1. INTRODUCTION This report ts a review of the literature on the radfoblology of internal emitters. Its purpose is to consider what has becane known about the radio- biology of internally deposited radionuclides over the last four decades. Our primary emphasis fs the progression of rad iobtological information through the 1950s and early 1960s, when atmospheric testing of atanic weapons was occurring with increasing regularity. oo Most of the over 280 references cited in this report ere from the open literature, although use of technical reports was sometimes also needed. Our focus was on developing a reasonable, documented chronology of the evolution of knowledge about the radfobfology of falloute We have used our scientific judgment about the significance of available Information in distilling an enormous volume of literature into a report of ‘this size. We do not Intend this report to be a complete survey of the subfect. The scientific literature ts replete with overviews of radiobfologic studies, and west Bes not been reviewed fn the onen literature hac heen reviewed in many documents, including those on nuclear reactor safety (US MRC, 1978), radiation risks (UNSCEAR, 1977, 1982; NAS, 1972, 1980), and radiation research in general (IRRC, 1980). the general evolution of radioblological research on Internal e@nitters fron qualitative studies on their radfotoxicity to quantitative assessments of the risk fram exposures to thew (Chapter III). Further, we look in general Important developments in the concern over fallout from nuclear weapons Getonations through the ere of atmospheric testing. at + In this report, after a historical perspective (Chapter 11), we address