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BPA Through Oral Route Remains Active

In a study using dogs, scientists observe direct absorption of bisphenol A from the mouth into the bloodstream

by Stephen K. Ritter
July 1, 2013 | A version of this story appeared in Volume 91, Issue 26

Experiments with dogs have found that the controversial chemical bisphenol A (BPA) can be absorbed under the tongue and pass directly into the bloodstream. Proof of this exposure route, not shown conclusively until now, suggests that higher levels of BPA may persist in the body than previously thought and be available to do harm (Environ. Health Perspect. 2013, DOI: 10.1289/ehp.1206339). BPA is a synthetic building block used to make the polycarbonate plastics and epoxy resins used in food containers and a host of other products. Animal studies have shown that BPA mimics the action of hormones and that the trace amounts that people are exposed to may be contributing to health problems such as diabetes and heart disease. But the human health risk from BPA exposure remains murky because of uncertainty in how it enters the bloodstream. During digestion, BPA passes through the gastrointestinal tract and is metabolized in the liver. Via that route, most BPA is conjugated to glucuronic acid to create an inactive species that is excreted. Animal studies to test BPA and other chemicals tend to use feeding tubes or other methods to control the dose, an approach that bypasses direct absorption through the mouth. A research team led by Pierre-Louis Toutain at Toxalim Research Centre in Food Toxicology, in Toulouse, France, administered BPA to dogs by mouth, by feeding tube, and intravenously and found that BPA absorption under the tongue leads to the highest levels of unmetabolized BPA in the blood. The researchers believe their findings will have “major implications” in interpreting human biomonitoring data and making chemical risk assessments.


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