2019 Yes https://doi.org/10.1186/s40248-018-0167-y Andualem, Zewudu Africa Observational Exposure Study Students Elementary (K-5) Temperature Humidity Particulate Matter (PM) Bacteria Other Bacterial load Classrooms Correlation Indoor air Settle plate method Cross-sectional study in 51 classrooms at 8 Ethiopian primary schools used settle plate sampling to assess bacterial load and correlate it with PM2.5, PM10, temperature, and humidity. Findings call for better IAQ control to protect student health.