Determination of iodine-125 intakes in a group of radiopharmaceutical production workers by means of thyroid radioactivity measurements

New ionising radiation regulations that broadly embrace the principles laid down by the International Commission on Radiological Protection in ICRP Publication 26 are to be introduced in the U.K. One of the implications of the new regulations is that quantification of intakes of radionuclides will receive more attention than previously. A programme of thyroid monitoring is described which has been carried out in order to assess the activity intakes of a group of workers engaged in the commercial production of 125I-labelled radioimmunoassay kits. The estimated annual activity intakes of four workers, each dispensing approximately 10 GBq of 125I per annum, were between 0.4% and 3% of the annual limit on intake. These intakes represented only about 3 x 10-6 of the total activity used annually by each worker. Other workers in the laboratory using lower activity materials were subject to lower intakes. (author)