Diesel exhaust probably causes lung cancer, the Environmental Protection Agency said in a controversial report that’s just been released.

While the 651-page study said the long-term health effects of exposure to diesel engine exhaust were uncertain, "the evidence for a potential cancer hazard to humans resulting from chronic inhalation exposure to [diesel emissions] is persuasive."
The report, developed over the past 10 years, states that exposure to diesel exhaust poses "a chronic respiratory hazard to humans," including increased asthma and other respiratory problems. Furthermore, tests on animals showed diesel emissions likely to be a carcinogen, a cancer-causing substance, although the agency found insufficient scientific evidence to quantify a relationship between diesel exhaust exposure and lung cancer.
Environmental groups applauded the study and called on the Bush Administration to further reduce diesel exhaust emissions from vehicles. While the EPA requires a 90 percent reduction in diesel emissions from heavy trucks and buses by 2007 compared with today's levels, the agency has yet to deal with off-highway diesel exhaust sources such as farm tractors and construction equipment.
A lobby group for diesel engine manufacturers and fuel refiners criticized the study, saying it relies on data collected before the Clean Air Act -- primarily during the 1950s, 60s and 70s.
"While the report focused on the past, diesel trucks and buses built today are more than eight times cleaner than just a dozen years ago," said Allen Schaeffer, executive director of the Diesel Technology Forum. Advances in clean diesel technology are lowering emissions of diesel exhaust, as evidenced by EPA's own air quality data showing that from 1990-1998, levels of diesel particulates in the atmosphere dropped by over 37 per cent, he said.
Schaeffer pointed to a recent test by the California Air Resources Board where a diesel bus running on low sulfur fuel and equipped with the latest emissions-control technology outperformed a natural-gas-powered bus on eight of 11 emissions tests.
Two-thirds of all farm equipment runs on diesel, and diesel-powered trucks, trains, boats, and barges move 94 percent of the nation's goods -- more than 18 million tons of freight each day. "For many applications, there is no alternative to diesel. That's why manufacturers and fuel refiners are working overtime to continue reducing emissions from this vital technology," he concluded.