Environmental Health & Safety

Performing Iodinations

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

Prior to ordering I-125 ensure that your Principal Investigator is licensed to receive it. If he/she is not licensed for I-125, it is possible to obtain an amendment to the license by completing the form, "Amending a Radioactive Material License".

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 consists of thin lead foil, which is available through this Office. A scintillation detector should be used to survey for I-125 contamination. If you do not have a scintillation detector this Office can loan out a scintillation detector for a limited time.

Iodine, both stable and radioactive, is readily taken up by the thyroid 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 Thyroid Scan under Services).

The following safety consideration should be observed when storing, using and disposing of I-125:

  • 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 a 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 at fume hood.
  • Some Iodo-compounds can penetrate surgical rubber gloves. Therefore, double glove or as an alternative use polyethene gloves.
  • Containers of waste I-125 should 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:

  • Work in a fume hood with a flow rate of at least 150 feet per minute, but not greater then 300 feet per minute. The appropriate system for working with I-125 is a fume hood with an activated charcoal exhaust to remove the I-125 vapors. A fume hood for performing iodinations that includes a glove box with an activated charcoal exhaust is available through the Safety Office upon request at least 2 days in advance of using it.
  • 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 should wear a dosimeter to monitor exposure.
  • A sodium iodide detector should be used for monitoring for 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" labeled.
  • Shielding should be used around the waste container and the container with the labeled material.
  • The waste container should be provided with a cover for securing the contents.
  • Supplies in the fume hood should include additional gloves, tissues, and a tray with absorbent pad.

General Radiation Safety Practices

  • Designate and label areas for working with radioactive material
  • Label all containers with a radioactive material label and specify the isotope
  • No eating, drinking or smoking in the laboratory
  • No mouth pipetting of radioactive material
Conducting the Research
  • Use spill trays and absorbent covering
  • Use fume hoods for handling potentially volatile material
  • Use glove box for handling large quantities of volatile material
  • Wear laboratory coat, disposable gloves, and laboratory safety glasses
  • Use gloves appropriate for the chemicals to be handled
Post Research
  • Monitor and decontaminate surfaces as described in Chapter 14 of the Radiation Safety Manual
  • Dispose of radioactive waste in waste containers in accordance with Appendix G of the Radiation Safety Manual.
  • Insure the container is labeled with a "Radioactive Material" label and specify the radioisotope in the container.
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