Introduction

This chapter considers only air pollution of anthropogenic origin, since natural pollution events tend to be localized and relatively unimportant over the timescale covered. Indoor pollution can be traced back to the early use of fire for cooking and heating, and became an increasing problem as large-scale settlements developed. In present-day developing countries, the percentage of households burning solid fuels indoors ranges from 16% in Latin America and the Caribbean up to 77% in Africa. Man-made outdoor air pollution, on the other hand, only began to be a significant health issue with the Industrial Revolution in the eighteenth century.

Primary pollutants such as carbon monoxide or sulfur dioxide are released directly from engines or processes; ozone and particulate matter are among secondary pollutants formed by the reaction of primary pollutants. Polluted air can have direct impacts (on health, materials, and ecosystems) or less direct ones such as the formation of “acid rain” from sulfur dioxide, or population relocation. The major indirect effect of air pollution is the warming of the Earth’s atmosphere by greenhouse gases emitted when fossil fuels are burned. This is included in another chapter in this Copenhagen Consensus project.