BEST AVAILABLE COPY
Paay
June 23, 1966
THE NEW ENGLAND JOURNAL OF MEDICINE
ronment highly contaminated with radioactive material. The radioisotopes of strontium, barium and
iodine, along with some of the rare earths, were ab-
sorbed in greatest amount. Probably, only isotopes of
iodine exceeded the accepted permissible levels. No
acute effects of exposure from the internally absorbed
redionuclides were observed. Since their return to
Rongelap in 1957 the people have been exposed to
low levels of certain residual radionuclides — namely,
Csi"
Zn(this is an induced radtoelement) and
Sr’. Body burdens appear to have reached equilibrium with the environmental levels of these elements, and are well below the accepted permissible
rane,
LATER FINDINGS
Evaluation of the general health status, illnesses,
mortality, fertility and aging over the eleven years
since exposure has revealed no significant differences between the exposed and the unexposed populations that could be attributed directly to raclia-
tion. The slight lag in recovery of peripheral blood
elements has not affected their resistance to disease
and immunologic competence. Although the birth
rate has been about the same in the exposed and
unexposed vroups there was an apparent increase in
miscarriages and stillbirths in the exposed women
as compared with the uexposed women over the
four vears after exposure (41 per cent, or 13 of 32
pregnancies in the exposed, as compared with 16
per cent, or & of 49 pregnancies in the unexposed
women over a comparable peniod). A few congenital
abnormalities have been observed in babtes born to
exposed women, but no correlation with radiation
seems possible at present. Slit-lamp observations
have failed to reveal radiation-induced opacities of
the lens. Stucdies of growth and development? comparing 42 caposed with 75 unexposed children have
revealed a shieht retardation of growth in the bays
exposed at one to five vears of awe, most marked in
those exposed at twelve and cighteen months of
age. The possibility: that radiation was a causative
factor will be discussed heter.
CONSIDERATION OF THE RADIATION DOSE
TO THE THYROID GLAND
radioiodines have been made: 150 rads (from direct
measurements of urinary I); 100 rads (by indirect
measurements using animals — pigs removed from
Rongelap
~—
and
Marshallese
urinary-excretion
data)’; and 160 rads (based) on recent recalculations
of early data).® The last reealculations® were based
on analysis of pooled urine samples mainly from
adadt Rongelap people taken fifteen days after deto.
nation; an estimate of the one-day thyroid content of
I) was bL2 microcuries (5.6 to 22.4 microcurics)
assuming that 0.1 per cent (0.05 to 0.2 per cent
of
the maximum thyroid burden was excreted in the
urine on the fifteenth day. The dose of 160 rads te
the adult thyroid) gland was caleulated from oral
intake and inhalation of the various todine isotopes,
considering their fission vield, the average energy
deposited ino the thyroid wland= per disintegration
wid the time of absorption. The dose to the thyroid
the exp
lation. |
not den
proced
has app
twenty-!
micro“
Tn 18
year-old
have al
ditional
exposed
March,
were mK
ave ane
woman.
was Cill
with no
source of fodine ingestion, and since water was being
found.
in the
rads. In
thyroid
nodular:
rationed at the time of the fallont, it was assumed that
not
vlands of children three to four vears old) was then
calculated by means of these factors with considera
tion of pulmonary function and the thyroid s.ze7
of a child that age. Water was regarded as the main
the children drank the sume amount of water as adults
and therefore had the same thyroid burden of radioiodines, Because of the small size of the gland the beta
dose of radiation to the gland was substantially larger.
The total estimated dose from the varieus iodine isotopes to the child's gland was about LOOO rads, ws''ea
ine
nature
«
CASES W
inciden:
exposed
finiction
PTOryps
nunimiun of about FOO rads and a maximums of | 00
rads. The ghinds received an additional 175) rads
front external gamma radiation. Details of these calculations have been given bs James and Gofiman.§
Though the skin overlving the thyroid ghand was
recat ¢
that the deposits of radioactive materials in this area
added significantly to the thyroid dose since mast of
the beta irradiattons were of gisuffictent energies to
have penetrated to the depth of the gland.
cidence
frequently the site of “beta burns” it is not believed
ths roid
pothyre
at less t
The an
males (.
fernale.
Pyriust
ABNORMALITIES OF THE THYROID GLAND
Phivsical examinations have always included care-
ful inspection of the thyroid region in both exposed
and
unexposed
comparison
groups.
In
addition,
the gland and the relative proportion of the several
determinations of the level of protein-bonnd iodine
and cholesterol in serum have been carried ont al
various intervals since 1959 in some persons. Until
1963 no thyroid abnormality was detected in cite!
in fallout is well known. In addition to ['#. the
ment seen in an unexposed woman. The average
level of serum protein-bound iodine was found to
Calculation of the dose to the thyroid ehind from
ridioactive iodine requires knowledge of its uptake
by the gland, its half-life in the gland, the size of
Yo 27
radioisotopes of iodine.
Unfortunately, in the
present situation few data of a direct nature are
available. The relative distribution of radiciodines
the exposed or the comparison population, except
isotopes of B33) 23 and to a lesser extent Icontributed significantly to the thyroid dose. The only
data available are radiochemical analyses of pooled
urine samples taken fifteen davs and longer after
the fallout. Three separate estimates of the dose to
the thyroid) glands of adult Rongelap people from
be elevated in both the exposed and comparison
populations. It is believed that this is a racial char
acteristic, and that the increase is partly due to an
increased level of the iodoprotein fraction of serum.
No significant differences were noted between the
mean protetebound iodine and cholesterol level: im
for 1 case of asymptomatic diffuse thyroid enlarge-
A,
LB Ft
A.B
A ALT
+
I
th,
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>
"tat
uch pre
wasead