Abstract
The US nuclear weapons testing program in the Pacific conducted between 1946 and 1958 resulted in radiation exposure in the Marshall Islands. The potentially widespread radiation exposure from radio-iodines of fallout has raised concerns about the risk of thyroid cancer in the Marshallese population. The most serious exposures and its health hazards resulted from the hydrogen-thermonuclear bomb test, the Castle BRAVO, on March 1, 1954. Between 1993 and 1997, we screened 3,709 Marshallese for thyroid disease who were born before the BRAVO test. It was 60% of the entire population at risk and who were still alive at the time of our examinations. We diagnosed 30 thyroid cancers and found 27 other study participants who had been operated for thyroid cancer before our screening in this group. Fifty-seven Marshallese born before 1954 (1.5%) had thyroid cancer or had been operated for thyroid cancer. Nearly all (92%) of these cancers were papillary carcinoma. We derived estimates of individual thyroid dose proxy from the BRAVO test in 1954 on the basis of published age-specific doses estimated on Utirik atoll and 137Cs deposition levels on the atolls where the participants came from. There was suggestive evidence that the prevalence of thyroid cancer increased with category of estimated dose to the thyroid.
Highlights
The US nuclear weapons testing program in the Pacific conducted between 1946 and 1958 resulted in radiation exposure in the Marshall Islands
Radiological Study has provided evidence that at least ten of the inhabited atolls or reef islands have been contaminated from the atmospheric explosions to various degrees.4-6In conjunction with this assessment, we examined a large proportion of the Marshallese population potentially exposed to radioactive fallout for thyroid disease.' We previously showed that thyroid nodules were very common, in particular in female Marshallese, and that the prevalence increased with age, but we found little evidence that benign thyroid nodules were related to exposure from nuclear fallout.8-11In 2001, we published a monograph that summarized our previous findings systematically.[11]
We reported that the occurrence of thyroid cancer in Marshallese was still high in 40 years after the nuclear test and that the association between thyroid cancer prevalence and radio-iodines exposure using the data collected until the end of 2000
Summary
One objective of this study was to determine the prevalence of thyroid cancer in Marshallese people who lived anywhere in the Marshall Islands during the atomic bomb testing period , in partic-. 7,172 Marshallese people for thyroid disease during four study clinical phases of work Of this group, 5,821 were born before. Since at present no detailed assessment of individual radiation dose to the thyroid gland has been conducted for people in the study, and there is very little other information about received doses in the Marshall Islands, we based our analysis on surrogate measures of radiation dose. The only data on radiation dose from fallout in the Marshall Islands come from Lessard et al.,[1] who estimated thyroid doses for people who were exposed to radioactive fallout on Rongelap and Utirik after the BRAVO test.
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