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Nitrogen Oxides

What are Nitrogen Oxides?

Nitrogen oxides are a group of seven gases and compounds composed of nitrogen and oxygen, sometimes collectively known as NOx gases.  The two most common and hazardous oxides of nitrogen are nitric oxide and nitrogen dioxide. Nitrous oxide, commonly called laughing gas, is a greenhouse gas that contributes to global warming.

Nitrogen oxide pollution is emitted from vehicle exhaust, and the burning of coal, oil, diesel fuel, and natural gas, especially from electric power plants. They are also emitted by cigarettes, gas stoves, kerosene heaters, wood burning, and silos that contain silage.

Nitrogen oxides can create environmental health hazards when they react with sunlight and other chemicals to form smog. Nitrogen oxides and sulfur dioxide react with substances in the atmosphere to form acid rain.

Nitrogen dioxide is used to produce rocket fuels and explosives.

Nitrous oxide is emitted during agricultural and industrial activities, and during combustion of fossil fuels and solid waste.  Additionally, it is used as an anesthetic.

See also: Factories Fuel Industry Homes Vehicles and Engines Power Plants Air Pollution Agriculture

Where are Nitrogen Oxides found?

  • Air – vehicle exhaust, emissions from coal-fired power plants and appliances that burn fossil fuels, cigarette smoke, and secondhand smoke are nitrogen oxide sources
  • Consumer products – cigarettes and vehicles are nitrogen oxide sources

How can I be exposed to Nitrogen Oxides?

Nitrogen Oxides commonly enter(s) the body through:


Inhalation (breathing)

  • Breathing emissions from nitrogen oxide sources like coal-fired power plants, vehicles, and appliances that burn fossil fuels; smoking cigarettes; and breathing secondhand smoke or smog

Skin contact

  • Exposure to high concentrations of nitrogen oxide gases or liquid nitrogen dioxide

What happens when I am exposed to Nitrogen Oxides?

Short-term exposure:
Health effects from breathing nitrogen oxides can include:

  • Irritation of the respiratory system, eyes, and skin
  • Aggravation of respiratory diseases, particularly asthma
  • Coughing and choking
  • Nausea
  • Headache
  • Abdominal pain
  • Difficulty breathing

Skin and eye contact with nitrogen oxide gases or liquid nitrogen dioxide can cause irritation and burns.

Long-term exposure:
Long-term exposure to low levels of nitrogen dioxide can cause:

  • Asthma
  • Respiratory infections

Health effects from very high levels of nitrogen oxides can include:

  • Death
  • Genetic mutations
  • Harm to a developing fetus
  • Decreased female fertility
  • Spasms
  • Swelling of the throat
  • Rapid pulse 
  • Dilated heart

Who is at risk for exposure to Nitrogen Oxides?

  • Consumers
    • Everyone is exposed to small amounts of nitrogen oxides in the air. Some heating and cooking appliances use fossil fuels; some people live near coal-fired power plants.
  • Cigarette smokers
    • Cigarette smoke and secondhand smoke are nitrogen oxide sources.

Reduce your risk

If you think your health has been affected by exposure to nitrogen oxides, contact your health care professional. 

Always wash your hands thoroughly after handling chemicals. For poisoning emergencies or questions about possible poisons, please contact your local poison control center at 1-800-222-1222.


  • Do you live near a coal-burning electric power plant or areas with heavy motor vehicle traffic?
  • Do you live in an area with high levels of air pollution and smog?
  • Do you, or does anyone in your household, smoke tobacco products?
  • How frequently are you exposed to vehicle exhaust or gas stations?
  • Use proper ventilation, especially if you have an indoor gas stove or space heaters.
  • Make sure gas stoves, furnaces, and space heaters are properly vented.
  • Keep appliances properly adjusted.
  • Have gas appliances routinely inspected by a trained professional. Repair any leaks promptly.
  • Install and use an exhaust fan vented over gas stoves.
  • Use proper fuel in kerosene space heaters.
  • Open flues when using fireplaces.
  • If you smoke, quit. Avoid secondhand smoke.
  • Limit your time near idling cars, trucks, or buses.
  • Do not idle the car inside a garage.
  • Farm families should not allow children to play near silos that contain silage.
  • Don’t let children play near gas stations, idling cars, or busy highways.

National Library of Medicine Resources and Databases

Additional Resources

  • Nitrogen Oxides. ToxFAQs
    Agency for Toxic Substances and Disease Registry
    Factsheet with answers to the most frequently asked questions about nitrogen oxides exposure and their effects on human health, developed by a federal public health agency that protects communities from harmful health effects related to exposure to natural and man-made hazardous substances.
  • Acid Rain
    Environmental Protection Agency
    Educational resources for students and teachers on acid rain, as well as information on its effects, and programs and policies aimed at reducing its harm on the environment.
  • Acid Rain Students Site
    Environmental Protection Agency
    A student website on the causes and effects of acid rain. The English and Spanish website includes games, activities, animation, and information on reducing pollutants.
  • Nitrogen Dioxide (NO2) Pollution
    Environmental Protection Agency
    Information on nitrogen dioxide pollution, including sources and effects, as well as setting, reviewing, and implementing standards to protect human health and the environment.
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