From the above data of Lessard and Greenhouse the highesc estimated aver- age accumulated dose equivalents to the thyroid glands. includiag that from background, due to residual radiation exposure (from both external and internal sources) for individuals living full time on Utirik since 1954 and on Rongelap since 1957 were, respectively, 16.3 rem and 4.49 rem. The dose equiv- alents from 652m calculated for the Utirik people (acquired largely in the first year or two) were probably considerably higher than those actually received because these people subsisted to a great extent on food subsidies during the first few years after the accident. Also, the unexposed people returning to live on Utirik probably received lower doses than calculated because they generally arrived on the island at a later date than did the ex- posed people. [It should be pointed out that the Marshallese visit other atolls for varying periods of time, and this would tend to reduce their exposure. Questioning of the inhabitants brought out that they may spend as much as half their time away from their home atoll. Even though personnel monitoring at Rongelap and Utirik included some people who may have returned recently and would therefore have had somewhat lower body burdens of radionuclides at that time, this factor is not considered to reduce the average dose equivalent estimates of the resident population greatly because the majority of the people tested had been living on the island for several years or more. However, in view of the estimate of halftime habitation on the home islands, it does not seem unreasonable to assume that the total average dose to the population from residual radiation might be about half of what it would have been with full-time residence. It was not considered necessary to add the exposure from natural radiation acquired while away on other atolls since the Marshallese populations are to be compared with unexposed populations in whom such exposure is inherent.* Since most of the data on radiation effects in human beings are based on acute exposures, with uncertainty regarding the degree of reduced effectiveness of low-dose chronic radiation exposure, no attempt has been made at this time to add the early and residual dose equivalents in the exposed Marshallese. C. Bikini Dose Estimates Greenhouse et al. (223) have calculated the total dose equivalent to the Bikini inhabitants from both external and internal sources, and these data are summarized in Table 7. They state that "...for residence periods between the years 1969 and 1978 these figures evince a maximally exposed person receiving a whole~body dose equivalent and commitment of 3 rem, and a population average dose and comsitment of 1.2 rem from man-made radioactivity on Bikini Island." The levels were so low that quantification was difficult. The levels did not appear to be much higher thannoted in other world populations. *For purposes of comparison, the estimated whole-body doses are not very different from those received by the average U.S. citizen (4S rem in 25 yr) or by an inhabitant of Denver (some 7 rem in 25 yr). People living on the monozite ponds of South America or India probably receive even greater doses than the Marshallese. - 119 -