2019 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6343310/ Andualem, Zewudu Africa Observational Exposure Study Modeling Elementary (K-5) Temperature Humidity Carbon Dioxide (CO2) Particulate Matter (PM) Bacterial load Classrooms Correlation Indoor air Settle plate method The grand total mean bacterial load was 2826.35 CFU/m3 in the morning and 4514.63 CFU/m3 in the afternoon. The lowest and highest mean bacterial load was recorded at school 3 (450.67 CFU/m3) and school 5 (7740.57 CFU/m3) in the morning and afternoon, respectively. In the morning relative humidity (r = − 0.7034), PM2.5 (r = 0.5723) and PM10 (r = 0.6856); in the afternoon temperature (r = 0.3838), relative humidity (r = − 0.4014) were correlated with indoor bacterial load. Staphylococcus aureus, Coagulase-negative Staphylococcus species and Bacillus species were among isolated bacteria.