 As a result of atmospheric nuclear tests in the 1950s, and until the test ban in 1963, considerable amounts of iron-55 have been released into the biosphere.People close to the test ranges, for example Iñupiat (Alaska Natives) and inhabitants of the Marshall Islands, accumulated significant amounts of radioactive iron.However, the short half-life and the test ban decreased, within several years, the available amount of iron-55 nearly to the pre-nuclear test levels.