Health effects resulting from nitrogen dioxide exposure in an indoor ice arena.

We investigated an outbreak of acute respiratory illness among adolescent ice-hockey players in an indoor ice arena in Stockholm that had a propane-powered ice-resurfacing machine. We administered questionnaires to all players, as well as to a reference group that had played ice hockey in indoor arenas with electric ice-resurfacing machines. In the exposed group, 55 subjects (55.6%) experienced acute respiratory symptoms, compared with 4 (7.1%) in the reference group (relative risk = 7.8; 95% confidence interval = 3.0, 20.3). The risk for pulmonary symptoms increased as time spent on the ice increased. Levels of nitrogen dioxide up to 2358 microg/m3 (1250 ppb) were detected during simulated conditions of the incident. The most likely cause of the outbreak was the high level of nitrogen dioxide that resulted from poor ventilation and a malfunctioning ice-resurfacing machine. Propane-fueled ice-resurfacing machines should not be used in indoor ice arenas.