Allowing the sale of a dirtier-burning blend, in place of a cleaner-burning one, might alleviate a supply bottleneck that is contributing to high prices. Such a substitution would give the industry time to make cleaner fuel, Mr. Millett said.
Waivers are reviewed case by case, Mr. Millett said, and are issued for 20 days, although extensions can be granted. Increased pollution is a concern, he said. "That's why we have the overall approach of minimizing duration and geographic area." Even last year, when regionwide waivers were issued after Hurricane Katrina, the agency did not see much environmental impact, he said.
But Richard Kassel, a senior lawyer with the Natural Resources Defense Council, said that allowing more pollution would not lead to relief from high gasoline prices.
"It's not clear that there's a problem with supply," he said. "There is an ozone cost to these waivers. They should be granted sparingly — when there really is a shortage, not a political problem."