title: Satellite-based estimates of ambient air pollution and global variations in childhood asthma prevalence.
abstract: BACKGROUND
  The effect of ambient air pollution on global variations and trends in asthma prevalence is unclear.
  
  
  OBJECTIVE
  Our goal was to investigate community-level associations between asthma prevalence data from the International Study of Asthma and Allergies in Childhood (ISAAC) and satellite-based estimates of particulate matter with aerodynamic diameter < 2.5 µm (PM₂.₅) and nitrogen dioxide (NO₂), and modelled estimates of ozone.
  
  
  METHODS
  We assigned satellite-based estimates of PM₂.₅ and NO₂ at a spatial resolution of 0.1° × 0.1° and modeled estimates of ozone at a resolution of 1° × 1° to 183 ISAAC centers. We used center-level prevalence of severe asthma as the outcome and multilevel models to adjust for gross national income (GNI) and center- and country-level sex, climate, and population density. We examined associations (adjusting for GNI) between air pollution and asthma prevalence over time in centers with data from ISAAC Phase One (mid-1900s) and Phase Three (2001-2003).
  
  
  RESULTS
  For the 13- to 14-year age group (128 centers in 28 countries), the estimated average within-country change in center-level asthma prevalence per 100 children per 10% increase in center-level PM₂.₅ and NO₂ was -0.043 [95% confidence interval (CI): -0.139, 0.053] and 0.017 (95% CI: -0.030, 0.064) respectively. For ozone the estimated change in prevalence per parts per billion by volume was -0.116 (95% CI: -0.234, 0.001). Equivalent results for the 6- to 7-year age group (83 centers in 20 countries), though slightly different, were not significantly positive. For the 13- to 14-year age group, change in center-level asthma prevalence over time per 100 children per 10% increase in PM₂.₅ from Phase One to Phase Three was -0.139 (95% CI: -0.347, 0.068). The corresponding association with ozone (per ppbV) was -0.171 (95% CI: -0.275, -0.067).
  
  
  CONCLUSIONS
  In contrast to reports from within-community studies of individuals exposed to traffic pollution, we did not find evidence of a positive association between ambient air pollution and asthma prevalence as measured at the community level.
authors.affiliation: MRC-HPA Centre for Environment and Health, King's College London, United Kingdom. r.anderson@sgul.ac.uk
authors.forename: H Ross
authors.initials: HR
authors.lastname: Anderson
authors.forename: Barbara K
authors.initials: BK
authors.lastname: Butland
authors.forename: Aaron
authors.initials: A
authors.lastname: van Donkelaar
authors.forename: Michael
authors.initials: M
authors.lastname: Brauer
authors.forename: David P
authors.initials: DP
authors.lastname: Strachan
authors.forename: Tadd
authors.initials: T
authors.lastname: Clayton
authors.forename: Rita
authors.initials: R
authors.lastname: van Dingenen
authors.forename: Marcus
authors.initials: M
authors.lastname: Amann
authors.forename: Bert
authors.initials: B
authors.lastname: Brunekreef
authors.forename: Aaron
authors.initials: A
authors.lastname: Cohen
authors.forename: Frank
authors.initials: F
authors.lastname: Dentener
authors.forename: Christopher
authors.initials: C
authors.lastname: Lai
authors.forename: Lok N
authors.initials: LN
authors.lastname: Lamsal
authors.forename: Randall V
authors.initials: RV
authors.lastname: Martin
authors.forename: Isaac Phase
authors.initials: IP
authors.lastname: One
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology*; D002648:Child; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity*; D010126:Ozone / Q000032:analysis / Q000633:toxicity*; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D015995:Prevalence; D058998:Remote Sensing Technology; D012959:Socioeconomic Factors; D018531:Spacecraft; D018709:Statistics, Nonparametric
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone; D009585:Nitrogen Dioxide