The air that killed Mark Tostado on Labor Day weekend was calm and hot, the product of the sunny days that draw boaters year-round to Lake Havasu, on the California-Arizona line.

Tostado, 31, a Huntington Beach personal fitness trainer and military veteran, had waded into the lake's shallow Bridgewater Channel last year to say goodbye to a woman standing behind two idling boats. She playfully stole his hat and turned away. When she looked back less than a minute later, Tostado was gone. His body was found the next day.

An autopsy revealed that Tostado's blood was 40.7% saturated with carbon monoxide, a colorless and odorless gas released as engines burn gasoline. Tostado presumably breathed a pocket of exhaust from nearby boats, passed out and drowned.

A spate of such deaths, more than 100 nationwide since 1990, prompted the California Assembly to recently pass a bill that would force boat sellers to put carbon monoxide warning labels on vessels and outlaw boaters from standing or hanging onto swim platforms attached to the stern while an engine is running. The state Senate passed the legislation Monday.

But the families of carbon monoxide victims, legislators and physicians want boat makers and the Coast Guard, which regulates boat and marine engine design, to do more. They say improved marine engines and an aggressive public-awareness campaign about carbon monoxide dangers will help save lives.

In addition to the 111 confirmed deaths from carbon monoxide, independent and government scientists say that boat exhaust may be a factor in 40% of all drownings near boats, as many as 200 per year. The data are uncertain because many drowning victims never get tested for carbon monoxide poisoning.

"We solved this problem with cars," said Dr. Robert Baron, medical director of the Glen Canyon National Recreation Area in Arizona. "If five or 10 years ago boat manufacturers had put efforts into research, these people would still be alive."

Boat and engine manufacturers say that it's time-consuming and costly to develop new engines, and that boaters behave irresponsibly.

They point to "teak surfing," in which swimmers hang off the swim platform. In May 2003, teak surfer Anthony Farr, 11, inhaled carbon monoxide from a boat's exhaust pipes under the platform, passed out and drowned in Folsom Lake near Sacramento.

"The issue is the stupidity of people who let their kids hang around the business end of a boat," said Larry Meddock, director of the Water Sports Industry Assn. "If this was a crisis, the Coast Guard would be responding differently. They haven't issued any regulations on this issue."

Platform dangers

Researchers from the National Institute for Occupational Safety and Health say carbon monoxide poisoning fatalities began increasing in the 1970s when boats were equipped with swim platforms. Scientists estimate that three inhalations of carbon monoxide-rich air can cause death.

"When I was growing up, there were no swim platforms, just ladders on the sides of boats," said Tom McAlpine, an Alabama lawyer who represented the estate of a child who died of carbon monoxide poisoning after hanging onto the swim platform of an idling boat.

As part of a settlement, manufacturer Correct Craft began adding carbon monoxide warnings to its boats in the late '90s. The 2-by-4-inch sticker reads, in part, "Stay off and keep away from boarding platform while engine is running."

Meanwhile, the company and another major boat maker, MasterCraft, sell showering attachments that many users operate while standing on the swim platform. According to boat dealers, the engine must be running to provide a steady stream of hot water for the shower.

"One of their own designs forces people to stand in an exposure area. It doesn't make any sense," said Jane McCammon, a researcher for the National Institute for Occupational Safety and Health.

Correct Craft executives and the company's chief engineer, Bill Snook, declined to answer questions regarding the shower units. A MasterCraft representative said its owners' manuals and decals warn against standing on the swim platform while the engine is running.

Weak warnings?

Boat industry critics, including physician Baron, attorney McAlpine and researchers from the national Centers for Disease Control and Prevention, which, in a 2000 report, recommended removal of swim platforms, say the manufacturers' current sticker warnings are insufficient.

Studies by the Coast Guard and other government agencies show that carbon monoxide poisoning can occur inside boats, particularly in back seats.

"CO levels in the stern [back] seat of a ski boat are high enough to be cause for concern," one study reads. "CO levels at 20 feet behind the towed boat are high enough to affect towed tubers who tend to be young children."

In a 1997 incident, a 13-year-old girl lay on the back seat of an open-air powerboat as it headed to an Arizona lakeshore. Fifteen minutes later, when the boat docked, she was dead of carbon monoxide poisoning, according to the examining physician.

The American Boat and Yacht Council recommends that stickers on boats include warnings to not "occupy aft lounging areas when engine[s] or generator[s] is running." Stickers by MasterCraft and Correct Craft contain no such warnings about back-seat risks.

"The boat companies encourage people to sit back there by putting in seats and drink holders," said Teresa Stark, chief of staff to California Assemblyman Paul Koretz (D-West Hollywood), who introduced the bill that would require boats sold in California to carry large warning stickers. The measure would also prohibit boaters from occupying, hanging onto or bodysurfing behind swim platforms while a boat was operating. Gov. Arnold Schwarzenegger has not stated his position on the bill, but Stark expects him to sign it into law when it reaches his desk.

Boat manufacturers maintain that operator error, not boat design, results in carbon monoxide poisoning.

"There is virtually no risk of carbon monoxide poisoning" when boaters comply with state and Coast Guard regulations, Snook, Correct Craft's chief engineer, said in an e-mail.

"It's not my fault you've got parents who stick their kid behind an exhaust pipe," said Rick Lee, president of Fineline Industries, a powerboat manufacturer. "Why weren't these kids wearing life jackets? For over 80 years, society has been smart enough to not breathe in stinky exhaust."

But Glenn Palmer, a 20-year Phoenix paramedic trained in carbon monoxide detection, says he had no clue when refueling his boat in November that he was inhaling the odorless gas. The refueling mechanism required a running engine.

"There was no smell of exhaust or fumes, no lightheadedness, nothing," Palmer said. "I was standing there talking to my wife for about five minutes, when she said my eyes rolled up in mid-sentence and bam, I was out. It hit me so fast, if I had fallen in the water, I would have had no chance."

New controls

In the 1960s and 1970s, Congress addressed concerns over carbon monoxide emissions from automobiles by passing laws that required car manufacturers, but not boat makers, to decrease emissions.

Relatives of carbon monoxide victims say manufacturers have had decades to develop cleaner engines. Use of catalytic converters — a honeycomb filter that transforms carbon monoxide into safer gases — would essentially eliminate the emissions, they say. Boat exhaust contains 188 times more carbon monoxide than the average emission from an automobile.

But marine engine experts say the automotive solution won't work in water.

"Catalysts and water don't mix," said Dick Rowe, founder and chief executive of Indmar Products, a major marine engine manufacturer. "When you put an engine in the water, everything changes."

By 2008, however, the California Air Resources Board will effectively require new boat engines to incorporate catalytic converters. To establish the standard, it hired the Southwest Research Institute in San Antonio to equip four marine engines with catalytic converters. The project took four years and cost $1 million, according to chief engineer James Carroll, and the engines have successfully performed in freshwater lakes for more than 400 hours.

Regulators, including Andrew Spencer, an air pollution specialist at the Air Resources Board, say manufacturers could have produced safer engines more than a decade ago if they had made them a priority.

Manufacturers say they expect to surmount the technological challenges before 2008, but until then, consumers will dictate their agenda.

"Why haven't we solved carbon monoxide?" asked Rowe of Indmar. "Because there are other research priorities that are rewarded more by consumers. We're not sure we know how to market a catalytic converter-equipped boat. We are a small company. We can't afford to spend money on research consumers won't appreciate."

Critics also blame the Coast Guard for insufficiently policing the industry. The guard has no regulations related to carbon monoxide.

"How can the Coast Guard know this is happening and not require warnings?" asked Mike Farr, father of the boy who died while teak surfing on Folsom Lake near Sacramento. "How come there are no regulations from the Coast Guard about boat design to keep people away from the backs of boats?"

The Coast Guard's specialist on carbon monoxide emissions defends the agency's approach, noting that it sponsors media campaigns and workshops about the dangers of the gas.

"We have raised the issue of requiring warning labels at our workshops, but the manufacturers have blocked that proposal," said Richard Blackman, an engineer in the Coast Guard's Office of Boating Safety. "I'm not sure it's worth the investment."

Blackman said the Coast Guard is reluctant to issue regulations that will meet industry resistance. "The Coast Guard says if industry can regulate themselves, then it's in the best interest of everyone for companies to choose what should be done," he said.

Meanwhile, many boaters blame adults and fate for carbon monoxide deaths. "I would never let a kid hang off the back of a boat without a life jacket," Charlie Hardke, 32, said as he drove his powerboat around Folsom Lake. "But if there are toxic levels of carbon monoxide, I'd like to know."

One of Hardke's passengers, Robyn Westlake, a physician specializing in internal medicine, floated in the water near the back of the boat.

"I don't think it is any worse than the freeway, is it?" she asked.

On a day set aside for water play, victims often do not realize air quality is hazardous until it's too late.

Charles Duhigg is a Times staff writer. He can be reached at