Airway microbiome is associated with respiratory functions and responses to ambient particulate matter exposure

Background: Ambient particulate matter (PM) exposure has been associated with respiratory function decline in epidemiological studies. We hypothesize that a possible underlying mechanism is the perturbation of airway microbiome by PM exposure. Methods: During October 2016–October 2017, on two human cohorts (n = 115 in total) in Shanghai China, we systematically collected three categories of data: (1) respiratory functions, (2) airway microbiome from sputum, and (3) PM_2.5 (PM of ≤ 2.5 µm in diameter) level in ambient air. We investigated the impact of PM_2.5 on airway microbiome as well as the link between airway microbiome and respiratory functions using linear mixed regression models. Results: The respiratory function of our primary interest includes forced vital capacity (FVC) and forced expiratory volume in 1st second (FEV₁). FEV₁/FVC, an important respiratory function trait and key diagnosis criterion of COPD, was significantly associated with airway bacteria load (p = 0.0038); and FEV₁ was associated with airway microbiome profile (p = 0.013). Further, airway microbiome was significantly influenced by PM_2.5 exposure (p = 4.48E-11). Conclusions: To our knowledge, for the first time, we demonstrated the impact of PM_2.5 on airway microbiome, and reported the link between airway microbiome and respiratory functions. The results expand our understanding on the scope of PM_2.5 exposure's influence on human respiratory system, and point to novel etiological mechanism of PM_2.5 exposure induced diseases.