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Page Title:
Table VIII. Relative Importance of Various Sources of Uncertainty for Dose Assessment |
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|  DOE-STD-1121-98
Table VIII. Relative Importance of Various Sources of Uncertainty for Dose Assessment
In
In vitro
Workplace
Source of Uncertainty
vivo
Monitoring
The degree to which the contaminated air measurement
represents the air actually breathed, including the effects of
-
-
high
respiratory protection
The difference between actual and modeled breathing rate
-
-
high
Nose or mouth breathing
-
-
high
Degree of knowledge of particle size distribution
med
high
high
Aerosol transportability from lung into the transfer
compartment, GI tract, and lymphatic system
med
high
high
Assumed aerosol deposition in the lung
-
high
high
Clearance rate from the lung
high
high
high
Cleared aerosol absorption from the GI tract and lymphatic
high
high
high
system
Time course of intake(s)
high
high
high
Assumptions of present locations of radionuclides within the
region near the detector (e.g., lymphatic system or lung)
high
-
-
Systematic uncertainty in calibration
high
low
med
Random uncertainty in measurement
high
low
med
Systematic uncertainty in the choice of an appropriate blank
med
low
low
Biokinetic model assumptions
high
high
high
Future time course of retention and excretion
high
high
high
Mass of target tissues or organs
high
high
high
Assumptions of present locations of radionuclides within the
low
high
high
body (e.g., liver or bone)
Fraction of radionuclide excreted by route being sampled
-
high
-
Assessing committed effective dose equivalent (HE,50) from bioassay measurements is generally
mores accurate than assessing HE,50 from measurements of concentration of radioactive material in air and
multiplying by stay time and breathing rate. There are numerous reasons why the latter procedure
requires more leaps of inference than the former. However, for the case of plutonium and other actinides,
air samples and stay times may be much more sensitive, that is, they may have much lower detection
limits when expressed in terms of HE,50. Furthermore, dose assessment based on air samples may also be
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