Public safety officials are questioning a 2004 national study that deemed “no apparent health hazard” from carbon monoxide poisoning at Lake Pleasant.

In fact, they’re conducting their own informal study to see if there are more victims of carbon monoxide poisoning than previously thought.

Officials speculate that people who appear to be struck by heat-related illness are actually exhibiting symptoms of exposure to carbon monoxide from boat exhaust.

The Arizona Department of Health Services will soon issue results from volunteers’ blood-oxygen levels and readings from carbon monoxide sensors at Lake Pleasant the weekend of July 4.

If Sgt. Wayne Lupinski’s suspicions are correct, it will trump the January 2004 report of the U.S. Department of Health and Human Services that said there was no apparent health hazard at the lake.

“My belief is that the problem may be more widespread than we’re aware of,” said Lupinski, a member of the Maricopa County Sheriff’s Lake Patrol. “Headaches, altered level of consciousness – they can also mimic exposure to the sun.”

Lupinski said it’s hard to differentiate between heat stroke and carbon monoxide poisoning, and the wrong diagnosis can hinder timely treatment.

The only way to tell is through blood analysis. The Peoria Fire Department, which responds to lake emergencies, has a machine on loan that reads blood carbon-monoxide levels from a sensor clipped onto a fingertip.

But when that machine is not available, the only option is for a hospital to test the blood.

Readily available equipment would “make sure (patients) get the appropriate care,” Lupinski said. “Do they need high-flow oxygen? Make sure they get sent to a facility with a hyperbolic chamber.

“The thing to look at is how to appropriately treat these people and not miss some of them.”

Will Humble, deputy assistant director of the Arizona Department of Health Services, said the department sometimes writes up results to help municipalities and other agencies make decisions, such as idling policies or how to manage hazards.

Lupinski said the Peoria Fire Department and the Sheriff’s Office would study the results and determine where to go from there.

Three carbon monoxide poisonings this week underscored the dangers posed by the gas, especially for people engaged in boating-related activities.

A 2-year-old boy had a seizure and fainted after he was exposed to carbon monoxide while sitting on the back of a boat Tuesday at Saguaro Lake. The boy was at the rear of the watercraft as it idled at a boat ramp. Family members were preparing to leave the lake when the boy became ill. He was taken to a hospital and is expected to recover.

On Sunday, two women were poisoned while swimming at Lake Pleasant. The women, ages 19 and 20, were swimming near a number of boats that were afloat in Humbug Cove at the far northern end of the lake, a popular partying spot, said Howard Munding, Peoria fire marshal.

The women were pulled from the water by off-duty firefighters from Daisy Mountain and Sun City who performed first aid. They were taken to a Phoenix hospital for further treatment and are expected to make a full recovery, Munding said.

The Peoria Fire Department is monitoring carbon monoxide levels at the lake and has ongoing efforts to warn boaters of the gas dangers, Munding said.

But carbon monoxide levels tend to be higher at Humbug Cove because boaters often gather there and leave engines and generators running, creating the potential for poisoning, Munding said.

“At any given time, there can be as many as hundreds of boats in there,” he said. “They go in there, tie up their boats and leave them running so they can have their blenders and radios.”

There have been other poisonings at Lake Pleasant, including two reported in 2003, according to a study issued by U.S. Coast Guard, National Park Service and other federal agencies in October 2004.