‘Winter Gas’ Cuts Carbon Monoxide Emissions : Air quality: Although levels of the pollutant dropped by 33% in the state, use of the oxygen-filled gasoline is credited for only 10% of that. Winter storms did the rest.

The use of oxygen-filled “winter gasoline” in California over the past four months cut carbon monoxide levels statewide by 10%, the state Air Resources Board said Wednesday.

But the so-called oxygenated fuel, which lowers carbon monoxide emissions by making combustion more efficient, also has raised the cost of operating a vehicle--increasing the price of gasoline by up to 10 cents a gallon and lowering mileage between 1% and 5%.

The level of carbon monoxide, which poses a health threat for people with heart disease and respiratory problems, dropped 33% in the state this winter, said ARB spokesman Bill Sessa. But the unusually stormy weather is credited with about two-thirds of the air quality improvement.

“We’re probably looking at the cleanest carbon monoxide year” since monitoring began in 1976, Sessa said. “Carbon monoxide is the wintertime pollution problem. We’ve never had levels this low before. . . . It’s important that people can see that (oxygenated gas) really did something.”

A 10% reduction in any pollutant from a single strategy “is very good,” said Mary Nichols, director of the Los Angeles office of the environmental group Natural Resources Defense Council.

“This is a big-time program,” Nichols said. “There are no rules being considered by the (South Coast Air Quality Management District) at the moment that could reduce 10% of the total emissions of anything.”

Sale of the gasoline, which began in Southern California on Nov. 1, ends Sunday night. As the seasonal program winds down nationally, gasoline prices already have begun to fall slightly. Prices in the Los Angeles area, however, have yet to drop.

Although statistics are not yet available for the state, Sessa said that Lynwood, with the nation’s highest levels of carbon monoxide, violated federal standards for the pollutant on only 13 days this winter, compared to 40 last winter.

In Burbank, which averages more than 10 violations each year, none have occurred in the past four months. And the San Francisco Bay Area was free of violations for the first time since monitoring began.

Gas stations in 39 metropolitan areas throughout the country--including eight in California--were required by 1990 amendments to the federal Clean Air Act to sell the new winter gasoline. These regions have yet to meet federal health standards for carbon monoxide, 90% of which comes from cars.

The ARB has built upon the Clean Air Act by mandating the sale of oxygenated gasoline statewide. California’s law also differs from the federal legislation by requiring less of the additive--either metyl tertiary butyl ether or ethanol--because it increases other problem pollutants.

Because of the higher additive levels elsewhere, the U.S. Environmental Protection Agency figures that carbon monoxide emissions dropped 15% to 20% nationally, said Bill Glenn, spokesman for the agency’s Region 9, which includes California. The EPA has no statistics yet for actual reductions.

During the winter, carbon monoxide levels rise for two reasons. First, vehicles burn gasoline less efficiently as they warm up, and it takes them longer to warm up in colder weather. Second, the winter inversion layer is pressed at rooftop level instead of thousands of feet into the atmosphere, and carbon monoxide concentrates lower to the ground.

Winter storms, however, created enough turbulence in the atmosphere to dilute the toxic pollutant and account for a large amount of the carbon monoxide reduction, Sessa said.

Carol E. Lyons, who helped analyze a winter gas program that began in Colorado three years ago, questioned how effective the fuel is. Although all cars had to use oxygenated gasoline, she said only the dirtiest cars really showed a decrease in carbon monoxide emissions.

“You’re forcing 100% of the car population to pay for a program that benefits only a small minority,” said Lyons, senior air quality specialist at PRC Environmental Management, which analyzed the program for Colorado. Simply finding and tuning up dirty cars, she added, would give “a much greater reduction in carbon monoxide at a much lower cost.”