Reassessment of the experimental skin permeability coefficients of polycyclic aromatic hydrocarbons and organophosphorus pesticides

Abstract

Human exposure to polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) by dermal route is a continuing concern in environmental and occupational toxicology. Diverse authors have measured in vitro the absorption flux and permeability coefficient (kP) of those compounds delivered on skin surface using volatile solvents. However, there isn’t a harmonized method to obtain kP when the test substance is deposited on the skin as a solid. Consequently, varied experimental kPs have been reported for PAHs and OPPs, most in clear disagreement with the values predicted by well-established mathematical models. In this work, we collected the permeation fluxes reported for these toxicants through human skin and calculated the (aqueous) kPs using a method based on the maximum flux and water solubility. The reanalyzed fluxes and recalculated kPs show improved consistency between the different experimental works and mathematical models. Notably, the recalculated kP of benzo[a]pyrene, among others, was approximately 100 times higher than it had been previously considered. Suggestions are given to generalize the method in studies with other solvent-deposited toxicants and drugs.