Minamata Disease

Minamata disease 

• A crippling deformity caused by methylmercury poisoning that was first described in the inhabitants of Minamata Bay, Japan in 1956.
• Results from eating fish contaminated with mercury industrial waste.
• Signs and symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech. 
• In extreme cases, insanity, paralysis, coma, and death follow within weeks of the onset of symptoms. 
• A congenital form of the disease can also affect fetuses in the womb.

How does Mercury enter the  Food Chain ?

• Atmospheric mercury dissolved in freshwater and seawater.
• A type of mercury called methylmercury is most easily accumulated in the body and dangerous.
• Organic mercury in a human body comes from eating fish and shellfish, and 75 to 90 percent of organic mercury existing in fish and shellfish is methylmercury,
• Inorganic mercury and methylmercury are first consumed by phytoplankton,
• Phytoplankton are consumed by small animals such as zooplankton.
• The methylmercury is assimilated and retained by the animals, while the inorganic mercury is shed from the animals as waste products,
• Small fish that eat the zooplankton are exposed to food-borne mercury that is predominantly in the methylated form.
• Small fish are consumed by larger fish, and so on until it gets to humans.
• Methylmercury displays evidence of biomagnification.

Biomagnification

• Biomagnification stands for Biological Magnification, which means the increase in concentration of contaminated substances or toxic chemicals that take place in the food chains.

Note: Methylmercury is very different to ethylmercury. Ethylmercury is used as a preservative in some vaccines and does not pose a health risk.