2100p], AND 2!0Po IN TISSUES OF SOME ALASKAN RESIDENTS 126 earth's surface primarily in rainfall and are continually accumulated by the slow growing, 210Po deposited on the disc was measured in a that a major fraction of the "Pb deposited in recent years was produced in’ atmospheric time of death. long jiving arctic lichen. During this time, “Po eraws inte near racdinactive equilibrium with the "Pb. It has been sugeested, however, nuclear detonations by the reaction *°8Pb(2n,7) 210} (14a) ‘The purpose of this study was to investigate the increased tissue levels of 7!9Pb and #!°Po associated with the consumption of caribou meat. In addition, to ascertain the significance of atmospheric nuclear detonations as a source ‘of 29Ph in the arctic, the concentration of 2190p}, in recently collected lichen and caribou bone was compared with the concentration in similar samples collected before L951. Radium-226 was also measured in these older samples so that the 29P1) concentrations could be corrected for ingrowth. EXPERIMENTAL The analytical proceedure employed for the determination of ?°Ph and 7!"Po lias been described previously.4#!® “The samples were wet ashed in nitric acid and 72°% perchloric acid and the 2!©Po was deposited on a 2-in. silver disc from a 0.5 V EEG] solution containing 200 me of ascorbie acid at 84°C. The 4°Pb present was calculated from the 7!9Po ingrowth, which was measured by repeating the *!’Po deposition on another silver dise 3 & months after the initial deposition. ‘The alpha activity of the low-background (0,5-0.8 counts/hr) ZnS(Ag) scintillation counter. The initial ?!?Po values obtained were corrected for decay and ingrowth from the 2°Pb to obtain the concentration at the Any muscle attached to the bone was removed and the bones were fat extracted in anhydrous benzene. Defatting the bones was perforined in order to give a more reproducible bone sample weight,"” and it was determined that neither 2!°Pb nor 2!°Po was removed during the extraction. The average ratio of defat weight/fresh weight was 0.46 + 0.08 (S.D.) for 30 rib sainples. The “8Ra content was measured by the radon emanation method."!81 In each case, the 8Ra content was measured in the same sample used for the 7!°Pb analysis. RESULTS AND DISCUSSION Thuaman ftssies In Table | are listed the data for the Alaskan subjects from which tissue samples were obtained for analysis. The subjects are listed in the order of increasing caribou consumption, and the table includes the age, sex, residence and a bricf statement on the frequency with which caribou was eaten. Although it would be more desirable to have knowledge of exact quantities of caribou or reindeer consumed, such data was not available. Listed in Table 2 are the concentrations of 210Po and #°Pb measured in the various tissues. Table 1. Human sample data Subject number l 2 3 4 Age 6 } 15 410 MI EF 78 5 65 6 7 25 55 8 Sex 77 daskan residence Planum Caribou in diet None MM Anchorage Point Barrow and .Anchorage Eagle None Ate caribou meat regularly at Barrow, but hadlived in Anchoragethe last three years where she ate none ‘Ate caribou meat occasionally F M (near Bethel) Anchorage Kivalina Ate caribou meat once or twice a month Caribou meat was main diet in winter—fish in summer NI M Akiak Royuk A few times a year A steady diet of rerndeer meat, but ate none during terminal illness of 3 months