estimate the health risk that may be associated with long-term
exposures at-the level of the radiation dose and soil removal
criteria being recommended. It is clear from this review that
knowledge of the relationship between radiation dose and effects
of that dose on man as characterized in dose-effect curves is
incomplete even for external radiation exposures. For internal
emitters and particularly for plutonium, the situation is 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 assume 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 6,000 cases of

cancer would be produced each year in a population of 200, 000, 000

people exposed ata 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 sarme level, one can makethe

following estimate:

6X 10° cases/yr X 500 people =

2X 10° people

1.5X 1072 cases of cancer/yr

Using a linear dose-effect curve, exposure at the level of the
recommended criterion of 0,25 Rem/yr would give 2.2 X 10-2
cases per year. The Task Group views 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.

Most of the exposure to whole body, at Enewetak, and in fact,
to all organs will come from internal emitters. 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. A lack of confidence in

JH-12

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