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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. |
Oil as one of the major water pollutants
Oil and oil products are one of the most widespread agents of water pollution in the oceans. At the beginning of the 80's around 6 million tons of oil was dumped into water (which is around 0.23% of the whole amount being produced on earth). Mostly such tremendous quantity of oil was connected with its transportation from the areas where it was extracted. Regular accidents and constant drainage of wash waters by tankers created certain paths of regular oil pollution from the areas of extraction to the place where the oil was delivered. For the last 30 years more than 2000 underwater wells have been drilled. Due to insignificant drainage about 0.1 million tons of oil gets into the ocean every year. Large amounts of oil are also carried into the ocean together with industrial and domestic flows.
The general amount of oil polluting the world ocean every year is about 2.0 million tons with half of a ton produced by industrial drainage. Getting into the water oil doesn't dissolve in it but spreads to tremendous areas and has certain thickness which can be defined by the color of the oil layer. For example, a film of 30-40 micrometer fully absorbs infrared rays and prevents water organisms from the reaction of photosynthesis. By mixing with water oil can create emulsions of two types: oil in water and water in oil. The first type is characteristic for oils containing surface active agents. After the removal of volatile fractions the oil creates viscous emulsions that can remain on the surface for a long time.
