The bioavailability of metals, which are known as important contact allergens, is decisive for the development
and the maintenance of contact dermatitis. The aim of this study was to evaluate the percutaneous
penetration of metal powders of cobalt (Co), nickel (Ni) and chromium (Cr) and the effect of skin
lesions on skin absorption. In vitro permeation experiments were performed using the Franz diffusion
cells with intact and damaged human skin. Physiological solution was used as receiving phase and metal
powders (Co, Ni and Cr) dispersed in synthetic sweat at pH 4.5 were applied as donor phase to the outer
surface of the skin for 24 h. The amount of each metal permeating the skin was analysed by electro-thermal
atomic absorption spectroscopy (ETAAS). Donor solution analysis demonstrated that metals were
present as ions. Measurements of metals skin content were also exploited. Median Co and Ni concentrations
found in the receiving phase were significantly higher when Co and Ni powders were applied on the
abraded skin than after application on the intact skin (3566 and 2631 ngcm2 vs. 8.4 and 31 ngcm2,
respectively). No significant difference was found in Cr permeation through intact and damaged skin.
The measurement of metals skin content showed that Co, Ni and Cr concentrations were significantly
higher in the damaged skin than in the intact skin. Co and Ni ions concentrations increased significantly
when the donor solutions were applied on the damaged skin, while Cr ions concentrations did not
increase. This study demonstrated that Co and Ni powders can permeate through damaged skin more
easily than Cr powder, which has probably a stronger skin proteins binding capacity. Therefore, our
results suggest that is necessary to prevent skin contamination when using toxic substances because a
small injury to the skin barrier can significantly increase skin absorption.
