Methodological issues in biomonitoring of low level exposure to benzene

Data from a pilot study on unmetabolized benzene and Irans, trans muconic a cid (t,t-MA) excretion in filling station attendants and unexposed controls were used to afford methodological issues in the biomonitoring of low benz ene exposures (around 0.1 ppm). Urinary concentrations of benzene and t,t-M A were measured by dynamic head-space capillary GC/FID and HPLC, respective ly. The accuracy of the HPLC determination of t,t-MA was assessed in terms of inter- and intra-method reliability. The adequacy of urinary t,t-MA and benzene as biological markers of low benzene exposure was evaluated by anal ysing the relationship between personal exposure to benzene and biomarker e xcretion. Filling station attendants excreted significantly higher amounts of benzene, but not of t,t-MA, than controls. Adjusting for occupational be nzene exposure, smokers excreted significantly higher amounts of t,t-MA, bu t not of unmetabolized benzene, than nonsmokers. A comparative analysis of the present and previously published biomonitoring surveys showed a good in ter-study agreement regarding the amount of t,t-MA and unmetabolized benzen e excreted (about 0.1-0.2 mg/l and 1-2 mu g/l, respectively) per unit of ex posure (0.1 ppm). For each biomarker, based on the distribution of paramete rs observed in the pilot study, we calculated the minimum sample size requi red to estimate the population mean with given confidence and precision.