Exposure to technologists from preparing and administering therapeutic 131I: how frequently should we bioassay?

It is common for nuclear medicine technologists to perform procedures involving the preparation and administration of therapeutic levels of (131)I-sodium iodide. This small study looked at the question of how much internal exposure a technologist receives, on average, while preparing and administering a therapeutic dose of (131)I.

The study estimated technologists' intake of airborne (131)I by measuring air concentrations in their breathing zone during therapeutic procedures using (131)I capsules. The measurement was made by determining the radioactivity collected on a charcoal filter contained within a personal air sampler. The radioactivity captured by the charcoal filter was assessed in a well counter.

Given these data, we were able to estimate the average (131)I intake of a technologist working in a general nuclear medicine department over a period of 1 y: about 19.2 kBq (0.52 μCi).

The NRC requirement is to monitor workers who could inhale or ingest more than 185 kBq (5 μCi) of (131)I in 1 y. The results of this small study suggest internal exposure rates that are well below the annual Nuclear Regulatory Commission trigger limits for individual bioassay.