Evaluation of a scheme for the pre-distribution of stable iodine (potassium iodate) to the civilian population residing within the immediate countermeasures zone of a nuclear submarine construction facility

Background The Barrow-in-Furness stable iodine (potassium iodate) tablet pre-distribution scheme was the first of its kind to be introduced to protect the population living around a fixed site nuclear facility in the United Kingdom. Predistribution schemes have attracted critical comment principally because the certainty of availability of potassium iodate tablets was unknown. This study aimed to establish the reliability of such a scheme. Method A structured interviewer-administered survey of a random sample of households served by the pre-distribution scheme was carried out using a standardized questionnaire. Results The ability of this scheme to provide stable iodine protection declined from 100 per cent to 60 per cent coverage over a period of two years for the designed worst-case demand (the ability to supply stable iodine tablets to all household residents normally living within the pre-distribution scheme zone). Conclusions Pre-distribution has value in areas where evacuation to a centre where stable iodine tablets are available or post-accident distribution to sheltering households is difficult. The value of such a scheme must be calculated against a predictable decline in its effectiveness. In implementing such a scheme it should be noted that this decline in coverage can be reduced by calculating the frequency with which tablet packs are redistributed to take account of this factor.