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
All rights reserved