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.-glutamyl transferase (GGT) levels were measured. A satellitebased spatio-temporal model was used to estimate the concentrations of ambient fine particles (PM with an aerodynamic diameter <= 2.5 mu m, PM2.5) at each participant's address. Linear and logistic regression models were used to investigate the associations between PM2.5 and the liver enzymes with adjustment for a wide range of potential confounders. Results After adjustment for confounders, every 10 mu g/ m(3) increment in 2-year average PM2.5 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 I U/L) per 10 mu g/m(3) PM2.5 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 PM2.5 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.