Although new Environmental Protection Agency head Christine Whitman had promised to take a close look at diesel emissions rules enacted during the last weeks of the Clinton presidency, she announced yesterday that the EPA would enforce the new rules.

Under the rule, finalized in December, fuel refiners will have to take practically all sulfur out of diesel - from 500 parts per million down to 15 ppm - starting in 2006. In a concession to concerns about refiners' ability to supply the fuel, EPA is phasing in the requirement: 80% of diesel fuel will have to meet the standard by 2006; the remaining 20% has until 2010.
Engine manufacturers will have to take 90% of particulate matter out of their exhaust by 2007. They also will have to cut nitrogen oxide emissions in two stages, starting in 2007 and finishing in 2010. Manufacturers will have to install exhaust aftertreatment devices such as catalytic converters to meet the requirements.
The American Trucking Associations expressed concern about the ability of fuel refiners to get the ultra-low-sulfur fuel in place by the deadline.
"ATA believes that it is in the nation's best interest to have one national fuel standard," the organization said in a statement. "EPA has failed to address our concerns that the diesel fuel supply will be adequate and that proper distribution systems will be in place."
Whitman said she would get annual reports from an advisory panel on the progress of reformulating diesel fuel.
ATA also said that the aftertreatment technology that will be needed to meet the new regulations does not have an extensive track record, and said that cleaner diesel fuel should be required for off-road users as well as on-highway trucks.