Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
radionuclide in urine and faeces. These models are used in this document to derive
dose coefficients for inhalation or ingestion or radionuclides and to provide reference
rates of urinary and faecal excretion following intake of a radionuclide for use in
interpretation of bioassay data.
(372) The following categorization of the main types of information used to develop
biokinetic models and summary of uncertainties associated with each type of
information is taken from a paper by Leggett (2001). Additional investigations of the
sources and extent of uncertainties in biokinetic models for radionuclides can be
found in the following papers and reports: Apostoaei et al 1998, Leggett et al 1998,
2001, 2007, 2008, Harrison et al 2001 2002, Bolch et al 2001, 2003, Skrable et al
2002, Likhtarev et al 2003, Apostoaei and Miller 2004, Sánchez 2007, Pawel et al
2007, NCRP, 2010.
Uncertainties associated with the formulation (structure) of a biokinetic model
(373) The confidence that can be placed in predictions of a biokinetic model for an
element depends not only on uncertainties associated with parameter values of the
model but also on uncertainties associated with the model structure. Such
uncertainties may arise because the structure provides an oversimplified
representation of the known processes, because unknown processes have been omitted
from the model, or because part or all of the model formulation is based on
mathematical convenience rather than consideration of processes. Some combination
of these limitations in model structure is associated with each of the biokinetic models
used in this document. These limitations hamper the assignment of meaningful
uncertainty statements to the parameter values of a model because they cast doubt on
the interpretation of the parameter values. For purposes of assessing the uncertainties
associated with predictions of a biokinetic model for an element, it is often more
illuminating to examine the range of values generated by a limited number of
alternative modelling approaches than to produce large numbers of predictions based
on variation of parameter values within a fixed but uncertain model structure.
Types of information used to construct biokinetic models for elements
(374) Regardless of the model formulation or modelling approach, a biokinetic
model for an element usually is based on some combination of the following sources
of information:
H1: direct information on humans, i.e., quantitative measurements of the element
in human subjects;
H2: observations of the behaviour of chemically similar elements in human
subjects;
A1: observations of the behaviour of the element in non-human species;
A2: observations of the behaviour of one or more chemically similar elements in
non-human species.
Data types H2, A1, and A2 serve as surrogates for H1, which is the preferred type of
information on which to base a biokinetic model.
(375) The sources H1, H2, A1, and A2 are sometimes supplemented with various
other types of information or constraints, such as quantitative physiological
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