The Accumulation of Radioactive Iodine in the Thyroids of Grazing Animals Subsequent to Atomic Weapon Tests

Abstract

Radioactivity due to 1311 was found in thyroid glands collected from sheep and cattle depastured on areas in various parts of Australia subsequent to atomic weapon tests conducted during 1956 at Monte Bello and at Maralinga. Thyroids from cattle were found to contain up to 830 mfLc 1311 (37 mfLc 1311/g of tissue) and from sheep, up to 144 mfLc 1311 (70 mfLc 1311/g of tissue). The uneven degree of contamination of pastures was emphasized by the fact that some of the highest concentrations of 1311 were observed in glands collected from individuals of flocks and herds grazing on terrain 1500-2000 miles distant from the site of the explosions. As the tests proceeded, fluctuations in the 1311 content of the thyroid glands of grazing stock indicated that many areas received repeated dressings of radioactive debris.