The U. S. Environmental Protection Agency (USEPA) has prepared a listing of “exposure to dose” conversion factors in two reports. For internal doses, the report is entitled “Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion and Ingestion”. For external doses, the report is called “External Exposure to Radionuclides in Air, Water, and Soil”. The factors found in these two reports are useful for assessing the radiation dose to individuals who can be reasonably characterized as equivalent to “Reference Man”. Reference Man is a hypothetical individual with well-defined values for daily intakes of air and water or carrier elements, breathing rates, excretion rates, organ sizes, metabolic features, and other physical parameters.