Acute respiratory effects of low level summer smog in primary school children

We aimed to study the possible effects of exposure to a summer smog episode on the respiratory health of 212 school children. Furthermore, the suitability of the forced oscillation technique (FOT) to demonstrate such effects was evaluated. Acute respiratory symptoms were evaluated by questionnaire and lung function was assessed by spirometry and respiratory impedance measurements. For each child, comparisons were made between measurements performed at baseline (low levels of air pollutant: 55 micrograms.m-3 for SO2 and 58 micrograms.m-3 for NO2 (maximum 24 h means); O3 levels ranged from 2-56 micrograms.m-3 (8 h mean)); and after a summer smog episode (characterized by 8 h O3 levels > 120 micrograms.m-3 (163 micrograms.m-3) and 1 h levels > 160 micrograms.m-3 (215 micrograms.m-3). No significant effects were observed on the prevalence of acute respiratory symptoms. When individual changes in lung function indices (delta LF) were regressed on changes in previous day ozone (8 h mean) and changes in mean daily temperature (delta MTemp), using multiple linear regression analysis, a significant negative association was observed with peak expiratory flow (PEF), but not with other spirometry indices. Although significant associations were observed with reactance at 8 Hz (Xrs8), resonant frequency (f0) and frequency dependence of resistance (FD), the signs of the beta s were opposite to the direction expected when O3 adversely affected the impedance outcomes. In conclusion, in this study short-term exposure to moderately high levels of ozone did not result in clear adverse effects on the respiratory health of the children.