An assessment of the risks to the health of grazing animals from the radioactive contamination of pastures.

As a result of the Chernobyl accident sheep and cattle in Wales, Cumbria and Scotland became contaminated with radionuclides of caesium and iodine. In the worst case, the maximum levels of contamination were of the order of 4000 Bq/kg of caesium-137 and 2000 Bq/kg of caesium-134 in muscle and 2,000,000 Bq/kg of iodine-131 in the thyroid gland. Calculations show that the radiation dose rates to the animals from these burdens of the radionuclides of caesium would have been approximately one thousandth of the dose rate needed to cause clinical signs of damage; in the case of iodine-131 approximately 10,000 times higher levels of the nuclide would have been required to cause clinically perceptible damage to the thyroid gland. In any forseeable nuclear accident severe problems of human health would arise before any detrimental effects on livestock could be detected.