While the world marks the 60th anniversary of the crew of the fishing boat Daigo Fukuryu Maru’s deadly exposure to fallout from a U.S. hydrogen bomb test in the Pacific, hundreds of “forgotten” victims who were also exposed to the testing are reliving the painful memories.

“It is too late (to seek out the truth),” said a former crew member of the Yahiko Maru, a cargo ship sailing in waters near the Castle Bravo test on March 1, 1954, one of the most powerful U.S. thermonuclear blasts.

The Daigo Fukuryu Maru, a Japanese tuna fishing boat based in Shizuoka Prefecture, is memorialized as a victim of the Castle Bravo test, one of a succession of U.S. nuclear tests carried out in the mid-Pacific 60 years ago, with all of its crew members being exposed to radiation.

When six nuclear tests were conducted between March and May 1954 on Bikini Atoll in the Marshall Islands, a total of 1,000 boats and ships are also estimated to have been sailing in nearby waters.

Because the Daigo Fukuryu Maru incident occurred when Japan was about to introduce nuclear power plants from the United States, both Tokyo and Washington hoped to settle the issue as quickly as possible.

They, therefore, limited acknowledging the consequences of radiation exposure from the hydrogen bomb testing to the Daigo Fukuryu Maru, and ignored the crews of other boats and vessels possibly exposed to fallout.

The Yahiko Maru, which set off from then Kuchinotsu town (present-day Minami-Shimabara city) in Nagasaki Prefecture in 1954, is one of the forgotten victims.

At the port town located at the southern tip of the Shimabara Peninsula, which was known as the “town of sailors,” Mitsuyoshi Taira, Toshiyuki Miura and Toyofusa Nakajima boarded the 7,000-ton cargo ship.

Taira and Miura were 39 and 51 years old, respectively, when they climbed aboard the vessel, and worked as a steersman and the No. 1 oiler. Nakajima, then 50, was a cook.

From January through May 1954, the Yahiko Maru twice shuttled between Japan and Makatea Island in French Polynesia. On March 1, 1954, the day of the Castle Bravo test, the vessel was on its first voyage, which began on Jan. 13, and was sailing 500 kilometers northeast of Bikini Atoll.

After the journey, Taira, Miura and Nakajima were diagnosed with cancer and other afflictions, and died over the next 30 years.

Although the government has not acknowledged their deaths were due to radiation exposure, their bereaved families suspect the cause was connected to the Castle Bravo test.

“My father had contracted every disease (until his death),” said Taira’s oldest daughter, Kyoko Nakagama, 68, who currently lives in Oita Prefecture.

According to Nakagama, her father collapsed from a bout of sudden dizziness and nausea around 10 days before the Yahiko Maru returned to Tokyo Port from its second trip to the South Pacific on May 30, 1954.

All 48 crew members underwent blood tests at medical centers in Tokyo or Tamano, Okayama Prefecture. Six of them, including Taira, were diagnosed as “having leukopenia caused possibly by exposure to radioactive substances,” and hospitalized at Okayama University Hospital.

Taira was discharged from the health-care center 20 days later, but subsequently suffered from anemia, angina and other afflictions, and was repeatedly hospitalized.

In 1975, Taira submitted a shipping company-issued document that said “he was exposed to radiation on Bikini Atoll” as well as doctor’s certification to apply for a “hibakusha” nuclear weapon survivor’s certificate. But his application was refused because the certificate was intended only for victims of the 1945 U.S. atomic bombings of Hiroshima and Nagasaki.

The former steersman passed away because of decreased cardiac function in January 1986.

“I can’t help but feel that the government had left the matter unresolved,” said Nakagama.

The eldest daughter of Miura, who died of lymph node cancer in October 1967, one and a half months after being hospitalized, also said her father would have been able to live longer if the state had acknowledged the relationship between his condition and his exposure to radiation.

“If we had been able to prove he was exposed to radiation, my father could have been provided with better treatment,” said Kuni Miyake, 80.

Nakajima passed away in May 1973 due to gastric cancer.

“If there are no records, one’s cause of cancer is regarded as unexplained,” said Kazue Oshima, 76, Nakajima’s second daughter. “Unless continuous follow-up research is conducted, whatever happens in the future can be dismissed with the simple words, ‘The cause cannot be identified.’ “

The Yahiko Maru’s 48 crew members also included Kinya Yamamoto, the ship’s doctor.

The 32-year-old physician, who learned of Washington’s nuclear testing over the radio, instructed other crew members to stay out of the rain. Yamamoto died of myelodysplastic syndrome, a type of hematopoietic disorder, in 2008.

His oldest daughter, Yumiko Urayoshi, 55, said her father had repeatedly stressed that “my body is evidence” and continued taking detailed notes on changes in his condition until shortly before his death.

As former crew members of the Yahiko Maru become increasingly elderly, the number of those who possibly bear witness to the dangers of radiation exposure declines–only six members were confirmed still living via the latest Asahi Shimbun research.

The former Yahiko Maru sailor, who resides in Hiroshima Prefecture, said there is no choice for crew members but to accept the current situation.

“Japan at that time made few complaints to the United States,” said the man, who was hospitalized for a month after returning from the second 1954 voyage. “I feel sorry for those who died previously, but I could not endure the situation unless I delude myself into believing their ages at death were their natural life spans given by heaven.”