Methods and Measurements for Estimating Human Dermal Uptake of Volatile Organic Compounds and for Deriving Dermal Permeability Coefficients

ABSTRACT

Water contamination of public drinking and recreational waters with volatile organic compounds (VOCs) is widespread, resulting in human exposure through multiple routes. Although dermal absorption is of considerable importance, there is great uncertainty in the dermal permeability coefficient (K_P) for many VOCs due to the methods by which they are derived. We present a human in vivo experimental approach for the measurement of VOC dermal uptake from water contaminated at environmentally relevant concentrations and for determination of K_P. Dermal permeability was estimated from 11 adult subjects following immersion of their hand and forearm into a sealed 4.8-L Plexiglas cylinder containing 100 μg/L each of chloroform, 1,1,1-trichloroethane (111-TCA), and toluene and 400 μg/L of methyl tertiary butyl ether (MTBE) in water. Uptake was determined by measuring the decrease in VOC water concentration during the exposure. A control glass arm accounted for nondermal losses. The concentration of VOCs was determined by solid-phase microextraction (SPME) and analysis with gas chromatography/mass spectrometry. For the eight male and three female adult subjects, on average there was a dermal uptake-attributed 13.5%, 14.9%, 20.8%, and 7.3% decrease in the concentration after 1 h exposure for chloroform, 111-TCA, toluene, and MTBE, respectively. The resulting mean K_P (standard deviation) was estimated to be 0.166 (0.108), 0.167 (0.107), 0.250 (0.064), and 0.109 (0.157) cm/h for the respective analytes. The experimental K_P values presented here exceed the previously published model-estimated K_P values by factors ranging from 6 to 57, suggesting that the published model-estimated K_P values may underestimate actual VOC dermal absorption from water.

KEYWORDS :

• Dermal Exposure
• Permeability Coefficient
• Uptake
• VOCs
• Human In Vivo
• Risk
• Uncertainty