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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. |
Organic pollution
The amount of organic compounds getting into the world ocean is approximately 300-380 million tons a year. Wastewaters containing dissolved organic chemicals or organic suspensions have a pernicious effect on the state of water reservoirs. By settling on the ground these chemicals prevent microorganisms whose natural function is to participate in the function of self-purification of water from their normal function or fully stop their vital functions. Decomposition of such organic chemical leads to the creation of detrimental compounds like hydrogen sulfide that pollute water in the whole reservoir. The presence of suspensions leads also to lower penetration of light into the water and, as a result, to worse process of photosynthesis. Detrimental effect is also produced by any organic chemicals that decrease the amount of oxygen in the water as hydrogen content is one of the major sanitary requirements for water. For example such chemicals may be such surface-active substances as oils, oil products, lubricants that form a thin layer on the surface of water and thus preventing normal gas exchange between the water and the atmosphere that leads to low hydrogen content.
A great amount of such organic compounds alien to natural waters is dumped into them together with other inorganic wastes from industrial and domestic drainage. The growing pollution of water reservoirs is a common thing in all industrial countries of the world. Especially noticeable such pollution is in water reservoirs with retarded flow or in stagnant waters.
