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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. |
Pesticides as water pollutants
Pesticides are a group of chemicals created exclusively for fighting with pests and various diseases of plants. They are divided into insecticides (substances designed to fight with insects), fungicides and bactericides (to fight with bacterial diseases of plants) and herbicides designed to fight weeds. It's been proven that by fighting harmful pests and diseases such pesticides also kill a wide range of useful microorganisms and do a great harm for biogenesis. There have been a lot of disputes about the necessity of transition from harmful chemical pesticides to organic and ecological methods of fighting with vermin. The process of such transition is very slow due to the incapability of large chemical companies to switch from production of harmful elements to the production of ecologically harmless substances – the whole technologically processes should be changed and this requires billions of dollars. Besides, such ecological substances and methods may appear less efficient in killing vermin and harmful microorganisms.
Moreover, industrial production of pesticides is as a rule accompanied with creation of a large number of harmful by-products polluting the drainage waters. Examples of insecticides, herbicides and fungicides are most often seen in aquatic environment. For instance, half-life of DDT and its derivatives can reach tens of years and they can be very resistant to biodegradation. Polychlorbiphenyl, a derivative of DDT is another harmful compound.
