29 Marshallese children appears similar, on a risk per rad basis, to that in the x-rayed children studied by Hempelmann.!07.109 Risk for thyroid cancer in the Rongelap people is also similar to that reported for other populations. The data in Table25 indicate that at the dose levels involved there is a correlation between inci- dence of thyroid lesions and the estimated dose to the gland. On the 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, and4 in the Uuritk group, where none was found. The lower effectiveness per rad in the Utirik children may be Table 33 Percent Incidence of Thyroid Lesions (20 Years Observation) Age at exposure <10 yr Group > 10 yr Benign Cancer Benign Rongelap Ailingnae Rongelap & Ailingnae 84.2 33.3 76.0 3.3 0.0 4.0 11.1! 33.3 15.8 X-rayed children (17 yr)19 X-rayed children, low dose (17 yr)!07 28.0 3.0 Utirik Marshallese controls Worldwideav. 108 United States!9? 0.0 0.0 1.0 1.8 10-5 (all ages) 2.5 & 10-5 (all ages) 4.4 0.0 3.3 3.1 4.3 0.13 0.36-1.7 Cancer 1.0 5.4 1.8 x 10-5 (al! ages) 2.5 K 10-5 (all ages) 0.5-1.6 Table 34 Risk* of Radiation-Induced Thyroid Lesions (Cases per 106 man-years per rad) Age at exposure < 10 yr Group (years follow-up) Dose range, rads {type) > 10 yr Benign Cancer 710-1150 (18,7) 41.9 2.6 Rongelap & Ailingnae (20) 280-1150 (If, y) 42.1 Rochester (17)!97 335 (av.) (x rays) Rongelap(20) Ailingnae (20) 280- 450 (18, y) Utirik (20) 43.6 60- 95 (1B, y) Ann Arbor (17)107 0 64.0 20 (av.} (x rays) Beach & Dolphin (20)123 24.0 (x rays) UNSCEAR(17)224 100- 300 (x rays) ABCC(20)101 <20 379 Benign 10.5 Cancer 7.0 0 135-190 151.1 0 0 31 892 178 2.3 327 22.5 6.4 5.5 2.2 1.7 0.5-15 20-1000 (y, 2) ABCC (20)!01 Dose range,rads 1.3 (all ages) (y,n) 0.2 (all ages) *Risk is calculated from the equation . No. of cases & 108 Risk = ~———_—___—"__ , dose x years at risk or, alternatively, Risk = No. of cases « 106 No. of subjects x mean dose x mean No.of years at risk" Both equations give almost identical results for the Marshallese because of the uniformity of the data, No correction has been made for expected numberof cases because the expectation among unexposed subjects is too low to affect the results (see Table 33}.