30 malignancies is well documented,°?-55 but that with other less well-defined agingcriteria is not clear- cut. Beebe et al.,55 reporting on 1300 deaths from 1950 to 1966 among 8200 exposed Japanese, stated: “Once cancer is removed from thelist of natural causes, mortality appears to bear norelation to radiation dosage. In none of the 4 time periods is there evidence of general increase in mortality that one might expect from the hypothesis of accele. ated aging.” Since the underlying mechanismsof ordinary aging are not clearly defined, it is difficult to com- pare radiation effects with the aging process and to recognize their interaction. Studies of longev- ity in the relatively small Marshallese population underobservation do not provide any evidence of a possible life-shortening effect of radiation. Atthis time the average age at death in the Rongelap exposed groupis 64 years compared with 65 in the unexposed population, and 61 among the unexposed Utirik people. The differences are not significant. Numerous empirical studies concerned with possible radiation-induced aging effects have been carried out on the Japanese survivors®?-56 and on the Marshallese.5-12.13.57-61 On several occasions Rongelap people were given a battery of nonspecific tests for aging similar to those used in the Japanese studies.8.12.13 Some of these tests were based on subjective assessment, on a 0 to 4+ scale, of items such as greyness of hair, arcus senilis, senile changesin the skin, balding, etc., but most involved direct measurements of items such as skin looseness, skin elasticity (skin caliper), visual accommodation, visual acuity, hearing (audiometric), blood pressure, neuromuscular function (light exunction test), hand strength (dynamometer), vibratory sense (vibrometer), and lean body mass (whole-body potassium by gamma spectrographic analysis). Comparison of these values in the exposed and unexposed Marshallese (Table 17) showednosignificant differences. The biological age scores (average percentscore), plotted in Figure 23 for both groups, are about the same. 5. Immunological Studies Radiation is known to impair the immunological status of individuals soon after exposureif the doseis sufficient to producesignificant leukopenia. During the early period, though the acute effects on the Rongelap people included considerable depression of peripheral blood elements, comparison of the incidenceof infections with that in the Utirik group gave no evidence of impaired immunity. Reduced immunological reserve maylikely be a late effect of radiation exposure,®? butit has not been observed conclusively in man. The developmentof leukemia and other malignanciesfollowing exposure may quite possibly be related to re- Table 17 Correlation of Criteria With Age and Radiation Exposure! Correlation with age (r value) Grayness Arcussenilis 0.87 0.83 Correlation with radiation Percent +17.0 0.0 Accommodation 0.81 —141 Skin looseness” 0.70 + 16 Skin retraction 0.74 Vibratory sense (M + F) 0.64** 0.55 — 2.0(M), —10.5 (F) ~115 0.39 0.36** —17.2 + 3.2(M), +1.1 (F) Potassium (M +F) 0.417" Combined scoret “N.S. - not significant at 5% level. ; — 1.4(M), +24.6 (F) 0.69 0.67 0.67** Cholesterol Neuromuscular function (M + F) (handtally) + 73 N.S. (0.70) NS. (1.00) 0.70** Visual acuity Hearing loss Hand grip (M+F) Reaction time (M + F) (light extinction test) Systolic blood pressure Significance* ( p) 0.99 N.S. (0.11) N.S. (0.68) N.S. (0.82) NS. (0.90, 0.20) + 14.0 + 7.9 +13.8(M), +13.8 (F) N.S. (0.59) N.S. (0.40) N.S. (0.15, 0.18) —14.6(M), +10.6(F) NS. (0.17, 0.22) + 7.0 NS. (0.27) **, values for males and females averaged. N.S. (0.88, 0.55) N.S. (0.30) N.S. (0.05) N.S. (0.85, 0.95) *Weighted accordingto 7 value.