29 January 2009
Fresh concerns about BPA
by Kate Melville
Common assumptions about the controversial chemical bisphenol A (BPA) may be wrong, with new research showing that high levels of BPA remain in the body even after fasting for as long as 24 hours, suggesting that BPA exposure may come from non-food sources, or, that BPA is not rapidly metabolized, or both. The new research was carried out by scientists from the University of Rochester Medical Center and their findings were published in the journal Environmental Health Perspectives.
Prior to these new findings, the FDA had already agreed to reconsider the health risks of the chemical, which is used to make plastic baby bottles, water bottles and many other consumer products. A number of scientific studies in the past have implicated BPA with damage to the brain and prostate glands in developing fetuses and infants; and adults with higher BPA levels in their urine were linked to higher risks for heart disease and diabetes.
The latest finding from Rochester is important because, until now, scientists believed that BPA was excreted quickly and that people were exposed to BPA primarily through food. Indeed, the FDA and the European Food Safety Authority have declared BPA safe based, in part, on those assumptions. "Our results simply do not fit that picture," said lead author Richard W. Stahlhut, of the University of Rochester's Environmental Health Sciences Center. "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."
Working with data from the Center for Disease Control's National Health and Nutrition Examination Survey, Stahlhut sought to explore the link between BPA urine concentration and the length of time a person had been fasting. Accepting the widely held assumption that food is the most common route of exposure to BPA, he expected to see a relationship between the last food ingested, fasting time, and BPA levels. People who had fasted longest (15 to 24 hours), for example, should have had much lower BPA levels than people who had eaten more recently, Stahlhut said.
Instead, those who fasted had levels that were only moderately lower than people who had just eaten. This is significant because scientists expected BPA levels to decrease by about half, every five hours. "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," Stahlhut noted.
He believes two possible explanations may exist for the higher-than-expected levels of BPA in people who fasted. One is that exposure to BPA might come through other means, such as house dust or tap water. In addition, Stahlhut theorizes that BPA may seep into fat tissues, where it would be released more slowly. However, further study is needed to evaluate the effects of BPA on adipose tissue hormones and function, Stahlhut said, as well as more studies to compare BPA levels in fat versus blood and urine.
Source: University of Rochester Medical Center