Nitrogen Dioxide 

What nitrogen dioxide is
Sources of nitrogen dioxide
Health problems associated with nitrogen dioxide
   Acute Effects
   High Exposures
   Long-term Exposure to lower levels
Decreasing exposure to nitrogen dioxide

What Nitrogen Dioxide Is 

Nitrogen dioxide (N0₂) is a colorless gas with a strong odor that is a common combustion pollutant. It is most often thought of as an outdoor air pollutant given off by motor vehicles and fossil-fuel burning power plants. It is used to produce other chemicals, as a nitrating and oxidizing agent in bleaching flour, and in rocket fuels and explosives. In the indoor environment it is often found as a result of inadequately vented gas ranges, gas pilot lights, gas or kerosene heaters, and welding activities, as well as tobacco smoke. Because nitrogen dioxide is a powerful respiratory irritant, it may aggravate asthma and other respiratory diseases.

Sources of Nitrogen Dioxide 

• Unvented or malfunctioning gas appliances such as gas stoves and gas clothes dryers. Those who live in a home with a gas stove are more than twice as likely to have respiratory symptoms than those who have electric stoves.¹

• Unvented or malfunctioning gas and oil furnaces

• Unvented kerosene heaters

• Wood or coal stoves

• Tobacco smoke

• Automobile exhaust, usually in attached garages

• Malfunctioning chimneys used for wood, gas, or oil exhaust

The level of nitrogen dioxide in homes without combustion appliances is about half that found outdoors. In homes with gas stoves, kerosene heaters, or unvented gas space heaters, indoor levels of nitrogen dioxide often exceed outdoor levels.

Health Problems Associated with  Nitrogen Dioxide

There is evidence that either high concentrations or continued exposure to low levels of nitrogen dioxide might increase the risk of respiratory infection. There is also evidence from animal studies that repeated exposures to elevated nitrogen dioxide levels might lead, or contribute, to the development of lung diseases such as emphysema and bronchitis.² Concentrations above 150 ppm can be deadly while concentrations in the range of 50ppm to 150 ppm can produce chronic (long-term) lung disease. The National Institute of Occupational Safety and Health (NIOSH) recommends that 1 ppm not be exceeded at any time.

People at particular risk from exposure to nitrogen dioxide include children and individuals with asthma and other respiratory diseases. Some studies have shown that children may have more colds and flu when exposed to low levels of nitrogen dioxide. When people with asthma breathe in low levels of nitrogen dioxide while exercising, their lung airways can narrow and react more to inhaled materials.

Health problems caused by nitrogen dioxide can either be acute, which occur immediately or within a few days of exposure, or they can be chronic, which are long-term health effects that might not show up for many years.

Acute Effects 

• Irritation of the eyes, nose, and respiratory tract

• Shortness of breath

Results of High Exposures 

• The development of acute or chronic bronchitis

• Pulmonary edema and diffuse lung injury, which may be fatal

Long-term Exposure to Lower Levels

• Increase the frequency of respiratory illness, often due to respiratory infections

• Lead to permanent lung damage resulting in chronic lung disease and respiratory illnesses such as bronchitis and emphysema²

Decreasing Exposure to Nitrogen Dioxide

• Use pilotless (electronic) ignition on gas appliances. These appliances are usually more energy efficient and eliminate the continuous low-level pollutants from pilot lights.

• Install and use an exhaust fan vented to outdoors over gas stoves. Remove and clean the metal mesh filters on your range hoods with detergent when they begin to look grimy (most can be put in the dishwasher). "Ductless" range hoods are not effective because they exhaust into the house rather than outside; add a duct or replace the hood with one vented to the outside (ducted).

• Choose vented appliances whenever possible.

• Before considering using an unvented space heater, check with your local and state building codes and fire ordinances. These types of unvented heaters are not allowed to be used in some communities, dwellings, or certain rooms in the house.

• Choose appliances, such as gas dryers, that vent their fumes to the outside. Have them properly installed and maintain according to the manufacturer's instructions.

• Never disconnect vents on combustion appliances, even if it seems like a way to get extra heat in the winter.

• Never use a gas range for home heating.

• Keep tobacco smoke out of your home and away from open doors or windows. Environmental tobacco smoke can increase the chance of lung cancer in nonsmokers. Children, pregnant women, or persons with lung or heart disease are especially sensitive to smoke.

• Never idle the car in a garage even if the garage door to the outside is open. Exhaust vapors can build up very quickly in the garage and living area of your home.

• Have a trained professional inspect your fuel-burning appliances including oil and gas furnaces, gas water heaters, gas ranges and ovens, gas dryers, gas or kerosene space heaters, fireplaces, and wood stoves at the beginning of every heating season. The central heating system (furnaces, flues, and chimneys) should also be inspected, cleaned, and tuned-up annually.

• Install combustion appliances away from the home's living area (such as living room and bedrooms).

• Supply adequate outdoor make-up air for combustion so there will not be backdrafting into the indoor environment.

• Inspect and clean flues and chimneys regularly to make sure they are in good condition and not blocked.

• Use proper fuel in kerosene space heaters. Only use water-clear ASTM 1-K kerosene for kerosene heaters, otherwise you could have even more pollutants get in your home. Never use gasoline in a kerosene heater because it can cause a fire or an explosion. Using even small amounts of gasoline could cause a fire.

• Open flues when fireplaces are in use.

• If you choose to use a wood stove, make sure they are the right size and that they are certified to meet EPA emission standards. Make certain that doors on all wood stoves fit tightly.

• Use an air cleaner to help in removing particulates from the air.

• If your household has young children or someone with allergies or lung disease, consider using a high-efficiency air cleaner in your forced-air heating system or add a stand-alone unit. Some stand-alone air cleaners (HEPA or electrostatic types) can remove particles in a single room. Small desktop air cleaners generally are not effective.

References

1. Garrett, M.H.; Hooper, M.A.; Hooper, B.M.; and Abramson, M.J. (1998). Respiratory symptoms in children and indoor exposure to nitrogen dioxide and gas stoves. American Journal Respiratory and Critical Care Medicine; 158: pp 891-895.

2. OSHA. Chemical sampling information: nitrogen dioxide. Occupational Safety and Health Administration. Revised February 18, 2000: www.osha-slc.gov/dts/chemicalsampling/data/CH_257400.html.