V. A. AGING, IMMUNOLOGICAL, CHROMOSOME, AND GENETIC STUDIES Aging Studies Numerous empirical studies concerned with possible radiation-induced aging effects have been carried out on exposed Rongelap people (8,11-15), similar to those carried out on the Japanese survivors (56-63,207). On several occasions Rongelap people were given a battery of nonspecific tests for aging (9,12,13). 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 changes in the skin, balding, etc., but most involved direct measurements of items such as skin looseness, skin elasticity, visual accommodation, visual acuity, hear- ing (audiometric), blood pressure, neuromuscular function (light extinction 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 showed no significant differences. The biological age scores (average percent score) for the two groups are about the same. Aging studies also resulted in negative findings in the Japanese survivors, and they have not been pursued in the Marshallese during the past 5 years. Beebe et al. (63), from mortality studies of the Japanese exposed to the atomic bombs, report that they do not find support for the belief that diseases other than cancer are involved in the late mortality effect and that "to the extent that the hypothesis of accelerated aging requires that radiation increase mortality from disease generally, these findings cast doubt upon that hypothesis." B. Immunological Studies A number of empirical studies for possible radiation effects on immuno- logical status have been carried out on the Rongelap people in past years (6,8, 11-15, 30-32), similar to those conducted on the Japanese survivors. These studies were reviewed in the 20-year report (1) and may be briefly summarized as follows: * Neither the acute depression of blood elements nor delayed recovery of these elements was reflected in any apparent increased susceptibility to disease. * At 3 years post-exposure, tests of antibody response to tetanus toxoid showed no significant difference between the exposed and unexposed people (6). * Assays for immunoproteins showed increased levels of gamma globulins (particularly the IgG moiety) with increasing age but no differences between exposed and unexposed people (30). * Lymphocyte function as measured by response to phytohemaglutinin (PHA) stimulation, and acetylation of histones in lymphocyte nuclei, both showed decreases with aging but no radiation effects (30,64). * Chromosome counts in PHA-stimulated lymphocytes showed hyper- and hypo-diploid changes in certain age groups that may have been related to radia- tion exposure (32). mA -32-