In vitro percutaneous absorption of benzene in human skin.

The in vitro percutaneous absorption of carbon-14-labeled benzene ([(14)C]benzene) in dermatomed human skin was determined using 2 cleaning products containing benzene. This study utilized cleaning solutions commonly used in the workplace. As Environmental Protection Agency (EPA) guidelines cover dose occlusion for volatile chemicals, the treatments were both nonoccluded and occluded, with low (10 microL/cm(2)), high (30 microL/cm(2)), and multiple (10 microL/cm(2) x 3 at 0, 30, and 60 min) doses. In an open-to-air test, the benzene quickly evaporated, and only 0.5%-1.4% of the original dose remained after 30 minutes. In the diffusion studies, human skin absorption of benzene peaked in the first few hours without occlusion, but was sustained for 24 hours with occlusion. The absorption of a high single dose was 1.2 +/- 0.16 times (mean +/- standard deviation) greater than that of a multiple dose, whereas theory would predict 1.0. The low-dose to high- or multiple-dose ratio was 3.6 +/- 2.2, so there was a clear dose response. The effect of occlusion was significant. In this study occlusion increased absorption by 40.1 +/- 24.6 times. These data place into partial perspective the role of occlusion in benzene flux, but should not be generalized until other volatile substances are studied in the experimental system and further validated with in vivo systems.