The accumulation of data from these surveys 1s becoming increasingly voluminous. Since conditions have not been favorable for performance of . extensive statistical analyses or use of electronic computing procedures to store and manipulate the data, the annual survey reports published by this Laboratory are made as complete as possible. This report, therefore, includes a considerable amount of raw data, much of it in appendices, so that others may have an opportunity to make further calculationsif desired. This report also contains a brief addendum on the vegetation of Rongelap Island. ’ DOE ARCHIVES Summaryof Past Findings Reports have been published on the findings of surveys made at the following times after expo- sure: tnitial examination,’ 6 months,’ 1 year,’ 2 years,‘ 3 years,®> and 4 years.* The following isa brief summary of the findings previously reported. During the first 24 to 48 hr after exposure, about % of the Rongelap people experienced anorexia and nausea. A few vomited and had diarrhea. Many also experienced itching and burning of the skin, and a few complained oflachrymation and burningof the eyes. Followingthis, the people remained asymptomatic until about 2 weeks after the accident, when cutaneouslesions and loss of hair developed, due largelyto beta ir- radiation of the skin. It was apparent when the people were first examined, a few days after exposure, that the lymphocytes were considerably depressed and thatsignificant doses of radiation had probably been received. In addition to the wholebody dose of radiauon and the beta irradiation of the skin, radiochemical analyses of the urine showed that measurable amountsof radioactive material had also been absorbed internally. The effects of the radiation can best be summarized under three headings according to the modeof exposure: penetraung irradiation, skin irradiation, and internal irradiation. PENETRATING IRRADIATION The changes in the peripheral blood of the more heavily exposed Rongelap people who received 175 r will be reviewed in the section on hemato- logical examinations (see Figures 33, 35, and 38, and Appendices 1 and 2). The changes in the Ailingnae and Uturik groups were similar but bess marked. Certain unexplained fluctuations have occurred from year to year in the peripheral blood levels of the comparison populations as well as of the exposed groups. Depression of the peripheral blood elements as represented by mean populauion levels occurred as follows. Lymphocytes fell promptly and bythe third day were about 55%of the control values in adults, and slightly lower in children, There was only slight recoveryafter six months. At 2 years, although further recovery was evident, the mean values of these cells werestill found to be below the comparison population levels (75 to 80%). At 3 years the mean lymphocyte counts wereslightly below those of the comparison population. At 4 years the mean level appeared to be aboutthe same as that of the comparison population, but many counts remained lower. Neutrophil levels fluctuated considerablyduring the first few weeks but fell gradually to a low of about 50% of comparison population levels by the 6th week after exposure. Slow recovery en- sued, but at 6 monthsthey werestill slightly below the unexposed levels. However, by | year post ex- posure they had returned to the level of the com- parison population and have remained so, with the possible exception of those of children <12 years old, which generally have been lower than those of the unexposed children of comparable age. Platelets fell to about 30% of the unexposed values by the 4th week. By 6 months they had reached 70% of the controls; at | year the mean platelet count was still belowthat of the control population but higher than at the 6-monthsurvey. Althoughfurther increases were apparent at the 2-, 3-, and 4-year examinations,the levels were still belowthose of the comparison population. Changes in hematocrit were not remarkable in anyof the groups. Clinical examinations revealed no disease proc- esses or symptoms which could be attributed to radiation effects, aside from skin lesions, Joss of hair, and early symptoms. Epidemics of chicken pox and measies occurred. The diseases encountered were no more severe or frequentin the irradi- ated group than in the unexposed group, even during the period of greatest depression of periphera] blood elements. Three persons in the exposed population died of disease: (1) a 46-year-old man with a hypertensive heart disease which had been