Earlier studies of children with asthma living in highly polluted regions, such as Mexico City and Los Angeles, all concluded that exposure to ozone and fine particles in excess of 120 parts per billion (ppb) and 65 micrograms per cubic meter ( g/m3), respectively, greatly increased the risk for respiratory symptoms. "We wanted to design a study that examined the effects of air pollution on a particularly vulnerable population - children with active asthma - in regions where pollution levels were somewhat lower than those in major metropolitan areas," said Leaderer.
Study participants included 271 asthmatic children living in Connecticut and the Springfield area of Massachusetts during the spring and summer of 2001. The investigators conducted monthly interviews with the mothers to obtain information on each child's daily wheezing, coughing, shortness of breath, chest tightness, and asthma medication use. Daily measurements of ground-level ozone and fine particulate matter were provided by the Departments of Environmental Protection of Connecticut and Massachusetts.
Although mean 1-hr average ozone concentrations measured only 59 ppb, variations in daily levels had a profound effect on the respiratory symptoms of those who used maintenance medication. A 50 ppb increase in 1-hr ozone was associated with a 35 percent increase in wheezing, and a 47 percent increase in chest tightness. The highest ozone levels were associated with increased shortness of breath and rescue medication use.
However, the investigators did not find a significant relationship between the children's exposure to fine particulate matter and daily respiratory symptoms or rescue medication use. Furthermore, no exposure-dependent outcomes were observed for either pollutant category among children who did not use maintenance medication.
"Our results suggest that ground-level ozone is
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Contact: John Peterson
peterso4@niehs.nih.gov
919-541-7860
NIH/National Institute of Environmental Health Sciences
8-Oct-2003