we eet ee enter te ee . a Guidelines for safe exposures to radioactivity on the atoll are given in terms of the maximum annual dose receiyed hy an individual and are also evaluated in terms of long-term health effects. The main objective of radiological cleanup is to reduce the radioactivity of the Atoll to levels at which the population can be expected to have annual exposures below the value of these guidelines. 5.3.2.1 Long-Term Health Effects. Quantitative evaluation of low levels of absorbed radiation on human health continues to be a subject of medical research. Present knowledge is based on the response to high levels of radiation of research animals, of persons undergoing medical treatment with radioactivity, and of a few victimns of radioactivity accidents. Direct determination of the human health response to low levels of radiation, ~ guch as are discussed in this report, is complicated by a number of factors. such as; e , | the'requirement to study radiation effects ona large population for statistically meaningful results, e the long time delay between radiation exposure and appearance © difficulty in distinguishi of such effects as neoplasms, tion and those not rela iation, <_ ibutable to radia- Poy @ the fact that such factors as cancer susceptibility are widely varying functions of age, sex, genetic constitution, diet, personal habits, socioeconomic factors, and other variables. Because of the above factors, present risk estimates are based predominantly on conservative extrapolations from data obtained at high doses. " : | " The recommendations are based on the conservative assumption of . a nonthreshold linear relationship between radiological dose and the health effect. The assumption of no threshold means that any nonzero dose yields a nonzero effect detrimental to health. Evaluation of risks using | this assumption probably results in overestimates of risks. BEST AVAILABLE COPY ds on Enewetak The methodsexaminedfor limiting radiological hazar | by + Atoll are: Q) the control of the dietof the Enewetak people and, ol. contr (2) the Implication, their agricultural and food gathering practices; ss and (3) atoll; the of ghout the islands ation throu ence of the popul of resid . . ee the cleanup of radioactive materials. a (P,) _—