To protect the food plants from insects, an insecticide was sprayed in small amounts but it was detected in high concentration in human beings. How did it happen?
The insecticide that has been mentioned in the question is DDT, a non-biodegradable substance which accumulates in the body of consumers or human beings through food chain. This phenomenon is called Bio-magnification. These kind of insecticides/pesticides are sprayed to protect the plant from insects and pests. But they eventually enter our body through food chain and cause serious health problems. The range of accumulation is different in different trophic levels. It is detected in higher concentration at the top consumer level which include Humans.