RATIONALE: Ambient air pollution exposure has been linked to mortality from chronic cardiorespiratory diseases, while evidence on respiratory infections remains more limited.

OBJECTIVES: We examined the association between long-term exposure to air pollution and pneumonia related mortality in adults in a pool of eight European cohorts.

METHODS: Within the multicenter project 'Effects of Low-Level Air Pollution: A Study in Europe' (ELAPSE), we pooled data from eight cohorts among six European countries. Annual mean residential concentrations in 2010 for fine particulate matter (PM 2.5), nitrogen dioxide (NO 2), black carbon (BC), and ozone (O 3) were estimated using Europe-wide hybrid land use regression models. We applied stratified Cox proportional hazard models to investigate the associations between air pollution and pneumonia, influenza, and acute lower respiratory infections (ALRI) mortality.

MEASUREMENTS AND MAIN RESULTS: Of 325,367 participants, 712 died from pneumonia and influenza combined, 682 from pneumonia, and 695 from ALRI during a mean follow-up of 19.5 years. NO 2 and BC were associated with 10-12% increases in pneumonia and influenza combined mortality, but 95% confidence intervals included unity [hazard ratios: 1.12 (0.99-1.26) per 10 µg/m 3 for NO 2; 1.10 (0.97-1.24) per 0.5 10 -5m -1 for BC]. Associations with pneumonia and ALRI mortality were almost identical. We detected effect modification suggesting stronger associations with NO 2 or BC in overweight, employed, or currently smoking participants compared to normal weight, unemployed, or non-smoking participants.

CONCLUSIONS: Long-term exposure to combustion-related air pollutants NO 2 and BC may be associated with mortality from lower respiratory infections, but larger studies are needed to estimate these associations more precisely.