ABSTRACT
The unrelenting pollution of the atmosphere by modern society is at the root of several global environmental issues. The emission of pollutants into the atmosphere is one of the oldest human activities, and the present problems are only the most recent in a lengthy continuum. Issues such as acid rain, increased atmospheric turbidity and the depletion of the ozone layer, include essentially the same processes which led to the urban air pollution episodes of a decade or two ago. The main difference is one of scale. The previous problems had a local, or at most, a regional impact. The current issues are global in scope, and therefore potentially more threatening.
