Pedestrian exposure to near-roadway PM2.5 in mixed-use urban corridors: A case study of Omaha, Nebraska

Compact, mixed-use, and pedestrian-oriented urban developments may offer numerous environmental and health benefits, yet they may also facilitate pedestrian exposure to air pollution within the near-roadway environment. This research examines ambient concentrations of fine particulate matter (PM2.5) across six sites situated within central Omaha, Nebraska, a mid-sized metropolitan area located in the Midwest US. The sites ranged from a low-density, strip-mall development to moderate-density entertainment, commercial, and retail districts with varying degrees of horizontal and vertical mixed-use. Tracing approximately two kilometer routes along the sidewalk, factors affecting average and peak PM2.5 concentrations at each site were identified using a mobile data cart capable of simultaneously recording video and sampling PM2.5. In general, sidewalk PM2.5 concentrations, averaged for each outing, were similar to “background” values obtained at a nearby fixed monitoring station (FMS). The results of a linear regression analysis suggest that 56% of the variability in sidewalk PM2.5 were attributable to background concentrations. Short-duration peak concentrations of up to 360 μg m−3 were associated primarily with vehicle tailpipe emissions and tobacco smoke. At four of the six study sites, pedestrian volume was higher on days and times when PM2.5 concentrations were comparatively low. Implications for policy and planning are discussed.