-28much as a factor of 2.
UCRL- 3644
It should remain nearly at this level, estimated as a
maximum of 0.0012 r/fyr, for an indefinite period.
Cesium-137 body burden at 0.001 r/yr is certainly not to be considered
an adult hazard.
With a linear relation between effect and dosage, 0.001 r/yr
over a lifetime would be less than 0.1 r, and irreversible accumulative effects
of radiation, such as leukemia, might be increased by less than
O.lr
50 r leukemia-doubling dose
= 0.002, or 0.2%.
Stated in terms of life span lost or of the total tendency toward disease,
0.1 4r
Cs
dose x -10 days of life span per r amounts to | day lost from the life
span. A loss of 1 day is very small compared with health-modifying factors
that are measured in years instead of days. Thus, in comparison with the
smoking problem, the long-term effect of Cs!37 is approximately 1/40, 000
as deleterious. Only this extraordinary method of estimation by extrapolation
of effect can convince the human reason that there is any such effect at all;
even the best statistical procedures could not detect it through study of the
most accurate data on the 160,000,000 people in the United States. A 0.2%
increase in leukemia (which is approximately 0.002 x 8,000 cases per year)
is just 16 additional cases. This 8,000 expected normal incidence can fluctuate by random interplay of chance factors by plus or minus 1%, equal to 80
cases per year;.thus, 16 cases of increased incidence cannot be detected.
The Level of Radiation Exposure from Fallout
The total increase in background radiation on a global basis, asa
consequence of radioactive fallout, has been very siight. In the preatomic
age, natural sources of radiation produced an average radiation exposure of
0.1 to 0.2 r/yr®”The variation is due to slight geographic differences, to
differing radioactive content of earth and buildings, and to the variation of
cosmic radiation with altitude. At 5000 feet above sea level, cosmic-ray
intensity (measured by numbers of ionizations produced in matter) is increased
to 1.5 times the sea-level intensity of cosmic rays; at 10,000 feet, the cosmic-
ray ionization is 3 times that at sea level.
The increased human-tissue irradiation due to fallout and ingestion
of radioisotopes is approximately as follows:
Soft tissue irradiation
Bone irradiation
(r/yr)
1955-1956
Csi3?
(r/yr)
0.0009
gr?0
<0.0004
0
(0.002 (adult)
0.0012
0
<0. 0006
0.04to 1.5
(0.004 (young)
Predicted future values
Csl37
Sr90
Table V lists human radiation exposures from a number of sources.
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