Biomagnification is referred to any random concentration of a toxin, such as pesticides like DDT, beta-hexachlorocyclohexane (BHC), copper sulphate, and aldrin or heavy metals in the tissue of tolerant organisms at successively higher levels in a food chain. In the fat-containing tissues of the organism, these pollutants generally accumulate. If we take an example of DDT in the aquatic food chain, the concentration of DDT is increased at successive trophic level starting from 0.003 parts per billion in water it can ultimately reach 25 parts per million in fish-eating birds (present after four trophic level) due to the effect of biomagnification. There is a disturbance in the calcium metabolism in the birds due to a high concentration of DDT and this may lead to thinning of the eggshell and their premature breaking eventually causing a decline in the bird populations. Minamata disease is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, and damage to hearing and speech.