key point. Wide-ranging research showed that within the ecosystem, the mercury
taken in was mercury concentrated through the food chain from the plant to the
fish, and from the fish to human beings. So the human beings ate the food with
a higher concentration of mercury. The mercury content in the water may have be
en low, but it was accumulated within the body of living beings through the foo
d chain. Namely, the mercury in the wa-ter was further concentrated from water
to the fish and the people through the food chain, So this has been verified by
the example of the Minamata Disease.
They had knowledge of the Minamata Disease at the Agano River, and that is why
they have a more beautiful set of data. Due the production of acetaldehyde at a
plant, you will start to have the patients after you reach a critical level of
production (see Figure 9). And at this point in time it was already clear that
mercury was to be blamed. The plant was therefore closed and it went down. The
number of patients increased up to a certain time, but then it decreased becau
se the plant was closed.
This is the mercury level in the hair of the patients, as has been plotted from
1965 on-wards (see Figure 10). When the plant stopped the production of acetal
dehyde in 1965 and the mercury discharge was stopped, the mercury level in the
hair of the patients de-creased ever thereafter. So we do have such a very clea
r-cut results, that is, the cause was very clearly identified as the mercury di
scharge from the plant.
