Airborne fungal microbiota in indoor and outdoor classrooms of schools in Ho Chi Minh City: concentration and composition

Airborne microbial contamination is vital for evaluating air quality and its impact on human health. This study investigated airborne fungal concentrations and compositions in indoor and outdoor classrooms at a university and two secondary schools in Ho Chi Minh City, Vietnam, aiming to understand the factors influencing fungal presence and propose preventative measures for potential health risks. 120 air samples were collected over a semester using an active sampling method with a SKC Biostage (single stage bioaerosol impaction) and cultivated on Sabouraud Dextrose Agar (SDA). Fungal concentration was measured in air - conditioned (AC) and non - air - conditioned (non - AC) classrooms, both with and without students present, and compared to outdoor levels in schoolyards. Results revealed lower average fungal concentration in AC classrooms (178.31 ± 47.32 CFU/m³) compared to non - AC classrooms (236.11 ± 57.24 CFU/m³), while outdoor areas exhibited an average density of 223.57 ± 41.42 CFU/m³. Correlation analysis indicated a positive relationship between fungal density and both temperature and humidity. Air conditioning was found to significantly reduce fungal density by regulating these factors and filtering fungal spores. Most indoor samples exhibited fungal concentrations below the World Health Organization (WHO) recommended limit of 500 CFU/m³. Identified fungal genera included Aspergillus (specifically A. niger, A. terreus, A. fumigatus, A. oryzae, A. flavus ) and Trichoderma spp . This study provides insights into the airborne fungal microbiome within educational settings in Ho Chi Minh City, emphasizing the influence of environmental factors and human activity. The findings contribute to a better understanding of potential health risks associated with airborne fungi and inform strategies for improving indoor air quality in schools.