Long-life Radioactivity in Occasional Thyroids

Abstract

IN January and February 1964 radioiodine-131 in cattle and sheep thyroids of the northern hemisphere reached the lowest concentrations (< 0.5 µµc./g) and for the longest time in the past 10 years (see ref. 1 for previous results). The lack of interference by iodine-131 and improved instrumentation have permitted γ-spectroscopy of small amounts of long-life radioactive substances in thyroids and some of these could mistakenly be considered iodine-131. In the first two months of 1964, 1–10 per cent of 520 cattle thyroids were detectably radioactive; the glands were received, unselected, from slaughterhouses in several countries, and the sources reported here were (number radioactive/number not detectably radioactive): Cali, Colombia (10/95); Tokyo, Japan (6/94); South Central United States (2/250).