Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
excretion, strictly elimination, of the material passing unabsorbed through the
alimentary tract after ingestion or clearance to the throat from the respiratory system
after inhalation.
(90) The reference models outlined in this Chapter are assigned reference
parameter values and used to calculate body or organ content and daily urinary or
faecal excretion at specified times after acute or chronic intake. They are used to
calculate reference bioassay functions and, together with dosimetric data, reference
dose coefficients.
3.2 Revised Human Respiratory Tract Model (HRTM)
(91) The Human Respiratory Tract Model (HRTM) described in Publication 66
(ICRP, 1994a) was applied to calculate inhalation dose coefficients for workers and
members of the public in Publications 68, 71 and 72 (ICRP, 1994b, 1995c, 1996), and
bioassay functions in Publication 78 (ICRP, 1997b). A revised version of the HRTM
is used in this series of reports and is described below.
(92) As in the original version of the HRTM, the respiratory tract is treated as two
tissues: the extrathoracic regions (ET) and the thoracic regions (TH). The sub-division
of these tissues into regions was based mainly on differences in sensitivity to
radiation. The thoracic regions are bronchial, (BB: trachea, generation 0, and bronchi,
airway generations 1 – 8), bronchiolar (bb: airway generations 9 – 15), alveolarinterstitial
(AI: the gas exchange region, airway generations 16 and beyond); and the
thoracic lymph nodes, LNTH. The extrathoracic regions are the anterior nasal passage,
ET1; the posterior nasal passages, pharynx and larynx, ET2; and the extrathoracic
lymph nodes LNET (Figure 3). For consistency with the HATM, the oral passage is not
now included in region ET2 as it was in Publication 66. This does not affect results
obtained with the model, because deposition in ET from air entering the mouth was
taken to occur only in the larynx.
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