Diesel Engine Exhaust

Why am I being warned about potential exposure to diesel engine exhaust?
  • Diesel engine exhaust is on the Proposition 65 list.
    • The International Agency for Research on Cancer (IARC) found that it is carcinogenic to humans and causes lung cancer. The US Environmental Protection Agency (US EPA) found that it is likely carcinogenic to humans. Other agencies made similar findings.
  • California’s Proposition 65 requires businesses to warn people before exposing them to a significant amount of a chemical listed under Proposition 65 for cancer or reproductive toxicity.
What is diesel engine exhaust?
  • Diesel engine exhaust is produced when engines, including those in vehicles and generators, burn diesel fuel.
  • It is a mixture of thousands of chemicals released as gases or particles (soot).
  • More than 40 chemicals listed for cancer are present in diesel engine exhaust. These include benzene, arsenic, formaldehyde, acetaldehyde, 1,3-butadiene, lead, and numerous polycyclic aromatic hydrocarbons (a class of chemicals created by burning fuels and other substances).
How does exposure to diesel engine exhaust occur?
An image of a diesel truck emitting black smoke from an exhaust pipe..
  • Exposure occurs by breathing in air containing diesel engine exhaust. Sources include diesel-powered motor vehicles, ships, trains, generators, and other diesel-powered equipment. 
  • Exposure also occurs through contact with diesel engine gases and exhaust particles, which may be absorbed through the skin or unintentionally ingested. These contaminants may:
    • Be present on the surface of diesel-powered vehicles and equipment.
    • Enter vehicles, homes, and other structures, where they can settle on surfaces and be absorbed into dust particles.
Main ways you can be exposed to diesel engine exhaust:
1. Breathing in air and dust containing diesel exhaust 2. Swallowing contaminated soot and dust deposited on the hands and transferred to the mouth 3. Touching contaminated surfaces and dust, and absorbing contaminants through the skin
  • During pregnancy, some chemicals in diesel engine exhaust can pass from mother to baby.
How can I reduce my exposure to diesel engine exhaust?
  • Always start and operate a diesel engine in a well-ventilated area.
  • Avoid breathing in diesel engine exhaust. Whenever practical, do not stand next to operating diesel engines.
  • Avoid idling diesel engine vehicles, where possible.
  • Do not use diesel-powered engines in enclosed spaces.
  • Do not modify or tamper with a diesel engine’s exhaust system.
  • Install backup and portable diesel-powered generators well away from your home so that exhaust does not come in through open windows and doors.
  • Consider replacing diesel-powered engines with alternatives such as engines powered by natural gas, propane, or electricity.
  • Perform regular maintenance and frequent tune-ups of all diesel-powered equipment.
  • When servicing or maintaining diesel-powered engines, prevent skin contact with exhaust by wearing gloves. Wash your hands when done, and before preparing food or eating.
  • California restricts the use of certain types of diesel-powered vehicles. You can learn more about statewide diesel regulations from the California Air Resources Board.
For more information:

General Fact Sheets and Resources

Scientific Information on Diesel Engine Exhaust

Proposition 65

Updated July 2024
Fact Sheet - Diesel Engine Exhaust

Related Chemical(s)

Related Product or Place

References
Chemical