Taking into account the characteristics of skin samples for better estimating percutaneous absorption flows

The percutaneous route represents the second occupational exposure route for numerous industrial toxic substances. The word “Skin notation” appears whenever the contribution from this route to the total absorption by the body represents at least 10%. Estimating percutaneous passage as accurately as possible thus constitutes an essential part of assessing occupational risks and, therefore, of protecting workers at the workstation.

Experimental results obtained ex vivo in rats and in humans have shown that, for exposure conditions that are, a priori, identical, the measured percutaneous absorption flow can fluctuate considerably (by a factor of 10 in humans). When the flow of the same molecules is determined in vitro in artificial membranes made of silicone, the values obtained are highly reproducible. Therefore, one or more factors inherent to the samples themselves or to the way they are prepared influence the absorption flow.

During this study, we propose to correlate the percutaneous flow with the characteristics of the skin that are determined on the basis of histological sections, and, in particular, the thicknesses of the various cutaneous layers (stratum corneum, viable epidermis, and dermis). This should make it possible to reduce the variability observed in measuring the flow of certain molecules and thus to give a better estimation of the absorption flows measured ex vivo.

The results of this study should be the subject of two scientific publications, firstly on the influence of various parameters on the structure of the skin, and secondly on standardisation of the absorption flow as a function of the structure of the skin.