Nitrogen dioxide (NO2)

Nitrogen dioxide (NO2) is a highly reactive gas, and is representative of a group of other highly reactive gases known collectively as nitrogen oxides (NOx). These gases, especially nitrogen dioxide, are products of vehicle, power plant, and off-road equipment emissions caused by fuels burning at high heat.

Nitrogen dioxide, when prevalent in the air, appears as a reddish-brown haze. Nitrogen dioxide and other nitrogen oxides react with other chemicals in the air to form other pollutants, known as secondary pollutants. These secondary pollutants include ozone, particulate matter, acid rain, and other toxic chemicals. Visit the US EPA nitrogen dioxide web page for more information.

Health impacts of nitrogen dioxide (NO2)

On its own, nitrogen dioxide can cause lung irritation and diminish immune responses to respiratory infections. Individuals with pre-existing conditions, especially asthma, as well as young children and the elderly, are particularly susceptible. Exposure can cause coughing, wheezing, or difficulty breathing, and can send affected individuals to the hospital. Secondary pollutants formed with nitrogen dioxide — including ozone and particulate matter — also have negative health impacts.

For additional information about the health impacts of air pollution in Minnesota, you can check out our most recent air quality report, the Air we breathe, or visit the Be Air Aware website. You can sign up for air quality alerts and forecasts.

Air quality standards that help protect us from adverse effects of nitrogen dioxide (NO2)

The Clean Air Act regulates nitrogen dioxide as a criteria pollutant. The U.S. EPA sets National Ambient Air Quality Standards (NAAQS) for nitrogen dioxide, including both primary standards to protect public health and secondary standards to protect the environment.

In 2010 and 2012, the EPA reviewed the science related to the human health and environmental impacts of nitrogen dioxide, respectively, and revised the NAAQS to reflect the most up-to-date information. The primary standards for hourly nitrogen dioxide levels are currently 100 ppb and the annual standard is 53 ppb. The state of Minnesota is currently in compliance with the national standards for nitrogen dioxide.

To see the MPCA’s monitoring data for NO2 and other criteria pollutants, explore our Criteria Pollutant Data Explorer.