Role of motor-vehicles and trend of air borne particulate in the Great Tehran area, Iran.

Tehran, the capital city of Iran, is one of the largest cities in the world. It extends over an area of approximately 2,300 square kilometers and has a population of more than 10 million people. The city is suffering from atmospheric pollution arising from the rapid urbanization during the last 3 to 4 decades. The city will develop towards the west to Karaj, and large volumes of traffic will be going east-west by the year 2015. With more than 2 million vehicles in Tehran, most of which are more than 20 years old, traffic is the major source of air pollution in Tehran. The city of Tehran has a significant air pollution problem and suspended particulate matter (SPM) appears to rank high on the list pollutants. The monthly average of PM-10 in Tehran is high in autumn and low in spring. Maximum average value observed in September is over 370 microg/m(3); the minimum in March (102 microg/m(3)) and early April (65 microg/m(3)). The diurnal variation PM-10 concentration have been studied.