i i | Marshallese children appears similar, on a risk per rad basis, to that in the x-raved children studied by Hempelmann. !97.109 Risk for thyroid cancer in the Rongelap people is also similar to that reported for other populations. The data in Table 25 indicate that at the dose levels involved there ts a correlation between inci- dence of thyroid lesions and the estimated dose to the gland. Onthe basis of the incidence per rad in the high exposure Rongelap children, about 2 children with adenomas would be expected in the Ailingnae group, where ? were noted, and 4 in the Uuirik group, where none was found. The lower effectiveness per rad in the Utirik children maybe Table 33 : rw ee ne ee ‘ ‘ 29 Percent [Incidence of Thyroid Lesions (20 Years Observation) Age at exposure <€10 yr Group Benign Rongelap > 10 yr Cancer 84.2 Ailingnae 33.3 X-raved children (17 yr)197 28.0 Rongelap & Ailingnae Utirik X-rayed children, low dose (17 yr)10? Marshallese controls 3.3 0.0 United States}? 4.0 0.0 3.0 0.13 4.3 1.8 x 10-5 (all ages) Ii 4.4 15.8 5.1 3.5 1.0 0.0 5.4 2.5 X 10-5 (all ages) 0.36-1.7 Cancer 33.3 76.0 0.0 1.0 Worldwide av.108 Benign 1.8 x 10-5 (all ages) 2.5 * 10-5 (all ages) 0.5-1.6 Table 34 Risk* of Radiation-Induced Thyroid Lesions (Cases per 108 man-years per rad) Age at exposure < 10 yr Group(years follow-up) Dose range, rads (type) > 10 yr Benign Cancer Dose range, rads Benign Cancer 379 135-190 327 31 10.5 16.1 ‘225 89.2 7.0 0 6.4 17.8 Rongelap (20) Ailingnae (20) Rongelap & Ailingnae (20) Uuirik (20) 710-1150 (18,7) 280— 450 (I, y) 280-1150 (18,y) 60- 95 (IB, y) 41.9 43.6 42.1 2.6 0 2.3 0 Rochester (17)197 335 (av.) (x rays) 64.0 3.5 Ann Arbor (17)!97 20 (av.) (x rays) Beach & Dolphin (20)!3 (x rays) UNSCEAR(17)!4 100- 300 (x rays) ABCC (20)!91 20-1000 (y, 7) ABCC (20)102 <20 (y,7) 24.0 2.2 1.7 0.5-15 1.3 (all ages) 0.2 (all ages) *Risk is calculated from the equation Risk = No.of cases x 106 ~ dose x years at risk ’ or, alternatively, . No.of cases x 10 Risk = ‘ = =“ oa oo . ° a 28. caetl No. of subjects X mean dose x mean No.of years atrisk ™=. Both equations give almost identical results for the Marshallese because of the uniformity of the data. No correction has been madefor expected numberofcases because the expectation among unexposed subjects is too lowto affect the results (see Table 33).