It’s all BPA all the time in the media, and today’s example of reporters not knowing biological pathways from their elbows comes from the Los Angeles Times. The reporter, who doesn’t appear to be on staff, writes the following about Bisphenol A, or BPA as its known for short, a component of polycarbonate plastic and other products:
The possibly bad news is that BPA doesn’t always stay put. The chemical acts a lot like estrogen if it’s introduced into the body — and evidence now shows that this happens to just about everybody every day.”
Except, it doesn’t! As every risk assessment compiled on BPA notes at some point, BPA is, in fact, rapidly broken down first in the gastrointestinal tract (GI) and then in the liver by enzymes which add a sugar molecule to BPA, transforming it into a water soluble BPA-glucuronide. BPA-glucuronide is, as the European Food Safety Authority’s risk assessment notes, “devoid of endocrine activity.” In other words, once BPA is broken down, it is not estrogenic in the body.
And being water soluble, BPA-glucuronide is easily excreted in urine. This happens very quickly. The half life of BPA-glucuronide is six hours. There is a minor metabolic pathway in which some BPA is converted to a sulfate, but this is also water soluble and quickly excreted as a metabolite. In adult human volunteer studies, no free or parent BPA is found in blood. There is 100 percent conversion to a metabolite.
This is partly the reason why so many of the studies claiming to find a risk from BPA have been rejected by risk assessments in Europe, Japan and the U.S.: they inject BPA into rodents, and the result, metabolically, is different.