Chemical uptake into human stratum corneum in vivo from volatile and non-volatile solvents

Purpose. Simple, safe and quick in vivo methods for estimating chemical upt ake into the stratum corneum (SC) from volatile and non-volatile solvents a re invaluable to health risk assessors. This study compares the human in vi vo SC uptake of a model compound (4-cyanophenol) from water and acetone usi ng quantitative attenuated total reflectance-Fourier transform infrared (AT R-FTIR) spectroscopy. Methods. Small areas on the ventral forearms of human volunteers were treat ed with 4-cyanophenol (CP) dissolved either in water or acetone. After the skin was cleansed of remaining surface CP, SC samples were taken by a stand ard tape-stripping method. CP concentration profiles across the SC were qua ntitated by direct measurement of the permeant on the individual tape-strip s using ATR-FTIR. Results. Increasing the duration of exposure to CP aqueous solutions result ed in increasing CP uptake into the SC; the kinetics of uptake correlated w ell with predictive diffusion equations. Increasing the 'dose' of CP in ace tone also resulted in increasing uptake into the SC, but uptake eventually plateaued at a maximum level. The amount of CP taken up into the SC from ac etone was 2 to 8-fold greater than that from water following similar short- time exposures. Conclusions. These safe, simple experimental methods provide practical and predictive assessments of chemical uptake into human SC in vivo.