Houseboat design linked to carbon monoxide deaths.

Federal investigators have linked several deaths to a design flaw on houseboats that can poison swimmers with carbon monoxide (CO) within minutes. An investigative report released by the Centers for Disease Control and Prevention (CDC) called houseboats with rear swim decks an "imminent danger" and urged immediate engineering changes. (Houseboat-Associated Carbon Monoxide Poisonings on Lake Powell--Arizona and Utah, 2000, 49 CDC Morbidity & Mortality Wkly. Rep. 1105(2000).)

"Houseboats with a rear swim deck and a water-level swim platform are an imminent danger to persons who enter the air space beneath the deck or spend time near the rear deck," the report said. "To prevent CO poisonings and deaths, boat manufacturers should immediately devise engineering changes to new and existing boats to prevent the collection of CO in air spaces around the stern deck."

"These deaths were senseless," said Jane McCammon, director of the National Institute of Occupational Safety and Health's Denver field office. "It is a design flaw that can be corrected.... There's no reason these deaths needed to happen."

Federal authorities began investigating the carbon monoxide poisonings last September, following the August 2000 deaths of two brothers, ages 8 and 11, on Lake Powell in the Glen Canyon National Recreation Area on the Arizona-Utah border. The investigation identified 111 cases of carbon monoxide poisoning, including 9 fatalities, linked to houseboats and other recreational boats.

Unlike automobiles, boat emissions are typically not controlled by devices such as catalytic converters, according to McCammon. Boat emissions, therefore, can quickly build to toxic levels.

"Maximum CO concentrations measured in the cavity beneath the stern deck on houseboats on Lake Powell ranged from 6,000 to 30,000 parts of CO per million parts of air (ppm) while the generators were in operation," the report said. "This oxygen-deficient, CO-rich environment in a confined space is lethal within seconds to minutes."

According to investigators, the two boys who died on Lake Powell swam into the air space beneath the swim deck of the family's houseboat "for about 30 seconds" after the family had turned on the generator to cool the interior and operate the television. In less than two minutes, one boy lost consciousness and the other started convulsing before sinking underwater.

In another case, a four-year-old girl fell unconscious into the water after standing in the back area of a boat while her mother reapplied her sunscreen.

More than half the deaths occurred after the victims entered the cavity beneath the swim platform of houseboats during or shortly after operation of the boats' generators or engines. Two people died after standing or swimming near a houseboat swim platform. The report attributes two of the nine fatalities to boats other than houseboats.

The report also warns that the boats pose a risk to repair workers. "The area beneath the swim deck should be designated as a confined space, and confined space entry procedures must be implemented before an employee enters the water to service engine components beneath the deck."

"The outdoor poisonings at Lake Powell and those reported elsewhere probably represent a larger number of deaths not recognized as CO poisoning," the report said. "Because symptoms of CO poisoning resemble those of other common conditions (e.g., alcohol consumption, motion sickness, heat stress, and nonspecific viral illness), poisonings often go unrecognized." The report also warned that emergency workers and hospital staff may not recognize cases of carbon monoxide poisoning in victims who were outdoors.

The federal government has broadened the investigation and is looking at reports of carbon monoxide poisonings outside the Lake Powell area. As the probe continues, investigators expect that even more cases could be linked to boats. "I think there probably are a significant number of poisonings we don't know about," McCammon said.