The Mizushima Heavy-Oil Leakage Accident in 1974 taught Japanese people an unforgettable lesson that such oil leakage accident would have the great impact on the environment.
Though the oil discharge from vessels and so on had dramatically increased until 1972 as the increase of the import oil, it tended to decrease after the year as shown in Figure 6-1. It is because of the countermeasures such as the regulation, the enforcement of monitoring system, the construction of wasted oil treatment facilities and so on which are implemented based on the Law The Relating To Prevention Of Marine Pollution And Maritime Disaster.
The Russian Tanker "Nahotoka" accident, which leaked large quantity of heavy oil, happened in north-north-east sea region from Oki Island in the Sea of Japan on January 2 in 1997. The widespread oil reached to the coast of the Sea of Japan. Many volunteers participated in the oil collection works on a large scale. The necessity of monitoring on the effect of the remained oil to the coastal ecosystem has been discussed.
The number of oil pollution in the Seto Inland Sea has remarkably decreased from 874 cases in 1972 to 89 cases in 1996, but it occupies about 24 % of the total occurrence number in Japan.
Though the number of sea disasters in the Seto Inland Sea tends to decrease after 1973, it is larger than in Tokyo Bay and Ise Bay.
Figure 6-1 The Number of Oil Pollution from Accidents