PM2.5 Constituents and Hospitalizations of a Wide Spectrum of Respiratory Diseases: A Nationwide Case-Crossover Study in China

Few studies have explored the acute effects of fine particulate matter (PM_2.5) constituents on respiratory diseases (RDs), particularly across a broad spectrum of RD subtypes. We analyzed the associations between PM_2.5 and its five major constituents [organic matter (OM), black carbon (BC), sulfate (SO₄^2–), nitrate (NO₃^–), and ammonium (NH₄⁺)] and RDs (10 major categories and 35 specific) based on the hospitalization records from 153 hospitals in 20 provincial distractions from 2013 to 2020. We found that short-term exposure (lag 0–1) to PM_2.5 constituents per interquartile range increase was associated with higher hospitalization risks for acute upper respiratory infections, influenza and pneumonia, other acute lower respiratory infections, chronic lower respiratory diseases, other diseases of the pleura, and other diseases of the respiratory system; the effect estimates were 2.45–2.99%, 2.02–2.71%, 2.98–3.62%, 3.06–3.65%, 3.22–4.52%, and 2.23–3.66%, respectively. Among 35 specific RDs, 12 were significantly affected by PM_2.5 and its constituents. Individuals aged >60 years were sensitive to PM_2.5 constituent exposure. Our individual-level nationwide study provided a more comprehensive perspective on the associations between PM_2.5 constituents and various major and specific RDs, highlighting the necessity of prioritizing targeted control strategies for key constituents to effectively mitigate the burden of RDs in China.