title: Multifactorial airborne exposures and respiratory hospital admissions--the example of Santiago de Chile.
abstract: Our results provide evidence for respiratory effects of combined exposure to airborne pollutants in Santiago de Chile. Different pollutants account for varying adverse effects. Ozone was not found to be significantly associated with respiratory morbidity.
  
  
  BACKGROUND
  High concentrations of various air pollutants have been associated with hospitalization due to development and exacerbation of respiratory diseases. The findings of different studies vary in effect strength and are sometimes inconsistent.
  
  
  OBJECTIVE
  We aimed to assess associations between airborne exposures by particulate matter as well as gaseous air pollutants and hospital admissions due to respiratory disease groups under the special orographic and meteorological conditions of Santiago de Chile.
  
  
  METHODS
  The study was performed in the metropolitan area of Santiago de Chile during 2004-2007. We applied a time-stratified case-crossover analysis taking temporal variation, meteorological conditions and autocorrelation into account. We computed associations between daily ambient concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), particulate matter (PM10 and PM2.5 - particulate matter with aerodynamic diameters less than 10 or 2.5 μm, respectively) or ozone (O3) and hospital admissions for respiratory illnesses.
  
  
  RESULTS
  We found for CO, NO2, PM10 and PM2.5 adverse relationships to respiratory admissions while effect strength and lag depended on the pollutant and on the disease group. By trend, in 1-pollutant models most adverse pollutants were CO and PM10 followed by PM2.5, while in 2-pollutant models effects of NO2 persisted in most cases whereas other effects weakened and significant effects remain for PM2.5, only. In addition the strongest effects seemed to be immediate or with a delay of up to one day, but effects were found until day 7, too. Adverse effects of ozone could not be detected.
  
  
  CONCLUSIONS
  Taking case numbers and effect strength of all cardiovascular diseases into account, mitigation measures should address all pollutants especially CO, NO2, and PM10.
authors.affiliation: Core Facility Studies, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany. Electronic address: ulrich.franck@ufz.de.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Franck
authors.affiliation: Core Facility Studies, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany. Electronic address: arne.leitte@googlemail.com.
authors.forename: Arne Marian
authors.initials: AM
authors.lastname: Leitte
authors.affiliation: Institute of Meteorology and Climate Research (IMK-IFU), Karlsruhe Institute of Technology (KIT), Garmisch-Partenkirchen, Germany. Electronic address: peter.suppan@kit.edu.
authors.forename: Peter
authors.initials: P
authors.lastname: Suppan
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D000397:Air Pollution / Q000706:statistics & numerical data*; D002248:Carbon Monoxide / Q000032:analysis; D002318:Cardiovascular Diseases / Q000453:epidemiology; D002677:Chile / Q000453:epidemiology; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D009585:Nitrogen Dioxide / Q000032:analysis; D010126:Ozone / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D012140:Respiratory Tract Diseases / Q000453:epidemiology
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone; D002248:Carbon Monoxide; D009585:Nitrogen Dioxide
keywords: Airborne pollutants; Hospital admissions; Multiple exposures; Respiratory health effects