Abstract
Abstract Natural 226 Ra and 228 Th are concentrated in occasional cattle thyroids until the concentration has exceeded 10 times that found in bones of the same animals. These alpha emitters with their radioactive daughters have been found by gamma spectroscopy in less than 1 per cent of cattle from the U.S.A. and 10 per cent of cattle from the endemic goitre area of Colombia, South America. Recently, we have found that more than 80 per cent of thyroids from 103 cattle from Nigeria contained easily detectable quantities of 228 Th, possibly mixed with 226 Ra. Radioautographs of these thyroids revealed highly concentrated sources of alpha particles distributed throughout the thyroid. Measurements of the alpha tracks suggest that each 6·5-MeV alpha particle produces 9000 rad along its track and many of these tracks transverse thyroid cells. Therefore, the normal bovine thyroid can concentrate natural radium and this may constitute a source of some “naturally occurring” thyroid disease.
Published Version
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