Benzene in blood as a biomarker of low level occupational exposure

The occupational airborne exposure to benzene of 150 workers employed in petrol stations and a refinery plant was assessed using personal sampling pumps. All workers provided blood samples after the end of work and on the following morning before resuming work. Benzene concentrations in the blood of 243 non-occupationally-exposed subjects were also measured. The median occupational benzene exposure for all 150 workers studied was 80 mgrm3. Overall median blood benzene of all workers was 251 ngrl at the end of the shift, and 174 ngrl the following morning. The benzene concentrations measured in blood collected the following morning proved to be significantly lower than those measured at the end of the shift. Median blood benzene for the 243 ‘normal’ subjects was 128 ngrl, which was significantly lower than that measured in the workers before a new work shift. The median blood benzene concentration was significantly higher in smokers than in non-smokers, both in the general population 210 ngrl vs. 110 ngrl. and in the exposed workers at the end of the shift 476 ngrl vs. 132 ngrl. and the following morning 360 ngrl vs. 99 ngrl.. End-of-shift blood benzene correlated significantly with environmental exposure; this correlation was better in the 83 non-smokers than in the 67 smokers. In non-smokers with the median benzene occupational exposure of 50 mgrm3, no difference was found in blood benzene concentration in exposed and non-exposed subjects.