The Impact of an Anti-Idling Campaign on Ambient Air Quality Near Schools

Abstract

Background: Exposure to air pollution and diesel exhaust may be elevated at schools due to nearby traffic and buses. School bus idling, in particular, has been associated with an increase of fine particulate matter (PM2.5) and elemental carbon (EC) concentrations near schools. Aims: To determine the impact of an anti-idling campaign on outdoor air quality at four schools with varying exposure to school buses. Methods: Outdoor air sampling for PM2.5 and EC was conducted at four schools for five days before and after an anti-idling campaign. Sampling began each day 30 minutes before the morning arrival of buses and concluded 30 minutes after their departure in the afternoon. Sampling was conducted simultaneously at four corresponding community sites to represent ambient background concentrations. Differences in PM2.5 and EC levels at school and community sites for each sampling day were calculated before and after the campaign. Results: Prior to the anti-idling campaign, the average concentration of PM2.5 at 3 of the 4 schools exceeded the community background levels and the difference was greatest (4.1 µg/m3, p < 0.01) at the school with the most buses (n = 39). The largest difference in EC between school and community site was also observed at the school with the greatest number of buses (0.40 µg/m3, p < 0.01). Following the anti-idling campaign, the average difference in PM2.5 at the school with the most buses decreased from 4.1 µg/m3 to 1.0 µg/m3 (p < 0.05). Similarly, at this school the difference in EC level decreased from 0.4 µg/m3 to 0.1 µg/m3 (p < 0.05). Concentrations of PM2.5 and EC at schools with fewer buses (n = 5–12) were not significantly reduced. Conclusions: The concentration of PM2.5 and EC at schools may exceed community background levels, particularly in the presence of idling school buses. An anti-idling campaign was effective at reducing the concentrations of PM2.5 and EC at the school with the greatest number of buses.