A recent lawsuit filed by former crew members and relatives of deceased crew members of fishing boats operating near the area where the United States conducted a series of nuclear weapons tests in the Pacific in 1954 — seeking compensation from the Japanese government over its questionable behavior at the time and in subsequent years — carries historical significance. More than six decades after the hydrogen bomb tests at Bikini Atoll in the Marshall Islands, beginning with a test explosion code-named Castle Bravo on March 1, 1954, the lawsuit will help shed fresh light not only on the scope of radiation exposure for Japanese fishermen but also on whether the Japanese and U.S. governments acted properly to deal with the consequences of the fallout from the tests.

Even before the court proceedings begin, the omission on the part of the Japanese government seems clear — its failure to properly examine and keep track of the potential damage to the fishermen’s health and nondisclosure for decades of the records of their radiation exposure.

In connection with the 15-megaton Castle Bravo test, which was over 1,000 times more powerful than the atomic bomb dropped on Hiroshima on Aug. 6, 1945, the tragedy of the tuna trawler Fukuryu Maru No. 5, also known as the Lucky Dragon, is widely known. The fallout from the test fell onto the vessel for a few hours, causing its 23 crew members to suffer nausea. By the time they returned to their home port of Yaizu, Shizuoka Prefecture, two weeks later, they had developed serious symptoms of radiation sickness, and the radio operator, Aikichi Kuboyama, died six months later. The Fukuryu Maru incident sowed the seed for civic anti-nuclear movements in Japan.

The islanders suffered a great deal. The H-bomb tests contaminated many areas of the Marshall Islands so badly that they became unlivable. The tests destroyed the culture of the islands and irradiated thousands of people. In the years after the tests, the U.S. told evacuated islanders that it was safe to return. But many returning residents were exposed to contaminated water, air and food due to the false assurance.

The plaintiffs in the lawsuit, the first legal action seeking state compensation over the 1954 H-bomb tests, are former crew members of fishing boats other than the Fukuryu Maru that were operating in the area around the time of the tests and family members of fishermen who have since died. Most of the fishing boats were from Kochi Prefecture.

With regard to the Fukuryu Maru incident, the Japanese and U.S. governments reached a political settlement in 1955 under which the U.S. paid $2 million, worth ¥720 million at that time, ex gratia to Japan for the injuries and damage caused by the Castle Bravo H-bomb test. The money was distributed to the Fukuryu Maru crew members and the fishing industry.

The plaintiffs’ main contention is that the settlement, which had the effect of preventing Japan from clarifying the U.S. responsibility, plus the Japanese government’s failure for decades to disclose the records of the fishermen’s radiation exposure, deprived them of the chance to seek compensation from the U.S. They are seeking ¥2 million each in compensation from the Japanese government for the mental suffering caused by these developments. Behind Washington’s rush to conclude the settlement with Tokyo was reportedly the concern that the Fukuryu Maru incident may intensify anti-nuclear and anti-U.S. sentiment in Japan. The Japanese government for its part apparently was hoping not to aggravate the bilateral relationship because it was hoping to get nuclear power technology from the U.S.

It has been said that about 1,000 Japanese fishing boats were operating in the area around the time of the H-bomb tests. The plaintiffs contend that Japan’s government failed to notify Japanese fishing boats about the imminent H-bomb tests even though it had received relevant information on the tests in advance.

When a Japanese Communist Party lawmaker from Kochi Prefecture demanded during a Diet session in 1986 that the government disclose results of radiation exposure checks on the fishermen, the government said it could not locate the relevant records. But following repeated requests by a Kochi-based citizens’ group and others working on the issue, the Health, Labor and Welfare Ministry released the data in 2014.

The data covered 473 fishing boats and their crews that were examined by the national and local governments from March to June 1954. The ministry said crew members from 10 boats were exposed to radiation levels above the threshold at which contaminated hauls of fish must be abandoned. But it asserted that their exposure was much lower than the levels that could damage their health. It has been pointed out, however, that the checks failed to take into consideration the fishermen’s internal exposure to radiation.

With the lawsuit, the plaintiffs will try to bring to light the government’s omission, including its failure to conduct follow-up health surveys on the crew members and to pay compensation to those who fell ill due to causes linked to the radiation exposure. Several of the former fishermen died of cancer — although it will be difficult to establish the causal relationship because so much time has passed. At least the court proceedings should shed light on how the government acted when it negotiated the settlement with the U.S. over the Fukuryu Maru incident — as well as on why the records of the radiation exposure suffered by other Japanese fishermen were kept undisclosed for so long and why no follow-up checks on the fishermen’s health were made.

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