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Health Phystes Pergamon Press 1973. Vol. 24 (May), pp. 555-557. Printed in Northern Ireland
Period*
(Received 7 July 1972; in revised form 3 August 1972)
AFTER the partial test ban treaty in 1963 and subsequent stopping of nuclear weaponstesting in the
atmosphere by United States and Soviet Union, the
level of radioactive contamination in the biosphere
has been reduced considerably. China and France
whodid not signthis treaty, continue weaponstesting
in the atmosphere. At the present time there is no
significant increase in the levels of radioactive contamination from theselatter tests, as these constitute a
very small per cent of total tests conducted by the
U.S.A. and U.S.S.R. Nevertheless, these tests do pose
possible future hazards and should testing continue,
periodic monitoring of the atmosphere and human
subjects is necessary.
Cesium-137 is one of the products which results
from nuclear explosions. Because ofits long half life
(Ty = 30 yr) and ease with which it enters into the
body through food and milk, 137Cs presents a potential
radiation hazard to man. This report presents body
burdens of !37Cs observed in a selected population of
Long Island from the beginning of 1960 until the end
of 1971. Estimates of total radiation dose are also
given and the results are compared with those of other
investigators. Early results of this investigation have
been previously reported.)
Methods and Materials
Cesium-137 emits a gamma ray of energy of
0.66 MeV and body burdens of cesium can be
measured with whole body counter. Twodifferent
Brookhaven whole body counters were used for the
measurements. Initially, an 8 x 4-in. sodium iodide
crystal detector was used in a standard chair counting
geometry.'2) In 1967 this system was replaced by a
more sensitive and advanced 54 crystal detector
system with an on-line computer facility.) This
system, in addition to its high sensitivity, corrects
individually for body absorption of gamma rays
employing broad-beam 47Cs sources and a computer
program.” The counting time was reduced from
30 min in chair geometry to 15 min in 54 crystal
geometry. As usual, to avoid any possible external
contamination, each subject changes to hospital dress
and showers prior to counting. Both the systems were
intercalibrated before the switch over.
* Research supported by the U.S. Atomic Energy
Commission.
Rerositony
SVL
Ten normal and healthy subjects (7 males and
three females) who were counted once every month
for 12 yr are employees of Brookhaven National
Laboratory (BNL). These subjects did not have any
significant occupational contact with radioactive
substances. At the start of study their age ranged
from 25 to 45 yr.
In addition to 87Cs measurements, body potassium
of these subjects was also measured by counting
gamma ray activity of naturally occurring radio-
isotope “K,
Results and Discussion
Because 387Cs follows a metabolic path similar to
that of potassium and is found mainly in muscle mass,
body burdens of 157Cs are expressed in terms of body
potassium (pCi/g). This ratio tends to minimize the
spread in values due to variations in body weight,
The results are presented in Fig. 1. After nuclear
weapons testing in the atmosphere was stopped
towards the end of 1959, there was a drop in the
specific activity of 87Cs, and the average value in 1961
was 37 pCi/g. ANpERson4) of Los Alamos Scientific
Laboratory (LASL) reported 25-30 pCi/g at the end
of 1961. Cesium-137 levels in man started rising in
1962 again after the start of a new series of tests in
1961. In December 1962, specific activity of 87Cs
_ was about 75 pCi/g andin March 1963 it rose to 110
pCi/g.) In the present study, the average value for
1963 was 80 pCi/g which reached a maximum value
of 180 pCi/g in August 1964. The sharp rise was observed during the spring of the year associated with
heavy rainfall. The 18’Cs levels were lower in female
by 20% when compared with males.
After the test ban treaty in 1963 and subsequent
decrease in radioactive contamination in atmosphere,
137Cs concentration in man started declining towards
the end of 1964. The average value for 1969 was
18-20 pCi/g with very little change in level in 1970
and 197].
A comparison of the present results with those of
other investigators is shown in Fig, 2. The number of
variables involved in the level of 487Cs make it
difficult to compare the results from other countries.
Someof these variables are food habit, geographical
location and the variability of biological half life of
137Cs in man. Results obtained by BNL comparevery
well with LASL, however, the corresponding valuesin
the U.S.S.R. were uniformly higher (Fig. 2).
The rate of fall of the Cs concentration in
human beings was found to have a half life of about
520 days from September 1964 until 1968.
RECORDS
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Fallout ’Cs-Levels in Man Over a 12 yr