title: Characterization of source-specific air pollution exposure for a large population-based Swiss cohort (SAPALDIA).
abstract: BACKGROUND
  Although the dispersion model approach has been used in some epidemiologic studies to examine health effects of traffic-specific air pollution, no study has evaluated the model predictions vigorously.
  
  
  METHODS
  We evaluated total and traffic-specific particulate matter < 10 and < 2.5 microm in aero-dynamic diameter (PM(10), PM(2.5)), nitrogren dioxide, and nitrogen oxide concentrations predicted by Gaussian dispersion models against fixed-site measurements at different locations, including traffic-impacted, urban-background, and alpine settings between and across cities. The model predictions were then used to estimate individual subjects' historical and cumulative exposures with a temporal trend model.
  
  
  RESULTS
  Modeled PM(10) and NO(2) predicted at least 55% and 72% of the variability of the measured PM(10) and NO(2), respectively. Traffic-specific pollution estimates correlated with the NO(x) measurements (R(2) >or=0.77) for background sites but not for traffic sites. Regional background PM(10) accounted for most PM(10) mass in all cities. Whereas traffic PM(10) accounted for < 20% of the total PM(10), it varied significantly within cities. The modeling error for PM(10) was similar within and between cities. Traffic NO(x) accounted for the majority of NO(x) mass in urban areas, whereas background NO(x) accounted for the majority of NO(x) in rural areas. The within-city NO(2) modeling error was larger than that between cities.
  
  
  CONCLUSIONS
  The dispersion model predicted well the total PM(10), NO(x), and NO(2) and traffic-specific pollution at background sites. However, the model underpredicted traffic NO(x) and NO(2) at traffic sites and needs refinement to reflect local conditions. The dispersion model predictions for PM(10) are suitable for examining individual exposures and health effects within and between cities.
authors.affiliation: Institute of Social and Preventive Medicine, University of Basel, Basel, Switzerland. sally.liu@unibas.ch
authors.forename: L-J Sally
authors.initials: LJ
authors.lastname: Liu
authors.forename: Ivan
authors.initials: I
authors.lastname: Curjuric
authors.forename: Dirk
authors.initials: D
authors.lastname: Keidel
authors.forename: Jürg
authors.initials: J
authors.lastname: Heldstab
authors.forename: Nino
authors.initials: N
authors.lastname: Künzli
authors.forename: Lucy
authors.initials: L
authors.lastname: Bayer-Oglesby
authors.forename: Ursula
authors.initials: U
authors.lastname: Ackermann-Liebrich
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000032:analysis*; D002947:Cities; D015331:Cohort Studies; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D006801:Humans; D008962:Models, Theoretical; D009585:Nitrogen Dioxide / Q000032:analysis*; D009589:Nitrogen Oxides / Q000032:analysis*; D016011:Normal Distribution; D052638:Particulate Matter; D013557:Switzerland; D014504:Urban Health; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D052638:Particulate Matter; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide