Association of long-term exposure to ambient PM2.5 and its constituents with gut microbiota: Evidence from a China cohort

Accumulating animal experiments and epidemiological studies have found that exposure to fine particulate matter (PM2.5) is associated with altered gut microbiota (GM). However, it is unclear what kind of role the PM2.5 constituents play in the PM2.5-GM association. Therefore, this study aimed to investigate the association of long-term exposure to PM2.5 and its constituents (PMcons) with GM. This study included 1583 participants from a cohort in Southwest China. Satellite remote sensing and chemical transport modelling were used to determine the yearly average concentrations of PMcons. GM data were derived from 16 s sequencing based on stool samples. Generalized propensity score weighting regression and Bayesian Kernel Machine Regression (BKMR) were used to estimate the individual and joint association of exposure to PMcons with the Shannon index. The weighted correlation analysis was used to estimate the association of PMcons with the composition of GM. The result showed that an interquartile range increase of 3-year average black carbon (BC), ammonium, nitrate, organic matter (OM), sulfate, and soil particles (SOIL) were negatively associated with Shannon index with mean difference (95 % confidence interval) being -0.144 (-0.208, -0.080), -0.141 (-0.205, -0.078), -0.126 (-0.184, -0.068), -0.117 (-0.172, -0.062), -0.153 (-0.221, -0.085), and - 0.153 (-0.222, -0.085). BKMR indicated joint exposure to PMcons was associated with decreased Shannon index, and BC had the largest posterior inclusion probability (0.578). Weighted correlation analyses indicated PMcons were associated with decreased Bacteroidetes (r = -0.204, P < 0.001 for PM2.5) and increased Proteobacteria (r = 0.273, P < 0.001 for PM2.5). These results revealed that long-term exposure to PMcons was associated with GM. BC was the most important constituent in the association, indicating that the source of BC should be controlled to mitigate the negative effects of PM2.5 on GM.