This is a story about a problem that we can solve — with a bit of help from Congress.

Fifteen years ago, there was no such thing as clean diesel. City transit riders held their breath when the bus pulled away from the curb, and parents worried about their children being exposed to plumes of black smoke from the tailpipes of old school buses. Diesel trucks brought us the goods we wanted, but with a side dish of pollution.

Today, new diesel buses, trucks and other engines are more than 90 percent cleaner. These new diesel engines operate smoke-free, have created thousands of new jobs in the hard-hit engine manufacturing sector and elsewhere, and are helping to save fuel costs by operating more efficiently. A national diesel cleanup effort has enjoyed broad, bipartisan support.

President Bill Clinton signed the first regulation to clean up diesel trucks and buses in 2001, and President George W. Bush signed the next regulation to clean up diesel construction and farm equipment in 2004.

In 2005, Congress followed up by passing the Diesel Emissions Reduction Act (DERA), a five-year effort to accelerate the cleanup of the millions of dirty diesel engines still in use. DERA sought to improve America's air quality by modernizing older diesel engines and equipment through engine replacements and retrofits in all 50 states.

From 2008 through 2010, Maryland received more than $19.9 million in DERA funding — the fifth-highest amount of all 50 states — for several important projects to upgrade, replace or retrofit school buses, marine engines, construction equipment, freight trailers and locomotive engines with new clean diesel technology to reduce emissions.

These include programs operated by the Maryland Clean Diesel Grant Program (school and transit bus upgrades); Anne Arundel, Montgomery and Prince George's counties (public school bus retrofits); Chesapeake Bay Foundation (repower educational, waterman and tug vessels); Maryland Department of the Environment (school bus upgrades); Maryland Transit Administration (transit bus upgrades and repower of locomotive engines with ultra-clean generator set technology); and other local projects to reduce emissions in trash haulers, dump trucks, commercial trucks, harbor craft and dredging equipment, ferries and tugboats.

Unfortunately, this entire program may be coming to an end.

Just a few months ago, DERA was overwhelmingly reauthorized for another five years. But in February, the president's budget included no money for DERA, and Congress will soon debate what to do. We think Congress should continue to fund DERA, and here's why.

Every dollar invested in diesel retrofits and replacements yields at least $13 in health benefits — fewer asthma emergencies, fewer lost work days, and healthier communities. Plus, DERA has provided federal funds in a competitive process that encourages state, local or private funding matches. By doing so, DERA has been able to leverage roughly three dollars in state, local or private funding for every federal dollar. It's hard to find a better investment in public health.

DERA provides the seed funding for thousands of fleet owners, farmers and other diesel users to buy the new engines, retrofits and technologies. In turn, this is unlocking the potential of America's engine makers and equipment innovators. U.S. engine companies are producing the most durable, most efficient and cleanest diesel engines in the world, and other clean diesel manufacturers are making the catalysts and filters that can make older diesel engines much, much cleaner during the years of service that they have left.

We understand that, in this very serious budget climate, tough choices have to be made. But the issue of clean air shouldn't be a partisan issue, and diesel cleanup has never been one. Last December, Democrats and Republicans came together to overwhelmingly reauthorize DERA because they recognized that there was no such thing as Democratic air or Republican air.

If ever a program made sense and had the support of environmental, labor, public health and industry groups, this is the one. With 11 million dirty diesel engines still on our roads, construction sites and farms, Congress needs to continue funding DERA.

Allen Schaeffer is the executive director of the Diesel Technology Forum in Frederick. Richard Kassel directs the Clean Fuels and Vehicles Project at the Natural Resources Defense Council in New York.