Background on Air Pollution System
An atmospheric condition in which substances exist at concentrations higher than the normal background or ambient level is said to be polluted if it has measurable effects on humans, animals, flora or materials. To understand the origin of the problem and take ultimate action we have to define a system to follow. An air pollution system in the form of a block diagram is presented in figure 1. It starts with the emission source, which might be a coal-burning power station. The source control might be flue gas scrubbers prior to emission. The detectors might be continuous monitors for SO2. The receptors might be a biological indicator, i.e. lichens. When the detector or receptor shows unacceptable emissions, an automatic control response might result, i.e. reduce the emission rate. An unacceptable emission may be pursued by legislation, forcing modifications to emission or source control. The proposed national action plan on air pollution is based on the principles outlined in this system.