Abstract
Fission products produced by atomic bomb explosions give rise to local and world-wide radioactive fallout. The local fallout consists of large particles, but from bombs of approximates 20-kt range the world-wide fallout consists of particles with diameters less than 0.01 mm which are distributed throughout the troposphere, at 10,000 to 20,000 m. Because of the prevailing westerly winds it is distributed over a relatively narrow band and is washed to earth by rains. With bombs in the Mt range the radioactive dust is found essentially in the stratosphere, from where a small portion continuously descends through the tropopause into the troposphere and to the earth. The fallout is readily incorporated into drinking water and foodstuffs, or may be inspired as an aerosol. In Switzerland air concentrations of fallout in 1956 were slightly increased above the normal radiation level, and increased to maxima at the beginning of 1959 and the end of 1961. These maxima were related to French and Russian bomb tests. Although a truly valid evaluation of the biological risk is difficult, a permissible level of 5 rem (gonads and whole body), 30 rem (bone, skin, and thyroid), and 15 rem (other organs) has been established in Switzerland formore » radiation workers. For the general population these values are less by a factor of 100 (gonads) and 30 (all other organs). The maximum permissible concentration (MPC) in air, water, and foods of any radionuclide depends on its metabolism. For Sr the MPC(air) is 3 pC/m/sup 3/, and for tritium the MPC(air) is 50,000 pC/mg. The MPC (air) for mixed uranium fission products at 10 days is 506 pC/m/sup 3/, and at 365 days it is 92 pC/m/sup 3/. For I/sup 131/ the MPC(air) is 100 pC/m/sup 3/, but because it is incorporated into milk the I/sup 131/ hazard to small children is about 1000 times greater from this source than from respiration. At an air contamination of 0.07 pC/m/sup 3/ of I/sup 131/ milk contains an MPC of 130 pC/l. The present value of approximates 3 pC/m/sup 3/ for mixed fission products is much less than the MPC(air) of 229 pC/m/sup 3/. This present value does not endanger the population, but steps must be taken to control bomb tests. (BBB)« less
Published Version
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