Internal exposure to relatives of radioiodine therapy patients from I-131 inhalation at home

We studied the exposure to relatives of radioiodine therapy (RIT) patients from inhalation of 131I exhaled by the patients at home after their discharge from the hospital. Whole-body 131I activity was measured in 17 volunteers, all relatives of patients who had undergone RIT for benign thyroid disease, a new days after the patients' discharge. In 9 out of these, thyroidal 131I activity was measured, too. The measured activity was compared with the result of calculations based on a three-compartment model of iodine kinetics. A good correlation (r=0,88) was established between measured and predicted thyroidal activities under the assumption that 2 μg from a daily iodine intake of 60 μg are being exhaled. Effective dose from inhaled 131I did never exceed 100 μSv. Using the same model parameters effective doses of more than 8 mSv are predicted for out-patient RIT under worst-case assumptions. (orig.)