Relationship between ozone exposure and asthma control in children

Background: Air pollution adversely affects the health of population. Children are at greater risk than adults to the adverse effects of air pollution because their respiratory systems are still developing, so they may be adversely affected by lower ozone concentrations than those that would affect adults. The aim of this study was to investigate the influence of ozone on the control of allergic asthma in children. Materials and methods: In the study were included 161 asthmatic children under 15 Years, with asthma, living in the same area. Clinical course of asthma was observed during two seasons: A - summer 2006 with high and B - summer 2007 with usual ozone levels for the season and area. Asthma symptoms, reliever usage, morning peak-flow (PEF) values and asthma-related hospital admissions were observed. Local daily concentrations of ozone and meteorological data were obtained from the Environmental Agency of the Republic of Slovenia. Results: Lower morning PEF rates' higher reliever usage and more asthma-related hospital admissions (P < 0.01) were observed in period A. In both periods a significant increase of daily asthma symptoms was observed as early as ozone concentration exceeded the 8-hour target value of 120 mu g/m(3) (chi(2) = 179-17; P < 0.0001). Positive influence on hospital admissions was observed, when ozone concentration exceeded the threshold hourly value (180 mu g/m(3)), (P = 0.019) or the 8-hour target value (P = 0.024). Conclusions: We demonstrated a significant effect of ozone on asthma control even at concentrations bellow information threshold values.