Concentration, composition and exposure risk assessment of particulate matter with different particle sizes in subway stations

Abstract

Particle composition and risk assessment of their exposure in a subway station are very important for a station's environment and the health of people. However, only a handful of papers have compared and analyzed the composition of particulate matter and the risk of their exposure to people. To address these issues, environmental parameters and particulate matter were measured for one month at six different locations in twelve subway stations in a capital city located on the central coast of China. The particulate matter (PM), its composition and characteristics were analyzed and compared. The daily average exposure risk assessment model for the studied city was proposed to analyze the exposure risks associated with various particulate matters and metals for both commuters and workers. The results showed that, in all public areas (station hall, platform and carriage), the concentrations of PM were higher than those outside the subway station. The highest values of PM2.5, PM10, and TSP (total suspended particulates) were determined to be 158.3 μg/m3, 168.0 μg/m3, and 170.7 μg/m3, respectively. The physical characteristics showed that the surface of particles inside the station was rougher, larger and darker in color. Compared to outdoors, the particles within the subway stations contained much more metals, particularly Fe that had the mass fraction of 9.59 %. On the other hand, the outdoor environment did not contain any Fe. These findings indicated that there were original sources of contamination at subway stations, and the hazardous nature of the particles was particularly pronounced within subway stations. The exposure risk of TSP and metals for workers was nearly twice that of passengers. This study aims to provide data that could help in controlling the environment at subway stations.