Exposing drinking bottles made from polycarbonate plastic to boiling water significantly speeds up the release of the chemical bisphenol A compared with room temperature water — and the amount of leaching is similar whether containers are well-used or brand new, researchers say.

'I'm not recommending for myself or others to throw their hot tea in these [bottles] or throw them in a microwave to make hot cocoa before they go skiing.'—Scott Belcher, researcher

The scientists at the University of Cincinnati found that when new and used polycarbonate drinking bottles were filled with boiling water and left for 24 hours, concentrations of bisphenol A (BPA) were released at rates up to 55 times more rapidly than with room temperature water.

Amounts of the chemical, which acts like the hormone estrogen, also leached out in higher quantities at the higher temperature, said study co-author Scott Belcher, an associate professor of pharmacology.

Bisphenol A found to affect reproduction in animal studies

Bisphenol A, widely used in such products as reusable water bottles, baby bottles, food-can linings and water pipes, has been shown to affect reproduction and brain development in animal studies.

"You could see that there are times when you would be putting hot liquids in these or boiling these or putting polycarbonate to these kinds of temperatures," Belcher said Tuesday from Cincinnati, noting that parents heat up plastic baby bottles and some people use water bottles for hot drinks.

While its effects are far from well-studied in humans, primarily because the chemical is so ubiquitous in daily life, there are concerns that BPA could contribute to some breast and prostate cancers as well as infertility in people.

Some retailers, including Canada's Mountain Equipment Co-op chain, have stopped selling water bottles made from polycarbonate plastic until a review of BPA's safety in humans is completed by Health Canada. An initial report to the federal government is expected in May.

Plastic bottle maker Nalgene says on its website that BPA has been used around the globe for more than 50 years, noting studies from the U.S. Food and Drug Administration and the Environmental Protection Agency have shown the chemical doesn't pose a health risk.

Study mimicked hiker's habits

To conduct the study, published in Wednesday's issue of the journal Toxicology Letters, the U.S. researchers measured amounts of BPA that escaped from one- to nine-year-old plastic bottles collected from participants at a local climbing gym.

Mountain Equipment Co-op announced in December it was removing products containing bisphenol A from its stores because of health concerns.
(CBC)

The bottles had been filled with room-temperature water and left for seven days. The experiment was also conducted with never-used bottles made by the same manufacturer.

"We just took that water, incubated it and at different times during the seven days we collected samples and then the sample at the end of the incubation period and compared the amount in new versus used," he said.

"And we really did not see any difference between the amount (of BPA) that was liberated."

The scientists then filled the bottles with boiling water, left them at room temperature for 24 hours, then measured BPA concentrations.

"My thought was it was more like mimicking what happens in the alpine world when you're climbing or something, where you could boil your water and dump it in or drink your hot tea in it," said Belcher, noting that the amount of chemical and the speed at which it was released was vastly increased at higher temperatures.

So what should consumers make of the finding and what should they do?

"I still haven't got a good answer for this one," he said. "I can tell you what I've done. I've tried to eliminate polycarbonate as much as I can.… I'm not recommending for myself or others to throw their hot tea in these or throw them in a microwave to make hot cocoa before they go skiing."