Tehran University of Medical Sciences Journal of Air Pollution and Health 2476-3071 11 3 2026 09 13 307 324 Sachin Admane Department of Civil Engineering, Sanjivani College of Engineering, Kopargaon, India Tejas Admane School of Civil and Environmental Sciences JSPM University Pune, Maharashtra, India Aditi Admane Faculty of Medicine, Kasr Al Ainy, Cairo University, Cairo, Egypt Sanket Kasture Faculty of Medicine, Kasr Al Ainy, Cairo University, Cairo, Egypt 2026 01 24 2026 07 22 Introduction: Short-term associations between ambient air pollution and cardiovascular morbidity remain inconsistent across different settings. This study evaluated these associations using Generalized Additive Models (GAMs) and examined the robustness of the findings through lag and sensitivity analyses. Materials and methods: An ecological time-series analysis was conducted using a publicly available environmental–health dataset comprising 5,811 daily observations of air pollutant concentrations, meteorological variables, and aggregated cardiovascular morbidity indicators. GAMs with penalized smoothing splines were fitted to assess potentially non-linear exposure–response relationships while adjusting for meteorological covariates. Lag structures (Lag 0–3 days), alternative spline dimensions, and multi-pollutant models were evaluated as sensitivity analyses. Results: The final GAM demonstrated limited explanatory capacity (AIC=25,602.9; AICc=25,604.6; explained deviance=1.04%). Pollutant smooth terms showed shallow non-linear exposure–response patterns (effective degrees of freedom: 8.36-9.40), but none were statistically significant (PM₂.₅: p=0.357; PM₁₀: p=0.950; NO₂: p=0.594; SO₂: p=0.339; O₃: p=0.530). Sensitivity analyses produced consistent results across alternative lag structures and spline dimensions, and model diagnostics indicated satisfactory fit without evidence of substantial over dispersion. Conclusion: Only shallow, statistically non-significant short-term associations were identified. These findings should be interpreted within the limitations of the ecological design, potential exposure misclassification, and residual confounding. https://japh.tums.ac.ir/index.php/japh/article/view/1208 https://japh.tums.ac.ir/index.php/japh/article/download/1208/476