Description
Nitrogen oxides are a family of gases produced whenever fuel burns. Nitrogen dioxide (NO2), a corrosive, brownish gas, is of major concern to the health of humans and the environment. Nitrogen dioxide is one of the six major pollutants of outdoor air in the U.S. It is a major cause of ground-level ozone (smog) and fine particulate soot in air. On the other hand, nitrogen oxide (NO) is fairly benign, but can be converted into nitrogen dioxide.
Nitrogen dioxide is present in vehicle exhaust and in the fumes from kerosene heaters, unvented gas stoves, space heaters, fireplaces, gas-fueled clothes dryers, and tobacco smoke. Nitrogen dioxide is also present in emissions from electric utilities and industrial boilers.
Nitrogen dioxide, and the resulting ozone and particulates, trigger asthma attacks. They also may cause asthma and other respiratory ailments.
When NO2 combines with water, it can form nitric acid, which contributes to acid rain. Acid rain can harm fish, damage forests and plants, and erode buildings. Nitrogen dioxide also increases the levels of nitrates and nitrites in water, and causes explosive growths of algae that deplete oxygen in water, killing fish and other aquatic life.
Children can be exposed to nitrogen dioxide indoors where gas appliances are used without adequate ventilation and if they live with smokers. Outdoors, ozone levels tend to be highest during the summer.
Health Effects
Immediate Health Effects
- If SWALLOWED, nitrogen oxides is Not Available
- If ABSORBED THROUGH SKIN, nitrogen oxides is Not Available
- If INHALED (SNIFFED OR BREATHED IN), nitrogen oxides is Very Highly Toxic
Longterm or Delayed Health Effects
Other
- At low levels, nitrogen dioxide fumes can irritate the lungs, eyes, nose and throat and cause coughing, fatigue and nausea. However, acute effects from indoor exposures are unlikely, except in occupational settings or as a result of faulty gas appliances in homes.
- Exposure to NO2 may lower resistance to respiratory infections such as the flu, and may harm people with respiratory illness such as asthma, emphysema, and bronchitis. Children frequently exposed to elevated NO2 levels in air may experience higher rates of respiratory infections.
- At levels likely to occur in air pollution, NO2 may increase the likelihood of asthma attacks in asthmatics. NO2 may also make asthmatics more sensitive to other allergens and asthma triggers, and may heighten respiratory irritation when they exercise. In some studies, increased levels of NO2 and other air pollutants have corresponded with increases in the number of asthma-related emergency room visits.
- Ozone or smog, a byproduct of NO2, has been linked ot heart disease. Recent studies show that ozone causes arteries to close.
- In offspring of test animals exposed during pregnancy, nitrogen dioxide has caused decreased birth weights and affected coordination and behavior. Long-term or repeated exposure may cause genetic mutations in humans.
How Exposures Occur
Combustion Appliance
- Children can inhale nitrogen dioxide in homes where fuel-burning appliances, including gas stoves, gas space heaters, kerosene heaters, furnaces, and wood stoves are used, especially if they are in disrepair, used improperly or without proper ventilation.
Grain Silos
- Children may inhale nitrogen dioxide if they enter silos that contain fermenting corn, hay, silage or grain.
Automobile Exhaust
- Children can inhale nitrogen dioxide from car exhaust, particularly if they live close to busy streets or highways. Children in high-traffic urban environments are likely to breathe in more NO2 from car exhaust than kids in rural areas, with levels peaking during rush hours.
In enclosed spaces, such as garages, NO2 can reach dangerous levels if adequate ventilation is not provided.
Recent studies show that diesel school buses a source of exposure to school children.
Industrial Pollution
- Children can inhale nitrogen dioxide from polluted outdoor air, particularly if they live near polluting facilities such as coal-fired electric utilities. NO2 primarily enters the air from fuel combustion by electric power plants and from automobile exhaust (see below).
Tobacco Smoke
- Children can inhale traces of NO2 from secondhand tobacco smoke. NO2 levels may be 4-10 times higher in sidestream smoke (emitted between the puffs of a burning cigarette, pipe, or cigar) than in mainstream smoke (the smoke exhaled by the smoker).
Welding
- Children can inhale nitrogen dioxide if someone is doing electric arc welding in the near vicinity.
Significant Statistics
Indoor levels of nitrogen dioxide often exceed outdoor levels in homes where gas stoves, kerosene heaters or un-vented gas space heaters are used. The average level of nitrogen dioxide in homes without these appliances is about half that of levels found outdoors.
Indoor Air Quality-An Introduction: Nitrogen Dioxide. U.S. Environmental Protection
Agency.http://www.epa.gov/iaq/no2.html
Since 1970, emissions of the six principal air pollutants have decreased significantly with the exception of nitrogen oxides, which have increased approximately 10% over this period, according to the U.S. Environmental Protection Agency. (The six major air pollutants are: carbon monoxide, lead, nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds.)
NOx: How Nitrogen Oxides Affect the Way We Live and Breathe. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, September 1998.
http://www.epa.gov/air/urbanair/nox/index.html
While nitrogen dioxide levels in urban areas have fallen, national emissions of nitrogen oxides have increased by 4% over the past 20 years. This increase is the result of a number of factors, the largest being an increase in nitrogen oxides emissions from diesel-fueled vehicles.
National Air Quality Status and Trends 2000: Nitrogen Dioxide. U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, 2000.http://www.epa.gov/oar/aqtrnd00/nitrodox.html
Since 1970, emissions of nitrogen oxides from coal-fired power plants have increased 44 percent.
1997 National Air Quality: Status and Trends,Six Principal Pollutants-Nitrogen Dioxide (NO2). U.S. Environmental Protection Agency, Office of Air & Radiation, December 1998.http://www.epa.gov/oar/aqtrnd97/brochure/no2.html
Solutions
How to detect nitrogen oxides
- While NO2 has a pungent odor at high levels, its odor at levels just above normal levels is generally difficult to detect. However, indoor sources of NO2 often are accompanied by carbon monoxide, which can be detected with a carbon monoxide detector.
For information on carbon monoxide detectors, see Gas Appliances: How to Minimize Pollutants
How to minimize exposure to nitrogen oxides
- Always operate gas and kerosene appliances and wood stoves according to manufacturer specifications. Use the proper fuel in kerosene space heaters and never leave space heaters unattended.
- Keep gas appliances properly maintained and in repair. Have gas appliances, furnaces and chimneys inspected, cleaned and tuned at least once a year. Repair leaks promptly. Use the proper fuel in kerosene space heaters and never leave space heaters unattended. When appliances are kept in good working condition and operated correctly, they produce few combustion pollutants such as nitrogen dioxide.
If you suspect any of your appliances could be leaking pollutants, your local gas companies may perform inspection services.
- Always ventile well when using gas and kerosene appliances.
-Use an exhaust fan vented to outdoors every time you use a gas stove. The exhaust fan should be located above the stove. Note: In many cases, the fans in overhead stove hoods ARE NOT vented outdoors. Do not rely on these for ventilation. If you do not have an exhaust fan over your gas stove or the fan is not vented outdoors, always open a window while cooking.
-Open flues when fireplaces are in use.
- Make your home a smoke-free zone. Keep children away from secondhand smoke.
- Children should be kept from doing moderate to strenuous exercise outdoors when air pollution levels are high. Ozone tends to be highest in the summer. Many newspapers around the country report pollution levels. You can also check ozone levels by region at AirNOW, a U.S. Environmental Protection Agency website.
Children should also avoid exercising on playing fields near highways or other busy roads. Pollution levels can be high up to 50 feet from the roadway.
- If you suspect your home contains elevated levels of nitrogen dioxide, evacuate sensitive individuals such as young children, the elderly, and those with respiratory diseases such as asthma or emphysema. If you can identify the source (e.g., a gas engine), turn it off and get fresh air into the area by opening windows and doors and using a window fan to increase ventilation. Call your local gas utility or a heating contractor for a home inspection. Repair, replacement, or proper ventilation of the appliance can eliminate the problem, once the NO2 source is identified.
- Choose properly sized wood stoves that are certified to meet U.S. Environmental Protection Agency emission standards, and be sure doors on wood stoves fit tightly. Consider purchasing a vented space heater when replacing un-vented heaters. See How to Build a Safe Fire for information on fireplace safety.
- Never leave a car or lawnmower engine running in a garage, shed or other enclosed spaces. Even if the garage door to the outside is open, fumes can build up very quickly in the garage and living area of your home.
- Don’t use gasoline-powered appliances, engines or tools (mowers, weed trimmers, snow blowers, chain saws, small engines or generators) in enclosed or partly-enclosed spaces.
- Air purifiers will not remove gases from indoor air. Ozone generators convert NO2 into nitric acid, which also poses health risks.
Alternatives
- Using ovens and heating systems powered by electricity instead of fuels will reduce nitrogen dioxide emissions in the home; however, electric ovens are not as energy-efficient
as gas ovens. If you decide on gas appliances, choose appliances that vent their fumes to the outdoor whenever possible.
For More information
Books, articles, factsheets and reports
What You Should Know About Combustion Appliances and Indoor Air Pollution. U.S. Consumer Product Safety Commission, U.S. Environmental Protection Agency, and The American Lung Association, Updated March 15, 1999.
http://www.epa.gov/iaq/pubs/combust.html
What You Should Know About Space Heaters Used for Supplemental Room Heating. U.S. Consumer Product Safety Commission, February 2001.
http://www.cpsc.gov/CPSCPUB/PUBS/463.html
The Inside Story: A Guide to Indoor Air Quality. U.S. Consumer Product Safety Commission and the U.S. Environmental Protection Agency.
http://www.cpsc.gov/CPSCPUB/PUBS/450.html#Look4
Danger In The Air: The 2001 Ozone Season Summary. U.S. PIRG Education Fund, August 2002.
http://uspirg.org/uspirg.asp?id2=7727&id3=USPIRG&
State of the Air 2002. American Lung Association, May 2002.
http://www.lungusa.org/press/envir/air_050102.html
Other government agencies
U.S. Environmental Protection Agency - Office of Air and Radiation
Ariel Rios Building
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Indoor Air Quality Hotline: 800-438-4318
http://www.epa.gov/oar
Nonprofit organizations
American Lung Association
1740 Broadway
New York, NY 10019
212-315-8700
800-LUNGUSA
http://www.lungusa.org
Clean Air Trust
1625 K Street NW, #790
Washington DC 20006
202-785-9625
http://www.cleanairtrust.org
Other websites
Environmental Defense Chemical Scorecard
http://www.scorecard.org
Healthy Indoor Air for America’s Homes
http://www.montana.edu/wwwcxair/
