Smoky diesel exhaust billowing from the tailpipes of buses, trucks and construction equipment leads to more premature deaths, heart attacks and bouts of asthma in New York than in any other state, according to a report released yesterday by the Clean Air Task Force, an environmental group. The harmful effects of diesel exhaust were most severe in New York City, despite recent efforts to reduce noxious emissions. The study estimated that there were more heart attacks per capita connected to diesel exhaust in the city than in any other metropolitan area in the country. Diesel manufacturers contend that the study...