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VOLUME 1 ISSUE 2 OCT- DEC 2025

Health Burden of Ambient Air Pollution on Respiratory Diseases in the Delhi–National Capital Region (2010–2025): A Systematic Review and Meta-analysis

Pradeep Kumar Soothewal

Introduction: Ambient air pollution is a major contributor to respiratory morbidity and mortality globally, with disproportionate impacts in low- and middle-income countries. The Delhi–National Capital Region (NCR) experiences persistently high levels of air pollution, yet region-specific quantitative syntheses of respiratory health impacts remain limited. This study aimed to systematically review and meta-analyse epidemiological evidence on the association between ambient air pollution and respiratory outcomes in Delhi–NCR from 2010 to 2025.

Methods: A systematic review and meta-analysis were conducted in accordance with PRISMA 2020 guidelines. PubMed/MEDLINE, Scopus, Web of Science, Embase, and additional sources were searched for eligible studies examining associations between ambient air pollutants (PM₂.₅, PM₁₀, NO₂, SO₂, O₃, CO) and respiratory morbidity or mortality in Delhi–NCR. Time-series, case-crossover, cohort, and observational studies reporting quantitative effect estimates were included. Random-effects meta-analyses were performed to derive pooled relative risks per 10 µg/m³ increase in pollutant concentration. Risk of bias was assessed using adapted ROBINS-E and Newcastle–Ottawa tools.

Results: Ten studies met inclusion criteria for qualitative synthesis, and seven were included in meta-analysis. Short-term increases in PM₂.₅ were associated with higher respiratory emergency visits (RR 1.038; 95% CI: 1.021–1.056) and respiratory mortality (RR 1.019; 95% CI: 1.006–1.033). PM₁₀ exposure was linked to increased respiratory admissions (RR 1.026; 95% CI: 1.012–1.041), while NO₂ showed a strong association with acute respiratory visits (RR 1.041; 95% CI: 1.018–1.064). Heterogeneity ranged from low to moderate.

Conclusion: Ambient air pollution is consistently associated with increased respiratory morbidity and mortality in Delhi–NCR. These findings underscore the urgent need for strengthened air quality interventions and targeted public health strategies in highly polluted urban settings.

Keywords: Ambient air pollution; Respiratory diseases; PM₂.₅; Nitrogen dioxide; Delhi–NCR; Meta-analysis.

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