127
4.M. Dobyns and B.A. Hyrmer: Thyroid Neoplasms and Hydrogen Bomb Fallout
Fable 1. The most recent estimated dose of radiation to the thyroid
in various groups of exposed Marshallese.”
,
Q
al
o>
KWAJALEIN
Q
om
Thyroid dose (rads)
Rongelap (63 people)”
1 year
9year
Adult
l year
9year
Adult
190
190
190
110
110
110
5,000—20,000
2,000-8.000
1,000—4,000
1,300-5.200
§40—2.200
280-1120
Syear
Adult
Ii
11
300-1200
150-600
lyear
Ili
(avg-max)”
670-2,700
’Does not include external dose.
“Includes 3 in utero exposures.
?
adults from Rongelap, and particularly in those who were
exposed as children <10 years of age at the time of the accident.
The decline in thyroid function was noted in 4 Rongelap
children who showed gradual retardation of growth. This was
most marked in 2 children, exposed at 1 year of age [5, 6]. Their
thyroids gradually became atrophic with clinical signs of myxedema. Neither of the 2 children developed thyroid masses,
then or since. As time passed some others among the more
heavily exposed group showed a slight degree of reduced
thyroid function, evident only on a biochemical basis and
without clinical signs of hypothyroidism [7, 8]. Early in the
study Micronesian people were found to have somewhathigher
protein bound iodine (PBI) levels than most populations due to
the presence of unusually high iodo-proteins, so that subnormal
levels were not recognized until morerefined tests for thyroxine
were available. A numberof the exposed Rongelap people have
gradually over the years developed biochemical hypothy-
roidism [9-11].
Between 1965 and 1968, 12 more Rongelap people developed
palpable thyroid nodules which prompted surgical exploration
at New England Deaconess Hospital, Boston. Among the 12
patients there was 1 carcinoma with a positive lymph node
found in 1965. This was the first frank carcinoma found up to
that time.
It is noteworthy that of the 15 individuals undergoing surgery
unul 1968, 14 patients were <10 years of age when exposed and
all were from the most exposed group (Rongelap). All had
adenomatous changes in addition to the 1 carcinoma. Various
pathologists have incidentally commented on the unusual degree of focal or nodular hyperplasia in the adenomasin 9 of the
first 15 cases [8].
In 1969 ona single survey, 5 additional exposed persons were
‘uund to have small palpable nodules and were surgically
“xplored by the author (BMD). Three of these persons proved
10 have carcinoma, | with extensive, metastatic deposits in
humerous cervical lymph nodes. One person with carcinoma
F pad peen exposed on Utinik. More masses then began to appear
e lesser exposed Ailingnae and Utirik groups. As time
SU12143
External dose
“From Lessard and coworkers [2}.
Fig. 1. A diagram of the fallout area from the detonation of a high yield
thermonuclear device (Bravo) on Bikini on March 1, 1954 and the
relationships of atolls of the Northern Marshall Islands [6].
:
(rads)
Utirik (159 people)
°
MAJURO S
Age
Ailingnae (19 people)
Q
oO
Group
passed, between | and 13 persons developed nodules and were
referred each year for surgery by the author (BMD). The peak
occurrence of masses happened in 1979 (8 in 1978; 13 in 1979).
Only 1 person underwent surgery in the period from 1986 to
1988. In the meantime the population base was diminishing
from natural attrition but not from the effects of radiation.
The Need for Controls
Since little was known of the natural occurrence of thyroid
neoplasms in Micronesians, it was necessary to examine the
population thought to have been unexposed [1, 6, 8}. Individuals to be described hereafter are difficult to define as distinct
control groups because they represent a very diverse range of
people andsituations accumulated over the length of the study.
The initial control group consisted of 86 Rongelap relatives who
wereliving on Majuro Atoll, far remote from the fallout area at
the time of the accident. They were matched for sex and age.
Because of inadequate numbers, attrition from natural causes,
and wanderings to other atolls, additional controls were
needed. Therefore, the additional controls consisted of people
of Rongelap origin, who were merely not on Rongelap at the
time of the accident, and supplementedtheinitial control group.
However, some of these controls may have been living on
neighboringatolls (south of Rongelap and Utirik) where slight
amounts of fallout may have occurred [3]. By 1979 this group
had reached 227 people, most of whom had been available for
multiple examinations [9-12]. Another group of Rongelap con-
trols were individuals born after the accident of exposed and
unexposed Rongelap parents. These young individuals were
part of a group who were born after the accident and screened
for possible inherited effects from exposed parents. Many were
reaching an age comparabie to those who had been exposed and
developed nodules at an early age. The entire expanded group
of registered Rongelapese eventually reached 668 people [{1!. 8].
Another group of controls consisted of 473 unexposed peo-
ple. mostly of Utirik origin, who turned up on Utink or other
atolls during street surveys to examine thyroids during the
annual examinations of exposed people. Finally because of the
need for the largest possible control population, a one-time
survey of some of the populations on neighboringatolls (Likiep
and Wotje) was made to provide still another group of 354
controls. Some of those with a palpable mass were registered