Industry and a yellow sky background

Nitrogen oxides (NOx) are a collective term for toxic gas molecules that are chemical compounds between nitrogen and oxygen and are an essential component of air pollution.

Nitric oxide (NOx)

Nitrogen oxides (NOx) are a common term for the nitrogen oxides N2O, NO, N2O3, NO2 and NO3 and are a chemical compound of oxygen and nitrogen that is formed during the combustion of fuel and organic material at high temperatures. NOx emissions in Norway come mainly from energy production from oil and gas, land-based industry, road traffic and shipping.

NOx may:

  • react with ammonium (NH4 +), water vapor and other compounds to form nitric acid (HNO3). Inhalation of nitric acid vapor is toxic and can lead to catarrh of the bronchi, pneumonia and etching of the alveoli.
  • react with volatile organic compounds in the presence of sunlight and form ground-level ozone which damages vegetation by reacting with unsaturated fats in cell membranes, and can give rise to hydrogen peroxide which causes oxidative stress.
  • contribute to acid rain with a lower pH than 5.6. Acid rain has the greatest consequences for aquatic organism, forests ecosystems and buildings. An example is fish deaths due to disturbances in the water and ion balance and respiratory failure.
  • form smog or yellow cloud that covers larger cities and provides poor air quality. NOx can cause serious damage to human health, including asthma and respiratory infections.

According to the Norwegian Institute of Public Health in 2019, more than 4 million deaths globally were caused by pollution of particulate matter, nitrogen dioxide and ozone.