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Occupational exposure limits are the maximum allowable concentrations of hazardous elements in the air. They are defined by scientific laboratories in order to control the level of pollution in different areas. Among the main atmosphere pollutants are large-scale industry, domestic boilers and transport. The portion of each of these pollutants is different from place to place, but industrial companies are considered to be the worst pollutants. The major sources of artificial aerosol pollution of the atmosphere are thermal power plants that burn a large amount of coal with high ash content, concentrating mills, metallurgical, cement, magnesite and soot plants. |
Scale of pollution
By it scale the pollution can be separated into local, regional and global. These three types of contamination are closely connected between each other. As a rule the primary one is the local pollution which turns into regional if the speed of pollution exceeds the speed of natural purification. In certain cases it can turn into a global problem for the environment. The time factor turns out to be the crucial one for global pollution.
The existence of such processes witnesses limited resources of the atmosphere as well as the limits of its natural self-recovery.
In the existing conditions of pollution the harmful substances can spread to tens and hundreds of kilometers from the source of pollution. And the notion of a source itself has somewhat changed its meaning. If in small industrial areas we can separate certain sources of pollution, in the scale of a region a whole industrial area, for example a big city can be considered one single source with a system of pointed, linear and group sources. Moreover, a whole region or even a whole country can be regarded as a single source of pollution.
The contemporary industrial production has a great influence on the nature on the global scale. Although the majority of pollutants and heat energy are produced on limited territories, mostly in industrialized areas of North America, Europe and Asia, as a result of circulation of atmosphere and shifts in the water layer of the Earth a considerable part of some of the long-living polluting factors is dispersed over vast territories around the globe.
