THE EFFECTIVENESS OF ORAL-ADMINISTRATION OF POTASSIUM-IODIDE TO LACTATING GOATS IN REDUCING THE TRANSFER OF RADIOIODINE TO MILK

Ingestion of milk contaminated by radioiodine (most especially I-131) represents an important potential route of radiation exposure to human s in the event of a nuclear accident. Oral administration of stable io dine to dairy ruminants has previously been suggested as an effective counter-measure to reduce radioiodine levels in milk. However, previou s data on its effectiveness are contradictory, and little attention ha s been given to the most appropriate time to administer stable iodine relative to the time that an animal is first exposed to radioiodine. T he effectiveness of 1 g KI orally administered to lactating goats 12h before and 12h after contamination with pulse doses of radioiodine was investigated. Administration of KI prior to the ingestion of radioiod ine was shown to reduce the transfer to milk by 50% compared to a redu ction of approximately 40% when KI was administered 12h after radioiod ine. The administration of KI 12h prior to radioiodine contamination e ffectively reduced the transfer of radioiodine to the thyroid by appro ximately 90%. When administered 12h after radioiodine, the KI stopped subsequent uptake of radioiodine by the thyroid. The maximum level of iodine in milk, as a consequence of the administration of KI, was 20 m g I kg(-1). This was 40-fold higher than the maximum permissible level of iodine in milk of 0.5 mg l(-1) currently set in some countries. Fu rther consideration is required on stable iodine administration regime s for different scenarios and the consequent increase in the stable io dine content of the milk of different dairy animals. (C) 1997 ELsevier Science Limited.