High-resolution distributions of traffic particles and personal inhalation dose estimation at different pedestrian overpasses

While overpasses are conducive to pedestrians’ safe passage across roads, heavy road traffic can also lead to high exhaust emissions and introduce remarkable but uncertain air pollution to overpasses due to complex street environments. To clarify the pollution distribution and personal exposure dose, we collected fine-scale samples of submicron particle (PM_1.0) and black carbon (BC) concentrations synchronously at two “I-shaped” overpasses with different street environments. Then, we statistically analysed the spatiotemporal particle patterns at the two overpasses and finally evaluated the pollutant inhalation doses of different pedestrians passing through the overpasses. The measurements indicated that the average particle level was higher in the open overpass crossing heavy ground traffic, and particle hotspots were distributed mostly in the upper sections of the two overpasses, while BC hotspots sometimes occurred at the entrances of the overpass stairways. Contrary to BC, PM_1.0 was always high in the morning, and its fluctuations were more affected by suddenly intensified background pollution. Under a low background pollution scenario, the traffic volume and wind speed were the largest factors affecting both pollutants at the two overpasses. The inhalation exposure estimation showed that the inhaled pollutant doses of pedestrians climbing stairs were greater than those of pedestrians walking on the upper sections of the overpasses, and the maximum increment can reach 22%. Among the different groups, the inhalation dose was highest for mid-aged men but lowest for elderly women. These results highlight the importance of optimizing overpasses based on location environments and pedestrian activity levels to maximize the reduction in personal inhaled pollutant dose.