Volatile organic compounds (VOCs), surface ozone and nitrogen oxides are the main components of the chemical haze or smog [local] found in many metropolitan cities. Smog is generated by fossil fuel burning automobiles. Photochemical smog is a mixture of pollutants which includes particulates, nitrogen oxides, ozone, aldehydes, peroxyacetyl nitrate(PAN), and unreacted hydrocarbons, etc.

Smog levels in certain parts of the U.S. have continued to rise [local]. The Canadian Council of Ministers of the Environment has published suggestions [local] for reducing smog.

An estimated 1,600 people die prematurely each year in southern California due to smog. Thousands of others suffer temporary or long-term health effects. Millions are inconvenienced Health Effects of Southland Smog [local].