MEASUREMENT OF BENZENE IN HUMAN BREATH ASSOCIATED WITH AN ENVIRONMENTAL EXPOSURE

The concentration of benzene in breath was measured after exposure to environmental benzene. Five volunteers were exposed to environmental t obacco smoke at different exposure levels and for different exposure d urations. The breath samples were collected before, during, and postex posure for up to three hours. Benzene in breath was confirmed as a sho rt-term biomarker of environmental benzene exposure at the sub-ppm lev el. Less than 10% of the inhaled benzene was expired within three hour s following two-hour inhalation exposures, with a greater percentage e xpired following shorter exposures. An average of 64% percent of the i nhaled benzene was absorbed through the lung barrier, with the percent age absorbed decreasing with continued exposure. Benzene biological ha lf-lives of 7.6 and 68 minutes were calculated empirically using a two -compartment model based on the exponential benzene decay curve after correcting the breath concentrations for background breath concentrati ons. The breath concentration calculated at the end of the exposure by extrapolation of the postexposure breath samples demonstrates a disco ntinuity with the breath concentration collected during exposure, cons istent with equilibrium exchange between blood and breath.