"For decades, diesel trucks and buses have spewed large amounts of soot, smog-causing gases and carcinogens into the air. But new diesel engines are more than 90 percent cleaner than a few years ago, far exceeding the emission reductions required by the U.S. Environmental Protection Agency, according to a new independent study released Thursday. Data show new diesel technologies are working even better than expected."
"New Diesels Cut Soot, Smog Over 90%
Source: Env. Health News, 06/19/2009