Objectives: Recently, S-phenylmercapturic acid (S-PMA) and trans,trans-muconic acid (t,t-MA) in urine have been proposed as reliable biomarkers for monitoring occupational exposure to benzene. The aim of this study was to test the applicability of S-PMA and t,t-MA as exposure biomarkers and to monitor the occupational exposure level and the extent of environmental contamination from benzene in Korea.
Methods: The urinary excretion of S-PMA and t,t-MA in rats after the intraperitoneal administration of benzene (0.88-800 mg/kg body weight, 7 days) was examined. These biomarkers were also validated in human urine samples collected from elementary schoolchildren in several industrial areas including chemical manufacturing plants, oil refineries, and natural gas-producing installations in Korea. Urine was collected from elementary schoolchildren in a mountain village with no known occupational exposure to benzene and air pollution as the reference group.
Results: In rats, there was a significant relationship between the benzene concentration and the excretion of the urinary S-PMA and t,t-MA as a function of concentration, and the excretion of benzene metabolites peaked on the first day after intraperitoneal administration. In human urine, higher levels of S-PMA and t,t-MA were detected more frequently in petrochemical industrial areas than in areas with no known occupational exposure to benzene.
Conclusions: These results show that the quantitative determination of S-PMA and t,t-MA in urine can be used as a reliable exposure biomarker for benzene, and they also suggest that extensive attention to benzene exposure is needed for maintaining the health of the population in Korea.