NON-ALCOHOLIC fatty liver disease (NAFLD) is now the most common chronic liver disease worldwide and presents a growing burden for health systems, particularly in urban areas. While the role of lifestyle and metabolic factors in NAFLD development is well-established, the potential contribution of environmental exposures, such as air pollution, remains underexplored. A recent study aimed to address that gap by systematically evaluating whether air pollutants are associated with increased NAFLD risk. The key finding is that exposure to several major air pollutants, including PM2.5, PM10, NO₂ and NOx, is linked with a significantly higher risk of developing NAFLD.
A comprehensive literature search was carried out across four databases: Embase, Web of Science, PubMed, and the Cochrane Library, covering studies published up to 4 February 2025. Eligible studies were assessed for quality using the Newcastle-Ottawa Scale (NOS) for cohort studies and the Agency for Healthcare Research and Quality (AHQR) scale for cross-sectional studies. Pooled risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using Stata 16.0 to quantify the strength of association between pollutant exposure and NAFLD incidence.
10 studies met the inclusion criteria. Meta-analysis revealed that higher concentrations of PM2.5 (RR: 1.24; 95% CI: 1.18–1.44), PM10 (RR: 1.24; 95% CI: 1.13–1.36), NO₂ (RR: 1.22; 95% CI: 1.09–1.37), and NOx (RR: 1.24; 95% CI: 1.14–1.36) were associated with a significantly increased risk of NAFLD. Additionally, each unit increase in PM1 (RR: 1.15), PM2.5 (RR: 1.15), PM10 (RR: 1.10), NO₂ (RR: 1.13), and NOx (RR: 1.10) also raised NAFLD risk, suggesting a dose–response relationship.
These results highlight a potentially important environmental determinant of NAFLD and call for greater consideration of air quality in liver disease prevention strategies. However, several limitations must be acknowledged. The high heterogeneity across studies, limited number of high-quality investigations, and variation in study design reduce the ability to draw firm causal conclusions. From a clinical perspective, these findings underscore the importance of factoring environmental exposures into NAFLD risk assessments, particularly for individuals living in high-pollution areas. Public health policies may need to broaden their scope beyond individual behavioural risk factors to include urban air quality as part of liver disease prevention frameworks.
Reference
Zhu Z et al. Association between exposure to air pollutants and NAFLD/MAFLD: a meta-analysis. BMC Public Health. 2025;25(1):2672.
