Nitrogen dioxide in air

Nitrogen dioxide is known to affect the throat and the lungs. In levels encountered in polluted air, people with respiratory problems, particularly infants, children and the elderly, may be affected. People with asthma are often sensitive to nitrogen dioxide.

Sources of nitrogen dioxide

The main source of oxides of nitrogen in the urban atmosphere is the combustion of fossil fuels (petrol, diesel, coal, gas). Oxides of nitrogen can be in two forms - nitric oxide, which is not harmful to human health, and nitrogen dioxide, which is harmful. Nitrogen dioxide may be emitted directly, but it is also formed in the atmosphere from nitric oxide.

Current standards for nitrogen dioxide

The current standard for nitrogen dioxide is 0.12 ppm (parts per million) for one hour and 0.03 ppm for one year.

Goal for nitrogen dioxide

The one-hour standard should not be exceeded more than once (one day) per year. The one-year standard should not be exceeded.

Nitrogen dioxide air quality categories

The nitrogen dioxide (NO2) data on our website will be shown in different colours, depending on the amount of NO2 in the air. The categories range from green – when levels of NO2 are low and air quality is very good – through to black – when high levels of NO2 result in very poor air quality.

Air quality category NO2 ppb
Very good 0–39
Good 40–78
Fair 79–119
Poor 120–179
Very poor 180 or greater

Page last updated on 12 Sep 2017