July 12, 2011 -- Reusable metal water bottles have lately gained a certain cachet as a greener, healthier alternative to some kinds of plastics, which can release trace amounts of a hormone-disrupting chemical into the liquids they hold.
But a new study shows that some kinds of aluminum bottles may be releasing more of that chemical, known as bisphenol A (BPA), than the hard, clear polycarbonate plastic bottles they were supposed replace.
Sales of one popular brand of reusable water bottles have roughly tripled in the four years since it was launched in the United States, according to The Aluminum Association, an industry trade group in Arlington, Va.
In a 2009 interview with the New York Times, the CEO of that company said sales had been driven by the “huge green wave” and “the BPA scare.”
Worries About BPA
BPA is a chemical that’s widely used in food packaging. It’s also thought to act like a hormone in the body.
Though the research is still ongoing, in animal studies, BPA has been linked to a large range of effects, from birth defects, to problems with brain and nervous system function, to reproductive abnormalities and some kinds of cancer. In humans, BPA has been tied to reproductive problems in women and men. A 2008 study by researchers at the CDC detected it in the urine of 93% of people they tested.
Another recent study showed that people could lower their levels of BPA by eating fresh, rather than packaged, foods and by avoiding plastic food containers.
BPA in Aluminum Bottles
In a carefully controlled test, where researchers stored ultra-pure water in several different kinds of containers for five days, they found that some aluminum bottles released up to five times the amount of BPA that was shed by the older, polycarbonate bottles.
“It’s been used for marketing purposes,” says study researcher Scott M. Belcher, PhD, an associate professor of pharmacology and cell biophysics at the University of Cincinnati, in Ohio.
“If you pick up an aluminum bottle from your super-cheap discount retailer, you can’t be so sure what’s in it,” Belcher tells WebMD, “Especially aluminum, because they do require a lining of some sort.”
Sometimes, that sprayed-on liner is made with an epoxy resin that contains BPA.
“It may be aluminum on the outside, but if it’s plastic on the inside or this epoxy, it’s the same thing as a polycarbonate bottle,” says Sonya Lunder, a senior analyst for the nonprofit Environmental Working Group in Washington, D.C.
Experts say that epoxy liner usually looks copper-colored and may feel slightly tacky to the touch, but it may also not feel like anything but bare metal, making it tough to know when it’s there.
“For the consumer, this is a tricky issue, to try to boil this down to some simple, useful tips that people can use to distinguish products,” Lunder says. “This study is kind of showing that you can’t just look at what’s outside of the container, you need to know some specifics about what’s on the inside.”
One thing people can do to reduce their exposure, Lunder says, is to carefully follow the manufacturer’s directions about how to use the bottles.
The study found that epoxy-lined bottles released even more BPA when the water was heated before it was poured in.
BPA-Free Claims May Hold Water
The good news is that some companies that make reusable water bottles have already listened to consumer concerns about BPA and removed it from a newer generation of materials for their containers.
Those bottles, which say "BPA-Free" on the packaging, largely live up to their promises, the study showed.
Two containers, an aluminum bottle with a newer kind of proprietary liner and a next-generation plastic bottle, both had low-to-undetectable BPA levels in the test.
That’s an important finding, researchers point out, because “BPA-free” really doesn’t have any regulatory meaning or definition. Consumers are left to trust companies about their claims.
The study also exonerated uncoated stainless steel bottles.
Experts say the new study should serve as a wake-up call to consumers and government regulators.
“This new study finds that some products marketed as BPA-free alternatives are -- and some are not -- BPA free, reinforcing that we have a buyer-beware consumer economy with very little government oversight,” says Ruthann Rudel, director of research at the Silent Spring Institute in Newton, Mass., in an email to WebMD.
“People want to know that their health is not jeopardized by food packaging and other consumer products, and to get there we need to rethink our approach to chemical regulation,” she says.