Air pollution levels in the megacities of Asia show a stabilizing trend but still exceed World Health Organization guidelines. Studies also show poor air quality, not only in the megacities of Asia, but also in smaller cities with populations of 150,000 to 1.5 million. While megacities often receive support for improving air quality; similar assistance seldom reaches smaller cities. Responding to the need to strengthen air quality management in smaller cities, the Association of Southeast Asian Nations (ASEAN)