Abstract
Polycyclic aromatic hydrocarbons (PAHs) are a group of significant contaminants in occupational and living environment. In addition to the inhalation route of exposure in occupational environment, there is also significantly applied dermal route of exposure.
The existing experimental data on intensity and rate of penetration of these substances into systemic circulation are still limited. The presented paper is focused on methodological and interpretative issues of trans-epidermal absorption of PAU in vitro.
In this study, we assessed intensity (Flux) and rate (Lag time) of penetration of naphthalene, phenanthrene, pyrene and benzo[a]pyrene through the epidermal membrane derived from a pig ear. The experiment was performed using the static vertical Franz diffusion cells (n = 32) and the isopropyl myristate was used as a solvent.
The Flux (nmol/cm2/hour) reached 95.7+-45.5 in case of naphthalene, 19.5+-8.7 of phenanthrene, 4.38+-1.98 of pyrene and 0.21+-0.08 of benzo[a]pyrene. The Lag time (hour) was 0.26+-0.17 in case of naphthalene, 2.12+-0.41 of phenanthrene, 3.25+-0.50 of pyrene and 11.2+-4.08 of benzo[a]pyrene.
The value of the Flux decreased with the molecular weight of PAHs, while the Lag time increased with the molecular weight of PAHs. The amount of PAHs that penetrated through epidermal membrane in a given time period ranged between 0.24 % (benzo[a]pyrene) and 0.84 % (phenanthrene) of applied dose.
The penetration of PAHs through the epidermal membrane showed a lower degree of data variability compared to the full thickness skin experiments. The results suggest that the use of the epidermal membrane could define more accurately both the estimation of the internal dose of PAHs after dermal exposure and the estimation of the associated health risk within a conservative exposure scenario.
However, experiments with using the epidermal membrane are time consuming and experimental demanding, with no option of an objective control of the integrity of the epidermal membrane, which can lead to costly testing, loss of samples and, finally, an increase in the differences in data values obtained in different laboratories.