Xuannian Li ¹ Suqi Liu ² Nan Jiang ² Fei Xu ³ Huaman Liu ⁴ Xinhua Jia ^5*

• ¹ The First College of Clinical Medicine, Shandong University of Traditional Chinese Medicine, Jinan, Shandong, Jinan, Shandong Province, China
• ² First College of Clinical Medicine, Shandong University of Traditional Chinese Medicine, Jinan, Shandong Province, China
• ³ Department of Geriatric Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong Province, China
• ⁴ Department of General Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong Province, China
• ⁵ Department of Pneumology and Critical Care Medicine, Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, Shandong Province, China

Abstract Objectives Our study aims to clarify the causality between air pollutants and lung function, chronic respiratory diseases, and the potential mediating effects of inflammatory proteins. Method We employed Mendelian Randomization (MR) analysis with comprehensive instrumental variables screening criteria to investigate the effects of air pollutants on lung function and chronic lung diseases. Our study incorporated genetic instruments for air pollutants, ensuring F-statistics above 20.86. A total of 18 MR analyses were conducted using the inverse-variance weighted approach, along with heterogeneity and pleiotropy tests to validate the results. Mediated MR analysis was utilized to evaluate the inflammatory proteins mediating the effects of air pollutants. Result MR analysis demonstrated significant causal interactions of particulate matter 2.5 (PM2.5), PM10, and Nitrogen dioxide (NO2) with lung function decline. Specifically, PM10 negatively affected forced expiratory volume in one second (FEV1) (OR: 0.934, 95% CI: 0.904–0.965, P = 4.27×10-5), forced vital capacity (FVC) (OR: 0.941, 95% CI: 0.910–0.972, P = 2.86×10-4), and FEV1/FVC (OR: 0.965, 95% CI: 0.934–0.998, P = 0.036). PM2.5 and NO2 were identified as potential risk factors for impairing FEV1 (OR: 0.936, 95% CI: 0.879–0.998, P = 0.042) and FEV1/FVC (OR: 0.943, 95% CI: 0.896–0.992, P = 0.024), respectively. For chronic respiratory diseases, PM2.5 and NO2 were associated with increased COPD incidence (OR: 1.273, 95% CI: 1.053–1.541, P = 0.013 for PM2.5; OR: 1.357, 95% CI: 1.165–1.581, P = 8.74×10-5 for NO2). Sensitivity analyses confirmed the robustness of these findings, with no significant heterogeneity or horizontal pleiotropy detected. Conclusion Our study ascertained the causal correlations of air pollutants with lung function and COPD, emphasizing the importance of reducing air pollution. Interleukin-17A mediates the reduction of FEV1 and FVC by PM10, revealing potential therapeutic targets.