More than 8,500 premature deaths are caused every year by pollution from off-road diesel-fueled equipment not regulated by the federal government, according to a new study by state air pollution control officials. Earthmovers, bulldozers, agricultural equipment, and other such vehicles emit extraordinarily high levels of pollution that have been linked to heart illnesses, asthma attacks, and other respiratory illnesses. Last week, the Bush administration announced an unusual collaboration between the U.S. EPA and the Office of Management and Budget to regulate off-road diesel emissions. That announcement came after a federal appeals court upheld a Clinton-era rule requiring a rapid reduction in emissions from diesel-fueled large trucks and buses. Some environmentalists and state regulators fear the White House will try to create some wiggle room on the bus-and-truck rule as it goes about devising a plan for off-road vehicles.