2024 Yes Polycyclic aromatic hydrocarbons in primary school environments: Levels and potential risks https://www.sciencedirect.com/science/article/abs/pii/S0048969716321258?via%3Dihub Oliveira, Marta Europe Exposure Students Elementary (K-5) Particulate Matter (PM) Air School Polycyclic aromatic hydrocarbons (PAHS) indoor/outdoor children Risk PM2.5-bound PAHs were measured indoors and outdoors at 10 urban Portuguese primary schools. Indoor sources contributed to lighter PAHs; traffic dominated overall. Cancer risk in students exceeded WHO and USEPA thresholds, driven by indoor exposure time. 2017