A new experiment with dogs finds that Bisphenol-A (BPA) can be absorbed in the mouth and pass directly into the bloodstream, just as nitroglycerin under the tongue. This way it bypasses detoxification in the liver after absorption in the gut. The result is that much more biologically active BPA is available to possibly cause health effects, with major implications for how much risk BPA may pose for human health.
2013 Study Abstract
Bisphenol A (BPA) risk assessment is currently hindered by the rejection of reported higher than expected BPA plasma concentrations in humans after oral ingestion. These are deemed incompatible with the almost complete hepatic first-pass metabolism of BPA into its inactive glucurono-conjugated form, BPA glucuronide (BPAG).
Using dogs as a valid model, plasma concentrations of BPA were compared over a 24-h period after intravenous, orogastric and sublingual administrations, in order to establish the absolute bioavailability of BPA administered sublingually and to compare it with oral bioavailability. Methods: Six dogs were sublingually administered with BPA at 0.05 mg/kg and 5mg/kg. The time course of plasma BPA concentrations was compared with that obtained in the same dogs after intravenous administration of the same BPA doses and after a 20mg/kg BPA dose administrated by orogastric gavage.
The data indicated that the systemic bioavailability of BPA deposited sublingually was high (70-90%) and that BPA transmucosal absorption from the oral cavity led to much higher BPA internal exposure than obtained for BPA absorption from the gastro-intestinal tract. The concentration ratio of BPAG to BPA in plasma was approximately 100-fold lower following sublingual administration than after oral dosing enabling the two pathways of absorption to be easily distinguished.
These findings demonstrate that BPA can be efficiently and very rapidly absorbed through the oral mucosa by the sublingual route. This efficient systemic entry route of BPA may lead to far higher BPA internal exposures than known for BPA absorption from the gastrointestinal tract.
- Read BPA is absorbed in the mouth; could explain high blood levels, by John Peterson Myers, EHN, Jun 19, 2013.
- Sources: High Bioavailability of Bisphenol A from Sublingual Exposure, Environmental Health Perspectives, 12 June 2013, Full PDF.
- Related post: Endocrine Disruptors and why the toxic Chemical #BPA has not been banned by the #FDA yet.
- Our tags BPA – Endocrine Disruptors – Pesticides – Phthalates.