~~ 6 =
which might cause genetic effects, have averaged between one
and five thousandths of ome roentgen per year in the United
States during the last three or four years. This figure
‘- should be compared with a normal dosage of 150 thousandths
of one roentgen per year from cosmic rays and natural radio-
activé materials in the environment.
In other words, the
external fallout radiation has been from 0.7 percent to about
three percent of the natural radiation exposure.
’
As another example, in certain countries of the
world a brick house might easily have enough natural radioactive material in the walls ito give up to 40 thousandths
of a roentgen more exposure per year than a wooden house
and a concrete block house gives about 100thousandths of
@ roentgen more annually.
These dosages range between 8 and
100 times the dosage due to test fallout.
Obviously, the genetic effect of fallout radiation
must be very small compared with the genetic effect of
natural radiation.
As you pointed out in your statement, radioactive
ity from tests which already have been held is present in the
stratosphere, from which it will descend for years to come.
The radioactivity of this material constantly is decreasing
through normal radioactive decay.
The tiny radioactive
particles fall so Slowly from the stratosphere that the
continuing fallout in the United States just about compensates
for the radioactive decay of the radiostrontium already de-
*
posited.
Therefore, the present level of radiostrontium in
the soil is about as much as we shall ever have from tests
already fired.
Continued testing would not increase radioactivity
on a straight additive basis, since an equilibrium would be
established between the added radioactivity and radioactive
decay.
If tests were to continue until 1983 at the rate of
the past five years, levels in the United States would be ex-
pected to reach about four times their present values.
Levels about six times the present ones would be reached by
the year 2011 if testing were to continue for that long a
time.
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