Why should the spraying of DDT as an insecticide on vegetable crops be banned?
Spraying of DDT as an insecticide should be banned for the following reasons:
(i) DDT is a non-biodegradable insecticide. The concentration of DDT is increased at successive trophic levels.
(ii) For example, if it starts at 0.003pph in water, it can ultimately reach 25 ppm (parts per million) in fish-eating birds. This phenomenon is known as biomagnification.
(iii) Biomagnification refers to the increase in concentration of the toxic substance at successive trophic levels.
(iv) High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking eventually responsible for decline in bird populations.