Background <p>Randomized trials have not assessed how changing dietary patterns affects air pollution-related chronic diseases and mortality. We estimated these risks under hypothetical dietary interventions.</p> Methods <p>17,254 UK Biobank adults with repeated 24-h dietary assessments (2009–2012) were included. Exposures to six air pollutants (PM_2.5, PM₁₀, NO₂, NO_X, SO₂, and benzene) were estimated using the bilinear interpolation algorithm. Outcomes included incident cardiovascular disease (CVD), diabetes, cancer, chronic kidney disease (CKD), chronic obstructive pulmonary disease (COPD), dementia, and all-cause mortality. Eleven dietary patterns were calculated. Using the parametric g-formula, we simulated interventions increasing dietary scores (75th/90th percentiles, optimal adherence), estimating 13-year cumulative risks and risk difference (RD) for outcomes associated with air pollutant mixtures.</p> Results <p>Over 12.9 median follow-up years, 2295 CVD, 475 diabetes, 1912 cancer, 969 CKD, 395 COPD, 405 dementia cases, and 814 deaths occurred. Increased adherence to ten dietary patterns (excluding the healthy low-carbohydrate diet) reduced air pollution-related disease risks, with maximal benefit at optimal adherence. For example, comparing interventions targeting dietary diversity score with non-intervention, the 13-year RD (per 1000 population) ranged from − 0.48 to − 2.14 for CVD, − 2.85 to − 10.16 for diabetes, − 0.65 to − 2.95 for cancer, − 4.26 to − 16.22 for CKD, − 2.79 to − 9.60 for COPD, − 3.64 to − 12.12 for dementia, and − 2.54 to − 9.84 for death.</p> Conclusions <p>Interventions optimizing dietary patterns could mitigate the 13-year risks of major chronic diseases and mortality linked to air pollutant mixtures. Adherence to healthy dietary patterns holds significant public health potential for preventing air pollution-related morbidity and premature death.</p> Graphical Abstract <p></p>