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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., Competing Interests: The authors declare that they do not have any conflicts of interest., (Copyright © World Health Organization 2024. Licensee Frontiers Media SA and Stiftung Swiss School of Public Health plus.)

Objectives: For the development of the 2021 global air quality guidelines, the World Health Organization (WHO) commissioned a series of systematic reviews and meta-analyses to assess the association between exposure to air pollution and all-cause and cause-specific mortality. One of these reviews, which we aim to update, focused on the effects of long-term exposure to PM 2.5 and PM 10 on all-cause and cause-specific mortality., Methods: The protocol for this study was registered in PROSPERO (CRD42023425327). We searched the PubMed and Embase databases for studies published between September 2018 and May 2023. Study-specific effects were pooled using random-effects models., Results: We included 106 studies in the meta-analysis, 46 studies from the previous review and 60 from this update. All exposure-outcome pairs analysed showed positive and significant associations, except for PM 10 and cerebrovascular mortality. The certainty of the evidence was rated as high for the majority of exposure-outcome pairs., Conclusion: We included a large number of new cohorts, and provided new concentration-response functions that will inform WHO advice on the use of this information for air pollution health risk assessments., Competing Interests: The authors declare that they do not have any conflicts of interest., (Copyright © World Health Organization 2024. Licensee Frontiers Media SA and Stiftung Swiss School of Public Health plus.)

Background: We evaluated the independent and joint effects of air pollution, land/built environment characteristics, and ambient temperature on all-cause mortality as part of the EXPANSE project., Methods: We collected data from six administrative cohorts covering Catalonia, Greece, the Netherlands, Rome, Sweden, and Switzerland and three traditional cohorts in Sweden, the Netherlands, and Germany. Participants were linked to spatial exposure estimates derived from hybrid land use regression models and satellite data for: air pollution [fine particulate matter (PM 2.5 ), nitrogen dioxide (NO₂), black carbon (BC), warm season ozone (O 3 )], land/built environment [normalized difference vegetation index (NDVI), distance to water, impervious surfaces], and ambient temperature (the mean and standard deviation of warm and cool season temperature). We applied Cox proportional hazard models accounting for several cohort-specific individual and area-level variables. We evaluated the associations through single and multiexposure models, and interactions between exposures. The joint effects were estimated using the cumulative risk index (CRI). Cohort-specific hazard ratios (HR) were combined using random-effects meta-analyses., Results: We observed over 3.1 million deaths out of approximately 204 million person-years. In administrative cohorts, increased exposure to PM 2.5 , NO 2 , and BC was significantly associated with all-cause mortality (pooled HRs: 1.054, 1.033, and 1.032, respectively). We observed an adverse effect of increased impervious surface and mean season-specific temperature, and a protective effect of increased O 3 , NDVI, distance to water, and temperature variation on all-cause mortality. The effects of PM 2.5 were higher in areas with lower (10th percentile) compared to higher (90th percentile) NDVI levels [pooled HRs: 1.054 (95% confidence interval (CI) 1.030-1.079) vs. 1.038 (95% CI 0.964-1.118)]. A similar pattern was observed for NO 2 . The CRI of air pollutants (PM 2.5 or NO 2 ) plus NDVI and mean warm season temperature resulted in a stronger effect compared to single-exposure HRs: [PM 2.5 pooled HR: 1.061 (95% CI 1.021-1.102); NO 2 pooled HR: 1.041 (95% CI 1.025-1.057)]. Non-significant effects of similar patterns were observed in traditional cohorts., Discussion: The findings of our study not only support the independent effects of long-term exposure to air pollution and greenness, but also highlight the increased effect when interplaying with other environmental exposures., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer-review process and the final decision., (© 2024 Dimakopoulou, Nobile, de Bont, Wolf, Vienneau, Ibi, Coloma, Pickford, Åström, Sommar, Kasdagli, Souliotis, Tsolakidis, Tonne, Melén, Ljungman, de Hoogh, Vermeulen, Vlaanderen, Katsouyanni, Stafoggia and Samoli.)