* Plutonium-239, a 24,000 year half-life isotope that is either unconsumed remains fromthe plutonium-239 composition of the nuclear explosives or is formed by capture of a neutron into . uranium-238 nuclei (Followed later by two beta-particle decays completing the transmutation to plutonium-239) during the instant of the nuclear explosion. Being principally an emitter of alpha The concern is instead in regard to internal exposure, principally to the lung following retention upon breathing the |dust; the subsequent hazard is risk of cancer formation. (Retention of plutonium-239 via the food chain is of very reduced concern.) Other radioactive isotopes exist on the Atoll as a result of the various test series, but the health hazards they produce are insignificant compared to cesium-137, strontium-90, and plutonium-239 and furthermore are insignificant on the bases of any of the several existing guidelines for safe radiological conditions for the general public. These less important isotopes resulted from the following processes during the tests: @ Other fission product isotopes resulting from nuclear explosions. * Isotopes resulting from capture of neutrons by other materials nearby the nuclear explosive during the instant of explosion, for example iron-55 from neutron capture iron in towers, barges, and containers of the nuclear explosive and carbon-14 from neutron capture in carbon found in the natural surroundings. 4 LT EY WEY of very reduced concern regarding external exposures, toe rena ne particles, which are very lightly penctrating, plutonium-239 is