Exhaled breath analysis as a measure of workplace exposure to benzene ppm

Exposures to benzene vapour were measured in a group of coal tar distillation workers and the concentration of benzene in the air that they exhaled was determined at the beginning of the following work period. Time-weighted average benzene concentrations were principally in the range 0.02-0.9 ppm. Benzene vapour was detectable in the breath of all subjects 16 h after exposure, and a progressive build-up over the working week was found. Nevertheless the relationship between exposure and concentration in exhaled breath was found to be poor. This suggests that at concentrations below about 1 ppm, the analysis of exhaled breath is not a reliable method of measuring previous exposure to benzene.