Plastics chemicals stay in body3rd February 2009
The plastics chemical bisphenol A (BPA) may remain in the body much longer than anyone realised.
People are widely exposed to it, because it is found in everything from PVC pipe to drink containers, aluminum cans, and dental sealants.
Basing their conclusions on limited evidence, most scientists had assumed that the body excretes BPA within 24 hours of exposure.
Scientists have not worried about dietary BPA, since exposure to it is assumed to come only from food, and since the half-life of the molecule is short.
This comes just several months after the Canadian government banned the use of BPA in plastic baby bottles.
Since then, several companies have stopped using the chemical entirely.
In order to find out more about the health effects of BPA, Richard Stahlhut analysed data in adults from the CDC's 2003/04 NHANES study.
NHANES researchers gave BPA to subjects who had been fasting. They were allowed to drink water, black coffee, and diet soda.
Stahlhut compared the BPA levels of the subjects to how long they had gone without food. He said that after 10 to 15 hours of fasting, there should not have been anybody with any detectable levels of BPA.
He said that the BPA remained in their bodies for over 24 hours, and though it showed a subtle downward trend, it was not possible to predict when it would be gone.
John Cienki of the University of Miami said that he thinks researchers are misusing the data.
He said that scientists would anticipate a greater BPA excretion if people were fasting, though the NHANES study did not control for consumption of or exposure to BPA.
Stahlhut agrees with Cienki, noting that drinking water testing has been lacking at best, since the tests performed did not look for chlorinated BPA, the most likely form of BPA to be leached from PVC pipes.
Stahlhut's other idea, supported by several studies, is that the BPA may not have been ingested in the form of fluids consumed during the study, and that it stays inside fat tissues.
This could be a problem, because researchers have found a link between high levels of BPA in the body and a higher risk of disease.
Another study showed that average levels of BPA disrupt a hormone involved in diabetes, and yet another study showed that obese people whose fat stores high amounts of chemical food additives have a much higher risk of diabetes.
Stalhut says that it is important to discover whether or not these conditions are caused by persistent organic compounds in the fat of obese people.
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