Last Update: July 25, 2015

Diesel combustion exhaust is a major source of atmospheric soot and fine particles, which is a fraction of air pollution implicated in human heart and lung damage. Diesel exhaust also contains nanoparticles. See:  (

While the study of nanoparticles and nanotoxicology is still in its infancy, the full health effects from nanoparticles produced by all types of diesel are unknown. Long term effects still need to be clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases.

It should be noted that the types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution. One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.

Diesel engines emit a complex mixture of air pollutants, composed of gaseous and solid material. The visible emissions in diesel exhaust are known as particulate matter or PM. In 1998, California identified diesel exhaust particulate matter (PM) as a toxic air contaminant based on its potential to cause cancer, premature death, and other health problems. Diesel engines also contribute to California's fine particulate matter (PM2.5) air quality problems. Those most vulnerable are children whose lungs are still developing and the elderly who may have other serious health problems. Based on year 2005 emissions in California, diesel PM contributes each year to approximately 3,500 premature deaths and thousands of hospital admissions, asthma attacks and other respiratory symptoms, and lost workdays. Overall, diesel engine emissions are responsible for the majority of California's known cancer risk from outdoor air pollutants. In addition, diesel soot causes visibility reduction and is a potent global warmer. ARB has sponsored diesel health-related research. See:  (

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Health Effects of Diesel Exhaust

Diesel fuel is widely used throughout our society. It powers the trucks that deliver products to our communities, the buses that carry us to school and work, the agricultural equipment that plants and harvests our food, and the backup generators that can provide electricity during emergencies. It is also used for many other applications. Diesel engines have historically been more versatile and cheaper to run than gasoline engines or other sources of power. Unfortunately, the exhaust from these engines contains substances that can pose a risk to human health. See:  ( and: A fact sheet by Cal/EPA's Office of Environmental Health Hazard Assessment and the American Lung Association

In 1998, the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) completed a comprehensive health assessment of diesel exhaust. This assessment formed the basis for a decision by the California Air Resources Board (ARB) to formally identify particles in diesel exhaust as a toxic air contaminant that may pose a threat to human health. The American Lung Association of California (ALAC) and its 15 local associations work to prevent lung disease and promote lung health. Since 1904, the American Lung Association has been fighting lung disease through education, community service, advocacy and research.

What is diesel exhaust? Diesel exhaust is produced when an engine burns diesel fuel. It is a complex mixture of thousands of gases and fine particles (commonly known as soot) that contains more than 40 toxic air contaminants. These include many known or suspected cancer-causing substances, such as benzene, arsenic and formaldehyde. It also contains other harmful pollutants, including nitrogen oxides (a component of urban smog).

How are people exposed to diesel exhaust? Diesel exhaust particles and gases are suspended in the air, so exposure to this pollutant occurs whenever a person breathes air that contains these substances. The prevalence of diesel-powered engines makes it almost impossible to avoid exposure to diesel exhaust or its byproducts, regardless of whether you live in a rural or urban setting. However, people living and working in urban and industrial areas are more likely to be exposed to this pollutant. Those spending time on or near roads and freeways, truck loading and unloading operations, operating diesel-powered machinery or working near diesel equipment face exposure to higher levels of diesel exhaust and face higher health risks.

What are the health effects of diesel exhaust? As we breathe, the toxic gases and small particles of diesel exhaust are drawn into the lungs. The microscopic particles in diesel exhaust are less than one-fifth the thickness of a human hair and are small enough to penetrate deep into the lungs, where they contribute to a range of health problems.

Diesel exhaust and many individual substances contained in it (including arsenic, benzene, formaldehyde and nickel) have the potential to contribute to mutations in cells that can lead to cancer. In fact, long-term exposure to diesel exhaust particles poses the highest cancer risk of any toxic air contaminant evaluated by OEHHA. ARB estimates that about 70 percent of the cancer risk that the average Californian faces from breathing toxic air pollutants stems from diesel exhaust particles.

In its comprehensive assessment of diesel exhaust, OEHHA analyzed more than 30 studies of people who worked around diesel equipment, including truck drivers, railroad workers and equipment operators. The studies showed these workers were more likely to develop lung cancer than workers who were not exposed to diesel emissions. These studies provide strong evidence that long-term occupational exposure to diesel exhaust increases the risk of lung cancer. Using information from OEHHA's assessment, ARB estimates that diesel-particle levels measured in California's air in 2000 could cause 540 "excess" cancers (beyond what would occur if there were no diesel particles in the air) in a population of 1 million people over a 70-year lifetime. Other researchers and scientific organizations, including the National Institute for Occupational Safety and Health, have calculated cancer risks from diesel exhaust that are similar to those developed by OEHHA and ARB.

Exposure to diesel exhaust can have immediate health effects. Diesel exhaust can irritate the eyes, nose, throat and lungs, and it can cause coughs, headaches, lightheadedness and nausea. In studies with human volunteers, diesel exhaust particles made people with allergies more susceptible to the materials to which they are allergic, such as dust and pollen. Exposure to diesel exhaust also causes inflammation in the lungs, which may aggravate chronic respiratory symptoms and increase the frequency or intensity of asthma attacks.

Diesel engines are a major source of fine-particle pollution. The elderly and people with emphysema, asthma, and chronic heart and lung disease are especially sensitive to fine-particle pollution. Numerous studies have linked elevated particle levels in the air to increased hospital admissions, emergency room visits, asthma attacks and premature deaths among those suffering from respiratory problems. Because children's lungs and respiratory systems are still developing, they are also more susceptible than healthy adults to fine particles. Exposure to fine particles is associated with increased frequency of childhood illnesses and can also reduce lung function in children.

Like all fuel-burning equipment, diesel engines produce nitrogen oxides, a common air pollutant in California. Nitrogen oxides can damage lung tissue, lower the body's resistance to respiratory infection and worsen chronic lung diseases, such as asthma. They also react with other pollutants in the atmosphere to form ozone, a major component of smog.

What is being done to reduce the health risks from diesel exhaust? Improvements to diesel fuel and diesel engines have already reduced emissions of some of the pollutants associated with diesel exhaust. However, diesel exhaust is still one of the most widespread and toxic substances in California's air.

ARB's Diesel Risk Reduction Plan, when fully implemented, will result in a 75 percent reduction in particle emissions from diesel equipment by 2010 (compared to 2000 levels), and an 85 percent reduction by 2020. The plan calls for the use of cleaner-burning diesel fuel, retrofitting of existing engines with particle-trapping filters, and the use in new diesel engines of advanced technologies that produce nearly 90 percent fewer particle emissions, as well as the use of alternative fuels.

The use of other fuels, such as natural gas, propane and electricity offer alternatives to diesel fuel. All of them produce fewer polluting emissions than current formulations of diesel fuel. As a result of ARB and local air-quality regulations, public transit agencies throughout California are using increasing numbers of passenger buses that operate with alternative fuels or retrofitted equipment.

Introduction Diesel exhaust is a pervasive airborne contaminant in workplaces where diesel-powered equipment is used. Due to expanding use of diesel equipment, more and more workers are exposed to diesel exhaust. More than one million workers are exposed to diesel exhaust and face the risk of adverse health effects, ranging from headaches and nausea to cancer and respiratory disease. Such workers include mine workers, bridge and tunnel workers, railroad workers, loading dock workers, truck drivers, material handling machine operators, farm workers, longshoring employees, and auto, truck and bus maintenance garage workers. See:   (

There are currently no standards for diesel exhaust as a unique hazard. However, exposures to various chemical components of diesel exhaust are addressed in specific standards for the general industry and shipyard employment.

Standards This section highlights OSHA standards, Federal Registers (rules, proposed rules, and notices), directives (instructions for compliance officers), standard interpretations (official letters of interpretation of the standards), and other federal standards related to diesel exhaust.

Diesel fuel exhaust from vehicles can pollute the air with harmful chemicals. See:  (

What are diesel fuel and exhaust?

Diesel fuel is a petroleum product that is used in diesel engines in some automobiles, generators, light-duty and heavy-duty trucks, and railroad locomotives. It is a mixture of petroleum compounds and is less expensive to produce than gasoline.

Diesel exhaust is a mixture of gases and tiny particles. This exhaust contains carbon dioxide, carbon monoxide, nitrogen oxides, sulfur compounds, formaldehyde, benzene, volatile organic compounds, and other gases. Greenhouse gases released by this exhaust affect climate change.

How might I be exposed to diesel fuel?

You can be exposed to diesel fuel if you breathe air that has been contaminated with diesel exhaust or vapors, or if you drink or swim in water that has been contaminated with diesel fuel from a spill or leaking underground storage tank.

At work, you can be exposed to diesel fuel, diesel fuel vapors, and diesel exhaust if you are a truck or forklift driver, railroad worker, mine worker, auto mechanic, vehicle maintenance worker, firefighter, farm worker, lumberjack, trucking company worker, toll booth collector, or worker at a facility where diesel-powered equipment is used.

You can also be exposed to diesel exhaust if you work in a tunnel, bus garage, parking garage, bridge, loading dock, facility where diesel-powered equipment is used, or in or near areas where vehicles with diesel engines are used, stored, or maintained.

How can diesel fuel affect my health?

Diesel exhaust is "reasonably anticipated to be a human carcinogen," according to the Eleventh Report on Carcinogens published by the National Toxicology Program, because long-term exposure to diesel exhaust may cause lung cancer and other lung damage.

Long-term exposure to diesel exhaust can cause chronic respiratory symptoms such as persistent cough and mucous, bronchitis, and reduced lung capacity. Long-term exposure to diesel fuel vapors can cause kidney damage and lower the blood's ability to clot. Swallowing diesel oil can cause collapse, rapid low blood pressure, and loss of vision.

In combination with other cancer-causing substances, such as cigarette smoke, welding fumes, and asbestos, long-term exposure to diesel exhaust can increase your risk of developing lung cancer.

If you have asthma, emphysema, heart disease, or allergies, exposure to diesel exhaust can worsen those symptoms.

Short-term exposure to diesel exhaust can irritate the eyes, throat, and lungs. It can cause light-headedness, feeling "high," headache, heartburn, weakness, numbness, tingling extremities, chest tightness, wheezing, coughing, nausea, and vomiting.

Short-term exposure to diesel fuel vapors can cause difficulty breathing, nausea, eye irritation, increased blood pressure, headache, light-headedness, loss of appetite, poor coordination, and difficulty concentrating.

Swallowing diesel oil can cause severe abdominal pain, vomiting, vomiting blood, swollen throat, burning of the food pipe, irritated skin, and severe pain or burning in the throat, nose, eyes, ears, lips or tongue.

About the Author(s)

David Herron : David Herron is a writer and software engineer focusing on the wise use of technology. He is especially interested in clean energy technologies like solar power, wind power, and electric cars. David worked for nearly 30 years in Silicon Valley on software ranging from electronic mail systems, to video streaming, to the Java programming language, and has published several books on Node.js programming and electric vehicles.
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