Bisphenol A May Linger in Body
Study Shows More Than Expected Amounts of BPA May Accumulate in Americans' Bodies
The BPA could have come from the diet soda or other things the CDC researchers couldn't control, points out University of Miami medical toxicologist John Cienki, MD. Cienki, who was not involved in the Stahlhut or NHANES studies, says he worries about BPA. But he warns that there are too many unknowns in the NHANES data to draw any definite conclusions.
"I think we are using data here that was not designed to be used this way," Cienki cautions. "Yes, we would anticipate a greater BPA excretion if people were fasting -- if they had not continued to ingest BPA. But this study did not control for consumption of or exposure to BPA."
Stahlhut fully agrees. However, he notes that the BPA could have come from another source: tap water. Surprisingly few BPA tests have been done on tap water. And those tests did not look for chlorinated BPA, which would be the form of BPA leached from PVC pipes into municipal tap water.
Or maybe, Stahlhut says, not all the BPA was being ingested. Maybe a lot of it really lingers in fat tissues, as some studies suggest. And far from being a stored harmlessly, BPA may be a bad actor in human fat.
A 2008 study in the Journal of the American Medical Association showed that people with higher urinary BPA levels have more medical disorders. Another intriguing study from 2008 showed that BPA -- at normal levels of exposure -- disrupts a hormone involved in insulin sensitivity and diabetes. And a 2007 study showed that obese people are much more likely to suffer insulin resistance if they have high fat levels of organic pollutants.
"Imagine if what we think is caused by obesity is actually caused by persistent organics in the fat of obese people," Stahlhut says. "If they don't have the organics, they don't have the diabetes. That would be huge."
But first things first. Stahlhut agrees with Cienki that his study is not grounds for any kind of regulatory action. He calls for rigidly controlled experiments to find out what happens to people after long-term exposure to BPA. He also urges studies measuring BPA in human fat tissues. And he thinks it's urgent to search for new, potentially important sources of BPA exposure.
Stahlhut and colleagues report their findings in the Jan. 28 online issue of Environmental Health Perspectives.