125I

(Iodine-125)

Physical Characteristics

Half Life:

Physical 60.1 days

Biological 138 days (whole body) 138 days (thyroid)

Effective 41.8days (whole body) 41.8 days (thyroid)

Radiation Emitted: g and X-rays

Energy of Radiation (keV):

35 (7% emitted, 93% converted)

27-32 (138%m Te-X-rays)

Dose Rate a 1 meter from a 1 mCi Point Source: 0.275 mR/hr

Radiation Biology

Critical Organ: Thyroid

Toxicity: Medium/High

ALI: Ingestion Inhalation

All compounds 4X10+1 µCi 6X10+1 µCi

(Thyroid: 1X10+2 µCi) (Thyroid: 2X10+2 µCi)

Bioassay: (See Table 1)

Health Physics

DAC (µCi/ml): 3X10-8 (for all compounds)

Survey Technique: Low energy Gamma or X-ray scintillation-type survey meter.

Shielding Required: 0.8 mm of lead provides 95% attenuation.

Film Badge Required: Yes -- whole body.

Special Considerations: Volatilization is a most significant problem. Simply opening a vial of sodium iodide can cause significant airborne release. Breathing zone and exhaust effluent monitoring may be required. Solutions should not be made acidic or stored frozen. Double gloving strongly recommended. Notify RSO immediately if personnel contamination is suspected. Medical consultation may be needed. All work is normally to be done in an approved hood. Depending on activity used, supplemental "mini hoods," glove boxes, and/or in-line exhaust filters may be required.