An optimized sampling and GC-MS analysis method for benzene in exhaled breath, as a biomarker for occupational exposure

Benzene is known to be toxic and carcinogenic: therefore, in case of exposure to benzene vapours, a reliable biological monitoring procedure is needed, particularly in the field of occupational hygiene. The determination of the concentration of benzene in the exhaled air 8 h after the exposure has been demonstrated to be a significant biomarker, even for low concentrations of airborne benzene vapours. This work presents a sampling and analysis method that optimizes previously described procedures: in the sampling phase, a double-step sample collection in Tedlar bags is used, in order to remove the breath moisture and to standardise the sample volumes. The analytical phase uses a cryogenic trap for the concentration of the air samples to be injected in the GC-MS, without the need for trapping materials, significantly reducing time and costs of the analysis and improving sensitivity. The presented method has been successfully applied to the biological monitoring of a mixed population (occupationally exposed and not exposed subjects, smokers and non-smokers), with a lower detection limit of 1.5 ng of benzene per litre of exhaled air, that is 1/200 of the biological exposure index recommended by the American Conference of Governmental Hygienists.