Particulate matter intake fractions for vehicular emissions at elementary schools in Hamilton, Canada: an assessment of outdoor and indoor exposure

Air pollution around schools has been considered a crucial concern worldwide, as children are at school for a large part of the day. A growing body of evidence finds that schools are located in areas with high levels of air pollutants with significant contributions from motor vehicles. Determining children exposure to air pollutants at schools is crucial for disease prevention and control. In this paper, we evaluated PM2.5 intake fractions for vehicular emissions at elementary schools in Hamilton, Canada. Specifically, we estimated the mass inhalation of PM2.5 (that comes from traffic) by children considering two environments: outdoor (during drop-off period) and indoor (during class period). We evaluated PM2.5 intake fractions (iF) for vehicular emissions in 32,298 students from 86 elementary schools in Hamilton. Indoor exposure presented the highest iF. On average, each student inhales 0.53 × 10−6 ppm daily during the drop-off time (outdoor exposure) and 13.06 ppm daily during class hours (indoor exposure). Considering time spent in classes, this estimate indicates that approximately 13 g of PM2.5 emitted from motor vehicles is inhaled for every million grams of PM2.5 emitted. Our sensitivity analysis showed that traffic emissions were the variable that affects the iF most during outdoor and indoor exposure. Our findings can help in future investigations to advance environmental health effects research, especially on children’s health and human health risk assessment. Our results are important for future public policies related to transportation, environmental health, and urban planning, including air pollution and location of schools.