Nitrogen is a colorless, odorless, tasteless gaseous element that makes up approximately 78 percent of the earth's atmosphere by volume. It is also the seventh most abundant element in the solar system and the universe.
Nitrogen is found in all living organisms, primarily in proteins, amino acids, and nucleic acids (DNA and RNA). It is at the center of the nitrogen cycle, in which it is fixed by bacteria and converted into forms usable by plants.
Nitrogen for industrial use is obtained primarily through the distillation of liquified air. Applications for it and its compounds include the production of fertilizers, explosives, nitric acid, dyes, and nylon, as an inert atmosphere for electronics manufacturing and food preservation, and as a refrigerant in liquid form including for food freezing and cell preservation.
While nitrogen by itself is non-toxic, some nitrogen compounds can be harmful. Among them, nitrogen dioxide, the main source of which is internal combustion engine road vehicles, is associated with increased risk of lung cancer and heart disease.