FOREWORD 



With the artificial production of radioactive nuclides, man greatly 

 increased the potential radiation hazards arising from materials de- 

 posited in his own body. The complete evaluation of these hazards re- 

 quires a vast amount of experimental information, much of which is not 

 presently available. Information on distribution, retention, and ex- 

 cretion of each nuclide must be known in considerable detail. The prob- 

 lem is compounded by the fact that each of these three factors may 

 depend upon the physical and chemical state in which the nuclide enters 

 the body. Absorbed dose calculations are complicated by the irregular 

 patterns of retention; the effects of the rapidly varying dose rates that 

 exist in close proximity to an emitter are largely unknown. 



Although a complete hazard assessment is in general not now 

 possible, a good start has been made, and some practically useful ap- 

 proximations can be made. The interim report of the Subcommittee 

 on Internal Emitters is in the nature of a status report. The pertinent 

 factors in hazard evaluation from internal emitters are discussed in 

 general terms and the present situation summarized. It is hoped that 

 future research results will permit a more detailed discussion in later 

 reports. 



Shields Warren, Chairman 

 Committee on Pathologic Effects 



