Concentration, pathogenic composition, and exposure risks of bioaerosol in large indoor public environments: A comparative study of urban and suburban areas.

Biological contamination in larger indoor environments can lead to the outbreak of various infectious diseases. This study aimed to compare the pollution profiles and associated health risks of airborne microorganisms in different indoor settings between urban and suburban areas by culturing, sequencing, and toxicological evaluation. The results indicated that the average level of culturable bacteria was higher in urban areas (955 ± 259 CFU/m) compared to suburban areas (850 ± 85 CFU/m), with the highest concentrations found in the market (2170 ± 798 CFU/m) and gymnasium (2010 ± 300 CFU/m). Conversely, the total number of airborne bacteria was higher in classroom (2.09 × 10) and laboratory (1.95 × 10 copies/m), likely due to the presence of viable but non-culturable cells. Additionally, the concentrations of 0.5-2.0 μm total particles were higher in the market and cafeteria. Dominant airborne genera included Acinetobacter and Pseudomonas for bacteria, Cladosporium and Aspergillus for fungi, as well as Geneviridae and Herpesviridae for viruses. Bacterial and viral diversity and richness were significantly higher in suburban areas compared to urban areas, with distinct viral communities observed in hospital. Cytotoxicity assays revealed lower viability of cells in response to bioaerosols from the library (52.3 %) and laboratory (54.5 %); while lower proliferation rates were found for the cells exposed to bioaerosol from gymnasium (5.4 %) and market (6.0 %), suggesting higher toxicity of these environments. Additionally, bioaerosol exposure may impair cellular innate immunity by increasing the expression of IL-6, IL-8, TNF-α, IFN-γ. Our findings provide valuable information for assessing and controlling bioaerosol-related health risks in indoor environments.