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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. |
Heavy metals as water pollutants
High-density metals like mercury, lead, cadmium, Zink, copper, arsenic are one of the most widespread and very toxic pollutants on Earth. They are widely used in different industrial processes, that's why even though sewage treatment facilities have been built in many countries, the content of heavy metals in sewage waters is still comparatively high. A large amount of such compounds enters the ocean via atmosphere. For marine biosynthesis the most dangerous are mercury, lead an cadmium. Weathering of sediments and eruptive rocks every year leads to the release of about 3.5 thousands of tons of mercury. The atmospheric dust also contains about 12 thousands of tons of mercury, and a considerable part of it is of the anthropogenic origin. Around a half of the yearly industrial production of this metal gets into the ocean by various paths. The contamination of marine products with mercury has lead to repeated poisoning of the coastal population resulting in hundreds of lethal outcomes.
Lead is also a typical interspersed element that's contained by all elements of the environment: rocks, soils, natural waters, atmosphere, and living organisms. Besides, lead is actively dispersed into the environment in the process of the human activity. These pollutants get into waters with industrial and domestic sewage, smoke and dust from industrial plants, exhaust gases of internal combustion engines. Every year tens of tons of lead are accumulated in the oceans.
Arsenic contamination of deeper levels of groundwater is also a warning problem.
