Acute respiratory effects of summer smog in primary school children.

In 535 primary school children we studied the effects of exposure to summer smog on respiratory health. Baseline measurements were performed during low air pollution levels (max. 24-h concentrations of SO2, O3 and NO2 were 55, 49 and 58 micrograms/m3, respectively) consisting of lung function measurements using spirometry and the forced oscillation technique (FOT) and the prevalence of respiratory symptoms, determined by a written questionnaire. During a summer smog episode, 212 randomly chosen children were re-examined, characterised by 8-h ozone levels > 120 micrograms/m3 (max. 163 micrograms/m3) and 1-h ozone levels > 160 micrograms/m3 (max. 215 micrograms/m3). Overall, small decrements were observed in the forced expiratory volume in 1 s (FEV1), (P < 0.05) and the forced expiratory volume between 25 and 75% of the vital capacity (FEF25-75%) (P < 0.01). On the contrary, there was a statistically significant decrease in resistance parameters. No increases were observed in the prevalence of acute respiratory symptoms. In conclusion, in this study we found small inconsistent changes in lung function and no increase of respiratory symptoms after short-time exposure to moderately high ozone levels.