title: Ozone exposure and its influence on the worsening of childhood asthma.
abstract: BACKGROUND
  It is well documented that high levels of many airborne pollutants can adversely affect many systems of the human body. The aim of this study was to evaluate the specific impact of ozone (O(3)) on the worsening of childhood asthma, comparing children living at regions with high and low O(3) concentrations (reference site) without the confounding effects of other pollutants.
  
  
  METHODS
  Pollutant concentrations were monitored and data concerning asthma prevalence were collected through a questionnaire. The studied population consisted of 478 children aged 6-13 years old enrolled in four schools of the municipalities where monitoring was performed. Remote sites were identified with very low concentrations of nitrogen dioxide and volatile organic compounds and high concentrations of O(3).
  
  
  RESULTS
  The prevalence of wheeze for lifetime period and in the past year was 15.9% and 6.3%, respectively. Asthmatic children were identified when dyspnoea and wheezing were simultaneously mentioned in the absence of upper respiratory infections; according to that, the lifetime prevalence of asthmatic symptoms at the remote sites was 7.1%. The comparison with other previous studies was difficult because the criteria for analysis are not conveniently established.
  
  
  CONCLUSIONS
  The prevalence of childhood asthmatic symptoms was about 4% higher at the high O(3) site than at the low O(3) site.
authors.affiliation: LEPAE, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, R. Dr. Roberto Frias, Porto, Portugal.
authors.forename: S I V
authors.initials: SI
authors.lastname: Sousa
authors.forename: M C M
authors.initials: MC
authors.lastname: Alvim-Ferraz
authors.forename: F G
authors.initials: FG
authors.lastname: Martins
authors.forename: M C
authors.initials: MC
authors.lastname: Pereira
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000009:adverse effects / Q000032:analysis; D001249:Asthma / Q000453:epidemiology* / Q000503:physiopathology*; D002648:Child; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D009585:Nitrogen Dioxide / Q000032:analysis / Q000276:immunology; D010126:Ozone / Q000009:adverse effects* / Q000032:analysis; D011174:Portugal / Q000453:epidemiology; D015995:Prevalence; D012135:Respiratory Sounds / Q000503:physiopathology*; D012307:Risk Factors; D011795:Surveys and Questionnaires; D055549:Volatile Organic Compounds / Q000009:adverse effects / Q000032:analysis
chemical_list: D000393:Air Pollutants; D055549:Volatile Organic Compounds; D010126:Ozone; D009585:Nitrogen Dioxide