39 Marshallese children appears similar, on a risk per rad basis. to that in the x-raved children studied by Hempelmann. 107-109 Risk for thyroid cancerin the Rongelap people is also similar to that reported for other populations. The data in Table 25 indicate that at the dose 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 2 were noted. and 4 in the Utirik group, where none was found. The lower effectiveness per rad in the Utirik children may be levels involved there is a correlation between inci- Table 33 Percent Incidence of Thyroid Lesions (20 Years Observation) Age at exposure <10 yr Group Benign Rongelap > 10 yr Cancer 84.2 Ailingnae Rongelap & Ailingnae Utirik 3.3 33.3 76.0 0.0 X-rayed children (17 yr)!0? X-rayed children, low dose (17 yr)'07 33.3 15.8 3.1 1.8x 10-5 (all ages) 2.5 « 10-5 (all ages) 5.4 4.3 0.13 1.0 0.36-1.7 Cancer 11.1 0.0 4.0 0.0 28.0 3.0 Marshallese controls Worldwide av. 108 United States? Benign 4.4 0.0 3.5 1.0 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 10® man-vears 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 10.5 151.1 22.5 89.2 7.0 0 6.4 17.8 Rongelap (20) Ailingnae (20) Rongelap & Ailingnae (20) Ctirik (20) 710-1150 (IB,y) 280- 450 (I8,y) 280-1150 (IB, y) 60- 95 (18, y) 41.9 43.6 42.1 0 2.6 0 2.3 0 Rochester (17)!07 Ann Arbor (17)!97 Beach & Dolphin (20)!23 UNSCEAR (17)124 335 (av.) (x rays) 20 (av.) (x rays) (x rays) 100— 300 (x rays) 64.0 24.0 55 2.2 1.7 0.5-15 ABCC(20)19! ABCC (20)191 ~ 20-1000 (y, 7) <20 1.3 (all ages) (y, 1) 0.2 (ali ages) “Risk is calculated from the equation . No. of cases x 108 Risk = ~————___—___- , or, alternatively, dose X years at risk No. of cases x 108 Risk = No. of subjects X mean dose x mean No. ofyears atrisk’ Both equations give almost identical results for the Marshallese because of the uniformity of the data. No correction has been madefor expected number ofcases because the expectation among unexposed subjects is too low to affect the results (see Table 33).