Mortality and Morbidity Effects of Long-Term Exposure to Low-Level PM 2.5 , BC, NO 2 , and O 3 : An Analysis of European Cohorts in the ELAPSE Project.

Long-term exposure to PM, NO, and BC was positively associated with natural-cause and cause-specific mortality in the pooled cohort and the administrative cohorts. Associations were found well below current limit values and guidelines for PM and NO. Associations tended to be supralinear, with steeper slopes at low exposures with no indication of a threshold. Two-pollutant models documented the importance of characterizing the ambient mixture with both NO and PM. We mostly found negative associations with O. In two-pollutant models with NO, the negative associations with O were attenuated to essentially unity in the mortality analysis of the administrative cohorts and the incidence analyses in the pooled cohort. In the mortality analysis of the pooled cohort, significant negative associations with O remained in two-pollutant models. Long-term exposure to PM, NO, and BC was also positively associated with morbidity outcomes in the pooled cohort. For stroke, asthma, and COPD, positive associations were found for PM, NO, and BC. For acute coronary heart disease, an increased HR was observed for NO. For lung cancer, an increased HR was found only for PM. Associations mostly showed steeper slopes at low exposures with no indication of a threshold.