Bacteriome and mycobiome in ambient PMs during haze episodes and health hazard: A nationwide survey in China

Abstract

Airborne microorganisms transported by haze-associated particulate matter (PM) pollution pose significant respiratory health risks due to their ability to penetrate deep alveolar regions. While bacterial dynamics in coarse PM were well-characterized, the ecological behavior and health impacts of microbial communities in fine particles (PM 1 and PM 2.5 ) remain poorly understood. Here, we integrated field sampling (Ji'nan City) with a systematic literature analysis of 17 Chinese cities to investigate spatial heterogeneity and PM pollution-driven shifts in bacterial and fungal communities via bioinformatic pipelines. Our results demonstrate that haze-associated PM pollution differentially modulates microbial diversity: bacterial diversity decreased by 28.3 ​% in PM 1 (p < ​0.01) but increased by 12.4 ​% in PM 2.5 (p ​< ​0.01), whereas fungal diversity exhibited consistent decline across PM 2.5 and PM 1 (p ​< ​0.05). Three distinct microbial response patterns emerged: (i) progressive enrichment of pollution-adapted taxa with escalating PM pollution level, (ii) sustained diversity loss in sensitive taxa, and (iii) selective proliferation of taxa at specific PM pollution thresholds. Critically, PM 1 preferentially harbored a greater variety of pathogens and PM 2.5 exhibits higher microbial abundance. The abundance of Aspergillus subversicolor correlated strongly with air quality index (AQI) (R 2 ​= ​0.82, p ​< ​0.01), indicating escalating health risks during severe haze episodes. This study identifies fine PMs as underrecognized reservoirs of pathogenic bioaerosols during haze episodes. This highlights the limitations in current air quality monitoring frameworks prioritizing PM 2 . 5 chemical composition over biological constituents. We propose urgent regulatory reforms to implement size-resolved bioaerosol standards and deploy real-time pathogen surveillance systems for targeted mitigation of haze-associated respiratory diseases.