Al. Stinchcomb et al., Chemical uptake into human stratum corneum in vivo from volatile and non-volatile solvents, PHARM RES, 16(8), 1999, pp. 1288-1293
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.