Photochemical smog

Photochemical smog is the term to represent a multitude of chemical agents which are considered to be detrimental to the environment and health. They are called photochemical smog because they are produced by the photolysis of primary pollutants. Photochemical smog includes the following:

• Nitrogen Oxides, such as Nitrogen Dioxide
• Tropospheric Ozone
• Volatile Organic Compounds (VOCs)
• Peroxyacetyl Nitrates (PAN)

All of these are usually highly reactive and/or oxidising, and so photochemical smog is considered to be a problem of modern industrialization.