Evaluation of toxicological hazards from medical radioiodine administration.

Iodine-131 is a radioactive isotope that is routinely administered as sodium iodide-131 (NaI-131) by health-care providers to both diagnose and treat thyroid disease. Patients may receive between 1 μCi and 10 mCi for diagnostic procedures. Therapeutically, patients may be administered 1 to 300 mCi depending on whether they are being treated for hyperthyroidism (1 to 29 mCi) or thyroid cancer (30 to 300 mCi) [1, 2]. The mechanism by which radioiodine (RI) is taken up into the thyroid depends on a number of factors, including the functional status of the gland, the level of thyroid-stimulating hormone (TSH) in the blood, and the consumption of certain foods and medications [2, 3]. As RI undergoes radioactive decay by releasing energy in the form of gamma and beta radiation, safety precautions should be followed by those receiving RI to keep potential secondary exposures to the public well within regulatory limits [4]. Health-care professionals who assist in the administration of RI to a patient, such as the prescribing physician and nuclear medicine technologist, usually provide safety instructions to the patient prior to RI administration and again before discharge from the clinic or hospital. These instructions include the minimum distance at which the patient should stand from others, instructions on washing clothes, and instructions on toilet use [1]. Although instructions are usually given as a safety precaution to patients receiving RI therapy, hospitals are not legally required to provide instructions if the amount of radiologic activity administered (≤7 mCi), or the dose rate of a patient, falls below a certain threshold (e.g., ≤0.02 mSv/h at a distance of 1 m) [1]. In addition, many patients may find it difficult to recall the exact instructions provided to them following their RI administration. Finally, instructions given may not be as detailed as needed when it comes to handling of objects contaminated with the patient’s bodily fluids. Therefore, when a contamination incident occurs, patients may become concerned and seek the help of a health-care professional. If unable to reach their prescribing physician, they may contact a state or regional poison center for advice. Poison centers rely on health-care professionals with specialized expertise in clinical toxicology, such as medical toxicologists, to provide comprehensive advice in radiologic exposures. This necessitates medical toxicologists knowing what precautions to take when dealing with RI exposure and contamination issues. In addition, it may be advantageous for medical toxicologists to understand the inherent characteristics of the radiopharmaceutical so that they may provide the best guidance possible to the public on how to handle contamination scenarios or radiation exposure concerns. It is important to note that this paper pertains to that of NaI-131 and may not be suitable for application with other radiopharmaceuticals. In addition, although fundamental concepts are introduced, the expertise of subject-matter experts and outside resources may be necessary to call on in order to fully address certain situations.