Long-term exposure to ambient fine particulate matter and liver enzymes in adults: a cross-sectional study in Taiwan

Objectives: Animal experiments indicate that exposure to particulate matter (PM) can induce hepatotoxic effects but epidemiological evidence is scarce. We aimed to investigate the associations between long-term exposure to PM air pollution and liver enzymes, which are biomarkers widely used for liver function assessment.

Methods: A cross-sectional analysis was performed among 351 852 adult participants (mean age: 40.1 years) who participated in a standard medical screening programme in Taiwan. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and γ-glutamyl transferase (GGT) levels were measured. A satellite-based spatio-temporal model was used to estimate the concentrations of ambient fine particles (PM with an aerodynamic diameter ≤2.5 µm, PM_2.5) at each participant's address. Linear and logistic regression models were used to investigate the associations between PM_2.5 and the liver enzymes with adjustment for a wide range of potential confounders.

Results: After adjustment for confounders, every 10 µg/m³ increment in 2-year average PM_2.5 concentration was associated with 0.02%(95% CI: -0.04% to 0.08%), 0.61% (95% CI: 0.51% to 0.70%) and 1.60% (95% CI: 1.50% to 1.70%) increases in AST, ALT and GGT levels, respectively. Consistently, the odds ratios of having elevated liver enzymes (>40 IU/L) per 10 µg/m³ PM_2.5 increment were 1.06 (95% CI: 1.04 to 1.09), 1.09 (95% CI: 1.07 to 1.10) and 1.09 (95% CI: 1.07 to 1.11) for AST, ALT and GGT, respectively.

Conclusions: Long-term exposure to PM_2.5 was associated with increased levels of liver enzymes, especially ALT and GGT. More studies are needed to confirm our findings and to elucidate the underlying mechanisms.