452 1S0T0PIC TRACERS AND NUCLEAR RADIATIONS [Chap. 19 



Parker [9]. By the tolerance dose is meant the amount of radiation that 

 an individual may receive and suffer no observable ill effects. It is usually 

 expressed as a dosage rate, as the amount allowable per day or per week. 

 For several years in this country the accepted figure for x- and gamma rays 

 has been 0.10 r per day. Factors taking into account the relative biological 

 effectiveness of other types of radiation have modified this figure for neutrons, 

 protons, and alpha particles. Table 40 gives the tolerance daily doses 

 accepted by the Atomic Energy Commission for various types of radiation: 



Table 40. Daily Tolerance Doses [10] 



x-rays . 10 r 



Gamma rays . 10 r 



Beta particles 0.10 rep 



Fast neutrons* 0.02 rep 



Thermal neutrons . 02-0 . 05 rep 



Alpha particles 0.01 rep 



* Also applies to protons. 



A lower tolerance figure has been advocated by some, and recently the 

 National Advisory Committee on Radiation Protection has recommended 

 0.30 r per week for x- and gamma rays with proportionately lower figures 

 for other types of radiation. The recommendation regarding exposure of 

 the hands is that a dose three times that for total body irradiation be allowed, 

 or approximately 1 r per week. This committee has also suggested that 300 r 

 be taken as the upper limit for accumulated lifetime exposure. It seems 

 probable that these lower allowable doses will be generally accepted in the 

 near future. 



The hazards associated with the presence of radioactive material inside 

 the body depend upon the metabolism of the material, its radiation char- 

 acteristics and half-life. Some substances, for example, when ingested, are 

 not absorbed from the gut, others are readily absorbed; radium is a familiar 

 example of a substance that may find its way to the blood stream by way of 

 the gastrointestinal tract or the pulmonary tract and is deposited in bone. 

 Its presence in the skeleton over long periods of time has been associated with 

 the development of malignant bone tumors. Osteogenic sarcomas and 

 anemias may be expected also with other long half-life isotopes that have 

 affinity for the skeleton. Certain isotopes such as radio sodium are more 

 widely distributed and result in general body radiation. 



Care must be taken in the laboratory that radioactive vapors and dusts 

 are not allowed to contaminate the air and result in internal radiation follow- 

 ing inhalation. Obviously, smoking and eating in the laboratory are 

 hazardous. 



Fairly elaborate medical supervision of personnel has been carried out in 

 Manhattan District and Atomic Energy Commission laboratories which 



