BPA Plastic May Stay In Body Longer
The study was the work of researchers at the University of Rochester Medical Center, Rochester, New York, and the University of Missouri-Columbia, and was published online before print on 28 January in the journal Environmental Health Perspectives.
BPA is used to harden plastics in many types of products, including baby bottles and water bottles. It is also used in PVC water pipes and as a coating inside metal food cans, and to make dental sealant.
The authors wrote that studies have suggested BPA may harm the brain and prostate glands in developing fetuses and babies, and a JAMA paper published in September 2008 found higher heart disease and diabetes risks among adults with higher levels of BPA in their urine.
Last month, the US Food and Drug Administration (FDA) agreed to reconsider the health risks of BPA.
Two of the reasons the FDA and their European counterpart, the European Food Safety Authority, have declared BPA to be safe is because the authority view in science is that the chemical is eliminated quickly from the body and the main source of exposure is food containers. However, this latest study questions both of these key assumptions.
Lead author Dr Richard W Stahlhut explained:
"Our results simply do not fit that picture."
"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," said Stahlhut, who works at the University of Rochester's Environmental Health Sciences Center.
For the study, Stahlhut and colleagues used data on 1,469 US adults who took part in the Center for Disease Control's (CDC's) National Health and Nutrition Examination Survey (NHANES). From this they could examine links between levels of BPA in people's urine and how long they had fasted before giving their samples.
If, as many scientists assumed, the main route for BPA to enter the body was through food and beverages, then the researchers expected to see clear relationships between fasting times and levels of BPA; ie the lowest levels should be in the urine of people who had fasted the longest. In fact, they expected the levels to halve for every additional 5 hours of fasting.
But what they found was the people who had fasted the longest had urine levels of BPA that were only moderately lower than people who eaten just before giving their sample.
Stahlhut described their unexpected result:
"In our data, BPA levels appear to drop about eight times more slowly than expected -- so slowly, in fact, that race and sex together have as big an influence on BPA levels as fasting time."
He and colleagues suggested two reasons for their findings. First, BPA might have entered the body by other means, for instance via house dust or tap water, and secondly, perhaps it got into fat tissue from which it is released more slowly.
They said further research was needed to evaluate how BPA might affect the way fat tissue hormones work and to look for other non-food sources of BPA exposure.
According to CDC estimates, over 90 per cent of Americans have detectable levels of BPA in their urine.
The University of Rochester School of Medicine and Dentistry, and the National Institute of Environmental Health Sciences Training Grant, paid for the research.
"Bisphenol A Data in NHANES Suggest Longer Than Expected Half-Life, Substantial Non-Food Exposure, or Both."
Richard W. Stahlhut, Wade V. Welshons, and Shanna H. Swan.
Environmental Health Perspectives, In press, Online version available 28 January 2009.
Click here for pre-press view of Abstract (PDF donwload).
Sources: Journal abstract, University of Rochester Medical Center press release.
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