Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
bbseq long-term retention (t½ about 700 d) in airway walls of a small fraction
of the particles deposited in the bronchiolar region.
ALV retention (t½ about 200 d) of particles deposited in the alveoli. A
fraction (0.67) of the deposit is removed by particle transport to the ciliated
airways (bb′), while the remainder penetrates to the interstitium (INT).
INT very long-term retention (t½ about 60 y) of the particles deposited in
the alveoli that penetrate to the interstitium: the particles are removed slowly
to the lymph nodes.
Deposition
Refers to the initial processes determining how much of the material in the
inspired air remains behind in the respiratory tract after exhalation. Deposition
of material occurs during both inspiration and exhalation.
Endogenous excretion
Term used to specify the excretion of materials from body fluids to the
alimentary tract, applying to biliary excretion and passage of materials through
the alimentary tract wall.
Endosteum (or endosteal layer)
A 50 µm-thick layer covering the surfaces of the bone trabeculae in regions of
trabecular spongiosa and those of the cortical surfaces of the medullary
cavities within the shafts of all long bones. It is assumed to be the target tissue
for radiogenic bone cancer. This target region replaces that previously
introduced in ICRP Publications 26 and 30 (ICRP, 1977, 1979) – the bone
surfaces – which had been defined as a single-cell layer, 10 µm in thickness,
covering the surfaces of both the bone trabeculae and the Haversian canals of
cortical bone.
Exogenous excretion
Term used to specify the (faecal) excretion of material that passes through the
alimentary tract without absorption.
Extrathoracic (ET) Airways
Part of the respiratory tract, consisting of the anterior nose (the ET1 region)
and the posterior nasal passages, pharynx and larynx (the ET2 region). Note
that the oral part of the pharynx is no longer part of ET2 because it is included
in the HATM.
Exposure (in the context of inhalation)
The product of the air concentration of a radionuclide to which a person is
exposed (Bq m -3 ) and the time of exposure. More generally, when the air
concentration varies with time, the time integral of the air concentration of a
radionuclide to which a person is exposed, integrated over the time of
exposure.
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