Air pollutants
Nitrogen dioxide (NO2)
What is nitrogen dioxide?
Nitrogen dioxide (NO2) is a reddish, brown, pungent, acidic, gas that is formed by combustion of fossil fuels. Atmospheric nitrogen and any nitrogen in fuel is converted into its oxides, mainly nitric oxide (NO) and NO2 during combustion. The NO oxidises to form NO2 in the atmosphere.
What are the sources and contributors of NO2?
The main source of NO2 is from the combustion of fossil fuels (coal, oil and gas). In urban areas, most ambient NO2 comes from motor vehicles. Other sources include combustion of natural gas, refining of petrol and metals, commercial manufacturing and food manufacturing. Electricity generation using fossil fuels can also produce significant amounts of NO2.
What are the effects of nitrogen dioxide?
NO2 can irritate the lungs, increase susceptibility and severity of asthma and lowers resistance to infections such as the flu. Children exposed to NO2 are at increased risk of respiratory infection.
Nitrogen oxides are critical components of photochemical smog - it is nitrogen dioxide that produces the yellowish brown colour of the smog and significantly affects visibility.
Standards/guidelines for nitrogen dioxide
The NO2 air quality target for Auckland is 200µg/m3 for a one-hour average and 100µg/m3 for a 24-hour average.
View NO2 trends around Auckland.
Sources of nitrogen oxygen in the Auckland region
