Radiation from the 23 nuclear tests conducted near Bikini Atoll in the 1940s and ’50s has lingered far longer than previously predicted.
Radioactive material such as cesium-137 currently produces, on average, 184 millirems of radiation per year on Bikini Atoll. And some parts of the island hit 639 millirems per year, researchers report online the week of June 6 in the Proceedings of the National Academy of Sciences. Those measurements, made last year, surpass the 100 millirems per year safety standard set by the United States and the Republic of the Marshall Islands, which controls the island.
Scientists had predicted that, by now, radiation levels would have dropped to 16 to 24 millirems per year. But those estimates came from extrapolating from measurements made in the 1970s. The mismatch probably stems from incorrect assumptions about how rapidly radioactive material washes off the island, proposes study coauthor Emlyn Hughes, a physicist at Columbia University.
Whether the higher radiation levels pose a serious health risk to caretakers who live on the island for part of the year depends on how long they stay on the island and whether the local fruit they eat is safe, Hughes says.