Influence of climate on microbiological air quality in school classrooms

Abstract

The aim of the study was to assess the microbiological quality of air in a naturally ventilated classroom used by students. The research was conducted over a nine-week cycle during the winter-spring-summer period of 2024. Bacterial and fungal concentrations in the air were analyzed, and the results obtained were compared with indoor microclimate parameters and atmospheric conditions. It was found that after classroom airing, bacterial counts decreased significantly, while mold spore counts increased, indicating a significant influence of outdoor air on the composition of indoor bioaerosols. During classes, there was a systematic increase in both bacterial abundance and diversity, with the primary source being the room occupants. The variability in microbial counts was also strongly correlated with weather conditions - dry, sunny days promoted reductions, while high humidity and limited exposure to sunlight increased their presence. The identified microorganisms belonged to general typical of indoor and outdoor environments, including Staphylococcus, Bacillus, Serratia, Aspergillus, and Penicillium, some of which are potentially pathogenic taxa. Regression modeling confirmed that key factors shaping microbial abundance were indoor and outdoor air temperatures. Despite the observed fluctuations, air quality remained within the typical range for public spaces and did not pose a significant health risk to users. The results emphasize the importance of appropriate ventilation and microclimate control in ensuring proper microbiological air quality in classrooms.