.. . .\ .... ... . . ... ..... ..::: :..7 ...... ......... ~=. .,...,..> — , estimate the health risk that may be associated with long-term exposures at the level of the radiation dose and soil removal It is clear from this re~tiew that criteria being recommended. knowledge of the relationship between radiation dose and effects of that dose on man as characterized in dose-effect curves is For internal incomplete even for external radiation exposures. emitters and particularly for plutonium, the situation is even UN’SCEAR has summarized their findings less satisfactory. by stating that one should not extrapolate in a 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 The 13EIR Committee, using only human recovery and repair. data, concluded that since the low dose data were incomp~ete, one should conservatively assume a linear no-threshold dose-effect curve drawn through data obtained at high doses and dose rates. The corrunittee further suggested that if this linear no-threshold curve is assumed to be correct, it follows tk.at 6, 000 cases of cancer would be produced each year in a population of 200, 000, 000 people exposed at a rate of O. 17 Rem/yr. (This is the FRC RPG population for population groups - see Table 1, ) For the Enewetak of less than 500 exposed at the same level, one can make the following estimate: 6 X 103 cases /\-r X 500 Deople = 1.5 X 10 -2 cases of cancerlyr 2 X 10~ people Using a linear dose-effect curve, exposure at thelevel of the recommended criterion of O. 25 Rem/yr would give 2.2 X 10-2 The Task Group vie~w this as a pessimistic cases per year. It could be inferred that there may be upper limit of risk. between zero and three cases of cancer in 100 years if the _ entire Enewetak population were continuously exposed to O. 25 Rem/yr over that time period. Most of the exposure to whole body, at Enewetak, and in fact, to all organs ~~ill come from internal emittei-s. 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 oi high dose and dose rate effects into the very low dose and low dose rate situation. A lack of confidence in . .. ..... .. ... . ....... ...... ....... . ““”i ......— .... . -111-12 ,