California was among the states objecting to the U.S. Environmental Protection Agency´s mandate that urban areas with smog problems sell only gasoline containing 2 percent oxygen by weight. Ethanol and methyl tertiary butyl ether are the most common gasoline additives to boost oxygen content.

While the EPA long argued the additives improved air quality, California officials argued that addition of ethanol actually worsened air pollution problems in some California areas.

In announcing the policy change Feb. 15, EPA officials acknowledged the existing mandate is "burdensome" and said the new policy would give states and refiners "greater flexibility in producing clean-burning gasoline to protect and improve air quality."

About 30 percent of the gasoline sold in the country is reformulated gasoline containing MTBE or ethanol. Parts of 14 states and the District of Columbia currently are required to sell reformulated gasoline.

California was among several states banning MTBE from gasoline because of concerns the chemical was contaminating drinking water supplies. In addition, California is located a significant distance from ethanol producing facilities in the Midwest that make the additive, a form of alcohol derived from corn, which leads to higher gasoline prices.

"This requirement was unnecessary and harmful to California´s air and water and should have been done years ago," said Sen. Barbara Boxer, D-Calif., long a critic of the fuel mandate. "The use of the oxygenate MTBE caused untold damage to our drinking water supplies and cost untold millions to our consumers. The use of the oxygenate ethanol in the summer months when clean-burning fuels were available was actually counter to the purpose of the Clean Air Act, which required the use of oxygenates in the first place."

The EPA agreed that refiners are now able to make cleaner-burning fuel without the addition of oxygenates. While eliminating a requirement for the additives, states are free to continue allowing their sales. In fact, part of the Bush administration´s energy policy calls for refiners to boost use of ethanol, which extends fuel supplies.

Dropping the reformulated gasoline mandate takes effect May 6 for most of the country. In California, it will take effect 60 days after the regulation´s publication in the Federal Register.