WEDNESDAY, Jan. 28, 2009 (HealthDay News) -- Bisphenol A, a controversial chemical used to harden plastics for consumer products such as baby bottles and food containers, appears to remain in the body much longer than thought, a new study says.
The finding suggests that exposure to BPA may come from many different sources, not just food products, or that the body doesn't metabolize the chemical as fast as has been thought, the researchers said.
The finding also adds to the controversy about the health consequences of exposure to the chemical, which some studies have linked to cancer, diabetes, heart disease and developmental problems in children.
"What this study shows is that either we are getting exposed to a lot more BPA than we thought, or it's hanging around longer than we thought, or both," said lead researcher Dr. Richard W. Stahlhut, a postdoctoral fellow at the University of Rochester Medical Center's Environmental Health Sciences Center, in New York.
The U.S. Food and Drug Administration was criticized by some scientists -- including one of its own advisory panels -- after it said last August that BPA did not pose a health threat. By December, the agency had agreed to re-examine that earlier ruling.
For the new study, Stahlhut's team collected data on 1,469 people who participated in the U.S. Center for Disease Control and Prevention's National Health and Nutrition Examination Survey. The researchers looked at the amount of BPA in urine and the length of time the participants had been fasting before the urine sample was taken.
Conventional wisdom says food is the most common source of BPA, and the body clears the chemical fairly quickly. The researchers expected to see less BPA in those who fasted the longest, compared to those who had eaten recently.
But, the researchers found that the levels of BPA in people who had fasted the longest were only moderately lower than in those who had just eaten. BPA levels dropped about eight times more slowly than expected, the scientists said.
One possibility is that people are exposed to more BPA than can be found in food alone, Stahlhut said, citing tap water or house dust as other sources. The other possibility is that BPA gets "hung up" in fat cells in the body, he said.
The findings were published online Jan. 28 in the journal Environmental Health Perspectives.
Stahlhut noted that BPA is used to harden plastics in many products, including plastic bottles, PVC water pipes and food-storage containers. It's also used to coat the inside of metal food cans and in dental sealants. It's even found in cash register receipts and recycled paper, he said.
About 93 percent of Americans have detectable levels of BPA in their urine, according to the CDC.
Fred vom Saal, a professor of biological sciences at the University of Missouri-Columbia Division of Biological Sciences, said more research is needed to determine all the ways people are potentially exposed to BPA.
"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," vom Saal said. "These data are not consistent with that assumption.
An estimated 8 billion to 9 billion pounds of BPA are produced each year, according to vom Saal. His own research with animals has found that the chemical isn't cleared as fast as people had thought.
"There is a lot about this chemical, and the way we are exposed to it and the amount we are exposed to, that we don't know about," he said. "The levels of exposure have to be higher than people have been estimating."
Steven Hentges, executive director of polycarbonate/BPA global group at the American Chemistry Council, disagreed with the study. BPA is safe and is quickly eliminated from the body, he said.
Hentges noted that studies show that most BPA is excreted by the body within half an hour. "In addition, human exposure to BPA is extremely low," he said. "CDC data shows us that exposure is about 1,000 times below safe intake levels established from animal data."
For more on BPA, visit the U.S. National Institute of Environmental Health Sciences.