Action to improve air quality, and in this way to improve people's health, starts by recognizing the pollutants and pollution sources that contribute most to population exposure. The foundation for improving public health here is laid by risk assessment of air pollution and by legislation based on relevant scientific information. Internationally, there is substantial cooperation on activities related to ambient air quality, and several important agreements are gradually being implemented.
The Geneva Convention on Long-range Transboundary Air Pollution (1979) defines "air pollution" to mean, the introduction by man, directly or indirectly, of substances or energy into the air resulting in deleterious effects of such a nature as to endanger human health, harm living resources and ecosystems and material property and impair or interfere with amenities and other legitimate uses of the environment, and "air pollutants" shall be construed accordingly.