In contrast, we report on timely measurements of external gamma radiation levels, made in August 2015, on six northern Marshall Islands: Enewetak, Medren, and Runit on Enewetak Atoll Bikini and Nam on Bikini Atoll and Rongelap on Rongelap Atoll. However, these studies calculate radiation levels based on old measurements and assumptions about the half-life of 137Cs in the environment, the major source of gamma radiation, as described below. Previous studies ( 9– 13) have characterized the background radiation levels of the land, water, and food, for several of the contaminated islands. Today, just a handful of inhabitants live on Bikini Island and approximately a dozen people live on Rongelap Island, both groups primarily serving as contractors working for the US and Marshallese governments. However, resettlement of populations to the islands of Bikini and Rongelap has not been realized. Several agreements (Memorandums of Understanding) related to nuclear testing legacy and acceptable levels of radiation have been signed by the Marshallese and US governments beginning in 1982. Cleanup efforts were also undertaken on the islands of Bikini and Rongelap. Enewetak Island is inhabited today by a population of less than 1,000 people. In addition, a concrete dome was constructed on Runit Island in the Enewetak Atoll to serve as a chemical and nuclear waste site. A population of Marshallese people lives on Enewetak today and Medren has since been abandoned. Following the cleanup, Enewetak and Medren islands were resettled. This cleanup entailed the removal of radioactive topsoil on these islands, performed from 1977 to 1980. By contrast, the resettlement history of Enewetak Atoll includes a major cleanup of the islands of Enewetak and Medren. In both cases, large populations were moved back to their home islands when radiation levels on those islands remained well above standards for safe exposure limits. The subsequent history of resettlement decisions has been riddled with mistakes, including the premature resettlement of Rongelap in 1957 and Bikini in 1968. Many of these effects are still being felt by the descendants of the exposed populations ( 2– 4). The inhabitants of these islands suffered greatly from health complications, resulting in death and illness for adults and children, both born and unborn. However, alleged underpredictions of the yield of the largest thermonuclear weapon tested by the United States, Castle Bravo ( 1), coupled with an unexpected easterly wind, resulted in substantial radioactive fallout on Rongelap and Utirik Atolls, where no evacuation had been implemented. Inhabitants of Bikini and Enewetak Islands were evacuated to distant islands before the tests. Enewetak and Bikini Atolls, which were used as ground zero for 67 nuclear tests, as well as neighboring atolls Rongelap and Utirik, were all exposed to high levels of radioactive fallout ( 1). Nuclear weapons testing by the US government in the northern Marshall Islands during the 1940s and 1950s resulted in severe radioactive contamination of numerous islands. To determine conclusively whether these islands are safe for habitation, radiation exposure through additional pathways such as food ingestion must be considered. External gamma radiation levels on Bikini Island significantly exceed this standard ( P = <<0.01), and external gamma radiation levels on the other islands are below the standard. We provide interpolated maps for four islands (Enewetak, Medren, Bikini, and Rongelap), and make comparisons to control measurements performed on the island of Majuro in the southern Marshall Islands, measurements made in Central Park in New York City, and the standard agreed upon by the United States and the Republic of the Marshall Islands (RMI) governments (100 mrem/y = 1 mSv/y). Distributions of gamma radiation levels are provided, and hot spots are discussed.
We find low levels of gamma radiation for the settled island of Enewetak, larger levels of gamma radiation for the island of Rongelap (mean = 19.8 mrem/y = 0.198 mSv/y), and relatively high gamma radiation on the island of Bikini (mean = 184 mrem/y = 1.84 mSv/y). These recordings are of relevance to safety of human habitation and resettlement. Measurable excess radiation could be expected from the decay of 137Cs produced by the US nuclear testing program there from 1946 to 1958.
We report measurements of background gamma radiation levels on six islands in the northern Marshall Islands (Enewetak, Medren, and Runit onEnewetak Atoll Bikini and Nam on Bikini Atoll and Rongelap on Rongelap Atoll).