For the first time, fine particles emitted by coal-fired power plants, factories, and diesel trucks have been linked to an increased risk of death from lung cancer. According to a study published in today’s issue of the Journal of the American Medical Association, people living in heavily polluted U.S. metropolitan areas have a 12 percent higher risk of dying from the disease than people in the least-polluted urban areas. Living in the most polluted places — which include New York, Chicago, Los Angeles, and Washington, D.C. — is comparable to living with a smoker, the report said. The study, which tracked the health of half a million people over 16 years, comes at a time when the Bush administration is moving to relax air-pollution controls on power plants and oil refineries. Environmental groups hope the findings will support their call for strict regulations and tough enforcement.