BACKGROUND: Ambient particulate matter is classified as a human Class 1 carcinogen, and recent studies found a positive relationship between fine particulate matter (PM(2.5)) and liver cancer. Nevertheless, little is known which specific metal constituent contributes to the development of liver cancer. OBJECTIVE: To evaluate the association of long-term exposure to metal constituents in PM(2.5) with the risk of liver cancer using a Taiwanese cohort study. METHODS: A total of 13,511 Taiwanese participants were recruited from the REVEAL-HBV in 1991-1992. Participants' long-term exposure to eight metal constituents (Ba, Cu, Mn, Sb, Zn, Pb, Ni, and Cd) in PM(2.5) was based on ambient measurement in 2002-2006 followed by a land-use regression model for spatial interpolation. We ascertained newly developed liver cancer (i.e. hepatocellular carcinoma [HCC]) through data linkage with the Taiwan Cancer Registry and national health death certification in 1991-2014. A Cox proportional hazards model was utilized to assess the association between exposure to PM(2.5) metal component and HCC. RESULTS: We identified 322 newly developed HCC with a median follow-up of 23.1 years. Long-term exposure to PM(2.5) Cu was positively associated with a risk of liver cancer. The adjusted hazard ratio (HR) was 1.13 (95% confidence interval [CI]: 1.02, 1.25; p-value=0.023) with one unit increment on Cu normalized by PM(2.5) mass concentration in the logarithmic scale. The PM(2.5) Cu-HCC association remained statistically significant with adjustment for co-exposures to other metal constituents in PM(2.5). CONCLUSIONS: Our findings suggest PM(2.5) containing Cu may attribute to the association of PM(2.5) exposure with liver cancer.
