levels are far below the concentrations that produce harmful effects in animal studies.

What we need in situations like this is a neutral third party to evaluate the risks. Neither the chemical industry nor the healthfood industry can be trusted.

Along comes the Journal of the American Medical Association (JAMA). The Oct. 3, 2007 issue has an article summarizing the results of two recent studies [Expert Panels Weigh Bisphenol-A Risks].

The first study was done by a group of 38 scientists in November 2006.

After reviewing more than 700 studies, the group concluded that the molecular mechanism of BPA action in humans and animals is essentially identical, said Frederick S. vom Saal, PhD, of the Endocrine Disruptors Group at the University of Missouri-Columbia. Additionally, they determined that human and animal cells respond to similar doses of BPA and that the documented responses to very low-dose exposures can be explained by BPA's interaction with estrogen receptors on the cellular membrane.

"It's through these cell membrane receptors that doses below a part per trillion in cell culture can activate changes in cells," vom Saal said. "We're talking about levels of potency that are absolutely equivalent to estradiol."

The BPA doses that have been linked with health problems in animals are actually lower than the levels of free biologically active BPA that have been documented in human blood by a variety of techniques, such as ELISA testing and mass spectrometry, vom Saal said.

"The wide range of adverse effects of low doses of BPA in laboratory animals exposed both during development and in adulthood is a great cause for concern with regard to the potential for similar adverse effects in humans," according to the consensus statement. The statement calls for more research to probe BPA's effects in laboratory animals, wildlife, and humans.

The second study was done last August by a panel of the National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction.

Although the panel rated the likelihood of human reproductive problems as "minimal" or "negligible," based on existing studies, it did have "some concern" that exposure could have neurological or behavioral effects in pregnant women, fetuses, infants, and children.

One reason for the differences in the groups' conclusions is that the NTP panel chose to exclude studies in which animals were exposed to BPA through injections. Members of the panel noted that most human exposure occurs through ingestion of the substance and that this translates to lower doses because the chemical is metabolized by the liver. But other researchers argue that such studies should have been included and that excluding them overlooks important evidence that exposure to low doses of BPA may lead to morphological and functional changes in the reproductive tracts of animals exposed early in development (Maffini MV et al. Mol Cell Endocrinol. 2006;254-255:179-186).

The bottom line is that there is enough concern to warrant trying to cut down on BPA intake. While the evidence suggests that it may be impossible to completely avoid exposure, you can still avoid the most likely sources—including those plastic water bottles.

It's probably time to switch to glass or metal, just to be on the safe side.

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