Quantitative assessment of cyclists’ exposure to PM and BC on different bike lanes

Abstract

To assess the exposure of cyclists to particulate matter (PM) and black carbon (BC), real-time mobile monitoring with portable instruments was carried out on typical bike lanes in Xi'an, China. The inhalation dose as well as the deposition and distribution of different sizes of PM and BC in cyclists' respiratory systems, were quantified using a multiple-path particle dosimetry model (MPPD). A generalized linear regression model was fitted to explore the impact of different potentially influencing factors. The results of this case study in Xi'an showed that cyclists' exposure to PM2.5 (70.9 ± 30.0 μg m−3) and BC (7.5 ± 5.1 μg m−3) was marked by great temporal and spatial variability along the sampled urban routes, and their exposure hotspots generally consisted of intersections, temporary parking sites for vehicles, and diesel vehicles. Among the three types of bike lanes, cyclists were exposed to the lowest PM2.5 (62.9 ± 29.1 μg m−3) and BC (6.86 ± 4.0 μg m−3) concentrations on bike boulevards. The regression results revealed that certain factors, namely bike lanes, vegetation, and meteorological conditions, are correlated with cyclists' exposure to PM2.5. For their BC exposure, traffic volume was the predominant predictor. Concerning their regional deposition in the cyclists' respiratory system, PM2.5 was deposited to a greater extent in the head region (90%) than BC, the latter being deposited primarily in the pulmonary region (43%). This finding of greater BC deposition in the pulmonary region bolsters the need to incorporate BC into the current air-quality index of urban areas.