Washington ? Diesel exhausts from large trucks and other sources probably cause lung cancer, the Environmental Protection Agency concluded Tuesday in a report that buttresses a push to reduce truck emissions through stricter requirements for cleaner fuel.

The EPA report concludes that uncertainties remain about long-term health effects of exposure to diesel exhausts. It said, however, that studies involving tests on animals and occupational exposure suggest strong evidence of a cancer risk to humans.

“Overall, the evidence for a potential cancer hazard to humans resulting from chronic inhalation exposure to (diesel emissions) is persuasive,” said the health impact report released by the EPA.

The report mirrors conclusions made previously in documents from various world health agencies and studies in California and is particularly significant because the EPA is the federal agency that regulates diesel emissions under the Clean Air Act.

EPA Administrator Christie Whitman repeatedly has promised to go ahead with the tougher diesel rules. Last month, with White House approval, the EPA rebuffed attempts by some diesel engine manufacturers to postpone the requirements, approving new penalties against manufacturers who fail to meet an October deadline for making cleaner-burning truck engines.

The report reiterated that environmental exposure to diesel exhausts poses “a chronic respiratory hazard to humans” in the long term including increased asthma and other respiratory problems. In some urban areas diesel exhausts account for as much as a quarter of the airborne microscopic soot, the report said.

As for cancer, the report noted occupational health studies and tests on animals that showed diesel emissions to be a cancer-causing substance. While there remain uncertainties, the report said, “it is reasonable to presume that the hazard extends to environmental exposure levels” as well.