Chemical Leaks when Water is Hot

Developing cerebellum neurons. Courtesy of Scott Belcher; Below courtesy of University of Cincinnati

Friday, February 1st, 2008--

Campers take note: You may want to think twice about washing your water bottles, or using hot water anyway. A new study suggests that polycarbonate water bottles--like some Nalgenes and other durable bottles made for hiking trips--leech the chemical bisphenol A (BPA) up to 55-times faster when exposed to boiling water as compared to room temperature water.

Polycarbonate plastic is made of long strands of BPA monomers. "That's what gives it its desirable properties," says Scott Belcher, professor of pharmacology and cell biophysics at University of Cincinnati and an author on the study. Nalgene uses polycarbonate because it provides "extraordinary durability, glass like clarity and resistance to stains and odors," according to its website.

The potential problem for water bottle users is that BPA also mimics the hormone estrogen and has been shown to have effects on reproductive function, prostate cancer, breast cancer, neuronal function, and brain development in wildlife, lab animals, and cell cultures, Belcher says.

Previous studies, including an examination of polycarbonate baby bottles, suggested that the degree of use of the plastic correlates with increased BPA seepage. Belcher's study, published in the journal Toxicology Letters, found no significant difference between new and used bottles. Instead, it was temperature of the liquid inside the bottle that significantly changed the rate of BPA migration. It's not clear exactly why heat would prompt faster BPA release Belcher says, but one hypothesis is that heat helps break the bonds between the BPA monomers, freeing them to migrate into the water.

Belcher's lab, which focuses on the effects of estrogen on brain development, used a cell culture of developing neurons to measure the biological effects of the liquid coming from the bottles. When they exposed the neurons, taken from the cerebellum area of rat brains, to the liquid from the bottles, some cells self-destructed.

"Previously we had shown that bisphenol A did all of the estrogen-like things in these populations of neurons, but we didn't show directly that bisphenol A was killing the cells," Belcher says. He adds that this study shows that direct application of BPA killed some neuronal cells and that the material leeching from the water bottles had the same effect.

Note that (naturally-occuring) estrogen also prompts some cells to die, Belcher says. So what does BPA exposure mean for humans? "That is the big question that is vigorously being debated right now," Belcher says. Definitive studies on humans have not been done, he says.

"If you put all of the data together... there may be a reason for caution associated with BPA," Belcher says. But water bottles are only one small source of our exposure to BPA, and BPA is only one chemical of many that we're exposed to, he says. "We have a complex mixture of multiple different chemcials, working through many different mechanisms of action, leading to many different physiological responses--that's really quite difficult to tackle."

--Flora Lichtman