Ambient PM2.5 air pollution exposure and hepatocellular carcinoma incidence in the United States

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/m³ 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/m³ 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.

Keywords: Air pollution; Geographic information system; Hepatocellular carcinoma; Liver cancer; PM2.5; Particulate matter.

Fig. 1

Ambient PM_2.5 exposure (μg/m³) in 2000 by quintiles across 607 counties in the U.S. Higher PM_2.5 levels are shown in darker colors. The PM_2.5 quintiles were calculated using all 607 counties captured by the 16 SEER population-based cancer registries included in the study.