28 those >>35, exposed and unexposed, werefree of clinically detectable peridontal disease. In the aged, many of the remaining teeth were simply held in position by the gingival attachment. Almost all the Rongelapese exhibited marked xerostomia. The oral mucosa felt damp butnot wet. During the dental examination, manipulation of the tissues by mouth mirror and explorer failed to stimulate the flow of saliva. For pH readings, the paper strip had to remain in contact with the floor of the mouth for 25 to 30 sec in orderto absorb sufficient saliva. In most instances it was difficult for the subject to produce the 5 mlof saliva necessary for pH determination in a period <(10 to 15 min. The fH values ranged from 6.0 to 7.5, with an average of 6.3 Utirik Population The Utirik population exhibited oral findings similar to those of the Rongelapese. Their standards of oral hygiene were somewhatsuperior, but the incidence of peridontal disease and caries in adults was practically identical. In the Utirik children less evidence was seen of bunchingofthe lower anterior teeth, and jaw developmentwasin harmony with general body growth. Conclusions These examinations led to the following con- clusions. 1. There was no significant difference in either caries rate or incidence of peridontal disease between the exposed and the unexposed people of Rongelap. Thelevel of oral hygiene appeared to be somewhatbetter in the children examined at Majuro and at Utirik, but the incidenceofcaries wasaboutthe samein the two groups, and higher than in the Rongelapese children. 2. The poor oral hygiene generally observed in the Marshallese people had its usual results: a high caries rate in teen-age children; severe peridontallesions in adults (heavy calculus, loss ofalve- olar bone); and edentulous mouthsin the aged. _ 3. No difference was perceptible in the clinical appearanceof developing dentition amongtheexposed children, the nonexposed, and those born to irradiated parents. STUDIES OF AGING CRITERIA The results of aging criteria studies are plotted in Figures 13 to 31. Individual readings are plotted Foe roy mms = CONT eu Fl uo (open circles, exposed people; closed circles, unexposed people) to show the spread of the data, and the mean valuesare also plotted (squares) for each 5-year age group with exposed and unexposed people combined. Thetrend of each criterion with increasing age is representedby a line of approxi- mate best fit by eye. The values of the criteria generally either increase or decrease with increas- ing age. Many changes, such as greving of the hair, balding, arteriosclerosis (peripheral and retinal), and skin looseness and retraction, are not appeciably manifest in the Marshallese until after age 35 to 40. There is a tendency for values of criteria such as blood pressures, greying of the hair, loss of visual acuity, and accommodation to level off, or even to show slightly reduced values in the oldest groups. The numberof people in these groups is too smal! to make this observation certain. However, American statistics on blood pressure (systolic and diastolic) also show a plateau effect beyond about 60 years of age and evena slight tendency to lowering of blood pressures be- yond this age.*® By the age of 65 to 70, arcus senilis in all Marshallese showed a 4+ change and, therefore, the plateau was at a maximum. Some curves showed lower maxima. For example, baldness in women showedonly a 35% maximum, and arteriosclerosis of the retina only 45%, The differences in maxima probably were due largely to differences inthe degree of change associated with the various criteria but also partly to the arbitrary nature of the scoring. The sexualdifferences in hand strength and baldness were expected. In the neuromuscular functiontest, slight muscle fatigue may have been a factor in the lower female scores, necessitating separate evaluation. ee) Tod 100 TT re so ae | I ~ o= EXPOSED «= UNEXPOSED °=MEAN BOTH GROUPS ete | I9g 90 80} 70 67s ~, 00 (sec) 50 45 40} 30 =| io! 20 225 . 30 . 40 50 60 AGE-YRS 7O 80 Figure 13. Skin retraction time, 1958-1959.