Determination of S-phenylmercapturic acid in the urine—an improvement in the biological monitoring of benzene exposure

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Abstract
In an inhalation study rats were exposed to different doses of benzene, ranging from 1 to 500 p.p.m. The urine was sampled during the inhalation period of 8 h and for 24 h after exposure. S-Phenylmercapturic acid (S-PMA) in the urine was determined by amino acid analysis. Phenol was measured by gas chromatography/mass spectrometry. In both cases the correlation between benzene uptake and the excretion of the urinary metabolites was significant at the level of P = 0.01. The same significant correlation (P = 0.01) was demonstrable after i.p. administration of benzene at doses between 0.7 and 140.0 μI/kg body weight. In the case of two collectives of workers who were exposed to air concentrations of up to 0.15 p.p.m. for 8 h and of up to 1.13 p.p.m. for 12 h respectively, the amount of S-PMA in the first urine samples after the shift was significantly higher than in samples collected at the beginning of the shift (P = 0.01). In the first collective the mean values and the standard deviations of the S-PMA concentrations in the samples at the beginning of the shift were 12.0 ± 16.7 compared with 48.5 ± 64.5 μg/g creatinine at shift end. In the second collective they were 25.1 ± 25.1 compared with 70.9 ± 109.2 μg/g creatinine. The level of significance of the difference between the concentration values of S-PMA at the beginning and end of the shift was P = 0.01. The phenol concentration did not differ significantly. These results suggest that S-PMA can be regarded as a useful indicator for monitoring individuals and collectives exposed to benzene at levels even <1 p.p.m.