SACRAMENTO – To compliment its recent "clean air recipe" to limit summer-time smog from gasoline-related emissions, the California Air Resources Board (ARB) has required the use of oxygen-rich additives to limit peak, winter-time levels of carbon monoxide.

The statewide use of "oxygenated" gasoline, adopted today after a Sacramento public hearing, will begin in November 1992 and is expected to cut carbon monoxide emissions from tailpipes by 1,200 tons per day, or about 10 percent.

The ARB noted that peak, winter-time level of carbon monoxide, an invisible gas that curbs the ability of blood to carry oxygen, exceed state health standards in every metropolitan region. Unlike urban smog, which peaks during the summer months and over wide areas, the highest carbon monoxide levels are measured during winter months, usually in areas of high traffic volume or heavy traffic congestion.

Under the new ARB standards, oxygen-rich additives such as ethanol or methyl-t-butyl-ether (MTBE) will make up about 6 to 11 percent respectively of each gallon of gasoline during winter months. During combustion, the oxygen is released, making the gasoline burn more completely and reducing the formation of carbon monoxide.

With the new regulations, California joins at least 30 metropolitan regions nationwide, such as Denver and Phoenix, that use or are planning to use oxygenated gasoline to curb winter carbon monoxide levels. The oxygen levels required by the ARB, however, are lower than the 10 to 15 percent used in the rest of the nation, in an effort to also prevent increases in nitrogen oxide, a pollutant that causes many more winter pollution problems for California because of its milder weather at that time of the year.

In voting for the rule, ARB Chairwoman Jananne Sharpless said, "Combined with other changes we've recently put in place, we now have set the stage for cleaner burning gasoline for every season of the year.

"This will improve public health and it reflects Governor Wilson's commitment to a strong air quality program and a diversity of clean burning fuels in California."

The move is the latest effort by the ARB to reduce pollution created by the burning of gasoline. In late November, the ARB adopted specifications for seven components of gasoline, effective in 1996, that will reduce the summer-time, smog-forming potential of the emissions by 30-40 percent.

Also, the ARB's 10-year effort to reduce lead in gasoline will end January 1, 1992, when only lead-free gasoline will be available in California. During the oil industry's peak use of lead in the late 1970s, some grades of gasoline included as much as 3.5 grams of lead, primarily as an inexpensive method of boosting octane.

 Since then, both ARB and national Environmental Protection Agency (EPA) standards have lowered allowable lead to just trace amounts of only 0.1 gram, forcing more sophisticated and improved refining methods to produce cleaner gasoline. In addition, to protect engines in older cars, primarily those built before 1971 that were designed for leaded gasoline, oil companies have substituted more environmentally acceptable additives.

Sharpless noted that the ARB's phase-out of lead in gasoline was prompted by the health threat of excessive airborne lead levels, including anemia in adults and neurological damage that leads to learning disorders in children. "Before we began the phase-out of lead in gasoline, peak lead levels in the air were often 10 times higher than our health standards allowed.

 "Fortunately, we have rarely exceeded that health standard for many years now, and that is a public health benefit that is tied directly to our phase-out of lead in gasoline."

Sharpless also noted that even though lead levels in gasoline have been gradually reduced over many years, motorists may only now be aware of it as gas stations begin a changeover to unleaded pumps to meet the January 1 deadline.

"Some oil companies have been selling only lead-free gasoline for quite some time now," she said. "And the lead-free gasoline that is required next year will provide the same performance and engine protection as older grades, but will be more environmentally acceptable."