The Environmental Protection Agency has predicted that the scheduled introduction of cleaner ultra-low sulfur diesel fuel this year may spur growth in the number of state and locally sponsored engine retrofit programs to reduce pollution, according to a Light & Medium Truck report. Emissions of particulate matter can be removed from the engine exhaust of older vehicles by retrofitting the vehicles with particulate filters. But installing retrofit technology has been difficult in the past because the level of sulfur in current diesel fuel clogs the filters, which has caused there to be few retrofit programs to this point. Because new truck engines will need ULSD to meet tougher emission regulations in 2007, the EPA has mandated that 80 percent of highway diesel fuel sold after Oct. 15 must meet the new standard of 15 parts per million of sulfur. Current diesel fuel has 500 parts per million. Since older trucks are substantial polluters, diesel retrofits are among the highest priority for the EPA, however, the agency does not have the authority to require retrofits. According to the Light&Medium Truck report, funds for state-sponsored retrofit programs could possibly come from The Congestion Mitigation and Air Quality Improvement Program, which received $8.6 billion in funding, and was recently made available to the private sector by the President.