Last weekend, 22-year-old Lucas Allyn died after boating at Bear Lake in Utah when he was overcome by carbon monoxide. According to the Deseret News, Allyn spent a good part of the day at the rear of a boat near its exhaust hoisting skiers and swimmers out of the water.
"It happened in the open air. You would think it unbelievable until you think about how the gases recirculate near the back of the boat," Dr. Robert Baron, a medical adviser for Glen Canyon National Recreation Area, told the newspaper.
On Sunday, 12 people were treated in southern Nevada after being sickened while house boating on Lake Mead. Five were flown to a hospital in Las Vegas, four were taken by ambulance and three others were treated at the scene. All have since recovered.
"They were running their generator to keep the air conditioning going," said Christie Vanover, spokeswoman for the Lake Mead National Recreation Area. She said another boat parked next to it, causing the exhaust to circulate back into the house boat.
Lyngar said carbon monoxide poisoning while boating "is far more common than we thought."
He pointed to the ban on "teak surfing," where people hold onto a swim platform at the back of a boat and are pulled through the water. Platforms are near exhaust systems.
"People used to do that for fun," he said. "There were several fatalities nationwide." It is now illegal in many states.
Lyngar recalled another incident several years ago on Lake Powell, a reservoir on the Colorado River along the Utah-Arizona line. A girl died after washing her hair using the exhaust port from a generator.
"That exhaust is filled with carbon monoxide, but that spout also has warm water," Lyngar said.
Lyngar said a regional group that has studied deaths on the Colorado River concluded that carbon monoxide poisoning "was more prevalent than we thought."
"Going over the record of old accidents, we think a lot more of these are carbon monoxide-related," he said.
"I would say 10, 20 years ago we did not look at this as seriously as we do now," he said. "Over the last decade or two, we've recognized how serious it can be."
Baron, who has reviewed death and illness reports on Lake Powell for more than 25 years, agreed.
He and others have collected data showing more than 800 incidents of death or illness on U.S. waterways attributed to carbon monoxide since the mid-1990s.
"There is absolutely many more than that number," he told The Deseret News. "It's still an under-recognized event."
Lyngar said it's a good idea for boaters to have carbon monoxide detectors on board and pay attention to them. Also, people should not linger in the back of a boat near exhaust.
"Be careful at low speeds," he said, adding invisible gas clouds can form quickly when boats are idling or moving slowly.
Safety tips on avoiding exhaust problems are covered in the agency's safe boating programs and pamphlets.
"We don't want to make people afraid," Lyngar said. "We just want to make people aware."