Occupational Intakes of Radionuclides Part 1 - ICRP

2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
Lung retention
1.0
0.8
0.6
0.4
0.2
0.0
DRAFT REPORT FOR CONSULTATION
10 100 1,000 10,000 100,000
Time (d)
62
Jammet (1978)
Bohning (1982)
Bailey (1985)
Philipson (1994)
Davis (2007)
RFP (2007)
Original HRTM
Kuempel (2001)
Revised HRTM
Figure 8. Measured lung retention data (Philipson et al, 1996; Davis et al, 2007; (ORAUT,
2007) and studies reported in Publication 66 Annex E, (ICRP, 1994a) are shown together
with the model predictions by assuming initial deposition in the alveolar region only.
Predictions of both the original HRTM and the Kuempel et al (2001) model with default
parameter values are shown. The ‘Revised HRTM’ curve was obtained with optimised AI
particle transport parameters AIseq = 0.37 and m = 0.0027 d –1 (from Gregoratto et al, 2010).
3.2.3 Clearance: Absorption to blood
(128) Absorption to blood (body fluids) depends on the physical and chemical form
of the deposited material. In both the original and revised HRTM it is assumed (by
default) to occur at the same rate in all regions (including the lymph nodes) except
ET1 for which it is assumed that no absorption takes place. It is recognised that
absorption is likely to be faster in the AI region where the air-blood barrier is thinner
than in the conducting airways (ET, BB and bb regions), but there is insufficient
information available to provide a general systematic basis for taking this into
account, such as a scaling factor for different rates in different regions.
(129) In the HRTM absorption is treated as a two-stage process: dissociation of the
particles into material that can be absorbed into body fluids (dissolution); and
absorption into body fluids of soluble material and of material dissociated from
particles (uptake). The clearance rates associated with both stages can be timedependent.
(130) Dissolution: both the original and revised HRTM use the same simple
compartment model to represent time-dependent dissolution. It is assumed that a
fraction (fr) dissolves relatively rapidly, at a rate sr, and the remaining fraction (1 – fr)
dissolves more slowly, at a rate ss (Figure 9(a)).