Physical Data
- Gamma - 35.5 keV (7% abundance)
- X-ray - 27 keV (113% abundance)
Half-Life
- Physical: 60.14 days
- Biological: 120 - 138 days (unbound iodine)
- Effective: 42 days (unbound iodine)
Range
- Theoretically infinite in air (unshielded)
External Hazard
- Is an external exposure hazard. Unshielded exposure rate from a 1 mCi point source at a distance of 1 cm is 1,400 mrem/hour.
Internal Hazard
- Critical Organ: Thyroid Gland. Internal uptake results in whole body and thyroid exposure.
Skin & Eye Hazard
- Is an external exposure hazard. Unshielded exposure rate from a 1 mCi point source at a distance of 1 cm is 1,400 mrem/hour.
Safety Guidelines
- Whole body and ring dosimeters are required to be worn by individuals "routinely working with > 5 mCi quantities of I-125."
- Wear a lab coat and disposable gloves when working with I-125. Change gloves frequently.
- Avoid direct eye contact - wear safety glasses to avoid splashing I-125 into eyes.
- Store I-125 source vials and solutions behind lead shields.
- Internal radiation doses from radioiodine may result from inhalation, ingestion or absorption through the skin.
- Unbound sodium iodide (NaI) and certain labeled compounds can readily volatilize.
- All work with unbound compounds must be conducted within a properly working fume hood in an EH-approved mini-hood with a charcoal filter. Replace the filter as necessary. For more information contact Laurie Scholl at 353-5389.
- Use remote handling tools to manipulate mCi quantities of I-125.
- Neutralize spills of unbound NaI with sodium thiosulfate solution.
- A baseline thyroid bioassay is required prior to using 100 uCi or more of unbound (NaI) I-125.
- Post-iodination thyroid bioassays are required within 24-72 hours. Contact EHS at 335-8501 to schedule a thyroid count.
updated 01/2013