Chapter I 



INTRODUCTION 



In the four years since the preparation of the first report of this Subcommittee , 

 advances in radiobiology have contributed significantly to our understanding of the 

 hazards to man from exposure to radionuclides. Research in a wide variety of fields 

 has added to our knowledge of the consequences of the internal deposition of radio- 

 elements in human beings, notably in cases of radium poisoning, and in experimental 

 animals, particularly with regard to radiostrontium, plutonium, and radium. 



During recent years, quantitative aspects of the effects of internal irradiation 

 and of the relation between dose and damage in various tissues, especially bone, have 

 moved into the foreground of much of the experimental work. There has been an in- 

 creasing effort to evaluate radiation risks directly through the study of exposed human 

 populations, thus avoiding the uncertainties of extrapolation from laboratory animals 

 to man. However, it is still necessary to use experimental animals because many 

 factors cannot be studied in man. 



The Subcommittee has decided to issue this report as an interim statement, 

 embodying only few specific data and presenting a brief general survey of the status 

 of the problems. We believe, however, that a future critical analysis of existing 

 data and preparation of a more comprehensive report is desirable. 



