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 relationship between ambient ozone concentrations and peak expiratory flow rate. METHODS Enrolled children recorded peak expiratory flow rates (PEFR) twice daily. We obtained air pollution, meteorological and pollen data. In all, 125 children remained in the final analysis. RESULTS We found a significant negative association between daily mean deviation in PEFR and same-day mean daytime ozone concentration (beta-coefficient = 0.88; P = 0.04) after adjusting for co-pollutants, time trend, meteorological variables, pollen count and ALTERNARIA: count. The association was stronger in a subgroup of children with bronchial hyperreactivity and a doctor diagnosis of asthma (beta-coefficient = -2.61; P = 0.001). There was no significant association between PEFR and same-day daily daytime maximum ozone concentration. We also demonstrated a dose-response relationship with mean 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 children with bronchial hyperreactivity and a doctor diagnosis of asthma.