Marshall Islands, Where U.S. Ran 67 Nuclear Weapon Tests, More Contaminated than Fukushima and Chernobyl

Some of the Marshall Islands, where the U.S. conducted dozens of mid-century nuclear tests in the mid-century, have radiation levels higher than Fukushima and Chernobyl, according to scientists.

Made up of two chains of atolls comprised of over 1,000 small islets, the Marshall Islands sit in the central Pacific Ocean between Hawaii and the Philippines. Following the Second World War, the U.S. occupied the islands and used them for nuclear weapons testing between 1946 and 1958. Bikini and Enewetak were used as ground zero and residents were relocated so the 67 tests could be carried out.

The Marshall Islands tests made up only around 6 percent of the 1,054 carried out by the U.S. between 1946 and 1992, but the area bore the brunt of the energy yield. The Bikini Atoll alone was hit by a total yield of around 77 Mt, or almost 40 percent of the total energy yield of all US nuclear tests in that time, the authors of a new study wrote.

Scientists investigated levels of radioactive contamination in the atolls of Bikini, Enewetak, Rongelap and Utirik to the north of the chain. The researchers looked at soil samples, ocean sediment and external gamma radiation levels collected from the territory. Tests conducted in the southern Majuro Island in 2015 acted as the control for external gamma radiation levels.

Scientists found external gamma radiation levels on Enewetak Atoll's Enjebi Island andNaen Island in Rongelap Atoll were significantly elevated compared with the southern islands. The radiation on Bikini and Naen islands were at levels higher than agreed upon in a memorandum between the U.S. and the leaders of the Republic of the Marshall Islands. The average value of background gamma radiation levels on Bikini was found to be nearly double that limit. This means residents will not be able to return to Bikini.

The authors also studied cores taken from the crater left behind by Castle Bravo, the biggest hydrogen bomb tested by the U.S. The bowl was contaminated with radionuclides throughout, and contamination levels of radioactive isotopes like plutonium and americium "will likely last for centuries."

The authors said they were surprised by the how polluted Rongelap Atoll was as it was not a site of nuclear testing, "but was only exposed to fallout, primarily from the Bravo test performed in 1954."

Their three studies were published in the journal Proceedings of the National Academy of Sciences.

Marshall Islands, Arno Atoll,
A stock image of the Marshallese Arno Atoll. Scientists have investigated radioactive contamination in the Marshall Islands. Getty

Scientists not involved in the research told Newsweek the findings were useful, but not surprising.

Zoe Richards of the Coral Conservation and Research Group at Curtin University, Perth, Australia told Newsweek: "These studies make a valuable contribution to our understanding of the longer-term impacts of the RMI [Republic of the Marshall Islands] nuclear testing regime. Up until now little independently collected data about contamination levels has been publicly available."

She said the results from Naen "are a particular cause for concern."

"The suitability of the northern islands for human occupation is an issue of broad cultural and social significance, especially to descendants from these islands."

"For the northern Marshall Islanders food security is a very real concern and it is important for clear, relevant and reliable advice to be issued to people to clarify if breadfruit, coconut, coconut crabs, chickens, lagoonal fish or other plants and animals are unsafe to eat," she said.

Steven L. Simon of the Epidemiology and Biostatistics Program, National Cancer Institute, National Institutes of Health directed a major radiological survey by the Marshall Islands Government, which published its findings in 1997. He told Newsweek: "The report by Hughes is a nice analysis, though the topic is already well understood."

He also questioned why the authors did not extensively cite and compare their findings to previous works.

Professor Jim T. Smith of the School of Earth & Environmental Sciences at the U.K.'s University of Portsmouth told Newsweek: "This study is broadly consistent with what we know about transfers of radioactivity, particularly radiocaesium, in this and other contaminated systems."

"The dose rates are above the agreed limit of 1 mSv [100 mRem] per year, but this in no way means that they are dangerous—they represent a very small additional risk of future cancer if people were to resettle on Bikini Atoll," he said.