Organic phosphates and chlorinated hydrocarbons have the same basic structure with carbon and hydrogen. Chlorinated hydrocarbons have chlorine as an added element. Organic phosphates have the hydrocarbon chain and phosphate group. Chlorinated hydrocarbons are less toxic then organic phosphates.
Both are used as insecticides . However they are difficult to remove from the environment as they do not degrade which creates problems. Organic phosphates like parathion and Malathion are effective on insects like aphids and mites.Organophosphates can form flammable phosphine gas in the presence of reducing agents or can be oxidised to release phosphorus oxides. (Cameo chemicals 2008) Chlorinated hydrocarbons include DDT, heptachlor and mirex.
Organic phosphates are present in the soil whereas chlorinated hydrocarbons are rare but may present in some processes in the human body. Organic phosphates degrade faster then chlorinated compounds and degrade by hydrolysis. This quicker degradation makes them a better alternative . They act by attaching to enzyme acetyl cholinesterase.Four methods of pest control are: Insect control can be done by spraying, natural predators and using biotic controls.
Spraying can be done by hand pumps or through the air where it is more expensive as helicopters or aeroplanes are required. Natural predators are a safer method of pest control as no chemicals are introduced and it can be more selective. Here a natural predator of a pest is introduced to keep the pest numbers in control. This results in a more selective removal of the pest and prevents damage to the environment. Another method of sterilisation of the male insect population would be difficult to achieve.Carson also proposed controlling pests by using the insects which they feed on as a poison.
Some insects accumulate substances in their bodies making them poisonous. However this poison is naturally occurring in their body and would kill the pest when they consumed the insect. Five examples of how pesticides were harmful to the environment are: DDT was used as an insecticide but accumulated in the lakes and rivers where it entered the food chain through fish.This resulted in a decline in the bird population who ate the fish as it accumulated in their bodies and was lethal. Carson, R.
1972) However the use of DDT against malaria by spraying it over lakes where the mosquito cannot access and larvae die has been an important step in the fight against the disease and as a result banning the use of DDT can lead to other problems. However other alternatives to DDT can be used such as oil which prevents oxygen from reaching the larvae in the ponds. Chloroform was used as an anaesthetic agent but since the advent of safer anaesthetics its use declined and it is used as a solvent and refrigerant.It has been implicated tube a carcinogen. Carbon tetrachloride is used in manufacturing plants but exposure to this can be toxic to humans and cause liver and kidney damage. When released into the atmosphere it can form toxic free radicals that damage the ozone.
(ATSDR. 2005) This damage to the ozone has resulted in an increase in radiation like UVB penetrating the atmosphere and has caused an increase in skin cancer in geographic areas where ozone depletion has occurred like Australia.Organic phosphates have been used in World War 2 as nerve gas . Examples includes DFP and VX nerve agent. This acts through inhibiting enzymes and makes it difficult for normal body processes like respiration to occur.
In the 1970’s much of the awareness regarding chlorinated hydrocarbons was created resulting in a ban on their use in many countries and also an interest in alternatives. Organic phosphates have been seen to be a suitable alternative as are other methods of pest control without the use of insecticide.
