Internal dosimetry of nuclear medicine workers through the analysis of 131I in aerosols

I-131 is widely used in nuclear medicine for diagnostic and therapy of thyroid diseases. Depending of workplace safety conditions, routine handling of this radionuclide may result in a significant risk of exposure of the workers subject to chronic intake by inhalation of aerosols. A previous study including in vivo and in vitro measurements performed recently among nuclear medicine personnel in Brazil showed the occurrence of I-131 incorporation by workers involved in the handling of solutions used for radioiodine therapy. The present work describes the development, optimization and application of a methodology to collect and analyze aerosol samples aiming to assess internal doses based on the activity of I-131 present in a radiopharmacy laboratory. Portable samplers were positioned at one meter distant from the place where non-sealed liquid sources of I-131 are handled. Samples were collected over 1 h using high-efficiency filters containing activated carbon and analyzed by gamma spectrometry with a high-purity germanium detection system. Results have shown that, although a fume hood is available in the laboratory, I-131 in the form of vapor was detected in the workplace. The average activity concentration was found to be of 7.4 Bq/m(3). This value is about three orders of magnitude below the Derived Air Concentration (DAC) of 8.4 kBq/m(3). Assuming that the worker is exposed by inhalation of iodine vapor during 1 h, I-131 concentration detected corresponds to an intake of 3.6 Bq which results in a committed effective dose of 7.13 x 10(-5) mSv. These results show that the radiopharmacy laboratory evaluated is safe in terms of internal exposure of the workers. However it is recommended that the presence of I-131 should be periodically re-assessed since it may increase individual effective doses. It should also be pointed out that the results obtained so far reflect a survey carried out in a specific workplace. Thus, it is suggested to apply the methodology developed in this work to other nuclear medicine services where significant activities of I-131 are routinely handled as an effective means to optimize individual exposures and improve occupational radiation protection safety. (C) 2014 Elsevier Ltd. All rights reserved.