An investigation of the PM 2.5 concentrations and cumulative inhaled dose during subway commutes in Changchun, China.

Air quality in subway systems is crucial as it affects the health of passengers and staff. Although most tests of PM 2.5 concentrations in subway stations have taken place in public areas, PM 2.5 is less understood in workplaces. Few studies have estimated the cumulative inhaled dose of passengers based on real-time changes in PM 2.5 concentrations as they commute. To clarify the above issues, this study first measured PM 2.5 concentrations in four subway stations in Changchun, China, where measuring points included five workrooms. Then, passengers' exposure to PM 2.5 during the whole subway commute (20-30 min) was measured and segmented inhalation was calculated. The results showed that PM 2.5 concentration in public places ranged from 50 to 180 μg/m 3 , and was strongly correlated with outdoors. While the PM 2.5 average concentration in workplaces was 60 µg/m 3 , and it was less affected by outdoor PM 2.5 concentration. Passenger's cumulative inhalations in single commuting were about 42 μg and 100 μg when the outdoor PM 2.5 concentrations were 20-30 μg/m 3 and 120-180 μg/m 3 , respectively. The PM 2.5 inhalation in carriages accounted for the largest proportion of the entire commuting, about 25-40%, because of the longer exposure time and higher PM 2.5 concentrations. It is recommended to improve the tightness of the carriage and filter the fresh air to improve the air quality inside. The average daily PM 2.5 inhaled by staff was 513.53 μg, which was 5-12 times higher than that of passengers. Installing air purification devices in workplaces and reminding staff to take personal protection can positively protect their health.