PLUTONIUM
101
3. HEALTH EFFECTS
(dissolution) of particles; then the dissolved molecules or ions diffuse across capillary walls and are taken
up by the blood. Immediately following dissolution, rapid absorption is observed.
For some elements,
rapid absorption does not occur because of binding to respiratory-tract components. In the absence of
specific data for specific compounds, the model uses the following default absorption rate values for those
specific compounds that are classified as Types F (fast), M (medium), S (slow), and V (instantaneous):
•
For Type F, there is rapid 100% absorption within 10 minutes of the
material deposited in the BB,
bb, and AI regions, and 50% of material deposited in ET
2
. Thus, for nose breathing, there is rapid
absorption of approximately 25% of the deposit in ET; for mouth breathing, the value is 50%.
•
For Type M, about 70% of the deposit in AI reaches the blood eventually.
There is rapid
absorption of about 10% of the deposit in BB and bb, and 5% of material deposited in ET
2
. Thus,
there is rapid absorption of approximately 2.5% of the deposit in ET for nose breathing, and
5% for mouth breathing.
•
For Type S, 0.1% is absorbed within 10 minutes and 99.9% is absorbed within 7,000 days, so
there is little absorption from ET, BB, or bb, and about 10% of the deposit in AI reaches the
blood eventually.
•
For Type V, complete absorption (100%) is considered to occur instantaneously.
ICRP (1996a) classifies insoluble plutonium oxides as Type S and recommends assigning all other
plutonium aerosols to Type M in the absence of specific information
supporting an alternative
classification.
ICRP (1994a) Plutonium Biokinetics Model
Description of the Model.
ICRP (1990, 1994a) developed a compartmental model of the kinetics of
ingested plutonium in humans that is applicable to infants, children, adolescents, and adults. The model
is a modification and expansion of a similar model for plutonium (DOE/EPA 1984), described by Leggett
(1985). The fraction of ingested plutonium that is absorbed (uptake to blood) is assumed to vary by
chemical form and age (Table 3-8). Absorbed plutonium enters the blood plasma where it distributes to
the
skeleton, liver, and other tissues (Figure 3-6). Excretion pathways included in the model are plasma
to urine and feces, including transfers to gastrointestinal tract from blood and liver. Transfer rate
coefficients between compartments are age-specific and, depending on
the specific coefficient, values can
change at ages 3 months, 1, 5, 10, and 15 years, and adult (>15 years) (Table 3-8).
PLUTONIUM
102
3. HEALTH EFFECTS
Table 3-8. Parameters of ICRP (1994a) Model
of Plutonium Biokinetics in Humans
a
Age
Parameter
b
3 months 1 year
5 years
10 years
15 years
Adult
Soft tissue (ST0) to
6.93x10
-1
6.93x10
-1
6.93x10
-1
6.93x10
-1
6.93x10
-1
6.930x10
-1
blood
Soft tissue (ST1) to
4.75x10
-4
4.75x10
-4
4.75x10
-4
4.75x10
-4
4.75x10
-4
4.75x10
-4
blood
Soft tissue (ST2) to
1.9x10
-5
1.9x10
-5
1.9x10
-5
1.9x10
-5
1.9x10
-5
1.9x10
-5
blood
Cortical/trabecular
7.6x10
-3
7.6x10
-3
7.6x10
-3
7.6x10
-3
7.6x10
-3
7.6x10
-3
bone marrow to blood
Other kidney tissue to 1.39x10
-3
1.39x10
-3
1.39x10
-3
1.39x10
-3
1.39x10
-3
1.39x10
-3
blood
Liver (2) to blood
2.11x10
-4
2.11x10
-4
2.11x10
-4
2.11x10
-4
2.11x10
-4
2.11x10
-4
Gonads to blood
1.9x10
-4
1.9x10
-4
1.9x10
-4
1.9x10
-4
1.9x10
-4
1.9x10
-4
Blood to soft tissue
2.773x10
-1
2.773x10
-1
2.773x10
-1
2.773x10
-1
2.773x10
-1
2.773x10
-1
(ST0)
Blood to soft tissue
8.06x10
-2
8.06x10
-2
8.06x10
-2
8.06x10
-2
8.06x10
-2
8.06x10
-2
(ST1)
Blood to soft tissue
1.29x10
-2
1.29x10
-2
1.29x10
-2
1.29x10
-2
1.29x10
-2
1.29x10
-2
(ST2)
Blood to trabecular
2.264x10
-1
2.264x10
-1
1.941x10
-1
1.941x10
-1
1.941x10
-1
1.941 x10
-1
surface
Blood
to cortical
2.264x10
-1
2.264x10
-1
1.941x10
-1
1.941x10
-1
1.941x10
-1
1.294x10
-1
surface
Trabecular surface to 8.22x10
-3
2.88x10
-3
1.81x10
-3
1.32x10
-3
9.59x10
-4
2.47x10
-4
volume
Cortical surface to
8.22x10
-3
2.88x10
-3
1.53x10
-3
9.04x10
-4
5.21x10
-4
4.11x10
-5
volume
Trabecular surface to 8.22x10
-3
2.88x10
-3
1.81x10
-3
1.32x10
-3
9.59x10
-4
4.93x10
-4
marrow
Trabecular volume to 8.22x10
-3
2.88x10
-3
1.81x10
-3
1.32x10
-3
9.59x10
-4
4.93x10
-4
marrow
Cortical surface to
8.22x10
-3
2.88x10
-3
1.53x10
-3
9.04x10
-4
5.21x10
-4
8.21x10
-5
marrow
Cortical volume to
8.22x10
-3
2.88x10
-3
1.53x10
-3
9.04x10
-4
5.21x10
-4
8.21x10
-5
marrow
Blood to other kidney 3.23x10
-3
3.23x10
-3
3.23x10
-3
3.23x10
-3
3.23x10
-3
3.23x10
-3
tissue
Blood to liver (1)
6.47x10
-2
6.47x10
-2
1.294x10
-1
1.294x10
-1
1.294x10
-1
1.941x10
-1
Liver (1) to liver (2)
1.77x10
-3
1.77x10
-3
1.77x10
-3
1.77x10
-3
1.77x10
-3
1.77x10
-
3
Blood to testes
1.3x10
-5
1.9x10
-5
2.2x10
-5
2.6x10
-5
2.1x10
-4
2.3x10
-4