3. What are nitrogen oxides and why are these gases a concern?

Nitrogen oxides are a group of gases made up of oxygen and nitrogen atoms. The most common forms are nitrogen dioxide (one nitrogen and two oxygen) and nitric oxide (one nitrogen and one oxygen).

Nitrogen oxides are formed when carbon based fuels (oil, gas, coal, biomass) are burned at high temperatures. Today automobiles (the internal combustion engine) are one of the most common sources of nitrogen oxides.

Nitrogen oxides are also produced when the organic nitrogen in sewage and livestock wastes naturally decompose (EPA).

Nitrogen oxides can dissolve in water vapour in the air to form acids. This is a source of acid rain. Nitrogen oxides also contribute to particles that form in the air – more commonly known as “smog”. NO2 is one of the primary contributors to the formation of ozone at ground level, which causes respiratory problems (Environment Canada).

Nitrous oxide is also a harmful greenhouse gas. Although the concentration of nitrous oxide in the atmosphere is considerably lower than that of carbon dioxide, the global warming potential of nitrous oxide is over 300 times greater.