Such proposals are motivated by both economic and environmental concerns.
To be sure, even the Bush administration, long the target of criticism from environmental groups, is proposing massive reductions in air pollution caused by certain types of diesel-powered vehicles.
Machinery slated for reductions would include marine vessels, mining equipment and farm machinery.
The proposal would force manufacturers of a wide range of off-road diesel equipment to install modern emission controls on new vehicles beginning in 2008 and the new guidelines would mandate the use of cleaner-burning diesel fuel containing 99-percent less sulfur by 2010.
While some critics worry the proposed regulations will force farmers to replace older equipment with newer models, supporters of renewable fuels are optimistic the new rules will increase market share for biodiesel and ethanol.
The new guidelines are part of a broader plan by EPA to curtail emissions from all diesel-powered vehicles. The off-road regulations follow a 2001 rule ordering pollution cuts from heavy-duty diesel engines and diesel fuel used in highway trucks and buses.
According to EPA, the reduction in off-road diesel emissions will prevent nearly 10,000 premature deaths, 16,000 heart attacks and 260 thousand respiratory ailments in children by the year 2030. The proposed rule would take effect in 2004 after EPA evaluates public comments.