On February 23, 1992, the Wisconsin Department of Health and Social Services (DHSS) was notified that 11 students from two high schools had been treated in two emergency rooms for acute respiratory symptoms (ARS) (i.e., cough, hemoptysis, chest pain, and dyspnea); two students were hospitalized. All of the students had participated in an indoor ice hockey tournament the previous night.

On February 23, DHSS interviewed 12 players and spectators who had attended the game, some of whom reported acute respiratory manifestations that began during the game and intensified as the game continued. Others reported central nervous system manifestations, including headache, dizziness, sleepiness, nausea, and vomiting.

On February 25, DHSS administered a questionnaire to all 2215 students from the two high schools. The questionnaire asked whether they had attended the game and whether they had experienced any symptoms on the following days. Of the 1734 (78%) students who completed the questionnaire, 131 reported having attended the game.

A case of ARS was defined as cough with acute onset, hemoptysis, dyspnea, chest pain, or coughing spells within 48 hours after the start of the game. A case of central nervous system symptoms (CNSS) was defined as headaches, sleepiness, dizziness, nausea, or vomiting within 24 hours after the start of the game. Among 131 attendees, 63 (48%) reported illness, including 23 cases of ARS, six cases of CNSS, and 34 cases of both. Time at onset of ARS was 1-32 hours (mean: 4 hours) after the beginning of the game; time at onset of CNSS was 1-24 hours (mean: 2 hours) after the beginning of the game.

The risk for ARS among players (19%) was more than twice that among spectators (relative risk=2.2; 95% confidence interval=1.4-3.2), but the risk for CNSS among the two groups was similar. Risks did not vary by sex, smoking status, and presence of other respiratory conditions.

During simulation tests on February 24, levels of nitrogen dioxide of 1.5 parts per million (ppm) were detected in the air over the rink after use of an ice resurfacing machine powered by an internal combustion engine. These levels exceed the standard set by the Occupational Safety and Health Administration of 1.0 ppm for short-term (i.e., 15 minutes) exposures and are above the standard of 0.5 ppm established in Minnesota for indoor ice arenas. * The concentration of carbon monoxide was 150 ppm -- five times higher than the recommended level of 30 ppm for ice arenas in Minnesota. Higher concentrations may have been reached the night of the game because the arena and the ice resurfacing machine had been operating since early morning.

An inspection of the arena and the ice resurfacing machine showed that the engine had not been properly serviced, and the air intake of the main ventilation system in the arena was not working. Neither the locker nor referee rooms -- which were adjacent to the room where the ice resurfacing machine was stored -- were equipped with vent systems.

Reported by: W Smith, T Anderson; HA Anderson, MD, State Environmental Epidemiologist, PL Remington, MD, State Chronic Disease Epidemiologist, Div of Health, Wisconsin Dept of Health and Social Svcs. Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Although episodes of intoxication by either nitrogen dioxide or carbon monoxide in indoor arenas have been documented previously, this report describes concurrent intoxication by both toxins. Persons exposed to toxic levels of nitrogen dioxide are at increased risk for acute respiratory manifestations, such as those described in this report (1,2); CNSS suggest carbon monoxide intoxication (3,4). Both gases can be produced in indoor ice arenas by internal combustion engines used in ice resurfacing equipment. Additional sources of carbon monoxide are gas-powered radiant heaters used to heat the stands (5-8).

In general, players may be at greater risk than spectators for intoxication from nitrogen dioxide because 1) nitrogen dioxide gas is heavier than air and tends to be present at higher concentrations near ice surfaces; 2) a thermic inversion, caused by the presence of cold air over the ice, and plexiglas shields surrounding rinks may impair air circulation over rinks; and 3) the locker rooms were located next to the ice resurfacing machine storage room and had no ventilation system, which may have allowed build-up of a high concentration of gases.

Although there are more than 800 indoor ice arenas in the United States (8), only three states have established standards for ice arena air quality. To prevent the occurrences of nitrogen dioxide and carbon monoxide intoxication in indoor arenas, states that have indoor arenas should consider recommending 1) education of those who operate arenas in the prevention of these risks, 2) proper maintenance of ice resurfacing machines and heating systems, 3) adequate air circulation systems capable of exchanging the air throughout the arena, 4) continuous air monitoring to detect dangerous levels of toxins, and 5) use of battery-operated resurfacing equipment.

References

1. Douglas WW, Hepper NGG, Colby TV. Silo-filler's disease. Mayo Clin Proc 1989;64:291-304.

2. Ramirez J, Dowell AR. Silo-filler's disease: nitrogen dioxide-induced lung injury. Long-term follow-up and review of the literature. Ann Intern Med 1971;74:569-76.

3. Larcan A, Lambert H. Current epidemiological, clinicobiological, and therapeutic aspects of acute carbon monoxide poisoning. Bull Acad Natl Med (Paris) 1981;165:471-8.

4. Thompson N, Henry JA. Carbon monoxide poisoning: poisons unit experience over five years. Hum Toxicol 1983;2:335-8.

5. Anderson DE. Problems created for ice arenas by engine exhausts. Am Ind Hyg Assoc J 1971;790-801.

6. Paulozzi LJ, Satink FA. A carbon monoxide mass poisoning in an ice arena in Vermont (Letter). Am J Public Health 1991;81:222.

7. Levesque B, Dewailly E, Lavoie R, Homme DP, Allaire S. Carbon monoxide in ice skating rinks: evaluation of absorption by adult hockey players. Am J Public Health 1990;80:594-8.

8. Hedberg K, Hedberg CW, Iber C, et al. An outbreak of nitrogen dioxide-induced respiratory illness among ice hockey players. JAMA 1989; 262:3014-7.

• Minnesota standards are cited as a point of reference because Wisconsin does not regulate air quality of indoor arenas.

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