A quantitative approach to evaluate urinary benzene and S-phenylmercapturic acid as biomarkers of low benzene exposure

Context: Benzene is a ubiquitous pollutant; smoking habit, genetic polymorphisms, and analytical difficulties impact the identification of the best biomarker. Objective: To apply a systematic quantitative approach to evaluate urinary benzene (BEN-U) and S-phenylmercapturic acid (SPMA) as biomarkers of low benzene exposures. Methods: Seventy-one blue collar refinery workers, 97 white collar refinery workers and 108 general population subjects were included. Intrinsic characteristics, sampling and analytical issues were compared. Results: BEN-U and SPMA were detected in 99% and 78% of samples, which correlated with benzene exposure (r=0.456 and r=0.636, respectively) and with urinary cotinine (r=0.630 and r=0.570, respectively). Intrinsic characteristics were similar for the two biomarkers: specificity (0.64 and 0.69 for BEN-U and SPMA), sensitivity (0.74 and 0.83), as well as intra- and inter-individual variability (150% and >14 for both). Conclusion: BEN-U and SPMA show similar intrinsic characteristics; analytical issues in detecting SPMA suggest that BEN-U is more convenient for investigating low exposure levels.