HEALTH PHYSICS AND RADIATION PROTECTION 



91 



15 inc of radioactive material for procedures in any one week. The data 

 are summarized in Table 3-4. It is clear that the isotope users were 

 receiving less radiation than the X-ray workers and were well below the 

 maximum permissible Unci. Knisely et al (40) have described the prob- 

 lems in the medical use of radioisotopes employing of the order of 30 c of 

 radioactivity for internal use per year. Even under these conditions the 

 acceptable weekly dose was rarely exceeded. 



Table 3-4. Survey of R.\i)Iation Exposures during 1950, 1951, and 1952 



[Compiled from Charles K. Spalding, I'^gilda Deamicis, and Russell F. Cowing, 

 Radiation Exposure Survey of X-ray and Isotope Personnel, Nucleonics, 11: 46-47 



(1953).] 



It is emphasized that the maximum permissible level should not rep- 

 resent an invitation to accept this dosage. Nor should the individual or 

 institution assume the attitude that precautions can be neglected so long 

 as this level is not exceeded. Rather, it is advisable to strive for the 

 lowest possible exposure at all times. Exposures as high as 0.3 r/w^eek 

 are entirely unnecessary if the radioisotope procedures are properly 

 undertaken. The reader interested in genetic effects should consult the 

 review of Plough (32) and the article of Muller (41), who argues that the 

 exposure of large numbers of the population to 0.1 r/day may lead to 

 obvious damage in future generations, since the radiation dosage appears 

 to be cumulative. To repeat, however, radioisotope studies can be car- 

 ried out readily with exposures acceptable to the extreme pessimist. 



The external irradiation hazard for a given isotope is governed by (a) 

 quantity of active material, (6) distance from the material, (c) duration 

 of exposure, and (d) absorption of radiation between the source and the 

 worker. At low levels of radioactivity the hazard may be controlled by 

 a, h, or c above. However, at levels of about 1 mc, especially with high- 

 energy gamma rays, some shielding protection is requii-ed, and the follow- 

 ing are some practical considerations in regard to this matter: 



Shielding. It should first be stated that, even though shielding is used 



