Canada has banned the import and sale of polycarbonate baby bottles containing bisphenol A, citing concerns about exposing infants to the chemical. (Jonathan Hayward/Canadian Press)

Bisphenol A, a chemical used to make many hard plastic products, may stay in the body longer than previously thought.

Researchers say the finding may also mean that people are ingesting the chemical from non-food sources.

In Wednesday's online issue of the journal Environmental Health Perspectives, Dr. Richard Stahlhut of the University of Rochester's Environmental Health Sciences Center said high levels of BPA remained in the body after people in a study fasted for as long as 24 hours.

In October 2008, Canada became the first country in the world to ban the import and sale of polycarbonate baby bottles containing bisphenol A, citing concerns about exposing infants to the chemical.

Late last year, the U.S. Food and Drug Administration said it planned more research into the safety of BPA, but the agency indicated no immediate plans to follow Canada's curb on the chemical.

In the latest study, Stahlhut and his colleagues looked at BPA levels in the urine of 1,469 U.S. adults who took part in a government health survey.

The researchers said they expected to see a relationship between the last meal, fasting time and BPA levels.

Based on the assumption that BPA is excreted quickly and people are exposed to the chemical mainly through food, much lower BPA levels were expected among those who fasted for 24 hours than those who fasted for 8.5 hours.

Safety assumption questioned

"Our results simply do not fit that picture," said Stahlhut.

"The research community has clues that could help explain some of these results, but to date the importance of the clues have been underestimated. We must chase them much more vigorously now."

BPA levels appeared to drop about eight times more slowly than expected, he added.

The researchers proposed two possible explanations for the higher-than-expected levels among people who fasted:

• Exposure to BPA from other sources, such as house dust or tap water.
• BPA may seep into fat tissues, where it is released more slowly.

"The finding is surprising and a little disturbing, in that all assumptions about the safety of BPA made by regulatory agencies are based on the idea that we are primarily exposed to this from eating," Fred vom Saal, a professor of biological sciences at the University of Missouri-Columbia Division of Biological Sciences, told HealthDay News.

To find out, more research is needed to evaluate the effects of BPA on fat tissue hormones and function, and to compare BPA levels in fat, blood and urine, Stahlhut said.

Bisphenol A is a chemical compound found in some hard, clear, lightweight plastics and resins. It's used in the production of various types of food and drink containers, compact discs, electronics and automobile parts, and as a liner in some metal cans.

Animal studies suggest that, once ingested, BPA may imitate estrogen and other hormones, according to the U.S. National Institutes of Health.

In a study published in September 2008 in the Journal of the American Medical Asssociation, adults with higher BPA levels in their urine were linked to higher risks for heart disease and diabetes.

The American Chemistry Council, which represents makers of BPA, maintains that the chemical is safe for all uses. Steven Hentges, spokesman for the trade group, dismissed the study's conclusions as "speculative at best."