Statistical correlation analysis on indoor air high-priority pollutants in spanish public primary schools

Resumen

Understanding indoor pollutant sources is crucial because of the prevalence of air pollution exceeding recommended levels. In addition, different research underscores the link between pollutant exposure and adverse health effects, particularly in children under 12 years-old, whose respiratory system is undeveloped. Under this consideration, schools become a focus of research where students spend considerable time indoors. This research addresses this issue by conducting a comprehensive evaluation of indoor air quality in public primary schools across Madrid (Spain). Classrooms have been monitored for a year, and a statistical analysis has been performed to explore correlations between indoor air pollutant concentrations during occupied and unoccupied periods, as well as the impact of student activities and classroom operation, among others. This study reports mean indoor values of several indoor air pollutants in the monitored schools, such as CO2 (1.640 ppm), PM2.5 (23.8 μg/m³), PM1 (7.5 μg/m³), Ultrafine (7132.8 part/cm3) or TVOC (160 ppb), among others. Findings reveal strong positive correlations between PM1 and PM2.5 (with correlation coefficients exceeding 0.93), alongside notable associations with CO2 levels, suggesting common pollution sources. Additionally, ultrafine particles directly correlate with PM0.3, exhibiting significant fluctuations across monitoring campaigns. Temperature and humidity emerge as influential factors, with varying effects on indoor air quality. Operational and activity-related factors, including door/window use and student activities, also influence pollutant levels, providing valuable insights into improving indoor air quality.