RT Journal Article SR Electronic T1 Urban air pollution, and asthma and COPD hospital emergency room visits JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 635 OP 641 DO 10.1136/thx.2007.091371 VO 63 IS 7 A1 J I Halonen A1 T Lanki A1 T Yli-Tuomi A1 M Kulmala A1 P Tiittanen A1 J Pekkanen YR 2008 UL http://thorax.bmj.com/content/63/7/635.abstract AB Background: There is little previous information of the effects of size fractioned particulate air pollution and source specific fine particles (PM2.5; <2.5 μm) on asthma and chronic obstructive pulmonary disease (COPD) among children, adults and the elderly.Objectives: To determine the effects of daily variation in levels of different particle size fractions and gaseous pollutants on asthma and COPD by age group.Methods: Levels of particulate air pollution, NO2 and CO were measured from 1998 to 2004 at central outdoor monitoring sites in Helsinki, Finland. Associations between daily pollution levels and hospital emergency room visits were evaluated for asthma (ICD10: J45+J46) in children <15 years old, and for asthma and COPD (ICD10: J41+J44) in adults (15–64 years) and the elderly (⩾65 years).Results: Three to 5 day lagged increases in asthma visits were found among children in association with nucleation (<0.03 μm), Aitken (0.03–0.1 μm) and accumulation (0.1–0.29 μm) mode particles, gaseous pollutants and traffic related PM2.5 (7.8% (95% CI 3.5 to 12.3) for 1.1 μg/m3 increase in traffic related PM2.5 at lag 4). Pooled asthma–COPD visits among the elderly were associated with lag 0 of PM2.5, coarse particles, gaseous pollutants and long range transported and traffic related PM2.5 (3.9% (95% CI 0.28 to 7.7) at lag 0). Only accumulation mode and coarse particles were associated with asthma and COPD among adults.Conclusions: Among children, traffic related PM2.5 had delayed effects, whereas among the elderly, several types of particles had effects that were more immediate. These findings suggest that the mechanisms of the respiratory effects of air pollution, and responsible pollutants, differ by age group.