Most of the Chemical Is Quickly Eliminated in Urine, Researchers Say
By Salynn Boyles
WebMD Health News
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Reviewed by Laura J. Martin, MD
Sept. 28, 2011 -- Most of the bisphenol A (BPA) that adults ingest is quickly eliminated in the urine, new research confirms.
In the government-funded study, BPA was virtually undetectable in the blood of adults, even when levels in urine were high.
The study's lead researcher says the findings show that the "odds are very small" that BPA poses a significant public health risk. And a food packaging trade group called the research "definitive evidence" that adverse health effects from exposure to the chemical are unlikely.
But a CDC investigator who was among the first to show widespread exposure to BPA from food packaging manufactured with the chemical says the new study was not designed to address the health effects of exposure.
"This study confirms that exposure to BPA is common in the adult population," research chemist Antonia M. Calafat, PhD, of the CDC's National Center for Environmental Health, tells WebMD. "The study also shows that BPA appears to be excreted rather quickly and that concentrations in serum are much lower than concentrations in urine."
BPA Health Concerns
BPA is widely used in the manufacture of clear plastic bottles and other food containers and the epoxy resins used in the lining of many canned foods.
Health concerns about the chemical stem from lab and animal studies suggesting that it is an endocrine disrupter, mimicking the female sex hormone estrogen in the body.
Early last year, the FDA concluded that studies have generally supported the safety of low levels of BPA exposure in adults, but agency officials expressed concerns "about the potential effects on the brain, behavior, and prostate gland in fetuses, infants, and young children."
These fears resulted from studies in rodents designed to test the subtle effects of exposure to the chemical.
The newly reported study, which was funded by the Environmental Protection Agency, is the first to compare BPA levels in urine with levels of the active form of the chemical in the blood over a 24-hour period.
Lead researcher Justin G. Teeguarden, PhD, of the Pacific Northwest National Laboratory in Richland, Wash., says although it was clear that BPA does enter the body from food sources, little has been known about what happens to the chemical after this.
"Many researchers have reported exposure to bisphenol A from the diet," Teeguarden tells WebMD. "The real question is and always has been, 'Do we get enough of the bioactive form of the chemical in the blood to cause adverse effects?'"
Blood and urine samples from 20 adult volunteers were collected hourly during the day and several times at night over 24 hours. Over the course of the study day, the participants ate three meals made from canned foods with linings that contained BPA.
As a result, the average consumption of BPA was estimated to be 21% higher than the average for 95% of adults in the United States.
Despite the high exposure, levels of bioactive BPA in the blood were undetectable in the samples, Teeguarden says.
Independent analysis of the samples by the CDC and the FDA's National Center for Toxicological Research confirmed the findings.
In the CDC analysis, bioactive BPA was below the limit of detection in all 320 analyzed blood samples.
Impact of BPA on Children Unknown
The CDC's Calafat says the finding that blood levels of bioactive BPA are much lower than urine levels is not a big surprise.
"Based on the properties of BPA we would expect to see this," she says.
The study appears in the September issue of the Journal of Toxicological Sciences.
In a news release, the industry trade group North American Metal Packaging Alliance called the research a "landmark study" providing "definitive evidence that adverse health effects from bisphenol A are highly unlikely."
Sonya Lunder, who is a senior analyst with the research and advocacy organization Environmental Working Group, says although the findings are somewhat reassuring for adults, the study did not address the safety of BPA exposure in developing fetuses, babies, and children.
"Ninety-five percent of Americans have measurable BPA in their urine on any given day," she tells WebMD. "A longstanding concern has been that children, infants, and developing fetuses may have no ability or very limited ability to metabolize this chemical the way adults do."
Calafat says a host of studies funded by a $14 million grant from the American Recovery and Reinvestment Act should shed new light on the safety or harms of BPA exposure in adults and children within the next year or so.
SOURCES: Teeguarden, J.G., Journal of Toxicological Sciences, published online September 2011.Justin G. Teeguarden, PhD, Pacific Northwest National Laboratory, Richland, Wash.Antonia M. Calafat, PhD, National Center for Environmental Health, CDC.Sonya Lunder, MPH, senior analyst, Environmental Working Group.News release, North American Metal Packaging Alliance.CDC: "BPA Fact Sheet."U.S. Department of Health & Human Services: "BPA Information for Parents."FDA: "Update on Bisphenol A for Use in Food, January 2010."
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