Air Pollution Exposure during School Commutes

Abstract

Background Understanding of how school location impacts children’s air pollution exposure and the ability of children to walk and bike to school has been a policy issue of interest in recent years. Smart growth advocates encourage districts to locate schools in “walkable” locations, often near high-volume roadways while health professionals emphasize the importance of minimizing near-roadway exposure and support decisions to distance school locations from major roadways. As states implement laws to site schools away from high-volume roadways, such policies often lead to school locations that are disconnected from neighborhoods and accessible only by motorized transport modes. This study analyzes children’s air pollution exposure during school travel and during the school day and assesses exposure for children walking to a nearby school in a heavy diesel/heavy traffic area compared to their exposure if they were required to be bussed or driven to a remote school located in a low diesel/low traffic environment. Methods Researchers selected two neighborhoods with different air quality environments – heavy-diesel/heavy-traffic and low-diesel/low-traffic – with a synthetic sample of students. Home-to-school commuting routes were created for three modes: walk, automobile, and school bus. Air pollution exposure along each route was estimated using models developed from the Near-Road Exposures and Effects of Urban Air Pollutants (NEXUS) study, which are calibrated to capture conditions in 2010 during typical school travel periods for the Detroit metropolitan area. Daily average exposures for pollutant NOx were estimated by breaking the average school day into 5 phases (AM Commute, Unload, School Day, Load, PM Commute). Results Commuting exposure to NOx for all modes was lower for children at the low-diesel/low-traffic school than those at the high-diesel school. When children were driven or bussed outside of their neighborhood to the more distant, low-diesel school, time-weighted daily average cumulative NOx exposure was the greatest at ~340 μg/m3 if bussed and ~175 μg/m3 if driven (compared to 190 and 152 respectively if they had taken these modes to their local high-diesel neighborhood school). Conclusions Local school environments still largely drive the daily cumulative exposures to air pollutants among children; however, the exposures during school commutes are not negligible. In particular, our simulated implementation of policies that use buses to transport children to better air quality environments found no association with net reductions in daily exposure.