Lungs
Based on these and other considerations, the concentration of ??9Pu in the
lungs of the cows from the outer compound of Area 13 can be estimated as
follows:
where, 3 x 107? is the fraction transferred from the gastrointestinal
tract to blood (Figure 2),
0.12 {6 the fraction transferred from the blood to the liver
(Figure 2),
4.8 kg is the estimated weight of the Liver,
and
Ciame = £78 m?/day) (107* g/m?)(215 pci/g) (0.18) [1-243
2.1 keg
i
= 55 pCi/kg (vs. 48 pCi/kg, Table 4),
where, 76 m? /day is the estimated respiration rate for a 275-kgz
cow (Equation 21),
107 g(soil)/m3(air) is the estimated mass loading factor
(Equation 21),
215 pCi/g is the average concentration of *39Pu in the soil
of Area 13*,
0.18 is the assumed fraction of inhaled plutonium deposited
in the lungs and cleared with a 500-day half-life,
2.1 kg is the estimated weight of the lungs,
and
X = 1n(2)/500 days,
Liver and Muscle
The plutonium ingestion rate for a 275-kg cow can be estimated as follows:
r, = 6158g(veg)/day** x O.1 x 70 pCi/g(soil)
+ 250g(soil)/day x 70 pCi/g(soil)
The concentration in liver for cows in the inner compound can now be estimated
as follows:
“435%
(60,606 g/day)(3 x 10 >) (0.12) (= 433
4.8 kg
Similar calculations were made for the other cases given in Table 4,
The
observed values from Table 4 and the estimated values are compared below in
pCi/kg wet weight.
Outer Compound
Observed
Estimated
Inner Compound
Observed
Estimated
Lungs
48.0
55,0
NR
61.0
Liver
13.7
19.6
38.9
60.7
Muscle
0.12
0.4
0.17
1.12
These comparisons (above) suggest that the model for beef cattle may be somewhat conservative, but the order-of—magnitude agreement between observed and
estimated values appears ta be good, better than might be expected as a matter
of fact. However, partial data for four cows, two areas, and two grazing
times is hardly an adequate basis for model validation. The best we can
conclude from these comparisons is that they provide no basis for rejecting
the model. The discrepancy between the experimental values and values predicted by the model are less than an order of magnitude, and we have iitcle
reason to expect better than an order of magnitude accuracy.
The Milk Cow
= 60,606 p Ci/day.
Cry
A = 1n(2)/30,000 days (Figure 2).
x
19.6 pCi/kg (vs. 13.7 pci/kg, Table 4),
The model milk cow is assumed to weigh 650 kg and to produce milk at a rate of
25 kg/day. Such an animal would require a digestible energy intake of 64,750
kcal/day, 1.e-., 18,500 kcal/day for maintenance plus 25 kg/day x 1,850 kcal/kg
for milk production (Siegmund, 1967). To meet this high-energy requirement
and, at the same time, provide a conservatively high estimate of plutonium
transport to man via milk, we shall assume that the model milk cow consumes
10 kg/day of desert vegetation and 15 kg/day of alfalfa hay grown in the same
contaminated area. The remainder of the diet consists of commercial concentrates containing no plutonium. For the model milk cow, the plutonium ingestion rate is estimated as follows:
I=, (250¢(soil)/day + 0.1 x 10,000g(veg) /day
*The average soil concentration in the outer compound is 70 pCi/g, but
some of the resuspended material in the air of the outer compound ts
assumed to come from the soil of the inner compound.
**Based on Equation (20) for a 275-kg cow.
652
+ 0.017 x 15,000g(alfalfa)/day)
= 1505 C, (pCi/day),
653