'-80 per cent of the fall-out dosevith Gustafson’s results?” during
159, when more than 90 per cent
ose rate at a location at Argonne
found to be derived from these
mon? obtained similar results at
Britain at about the same time.
Laboratory has therefore develcurate determination of environ© partial dose-rate contributions
and fall-out emitters utilizing
chamber and y-spectrometric
These techniques
the field.
umptions as to tho distributions
3 various radioisotopes and on
procedures for interpreting the
than 200 sites in the United
open-field y-dose rates from
y over a wide range from place
‘enerally falling between 5 and
here high natural levels (up to
ed, high thorium and potassium
ily responsible. The relatively
yw range of the observed dose-
9 uranium series are interesting
ier study, and are probably
uranium-238 and radium-226
and the migration of free
ayers of the soils,
1962 and 1963 it was observed
the environment had elevated
isurable amount at every locaQ per cent or more in the total
® common over open ground,
ere observed during the spring
umn 1963 readings were lower,
7ith those a yearearlier in the
iern New England. A decline
16 New York City area sites in
sast four months of quite large
4l background-levels. These
hose of Burch e¢ al." in Engand April 1963, who recorded
‘ somewhat elevated readings
ast-November 1962 and then
it. above normal y-background
untained except for the effect
pril 1963. There is also rough
data’, which seem to indicate
ission product dose rate at a
Laboratory from 2 ur./h to
962 and July 1963 and then a
“>
.
declme to 3 yur./h by October 1963.
With the signing of
the Test Ban Treaty, it is expected that the decline in
fall-out y-dose rates observed in late 1963 will continue,
but at a much slower rate as the long-lived '*Ru-!%*Rh
and ¥7Cs replace "Zr—*Nb as the dominant contributors.
Any assessment of the significance of the fall-out data
presented here in terms of population oxposure-levels
should take into account the relevance of open-field dose-
rate determinations to such considerations and the degree
to which the years 1962 and 1963 can be treated as typical
for conditions of substantial weapons testing.
If we
reduce our open-field fall-out measuroments bya factor of
two to account for the offect of structural shielding as
suggested by Spiers®, and by another factor of two to
correct for weathering processes not taken into account
in our measurements, it would appear that an increase of
the order of 10 per cent in total oxternal environmental
radiation exposure has been experienced by the popula-
tion of the United States during this two-year period.
If this is reasonable, it seems probable that, diring and
shortly after periods of significant nucloar weapons testing,
the exposure of the general population to environmental
y-radiation from deposited fall-out is not noghgiblo m
comparison with that duc to the natural radiation
environment.
1 0’Brien, K., Lowder, W. M., and Solon, L. R., Rad, Nes., 9, 216 (1958).
4 Solon, L, R., Lowder, W. M,, Shambon, A., and Blatz, H., Science, 131,
903 (1960).
1 Shambon, A.. Lowder, W. M., and Condon, W. 4, Health aid Safety Leth.
Rep, HASL-108 (1963),
‘Sievert, R. M., Arkiv. Pysik.. 16, 347 (1059).
* Spiers, F. W., Nature, 184, 1680 (1959).
*Vennart, J., Vature, 185, 722 (1960).
? Gustafson, P. ¥., Marinelli, L. D., and Brar, 8. 8., Seltence, 127, 1240 (1958),
* Gustafson, P. F., Radiology, 75, 282 (1960).
* Peirson, D. H., and Salmon, L., Nature, 184, 1678 (1959).
© Collins, W. R., jun., Welford, G. A., and Morse, R. 8., Scienec, 134, 980
(1961).
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(1961),
88 Gustafson, P. F., and Brar, 8. S., Health Phis., 9, 629 (1063).
' Gustafson, P. F., and Brar, S. &., in The Natural Radiation Enrironment,
edit. by Adams, J. A. S., and Lowder, W. M. (Univ. Chicago Press, 1964).
™ Burch, P. BR. J., Duggleby, J. C., and Spiers, F. W., in The Natural Radiation Environment, edit. by Adains, J. A. S., and Lowder, W. M. (Univ.
Chicago Press, 1964).
% Lowder, W. M., Condon, W. J., and Beck, H. I.., in The Natural Radiation
Environment, edit, by Adams, J. A. 5., and Lowder, W. M. (Univ.
Chicago Press, 1964).
1 oe A. B., U.K, Atomie Energy Authority Rep. AERE-R-4137
2a
17 Kartashov, N. P., Atomnaya Energiya, 10, No. 5, 531 (1961),
transL, Sov. J. dt. Fn.,10, No. 5, 526 (1962).
In English
1“ Wollenberg, H. A.. and Smith, A. R., in THe Natural Radiation Envirenment, edit. by Adams, J. A. 3., and Lowder, W. M. (Univ. Chicago
Press, 1964).
1® Gustafson, P. F., Argonne Nat. Lab. Rep. AN£5967, 156 (1959).
20 Friend, J. P. (ed.), Defense At. Support Agency Rep. DASA-1300, Part 3,
Chap. 3 (1961).
13