title: Creating national air pollution models for population exposure assessment in Canada.
abstract: BACKGROUND
  Population exposure assessment methods that capture local-scale pollutant variability are needed for large-scale epidemiological studies and surveillance, policy, and regulatory purposes. Currently, such exposure methods are limited.
  
  
  METHODS
  We created 2006 national pollutant models for fine particulate matter [PM with aerodynamic diameter ≤ 2.5 μm (PM2.5)], nitrogen dioxide (NO2), benzene, ethylbenzene, and 1,3-butadiene from routinely collected fixed-site monitoring data in Canada. In multiple regression models, we incorporated satellite estimates and geographic predictor variables to capture background and regional pollutant variation and used deterministic gradients to capture local-scale variation. The national NO2 and benzene models are evaluated with independent measurements from previous land use regression models that were conducted in seven Canadian cities. National models are applied to census block-face points, each of which represents the location of approximately 89 individuals, to produce estimates of population exposure.
  
  
  RESULTS
  The national NO2 model explained 73% of the variability in fixed-site monitor concentrations, PM2.5 46%, benzene 62%, ethylbenzene 67%, and 1,3-butadiene 68%. The NO2 model predicted, on average, 43% of the within-city variability in the independent NO2 data compared with 18% when using inverse distance weighting of fixed-site monitoring data. Benzene models performed poorly in predicting within-city benzene variability. Based on our national models, we estimated Canadian ambient annual average population-weighted exposures (in micrograms per cubic meter) of 8.39 for PM2.5, 23.37 for NO2, 1.04 for benzene, 0.63 for ethylbenzene, and 0.09 for 1,3-butadiene.
  
  
  CONCLUSIONS
  The national pollutant models created here improve exposure assessment compared with traditional monitor-based approaches by capturing both regional and local-scale pollution variation. Applying national models to routinely collected population location data can extend land use modeling techniques to population exposure assessment and to informing surveillance, policy, and regulation.
authors: School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada. phystad@gmail.com
authors: Perry
authors: P
authors: Hystad
authors: Eleanor
authors: E
authors: Setton
authors: Alejandro
authors: A
authors: Cervantes
authors: Karla
authors: K
authors: Poplawski
authors: Steeve
authors: S
authors: Deschenes
authors: Michael
authors: M
authors: Brauer
authors: Aaron
authors: A
authors: van Donkelaar
authors: Lok
authors: L
authors: Lamsal
authors: Randall
authors: R
authors: Martin
authors: Michael
authors: M
authors: Jerrett
authors: Paul
authors: P
authors: Demers
mesh_terms: D000397:Air Pollution / Q000032:analysis*; D001554:Benzene / Q000032:analysis; D001555:Benzene Derivatives / Q000032:analysis; D002070:Butadienes / Q000032:analysis; D002170:Canada; D004784:Environmental Monitoring / Q000379:methods*; D008962:Models, Theoretical; D009585:Nitrogen Dioxide / Q000032:analysis
chemical_list: D001555:Benzene Derivatives; D002070:Butadienes; D001554:Benzene; C031763:1,3-butadiene; C004912:ethylbenzene; D009585:Nitrogen Dioxide