Abhijit Deb

Biomagnification is the amplification of levels of pollutants as we move up the trophic levels of the food chain. Pollutants which cannot be broken down and hence cannot be excreted by organisms are ingested by smaller organisms, these organisms are then consumed by slightly bigger organism above the food chain and so on. The accumulation increases as we go up the chain because of the increasing persistence of the pollutants and higher energy requirements at higher levels. The main two categories of pollutants are: a. Persistent organic pollutants (POPs), which are novel organic materials like DDT, Hexachlorobenzene etc b. Pure metals like Mercury. The case of Minamata disease is a perfect example of biomagnification, the mercury in the industrial wastes are consumed by small fishes, a large no of small fishes are consumed by an individual big fish and then the particular fish is consumed by a bird or humans.

Minamata disease is a neurological syndrome caused by mercury poisoning. The main causal agent is Methylmercury chloride. The symptoms are: Loss of peripheral vision Muscle weakness Numbness in hands and feet Damage of hearing and speech In extreme cases, insanity, paralysis, coma or even death is possible. This disease was first discovered in a small fishing village of Japan called Minamata and hence the nomenclature. It is one of the most biggest pollution disease of Japan. The Chisso corporation is held responsible for outbreak of this disease. They dumped inorganic mercury into the ocean which the related with the water to form organic mercury. The toxic waste discharged into the water, consumed by fish, then found itself by nutrition into the human body. Photographic trivia: The prolific American photo journalist W Eugene Smith documented this disease and his photo essay brought attention of the world to this disease.