PLUTONIUM
107
3. HEALTH EFFECTS
period is 50 years for acute intake as an adult (age 25 years) and from intake to age 70 years for acute
intake at ages ≤15 years.
Target Tissues.
The model is designed to calculate radiation dose coefficients (Sv/Bq) corresponding
to specific inhalation or ingestion exposures to plutonium isotopes. Dose coefficients have been
estimated for all major organs, including the bone surfaces,
bone marrow, and liver, and other tissues
(ICRP 1994a, 1996a).
The model is based on both human and animal data. However, it is intended
for applications to human dosimetry. Applications to other species would
require consideration of
species-specific adjustments in model parameters.
The ICRP model is designed to simulate kinetics of ingested plutonium,
injected plutonium, and if combined with a respiratory tract model (e.g., ICRP Human Respiratory Tract
Model for Radiological Protection, ICRP 1994b), inhalation exposures to plutonium. The model can be
applied to any other route of exposure for which the transfer rate to blood is available.
Luciani and Polig (2000) Plutonium Biokinetics Model
Description of the Model.
Luciani and Polig (2000) developed a modification of the ICRP (1994a)
model that provided a more physiological parameterization of urinary excretion pathways and
modifications to the bone model. Modifications to the structure of the model were: (1) deletion of the
transfer pathway from soft tissue ST1 to urinary bladder; (2) deletion of transfer pathways from cortical
and trabecular bone surfaces to
bone volume; and (3) addition of a transfer pathway from blood to bone
volume (Figure 3-8). Specific changes made to rate coefficients are presented in Table 3-9.
Validation of the Model.
The Luciani and Polig (2000) model was calibrated with data on long-term
kinetics of plutonium in blood, urine, and feces following intravenous injection of Pu(IV) citrate into
subjects suffering from chronic disorders (Langham et al. 1950, 1980; Moss and Gautier 1983; Rundo et
al. 1976), and urinary excretion of plutonium in workers exposed to plutonium at the Mayak plant
(Khokhryakov et al. 1994). Predicted urinary excretion of plutonium was compared to observations made
on nine workers (USTUR 1993; Voelz et al. 1979, 1985). The Luciani and Polig (2000) model showed
improved agreement between predictions and observations compared to the ICRP (1994a) model (Luciani
PLUTONIUM
109
3. HEALTH EFFECTS
Table 3-9. Comparison of Parameters of ICRP (1994a) Model and Luciani and
Polig (2000) Model of Plutonium Biokinetics in Humans
a
Adult parameter values
Parameter
b
ICRP (1994a)
Luciani and Polig (2000)
Soft tissue (ST0) to blood
6.93x10
-1
1.39x10
-1 d
Soft tissue (ST1) to blood
4.75x10
-4
9.50x10
-4 d
Soft tissue (ST2) to blood
1.9x10
-5
1.9x10
-5
Cortical/trabecular bone marrow to blood
7.6x10
-3
7.6x10
-3
Other kidney tissue to blood
1.39x10
-3
1.39x10
-3
Liver (2) to blood
2.11x10
-4
4.00x10
-4 d
Gonads to blood
1.9x10
-4
1.9x10
-4
Blood to soft tissue (ST0)
2.773x10
-1
2.773x10
-1
Blood to soft tissue (ST1)
8.06x10
-2
8.06x10
-2
Blood to soft tissue (ST2)
1.29x10
-2
1.29x10
-2
Blood to trabecular surface
1.941x10
-1
2.26x10
-1 d
Blood to cortical surface
1.294x10
-1
9.52x10
-2 d
Trabecular surface
to volume
2.47x10
-4
Deleted
Cortical surface to volume
4.11x10
-5
Deleted
Trabecular surface
to marrow
4.93x10
-4
1.59x10
-3 d
Trabecular volume to marrow
4.93x10
-4
1.59x10
-4 d
Cortical surface to marrow
8.21x10
-5
1.56x10
-4 d
Cortical volume to marrow
8.21x10
-5
8.22x10
-5 d
Blood to other kidney tissue
3.23x10
-3
3.23x10
-3
Blood to liver (1)
1.941x10
-1
1.20x10
-1 d
Liver (1) to liver (2)
1.77x10
-3
1.00x10
-2 d
Blood to testes
2.3x10
-4
2.3x10
-4
Blood to ovaries
7.1x10
-5
7.1x10
-5
Liver (1) to small intestine
1.33x10
-4
4.00x10
-4 d
Blood to upper large
intestine contents
1.29x10
-2
8.0x10
-3 d
Blood to kidney (urinary path)
6.47x10
-3
9.93x10
-3 d
Blood to urinary bladder contents
1.29x10
-2
9.46x10
-3 d
Soft tissue (ST1) to urinary bladder contents
4.75x10
-4
Deleted
Kidneys (urinary path) to bladder
1.386x10
-2
1.02x10
-2 d
Gastrointestinal tract to blood
c
5.0x10
-4
5.0x10
-4
a
See Figure 3-8 for schematic representation of model.
b
Units are in days
-1
, except for gastrointestinal tract to blood, which is unitless.
c
Values shown for the absorption fraction are for general public exposures (e.g., diet).
Recommended values for
occupational exposures are as follows: oxides (excluding poly-disperse oxides), 1x10
-5
; nitrates, 1x10
-4
; and other
compounds or unknown mixtures, 1x10
-4
.
d
Modified in Luciani and Polig (2000).