Asthma in children exposed to nitrogen dioxide in ice arenas

Very high concentrations of nitrogen dioxide (NO2) have been measured in arenas using combustion engine-powered resurfacing machines. This study was performed to compare the occurrence of asthma in children playing ice hockey in arenas using propane-powered machines and in children attending arenas using electric machines. Children regularly playing hockey in the arenas (nine propane, six electric) were sent a questionnaire, including questions on allergic disease and risk factors. Measurements of NO2 were performed with passive diffusion samplers during 3 consecutive days. The mean NO2 concentration in the propane arenas was 276 microg x m(-3) (range 28-1015 microg x m(-3)) and 11 microg x m(-3) (2-30) in the electric arenas. Questionnaires were answered by 1,536 children (78%), with an overall prevalence of asthma of 16%. The odds ratio (OR) for asthma was 0.9 (95% confidence interval (CI) 0.7-1.2) comparing propane arenas to electric. However, children in propane arenas with higher than median concentration of NO2 reported more wheezing (OR 1.4, 95% CI 1.0-1.9) and nasal symptoms (OR 1.7, 95% CI 1.3-2.3) than children in propane arenas with lower concentrations. In conclusion, children playing ice hockey in indoor arenas have a high prevalence of asthma, but it appears unlikely that increased exposure to combustion products, including nitrogen dioxide, is a major contributor to this excess risk.