Short-term effect of ozone in a panel study of asthmatics

Introduction: Particulate matter, exhaust and ozone concentrations in ambient air have been associated with respiratory effects, and asthmatics are especially sensitive. Aims: Our objective was to study short-term effects of particles (PM10), vehicle exhaust (NO2) and ozone in relation to lung function among adults with asthma residing in the two major Swedish cities Stockholm and Gothenburg. Methods: 27 study subjects (17 females) with asthma recruited from the GA2LEN survey (aged 25-72 years) used a daily diary over a 10 week period (winter-spring) and recorded peak expiratory flow (PEF), forced expiratory volume in the first second (FEV1). We collected urban background concentrations of PM10, NO2 and ozone in the city centre, and adjusted for participant (intercept), time trend, day of week, temperature and humidity in the regression analysis. We evaluated the effect of the same day concentrations, and lagged one and two days, respectively. Results: Negative effects on FEV1 of ozone lag 0, lag 1, lag 2 and lag 0-2 were seen in both cities, some significant. In Stockholm there was also a significant negative effect of ozone on PEF. No significant effects were seen for PM10 or NO2 in Stockholm or Gothenburg. Discussion: We found the most consistent negative effects on lung function of ozone. Fluctuations in daily mean concentrations of PM10 and NO2 may be less well represented by a central monitoring station.