PHOENIX (AP) _ The Dixey brothers had been swimming under and around their family houseboat when 8-year-old Logan lost consciousness and 11-year-old Dillon went into convulsions. Both sank and died from carbon monoxide poisoning.

For emergency room physician Robert Baron, whose concerns about carbon monoxide poisonings around houseboats had been growing for six years, the deaths at Lake Powell proved too much to ignore.

``When the Dixeys died, I said, `I don't care if this is the only lake in the world where this is happening, we've got to stop it,'' said Baron, medical director at the Glen Canyon Recreation Area, where the boys died.

The deaths drove Baron to conduct a formal study with the National Park Service and National Institute for Occupational Safety and Health. Recently released findings suggested a growing problem, especially among houseboats using a popular hull design with a rear exhaust for gasoline-powered electric generators.

Nine people have died and 102 were sickened by carbon monoxide at Lake Powell in the past decade, according to the report. Of the deaths, seven involved houseboats with the rear exhaust design.

The potentially fatal hazard hasn't been limited to the Arizona-Utah border.

In August, 15 people were hospitalized in Lake Cumberland, Ky., for about a day after being overcome by carbon monoxide on two rented houseboats.

And, in June, four people died from exposure to the fumes from a houseboat in Missouri. The same month, carbon monoxide killed a 61-year-old woman who was cleaning algae on a houseboat in Tennessee.

Exposure to carbon monoxide can cause headaches, fatigue, shortness of breath, nausea, dizziness, Baron said. Complicating matters is that symptoms may disappear quickly and drowned swimmers are rarely tested for the poisonous gas, he said.

Separate test results released Wednesday by the national occupational safety board showed similar fume buildups at Lake Cumberland.

The findings grabbed the industry's attention, said Lyn Turpin of Sumerset Custom House Boats in Somerset, Ky.

``It's a big deal,'' Turpin said. ``We need to do everything we can within the design constraints of the boat to make it safer.''

A hazard-reducing redesign of the boats was recommended last week in a report from the Centers for Disease Control and Prevention in Atlanta.

National statistics on boating accidents and fatalities compiled by the U.S. Coast Guard give little insight into the scope of carbon monoxide poisonings. The agency is planning to survey 85 boat builders about the problem in a preliminary step toward a possible recall.

``It's an attempt at cooperation; to get them to take this seriously,'' said Randolph Doubt, a Coast Guard civilian engineer. ``That makes things a lot easier all the way around.''

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On the Net:

Centers for Disease Control and Prevention: http://www.cdc.gov/

Glen Canyon Recreation Area: http://www.nps.gov/glca/intro.htm