http://www.environmentalhealthnews.org/ehs/news/cleaner-trucks-and-buses
"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."
