Tehran University of Medical Sciences Journal of Air Pollution and Health 2476-3071 10 4 2025 12 28 569 588 Behrooz Karimi Department of Environmental Health Engineering, Health Faculty, Arak University of Medical Sciences, Arak, Iran Maedeh Moradi Farahani Student Research Committee, Arak University of Medical Sciences, Arak, Iran 2025 03 12 2025 11 01 A growing body of evidence implicates ambient air pollution in the exacerbation of clinical outcomes after SARS-CoV-2 infection. To synthesize this evidence, we performed a global systematic review and meta-analysis to precisely quantify the associations between exposure to specific atmospheric  ontaminants and the subsequent risks of COVID-19-related mortality and hospital admission. Our methodology adhered to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) framework, involving a comprehensive search of scientific databases for literature published until the end of August 2025. From this search, 44 publications were deemed eligible for inclusion. We employed random-effects models to compute summary Risk Ratios (RRs) representing the change in health risk per 1 µg/m³ increment in atmospheric pollutant concentration. Our findings indicate that long term exposure to fine Particulate Matter (PM2.5), coarse Particles (PM₁₀), Nitrogen dioxide (NO₂), and Sulfur dioxide (SO₂) significantly increased the likelihood of fatal outcomes from COVID-19. The respective pooled RRs were 1.046 (95% CI: 1.031–1.062), 1.079 (95% CI: 1.005–1.154), 1.017 (95% CI: 1.004–1.029), and 1.077 (95% CI: 1.021–1.133). Acute exposures to ambient PM2.5 and NO₂ concentrations were similarly associated with increased mortality, demonstrating risk ratios of 1.043 (95% CI: 1.033–1.053) and 1.033 (95% CI: 1.019–1.048) respectively per 1 µg/m³ increment. Additionally, both acute and chronic exposures to PM2.5, PM₁₀, and NO₂ showed significant associations with higher COVID-19 hospitalization rates. This meta-analysis provides robust quantitative suggestion that ambient PM2.5, PM10, NO₂, and SO₂ are significant and modifiable risk factors for severe COVID-19 outcomes. These results emphasize the critical need for enhanced air quality standards as a fundamental element of public health policy to alleviate the impact of COVID-19 and bolster defenses against forthcoming respiratory epidemics. https://japh.tums.ac.ir/index.php/japh/article/view/932 https://japh.tums.ac.ir/index.php/japh/article/download/932/458