2022 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9022782/ Mathaios, Vasileios N. North America Observational Epidemiology Study Elementary (K-5) Nitrogen Dioxide (NO2) Fungi LASSO identified 10, 10, and 11 significant factors (lowercase italic p less than 0.05p<0.05) that were associated with indoor fine particulate matterPM2.5, BC, and nitrogen dioxideNO2 exposures, respectively. The overall variability explained by these models was uppercase r squared equals 0.679R2=0.679, 0.687, and 0.621 for fine particulate matterPM2.5, BC, and nitrogen dioxide, NO2, respectively. Of the model’s explained variability, outdoor air pollution was the most important predictor, accounting for 53.9%, 63.4%, and 34.1% of the indoor fine particulate matter PM2.5 , BC, and nitrogen dioxide, NO2 concentrations. School-based predictors included furnace servicing, presence of a basement, annual income, building type, building year of construction, number of classrooms, number of students, and type of ventilation that, in combination, explained 18.6%, 26.1%, and 34.2% of fine particulate matterPM2.5, BC, and nitrogen dioxide NO2 levels, whereas classroom-based predictors included classroom floor level, classroom proximity to cafeteria, number of windows, frequency of cleaning, and windows facing the bus area and jointly explained 24.0%, 4.2%, and 29.3% of fine particulate matterPM2.5, BC, and nitrogen dioxideNO2, concentrations, respectively.