Environment, Health and Safety

Working with S-35

Sulfur-35 is a commonly used radionuclide with a half-life of 87.4 days, emitting only beta particles with a maximum energy of 0.167 MeV (Million Electron Volts) and an average energy of 0.049 MeV. The beta particles from S-35 travel a maximum of 24 cm. in air.


Contamination on the skin will not likely cause a significant dose to the dead layer of skin, however, it could lead to the internal absorption of S-35 if there are cuts in the skin. The Annual Limit on Uptake (ALI) for S-35 for ingestion set by the NRC and NYS Health Department State Sanitary Code, Chapter I, Part 16 is 1E+4 uCi (3.7E+5 kBq).

Another concern involving S-35 is the possibility of radioactive gas releases by self-decomposition during certain labeling experiments. This has been documented with [S-35]-Met/Cys used in labeling proteins regardless of the manufacturer or grade of label. Typical procedures have the potential of releasing significant amounts of radioactive gas that could contaminate all components of your continuous flow CO2 incubator. Use of this compound in a fume hood (approved and labeled for radioactive use) or in a specially designed containment system (i.e.Billups-Rothenberg Hot Box System) will reduce the possibility of lab contamination by keeping levels ALARA (As Low As Reasonably Achievable). Contact EH&S for further information.

S-35 Stock vial in a fume hood

S-35 Stock Vial in a Fume Hood


The following equipment and supplies must be available before handling S-35:

  • Liquid scintillation detector; scintillation cocktail and a geiger counter sensitive to beta particles calibrated by EH&S.
  • Disposable latex or plastic gloves
  • Full-length lab coat
  • EH&S approved S-35 Decay Storage box
  • Pipettes dedicated to the use of S-35
  • Commercial decontaminate, i.e. DuPont's "Count Off".
S-35 Shielding

Glass and plastic are the best shields for beta particles from S-35.

Safety Rules

If the following safety precautions are used when handling S-35, personnel radiation exposure will be as low as reasonably achievable.

  • Designate a specific area of the lab for S-35 handling.
  • Wear a full-length lab coat.
  • Wear two pairs of disposable gloves to protect your hands from becoming contaminated from spills.
  • Never pipette S-35 by mouth.
  • Only use pipettes which have been dedicated to your specific use of S-35.
  • Pipettes will easily become contaminated and therefore, should not be shared with others.
  • If you have reason to believe that your gloves are contaminated, immediately dispose of them in the radioactive waste container

Post-Use Procedures

  • Conduct a wipe test on all work benches, floor, equipment, centrifuges, and water baths.
  • Count the wipes in a Liquid Scintillation counter:
  • If contamination is found:
    • Use a commercial radiation contamination remover (i.e. Count Off) with paper towels to clean up the equipment:
    • Place the towels in the S-35 Decay Storage box.
    • If contamination cannot be removed, place a "radiation" label on the equipment indicating that it is S-35, maximum cpm found, and the date you measured the level.
    • Inform your fellow lab workers if any un-removable contamination is found.
    • Call EH&S if you have any questions about where to survey, or how to fill out the form.
    • Check the normal trash container to make sure no radioactive waste has been accidentally placed there.
    • Wash your hands thoroughly.
  • S-35 waste will be stored by EH&S until it has decayed sufficiently to be disposed.

Any questions about these procedures? Call EH&S at 829-3281.

S-35 Detection

A tiny drop of contamination from S-35 can be easily detected with a wipe test from a Liquid Scintillation Counter. A Gieger Counter has a low effeciency for S-35, but high activities can be detected.