This disease can be clearly distinguished from traditional industrial mercury poisoning.
It took 12 long years to reach an official conclusion as to the cause of this disease from
the first outbreak. This is because scientific knowledge about and experience with transmission
of mercury compounds up the food chain in those days were very limited, as were the techniques
for analyzing very small concentrations of methylmercury.
In 1968, the government sorted out all the knowledge related to Minamata disease that had
been gathered up to that time, and announced its view point.
"Minamata disease is a poisoning disease of the central nervous system caused by methylmercury
compound, which was produced as by-product in the process of manufacturing acetaldehyde at Chisso
Co. Ltd. in Minamata City and Showa Senko Co. Ltd., located upstream of Agano River".