Impact of ambient particulate matter and meteorological factors on COPD risk and its association with blood eosinophilia

While the association between air pollution and chronic obstructive pulmonary disease (COPD) is well-documented, limited studies investigate the effects of meteorological factors in COPD. The objective of this study is to examine the impact of particulate matter less than < 2.5 μm (PM2.5), temperature and relative humidity (RH) on COPD detection, with a specific focus on the importance of blood eosinophil levels. This case-control study was conducted in Taiwan from December 2010 to April 2022, including 937 COPD patients and 833 controls. The average daily exposure and differences in PM2.5, temperature, and RH over 1-day, 7-day and 1-month periods were calculated using the radial basic function interpolation model. The associations between PM2.5, temperature, and RH with COPD were assessed using logistic regression, and non-linear exposure-response associations were further examined using generalized additive mixed models. We observed that each 1 µg/m³ increase in PM2.5 daily average over the 7-day and 1-month periods were associated with a 1.051-fold and 1.059-fold increase in the odds ratio (OR) of COPD, respectively. The exposure-response curves indicate that individuals with blood eosinophilia (≥ 2%) exhibit consistent increases in the odds of COPD in response to rising PM2.5 levels. The exposure-response relationship between temperature and COPD was also observed in subjects with blood eosinophilia. We observed that a 1-month average PM2.5 was associated with a 1.044-fold increase in the OR of GOLD stages 3–4 among COPD with eosinophil levels ≥ 2%. PM2.5 levels were associated with increased odds of COPD detection, with individuals exhibiting blood eosinophilia being especially vulnerable to PM2.5 exposure and more likely to detect severe COPD. Improving air quality for human health protection is important in response to climate change challenges.