Advantages of using thin sodium iodide detectors for thyroid monitoring of personnel working with 125I.

Measurements of neck count-rates for personnel who regularly iodinated proteins with 125I showed that, generally, count rates were higher after iodination than before. The major pathway for the intake of 125I during iodination was through skin that was exposed to the free-iodine atmosphere of the fume hood. Neck count-rates were measured in 34 other subjects who were working with 125I. The rates for 25 of them were significantly greater than for a control group of 36 subjects. Significant activities were also detected in seven of nine subjects who had never worked directly with 125I but who were located within areas where it was used extensively. To minimize thyroid burdens of 125I, it is essential that neck count-rates be measured routinely, in order to monitor the safety of procedures involving the use of 125I.