Environmental and biological monitoring of styrene exposure: urinary excretion of D-glucaric acid compared with exposure indices.

Abstract Styrene, oxidized by liver microsomal enzymes, can determine a liver enzyme induction. Urinary excretion of D-glucaric acid (DGA), which is believed to estimate this effect, was measured in 27 workers exposed to styrene in a fiberglass plant and in 27 control subjects in order to make a comparison with environmental and biological exposure indices. In exposed workers, airborne concentrations (8-h TWA) of styrene varied between 9 and 415 mg/m3, with styrene metabolites [sum of mandelic acid (MA) + phenylglyoxylic acid (PGA)] ranging from 93 to 2130 mg/g Cr in endshift urine samples collected on a Thursday, and from 45 to 792 mg/g Cr in samples taken before work the following morning. The correlation coefficient (r) between 8- h TWAs and sum of urinary metabolites MA + PGA was 0.92 (y=4.06x - 36.05; p<0.001) for Thursday endshift (ES) samples, and 0.84 (y=1.46x + 46.82; p<0.001) for Friday morning samples (beginning of shift: BS). Urinary excretion of MA correlated better with exposure than that of PGA (MA: ES r=0.91; BS r=0.86. PGA: ES r=0.80; BS r=0.76). ES and BS levels of DGA in exposed subjects (equal to 4.41 ± 1.57 and 4.01 ± 1.18 mmol/mol Cr respectively) were both significantly higher than the 2.93 ± 0.88 observed in 27 control subjects (Mann-Whitney test; p<0.001). No significant correlation was found between individual exposure to styrene evaluated by the environmental concentration or by urinary metabolites and urinary excretion of DGA. Furthermore, both ES and BS urinary DGA levels increased across three classes of styrene exposure (<100, 101-200, and >200 mg/m3, respectively, including 10, 7 and 10 workers). The DGA difference between the most exposed and the not exposed subjects was significant (ES-DGA: z=4.03 and p<0.05; BS- DGA: z=3.16 and p<0.05; Kruskall-Wallis test), but individual pairwise comparisons among all other groups were not. In spite of the above results, no significant correlation was found between individual exposure to styrene and urinary excretion of DGA, so that this biomarker cannot be used to monitor the exposure effects on an individual basis.