SACRAMENTO – In a move to cut urban soot and public exposure to potentially cancer-causing airborne compounds, the nation's cleanest burning diesel fuel goes on sale in California this Friday to comply with standards set by the California Air Resources Board (ARB).

 Also, sales of oxygen-rich gasoline will begin Friday in most of the state to reduce carbon monoxide concentrations during the winter months when levels of that pollutant reach their peak.

The clean diesel standards, adopted by the ARB in 1988, will cut emissions of soot-like particles and smog-forming nitrogen oxide from buses and trucks by 25 percent. The reduced emissions will help lower urban smog (ozone) and acid rain levels, improve visibility and reduce public exposure to highly toxic compounds such as benzene and 1,3 butadiene, which are carried in diesel soot particles.

The new standards cut soot-forming sulfur levels in diesel fuel by 80 percent and reduce by up to two-thirds certain types of hydrocarbons -- known as aromatics -- that produce nitrogen oxide when they are burned. Nitrogen oxide gases create urban smog, nitric acid and visibility-reducing particles in the atmosphere.

In an effort to provide refiners with flexibility and lower cost in meeting the rule, the ARB has also allowed the three largest producers to develop their own formulas for diesel fuel that reduce the same amount of pollution. Chevron, ARCO and Texaco all have received ARB approval for their unique diesel fuel blends, which are expected to cost about six cents per gallon, half of the state's original cost estimate.

ARB Chairwoman Jananne Sharpless explained that some oil companies are still finishing refinery modifications to produce the cleaner diesel fuel, most of which will be phased into production by the end of the year.

 "This cleaner diesel fuel will greatly reduce a major public health hazard from soot and smog in the air and will reduce emissions from all trucks and buses on the road as soon as it is put into their tanks," she said. "The added six cents per gallon is a bargain compared to the cost of the health problems that these pollutants cause," she said.

She noted that the EPA also is requiring lower sulfur level diesel nationwide, beginning Friday, and that the cost difference for the California grades should be between .02 to .03 cents per gallon.

"Cleaner diesel fuel is only one-third of our anti-soot program," she added, noting that the ARB already requires "soot-free" engines in new buses and trucks and also conducts roadside testing -- similar to the Smog Check for passenger cars -- to identify high-polluting trucks and buses and require repairs that lower their emissions."

This marks the second year that the state has used oxygen-rich additives in gasoline to reduce carbon monoxide. ARB standards require that between 6 and 11 percent of each gallon, compared to 10 or 15 percent required by EPA in about 40 cities outside the state, contain additives derived from either ethanol or methanol, known ETBE and MTBE. The requirement extends to January 31 in Northern California and until the end of February in Southern California. The requirement extends to January 31 in Northern California and until the end of February in Southern California.

 The change is expected to add less than a penny to the cost of a gallon of gasoline.

The extra oxygen in the gasoline reduces the formation of carbon monoxide by increasing the gasoline's ability to burn. The ARB estimates that use of oxygenated gasoline last year cut carbon monoxide by 10 percent, or 2000 tons per day, during the time of year when, because of winter weather conditions, the health threat from that pollutant is highest. Carbon monoxide reduces the blood's ability to carry oxygen, posing special health risks for people with respiratory and heart ailments.

"The ARB has clean gasoline recipes for each season of the year," Sharpless said, "and oxygenated additives help us get through the winter, when carbon monoxide poses the greatest health risk, by complementing the state's primary method of controlling carbon monoxide -- strict tailpipe emission limits."