Abstract
Background and aim: Vehicle exhaust is the main emission source in urban areas, mainly releasing ultrafine particles (<0.1µm, UFP) with impact in particle number concentration (N) in ambient air. Evidence of UFP health effects is inconsistent. New particles are the result of direct emissions and formation of secondary UFP from gaseous precursors. We segregated the UFP into these two classes and investigated their impact on daily respiratory mortality in Barcelona, Spain.
Methods: We collected daily mortality counts due to respiratory causes (ICD10: J00-J99), COPD (J40-J44,J47), LRTI (J09-J18,J20-J22), bronchitis (J20-J22) and pneumonia (J12-J18) and daily concentrations of UFP between 2009-2012. We segregated the UFP using a method based on the high correlation between black carbon and N (Rodriguez et al, Aerosol Sci 2007;38:1207-19). The first component accounts for aerosol constituents emitted by vehicle exhaust (N1) and the second for photochemical new particle formation enhancements (N2). We evaluated short-term effects up to one week, using a time-stratified case-crossover design.
Results: Daily mean UFP concentration (N) was 13,114/cm3, 45% being N1. We observed statistically significant associations for all respiratory causes and COPD, increasing risk of mortality by 6% and 10%, respectively, for 3,950/cm3 rise of N1 at lag 0. We observed positive, but not significant, associations between N1 and the other respiratory outcomes. We did not find any effect of N2.
Conclusion: UFP from vehicle exhaust are more harmful for respiratory health than those from photochemical nucleation. This should have an implication for EU regulation of the UFP concentrations in urban air.
- Copyright ©the authors 2016
