Fine particulate matter, airway inflammation, stress response, non-specific immune function and buccal microbial...

Fine particulate matter (PM_2.5) has been associated with risk of oral and respiratory diseases. However, the biological mechanisms of adverse oral and respiratory health response to PM_2.5 fluctuation have not been well characterized. This study aims to explore the relationships of PM_2.5 with airway inflammation, salivary biomarkers and buccal mucosa microbiota. We performed a panel study among 40 college students involving 4 follow-ups from August to October 2021 in Hefei, Anhui Province, China. Health outcomes included fractional exhaled nitric oxide (FeNO), salivary biomarkers [C-reactive protein (CRP), cortisol, lysozyme and alpha-amylase] and buccal mucosa microbial diversity. Linear mixed-effect models were applied to explore the cumulative impacts of PM_2.5 on health indicators. PM_2.5 was positively correlated with FeNO, CRP, cortisol and alpha-amylase, while negatively with lysozyme. Per 10-μg/m³ increase in PM_2.5 was linked to maximum increments in FeNO of 10.71% (95%CI: 2.01%, 19.41%) at lag 0-24 h, in CRP of 7.10% (95%CI: 5.39%, 8.81%) at lag 0-24 h, in cortisol of 1.25% (95%CI: 0.44%, 2.07%) at lag 0-48 h, and in alpha-amylase of 2.12% (95%CI: 0.53%, 3.71%) at lag 0-24 h, while associated with maximum decrement in lysozyme of 0.53% (95%CI: 0.12%, 0.95%) at lag 0-72 h. Increased PM_2.5 was linked to reduction in the richness and evenness of buccal microbe and o_Bacillales and o_Bacteroidales were identified as differential microbes after PM_2.5 inhalation. Bio-information analysis indicated that immunity system pathway was the most important enriched abundant process altered by PM_2.5 exposure. In summary, short-term PM_2.5 exposure may impair oral and respiratory health by inducing inflammatory and stress responses, weakening immune function and altering buccal mucosa microbial diversity.