Epidemiological bases for ambient air quality criteria.

Epidemiological information about the health consequences of ambient air pollution is adequate at present to set upper limits so that acute deterioration due to pollution can be prevented in patients with chronic lung disease. However, our knowledge is incomplete with respect to what is a safe chronic background level, particularly with regard to reducing and preventing the amount of chronic respiratory disease presently occurring. This review concentrates exclusively on sulphur dioxide and particulate pollution, although the principles used in setting standards for these two pollutants may be applied to photochemical pollutants such as ozone which may effect the lung. It is only when the dose-effect relationships between pollution and disease are more clearly understood that the benefit of reducing air pollution to improve health can be predicted.