Radiation levels in some regions of the Marshall Islands, where the United States conducted atom bomb tests in the 1950s, are far higher than in areas affected by the Chernobyl and Fukushima nuclear disasters, according to new research.
Three studies showed that the concentration of nuclear isotopes on some of the Pacific Ocean islands was well above the legal exposure limit established in agreements between the US and Republic of the Marshall Islands.
Researchers based at Columbia University in the US measured soil samples, ocean sediment and a variety of fruit.
Nearly 70 nuclear bombs detonated by the United States between 1946 and 1958 left widespread contamination on the islands, a chain of atolls halfway between Australia and Hawaii.
The largest nuclear detonation, 'Castle Bravo', in 1954 at Bikini Atoll, was 1,000 times more powerful than either of the bombs dropped on the Japanese cities of Hiroshima and Nagasaki that hastened the end of the Second World War.
The Marshall Islands have experienced rapid growth since the 1960s.
Most of the nation's residents live on two crowded islands and are unable to return to their home islands because of nuclear contamination.
Nuclear fallout from the tests is most concentrated on the Bikini, Enewetak, Rongelap and Utirik atolls.
"Based upon our results, we conclude that to ensure safe relocation to Bikini and Rongelap Atolls, further environmental remediation... appears to be necessary to avoid potentially harmful exposure to radiation," wrote the study authors.