Long-Term Exposure to Nitrogen Dioxide and Ozone and Mortality: Update of the WHO Air Quality Guidelines Systematic Review and Meta-Analysis
Maria‐Iosifina Kasdagli, Pablo Orellano, Román Pérez Velasco, Evangelia Samoli
Abstract
Objectives We performed a systematic review and meta-analysis on long-term exposure to nitrogen dioxide (NO 2 ) and ozone (O 3 ) with mortality, to expand evidence that informed 2021 the WHO Air Quality Guidelines and guide the Health Risks of Air Pollution in Europe project. Methods We included cohorts investigating NO 2 and O 3 mortality from all-causes, respiratory diseases, chronic obstructive pulmonary disease (COPD), acute lower respiratory infections (ALRI); and NO 2 mortality from circulatory, ischemic heart, cerebrovascular diseases and lung cancer. We pooled estimates by random-effects models and investigated heterogeneity. We assessed the certainty of the evidence using the Grading of Recommendations Assessment Development approach and Evaluation (GRADE). Results We selected 83 studies for NO 2 and 26 for O 3 for the meta-analysis. NO 2 was associated with all outcomes, except for cerebrovascular mortality. O 3 was associated with respiratory mortality following annual exposure. There was high heterogeneity, partly explained by region and pollutant levels. Certainty was high for NO 2 with COPD and ALRI, and annual O 3 with respiratory mortality. Conclusion An increasing body of evidence, with new results from countrywide areas and the Western Pacific, supports certainty, including new outcomes.