Characterization and risk assessment of particulate matter and volatile organic compounds in metro carriage in Shanghai, China

Abstract

Air quality in transportation microenvironment has received widespread attention. In this study, the exposure levels of volatile organic compounds (VOCs) and particulate matter that have a diameter of less than 2.5 micrometers (PM2.5) in Shanghai metro system were measured simultaneously, and their risks to human health under different driving conditions were then assessed. The results showed that VOCs, PM2.5 concentrations and life cancer risk (LCR) of four VOCs (benzene, formaldehyde, ethylbenzene, and acetaldehyde) in the old metro carriages were about 3 times, 3 times and 2 times higher than those in the new metro carriages, respectively. This difference can be ascribed to the fact that air filtration system in the new metro trains is significantly improved. The VOC levels, PM2.5 concentrations and LCR of VOCs on the above-ground track were slightly higher than those on the underground track. This is due to less outdoor polluted air entering into the carriage on the underground track. Number of passengers also had an effect on VOCs and PM2.5 concentrations in metro carriages. Additionally, the LCR of VOCs inside metro trains should not be ignored (7.69 × 10-6~1.47 × 10-5), especially inside old metro trains with the old ventilation system.