Objectives: To investigate the association between the heavy metal constituents in PM2.5and liver cancer incidence or death in a large Taiwanese cohort. Methods: A subset of 13,515 participants of the REVEAL-HBV cohort who lived in Taiwan (excluding outlying islands) during 1991-1992 was adopted for this study. Patients with liver cancer were identified through computerized data linkage with the national cancer registry and death certification systems during 1993-2014. Long-term exposure levels to eight metal constituents of PM2.5(i.e., Ba, Cu, Mn, Sb, Zn, Pb, Ni, and Cd) during 2002-2006 were determined using land-use regression models. Cox proportional hazards models were used to estimate the hazard ratios (HRs) of PM2.5metal components on liver cancer incidence or death, after adjustment for potential confounders. To investigate mutual confounding effects, we further applied two-pollutant models for evaluation of the association between metal constituents of PM2.5and liver cancer. Results: During a median follow-up of 23.2 years, 322 cases of liver cancer or death were identified. With a one-unit increment on a log scale, the adjusted HR of PM2.5Cu was 1.15 (95% confidence intervals [CIs]: 1.03-1.29). In addition, the association between PM2.5Cu and liver cancer incidence or death was significant. The two-pollutant model revealed a positive association of PM2.5Cu with liver cancer incidence or death (HR = 1.13, 95% CI: 1.00-1.27). Conclusions: The findings suggest that exposure to metals within ambient PM2.5, and PM2.5Cu in particular, may increase the risk of liver cancer occurrence or death.
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