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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. |
Synthetic surface-active substances
Synthetic surface-active substances refer to an extensive group of substances that decrease the surface tension of water. They are included as part of synthetic cleaning agents widely used in everyday life by almost every household on earth, as well as by industrial companies. Together with drainage waters such substances get into the oceans and marine environment. Synthetic cleaning agents contain sodium polyphosphates in which some detergents and additional ingredients are dissolved (like flavoring agents, bleaching reagents, soda ash, carboxymethylcellulose, sodium silicates) that are toxic for aquatic organisms. Depending on the nature and structure of molecules the synthetic surface-active substances are divided into different groups. The most widespread synthetic surface-active substances are anionic substances. They amount about to 50% of the general amount of such substances produced in the world. The presence of synthetic surface-active substances in industrial drainage waters is connected with their usage in such processes as polymer production, improvement of drilling of oil and gas wells, struggle with corrosion of equipment. In agriculture synthetic surface-active substances are used as part of pesticides.
The need to reduce the amount of synthetic surface-active substances is a much more controversial issue than the need to replace harmful chemical pesticides by organic and ecological chemicals as there are practically no alternatives to such surface-active substances able to perform all their functions.
