The 1954 Bikini Atoll Incident: an Update of the Findings in the Marshallese People (the Medical Basis for Radiation Accident Preparedness, 1980) (Partial)

Page 1

Published 1980 by Elsevier North Holland, inc. “~~e 1954 Bikini Atoll Incident: An Update of the Findings in the Consultant and former Head of the Marshall Island Medical Program at The thyroid findings in the Marshallese people accidentally exposed to radioactive fallout following the detonation of a nuclear device at Bikini in 1954 are reported in detail in a 20-year review{l’ and other repofis. (2-1) A 25-year review is being written. A brief upchting is presented here. The Marshal]ese populations with exposure data are lisled in Table 1. The early effects of exposure on the Rongelap group were similar to those reported by Dr. Kumatori for the fishermen on [he Lricky Dra:on. Transient nausea and vomiting occurred In that g[-oup and (o, a lesser degree in the Ailingnae group but were not reported in the Ul]nk group. The major findings in the Rongelap group were depression of blood leukocytes and platelets to about one-half normal levels for 4 to 6 weeks, widespread “beta” burns of the skin with epilation, and significant internal absorption of radionuclides. These findings were less pronounced in the Ailingnae group and were not documented in the Utirik population. These observations are described in detail in eadier reports. During the first-decade there were few findings that could definitely be associated with radiation exposure; although there did appear to be a lag in complete recovery of leukocytes in the Rongelap group. During Ihe second decade, however, there were serious developments in the exposed Rongelap group —a death from acute myelogenous leukemia and numerous thyroid abnormalities along with growth retardation in some of the children. Development of Thyroid Abnormalities Radiochemical urine analyses shortly after the accident revealed measurable amounts of radionuclides, particularly isotopes of strontium,

Page 2

Table 1. Exposures of ?.4arshallesePopulations Distance Xo. of Amount of F:tlm3tcd Atoll from B]km! people fallout gamma dose Rongelap -100 milef 67 Heavy (snow-like) 175 rad Lwik -300 mder 158 hot whle 14 rad barium, and iodine. The significance of the radioiodlne exposure was not fully appreciated at that time. When thyroid abnormalities began to appear, a re-evaluation of thyroid dose indicated an estimated dose of 335 rad to Rongelap adults and doses ranging from 700 to 1400 rad in the children exposed at less than 10 years of age. Lower doses were calculated for the other populations. The higher doses in the children were related to’ the smaller sizes of their thyroid glands. The largest component was ’311,but shorter-lived isotopes of iodine, particularly 1321, IN[, and 1351, contributed more than half the dose. The first indication of thyroid trouble was the finding of growth retardation in a number of exposed Rongelap children, and later correlation with decreasing thyroid hormone levels indicated decreased function of the gland. Two bo!’s de}eloped frank myxedema. II was about [hi> time ! 1964) that th>rold nodules began appearing. particularly in the e~posed children. lrt subsequent years, the nodules continued to appear in the Rongtlap and Ailingnae group and, beginning about 1967, in the Utink groups. Table 2 shows the numbers of subjects who have had (hyroid nodules up to the present. The Rongelap and Ailingnae people are seen to have greatly increased numbers of nodules. b~til benign znd maii:nant. arid the Utirik group also appears to have increased numbers compared with the unexposed Table 2. Thyroid Nodules Appearing from 1964 to 1979. Group “Total nodules Cancera ‘The number of cancer cases is tentative since final diagnoses on some recent cases are

Page 3

Ire was not J rad in the iarly in the people. In the Rongelap-Ail ingnae group, 65% of those exposed as children had nodules compared with 2WC of those exposed as adults. %radoxically, in the Utirik population a ~eater percentage of adults had nodules in spite of a higher dose to the childrerr”s glands. During the past ten jears, a disturbing find{ng has been the furtirc” development of ~hyroid hypofunction. even in >onk’ Rongeiap people without other detectable abnormalities. Table 3 shows the present status of thyroid hypofunction. The positive category represents individuals who have exhibited two TSH (thyroid-stimulating hormone) levels of 6 ~U/ml or greater. The suggestive category represents individuals who have two TSH levels of 4 to 6. The association of radiation exposure with the development of thyroid abnormalities in the Rongelap populahon seems “apparent though the Utink findings are less clear-cut. The development of thyroid tumors following radiation exposure is well documented in the Japanese exposed to the atomic bomb and in patients, particularly children. fo!lowing On a risk per rad basis, the induction of thyroid nodules and cancer in the Marshallese appears to be about equal [o that following X-ray exposure. Since 1311 is believed to be only about one-tenth as effective as X irradiation in producing thyroid abnormalities, it seems likely that ic the Marshallese the exposure to the short-lived isotopes of iodine 1321, IW1 and 1~~1which have more energetic betas and deliver a faster dose rate than 13’1,might account for the high incidence. The findings in the Marshallese emphasize the importance of thyroid exposure to radioiodines that may result from warfare or accidents in which radioiodines are released. Exposure to penetrating gammas or neutrons is a more serious hazard not only because of their acute effects. but also because of the fatal nature of malignancies such as Ieukernw which may develop. Deaths due to thyroid abnormalities including cancer Table 3. Thyroid Hypofunction in MarshaIlese Populations Group Positive Suggestive Totata ‘Some of lhese subjects appear also in the nodu[e table, i.e., they h~ve both hypofunctkn

Page 4

are rare, and such abnormalities are amenable both (o pre~’entive mea-( sures (such as prophylactic use of stable iodine) and to treatment with hormones and surgery. Conard R.1 Summary of thyrod Iindtngs m Marshallese 22 years after exposure 10 York, Grune :~rd Stratton. 1977. p 241. appeting as a deb) ed rnanifesta:mr, of accidenmi exrwsure to rddloactlve fallout in a international Atomic Energy Agexy. Vienm. 1978, pp 101-115.