A meta-analysis and systematic review on the association between air pollution and chronic liver diseases

Air pollution represents the second most significant global health burden, and existing epidemiological studies have reported that air pollution is harmful to the liver. To comprehensively understand the relationship between air pollution and liver health, this study quantitatively assessed the effects of air pollutants on liver diseases based on published population studies.

46 papers from PubMed, Cochrane Library, and Web of Science were included in this study. The study we included covered Asia, Europe, and the Americas, mainly from China (23/46), the United States (7/46), and the United Kingdom (3/46). This study has been registered on PROSPERO (CRD42024515689). A WHO-approved risk of bias (ROB) assessment tool specialized for air quality research was applied to evaluate the bias in the included studies. Statistical analyses were performed in R 4.3.2 with fixed/random-effects models (threshold: I²>50%). Effect values (odds ratio [ORs]/weighted mean differences [WMDs]) were standardized per 10 μg/m³ increment, with sensitivity analysis (leave-one-out), and publication bias tests (Begg/Egger) at P < 0.05. The results indicated that each 10 μg/m³ increment in particulate matter 2.5 mum (PM_2.5) was associated with increased levels of aspartate aminotransferase (AST) (3.25%, 95% CI: 0.87-5.68), alanine aminotransferase (ALT) (1.82%, 95% CI: 0.60-3.04), and gamma-glutamyl transferase (GGT) (1.86%, 95% CI: 0.70-3.01); as well as increased risk of metabolic dysfunction-associated fatty liver disease (MAFLD) (OR = 1.32, 95% CI: 1.21-1.44), liver cancer incidence (OR = 1.22, 95% CI: 1.11-1.35), and liver cancer mortality (OR = 1.47, 95% CI: 1.14-1.90). Particulate matter 10 mum (PM₁₀) and nitrogen dioxide (NO₂) exposure also correlated with elevated liver enzymes. The present study has demonstrated that long-term exposure to air pollutants was associated with a higher risk of developing liver diseases in comparison to short-term exposure. The cohort study yielded more statistically significant findings than the cross-sectional study.

The evidence presented in this study suggested that air pollution was associated with an increased risk of liver enzyme abnormality, incidence of MAFLD, as well as incidence and mortality of liver cancer, reminding the public, environmental and clinical experts, to pay attention to the liver health associated with air pollution.