Application of China's occupational disease hazard classification and EPA inhalation risk model in health risk assessment of work exposed to benzene

Background Benzene is a group Ⅰ carcinogen. With the wide use of benzene as an important production material in various industries, the number of workers exposed to benzene remains high. There is an urgent need to evaluate workers' health damage caused by occupational benzene exposure in the workplace, and propose preventive and control measures to reduce the occupational health risk of benzene.

Objective This study evaluates the occupational health risks of workers exposed to benzene in a paint factory in Jiangsu Province by China's occupational hazard classification and US Environmental Protection Agency (EPA) inhalation risk assessment model, and discusses their applicability and advantages.

Methods Questionnaires about chemical raw materials, worker distribution, and personal protective equipment usage were distributed among the workers exposed to benzene at various workstations in a paint factory in Jiangsu Province and the workplace monitoring data of benzene concentrations were collected in March 2018. China's occupational hazard classification and US EPA inhalation risk assessment model were used to evaluate the occupational health risks of workers exposed to benzene.

Results The occupational benzene-exposed workers were mainly distributed in packing, paint mixing, and color palette workstations. The concentration of 8 h time weighted average (C_TWA) of each workstation was less than the permissible concentration-time weighted average (PC-TWA, 6 mg·m^-3), the concentration of short-term exposure limit (C_STEL) was less than the permissible concentration-short-term exposure limit (PC-STEL, 10mg·m^-3), and result graded by China's occupational hazard classification was G ≤ 1 (Grade 0), indicating relative harmless work. However, due to the large difference in benzene exposure concentrations in different workstations, the results graded by EPA inhalation risk assessment model showed varied carcinogenic and non-carcinogenic risks with the extension of exposure years. The highest C_TWA of benzene exposure was 4100μg·m^-3 in the color palette workstation. The carcinogenic risks (Risk) of workers in the selected workstations all exceeded 1×10^-6 after they were exposed to benzene for 1 year, indicating medium carcinogenic risks; among them, the highest carcinogenic risk (Risk) was (32.22-114.23)×10^-6 in the color palette workstation. When they were exposed to benzene for 5 years, high carcinogenic risks occurred in the color palette, paint mixing, and packaging workstations, and the Risk values were (102.16-571.16)×10^-6. When they were exposed to benzene for 20 years, all workstations except the testing workstation had high carcinogenic risks. The hazard quotients (HQ) of the selected workstations were much higher than 1; among them, the non-carcinogenic risks were higher in the packing and color palette workstations, and their HQ values were 25.39-37.44.

Conclusion According to China's occupational hazard classification standards, the benzene-related factory's occupational hazard risk at reported exposure concentration is grade 0 (relatively harmless). According to the US EPA model, all workstations show medium to high health risks. Therefore, even the result generated by China's occupational hazard classification is grade 0, we should consider the carcinogenic and non-carcinogenic health effects of benzene exposure in real workplace settings, and pay attention to the health protection of occupational benzene-exposed population.