2024 Yes Distribution Levels of Particulate Matter Fractions (<2.5 µm, 2.5-10 µm and >10 µm) at Seven Primary Schools in a European Ceramic Cluster https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8124735/ Pallarés, Susana Europe Observational Elementary (K-5) Particulate Matter (PM) Indoor airborne particles Primary schools Statistical analysis Ceramic hub Mediterranean basin Particulate matter was measured in seven schools in northeast Spain. Rural schools had lower PM2.5 and large particle levels, while industrial sites showed highest coarse particles. Indoor and outdoor sources both influenced classroom air quality. 2021