2021 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7386335/ Prokopciuk, Nina Europe Exposure Study Elementary (K-5) Children Indoor aerosols Pollution levels Primary schools Systematic and occasional sources Ventilation During all seasons, local cafeterias in the absence of ventilation were the main sources of the elevated levels of indoor PMC and PNC (up to 97,500 particles/cm3). The other sources of airborne particulates were the children’s activity during the lesson breaks with PMC up to 586 μg/m3. Soft furniture, carpets in the classrooms and corridors were responsible for PMC up to 200 μg/m3. Outdoor aerosol pollution (up to 18,170 particles/cm3) was higher for schools in city center. Elevated air pollution in classrooms also resulted from intermittent sources, such as construction work during classes (200-1000 μg/m3) and petrol-powered lawn trimmers (up to 66,400 particles/cm3).