Exposure of the Population in the United States and Canada from Natural Background Radiation (Supersedes NCRP Report No. 45)-97718230

Report No. 94 is another of the reports providing detailed assessment of population exposures. Natural radiation and radioactivity in the environment provide the major source of human radiation exposure and thus a comprehensive evaluation of exposures from this source is an important aspect of the overall assessment of population exposure. This Report gives a broad picture of exposure to natural background radiation. It includes considerable descriptive material in the introductory sections and then presents data summarizing the available information on the levels of natural radiation in the environment, the consequent average exposures, and radiation doses to the population and, wherever possible, the distribution, or at least the variability, of these factors. Treated in the Report are cosmic radiation, cosmogonic radioactivity, radionuclides in the earth, external terrestrial radiation, inhaled radionuclides, internally deposited radionuclides, and unusual exposures. An appendix provides information on fallout from nuclear weapons tests.