regions.
tracheobronchial
Particles assumed insoluble for lung and GI tract, soluble for other organs.
(e)
includes
URT is upper respiratory tract which
(c)
Numbers following E are exponents of 10.
the nasopharyngeal and
Yiy 7 0. I5y,(Oexp(~s t)exp(~7. 3[1-exp(-0.001899t) })
(d)
Particle size assumed to be 0.5 um activity mean aerodynamic diameter.
Modified
(a}
3, 60E+2
1.33E4
SDB
Task Group;
ICRP igs International Commission on Radiological Protection, Report of Committee II (1959}; Task Group is
Task Group on Lung Dynamics (Morrow, 1966) as modified in ICRP-19 (1972); SDB is Stuart, Dionne, and Bair
(1968, 1971); Modified is our modifications to the SDB model (Bloom and Martin, 1976).
5.43E+6
1.36E+6 | 6.79E+6
5-43E+6
5. 30E+3
8.82E+6
4, 74E+6
II
ICRP
Modified
a
~~
an
ICRP
IT
Task Group
SDB
Modified
SDB
Task Group
ICRP IL
Modified
Ingestion
Ingestion
Ingestion
Ingestion
(e)}
Inhalation
Inhalation
Inhalation
Inhalation
0.00
0.00
2.92E-3
1.07E-1
0.00
0.00
Ingestion
Ingestion
Ingestion
Ingestion
(e)
Inhalation
Inhalation
Inhalation
Inhalation
ICRP IL
Task Group
{b)
2.21E+2
B.46E+2 | 2.64E+3
6, 63E+6 | 6.21E+7
8.66E+5 | 2.67E+6 8.17E+5
8. 66E+5 | 2.67E+6 | 2.22E+5
1.51E+6
3.09E+5
1, 82E+2
1.82E+2
1.87E+2
2.62E+3
3.97E+3
7A45Et3
Rem
:
50=Year Cumulative Dose to Organs,
1.22E+3/0.00
1.22E+3/0.00
1,22E+3/0.00
0.00
0.00
1. 22E+3]5.52E+1
6.03E+3
3. 19E+3
7.59E+2/3,17E+6
5.48E+211. 28E+7
3.Q05E+8
4.82E+2/2. 24E+7
3.66E+8
1.94E+9
4. O2E+2/2.24E+7
1. 94E+0
3, 66E+8
1, 42E+2
1.26E+3
1, 26E+3
5.28E+3
1,.58E+2 | #02642
1.58E+2 © 4.02E+?
3.52E-1
5. 66E+2
3.15E+2
1,04E+3
2.74E+3
7. 96E+2
7. 96E+2
8. 48E+2
1.72E+2
1.72E+2
3.55E+3
3.90E+2
5.12E-1
6,57E-1
4.14E+3
9.26E+2
2.25E+3
7, 38E+2
1.52E-1
9,90E-3
9,91E-3
7.54E+L
1. 70E+L
1.13£+1
1,13E+1
1.54E-1
9.04E-3 4,02E-3 4.97E-1
9.04E-3| 2.08E-1 4.97E-1
3.50E-1
6. 70E-2
0.00
1.41E-3
0.00
0.00
0.00
4,41E-3
7.50E-1°?
7.50E-1;)0,00
7.50E-1]0.00
7.50E-1/7.375-4
4,69E-11 6. S8E+1
3.42E-111.35E+2
3, 00E-1)2.48E+2
3.Q0E-1]2,48E+2
50-Year Organ Burdens, uCi
1.65E-1
Total
Body
Borne
Kidney
Abdom.
Thoracic}
| rune
Tract
GI
|
=
urt’®
|
| Path
Mode?
Comparison of Calculations for lu Ci/Day Intake (a) Using Various Mcdels
Table ll.
u
o
>
oa
od
Stuart et al., 1971, applied their model to single inhalations and the variable half-time in the pulmonary lung did not present any difficulty.
However,
there is some doubt as to the interpretation of the variable half-time for the
chronic case. A strict interpretation would imply that a significant fraction
{15 percent) of material continuously deposited in the pulmonary lung is
eliminated with a half-time which exceeds 140 years after 10 years of chronic
inhalation, The lung burden could thus reach very high levels. There may
Indeed be a fraction which is retained with a long half-time, but we find it
difficult to believe this fraction could be so hiph (15 percent). We therefore examined the long-term behavior of the burden in this portion of the lung
resulting from a single inhalation. Equations (63) and (64) can be solved to
yield
(81}
where
¥p (0) is the initial amount deposited in the pulmonary Lung.
Neglecting radioactive decay (4,70), the initial fraction (15 percent) is
reduced to 0.4 percent after one year, 0.013 percent after five years, and
assymptotically approaches a constant value of about 0.01 percent. On the
basis of
these results,
we assumed
this
fraction
(0.01 percent)
is
retained
indefinitely, while the remaining 14.99 percent is removed with a three year
biological half-time.
Upon examining the calculated results in Tables 10 and 11, it is apparent that
inhalation is the critical pathway for plutonium to all organs except GIT.
The organ burdens and radiation doses from inhalation are generally 1,000 to
10,000 times greater than the corresponding burdens and doses from ingesting
the same amount of plutonium. This is due to the relatively large fraction
(0.2 to 25 percent) which reaches the blood directly from inhalation versus
the relatively small fraction (0.003 percent) from ingestion.
For ingestion,
the bone fs the critical organ for the ICRP-II and Task Group models, while
liver is critical for the SDB and Modified models, This difference is explained by the fraction transferred from blood to the organ which is 71 percent
to the liver and 25 percent to bone for the SDB and Modified models, while the
corresponding values for the ICRP-I1 model are 15 and 80 percent and those for
the Task Group model are 45 and 45 percent. Where the fractions are equal,
the bone has the Larger burden and dose because it has the larger biological
half-time.
For inhalation, the lung is the critical organ for all models except ICRP-I1.
The dose to lymph nodes is actually higher, but ICRP (1959) does not recognize
lymph nodes as critical organs.
For the ICRP-IE model, the bone is the critical organ because this model has the highest fraction of inhaled material
which reaches the blood immediately (25 percent) and the shortest biological
half-time in lung (365 days).
677