The production of synthetic organic compounds is increasing year by year. They include plastics, fibers, detergents, paints, pesticides, fungicides, weedicides insecticides, dyes and pharmaceuticals. Their presence in water imparts colour and offensive odour. The domestic waste and industrial waste coming from sugar cane, paper, leather, and pulp industries degrade in the presence of microorganisms affects the aquatic life (both animals and plants). In our country, where agriculture is the main occupation, indiscriminate usage of the pesticides has resulted in water pollution as well as development of resistance among the pests for these pesticides. So, there is a constant need to develop new varieties of insecticides and pesticides.
Some common examples are: Malathion, DDT, carboryl, chloro phenoxy group of compounds, compounds of dithio carbamate group and phenyl mercury acetate etc.
Though, the above substances are very useful in controlling the pests and thus help in increasing the crop yields, they are present both in animals and also in soil for a considerable time in unchanged conditions which is undesirable for the existence of animals and human beings. Some of the above substances mix with water and are consumed by the fish, and other aquatic life. Other animals like birds, which are then consumed by human beings, eat these. The concentration of these substances goes on increasing by the time reach the human beings. The carriers of these substances (plants - fish -animals and bird etc.) are called as "food chains" and the process of increase of concentration of these substances as we go from lower animals to higher animals and human beings is called as "bio amplification". In the human body, they remain unchanged for quite sometime. Thus, it results in high B.P. and increase in irritation levels of human beings. The bioamplification can be represented pictorially as follows