Personal exposure to PM2.5 in five commuting modes under hazy and non-hazy conditions.

Effective reducing exposure to fine particulate matter (PM2.5) during commuting can help lower the risk of adverse health effects therefrom; however, few studies have examined the influence of different background levels of air pollution-particularly in China where PM2.5 concentrations are high globally. In this study, personal sampling was conducted to measure individual exposure during five different modes of commuting (bus, metro, car, bicycle and walking) in Shanghai, China. A total of 125 measurements were conducted for five days under haze and non-haze conditions, following which the corresponding doses of PM2.5 inhaled were estimated. The mean concentrations (±standard deviation, SD, 1-min averaging) of background PM2.5 were 155.9 (±98.7) μg/m3 during haze and 36.3 (±17.6) μg/m3 under the non-haze conditions. Under both conditions, active commuters were exposed to higher PM2.5 concentrations than those using motorized commuting modes (Wilcoxon test, p < 0.01). Moreover, driving with closed windows and air conditioning effectively reduces the PM2.5 concentrations in cars by 35 %-57 %. Cyclists inhaled the highest doses (539.8 ± 313.2 and 134.8 ± 71.3 μg/h under haze and non-haze conditions, respectively), whereas car drivers inhaled the lowest doses (28.8 ± 21.2 and 3.7 ± 2.6 μg/h under haze and non-haze conditions, respectively). Individual exposure to PM2.5 during commuting varied with the modes; the discrepancy between the latter depended largely on the ambient concentration. Our findings provided evidence that traffic-related air pollution contributed to daily pollutant exposure and highlighted the importance of taking personal protective measures while commuting, particularly during haze.