Sodium-22 in the food-chain: lichen-reindeer-man

The 22Na-content of samples of lichen, reindeer-blood, -flesh and -bone collected between 1961 and 1969 in the area of Funasdalen in central Sweden (62.5°N, 12.5°E) have been measured by means of a sum-coincidence gamma-spectrometer. After the thermonuclear detonations in 1961 and 1962, the radioactive concentration of 22Na in reindeer-flesh rose rapidly from about 1–10 pCi per kg to a maximum value of 200 pCi per kg wet weight in late 1964. Early in 1969 the same value had decreased to 25 pCi per kg wet weight. The radioactive concentration of Na in reindeer-bone reached a maximum of 600 pCi per kg wet weight in mid-1965. The biological half time of sodium incorporated in reindeerbone was estimated to be about 0.5 yr. Analyses of y-spectra from the annually performed whole-body measurements on Lapps give a 22Na-body burden of less than 2 nCi at the time of assumed maximum. The presence of 22Na in the food-chain: lichen-reindeer-man has given a small contribution to the absorbed dose in man in comparison to many other bomb-produced and naturally occurring radionuclides.