More than half of the world’s population live in urban areas in Asia. Urban air pollution in most Asian Megacities (with a population of more than ten million) such as Beijing, Delhi and Jakarta has worsened due to the cumulative effects of population growth, industrialisation and increased vehicle use. The Air Pollution in the Megacities of Asia (APMA) project was initiated in November 2000 by the United Nations Environment Programme (UNEP) and the World Health Organization (WHO) in collaboration with the Korea Environment Institute (KEI) and the Stockholm Environment Institute (SEI). It is part of a programme on Regional Air Pollution in Developing Countries (RAPIDC)funded by the Infrastructure and Economic Cooperation division (INEC) of Sida(the Swedish International Development Co-operation Agency).