title: Exposure to traffic related air pollutants: self reported traffic intensity versus GIS modelled exposure.
abstract: BACKGROUND
  In epidemiological studies of the potential health effects of traffic related air pollution, self reported traffic intensity is a commonly used, but rarely validated, exposure variable.
  
  
  METHODS
  As part of a study on the impact of Traffic Related Air Pollution on Childhood Asthma (TRAPCA), data from 2633 and 673 infants from the Dutch and the German-Munich cohorts, respectively, were available. Parents subjectively assessed traffic intensity at the home address. Objective exposures were estimated by a combination of spatial air pollution measurements and geographic information system (GIS) based modelling using an identical method for both cohorts.
  
  
  RESULTS
  The agreement rates between self reported and GIS modelled exposure--accumulated over the three strata of self assessed traffic intensity--were 55-58% for PM(2.5), filter absorbance (PM(2.5) abs), and nitrogen dioxide in Munich and 39-40% in the Netherlands. Of the self reported low traffic exposed group, 71-73% in Munich and 45-47% in the Netherlands had low modelled exposure to these three air pollutants. Of the self assessed high exposed subgroups in Munich (15% of the total population) and the Netherlands (22% of the total population), only 22-33% and 30-32% respectively had high modelled exposure to the three air pollutants. The subjective assessments tend to overestimate the modelled estimates for PM(2.5) and NO2 in both study areas. When analysis was restricted to the portion of the Dutch cohort living in non-urban areas, the agreement rates were even lower.
  
  
  CONCLUSIONS
  Self reported and modelled assessment of exposure to air pollutants are only weakly associated.
authors.affiliation: GSF-National Research Center for Environment and Health, Institute of Epidemiology, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany. Joachim.Heinrich@gsf.de
authors.forename: J
authors.initials: J
authors.lastname: Heinrich
authors.forename: U
authors.initials: U
authors.lastname: Gehring
authors.forename: J
authors.initials: J
authors.lastname: Cyrys
authors.forename: M
authors.initials: M
authors.lastname: Brauer
authors.forename: G
authors.initials: G
authors.lastname: Hoek
authors.forename: P
authors.initials: P
authors.lastname: Fischer
authors.forename: T
authors.initials: T
authors.lastname: Bellander
authors.forename: B
authors.initials: B
authors.lastname: Brunekreef
mesh_terms: D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000032:analysis*; D015331:Cohort Studies; D003625:Data Collection / Q000379:methods / Q000592:standards; D040362:Geographic Information Systems; D005858:Germany; D006801:Humans; D008875:Middle Aged; D009426:Netherlands; D012111:Residence Characteristics; D012650:Self Disclosure; D012680:Sensitivity and Specificity; D012923:Social Class; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions