The estrogen-mimicking pollutant traces to a polymer resin lining affected bottles

By Janet Raloff

Web edition: July 11, 2011

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When metal 'looks' like plastic

Some aluminum water bottles host a lining that contains—and leaches—BPA.

Credit: iStockPhoto

Consumers who switched from polycarbonate-plastic water bottles to metal ones in hopes of avoiding the risk that bisphenol A will leach into their beverages aren’t necessarily any better off, a new study finds. Some metal water bottles leach even more BPA — an estrogen-mimicking pollutant — than do ones made from the now-pariah plastic.

That BPA doesn’t come from the metal, by the way, but from an epoxy-resin lining that is based on BPA’s recipe.

That’s the bad news.

If you’re willing to spring for name-brand bottles, however, several included in the new study either did not contain a resin liner or did not contain one that leached BPA. These data suggest such products would be a better bet for individuals who are especially risk averse. But BPA leaching by even the worst performing water bottles was low, observes toxicologist Scott Belcher of the University of Cincinnati College of Medicine, an author of the new study.

“Low is a fair characterization,” he says. “Infinitesimally low and irrelevant is not fair,” he adds, because there are so many potential sources of the pollutant in the human environment “and this is just one.” Moreover, his team confirmed, temperature abuse could — and did — exaggerate BPA releases by otherwise low-emitting bottles.

Belcher’s group has for years been testing the effects of BPA on heart-muscle cells. This work has shown that in rodent hearts, BPA exposures foster potentially life-threatening arrhythmias. And the risk intensifies in the presence of estrogen. (The team’s published data suggest that owing to the levels of estrogen present in women, the addition of substantial BPA via the diet might be capable of provoking such arrhythmias.)

After having a number of individuals plead with his team to test whether ostensibly BPA-free water bottles really were devoid of the pollutant, Belcher and his colleagues agreed to perform a series of tests. The researchers used old (but unused) polycarbonate and resin-lined aluminum bottles that they had closeted away several years earlier, along with new BPA-free “Tritan” plastic bottles (by Nalgene), stainless steel bottles (by Sigg) and new “EcoCare” resin-lined aluminum bottles (by Sigg). They also purchased some new aluminum water bottles from a major discount retailer.

After cleaning each unit, the scientists stored room-temperature water in three bottles of each type for five days. In an additional set of experiments, Belcher’s team filled the bottles with boiling water (which tests by others had shown could boost BPA leaching) and then let the water cool to room temperature over the next day.

Levels of BPA were below the limit of detection for the new Sigg and Nalgene bottles, the scientists reported early online July 8 in Chemosphere.

By contrast, the old polycarbonate bottles leached 0.17 to 0.3 nanograms of BPA per milliliter of water during the room temperature tests. The old aluminum bottles with an epoxy-resin liner (which looked golden orange) leached 0.59 to 0.14 nanograms per milliliter. Brand-new epoxy-resin-lined aluminum water bottles leached substantially more — up to six times more BPA than the worst-leaching polycarbonate bottle and more than 10 times as much BPA as the polycarbonate-plastic bottle that had leached the least.

Oh, and the hot-water test: It quadrupled BPA leaching over what occurred when water had been kept at or below room temperature.

Belcher says he was pleased to see that the bottles that had been sold as BPA-free in fact did not leach the steroid-hormone-mimicking pollutant. But he also cautions that at present, “BPA-free doesn’t really have a meaning, other than being a marketing tag.”  There are no regulations to limit which products can make that claim, he explains. And that’s important because some resins don’t contain BPA as a direct ingredient, but during breakdown might release the chemical or a biologically similar cousin.

For now, he notes, it appears that consumers can get a good gauge of whether bottles contain a BPA-based resin by inspecting the inside of the metal vessel. A golden-orange coating points to a material that can shed BPA, Belcher says; a white coating doesn't.

But what these experiments don’t establish is the absolute risk associated with use of drinking from bottles that leach BPA.

Recent animal studies, including a pair I reported on a couple of weeks back, indicate that exposures to BPA in the womb can rewire the developing brain in ways that alter gender-specific behaviors. Even in children, prenatal exposures to this chemical have been linked with a gender-bending of behaviors.

But no one has yet demonstrated the long-term importance of such changes. There’s the presumption that they’re deleterious and could ultimately affect gender identity or reproduction. There’s also, however, the possibility that such changes, though measurable, hold no more biological significance than whether a baby is born with brown eyes versus green ones.

So those who subscribe to the precautionary principle may want to withhold judgment. And, of course, keep abreast of the developing science reported here and elsewhere.