The University of Iowa

Radionuclide Safety Guideline for H-3

Physical Data

  • Radiation -  Beta (100% abundance)
  • Energy  - Max: 18.6 keV; Average: 5.7 keV


  • Physical: 12.3 years
  • Biological: 10-12 days
  • Effective: 10- 12 days


  • 6.0 mm in air unshielded (0.5 cm; 0.25 inches)

External Hazard

  • Not an external hazard

Internal Hazard

  • Critical Organ: Body water or tissue

Skin & Eye Hazard

  • 0% of H-3 beta particle energy is transmitted through the dead layer of skin.

Safety Guidelines

  • Shielding is not required. Dosimeters cannot detect H-3 beta radiation due to its low energy.
  • H-3 cannot be detected with a survey instrument or with a dosimeter.
  • Wear a lab coat and disposable gloves when working with H-3. Change gloves frequently.
  • Avoid direct eye contact - work behind a Plexiglas shield or wear safety glasses.
  • Skin contamination, inhalation, ingestion or absorption through the skin is assumed to be completely and instantaneously absorbed and rapidly mixed with total body water.
  • Volatile H-3 compounds should be used in an operating fume hood. Contact Laurie Scholl at 353-5389 for further information.
  • Tritiated water can readily penetrate gloves and skin in a short period of time.
  • DNA precursors are more toxic than tritiated water because the activity is concentrated in the cell nuclei.
  • Bioassays are required following the use of 100 mCi or more of tritiated water or 25 mCi or more of organically bound H-3. 

updated 1/2013