Biological monitoring occupational exposures to styrene and styrene-(7,8)-oxide

This study investigated the capability of some urinary and haematic biomarkers to discriminate among different levels of occupational exposure to styrene (Sty) and styrene-(7,8)-oxide (StyOX) and evaluated the influence of smoking habit and genetic polymorphism of metabolic enzymes GSTM1 and GSTT1 on these biomarkers. With this aim, we recruited workers of the reinforced plastic industry (n=8), of the paint and dye industry (n=13), and a group of controls (n=22). Median personal exposure to airborne Sty and StyOX in the different working activities was 14.8, 3.1 and 0.3 mg/m3, and 126, 13 and <5 µg/m3, respectively, as evaluated by repeated measurements. These chemicals were strictly correlated with each other (Pearson r = 0.826), the ratio between Sty and StyOX being about 1000:5. Personal exposure was significantly higher in exposed workers than in controls and, among workers, in subjects of the reinforced plastic industry. Urinary biomarkers, namely unchanged styrene (StyU), mandelic acid (MA), phenylglyoxylic acid (PGA), phenylglycine (PHG), 4-vinylphenol (4-VP), and mercapturic acids (M1 and M2) were higher in end- than in pre-shift samples and significantly correlated with both airborne Sty and StyOX. The best correlations were observed between end-shift MA or MA + PGA and airborne Sty (r = 0.890 or 0.886, respectively). The excretion of mercapturic acids was 6-fold higher in subjects with GSTM1 active genotype in comparison with those with null genotype. Cysteinyl albumin and hemglobin adducts of StyOX could not distinguish the different exposure categories investigated. In conclusion, in both reinforced plastic and paint and dye industry there was co-exposure to airborne Sty and StyOX. Among the different biomarkers urinary MA and PGA and their sum showed the best capability to discriminate different exposures and are recommended for Sty exposure assessment starting from a level of 1 mg/m3.