TORONTO – Exposing drinking bottles made from polycarbonate plastic to boiling water significantly speeds up the release of the controversial 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.
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 occurred 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, 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.
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.
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.”
Dr. Kapil Khatter, pollution policy adviser for the Canadian group Environmental Defence, said the study confirms that bisphenol A in polycarbonate plastic containers is “unstable and comes out.”
Environmental Defence is pushing for a ban on food and beverage containers that contain BPA while Health Canada completes its safety review.
“What we’re sort of saying right now, from what we know right now, is food and beverage containers are probably our largest source and it’s not something we can’t avoid,” Khatter said from Ottawa, adding that consumers can switch to alternative materials like glass and stainless steel.
“From our point of view, there’s no reason right now to continue to use these food and beverage containers while we’re trying to figure out whether prostate cancer rates going up and breast cancer rates going up is related to exposure to those chemicals.”
Dr. Jack Uetrecht, a professor of pharmacy and toxicology at the University of Toronto, said it’s impossible to know how BPA exposure affects health because it would be unethical to test the chemical directly in humans – and studies in animals can only point to “possible” harm in people.
“The probability that it’s causing a significant human health problem is probably small,” he said. “On the other hand, there’s too many things we don’t know and don’t understand … So I think we ought to try as best we can to minimize exposure, and unfortunately that’s often not done.”