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Background and Objective: When multiple complex air pollutants are combined in real-world settings, the reliability of estimating the effect of a single pollutant is questionable. This study aimed to investigate the combined effects of changes in air pollutants on small airway dysfunction (SAD)., Methods: We analysed Korea National Health and Nutrition Examination Survey (KNHANES) V-VIII database from 2010 to 2018 to elucidate the associations between annual changes in air pollutants over a previous 5-year period and small airway function. We estimated the annual concentrations of five air pollutants: NO 2 , O 3 , PM 2.5 , SO 2 and CO. Forced expiratory flow between 25% and 75% of vital capacity (FEF 25%-75% ) <65% was defined as SAD. Using the quantile generalized-Computation (g-Computation) model, the combined effect of the annual changes in different air pollutants was estimated., Results: A total of 29,115 individuals were included. We found significant associations between SAD and the quartiles of annual changes in NO 2 (OR = 1.10, 95% CI = 1.08-1.12), O 3 (OR = 1.03, 95% CI = 1.00-1.05), PM 2.5 (OR = 1.03, 95% CI = 1.00-1.05), SO 2 (OR = 1.04, 95% CI = 1.02-1.08) and CO (OR = 1.16, 95% CI = 1.12-1.19). The combined effect of the air pollutant changes was significantly associated with SAD independent of smoking (OR = 1.31, 95% CI = 1.26-1.35, p-value <0.001), and this trend was consistently observed across the entire study population and various subgroup populations. As the estimated risk of SAD, determined by individual-specific combined effect models, increased and the log odds for SAD increased linearly., Conclusion: The combined effect of annual changes in multiple air pollutant concentrations were associated with an increased risk of SAD., (© 2024 Asian Pacific Society of Respirology.)