Abstract
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 360μgm−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.
Highlights
Renewed interest in ‘traditional’ urban land use patterns and designs, such as moderate density mixed-use development, multimodal transit networks, and pedestrian friendly streetscapes with wide sidewalks and short, well-connected city blocks, has coincided with an expanding body of literature suggesting that pedestrian-oriented designs may offer numerous benefits, including the positive health outcomes associated with walking and cycling to work and other daily destinations (Frank, Engelke, & Schmid, 2003; Heath et al, 2006; Sallis et al, 2009)
The aim of the present study is to contribute to the on-going effort to understand the relationships between the built environment, site-specific activity patterns, and pedestrian exposure to air pollution by (1) identifying specific contributors to average and short-duration peak PM2.5 concentrations in mixed-use urban environments with varying typologies and design elements using a concomitant mobile air quality-video sampling system, and (2) determining the degree to which pedestrian activity along sidewalks within these environments align with PM2.5 concentrations at four separate times of day, and on weekdays versus Saturdays
The Environmental Protection Agency (EPA) requires that average ambient PM2.5 concentrations be no higher than 35 g m−3 over 24-h and no more than 12 g m−3 over one year to ensure public health and welfare (U.S EPA, 2012)
Summary
Renewed interest in ‘traditional’ urban land use patterns and designs, such as moderate density mixed-use development, multimodal transit networks, and pedestrian friendly streetscapes with wide sidewalks and short, well-connected city blocks, has coincided with an expanding body of literature suggesting that pedestrian-oriented designs may offer numerous benefits, including the positive health outcomes associated with walking and cycling to work and other daily destinations (Frank, Engelke, & Schmid, 2003; Heath et al, 2006; Sallis et al, 2009). Compact, mixed-use, pedestrian-oriented developments, have the potential to increase exposure to outdoor air pollution by focusing pedestrian activity within transport microenvironments that may trap and concentrate automotive emissions (de Nazelle, Rodriguez, & Crawford-Brown, 2009; Marshall, Brauer, & Frank, 2009). A clear distance decay effect was detected, with particulate concentrations significantly higher curbside than along the building facade
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