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.