Nitrogen dioxide (NO2) is one gas in a group of highly reactive gases known as nitrogen oxides (NOx) and it is used as the indicator for the whole group.
Breathing air with a high concentration of NO2 irritates airways in the human respiratory system. Short-term exposures can lead to symptoms like coughing, wheezing and heavy breathing. Longer exposures may contribute to the development of asthma and potentially increase susceptibility to respiratory infections.
The health effects of NO2 are especially emphasized in people with asthma, as well as children and the elderly.