Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
long-lived radionuclides with long term retention in the body. However, for the
example of 106 Ru, there is a decrease in committed effective dose as well as colon
dose, by about a factor two and five respectively, due to the major contribution to
effective dose from equivalent doses to alimentary tract regions for this radionuclide.
3.4.1 Intact skin
3.4 Intact Skin and Wounds
(195) Intact skin is an effective barrier against entry of most substances into the
body, and few radionuclides cross it to any significant extent. Exceptions of practical
importance are tritiated water in liquid or vapour form, organic carbon compounds
and iodine in vapour form or in solution.
(196) There is no general model for absorption of radionuclides through the skin
because of the wide range of possible exposure scenarios. Skin can become
contaminated by contact with, for example, aerosols, liquids, contaminated surfaces
or contaminated clothing. The physical and chemical form of the contaminant
(including pH) and the physiological condition of the skin are important factors in any
dose assessment.
(197) Both the radiation dose to the area of skin contaminated and the dose to the
whole body as a result of absorption should be considered. ICRP (ICRP, 1991, 2007)
recommends that skin doses should be calculated to sensitive cells, assumed to be at a
depth of 70 μm, or averaged over the layer of tissue 50 to 100 µm below the skin
surface and averaged over the most exposed 1 cm 2 of skin tissue. This applies to
activity either distributed over the skin surface or aggregated in particles. No
dosimetric models are recommended by ICRP for calculating doses from
radionuclides deposited on the skin and no dose coefficients are given.
3.4.2 Wounds
(198) Radionuclides may be transferred from the site of a contaminated wound to
blood and to other organs and tissues, and the NCRP has developed a model to
describe this transfer for materials in different physico-chemical forms (NCRP, 2007
and Figure 14). Because of the lack of adequate human data, parameter values for the
model were based on experimental animal data. When coupled with an elementspecific
systemic biokinetic model, the model can be used to calculate committed
doses to organs and tissues and committed effective doses following transfer of the
radionuclide to the blood and systemic circulation, as well as to predict urinary and
faecal excretion.
(199) This model was designed to be applicable for both soluble and insoluble
radioactive materials. Five compartments are used were designated to describe
physical or chemical states of the radionuclide within the wound site. These comprise:
Soluble (S) material; Colloidal and Intermediate State (CIS) material; Particles,
Aggregates and Bound State (PABS); Trapped Particles and Aggregates (TPA); and
Fragments. In some cases, the compartments contain the radionuclide in its original
physico-chemical form. In others, the originally deposited material changes state and
moves from one compartment to another with time. In most cases the model
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