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Thermal Pollution :
Thermal pollution is caused by the release of hot water into nearby lake/ponds.
Enormous amount of cool water is required for the cooling of condensers in
steam-electrically heated thermal plant. Cool water is thereby heated and when
released increase the temperature of the surface water lake/pond. While some
of the marine life like fish can survive or even promote its growth within certain
limits, while other may die.
Pesticides :
Pesticides are used to kill/destroy some organisms like insecticides, herbicides,
rodenticides and fungicides that are considered to hindrance to human lives.
For example, when malaria became epidemic through mosquitos, DDT or
dichlorodiphenyltrichroethane, was used to kill mosquitos and save human lives
from the deadly disease like malaria. When it was proved though DDT helps in
removing malaria it affects food chain of human and it was banned ultimately.
Synthetic organic insecticides are of three types : Organochlorines,
organophosphates and carbamates.
Other than DDT other organochlorines are methoxychlor, chlordane, heptachlor,
asdrin, dieldrin, endrin, ensosulphur and kepone.
Oxygenophosphates like parathion, malathion, diasion, TEPP (tetraethyl
pyrophosphate) and dimethoate are effective against wide range of insects and
are not persistent like DDT to effect the food chain. However, they are very toxic
and must be carefully handled to avoid skin rash, tendency of vomiting and
convulsion if inhaled.
Volatile Organic Compounds (VOC) :
Volatile organic compounds or VOCs are used for industrial uses or even for
domestic uses like detergents and because of its volatility, may be found in
traces in surface water, but while flowing underground their concentration may
increase many times and may be very harmful as they are suspected to
carcinogens or mutagens.
