Empirical relations predicting human and rat tissue : air partition coefficients of volatile organic compounds

Based on the hypothesis that tissue partitioning of volatile organic compou nds (VOCs) is due to lipophilic and hydrophilic interactions with tissue co mponents, empirical relations are established between olive oil (P-oil:air) , saline (P-saline:air), and tissue partition coefficients (P-tissue:air) f or human and rat tissues. Reported values of partition coefficients of a wi de range of VOCs With distinct chemical structures (n = 137) have been comp iled from the literature. Bilinear regression analysis shows that partition coefficients of VOCs in human blood, brain, fat, liver, kidney, and muscle tissues are well described by a linear combination of P-oil:air and P-sali ne:air with tissue-specific regression coefficients. The regression coeffic ient associated with the hydrophilic component of VOC partitioning in rat t issues is systematically higher than that of human tissues. For the human m odel, tissue concentrations calculated from predicted partition coefficient s are generally within a factor 4 of tissue concentrations calculated from experimentally observed partition coefficients. These results demonstrate t hat, without prior knowledge of tissue composition, it is possible to obtai n estimates of human tissue partition coefficients of VOCs with an accuracy that is in the same range as that commonly used in risk assessment. (C) 20 00 Academic Press.