we ence ie tee a a ne eee ia ey ow in part 1 ter riia for bone and b one marr lying ng the¢ criite I n applyi not exceed do if annual exposures above, 2 it is assumed that there will e, tis hest dos i the year Of £ hig teriaia in licable criiter tive mia limiting longer term cum cof hot bea requirement for 1 ahon © hand, implement exposures. On the other t will require consicera ‘Tlowest practicable" concep asures to reduce both annual and me effectiveness of remedial the extent pracficable. to s longer term exposure Risk Considerations the \ i sors have reviewed ' 3 technii cal advi k Group and its e anee from ICRP, UNSCEAR, Theable sformation us t cou Committee tha Academy of Science BEIR ey estimate the health risk that may be associated with long-term exposures at-the level of the radiation dose and soil removal - criteria being recormmended. It is clear from this review that kpowlecgs of the relationship between radiation dose and effects _of that on man as characterized in dose-effect curves incomplete even for external radiation exposures. For internal e érs and particularly for plutonium, the sitwationis even less satisfactory. UNSCEAR has summarized their findings by stating that one should not extrapolate ina linear fashion from effects seen at high doses and dose rates to effects at low doses and dose rates since there is strong likelihood of recovery and repair. The BEIR Committee, using only human data, concluded that since the low dose data were incomplete, one should conservatively assure a linear no-threshold dose-effect curve drawn through data obtained at high doses‘and dose rates. The committee further suggested that if this linear no-threshold curve is assumed to be correct, it follows that 6, 000cases of cancer would be produced each year in a population of 200, 000, 000 people exposed at a rate of 0.17 Rem/yr. (This is the FRC RPG for population groups - see Table I.) For the Enewetak population of less than 500 exposed at the same level, one can make the following estimate: 6 X 10° cases/yr X 500 people = 1.5 X 107” cases of cancer/yr 2X 10° people Using a linear dose-~effect curve, exposure at the level of the recommended criterion of 0.25 Rem/yr would give 2.2 X 1072 cases per year. The Task Group vieys this as a pessimistic upper limit of risk. It could be inferred that there may be between zero and three cases of cancer in 100 years if the entire Enewetak population were continuously exposed to 0.25 Rem/yr over that time period, exposurewhole body,at Enewetak, and in fact, to all organs will come from inter jitters. The shape of the . dose-effect curve for exposures from internal emitters is most uncertain because of lack of experience and lack of confidence in extrapolation of high dose and dose rate effects into the very low dose and low dose rate situation. oo MmEereT AVA ADIL FrABY A lack of confidence in A (7,