by Katherine Bolt, Susmita Dasgupta, Kiran Pandey, and David Wheeler

About the authors: Katherine Bolt, Susmita Dasgupta, Kiran Pandey, and David Wheeler are members of the World Bank’s Environment Department and Development Research Group in Washington, D.C.

Polluted air is a major health hazard in many parts of the world, but it is particularly troublesome in some developing countries, where regulations governing air quality have traditionally been lax or nonexistent. The international health community currently believes suspended particulate matter—commonly known as dust—to be the most damaging among widely measured air pollutants. Ambient concentrations of particulates in many cities of the developing world routinely exceed the World Health Organization safety standard by a factor of three or more.

Particulate air pollution is a complex mixture of small...