Association of low-level ozone and fine particles with respiratory symptoms in children with asthma

JAMA. 2003 Oct 8;290(14):1859-67. doi: 10.1001/jama.290.14.1859.


Context: Exposure to ozone and particulate matter of 2.5 microm or less (PM2.5) in air at levels above current US Environmental Protection Agency (EPA) standards is a risk factor for respiratory symptoms in children with asthma.

Objective: To examine simultaneous effects of ozone and PM2.5 at levels below EPA standards on daily respiratory symptoms and rescue medication use among children with asthma.

Design, setting, and participants: Daily respiratory symptoms and medication use were examined prospectively for 271 children younger than 12 years with physician-diagnosed, active asthma residing in southern New England. Exposure to ambient concentrations of ozone and PM2.5 from April 1 through September 30, 2001, was assessed using ozone (peak 1-hour and 8-hour) and 24-hour PM2.5. Logistic regression analyses using generalized estimating equations were performed separately for maintenance medication users (n = 130) and nonusers (n = 141). Associations between pollutants (adjusted for temperature, controlling for same- and previous-day levels) and respiratory symptoms and use of rescue medication were evaluated.

Main outcome measures: Respiratory symptoms and rescue medication use recorded on calendars by subjects' mothers.

Results: Mean (SD) levels were 59 (19) ppb (1-hour average) and 51 (16) ppb (8-hour average) for ozone and 13 (8) microg/m3 for PM2.5. In copollutant models, ozone level but not PM2.5 was significantly associated with respiratory symptoms and rescue medication use among children using maintenance medication; a 50-ppb increase in 1-hour ozone was associated with increased likelihood of wheeze (by 35%) and chest tightness (by 47%). The highest levels of ozone (1-hour or 8-hour averages) were associated with increased shortness of breath and rescue medication use. No significant, exposure-dependent associations were observed for any outcome by any pollutant among children who did not use maintenance medication.

Conclusion: Asthmatic children using maintenance medication are particularly vulnerable to ozone, controlling for exposure to fine particles, at levels below EPA standards.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Air Pollutants / analysis
  • Air Pollutants / poisoning*
  • Air Pollution / adverse effects*
  • Anti-Asthmatic Agents / therapeutic use
  • Asthma / chemically induced
  • Asthma / drug therapy
  • Asthma / physiopathology*
  • Child
  • Child, Preschool
  • Cohort Studies
  • Connecticut / epidemiology
  • Dyspnea
  • Female
  • Humans
  • Male
  • Massachusetts / epidemiology
  • Ozone / analysis
  • Ozone / poisoning*
  • Particle Size
  • Respiratory Sounds
  • Severity of Illness Index


  • Air Pollutants
  • Anti-Asthmatic Agents
  • Ozone