Skip to Content Skip to footer
To see content specific to your location, return to the country or region that matches your location.

Nitrogen Dioxide Risks and Solutions

Semi truck on the road.

Nitrogen dioxide is a common pollutant found within the air we breathe. This pollutant can be sourced from appliances to the cars we drive, making it common both indoor and outdoor. Nitrogen dioxide can have various affects on both human health and the environment, depending on levels of concentration or exposure. While outdoor nitrogen dioxide is more difficult to control, indoor nitrogen dioxide can be managed.

What is Nitrogen Dioxide?

Nitrogen dioxide or “NO2” is part of a group of highly reactive gases known as nitrogen oxides or “NOx”. When cooled or compressed, NO2 appears as a reddish-brown gas or yellowish-brown liquid.

Health Effects of Nitrogen Dioxide

Depending on your level of exposure, nitrogen dioxide may cause various health effects. Below are some of the potential effects that NO2 may have:

  • Inflammation of the airways
  • Irritation of the eyes, nose throat and respiratory tract
  • Cough or wheezing
  • Reduced lung function
  • Difficulty breathing
  • Aggravation of respiratory diseases such as asthma
  • High levels of nitrogen dioxide may be life threatening

Who is Most at Risk from Nitrogen Dioxide?

As it is found within the air we breathe, everyone has some level of risk from exposure to nitrogen dioxide. Some groups of people are more sensitive or experience higher levels of exposure to nitrogen dioxide, putting them at higher risk to its effects. Those at higher risk from NO2 exposure include the following:

  • Children and elderly are both at higher risk as children’s lungs are still developing and elderly are more likely to have pre-existing conditions. Children also tend to spend more time outdoors where levels of NO2 are higher.
  • People with asthma already experience irritation and symptoms involving the respiratory system. Exposure to NO2 may worsen or exaggerate the symptoms of asthma.
  • Tobacco smokers or those exposed to tobacco smoke are at higher risk due to the nitrogen dioxide within tobacco smoke.
  • Anyone who owns heating and cooking appliances that emit some level of NO2 by using fossil fuels are exposed to its emissions.
  • Those who live near or work at coal-fired power plants. Outside access points, such as doors or windows, may allow NO2 in the air from the nearby power plants indoors. Those who work within the power plants may be exposed to NO2 while working.

What Are the Sources of Nitrogen Dioxide?

Nitrogen dioxide is sourced both indoors and outdoors. These sources include the following:

  • Burning fossil fuels such as coal, oil, gas or diesel at high temperatures
  • Emissions from cars trucks and buses
  • Power plants, diesel-powered equipment and moveable engines
  • Industrial boilers
  • Unvented appliances
  • Kerosene or gas space heaters, and gas stoves
  • Tobacco smoke

How Can I Prevent or Reduce Exposure to Nitrogen Dioxide?

As mentioned previously, nitrogen dioxide may be emitted from sources both indoor and outdoor. We’ve broken down the tips on preventing or reducing exposure to NO2 by outdoor and indoor exposures.

Indoor Nitrogen Dioxide Exposure

  • Ensure gas appliances are properly adjusted and use exhaust fans vented to the outdoors.
  • Make sure to use the proper fuel in kerosene space heaters.
  • Purchase vented space heaters over unvented ones.
  • Open flues when fireplace or wood burning stoves are in use.
  • Have a trained professional inspect, clean and tune-up central heating systems annually.
  • Do not idle or run vehicles within the garage, especially in an attached garage. Doors from attached garages will allow pollutants into the home.
  • Live further from any power plants or locations that use sources of NO2 like diesel-powered equipment and moveable engines.
  • Avoid smoking tobacco, or at least avoid smoking tobacco indoors where it may linger afterwards.
  • Utilize indoor air cleaners, such as air purifiers with HEPA filters, that help reduce airborne pollutants within the home.


Outdoor Nitrogen Dioxide Exposure

  • Staying indoors, especially when pollution levels are high. “Average level in homes without combustion appliances is about half that of outdoors.” (Environmental Protection Agency, EPA)
  • Reduce the use of motorized vehicles by walking, biking, or using other means of transportation for close destinations. Utilize carpools with others for locations where motorized vehicles are necessary.


Environmental Effects of Nitrogen Dioxide

Nitrogen dioxide also plays a role in the environment that we live in, by contributing to harmful factors on it including:

  • Acid rain: Acid rain occurs when sulfur dioxide (SO2) and nitrogen oxides (NOx) are emitted into the atmosphere and transported by wind and air currents. Acid rain has many effects, including harm to sensitive ecosystems such as lakes and forests.
  • Visibility and Haze: Nitrate particles that result from NOx contribute to the visibility and haze that makes it difficult to see in outdoor environments.
  • Nutrient pollution: Nutrient pollution is causes by excess nitrogen and phosphorus in the air and water. Nitrogen and phosphorus support the growth of algae and aquatic plants which in turn provide solutions for an entire ecosystem. However, when there is too much nitrogen and phosphorus, the air and water become polluted.


Nitrogen affects both human health and the environment, making it important to take steps to avoid or reduce it. Those at a higher risk should continually maintain awareness of their levels of exposure to NO2.  While preventing or reducing levels of nitrogen dioxide outdoors is more challenging, there are steps you can take to prevent or reduce indoor nitrogen dioxide within your home.