Write a note on the effect of various pesticides on living things.

(N/A) Prior to World War $II$,many naturally occurring chemicals such as nicotine were used as pest-controlling substances for major crops in agricultural practices.
During World War $II$,$DDT$ was found to be of great use in the control of malaria and other insect-borne diseases.
Thus,after the war,$DDT$ was put to use in agriculture to control the damages caused by insects,rodents,weeds,and various crop diseases.
Therefore,as insect resistance to $DDT$ increased,other organic toxins such as Aldrin and Dieldrin were introduced in the market by the pesticide industry.
Most of the organic toxins are water-insoluble and non-biodegradable. These highly persistent toxins are,therefore,transferred from lower trophic levels to higher trophic levels through the food chain.
Over time,the concentration of toxins in higher animals reaches a level which causes serious metabolic and physiological disorders.
Organo-phosphates and carbamates are serious nerve toxins. As a result,such insecticides are responsible for the death of laborers working on the farm.