EPA issued a final rule last week that will force petroleum refiners to slash the amount of sulfur in gasoline by two-thirds. The move is part of an effort by the Obama Administration to reduce air pollution from cars and light trucks and reduce resulting respiratory problems. The rules require refineries to cut sulfur levels in gasoline by more than 60%—from 30 ppm to 10 ppm—by Jan. 1, 2017. Less sulfur in gasoline makes it easier for a car’s pollution controls to effectively filter out harmful emissions, resulting in cleaner air, EPA says. But refiners warn of possible supply problems. EPA has set “an unrealistic compliance date, which does not provide refiners adequate time to complete the required projects necessary to meet the new standard in a manner that avoids the potential for supply disruptions,” says Charles T. Drevna, president of American Fuel & Petrochemical Manufacturers, an industry trade group.