Ambient PM₁ on COPD mortality: insights from a population-based study

Evidence on the short-term association between particulate matter with an aerodynamic diameter of ≤1 µm (PM1) and mortality from chronic obstructive pulmonary disease (COPD) is scarce. We aimed to explore the potential effects of PM1 on COPD mortality. We conducted a province-wide time-stratified case-crossover study in 13 cities of Jiangsu province, China, from 2015 to 2019. Daily mortality data were collected and PM1 at the individual level was estimated using a gridded dataset (10 km × 10 km) linked to personal residential addresses. The effects of PM1 on COPD mortality were evaluated using conditional logistic regression. We also investigated the exposure-response relations and potential effect modifiers. A total of 255 043 COPD deaths were included in data analyses. Each 10 μg/m3 increase in PM1 was associated with increased mortality risk of 3.32% (2.67%-3.97%) for COPD, 3.75% (2.30%-5.22%) for chronic bronchitis, 3.25% (1.09%-5.45%) for emphysema and 3.35% (2.56%-4.15%) for acute exacerbation of COPD (AECOPD), respectively. Natural cubic splines analysis revealed linear relationships for PM1 and COPD mortality. Particulate matter with an aerodynamic diameter of ≤2.5 µm (PM2.5) had slightly weaker effects on COPD mortality than PM1. Population attributable fractions for PM1-related mortality from COPD, chronic bronchitis, emphysema and AECOPD were 8.86%, 8.84%, 8.25% and 8.86%, respectively. This study provides new evidence of an association between short-term exposure to PM1 and COPD mortality. Our findings suggest a predominant role of PM1 within PM2.5 and emphasise the need for targeted strategies to reduce PM1 concentrations.