43 exposed people
Chromosome-type aberrations were found in 23 of the
Proportionally, the largest
and 5 of the 8 unexposed individuals (Table II).
found in the low exposure
number of persons with chromosome aberrations was
next with 62 per cent and
group with 84 per cent. The unexposed group was
only 40 per cent of
which
in
group
re
this was followed by the high exposu
re groups one half
exposu
two
the
of
the people showed aberrations. In each
ric chromosomes,
dicent
as
such
events
t
of the aberrations consisted of two-hi
The incidence
nts.
fragme
ic
acentr
being
exchanges and a ring, the remainder
but in
group,
sed
unexpo
the
in
high
of acentric fragments was unusually
among then.
found
were
tions
aberra
t
two-hi
contrast to the exposed people no
with regard to the
The difference between the exposed and unexposed groups
at the 1 per
incidence of two-hit aberrations was found to be significant
cent level (p<0.001).
23
Aberrations ranged from one to four per person. Sixteen of the
such
one
than
more
had
ions
aberrat
ome
chromos
with
(70%)
exposed people
aberration; two of the 5 unexposed (40%) had multiple aberrations. In most
instances no more than one aberration was noted per cell.
There was no correlation between the occurrence of thyroid pathology
and chromosome aberrations. Ten of the exposed people included in this
Only
group developed thyroid pathology since these examinations were made.
children
were
three
earlier;
ons
aberrati
me
four of them had shown chromoso
and one an adult at the time of exposure.
No aberrations were found in the karyotypes that had been made from
the 32 grossly intact cells from the four subjects showing relatively high
aberration rates.
Likewise, no abnormalities were seen in 50 cells from
the bone marrow of one of the exposed subjects.
Discussion
The results of this study demonstrate that a small but significant
number of chromosome aberrations has persisted in blood lymphocytes of
some of the Marshallese people for ten years following exposure to whole--
body gamma radiation from fallout. This conclusion rests on the finding
of the large number of two-hit aberrations (dicentrics, exchanges and a
ring chromosome) in the exposed people which constituted one half of all
chromosome aberrations seen. This was in striking contrast ta the findings
in the unexposed people in whom no two-hit aberrations were found even
though the overall number of chromosome aberrations in this group was about
the same and even a fraction higher than that in the exposed people taken
as one group. Since two-hit aberrations were seen only in the people who
had whole-body gamma ray exposure and not in the unexposed group, we
interpret this finding as a residual effect of radiation,
We are unable to explain the greater incidence of chromosome
aberrations in the group exposed to 70 rads as compared to the group that
received 175 rads. We are also unable to account for the unusually high
incidence of acentric fragments in the unexposed and their relative
defecit in the exposed people. One might consider causative factors such
as the low levels of internal radiation exposure from absorption of radionuclides such as
37¢s, 652n,
sr, or expoSure to such things as virus
139