Air Pollution from Large Diesel Trucks and Buses

Posted: 01-Jan-1995; Updated: 02-Sep-2003

Large Diesel Trucks and Buses Emit Millions of Tons of Air Pollution Each Year

• Large diesel trucks and buses will emit millions of tons of air pollution this year. According to the U.S. Environmental Protection Agency (EPA) these emissions will include 2.2 million tons of smog-forming oxides of nitrogen (NOx) and 131,000 tons of fine particulates -- probable carcinogens that are breathed deep into the lungs. (see http://www.epa.gov/otaq/regs/hd-hwy/1999nprm/99ria15.pdf).
• Progress in cleaning up air pollution from large trucks and buses has lagged behind clean up of passenger vehicles. There have also been serious compliance problems with existing standards for diesel fuel (see http://www.epa.gov/compliance/).

Diesel Emissions Are a Human Health and Environmental Hazard

Diesel Particulates:

• The particles in diesel exhaust are very small, can be breathed deep into the lungs and have very serious respiratory effects.
• The chemicals that adhere or adsorb to the diesel particles are likely mutagenic and carcinogenic.
• The U.S. National Institute for Occupational Safety and Health, and World Health Organization have determined that diesel exhaust is a potential or probable carcinogen, and California EPA has classified it as a known carcinogen.
• In March 2000 a study by the South Coast Air Quality Management District of Los Angeles found that emissions of diesel particulates are responsible for 70% of the risk associated with carcinogenic air pollutants (see http://www.aqmd.gov/matesiidf/matestoc.htm).

Oxides of Nitrogen (NOx) and its Byproducts:

• Are a main ingredient in smog formation.
• Contribute to harmful fine particles.
• Contribute to acid deposition in forests, lakes and streams.
• Contribute to eutrophication of coastal estuaries such as the Chesapeake Bay.
• Contribute to haze in urban areas and national parks.

Enhanced Emission Control Technology for Diesel Engines Requires Cleaner Diesel Fuel

• Cleaner diesel that is low in sulfur is necessary for diesel particulate traps and NOx adsorbers to function effectively. These technologies are capable of reducing particulate and NOx emissions from large trucks and buses by as much as 90%.
• In April 2000, a world-wide alliance of automobile and engine manufacturers indicated that dramatic reductions in the sulfur content of diesel would be necessary for effective NOx and particulate controls for diesel engines (see http://www.autoalliance.org/).
• Low sulfur diesel fuel also is needed to enable the control technology for diesel-powered passenger cars, minivans, pickup trucks, and SUVs to meet recently-established tailpipe emission standards

Current Diesel Fuel Standards Allow High Levels of Sulfur and Are Inadequate

• Under legal standards that took effect in 1993, the allowed sulfur content of diesel is 500 parts per million (ppm).
• The actual average national sulfur content of diesel is about 340 ppm, outside of California.
• California also allows sulfur levels in diesel up to 500 ppm, but the actual average is substantially lower.

Cleaner Low-Sulfur Diesel Fuel Is Achievable in the U.S.

• ARCO (now merged w/BP AMOCO) voluntarily made available low sulfur diesel fuel in southern California. This fuel will have a maximum sulfur content of 15 ppm (see http://www.dieselnet.com/news/9912arco.html).
• Clean diesel is enabling large diesel fleet owners to retrofit their fleets with exhaust control technologies and thereby achieve immediate pollution reductions.

Cleaner Low-Sulfur Diesel Fuel Is Being Implemented Internationally

• The European Union has adopted fuel specifications that limit the sulfur content of diesel to 50 ppm by 2005.
• The United Kingdom will soon be achieving sulfur levels of 50 ppm.
• Finland has tax incentives for diesel with sulfur levels under 50 ppm, and this fuel comprises about 90% of the national market.
• Japan has proposed to limit sulfur in diesel to 50 ppm.