Biomedical Engineering Reference
In-Depth Information
Physician, Hajime Hosokawa from the Chisso Cor-
poration Hospital, reported in 1956 that ''an unclarified
disease of the central nervous system has broken out.''
Hosokawa correctly associated the fish dietary exposure
with the health effects. Soon after this initial public
health declaration, government investigators linked the
dietary exposures to the bay water. Chisso denied the
linkages and continued the chemical production, but
within two years, they moved their chemical releases
upstream from Minamata Bay to the Minamata River,
with the intent of reducing the public outcry. The mer-
cury pollution became more widespread. For example,
towns along the Minamata River were also contaminated.
Hachimon residents also showed symptoms of the
''strange disease'' within a few months. This led to a partial
ban by the Kumamoto Prefecture government, which
responded by allowing fishermen to catch, but not to sell,
fish from Minamata Bay. The ban did not reduce the local
people's primary exposure, since they depended on the
bay's fish for sustenance. However, the ban did acquit the
government from further liability.
Some three years after the initial public health dec-
laration, in 1959, Kumamoto University researchers de-
termined that the organic forms of mercury were the
cause of the ''Minamata disease.'' A number of panels and
committees, which included Chisso Corporation mem-
bership, studied the problem. They rejected the scien-
tific findings and any direct linkages between the
symptoms and the mercury-tainted water. After Hoso-
kawa performed cat experiments that dramatically
demonstrated the effects of mercury poisoning, Chisso
managers no longer allowed him to conduct such research
and his findings were concealed from the public.
32
Re-
alizing that the links were true, the Chisso Corporation
began to settle with the victims. The desperate and rel-
atively illiterate residents signed agreements with the
company for payment, which released the company from
any responsibility. The agreement included the exclusion:
''. if Chisso Corporation were later proven guilty, the
company would not be liable for further compensation.''
Notwithstanding these setbacks, Minamata also repre-
sents one of the first cases of environmental activism.
Residents began protests in 1959, demanding monetary
compensation. However, these protests led to threats
and intimidation by Chisso; so the victims settled for fear
of losing even the limited compensation.
Chisso installed a mercury removal device at the
outfall, known as a ''cyclator,'' but it omitted a key pro-
duction phase so the removal was not effective. Finally, in
1968, the company stopped releasing mercury com-
pounds into the Minamata River and Bay. Ironically, the
decision was neither an environmental one, nor an engi-
neering solution. The decision was made because the old
mercury production method had become antiquated.
Subsequently,
Corporation repeatedly and persistently contaminated
Minamata Bay from 1932 to 1968.
Victim compensation has been slow. About 4000
people have either been officially recognized as having
''Minamata Disease'' or are in the queue for verification
from the board of physicians in Kumamoto Prefecture.
Fish consumption from the bay has never stopped, but
mercury levels appear to have dropped, since cases of
severe poisoning are no longer reported.
Cadmium and Itai Itai disease
The mines of central Japan located near the Toyama Pre-
fecture have been removing metals from the surrounding
mountains since as early as 710 A.D. Gold was the first
metal to be mined from the area, followed by silver in
1589, and shortly thereafter lead, copper, and zinc. At the
start of the twentieth century, the Mitsui Mining and
Smelting Co. Ltd controlled the production of these
mines. As a result of the Russo-Japanese War, World War I,
and World War II, a surge in the demand for metals in the
use of weapons and military equipment caused massive
increases in the mines' production that was aided with the
advent of new European technologies in mining.
Along with the huge increase in mining production
came a significant increase in pollution produced from
the mines. Liquid and solid wastes were dumped into the
surrounding waters, including the Jinzu River that flows
into the Sea of Japan, and the five major tributaries that
flow into the Jinzu River. The Jinzu River water system
supplies water to the surrounding city of Toyama,
30 kilometers downstream from the main mining opera-
tions.
33
This water was primarily used by the surrounding
areas for irrigation of the rice paddies. In addition, water
provided a source for drinking, washing, and fishing.
Large amounts of cadmium were released into the Jinzu
River Basin from 1910 to 1945. Cadmium was extracted
from the earth's crust during the production of other metals
like zinc, lead, and copper that were being mined near the
Toyama area. Cadmium is a naturally occurring element
that does not corrode easily, enters the air during mining,
can travel long distances, and then falls into the ground or
water only to be taken up by fish, plants, animals, or humans
from the environment.
34
The cadmium from the mines
deposited in the river and land of the Jinzu River Basin was
absorbed by the surrounding plants and animals causing fish
to die and the rice to grow poorly. Furthermore, humans
living in that area consumed poisoned water and rice.
As a result of the ingestion of cadmium, a previously
undiagnosed disease specific to the Toyama Prefecture
appeared in 1912. Initially, the symptoms were not well
understood and suspected to stem from either a regional
or a bacterial disease or the result of lead poisoning.
However, in 1955, cadmium was linked to the disease
which came to be known as
itai itai.
In 1961, the
the
courts
found
that
the
Chisso
