Air pollution and cause-specific mortality in EU: a review integrating meta-analysis and meta-regression

Ambient air pollution remains a major public health concern in Europe despite recent improvements. This systematic review synthesizes evidence (2020-2025) on short- and long-term effects of PM₁₀, PM_2.5, NO₂ and O₃ on cause-specific mortality, integrating Italian BEEP and BIGEPI projects with European studies for the first time. Searches of PubMed, Web of Science, and Scopus (to 31 July 2025) identified 31 studies; meta-analyses were conducted when ≥ 5 studies were available (18 studies included for PM_2.5). Risk of bias was assessed using ROBINS-E (v1, June 2023) by two independent reviewers. PM_2.5 was significantly associated with mortality: all-cause RR ≈ 1.10 per 10 µg/m³ (I²=97.9%), cardiovascular RR = 1.026 (95%CI 1.014-1.039; I²=91.7%), and respiratory RR = 1.032 (95%CI 1.013-1.050; I²=88.3%), with stronger effects for long-term exposure. Long-term PM_2.5 and NO₂ exposures were consistently linked to increased all-cause, cardiovascular, and respiratory mortality; PM₁₀ showed weaker associations. Short-term increases in PM and NO₂ were associated with acute mortality rises, while O₃ evidence was heterogeneous. Limitations include substantial heterogeneity (I² 78-98%), evidence of small-study effects (Egger p < 0.05), and risk of bias rated "Some concerns" in most studies (16/18). Overall, air pollution continues to impose a measurable mortality burden in Europe, supporting stricter standards aligned with WHO guidelines. Funding: PNC PREV- A-2022-12376981.