U.S. Environmental Protection Agency officials said the agency would push for all 11 million diesel engines in the country to be retrofitted within 10 years in order to reduce their emissions of particulate matter. New diesel engines have recently come under new rules requiring lower emissions. Margo Oge, director of EPA’s Office of Transportation and Air Quality, announced the goal at a Diesel Technology Forum conference in the U.S., and said the agency would work with fleets to develop financial incentives to accomplish the retrofitting. Estimates of what the retrofitting would cost varied widely, from millions of dollars to billions. All diesel engines from trucks to construction equipment would be included. " We’re in the middle of seeing the most dramatic transformation of diesel engines ever," Oge said on June 3. "We have a huge job ahead of us to address the existing diesel fleets." Through retrofitting programs, "that black puff of diesel smoke we’ve become accustomed to will be a thing of the past," EPA Administrator Michael Leavitt said at the conference.