In vitro human skin permeation of benzene in gasoline: Effects of concentration, multiple dosing and skin preparation

Abstract

In vitro human skin benzene permeation was measured from gasoline formulations with benzene concentrations ranging from 0.8 to 10 vol% and from neat benzene. Steady-state fluxes (J SS), permeability coefficients (k p) and lag times (t lag) were calculated from infinite dose exposures. Permeation of benzene from small gasoline doses administered over a two-day period was also studied. The thermodynamic activity of benzene in gasoline at 30 °C was determined and the solution is near-ideal over the range from 0.8 to 100 vol%. J SS through human epidermal membranes were linear (R 2 =0.92) with concentration over the range from 0.8 to 10 vol%. J SS (μg/cm 2 /h) from gasoline (0.8 vol% benzene=6.99 mg/ml) through epidermis and full-thickness skin were 9.37±1.41 and 1.82±0.44, respectively. Neat benzene J SS was 566±138. Less than 0.25% of the total applied benzene mass from finite doses (10 μl/cm 2) of gasoline was detected in receptor cells, and a small reduction of barrier function was observed from six total doses administered over 2 days. Application of these results to dermal exposure assessment examples demonstrates a range of systemic benzene uptakes that can be expected from occupational and consumer dermal exposures to gasoline, depending on the type and extent of exposure.