Objective To assess the health risk of exposure to benzene in a petrochemical plant using probabilistic risk assessment (PRA), and compare with point estimate risk assessment (point assessment).
Methods Two types of workers, outside operators of chemical department and analysts of quality control department in a petrochemical plant, were selected to assess for the health risk of occupational benzene exposure using@risk software with references to the PRA and inhalation risk assessment models of Environmental Protection Agency (EPA). According to the recommendation values by EPA, the cancer risk value >1×10-4 was high cancer risk level, 1×10-6-1×10-4 was low cancer risk level, < 1×10-6 was no risk level; hazard quotient ≥ 1 was defined as non-cancer hazard level, and < 1 as no non-cancer hazard level. Conventional point assessment was also used. The advantages and disadvantages of the two methods were compared.
Results The results of point assessment showed that the cancer risks of outside operators and analysts were 0.43×10-4 and 0.37×10-4, respectively, both indicating a low cancer risk level, while the hazard quotients were 3.24 and 3.76, respectively, indicating non-cancer hazards. The PRA results showed that the probabilities of the operators at high, low, and no cancer risk levels were 10.6%, 88.9%, and 0.5%, respectively, and the corresponding probabilities of the analysts were 2.1%, 97.9%, and 0%, respectively. The probabilities of the operators with and without non-cancer hazards were 72.3% and 27.7%, respectively, and the corresponding probabilities of the analysts were 100% and 0%, respectively.
Conclusion Point assessment cannot show the distribution of a specific health risk in a population and are possibly to ignore or overestimate the risk. PRA show a full distribution of risk probability with reduced uncertainty and relatively accurate information, thus providing a scientific basis for health risk management and control.
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