ABSTRACT
Air pollutants are substances which, when present in the atmosphere under certain conditions, may become injurious to human, animal, plant or microbial life, or to property, or which may interfere with the use and enjoyment of life or property. This definition stresses the effects upon receptors, and includes modif icat ion due to both natural and anthropogenic sources. In the context of this book we will emphasize the physical factors leading to a more or less polluted atmosphere at a location rather than the effects evoked after receipt, and we will be concerned mainly with pollutants generated by human activities rather than by natural events.
