Low-level air pollution and cause-specific mortality in Denmark: the ELAPSE project

Abstract

BackgroundThe association between air pollution and mortality requires further investigation in areas with low air pollution levels for evaluation of current air quality limits. Within the Effects of Low-Level Air Pollution: A Study in Europe (ELAPSE) study we examined associations between long-term exposure to air pollution and cause-specific mortality in a Danish national administrative cohort.MethodsWe linked 3,334,143 Danish adults aged ≥30 years in 2000 to the Danish Cause of Death Registry until 2015. Annual mean concentrations of fine particulate matter (PM2.5), nitrogen dioxide (NO2) and black carbon (BC) were centrally modelled with European-wide hybrid ELAPSE land-use regression model in 2010 at 100m2 resolution. We applied Cox proportional hazard models for natural and cause-specific mortality in association with annual mean air pollution with age as underlying time, and adjusting for sex, education, employment status, birth country, area-level income and unemployment, and area-level lung cancer and COPD mortality rates.ResultsDuring 45,932,793 person-years of follow-up, we observed 817,029 deaths from natural causes in total, of which 245,489, 89,909, and 67,389 deaths were due to cardiovascular disease (CVD), respiratory disease (RD), and cerebrovascular disease (CeVD), respectively. Mean levels of PM2.5, NO2 and BC were 12.4 µg/m3, 20.2 µg/m3 and 1,0 10-5m-1, respectively. Hazard ratios and 95% confidence intervals for associations of PM2.5, NO2 and BC with natural mortality were 1.13 (1.11-1.16) per 5 µg/m3, 1.09 (1.08-1.10) per 10 µg/m3, and 1.08 (1.07-1.10) per 0.5 10-5m-1, respectively. Corresponding estimates for CVD mortality were 1.11 (1.08-1.15), 1.07 (1.06-1.09) and 1.07 (1.05-1.08); for RD mortality were 1.13 (1.09-1.18), 1.12 (1.10-1.15) and 1.10 (1.08-1.13); and for CeVD mortality were 1.07 (1.02-1.11), 1.04 (1.02-1.07) and 1.04 (1.02-1.06). Associations persisted below PM2.5 and NO2 EU limit values for all outcomes.ConclusionsLong-term exposures to PM2.5, NO2 and BC were associated with mortality even below EU limit values.