Iron-55 in Northern Sweden; Relationships and Annual Variation from 1956 Until 1967 in Lichen and Reindeer As Well As Uptake and Metabolism in Man

Abstract

The ⁵⁵Fe activity from nuclear weapons debris have been investigated in lichen, moss, reindeer and man. Lichen and moss were collected from 1956 until 1966 at different places in the world. After the nuclear weapons tests of 1956–58, the activity of ⁵⁵Fe in lichen was about 10 nCi/kg dry weight. The activity increased rapidly after the high yield events in 1961 and 1962 and reached a maximum value of about 100 nCi/kg dry weight. Reindeer meat samples were collected from 1961 until 1967 at Funasdalen in northern Sweden. There seems to be a seasonal variation of the ⁵⁵Fe activity in reindeer meat similar to that of ¹³⁷Cs. The maximum values reached in April 1965, 1966 and 1967 were about 400 nCi/kg dry weight. The biological halftime of iron in reindeer was estimated to be about 150 days. The body burden of ⁵⁵Fe was estimated by analyzing blood samples from Lapps and non-Lapps. No significant seasonal variation of the ⁵⁵Fe activity was found. The biological halftime of iron was also estimated. The average annual absorbed dose to the red blood cells during 1965–67 was estimated to be 5 mrad for female Lapps and 2.5 mrad for male Lapps. Because of the high iron concentration in the iron storage proteins, ferritin and haemosiderin, their annual absorbed dose in female and male Lapps was about 800 mrad and 400 mrad respectively. The absorbed dose to be received by the year 2000 from ⁵⁵Fe released in the major periods of nuclear weapon testing 1954–60 and 1954–62 was estimated.