“Efforts by Tehran officials to boost public transport, including extending the subway lines and establishing lanes for buses only, have barely dented the problem because of the ever-growing number of cars, many of which are inefficient and old. Western sanctions on fuel imports to Iran have also forced the country to rely on its own production of petrol — of a lower grade, and therefore more polluting, than in many other countries.”
http://www.rawstory.com/rs/2012/12/05/tehran-residents-urged-to-flee-dangerous-pollution/
