Radionuclide Fact Sheet 
CARBON - 14
Symbol: 14C
States/Forms: Soluble, except gaseous
Physical Characteristics
- Radioactive Half Life (T½): 5730 years
- Decay Type: Beta- (ß-)
- Maximum Energy Emission: 0.156 MeV
- Maximum Range in Air: 21-25 cm
- Maximum Range in Water/Tissue: 0.028 cm
- Maximum Range in Plexiglas or Lucite: 0.025 cm
Hazard Category
- A Level (High Hazard): >1.0 Ci
- B Level (Moderate Hazard): >10 mCi to 1.0 Ci
- C Level (Low Hazard): 0.1 mCi to 10 mCi
Radiological Characteristics
- 17% of beta particle energy transmitted through dead layer of skin.
- Critical organ: Fat tissue.
- Routes of intake: Ingestion, inhalation, puncture, wound, skin contamination (absorption).
- Internal exposure and contamination: Primary radiological concerns with 14C.
- External exposure: External exposure from weak 14C beta particles is not a major radiological concern.
Dosimetry
- Film badges and dosimeter rings are not appropriate for monitoring 14C exposure.
Bioassay Requirements
- Urinalysis and breath measurements of CO2 may be required after spills or incidents of contamination.
External Radiation Hazards and Shielding
- There is minimal external hazard with 14C, i.e. the glass vial containing the 14C provides sufficient shielding from the beta particles. If the skin is uniformly contaminated with 14C, 1 microcurie/cm2 (µCi/cm2) will deliver a dose of 1100 miilirems per hour (mrems/hr) to the basal skin cells.
Hazards if Internally Deposited
ALI (Annual Limit of Intake)
- 2400 µCi - by ingestion
- 2000 µCi - by inhalation
DAC (Derived Air Concentration)
- 1 x 10-6 µCi/mL
Survey Instrumentation
- A Geiger-Muller pancake/frisker can be used to detect 14C, however the survey meter probe must be within a very close range (< 1 inch).
- Geiger-Muller detectors have a very low efficiency (~3%) for counting low energy 14C beta particles.
- Smear surveys, using liquid scintillation counters, are required to detect removable 14C contamination.
Problems and Precautions
- Lab coats and protective gloves should always be worn when working with 14C to keep skin free from contamination, and gloves should be changed often.
- All waste in a 14C work area is considered to be contaminated. Work areas should be kept free of unnecessary items.
- Wastes should be segregated to those with 3H and 14C only.
- It is assumed that ingested or inhaled 14C labeled compounds are instantaneously distributed uniformly throughout the organs and tissues of the body, where they are retained with a biological half-life of 40 days.