Associations of air pollution and greenness with all-cause mortality in Greece: an ecological study

Abstract

Background/Aim: Epidemiological studies have documented the health effects of long-term exposure to fine particulate matter (PM2.5), while fewer studies have investigated the effects of exposure to nitrogen dioxide (NO2), black carbon (BC) and even less to ozone (O3). There is limited evidence for the synergistic effects of exposure to pollutants and proximity to green spaces. We investigated the association of long-term exposure to air pollution and greenness with all-cause mortality in Greece using a geographical ecological study. Methods: Mortality and socioeconomic data were obtained from 1035 municipal units from the 2011 census data. Annual average PM2.5, NO2, BC and O3 concentrations for 2010 were derived from 100x100m surfaces predicted by hybrid LUR models developed within the ELAPSE project. The normalized difference vegetation index was used for greenness. We applied generalized additive models on standardized total mortality rates (SMRs) adjusted for socioeconomic indicators and lung cancer rates and accounting for spatial autocorrelation. The analysis was conducted for the whole country and by urban and rural areas. We assessed interactions between pollutants and green space and two-exposure models. Results: PM2.5, NO2 and BC were significantly associated with mortality: an interquartile range (IQR) increase was associated with a Relative Risk (RR)of 1.09, (95% confidence interval (CI): 1.08-1.11), 1.03 (95% CI: 1.03-1.04) and 1.02(95% CI: 1.02-1.03), respectively. The associations were stronger in urban areas. Greenness was associated with lower mortality (RR: 0.95, 95% CI: 0.94 - 0.96 per IQR). An inverse association with O3 was found. We did not find any statistically significant interaction between pollution and green spaces, while estimates were mostly robust to co-exposure adjustment. Conclusions: Our findings support independent associations of air pollution exposure and green spaces with total mortality, both in the urban and rural areas in Greece that are of importance for public health policy and urban development.