WEDNESDAY, Jan. 30 (HealthDay News) -- Exposing plastic bottles to boiling water can release a potentially harmful chemical 55 times faster than normal, new research suggests.

Bisphenol A (BPA) is found in the plastics that make up water bottles, baby bottles, and other food and drink packaging. It acts as an environmental estrogen and can disrupt the function of the endocrine system.

In 2007, an expert panel convened by the U.S. Center for the Evaluation of Risks to Human Reproduction (CERHR) concluded that exposure to BPA presents some risk to development and reproduction, although it's unclear at what level that harm begins to occur.

"There isn't a real answer," said study senior author Scott Belcher, an associate professor of pharmacology at the University of Cincinnati. "There seems to be a current difference of opinion between the scientific research field and the folks doing risk assessment. If you were to sum it up in an easy, relatively conservative way, the scientific data points to some reason for caution at low concentrations. There really isn't much information regarding the effects on human populations directly."

Belcher's findings appear in the Jan. 30 issue of the journal Toxicology Letters.

Animal experiments have suggested that BPA may mimic the female sex hormone estradiol. The fear has been that exposure to BPA can cause birth defects and developmental problems. In addition, exposure to BPA has been blamed for a variety of other problems, including cancer, diabetes, obesity and attention-deficit disorder.

Exposure to BPA can occur through direct contact or by exposure to food or drink that has been in contact with material containing BPA.

Previous studies had found that repeatedly scrubbing, washing and boiling polycarbonate baby bottles could cause them to release BPA.

"It was migrating from the bottle into the water," Belcher explained.

This latest study tried to assess the effect from "normal" use, looking at both "old" polycarbonate water bottles from a local climbing gym as well as new bottles of the same brand.

The age of the bottle made no difference in the amount of BPA released.

However, if the bottles were briefly exposed to boiling water, they released BPA 55 times more rapidly than before being dunked in the hot water, the study said.

"There's nothing new in this paper," said Steven Hentges, executive director of the polycarbonate business unit of the American Plastics Council. "Migration has been studied many times before. In a sense, this is good news because it confirms what we already know."

Kirby Donnelly, department head of environmental and occupational health at the Texas A&M School of Rural Public Health, said the new finding was "not surprising" because it is a basic principle of chemistry that if a solvent is heated up, it will form a liquid solution.

"With BPA there are such contradictions as to whether it is toxic or nontoxic; a lot of times, it comes down to dose and duration," he added.

What does this mean to the average consumer?

According to Belcher, dishwashing temperatures might be OK but he stressed that even without the boiling water, such bottles do release small amounts of BPA.

For his part, Belcher avoids polycarbonate plastic. "That's been my personal choice," he said.

More information

Visit Statistical Assessment Service for more on BPA.

SOURCES: Scott Belcher, Ph.D., associate professor, pharmacology, University of Cincinnati; Steven Hentges, Ph.D., executive director, polycarbonate business unit, American Plastics Council; Kirby Donnelly, Ph.D., department head, environmental and occupational health, Texas A&M School of Rural Public Health, College Station; Jan. 30, 2008, Toxicology Letters

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