If you're like many folks, you've traded in your plastic water bottle for a metal one to limit your family's exposure to the estrogen-mimicking chemical, BPA. But a recent study shows that if you didn't choose your new bottle carefully, you may not have solved the problem.

The study, published in the online journal Chemosphere, found that some metal water bottles leach even more BPA than similar bottles made from plastic. How is it possible for metal bottles to leach a chemical commonly found in plastic? BPA doesn’t come from the metal but from an epoxy-resin lining that may contain the chemical. And just as with plastic bottles, the leaching is greater when the bottles are exposed to high temperatures.  

For the study, the University of Cincinnati College of Medicine researchers tested polycarbonate and resin-lined aluminum bottles along with new BPA-free “Tritan” plastic bottles (by Nalgene), stainless steel bottles (by Sigg) and new “EcoCare” resin-lined aluminum bottles (by Sigg). After cleaning each bottle with BPA-free water, the team stored room-temperature water in three bottles of each type for five days. They also filled additional bottles with boiling water and allowed it to cool to room temperature over the next day.

The results? Levels of BPA were below the limit of detection for the new "BPA-Free" bottles from Sigg and Nalgene. But the old polycarbonate bottles leached 0.17 to 0.3 nanograms of BPA per milliliter of water during the room temperature tests. By contrast, the aluminum bottles with an epoxy-resin liner leached substantially more, up to six times more BPA than the worst-leaching polycarbonate bottle. And as expected, exposing the bottles to hot-water quadrupled BPA leaching.  

The bottom line: If you want a reusable bottle that limits your family's exposure to BPA, be sure to take a look inside the rim. Ideally, look for a bottle that is all metal — with no plastic liner inside. If it is lined, choose a bottle with a white lining — as these probably will not leach BPA. If it has a golden-orange lining, take a pass — these were the worst offenders in the study.

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