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The Marshall Islands Are Becoming Less Nuclear

A new study finds that the abandoned nuclear test sites aren’t much more radioactive than Central Park

The Castle Bravo test at Bikini Atoll was more than 1,000 times more powerful than the bomb the United States dropped on Hiroshima. (U.S. Department of Energy)
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If you wanted to test a nuclear bomb in the 1940s and 1950s, you could head to one of two hotspots: Los Alamos, New Mexico or the Marshall Islands. The latter was the site of 67 nuclear tests over the years—dangerous experiments that forced islanders to abandon their homes. But change could be coming for the island exiles. Now, reports Patrick Monahan for Science, a new study shows that the Marshall Islands are becoming less nuclear.

A new study published in the journal Proceedings of the National Academy of Sciences​ found that previous estimates of contamination levels across the Marshall Islands are skewed. Researchers measured gamma radiation—electromagnetic radiation from nuclear fallout that is associated with cancer and developmental delays—on six of the over 1,000 islands in the republic where nuclear tests occurred. On five of the six islands studied, gamma radiation levels were below 100 millirem per year. That’s beneath the safe threshold for human habitation and a fraction of the approximately 310 millirem of radiation the average American is exposed to each year from natural sources.

Those measurements fly in the face of prevailing wisdom about radiation on the islands—wisdom that the study’s authors say is based on outdated, decades-old data. The findings could prompt Marshallese who had to flee their home islands to move back. If so, it will be a welcome relief to the evacuated residents forced to cram themselves onto crowded islands with scant resources.

In 2015, the situation on Kili and Ejit Islands became so bad that Marshallese officials petitioned the U.S. government to provide funds to move people away from the islands altogether. Climate change, which caused widespread flooding and inclement weather, was also at play. The U.S. Department of the Interior has since supported pleas to consider fleeing islanders as refugees.

Those efforts are only fair given the effects the U.S. nuclear program had on islanders. Between 1946 and 1958, 23 nuclear devices were detonated at Bikini Atoll. The most memorable of which was a 15-megaton bomb tested in 1954. More than a thousand times more powerful than the bomb dropped on Hiroshima, it was the largest nuclear device the U.S. ever exploded. At the time, unexpected weather patterns caused radioactive fallout to rain over several other islands.

Bikini Island radiation levels were the only ones in the six islands studied to be above safe levels for human habitation. But at 184 millirem per year, the measurement’s weren’t much higher than those taken at a control island or in New York’s Central Park, which receives about 100 millirem of gamma ray radiation per year. Those levels are probably due to granite within the park, writes Monahan.

Now that it’s been established that the islands have become less radioactive, is it finally time for displaced residents to go home? Not so fast—the study’s authors say that they’re not yet sure if the islands are safe for habitation. They write that other exposure pathways, like the fish-heavy diet the Marshallese enjoy, should be studied before a determination is made. But for the island's former residents, eager to ease crowding and go back to their home islands, the study is a hint of hope for achieving a more normal post-nuclear life.

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