- The Minamata Bay is an inner bay facing the Yatsushiro
Ocean (Shiranui Sea) in Kyushu.
- In 1932, the factory started to operate the acetaldehyde
compound acetic acid facilities using mercury as a catalyst.
Contaminants from the factory, especially methyl mercury
turned Minamata Bay into a sea of death.
- It took many years for people to realize the problem
and to understand the causes. During this time, many
victims suffered a pollution-induced disease.
- In 1956, an official recognition of Minamata Disease
was first issued. After that, the facilities suspended
the operation, and a dredging and sludge disposal program
- Presently the mercury pollution, which was the origin
of the environmental pollution, is coming to the end,
but many problems still need to be studied.
- Lake Kasumigaura is located in the northeast of Tokyo
and the southeast of Ibaraki Prefecture, and it is Japan’s
second largest natural freshwater lake.
- Due to natural factors such as the large water volume
to lake area ratio, the lake was particularly prone
to eutrophication. From about 1965, as various activities
in the Kasumigaura basin began to flourish and water
use expanded the quality of Kasumigaura’s water
began to change along with growing concern about the
- Several measures against the pollution of Lake Kasumigaura
were taken by the enforcement of the Ordinance to Prevent
Eutrophication. Among them were regulations of factory
drainage, construction of sewage systems, skimming of
water bloom “Aoko”(algae), and dredging
of bottom sludge.
- Thereafter, the COD gradually decreased. However,
for further water quality improvement, we need to push
a pollutant load reduction measure more on every pollution
source, address the pollution from non-point sources,
and restore sound ecosystems. We must also consider
new concepts for management of the lake and the entire
Kasumigaura basin including the land use planning, total
quantitative regulations considering the capacity of
the environment to absorb pollutants, and the creation
of regional recycling systems to protect our environments.