Urinary excretion of thioethers related to styrene exposure

The objective of this study was to test the suitability of styrene-specific mercapturic acids as urinary bioindicators of occupational styrene exposure. The excretion of mandelic acid (MA), global thioethers and styrene-specific mercapturic acids was measured in urine samples from 64 workers employed in three companies fabricating glass fiber-reinforced polyester products. Global thioethers were measured by a spectrophotometric method while MA and specific mercapturic acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine (M1) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine (M2), were measured by high pressure liquid chromatography with UV detection. Excretion of M1 and M2 was qualitatively verified by gas chromatography-mass spectrometry. The environmental measurements were carried out with passive dosimeters. Workers had 8-h TWA exposure levels ranging from 0 to 667 mg/m(3). End-of-shift MA excretion ranged from 0 to 2.08 mmol/mmol creatinine and was well correlated with environmental styrene exposure (r=0.91, p<0.001). M1 and M2 were detected (i.e. above ca. 1 mu mol/mmol creatinine) in urine samples of only three workers who were exposed to various concentrations of styrene. End-of-shift excretion of global thioethers was found to be significantly correlated to cigarette consumption as well as to styrene exposure, as measured by end-of-shift MA excretion. In opposition to data from rats, our results indicate that humans exposed to styrene excrete little styrene-specific thioethers. The apparent inter-individual variability in excretion of M1 and M2 suggests that they may not constitute suitable indicators of occupational styrene exposure.