30 malignanciesis well documented,®*">5 but that with other less well-defined aging criteria is not clearcut. Beebeet al.,°° reporting on 1300 deaths from 1950 to 1966 among 8200 exposed Japanese, stated: “Once canceris removed from the list of natural causes, mortality appears to bear no relauon to radiation dosage. In none of the 4tume periods is there evidence of general increase in mortality that one might expect from the hypothesis of accelerated aging.” Since the underlying mechanismsof ordinary aging are not clearlydefined, it is dificult to compare radiation effects with the aging process and to recognize their interaction. Studies of longevity in the relatively small Marshallese population under observation do not provide anyevidence of a possible life-shortening effect of radiation. At this 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 Utrrik people. The differences are not significant. Numerousempirical studies concerned with possible radiation-induced aging effects have been carried out on the Japanese survivors°?5§ and on the Marshallese.8.12.13.57-61 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, arcussenilis, senile changestn the skin, balding, etc., but most involved direct measurementsof items such as skin loose- ness, skin elasticity (skin caliper), visual accom- modation, visual acuity, hearing (audiometric), blood pressure, neuromuscular function (light extinction test), hand strength (dynamometer), vibra- tory sense {vibrometer), and lean body mass (whole-body potassium by gammaspectrographic analysis). Comparison of these values in the exposed and unexposed Marshallese (Table 17) showed nosignificant 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 immunologi- cal statusof individuals soon after exposure if the dose is sufficient to producesignificant leukopenia. During the early pertod, though the acute effects on the Rongelap people included considerable depression of peripheral blood elements, comparison of the incidenceofinfections with that in the Utirik group gave no evidence of impaired immunity. Reduced immunological reserve maylikely bea late effect of radiation exposure,®? but it has not been observed conclusively in man. The development of leukemia and other malignancies following exposure may quite possibly be related to re- Table [7 Correlation of Criteria With Age and Radiation Exposure]? Correlation with age (r value) Grayness 0.87 Correlation with radiation Percent +17.0 Significance* ( p) N.S. (0.70) Arcus senilis Accommodation 0.83 0.81 0.0 —14.1 N.S. (1.00) NS. (0.11) Skin looseness 0.70 + N.S. (0.82) Skin retraction 0.74 + 7.3 N.S. (0.68) 1.6 Vibratory sense (M + F) Visual acuity Hearing less Hand erip (M+F) Reaction time (M+ F) (light extinction test) 0.70** 0.69 0.67 0.67** 0.64** — 1.4(M), +24.6 (F) +14.0 + 79 + 13.8 (M), +13.8 (F) ~ 2.0(M), —10.5 (F) N.S. N.S. N.S. N.S. N.S. Potassium (M+ F) 0.41** — 14.6 (M), + 10.6 (F) N.S. (0.17, 0.22) + 7.0 N.S. (0.27) Systolic blood pressure 0.355 Cholesterol Neuromuscular function (M + F) (hand tally) Combined scoret *N.S. - not significant at 5% level. 0.39 0.36** 0.99 ~—115 —17.2 + 3.2(M), +11 (F) **y values for males and females averaged. (0.90, 0.20) (0.59) (0.40) (0.15, 0.18) (0.88, 0.55) NS. (0.30) N.S. (0.05) N.S. (0.85, 0.95) tWeighted accordingto r value.