Benzylmercapturic acid is superior to hippuric acid and o-cresol as a urinary marker of occupational exposure to toluene

Abstract The present study was initiated to examine whether urinary benzylmercapturic acid (or N -acetyl- S -benzyl cysteine, BMA), a mercapturate metabolite of toluene, increases in relation to the intensity of toluene exposure, and whether this metabolite is a better marker of occupational exposure to toluene than two traditional markers, hippuric acid and o -cresol. Accordingly, end-of-shift urine samples were collected from 122 printers and 30 office clerks (all men) in the second half of a working week. Solvent (toluene) exposure of the day (8 h) was monitored by means of diffusive sampling. Quantitative relation with toluene showed that BMA had a greater correlation coefficient with toluene ( r =0.7) than hippuric acid ( r =0.6) or o -cresol ( r =0.6). The levels in the urine of the non-exposed control subjects were below the detection limit of 0.2 μg/l for BMA, whereas it was at substantial levels for hippuric acid and o -cresol (239 mg/l and 32 μg/l as a geometric mean, respectively). Thus, BMA, hippuric acid and o -cresol could separate the exposed from the non-exposed when toluene was at o -cresol as a marker of occupational exposure to toluene.