Acute effects of low levels of ambient ozone on peak expiratory flow rate in a cohort of Australian children

Background We enrolled a cohort of primary schoolchildren with a history of wheeze (n = 148) in an 11-month longitudinal study to examine the relation ship between ambient ozone concentrations and peak expiratory flow rate. Methods Enrolled children recorded peak expiratory now rates (PEFR) twice d aily. We obtained air pollution, meteorological and pollen data. In all, 12 5 children remained in the final analysis. Results We found a significant negative association between daily mean devi ation in PEFR and same-day mean daytime ozone concentration (beta-coefficie nt = 0.88; P = 0.04) after adjusting for co-pollutants, time trend, meteoro logical variables, pollen count and Alternaria count. The association was s tronger in a subgroup of children with bronchial hyperreactivity and a doct or diagnosis of asthma (beta-coefficient = -2.61; P = 0.001). There was no significant association between PEFR and same-day daily daytime maximum ozo ne concentration. We also demonstrated a dose-response relationship with me an daytime ozone concentration. Conclusions Moderate levels of ambient ozone have an adverse health effect on children with a history of wheezing, and this effect is larger in childr en with bronchial hyperreactivity and a doctor diagnosis of asthma.