Slaughter JC, Lumley T, Sheppard L, Koenig JQ, Shapiro GG. Ann Allergy Asthma Immunol. 2003;91:346–353
Purpose of the Study.
To investigate the short-term effects of ambient air pollution on asthma symptoms and medication use among children with persistent asthma.
A total of 133 children (5–13 years of age) with mild/moderate asthma were studied. The mean duration of asthma was 5.3 years. The children were enrolled from 1 center participating in the Childhood Asthma Management Program study. During the run-in period of the Childhood Asthma Management Program study, before being placed on 1 of the study controller medications or placebo, the subjects had preventative therapy suspended and were monitored for 28 to 112 days while using only albuterol as needed and orally administered prednisone for treatment of severe exacerbations.
The children and their caregivers completed daily diary cards for an average of 58 days, recording medication use and asthma severity. Air pollution and temperature data were collected by the Puget Sound Clean Air Agency (Seattle, WA). Particulate matter (PM) and carbon monoxide (CO) were measured. PM is a complex aerosol of solid and liquid, organic and inorganic materials, including dust, soot, smoke, pollen, acid droplets, and secondary aerosols. PM with an aerodynamic diameter of ≤10 μm (PM10) and PM with an aerodynamic diameter of ≤2.5 μm (PM2.5) were measured. Recent research has indicated that PM2.5 may be more strongly associated with asthma than larger particles. PM2.5 and PM10 concentrations were measured nephelometrically. CO monitoring sites were located in areas of high traffic volume. CO data were averaged, to diminish the influence of random sources of air pollution on any given day.
Asthma severity and medication use were both associated with elevated PM2.5, PM10, and CO concentrations. Increasing asthma severity was most significantly seen 1 day after pollution exposure. With adjustment for confounders, 1 day after a 10 μg/m3 increase in PM2.5 levels, there was a 1.2-fold increase in the odds of having a serious asthma attack and a 1.08-fold increase in β-receptor agonist use. The association of air pollutants with medication use was weaker than that with asthma severity. Stronger associations with asthma severity and rescue inhaler use were found with CO levels than with PM levels.
Increases in PM and CO levels were associated with higher risks of increasing asthma severity and rescue medication use among children with moderate/severe asthma in the Seattle area.
The authors noted that there is no biological plausibility of a direct association between CO levels and asthma exacerbations. The primary effect of CO exposure is anoxia, which results in confusion, headache, and nausea. The authors speculated that CO levels may serve as a marker for exposure to combustion byproducts, particularly diesel and gasoline exhaust particles.