Bisphenol A (BPA) is a compound that is widely used in the industrial production of polycarbonate plastic containers such as baby bottles. It is also found in the resins of the plastic liners of canned foods and beverages. However, BPA can spontaneously leach out of these plastics and resins at very low doses and contaminate the food or drink in the container, especially if the container is hot. It has been found in the urine, blood, and amniotic fluid of a large majority of Europeans. In this regard, the European Food Safety Authority (EFSA) and the French Food Safety Agency (AFSSA) - now part of the French agency for food, environmental and occupational health safety - have set a tolerable daily intake (TDI) of 0.05 mg/kg body weight for BPA.
However, when the theoretical exposure of the population was calculated (by extrapolating the amount of BPA present in food), scientists noticed that measurements of BPA residues in human tissues did not match up. For this reason, several experts in the field suspected that there were other sources of BPA exposure, especially through the skin. Indeed, BPA is found as a free monomer in many thermal papers used in small printers (credit card and cash register receipts, etc.). It is used as a color developer during printout and, as a result, is present in relatively large amounts.
In August 2010 (1), a team of American researchers reported that cashiers had higher residual BPA levels.
INRA-Toulouse researchers, in collaboration with the Pierre Fabre laboratories, have demonstrated for the first time that the skin is probably another entry point into the body for BPA. With this in mind, they developed an ex vivo study model using viable pig skin explants (2) in order to analyse the passage of chemicals upon contact with tissue. They found that about two-thirds of the BPA deposited on the surface of the pig ear skin explants penetrated the skin barrier regardless of dose (50 to 800 nmoles). Later, a comparison was made using human skin explants, and the scientists obtained similar results.
These new data, as well as the fact that contamination from food alone could not account for the BPA levels found in certain individuals, strongly suggest that the molecule can pass through skin and enter the body.
INRA-Toulouse researchers already demonstrated in 2009 that rat intestinal tracts were higly sensitive to low doses of BPA, which affected intestinal permeability, and that pre- and post-natal exposure of rats to BPA could undermine the "intestinal barrier" function during adulthood.
These findings open new avenues in the assessment of exposure risks to endocrine disruptors, particularly BPA. BPA mimics the effects of oestrogens, the female sex hormones that not only play a crucial role in reproduction, but are also essential to the development of organs such as the brain or the cardiovascular system. The full results are published in the advanced online edition of the 27 October 2010 issue of Chemosphere.
Reference:
Viable skin efficiently absorbs and metabolizes bisphenol A. Chemosphere, online : doi:10.1016/j.chemosphere.2010.09.058.
Daniel Zalkoa, Carine Jacquesa, Hélène Duplanb, Sandrine Bruela, Elisabeth Perdua
a INRA, UMR1089 Xénobiotiques, 180 Chemin de Tournefeuille, BP 93173, 31027 Toulouse Cedex 3, France
b Pierre Fabre Dermo-cosmétique, Laboratoire de Pharmacocinétique Cutanée, Allée Camille Soula, BP 74, 31322 Vigoulet, France
1Braun et al, 2010
2Pig skin has strong physiological and morphological similarities to human skin.
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