The Health Physics and Radiological Health Handbook

Evaluation of Toxicological Hazards from Medical Radioiodine Administration

“…See explanation on the effective half-life under "Understanding Relative Radiation Exposure" for further explanation constant is used to calculate an estimate of radiation exposure coming from an individual [measured in milliroentgen (mR)] per unit time [measured in hours (h)] at a distance of 1 m. 1 The gamma constant for I-131 is 0.22 mR/h at 1 m per mCi. This is equal to a dose equivalence rate of approximately 0.002 mSv/ h at 1 m per mCi [5].…”

“…Although the toxicologist in our example does not know when the RI was administered, he or she can utilize the standard release rate and the radiation decay equation, A ¼ A 0 0:5 t=T 1=2 À Á , to estimate the current approximate dose equivalence rate at a 1-m distance from the patient. 5 The patient can be reassured to not worry about the external dose to members of the public who are at a distance of 1 m. The 5 mSv limit is a level of radiation dose for which a risk of disease is low [15].…”

“…Please see NUREG-1556, volume 9, revision 2 [9], for further guidance on these factors and the potential variance of patient-specific release rates. 5 Dose equivalence rate is different from exposure rate in that it takes into account the biological effect of different types of radiation. Exposure rate can be directly measured or determined from the radionuclide of interest and its activity.…”

“…Assuming the thyroid is a point source, the gamma constant for I-131 (approximately 0.002 mSv/h at 1 m per mCi) [5] yields a dose equivalence rate of 0.02 mSv/h from this point source (10 mCi×0.002 mSv/h/mCi at 1 m=0.02 mSv/h). The dose limit not to be exceeded to a member of the public from a patient released after therapy is 5 mSv [7].…”

Nevada Test Site Environmental Report 2009

“…Such low concentration values are considered to be below detection, meaning the concentration of the constituent in the sample is so low that it is undetected by the method and/or instrument. Shleien, 1992 (b) Total uranium may also be indicated by U-natural (U-nat) or U-mass (c) Natural uranium is a mixture dominated by 238 U; thus, the half-life is approximately 4.5 x 10 9 years …”