Gs-1357 ISS? — Zn-68 $1-90 ¢ G001) RETURN TO RONGELAP . 958 959 137] ' | sr-90 (.002) a sill OPERATION REOWING of the Cs'* ’g K in the entire Marshallese popula- tion suggests that the Cs**’ level, like the K’" level. is proportional to the lean body weight. The mean Cs'** body burden of the Rongelap adult males (14.7 mypC/kg) was 300 times the mean of that of the medical team carrying out the study(9.048). The levei of Cs'* in the world-wide population in July 1961 appears to have declined from the maximum level observed in 1959. The average value for Cs'"* measured in BNL person- nel, for example, declined from 59 puC’g Kin f J sr-90 1 0055: | | 20-658 Sr -90 1.0069) Co -60 OG. rium with the levels of Cs'* in the diet (although this is a difficult point to ascertain). The uniformity ] | June 1960 to 30 in December 1961. The body burdens of the Marshallese will. of course. also be affected bv this world-wide fallout as well as by the fallout released in the series of tests carried out by the USSR in October 1961. As the accumula- 2.2 0.3 0.4 95 0.6 0.7 tion is gradual both in the environment, as world- The levels of radioactive contamination ap- wide fallout settles out. and in the human body, via the ingestive route, it will be a number of months before a clear picture emerges. However, after the moratorium of 3 vears, during which time the Cs'** levels had an opportunity to stabilize, it will be clear what the direct results are of that particularseries oftests. sex apparently do not influence significantly the deposition of these radionuclides. Wide variations weight of the Marshallese does not differ significantly between the exposed and unexposed groups. nor doesit differ on the basis of sex or age. How- pee Figure 58. Estimated bodyburden of isotopes in Rongelap people at various times since 1954. Values obtained either by gamma spectroscopy or by radiochemical urine analyses. peared to bé about the samefor juveniles as for adults. for men as for women. Factors of age and in the level of contamination appear among individuals of all groups, as might be expected when the source of the contamination is via ingestion. Even with a fairly limited diet, individual tastes maydictate great differences in the food consumed. As for the time course of the contamination in the population as a whole, it is necessary to consider each radioisotope individually, as to source of supply and discrimination of the soil, plant and animal life, and the human bodyfor each isotope. The mean Cs'"* body burden of the Rongelap adult males is 14.7 muC/kg as compared to 14.1 in 1959. Thus, no significant change has occurred in the past 2 years. These Cs'** body burdens of the Marshallese result from the relatively high dietary intake through foodstuffs produced in the Marshallese environment. Theyreflect the level of residual fallout on the island, and also the higher uptake and retention of Cs'* by food plants grown in a K-deficientsoil. It appears that the bodyburden of Cs‘** has reached an approximate equilib- The mean Zn” concentration per kg body ever, the mean was generallyslightly higher among adults than in juveniles, and higher among aduit males than adult females. In the period 1959-1961 the value of Zn*’ body burden dropped bya factor of 6. The value of Zn*’ in male adult Marshallese dropped from 9.9 muC/kg bodyweight in 1959 to 1.51 in 1961. No clear reason emerges as the basis for this drop, although it is possible that dietary variation may be responsible.It is known that the source of Zn*”’ in these people is from fish. which selectively concentrate this element. Theretore. it is possible that the decrease in Zn”? levels noted mavbe due to the fact that the people are eating more canned meats in place of fresh fish. If the Zn”' intake in the diet had decreased radically during that period, the observed fall in the level of internally-deposited Zn" would be consistent with the effective half-life of Zn”’, which is =120 days.'* The evidence that could be obtained on this subject is insufficient to make anv conclusive statement, however.