In the early 1990s, NRDC attorney Rich Kassel liked to begin his mornings with a little man-versus-machine competition. From his home on the Upper West Side in New York City, he would get on his bike and head to Fifth Avenue, one of the main routes for downtown buses. Then he'd race them. Most days he'd win (according to his telling), but after a while this contest didn't seem like such a good idea. Black diesel exhaust spewed from the buses' tailpipes; the buildings trapped the fumes. "Fifth Avenue was a diesel canyon," says Kassel, now 44. "I began to think, 'Why doesn't anyone do anything about this?' Then I realized I could do something about it."

Through his research, Kassel discovered that diesel-powered vehicles were among the dirtiest wheels on the road. Truckers and bus fleets love them because they're fuel-efficient and durable. Diesel engines power about 12 percent of the miles driven by all U.S. vehicles but contribute 33 percent of the country's nitrogen oxides, a main component of smog and acid rain. Even worse, the vehicles emit huge quantities of particulate matter, known as soot, which public health experts have linked to asthma, cancer, bronchitis, and premature deaths.

So in 1993, Kassel started the Dump Dirty Diesels Campaign. His first mission was to get diesel buses off New York City's streets. The organization tried to place ads on city buses declaring: "Standing behind this bus could be more dangerous than standing in front of it." When the Metropolitan Transportation Authority, which owns the city's fleet of more than 4,500 buses, rejected the ads, NRDC fired back with a First Amendment lawsuit. NRDC won; the ads went up. "I doubt there was a reporter within 500 miles of New York City who didn't think that was a great story," Kassel says. In 2000, the authority finally agreed to implement a plan to cut diesel emissions by more than 90 percent over five years.

Kassel also took the campaign to Washington, D.C., where he advocated before Environmental Protection Agency (EPA) officials that rules governing diesel emissions across the nation needed to be strengthened. In 1998, the EPA agreed to slash diesel emissions from new trucks and buses by 40 percent beginning this year. The campaign also convinced the Clinton administration to remove almost all of the sulfur from diesel fuel and to adopt even tougher emissions standards for diesel-powered vehicles built after 2007. (Sulfur forms soot particles and clogs engine-emission controls, making diesel dirty.)

In May, Kassel and the campaign notched their biggest victory yet when the EPA extended stricter standards to bulldozers, cranes, tractors, and other "nonroad" diesel engines, which emit more soot than all of the nation's cars, trucks, and buses combined. These standards are expected to prevent some 12,000 premature deaths and more than 200,000 cases of childhood asthma each year.

Kassel still lives in New York City, where the remaining diesel buses now run on low-sulfur fuel. The dirtiest of the diesels are gone; 344 city buses run on natural gas, and 325 electric hybrids have been ordered. "Cleaning up diesel vehicles is going to save literally thousands of lives each year," says Kassel. "And New York City's buses started it all."
-- Whitney Royster