COMMON LOW ENERGY BETA EMITTERS

1.    H-3
2.    C-14
3.    S-35

H-3

Maximum energy: 18.6 KeV
Half-life: 12.3 years
Maximum range in air: 0.2 feet (~1/4 in.)
Penetration of skin: not through outermost layer
     An internal hazard
     No external hazard
Shielding: not required
Critical organ: whole body
Annual limits on intake (ALI):

80 mCi via inhalation, 80 mCi via ingestion
Appropriate detection instrument: Liquid scintillation counter (LSC) 60-70% efficient.
The regular use of wipe testing, using a LSC, is the only way to ensure that your work space is not contaminated. H-3 cannot be detected with a portable survey meter.
 

Special Considerations:

Tritiated nucleic acids and nucleic acid precursors are generally considered to be a more serious internal radiation hazard than other chemical forms.   Tritiated water vapor (HTO or 3H2O) is a common possible airborne hazard.  In addition to being used directly in this form, HTO may also be a by-product of experimental reactions or of the breakdown of other compounds.   Tritiated sodium borohydride (NaBH4[3H]) is an example of a compound whose use usually results in airborne release of HTO vapor.

 

 

H-3 migrates through containers (over time) and gloves. It can contaminate the inside of the freezer. Therefore, double containment is advised and dispose of H-3 when done using. Even though H-3 has a long half-life, it degrades chemically and may not be useful.

C-14

Maximum energy: 156 KeV
Half-life: 5730 years
Maximum range in air: 8.6 inches
Penetration of skin: less than a few mm
     An internal hazard
     Negligible external hazard
Shielding: not required
Critical organ:

whole body and body fat
Annual limits on intake (ALI): 200 mCi via inhalation, 2 mCi via ingestion
Appropriate detection instrument:

1)  Thin end window or pancake G-M probe (Low efficiency of detection 5-8%.  Most G-M detectors are not likely to detect the presence of C-14 in amounts less than about 100,000 dpm [0.05 uCi].) However, use the probe within a 1/2 inch of the surface, surveying slowly, without touching the surface.

2)  Liquid scintillation counter.   Recommended efficiency = 85-95%. (The regular use of wipe testing, using a LSC, is the only way to ensure that your work space is not contaminated.)

   
Special Precautions: C-14 may become airborne when used to study certain metabolic processes which result in the formation of 14CO2.  Any experimental procedures in which 14C may attach to dusts, mists, etc., may also result in airborne 14C.  Use fume hoods or other local ventilation to control any such hazards. Traps may be necessary to collect radioactive carbon dioxide gas if large gas or vapor releases are anticipated. This is to reduce the release to the environment.

S-35

Maximum energy: 167 KeV
Half-life: 87.4 days
Maximum range in air: 10 inches
Maximum range in tissue: .32 mm
     An internal hazard
     Negligible external hazard
Shielding: not required
Critical organ:

whole body and testis
Annual limits on intake (ALI): 20 mCi via inhalation, 8 mCi via ingestion
Appropriate detection instrument: 1)  Thin end window or pancake G-M probe. Low efficiency of detection, 5-8%.  Most G-M detectors are not likely to detect the presence of S-35 in amounts less than about 100,000 dpm [0.05 uCi]. However, use the probe within 1/2 inch of the surface, surveying slowly, without touching the surface.

2)  Liquid scintillation counter, 85-90% efficient.   The regular use of wipe testing, using a LSC, is the only way to ensure that your work space is not contaminated.

   

Special Precautions:

Gases containing 35S (i.e., 35SO2) may be formed during some chemical procedures and may pose an airborne hazard.  35S-labeled methionine/systeine compounds can volatilize.  Any experimental procedures in which 35S may attach to dusts, mists, etc. may also result in airborne 35S.  Use fume hoods or other local ventilation to control any such hazards. Activated charcoal can be used to trap contamination within equipment such as incubators. Stock solutions and thawed materials should be opened within a fume hood. Never use bleach as a disinfectant or to decontaminate a spill, as it can volatilize the sulfur-35.   (This is also true for I-125.)
   
  It is recommended to double glove.

University of the Sciences in Philadelphia • 600 South Forty-third Street • Philadelphia, PA 19104-4495 • phone: 215-596-8800 • email: safety@usp.edu