Effects of smoking and drinking habits on urinary o-cresol excretion after occupational exposure to toluene vapor among Chinese workers.

The relationship between the time-weighted average intensity of exposure to toluene and o-cresol concentration in shift-end urine was investigated in nearly 500 factory workers of both sexes in China, together with a similar number of nonexposed control subjects. Toluene concentration (25 ppm as geometric mean and 550 ppm as the maximum) was monitored by diffusive sampling using carbon cloth as adsorbent followed by gas chromatographic (GC) analysis. o-Cresol (up to 7 mg/l) was measured by GC after acid hydrolysis of samples. Urinary o-cresol levels correlated significantly (r = 0.69-0.77; p < 0.01) with toluene exposure in men, women and the two sexes in combination, regardless of correction for urine density. When compared with hippuric acid, however, o-cresol was less sensitive as an indicator of exposure to toluene and is not a suitable biological marker for detecting low level toluene exposure. Since urinary o-cresol level was significantly reduced by smoking, drinking, and the two habits combined, it cannot be considered reliable as an indicator of exposure to toluene.