Assessment of health risk of occupationally low-level benzene exposure based on biological monitoring indicator

  Objective  The cancer risk of occupationally low-level benzene exposure was assessed based on epidemiological survey data and biological monitoring biomarkers of benzene exposure.

  Methods  Based on the epidemiological data of occupational benzene exposure, the cancer risk model of occupational exposure to low-level benzene was deduced with multistage method. The relationship between air benzene concentration and metabolite concentration and its uncertainty analysis were done based on Bayesian linear regression and Markov Chain Monte Carlo method using R language, JARG software package and Crystal Ball software. The urinary S-phenylmercapturic acid (S-PMA) and trans, trans-muconic acid (tt-MA) concentrations were used to assess the cancer risk of benzene exposure.

  Results  Considering the low-level benzene exposure, a binomial multi-stage model was established to characterize the carcinogenic risk. The benzene exposure at level with current values of occupational exposure limits in China, including permissible concentration-time weighted average of benzene in air (6 mg/m³), urinary S-PMA concentration (100 μg/g Cr) and tt-MA concentration (3.0 mg/g Cr) after shift could cause the cancer risk 5.64 × 10^-4, 2.31 × 10^-4 and 1.52 × 10^-4, respectively, which were higher than the acceptable level 10^-4 for occupational population proposed by US EPA and US CDC.

  Conclusions  The cancer risk of benzene exposure at level with value of the national exposure limit was still relatively high, if benzene metabolites were used as indicator of exposure. In order to control the risk, engineering control and personal protection measures should be taken to reduce the exposure level as much as possible. In view of the risk acceptability, it is necessary to reduce the occupational exposure limit of benzene in China.