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 200,000 to 1.5 million. While megacities often receive support for improving air quality; similar

The air pollution is a growing problem in a number of cities around the world. Over the years, starting from the days of the infamous London smog and Los Angeles smog episodes, the cities around the world have established programs to better understand the air pollution sources and facilitated ways to control the pollution.

Over the past two decades the issue of air pollution in the
Kathmandu Valley has become of increasing concern as
concentrations of ambient air pollution exceed international
air quality guidelines and standards. The steady growth in
road traffic has resulted in the increasing contribution of
vehicle emissions to urban air pollution, especially particulate

Results of ambient air quality monitoring carried out during 2008 at various monitoring stations under National Air Quality Monitoring Programme by the CPCB.