ABSTRACT
An analysis of air quality shows the presence of numerous substances in trace amounts. Some of these substances can be explained in terms of either natural or anthropogenic (man-made) source activities. Others are formed indirectly from chemical processes in the atmosphere. The contribution of a source to air quality varies according to its emission characteristics and the emitted pollutant. The two types of air pollutants that can therefore be distinguished are either primary or secondary pollutants.
