Ambient Air Pollution and Primary Liver Cancer Incidence in Four European Cohorts Within the ESCAPE Project.

Abstract

Background: Tobacco smoking increases the risk of liver cancer, but little is known about possible risks associated with ambient air pollution. Methods: We evaluated the association between exposure to air pollution and primary liver cancer incidence. We obtained data from four cohorts with enrollment during 1985-2005 in Denmark, Austria and Italy. Nitrogen oxides (NO2 and NOX), particulate matter (PM) with diameter of less than 10 μm (PM10), less than 2.5 μm (PM2.5), between 2.5 and 10 μm (PM2.5-10) and PM2.5 absorbance concentrations at baseline home addresses were estimated using standardized land-use regression models from the ESCAPE project. We also investigated traffic density on the nearest road. We used Cox proportional-hazards models with adjustment for potential confounders for cohort-specific analyses and meta-analyses to estimate summary hazard ratios (HRs). Results: Out of 174,770 participants 279 cases were diagnosed during the mean follow-up of 17 years. Consistently in each cohort, HRs above one was observed for all exposures with exception of PM2.5 absorbance and traffic density. In the meta-analysis all exposures were associated with elevated HRs. The summary HR associated with a 10 g/m3 increase in NO2 was 1.10 (95% confidence interval (CI): 0.93, 1.30) and 1.44 (95% CI: 0.83, 2.52) for PM10, which was not available in Italy. Strengths of our study relate to the long prospective follow-up of a large study population from a geographic area with different air quality and the standardized, extensive exposure assessment, which enable us to assess fine-scale, address-specific, spatial variation in concentrations of a more comprehensive number of air pollutants than previous studies. Limitations include lack of information about lifetime exposure, time-activity patterns or personal measures of exposure. Conclusion: There are suggestive evidence that exposure to air pollution may increase the risk of liver cancer in this European study.