Walk the Less Trodden Path, or rather, the Less Driven: Mapping Pedestrian Paths and Local Air Pollution for Selective Walking in Cleaner Air

When we walk outdoors, we breathe ambient air. Walking in an urban environment exposes us to varying levels of air pollution. Yet, air quality is only emerging as a dimension of walkability. Disregarding air quality when assessing walkability is just the tip of the iceberg: we tend to be unaware of the variability of air pollution over space, even though we are aware of the meteorological variability within our city. Yet, variations in pollution levels within urban environments can be large. Just think about Calgary: a metropolitan area over 800 km2, with a 300 m elevation range, strong winds, and localized pollution sources. Truly, where we walk can make a difference in the quality of the air we breathe. Further, several traffic-related pollutants exhibit a spatial pattern with pollutant concentration declining rapidly as distance from roads increases; therefore, walking within a few hundred meters of a major road leads to higher pollution exposure than if we were to walk further away from the road. Indeed, air pollution is measured regularly and frequently over time, but irregularly and sparsely over space, failing to capture its spatial variation. Over the last several years, in collaboration with Health Canada, our group has conducted spatially detailed air monitoring campaigns, deploying up to 100 monitors within the urban area of Calgary. We subsequently developed land use regression models, which yield reliable spatially detailed estimates of air pollution, e.g., at the postal code level. We further integrated our spatial estimates with the temporal measurements of the regulatory network, which yielded air pollution estimates at the postal code level on a monthly base; therefore, we can provide integrated estimates of spatial and seasonal variation in air pollution levels. We are integrating our estimates with walkability assessments, using Calgary as a pilot study. We further analyzed pollution levels over the city’s existing extensive pathway network. The outcome of this study is a map reporting pedestrian (and bicycle) paths, with associated levels of pollution in each season. The map shall help guiding ‘where to walk’ choices, promoting walking (and cycling) on pathways where pollution levels are lower.