Personnel internal radiation exposure to iodine-125 in a radioiodination laboratory: Exposure levels and trends

Background: Monitoring internal exposure of individuals handling significant amounts of iodine-125 (I-125) for iodination is of great importance. These individuals are potentially exposed to external contamination, and internal contamination through inhalation, ingestion and intact skin absorption, to I-125. Considering radiological toxicity of this radionuclide its monitoring in the workplace and workers is necessary for radiation protection purposes. Materials and Methods: Direct measurement of I-125 in thyroid of individuals, known as a common and reliable method, was applied in the framework of monitoring program. Intakes of I-125 by individuals and the associated effective doses were evaluated using thyroid monitoring results and recommended metabolic models. Results: The monitoring results of the laboratory personnel for a period of 3 years are given and compared . According to the results , the intakes of I-125 by individuals in the early phase of laboratory operations were higher due to insufficient facilities and experience. Improvements in the radiation protection facilities of the laboratory and personnel including provision of personal respiratory protection devices resulted in significant reduction of I-125 intakes . Conclusion: According to 3 years results from the implementation of internal exposure monitoring program for personnel producing I-125 labeled compounds, the exposure levels of the personnel have contineously decreased due to improvements in working conditions and increasing of personnel experiences.