What are nitrogen oxides?

Nitrogen oxides are a group of gases that are composed of nitrogen and oxygen. Two of the most common nitrogen oxides are nitric oxide and nitrogen dioxide. The chemical formula for nitric oxide is NO; for nitrogen dioxide, it is NO₂. Nitrous oxide, N₂O, is a greenhouse gas.
 
Nitric oxide is a gas with a sharp, sweet smell; it is colorless to brown at room temperature. Nitrogen dioxide is a colorless to brown liquid at room temperature, with a strong, harsh odor. It becomes a reddish-brown gas at temperatures above 70 degrees F. 

Nitrogen oxides are released into the air from motor vehicle exhaust, or the burning of coal, oil, and natural gas, especially from electric power plants. They are also released during industrial processes such as welding, electroplating, engraving, and dynamite blasting. 

Nitrogen oxides, when combined with volatile organic compounds, form ground-level ozone, or smog. They are also produced by cigarette smoking. 

Nitric oxide is used to bleach rayon and produce nitric acid. Nitrogen dioxide is used to produce rocket fuels, explosives, and other chemicals. Nitrogen dioxide is sometimes used to bleach flour.

Nitrogen oxides are common pollutants found in most of the air in the United States. You can be exposed to nitrogen oxides outdoors by breathing air that contains it, especially if you live near a coal-burning electric power plant or areas with heavy motor vehicle traffic. You can be exposed to higher levels if air pollution and smog levels are high. 

You can be exposed at home if you burn wood, or use a kerosene heater or gas stove. 

You can be exposed at home or at work, indoors or outdoors, through smoking cigarettes or breathing second-hand cigarette smoke. 

You can be exposed at work if you work in a facility that produces nitric acid, explosives such as dynamite and TNT, or welded metals.

Exposure to high industrial levels of nitric oxide and nitrogen dioxide can cause death. It can cause collapse, rapid burning and swelling of tissues in the throat and upper respiratory tract, difficult breathing, throat spasms, and fluid build-up in the lungs. It can interfere with the blood's ability to carry oxygen through the body, causing headache, fatigue, dizziness, and a blue color to the skin and lips. 

Industrial exposure to nitrogen dioxide may cause genetic mutations, damage a developing fetus, and decrease fertility in women. Repeated exposure to high levels of nitrogen dioxide may lead to permanent lung damage. Industrial exposure to nitric oxide can cause unconsciousness, vomiting, mental confusion, and damage to the teeth. Industrial skin or eye contact with high concentrations of nitrogen oxide gases or nitrogen dioxide liquid can cause serious burns. 

Long-term exposure to nitrogen oxides in smog can trigger serious respiratory problems, including damage to lung tissue and reduction in lung function. Exposure to low levels of nitrogen oxides in smog can irritate the eyes, nose, throat, and lungs. It can cause coughing, shortness of breath, fatigue, and nausea. 

If you think you have been exposed to nitrogen oxides, contact your health care professional. 

For poisoning emergencies or questions about possible poisons, please contact your local poison control center at 1-800-222-1222.

Locations where Nitrogen Oxides may be found
City	Farm	Town	U.S.-Mexico Border	Port
Airplanes and Air Travel Climate Change Factory Homes Hospital Offices and Stores Outdoor Air Park School School Bus Vehicles	Climate Change Homes Off-road Vehicles Outdoor Air Vehicles	Climate Change Factory Homes Offices and Stores Outdoor Air Park School School Bus Vehicles	Auto Shop Border Crossing Climate Change Homes Illegal Dumps and Tire Piles Maquiladora Outdoor Air Park Tienda Trash Burning Vehicles	Beach Climate Change Cruise Ship Homes Marina and Boats Offices and Stores Outdoor Air Shipping Shipyard Vehicles

Last Updated: November 06, 2008