Association of air pollution and emphysema in chronic obstructive pulmonary disease: the role of eosinophil cell

The effect of air pollution on respiratory diseases, including chronic obstructive pulmonary disease (COPD), has been well-documented. However, there are limited studies on the association between air pollution and emphysema in COPD. Moreover, the role of urban climate in the association between air pollution and the risk of COPD has not been fully explored. To investigate the impact of air pollution exposure and deposition on lung function and emphysema severity in COPD, a pulmonary function tests and lung images of 111 COPD patients with emphysema were collected. We used a land use regression (LUR) model to estimate individual air pollution concentrations, including PM with an aerodynamic diameter ≤ 10μm (PM10), PM2.5, nitrogen oxide (NOx), and nitrogen dioxides (NO2) based on their home addresses. We used multiple-path particle deposition (MPPD) to calculate the amount of particle deposition in the lung. We observed that particulate matter (PM) exposure and deposition was associated with a decrease lung function in COPD patients. Deposition of PM in the lung resulted in higher severity of emphysema in the lower lobe region. Similarly, a higher impact of particle deposition was found in the lower lobe region of COPD patients with blood eosinophilia.
Moreover, to examine the association between air pollution exposure and the health outcomes of COPD with blood eosinophilia, we collected lung function tests, blood eosinophils counts, and overall health status of 291 COPD patients. We found that air pollution exposure was associated with decreased lung function in COPD patients. A notable association between air pollution and lung function decrease was found in males, former smoker and severe COPD patients. A stronger association between air pollution exposure and health outcomes was found in COPD patients with blood eosinophilia, including decreased lung function, lower quality of life and a higher frequency of acute exacerbations.
Considering the effect of urban climate on the association between air pollution exposure and the risk of COPD in individuals with blood eosinophilia, we collected a spirometry test data and blood eosinophil levels of 937 COPD patients and 833 control subjects. A radial basic function (RBF) interpolation approach was used to calculate the daily concentrations of air pollution, temperature and relative humidity (RH) based on their home locations. We observed that exposure to the average daily PM2.5 was associated with an increased risk of COPD. The average daily of difference in PM2.5 and temperature was associated with COPD risk. The average of daily exposure to PM2.5 and temperature was associated with the risk of COPD in individuals with blood eosinophilia. These findings highlight that air pollution, particularly PM10 and PM2.5, contributes to the increased severity emphysema in COPD. Furthermore, COPD patients with blood eosinophilia are a population at risk of air pollution exposure and climate change.
In conclusion, exposure to air pollution and particle deposition exacerbates lung function decrease and emphysema severity in COPD patients, particularly in individuals with blood eosinophilia, underscoring their susceptibility to air pollution and climate change. Reducing air pollution levels and mitigating climate change could improve the stability of COPD patients, especially those with blood eosinophilia.