Minimata, Japan - 1950s



During the 1950's an acetaldehyde plant in Minamata began dumping heavy metals into the local bay, and ended up poisoning the local aquatic wildlife. After a while, poison symptoms began emerging in the local population, many of which lost basic motor controls and began to act very irregularly.

Toxicological Perspective


In the late 1950s Minimata Bay became contaminated with Mercury from a nearby factory manufacturing the chemical acetaldehyde. Mercury, used in the manufacturing process, was being discharged into the Bay. Due to mercury's bioaccumulative properties, the fish in the bay were being over exposed to methyl mercury. The fish passed on the Mercury built up in their bodies to the fish-consuming residents nearby. Scientists estimate that the Biomagnification of the Mercury was as great as a millionfold (#Dartmouth, 2001).

Initial symptoms included uncoordinated movement and numbness of the lips and extremities, followed by constricted vision (#Gilbert, 2004). The effect upon the infants was even more severe as many were born with a wide range of disabilities. This was one of the first modern lessons of the dangers of methyl mercury.

The Japanese authorities were hesitant to publicize the issue and just over a year later a similar incident happened at Niigata, Japan where 13 people died and 330 were affected.


  • Gilbert, Steven G. A Small Dose of Toxicology. CRC Press, 2004.
  • Dartmouth University's Toxic Metal Research Program's page on mercury, 2001. Retrieved on 12-20-06.
  • Minamata disease - Wikipedia