at tb TT a | L Oo ! L y : 4 PREVALENCE (cases/100 pereons) a oa a v Tv T TT A TUNgRIOGE O vanoer © MORTENSEN O TRowsRIDeE VW RALLISON jaf 10 20 Jj 30 40 i $0 60 70 | 80 ! go «6100 AGE (yeers) Fig. 1. Prevalence of spontaneous thyroid nodules. From Maxon et al. (164). The data in Table 4, taken from a Nuclear Regulatory Commission Report (234), summarize the estimated occurrence of thyroid neoplasms in the general U.S. population compared with data on the Marshallese comparison population. In the Marshallese comparison population, as in other unexposed populations, the preponderance of thyroid nodules is in the older age group, whereas in the exposed Rongelap people the reverse is true. This appears to be the case in other exposed populations also.* About 1300 children living in Utah vere exposed to fallout from the Nevada tests in the 1950s (181), receiving doses estimated to be considerably higher than those to the Marshallese control populations, and they had no detectable increase in thyroid abnormalities compared with the unexposed populations in Arizona. Table 4. Age 0-19 20-39 40-59 60-80 grou Prevalence of thyroid nodules and cancer in unexposed Marshallese and U.S. populations. Prevalence of nodularity (2) Prevalence of cancer (2%) U.S. Marshallese U.S. Marshallese 0.8 2.6 2.6 0.08 0.31 0.9 4.3 6.1 7.9 0.52 0.73 0.7 *The slightly higher prevalence of nodules and carcinoma may be related to the more rigorous examinations given that group compared with reported surveys of other world populations. han - 108 -