Associations of indoor airborne microbiome with lung function: evidence from a randomized, double-blind, crossover study of microbial intervention†

Microorganisms constitute an essential component of the indoor ecosystem and may pose potential health risks after inhalation. However, evidence regarding the impact of indoor airborne microbiome on general respiratory health is scarce. Additionally, while air purification has been shown to be an effective strategy for controlling culturable bioaerosols, its impact on indoor airborne microbiome remains unclear. To determine the impact of indoor airborne microbial exposure on lung function, and whether and how air purification can modify indoor airborne microbiome, we conducted a randomized, double-blind, crossover study employing air purification intervention among 68 healthy young adults in Beijing, China. Indoor airborne bacteria and fungi were characterized using amplicon sequencing technology and quantified by qPCR. Our results indicated positive associations between indoor airborne microbial α-diversity and lung function indices; however, adverse effects from total microbial load were observed. Males were more susceptible to microbial exposure than females. Beneficial effects from richness in Actinobacteria, Bacteroidia, Oxyphotobacteria, Bacilli, Clostridia, Alphaproteobacteria, Gammaproteobacteria, Dothideomycetes, and Sordariomycetes, and detrimental effects from five Proteobacteria genera, including Dechloromonas, Hydrogenophaga, Klebsiella, Pseudomonas, and Tolumonas, were also identified. Air purification contributed to decreased fungal diversity and total fungal load, but not the overall microbial community structure. Our study demonstrates the significant role of indoor airborne microbiome in regulating human respiratory health and provides inspiration for improving health through manipulation of indoor microbiome. Meanwhile, our study also underscores the importance of balancing the potential benefits from decreased microbial load and the underlying risks from reduced microbial diversity while applying environmental microbial interventions.