Radiation on Marshall Islands up to 1,000 times higher than Chernobyl or Fukushima
Radiation in some parts of the Marshall Islands, where the US conducted 67 nuclear weapons tests between 1946 to 1958, is much higher than levels found in Fukushima and Chernobyl, according to a new analysis.
According to three studies, published in the journal Proceedings of the National Academy of Sciences (PNAS), a team of researchers from Columbia University analyzed the current extent of radioactive contamination in four atolls in the northern Marshall Islands: Bikini, Enewetak, Rongelap, and Utirik. And, when they tested the soil for plutonium 239 and plutonium 240, the team found that in Bikini, plutonium concentrations were up to 15-1,000 times higher than in samples from areas affected by the Chernobyl and Fukushima disasters.
An atoll is a ring-shaped coral reef or island surrounding a lagoon, which is a body of water.
The assessment shows that external gamma radiation was significantly high in Bikini Atoll, Enjebi Island in Enewetak Atoll and Naen Island in Rongelap Atoll, compared with a control island in the southern Marshall Islands. The levels were so high in Bikini and Naen that they even exceeded the maximal exposure limit established in a memorandum of understanding between the US and the Republic of the Marshall Islands.
“High activity concentrations of certain radioactive isotopes were observed in soil samples from Runit and Enjebi Islands in Enewetak, as well as from Bikini and Naen Islands, in some cases exceeding levels found in areas affected by the Fukushima and Chernobyl nuclear disasters. The radiation levels on Bikini Island, which served as the primary island for habitation on the atoll, before and in the aftermath of the testing, are too high for relocation to Bikini,” says the first study.
It further says, “We found external gamma radiation values on Naen to be the highest of any island we investigated, well above the 100 mrem/y agreement between the Republic of the Marshall Islands and the US governments. In Bikini, the average value of background gamma radiation is 190 mrem/y, which is nearly double the agreed-on limit.”
From 1946 to 1958, 67 nuclear weapons were tested in the Marshall Islands, a remote constellation of atolls in the Pacific Ocean, which was then a US trust territory. Two atolls--Bikini and Enewetak-- were used as ground zero for the tests. This caused unprecedented environmental contamination and for the indigenous peoples of the islands, long-term adverse health effects. The people of Rongelap and Utirik were also affected by radioactive fallout from the largest nuclear test the US has ever conducted, the Bravo test, held on March 1, 1954.
“Although the Marshall Islands is home to approximately 6% of the total number of tests conducted by the US (67 of 1,054 total tests from 1946 to 1992; the majority of US tests were performed underground), it bore the burden of more than half the total energy yield of all nuclear weapons tests conducted by the US,” says the paper.
Consistent with their previous findings, in which the researchers found low levels of external gamma radiation on Enewetak and Medren islands, the team also found low levels of external gamma radiation on both Ikuren and Japtan islands. “However, we do find elevated gamma radiation levels on Enjebi Island in northern Enewetak. In addition, one of two soil samples we collected on Enjebi Island had high concentrations of all five radionuclides. Runit Island, which is home to a nuclear waste repository, has significant levels of all five radionuclide concentrations,” says the paper.
According to the researchers, the results suggest that people currently living in southern Enewetak are not likely to get significant exposure to radiation from nuclear weapons testing. However, the presence of radioactive isotopes on Runit Island is a “real concern, and residents should be warned against any use of the island,” they add.
“Moreover, wash off of existing isotopes off the islands into the ocean from weathering and continued sea-level rise continues to threaten further contaminating the lagoon and the ocean at large. Investigating radioactivity levels in the ocean near Runit Island, and in the northern Marshall Islands more generally, is of utmost importance. Furthermore, residents of southern islands in the Enewetak Atoll should also be warned against spending time on northern islands, including Enjebi Island,” the researchers recommended.
In a second study, the researchers mapped radioactivity levels of isotopes in ocean sediment from the Castle Bravo crater at Bikini Atoll.
Activities of several isotopes (239, 240Pu, 241Am, and 207Bi) throughout the crater were at least an "order of magnitude higher" than those found in sediments elsewhere in the Marshall Islands, the study showed.
The third study looked at radioactive contamination of fruits in the northern Marshall Islands. Over 200 fruits, primarily coconuts, and pandanus were collected on 11 islands from the four atolls, and the level of cesium-137 (137Cs) contamination was determined for individual fruits. According to the study, Cesium-137 has a half-life of approximately 30 years and is readily absorbed by food crops, thus representing a health hazard for island inhabitants.
“In situ measurements of radioactive 137Cs levels in coconuts and pandanus fruits” revealed that a sizeable fraction of fruits from Bikini and Rongelap atolls had radioactivity levels exceeding the limits set by several countries and international organizations. “Contamination was especially high on Bikini Island, where some fruits exceeded even the highest safety limits. The results have implications for resettlement of the affected islands,” says the team.