title: Development of Long-term Spatiotemporal Models for Ambient Ozone in Six Metropolitan regions of the United States: The MESA Air Study.
abstract: BACKGROUND
  Current epidemiologic studies rely on simple ozone metrics which may not appropriately capture population ozone exposure. For understanding health effects of long-term ozone exposure in population studies, it is advantageous for exposure estimation to incorporate the complex spatiotemporal pattern of ozone concentrations at fine scales.
  
  
  OBJECTIVE
  To develop a geo-statistical exposure prediction model that predicts fine scale spatiotemporal variations of ambient ozone in six United States metropolitan regions.
  
  
  METHODS
  We developed a modeling framework that estimates temporal trends from regulatory agency and cohort-specific monitoring data from MESA Air measurement campaigns and incorporates land use regression with universal kriging using predictor variables from a large geographic database. The cohort-specific data were measured at home and community locations. The framework was applied in estimating two-week average ozone concentrations from 1999 to 2013 in models of each of the six MESA Air metropolitan regions.
  
  
  RESULTS
  Ozone models perform well in both spatial and temporal dimensions at the agency monitoring sites in terms of prediction accuracy. City-specific leave-one (site)-out cross-validation R2accounting for temporal and spatial variability ranged from 0.65 to 0.88 in the six regions. For predictions at the home sites, the R2is between 0.60 and 0.91 for cross-validation that left out 10% of home sites in turn. The predicted ozone concentrations vary substantially over space and time in all the metropolitan regions.
  
  
  CONCLUSIONS
  Using the available data, our spatiotemporal models are able to accurately predict long-term ozone concentrations at fine spatial scales in multiple regions. The model predictions will allow for investigation of the long-term health effects of ambient ozone concentrations in future epidemiological studies.
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, Washington, USA.
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Keller
authors.affiliation: Department of Epidemiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Sara D
authors.initials: SD
authors.lastname: Adar
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA; Institute of Health and Environment, Seoul National University, Seoul, Korea.
authors.forename: Sun-Young
authors.initials: SY
authors.lastname: Kim
authors.affiliation: Department of Civil and Environmental Engineering, College of Engineering, University of Washington, Seattle, Washington, USA.
authors.forename: Timothy V
authors.initials: TV
authors.lastname: Larson
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Casey
authors.initials: C
authors.lastname: Olives
authors.affiliation: Department of Statistics, University of Washington, Seattle, Washington, USA.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Sampson
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA; Department of Biostatistics, University of Washington, Seattle, Washington, USA.
authors.forename: Lianne
authors.initials: L
authors.lastname: Sheppard
authors.affiliation: Department of Biostatistics, University of Washington, Seattle, Washington, USA.
authors.forename: Adam A
authors.initials: AA
authors.lastname: Szpiro
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Sverre
authors.initials: S
authors.lastname: Vedal
authors.affiliation: Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA.
authors.forename: Joel D
authors.initials: JD
authors.lastname: Kaufman
keywords: MESA Air; Ozone; geo-statistical model; multi-city; spatio-temporal