Characterization, pro-inflammatory response and cytotoxic profile of bioaerosols from urban and rural residential settings in Pune, India

Microbiota associated with airborne particulate matter (PM) is an important indicator of indoor pollution as they can be pathogenic and cause serious health threats to the exposed occupants. Present study aimed to investigate the level of culturable microbes associated with PM and their toxicological characterization in urban and rural houses of Pune city. Highest concentration of bacterial aerosols observed to be associated with PM10 size fraction in urban site (2136 ± 285 CFU/m3) whereas maximum fungal concentration has been measured in rural houses (1521 ± 302 CFU/m3). Predominantly found bacterial species were Bacillus sp., S. aureus, and Pseudomonas aeruginosa and fungal species were Aspergillus sp., Cladosporium sp., and Penicillium sp. in both urban and rural residential premises. Concentration of endotoxin measured using the kinetic Limulus Amebocyte Lysate assay exhibited that the level of endotoxin in both urban and rural sites are associated with household characteristics and the activities performed in indoor as well as outdoor. Cell free DTT assay confirmed the ability of these airborne microbes to induce the production of reactive oxygen species (ROS) varying along with the types of microorganisms. On exposure of A549 cells to airborne microbes, a significant decrease in cell viability was observed in terms of both necrosis and apoptosis pathway. Elevated production of nitric oxide (NO) and proinflammatory cytokines in epithelial cells and macrophages clearly suggest the inflammatory nature of these airborne microbes. Results derived from the present study demonstrated that the indoor air of urban and rural houses of Pune is contaminated in terms of microbial load. Therefore, attention should be paid to control the factors favoring the microbial growth in order to safeguard the health of exposed inhabitants. [Display omitted] •Total culturable microbes associated with PM were detected in indoor environments.•Predominantly found microbial isolates are S. aureus, P. aeruginosa and Aspergillus sp.•LAL assay exhibited eminent level of endotoxin in urban and rural houses.•Annexin study confirmed cell death pathway induced by prevalent airborne microbes.•Dominantly found microbes exhibited elevated production of proinflammatory mediators. Present study screened the dynamic behavior of airborne microbes associated with PM collected from rural and urban indoor environments of Pune, India in terms of their measurement, characterization and evaluation