Ambient Air Pollution and Risk of ARDS and Mortality in Moderate to Severe COVID-19

Background and Objective: Ambient air pollution is known to exacerbate respiratory illnesses. However, its impact on COVID-19 outcomes remains underexplored. We investigated the association between ambient air pollution and outcomes in patients with moderate to severe COVID-19. Methods: We analysed 1867 hospitalized patients from a multicentre Korean cohort. Individual-level exposure to five air pollutants (SO₂, CO, NO₂, PM₁₀ and PM_2.5) was assessed over short-term (3-day) and long-term (3-year) periods. The risks of acute respiratory distress syndrome (ARDS) and 30-day mortality were evaluated using models adjusted for clinical and meteorological factors. Pollutant exposure was analysed both as quartiles and continuous variables to estimate effects per unit increase. Results: Short-term CO exposure was associated with increased ARDS incidence (per 0.1 ppm increase OR 1.18) and 30-day mortality (HR 1.15). Long-term NO₂ exposure was associated with higher ARDS risk (per 1 ppb OR 1.11). Long-term PM₁₀ exposure was also associated with ARDS incidence (per 10 μg/m³ OR 2.24). For mortality, short-term NO₂ (per 1 ppb HR 1.02) and PM_2.5 (per 10 μg/m³ HR 1.14) exposure were additionally associated with increased risk. These associations were consistent in quartile-based analyses. Conclusion: Both short- and long-term exposure to ambient air pollution were associated with worse COVID-19 outcomes, including ARDS and mortality. CO, often overlooked in pollution surveillance, showed the most consistent impact. These findings highlight the importance of air quality in pandemic preparedness and public health policy. (Figure presented.).