Changes in the Terrestrial Background Radiation Field Over Geologic Time
P .A. Karam
All life on Earth is exposed to background radiation. In the United States, the average person is exposed to about 3 mSv/yr from natural sources, most of which come from radon gas. Other sources of natural background exposure include internal, geologic, and cosmic sources. These have changed during the history of life on earth, which may have influenced the way modern life responds to radiation exposure. For the first three billion years life existed, lungs and gills did not exist. This limited alpha exposure severely because of low concentration of alpha-emitting radionuclides in water and because of the very short range of alpha particles. For this reason, radiation dose from alpha-emitting radionuclides has not been considered in research performed to date.
This abstract was presented at the 32nd Annual Midyear Meeting, "Creation and Future Legacy of Stockpile Stewardship Isotope Production, Applications, and Consumption", Environmental Implications of Stockpile Stewardship Session, 1/24/1999 - 1/27/1999, held in Albuquerque, NM.