SACE | Southern Alliance for Clean Energy

Diesel Impact Overview


Diesel exhaust is emitted from engines that use diesel fuel to operate. Diesel exhaust contains particulate matter, nitrogen oxides and over 40 chemicals that are classified as “hazardous air pollutants” under the Clean Air Act. Primary sources of diesel exhaust include trucks, buses, construction equipment, trains, and marine vessels. Post 2007 on-road diesel engines are 90 percent cleaner than in previous years, but millions of existing “legacy” vehicles will continue to pollute our air for decades.

Many studies show that diesel exhaust contributes to cancer, asthma, premature death, as well as respiratory illnesses. Diesel pollution contributes to high levels of ground level ozone, smog, acid rain and global warming.

concrete_truck_plume.jpgDiesel vehicles are often referred to as the workhorse of the American economy. They help deliver our children to school, construct and repair our roads, and transport our goods across the country. Diesel engines are durable. They can last 20 to 30 years making them appealing to many industries. The same thing that has made diesel engines appealing now contributes to a growing air quality and health concern.

In recent years, the U.S. Environmental Protection Agency (EPA) has established new emissions and fuel standards for both on and off-road diesel engines that will make new engines built in 2007 and 2010 or later, respectively, to be 90 percent cleaner. Unfortunately, the rule does not affect existing “legacy” engines built before 2007. This means that high polluting diesel engines built as late as 2006 will be on the road until 2036 or later–emitting high levels of pollution for the next thirty or more years.

In today’s economy many fleet owners may not have the option to replace their fleet with the newer, cleaner vehicles. However, there are cost effective solutions, for any budget, that can help reduce the pollution from and exposure to diesel exhaust on existing engines. They include:

  • Retrofit: On equipment that still has some useful life left, engines can be retrofitted with an emission control device. Retrofit technologies are available for a variety of applications and can reduce emissions by up to 90 percent.
  • Refuel: Switching to cleaner fuels such as alternative diesel fuels or ultra-low-sulfur diesel fuel can achieve modest reductions in pollutants. These fuels can also facilitate the use of advanced retrofit technologies, resulting in even less pollution.
  • Repower: The body or chassis of some equipment can last through many decades of use, beyond the life of the original engine. Installing a new low-emission engine in an older chassis can allow the machine to run for many more years.
  • Replace: If equipment is old and near the end of its life, replacing it with a new lower-emission model ahead of schedule can result in substantial emission reductions.
  • Rebuild or repair: Emissions gradually increase over the life of an engine. Performing routine maintenance and periodic engine rebuilds can keep emission rates at or near original levels.
  • Reduce idling: Idling equipment is not only polluting, but also a waste of fuel. Limiting idle time can save money by reducing fuel usage and wear and tear on the engine.

Using a combination of these strategies can significantly reduce diesel exhaust and the negative impacts it has on citizens and our environment. Please join us in reducing diesel pollution.


Anyone who has been behind a pre-2007 diesel vehicle is familiar with the black smoke that often makes it hard to see or leaves you choking on its exhaust. In fact, the exhaust from diesel engines have been proven to contribute to a number of illnesses, including asthma, respiratory disease, irritation of the eyes, nose and throat and heart problems. Diesel pollution is also known to cause cancer and lead to premature death.

Studies of occupational exposure to diesel exhaust have been conducted in truck drivers, bus drivers, dockworkers and railroad workers over the past three decades. A 1999 meta-analysis of all occupational studies published in the American Journal of Public Health concluded that workers exposed to diesel exhaust have a 47 percent higher risk of lung cancer relative to unexposed workers.

There are no safe levels of diesel emissions. It affects everyone and is a localized issue because the emissions tend to concentrate in “hot spots” within a mile of where the pollution occurs. Children and the elderly face the greatest risks. They are more vulnerable because their lungs are still developing and they also breathe faster, spend more time outdoors, and breathe in more air for their size than adults. To determine the health impacts in your area, click here .

Particulate matter and ozone from diesel engines also affect plant growth and development in many of the same ways that they affect human lung growth and function. Particulate matter can leave a fine layer of “soot” on plants while ozone affects plant tissue, interfering with growth and development. The same soot that deposits on plants can leave a thick residue on buildings and statues causing permanent damage and decay. Further, the acidic nitrate pollution from diesel exhaust disrupts the natural aquatic ecosystems by leaching into the soil and contributing to excessive levels of nitrogen and other chemicals in our waterways.

Diesel exhaust also contains black carbon, a global warming pollutant. Like an asphalt road, black carbon soot from diesel engines absorbs sunlight and heats up the atmosphere. Studies show that black carbon contributes to global warming by hastening the melting of ice.

Black carbon is also a killer. “Combustion-related air pollution is estimated to be responsible for nearly 2.5 million premature deaths annually around the world. By reducing diesel pollution now we can begin to see more immediate reductions in the pollution that contributes to global warming.

Relevant Publications

MAP-21 Transportation Bill: Congestion Mitigation and Air Quality Program Guidance

Health Impacts of Diesel, Based on Data from the National Scales Air Toxics Health and Climate Change.

U.S. EPA Health Assessment Document for Diesel Engine Exhaust

School Buses and Human Health