Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
important to distinguish between those reference parameter values that might be
changed in the calculation of effective dose under particular circumstances of
exposure and those values that cannot be changed under the definition of effective
dose. As effective dose applies to a reference person, individual-specific parameter
values should not be changed whereas material-specific parameter values may be
changed. Examples of material-specific parameters include lung-to-blood absorption
parameters, alimentary tract transfer factors and aerosol parameters such as the
activity median aerodynamic diameter (AMAD) of the inhaled aerosol.
(304) In the majority of cases, assessed doses are low in comparison to dose limits,
and for such cases it is likely that dose assessments will make use of the
recommended default values for material-specific parameters, the tabulated dose
coefficients and the ‘dose per unit content’ tables that accompany this report series.
Where assessed doses are likely to be greater, or where more than one monitoring
method has been used and a number of monitoring measurements have been made,
material-specific parameter values other than the recommended defaults may be used.
(305) In carrying out retrospective assessments of doses from monitoring data, the
assessor may need to make assumptions about factors such as the pattern of intake
and properties of the material because of lack of specific information on these factors.
A European project in the EC 5th Framework Programme was established to give
general guidelines for the estimation of committed dose from incorporation
monitoring data (Project IDEAS). The project developed a structured approach to the
interpretation of individual monitoring data (Doerfel et al, 2006, 2007), building on
the proposals made by the ICRP Working Party on Dose Assessment (Fry et al,
2003). This guidance has been developed further by the European Radiation
Dosimetry Group (EURADOS) (Lopez et al, 2011b; Marsh et al, 2008).
(306) In addition to this guidance, the International Organization for Standardization
(ISO) has published an International Standard, ISO 27048:2011 (ISO, 2011) that
specifies the minimum requirements for internal dose assessment for the monitoring
of workers. The IDEAS guidelines and ISO 27048 both adopt the principle that the
effort needed for dose assessment should broadly correspond to the anticipated level
of exposure.
(307) In unusual cases where doses to specified individuals may substantially
exceed dose limits, the committed effective dose can only provide a first approximate
measure of the overall detriment. If radiation dose and risk need to be assessed in a
more accurate way, further specific estimates of organ or tissue doses are necessary,
especially if organ-specific risks for the specified individuals are needed. In such
cases, absorbed dose to organs should be calculated and used with the most
appropriate biological effectiveness and risk factor data (ICRP, 2007). This
retrospective individual dose assessment should only be performed by professionals
with recognised expertise, skills and practical experience. It is beyond the scope of
this publication to give advice on how to perform individualized retrospective dose
and risk assessments.
(308) This Chapter discusses the information that should be collected on the
exposure, summarises approaches to data handling for single or multiple
measurements, and discusses uncertainties associated with internal dose assessments,
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