2025 Yes https://doi.org/10.1016/j.scitotenv.2025.179113 Bloom, Erica Europe Experimental Observational Exposure Study Students Elementary (K-5) Temperature Humidity Carbon Dioxide (CO2) Particulate Matter (PM) Bacteria Respiratory symptoms Respiratory symptoms Allergy School environment Endotoxins Respirable particulate matter (PM 10) FeNO was measured in 415 Swedish schoolchildren and linked to asthma, allergy, and environmental factors. FeNO rose with asthma, allergy, PM10, and Gram-negative bacteria, with effects modified by sex, parental allergy, home dampness, and housing type.