tional Council on Radiation Protection and Measurements (NCRP, 1987a), an average member of the US population receives in each year a total dose from natural background radiation of about 0.3 rem. Exposure to cosmic rays, naturally occurring radionuclides (potassium-40, radium, thorium, and uranium) in rock and soil, and naturally occurring radionuclides incorporated in body tissues (mainly by ingestion) gives a dose in each year of about 0.1 rem, and the remaining 0.2 rem in each year is due to indoor radon. Thus, for example, an average individual who lives for 70 years receives a total lifetime dose from natural background radiation, excluding the contribution from indoor radon, of about 7 rem, and the total lifetime dose, including the contribution from indoor radon, is about 21 rem.
A presentation of information on doses from natural background radiation is not intended to trivialize exposures that military personnel received during their participation in the weapons testing program or to convince individuals that their exposures are of no concern. However, such information can be helpful as each individual judges for himself the significance of his exposures during the testing program.
The types and amounts of ionizing-radiation exposures received by military personnel participating in atmospheric nuclear-weapons test detonations depended on the characteristics of the detonation, the role of the participants, and the proximity of personnel to detonations and fallout of nuclear debris.
When a nuclear explosion occurs, penetrating gamma rays and neutrons are emitted from fission of the fuel (usually 239Pu or 235U or a combination of the two). The gamma rays and neutrons can result in external radiation doses to