Research involving the iodine labeling reactions using solutions of sodium iodide (NaI) or iodine reagents in millicurie (mCi) quantities are typically handled at high radioactive concentrations. This may pose a significant external radiation hazard and an internal and external contamination problem. This page provides safety considerations for performing iodinations to minimize these potential risks.

I-125 is a low energy gamma and x-ray emitter with a half-life of 59.6 days. The energy of the gamma and x-ray radiation emitted from I-125 is very low on the order of 20 to 40 keV. Therefore, the shielding for I-125 typically consists of thin lead foil. A scintillation detector should be used to survey for I-125 contamination. If the laboratory does not have a scintillation detector, the EH&S Department can rent out a scintillation detector for a monthly fee. 

Iodine, both stable and radioactive, is readily taken up by the thyroid gland if inhaled, ingested or absorbed through the skin. The thyroid may accumulate 30% or more of the total iodine ingested. A thyroid scan of the individual performing the iodination must be done prior to and after the procedure (See Bioassay Requirements under Radiation Safety Services).

The following safety considerations should be observed when storing, using and disposing of radioiodine: 

  • Volatile elemental I-125 can be formed by freezing or acidifying a solution containing I-125 ions. Normally I-125 in the form of NaI can be stored at room temperature.
  • Opening a container of highly concentrated I-125 can generate a radioactive aerosol of I-125. Therefore, work with volatile I-125 only in a fume hood.
  • Some iodine-compounds can penetrate surgical rubber gloves. Therefore, double glove or as an alternative use polyethene gloves.
  • Containers of waste I-125 should be closed when not disposing of waste into the container and after removing the container from the fume hood.

In addition, the following safety steps should be taken when handling volatile I-125 in amounts greater than 1 millicurie (mCi): 

  • Work in a fume hood with a flow rate of ~ 150 feet per minute (have EH&S test). The appropriate system for working with radioiodine is a fume hood with an activated charcoal exhaust to remove the radioiodine vapors. 
  • Individuals performing iodinations should wear a lab coat and double gloves, which are frequently monitored for contamination, and changed if found to be contaminated. An alternative to surgical gloves is polyethene gloves.
  • The individual must wear a dosimeter to monitor exposure.
  • A scintillation detector (such as NaI) should be used for monitoring contamination on gloves and the work area.
  • All potentially contaminated equipment and containers of radioactive material and waste should be posted with a "Caution Radioactive Material" label along with the radioisotope, date, and the activity (if waste). 
  • Lead shielding should be used around the waste container and the container with the radioiodine labeled material.
  • The waste container should be provided with a cover for securing the contents. Ensure that the cover is kept on. 
  • Supplies in the fume hood should include additional gloves, paper towels/tissues, and a tray with absorbent pad.
  • Dispose of all waste in accordance with Einstein's radioactive waste policies (see Section III.S. of the Radiation Safety Manual)  

Please contact the Radiation Safety Officer if your laboratory would like to work with iodine radioisotopes.