title: Asthma aggravation, combustion, and stagnant air.
abstract: BACKGROUND
  The relationship between current concentrations of ambient air pollution and adverse health effects is controversial. We report a meteorological index of air stagnation that is associated with daily visits to the emergency department for asthma in two urban areas.
  
  
  METHODS
  Data on daily values of a stagnation persistence index and visits to the emergency department for asthma were collected for approximately two years in Spokane, Washington, USA and for 15 months in Seattle, Washington, USA. The stagnation persistence index represents the number of hours during the 24 hour day when surface wind speeds are less than the annual hourly median value, an index readily available for most urban areas. Associations between the daily stagnation persistence index and daily emergency department visits for asthma were tested using a generalised additive Poisson regression model. A factor analysis of particulate matter (PM(2.5)) composition was performed to identify the pollutants associated with increased asthma visits.
  
  
  RESULTS
  The relative rate of the association between a visit to the emergency department for asthma and the stagnation persistence index was 1. 12 (95% CI 1.05 to 1.19) in Spokane and 1.21 (95% CI 1.09 to 1.35) in Seattle for an increase of 11 and 10 hours, respectively, of low wind speed in a given day. The stagnation persistence index was only correlated with one set of factor loadings; that cluster included the stagnation persistence index, carbon monoxide, and organic/elemental carbon.
  
  
  CONCLUSIONS
  Increased air stagnation was shown to be a surrogate for accumulation of the products of incomplete combustion, including carbon monoxide and fine particulate levels of organic and elemental carbon, and was more strongly associated with asthma aggravation than any one of the measured pollutants.
authors.affiliation: University of Washington, Seattle, WA 98195, USA.
authors.forename: G
authors.initials: G
authors.lastname: Norris
authors.forename: T
authors.initials: T
authors.lastname: Larson
authors.forename: J
authors.initials: J
authors.lastname: Koenig
authors.forename: C
authors.initials: C
authors.lastname: Claiborn
authors.forename: L
authors.initials: L
authors.lastname: Sheppard
authors.forename: D
authors.initials: D
authors.lastname: Finn
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects*; D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D002248:Carbon Monoxide / Q000009:adverse effects; D004632:Emergency Medical Services / Q000706:statistics & numerical data; D004781:Environmental Exposure / Q000009:adverse effects*; D006801:Humans; D013458:Sulfur Dioxide / Q000009:adverse effects; D019037:Urban Health Services / Q000706:statistics & numerical data; D014861:Washington / Q000453:epidemiology
chemical_list: D000393:Air Pollutants; D013458:Sulfur Dioxide; D002248:Carbon Monoxide