Clean air is considered to be a basic requirement for human health and their well- being. Air pollution has become an alarming problem with industrialization, and protection of air quality turned into a topic of great interest since early 1960’s. The United Nations Conference on Environment and Development (UNCED) held in 1992 at Rio de Janeiro, Brazil, adopted the Framework Climate Convention (Agenda 21) which underlined the need of air pollution control. Also, the declaration of Habitat II (United Nations Conference on Human Settlements held in June 1996, at Istanbul, Turkey) emphasized the “sustainable development” and “sustainable human settlements” for the protection of environment. In sustainable human settlements clean air was one of the most important considerations put forward among the other environmental issues
