2021 No https://doi.org/10.1016/j.jhazmat.2021.125531 Heo, Sujeong Asia Observational Exposure Study Modeling Students Elementary (K-5) Particulate Matter (PM) Heavy metals Other School air quality Particulate matter (PM) PM 2.5 Emission source Chemical constituent Field study measured PM2.5 in Seoul elementary schools near traffic; indoor levels were below outdoor and guideline limits. Source analysis showed 58.5% of PM2.5 came from outdoors. Findings support urban planning and school design to reduce children’s exposure to harmful pollutants.