Use of a simple body-monitoring system in a pilot study on workers exposed to unsealed gamma-ray emitting material.

A portable body-monitoring system developed by the board uses two detectors, one for whole-body measurements and one for thyroid measurements. It can detect most commonly used gamma-ray emitting nuclides down to levels below those of interest for radiological protection purposes. The system has been used at 11 establishments including hospitals, universities, and research laboratories. Measurements have been made on 109 workers exposed to unsealed gamma-ray emitting material. Some activity other than that due to naturally occurring 40potassium was detected in a substantial proportion (30%) of those measured. The contaminating nuclides most often detected were 125iodine and 99mtechnetium. Some cases of contamination with 131iodine, 137caesium, 67gallium, and 85strontium were also detected. In most cases the level of activity detected was very low, but in three it was above the derived investigation level for routine monitoring of the nuclide concerned. The need for monitoring and possible monitoring programmes in which such a system would be useful are discussed.