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An inhalation pathway analysis similar to the one used for the Enewetak
Atoll dose assessment! °, based upon a mass loading concept, also indicates
that higher intake at Bikini by inhalation is possible.
Using a mass loading
of 100 g/m as in the Enewetak analysis !°, an average O-to 5-cm Bikini Pu
soil concentration of approximately 9 pCi/g, and a 20 m°/day breathing rate,
the annual intake via inhalation would-be 6.6 pCi compared with the estimate
of 0.2 pCi based on aerosol measurements.
Inhalation experiments 16
and dose models 7,16,17
indicate that approxi-
mately 0.1% of the activity inhaled will be excreted in the urine.
Assuming
an annual intake of 0.2 pCi for both Bikini and New York via inhalation,
only a total of 2 x 10° 4 pCi of Pu would be found in the urine during the
. course of a year.
s
The transfer coefficient across the gut into the blood is assumed to
be 3.x 10> for ingested Pul®. At Bikini this would mean that 15.4 x 10” 3
pCi would be transferred to the blood.
Of this amount approximate ly gy 16,17 or
1.2 x 1073 pCi would be transferred to the urine.
We find from this analysis
that the plutonium ingestion pathway contributes more than the inhalation
pathway to man at Bikini.
In New York the concentration to the total urine
level of Pu through ingestion (1.6 pCi x
3x10°° x 0.08 = 3.8 x 107° pCi) is
negligible compared to the inhalation route.
Therefore the total annual
estimated Pu in urine would be 2 x 107" pCi for New York residents and
2x10
4 °+12x10°21.4x
4
107? pCi for Bikini residents.
This computation
shows that plutonium levels in the urine could be at least 7 times higher at
Bikini than New York.
This ratio is very Similar to the ratio reported to usé.
As
These analyses indicate that thé differences observed in the Pu con-
centrations in urine of New York and Bikini populations can be accounted for
.
MD 5005525
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