ti Residual Skin Lesions Aging Studies On recovery of acute beta burns some 20 exposed Marshallese continued to show residual scarring, atrophy, and pigment changes, and biopsy studies revealed residual microscopic Aging studies have been included in several annual surveys to detect the possible influence of radiation on development of prematureaging. In the earlier studies various parameters usually as- changes. However, at no time have any of the le- sions developed into chronic radiation dermatitis or shown any evidenceeither grossly or histologi- cally of malignant change. An increased number of benign pigmented maculae and moles have been notedin previously irradiated areas of the skin, particularly in the neck region. Hematological Findings Mean peripheral blood counts in the Marshallese exposed group have tended to remain below those of the unexposed group followingtheinitial acute depression. A slight degree of depression of white cells and platelets has consistently persisted (Figure 41). This implies a residual radiation effect on the bone marrow. Other evidence in support of this was the finding, on bone marrow examination of some of the exposed people, of an alteration in the myeloid-erythroid ratio (increased red cell precursors), presence of cells with abnormal chroma- tin material and double nuclei, and also increased mitosis. Examination of peripheral blood smears revealed increased numbers of atypical lymphocytes in the exposed group and an unexplainedincrease in these formsin the children of exposed parents. Also, chromosomestudies of lymphocytes in cultured peripheral blood at 10 years post exposure revealed a high incidence of aneuploid cells and 2-hit aberrations in the blood of the exposed group. Dental Findings Dental examinations showednosignificantdifferences in caries rate between exposed and unexposed groups. However, the incidence and severity of peridontal disease was slightly greater in the exposed group.It is not known whetherthis finding is related to radiation exposure. The poor oral hygiene generally observed in the Marshallese resulted in a high caries rate in the teenage chil- dren, severe peridontal lesions in the adults (heavy calculus andloss of alveolar bone), and edentulous mouthsin the aged. Radiation exposure did not appear to have affected developing dentition in the exposed children. sociated with aging were measured at the time of physical examination. The values of someof the parameters were estimated and scored on a 0 to 4+ scale (such as graying of the hair, senile changesof theskin, balding,etc.), and the values of others were measured (skin looseness, skin elasticity, accommodation ofthe eyes, visual acuity, arcussenilis, hearing, blood pressure, neuromus- cular function, hand strength, vibratory sense, neuromuscular reaction time, body potassium by spectrographic analysis, etc.). Comparison of these values in exposed and unexposed individuals of the same age showed no apparentdifference. Most of the measurements showed varving degreesof correlation with aging. A biological age score was calculated for individuals and groups by use of an average percentage score. During the 1967 and 1968 surveys the age-related and/or radiationinduced agingeffect on immunological competence was tested in 100 unexposed and 50 exposed people (Figures 34 to 37). In the unexposed group decreasing immunological competence with aging was indicated by decreasing percentage transformation of peripheral blood lymphocytes by phytohemagglutinin stimulation, indicating decreasing immunological competence of lymphocytes; and by significantincrease in gammaglobulin, reflected also in increases in IgG and IgA immunoglobulins and light chains. Theselatter findings were believed to be associated with age-accumulated effects of repeated infections and perhapsalso with increased autoimmunereactions. The irradiated population exhibited certain significantdifferences from the unexposed population which mayindicate radiation effects. They had relative depression of platelet and neutrophil levels of the peripheral blood. As pointed out before, some slight degree of depression of peripheral blood elements has, however, been noted since exposure. Compared with the unexposed population the exposed group was also foundto havereduced gammaglobulin levels (including IgG, IgA, and light chains on immunodiffusion analysis), more pronouncedin older age groups, which may indicate a radiation-induced agingeffect. Evidence, however,for relative loss of immunological capac-