Abstract
PURPOSE: To conduct the first epidemiologic study prospectively examining the association between particulate matter air pollution < 2.5 µm in diameter (PM(2.5)) exposure and hepatocellular carcinoma (HCC) risk in the U.S. METHODS: Surveillance, Epidemiology, and End Results (SEER) provided information on HCC cases diagnosed between 2000 and 2014 from 16 population-based cancer registries across the U.S. Ambient PM(2.5) exposure was estimated by linking the SEER county with a spatial PM(2.5) model using a geographic information system. Poisson regression with robust variance estimation was used to calculate incidence rate ratios and 95% confidence intervals (CIs) for the association between ambient PM(2.5) exposure per 10 µg/m(3) increase and HCC risk adjusting for individual-level age at diagnosis, sex, race, year of diagnosis, SEER registry, and county-level information on health conditions, lifestyle, demographic, socioeconomic, and environmental factors. RESULTS: Higher levels of ambient PM(2.5) exposure were associated with a statistically significant increased risk for HCC (n = 56,245 cases; adjusted IRR per 10 µg/m(3) increase = 1.26, 95% CI 1.08, 1.47; p < 0.01). CONCLUSIONS: If confirmed in studies with individual-level PM(2.5) exposure and risk factor information, these results suggest that ambient PM(2.5) exposure may be a risk factor for HCC in the U.S.