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In 2010, researchers from the INRA's Research Centre in Food Toxicology, TOXALIM showed that bisphenol A (BPA) could enter the body through the skin. Now, another team from the same research unit (INRA and the École Nationale Vétérinaire de Toulouse) has shown for the first time in animals that BPA can be directly absorbed in the mouth through the sublingual mucosa (the membrane of the ventral surface of the tongue and the floor of the mouth).

• The results show that BPA is absorbed through the sublingual mucosa (a highly-vascularised area) and goes directly into the bloodstream.
• Researchers have demonstrated that when BPA absorption takes places in the mouth, the levels in the blood are nearly 100 times higher than those expected when the same amount of BPA is absorbed through the intestines.
• The resulting bioavailability of BPA via the sublingual route (70-90%) greatly exceeds that resulting from BPA absorption from the gastro-intestinal tract (below 1% in the study).

When BPA absorption takes place in the gut, all the BPA absorbed is drained into the liver where it is extensively converted into BPA-glucuronide, a harmless substance eliminated through urine; BPA absorbed through the mouth can enter the bloodstream directly avoiding this physiological metabolization process. If scientists confirm the passage of BPA through the mouth in humans (depending on how long the substance remains in the mouth), this means BPA entering the mouth could enter the bloodstream directly. Additional studies should offer insights on how this new pathway of contamination could contribute to overall exposure, thereby increasing understanding about the relationship between BPA exposure and blood concentration levels in the general population, a key element in human health risk assessment.

This work has been published in Environmental Health Perspectives

Véronique Gayrard, Marlène Z. Lacroix, Séverine H. Collet, Catherine Viguié, Alain Bousquet-Melou, Pierre-Louis Toutain, Nicole Picard-Hagen. High Bioavailability of Bisphenol A from Sublingual Exposure. Environmental Health Perspectives, 12 June 2013