2016 No https://doi.org/10.1111/ina.12237 Madureira, J. Europe Exposure Study Students Elementary (K-5) Carbon Dioxide (CO2) Particulate Matter (PM) Volatile Organic Compounds (VOCs) Bacteria Fungi Other Indoor air quality Bioaerosol Particulate matter (PM) Indoor sources Measured PM, CO₂, VOCs, fungi, and bacteria in 73 classrooms from 20 Portuguese public primary schools. CO₂ and PM often exceeded limits. Fungal and bacterial levels were high even in ventilated rooms. Findings call for improved IAQ controls in early education settings.