Carbon-Monoxide Poisoning Resulting from Exposure to Ski-Boat Exhaust --- Georgia, June 2002

Carbon monoxide (CO) is an odorless, colorless gas produced from the incomplete combustion of carbon-based fuels such as gasoline or wood. In the United States, CO poisoning causes approximately 500 unintentional deaths each year (1). Although CO poisonings often have been reported to occur in enclosed and semi-enclosed environments (2), they can also occur in open-air environments (3,4). This report describes two related cases of CO poisoning that occurred in children who were participating in recreational activities on a ski boat. Recreational boaters should be aware of the dangers of open-air CO poisoning, and engineering solutions are needed to reduce the amount of CO in boat exhaust.

On June 1, 2002, a family of two adults and three children (two boys aged 4 and 12 years and a girl aged 2 years) and three friends went to a lake in Georgia to water ski. The ski boat was placed in an idling position while one parent put on a ski vest. During this time, the girl climbed over the back of the boat onto the swim platform (a wooden platform attached to the stern a few inches above the surface of the water) and lay in a prone position to push back and kick the water. In <1 minute, she became unconscious and unresponsive.

The girl's father, a family physician, observed that her pupils were constricted and her jaw was firmly clenched. She had a pulse but no chest movement. He performed rescue breathing; after 15--20 assisted ventilations, the child resumed unassisted breathing. Local emergency medical services (EMS) personnel were notified. Approximately 35 minutes later, EMS personnel arrived and started the child on 100% oxygen through a nonrebreather mask and transported the child to the local hospital. Nearly 3 hours after exposure, the child's carboxyhemoglobin (COHb) level was 14.3% (normal: <5.0%). Back calculations of COHb levels estimated that her COHb level was 50%--57% immediately after exposure on the swim platform.

During the initial resuscitation of the girl, her youngest brother was removed from the swim platform and watched by friends during his sister's transport to the hospital. Several hours after being removed from the water, he complained of severe headache, vomited, and fell asleep. He was transported to the hospital for evaluation. Approximately 4 hours after exposure, his COHb level was 10.1%. Back calculations of COHb levels estimated that the boy's COHb level was 18%--21% immediately after exposure. Both children were transported to another hospital, admitted to the pediatric intensive care unit, and treated with 100% oxygen. They were discharged the following day.

Reported by: RJW Richards, Jr., MD, NN Richards, MPH, Evans; KE Powell, MD, Div of Public Health, Georgia Dept of Human Resources. R Baron, MD, Lake Powell Emergency Medical Svcs, Lake Powell, Arizona. J McCammon, Denver Field Office, National Institute for Occupational Safety and Health; SC Redd, MD, JA Mott, PhD, Div of Environmental Hazards and Health Effects, National Center for Environmental Health; AL Stock, PhD, EIS Officer, CDC.

Editorial Note:

Open-air CO-related morbidity and mortality has been reported to occur with exposure to exhaust from gasoline-powered electricity generators on houseboats (3). However, this report describes CO poisoning resulting from direct exposure to CO in the exhaust of a ski boat. Ambient CO concentrations have been measured as high as 27,000 parts per million (ppm) in the stern of boats involved in CO-poisoning fatalities (5). In comparison, the World Health Organization has set a ceiling limit on a person's exposure to CO at 87 ppm during a 15-minute interval (6). Although the introduction of the catalytic converter to automobiles reduced CO concentrations in automobile exhaust by >90% (7), emissions-control devices have not been introduced to the propulsion engines of recreational boats.

Since 1990, a case listing compiled by an interagency working group consisting of the U.S. Department of the Interior, National Park Service, CDC's National Institute for Occupational Safety and Health, and the U.S. Coast Guard has documented 17 fatalities and 37 nonfatal poisonings on U.S. waters resulting from exposure to the propulsion engine exhaust of ski boats and cabin cruisers (5). Although many poisoning victims were exposed while on or near the swim platform, several fatalities also occurred among persons seated in the stern of the boat. This case listing was compiled from media reports and probably underrepresents the national burden of these incidents. In addition, because COHb measurements are obtained infrequently from victims of unwitnessed drownings (8), the actual number of drownings resulting from CO poisoning remains unknown.

On inhalation, CO binds to hemoglobin with a binding affinity 200--270 times greater than that of oxygen. At COHb concentrations of 10%--20%, symptoms of CO poisoning might resemble those of motion sickness or heat exhaustion and can include headache, nausea, dizziness, and vomiting. Although seizures, coma, and death might occur at COHb concentrations >30% (9), COHb concentrations of >50% have been found after minutes of outdoor exposure to boat exhaust (5). Health-care providers should consider immediate COHb measurements any time a drowning occurs near a boat or boat occupants present with signs and symptoms consistent with CO poisoning.

Recreational boaters should be aware that boat exhaust can flow back into the rear of the boat and that CO in the exhaust is undetectable because it is odorless and colorless. In addition, they should avoid swimming or body surfing near the exhaust system while the boat or generator is running. Studies of CO concentrations in the air around boats and of COHb levels in recreational boaters are needed to determine the extent of boat-related CO poisonings, and public health campaigns to warn of the danger of boat-related CO poisonings require further evaluation. The use of emissions-control devices in recreational boats can reduce CO emissions and the risk for CO poisoning.

References

1. CDC. Carbon monoxide poisoning: what's the problem? Available at http://www.cdc.gov/nceh/airpollution/carbonmonoxide/cofaq.htm.
2. CDC. Unintentional carbon monoxide poisonings in residential settings---Connecticut, November 1993--March 1994. MMWR 1995;44:765--7.
3. CDC. Houseboat-associated carbon monoxide poisonings on Lake Powell---Arizona and Utah, 2000. MMWR 2001;49:1105--7.
4. CDC. Outdoor carbon monoxide poisoning attributed to tractor exhaust---Kentucky, 1997. MMWR 1997;46:1224--7.
5. U.S. Department of the Interior. Boat-related carbon monoxide poisonings on U.S. waters. Available at http://safetynet.smis.doi.gov/cohouseboats.htm.
6. World Health Organization. Environmental Health Criteria 213: Carbon Monoxide. 2nd ed. Geneva, Switzerland: World Health Organization, 1999.
7. Shelef M. Unanticipated benefits of automotive emission control: reduction in fatalities by motor vehicle exhaust gas. Sci Total Environ 1994;146:93--101.
8. CDC. Review of national park service emergency medical records to identify carbon monoxide poisonings at Lake Mead National Recreation Area. Washington, DC: U.S. Department of Health and Human Services, CDC, National Institute for Occupational Safety and Health, 2000; NIOSH report no. HETA 2000-0400.
9. Viccellio P, Bania T, eds. Emergency toxicology. 2nd ed. Philadelphia, Pennsylvania: Lippincott-Raven, 1998.

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