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Concentration Guide for individuals in the general public, or 0.6 to
1.2%, for a suitable sample of the public.
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Thus, the levels of plutonium in the top layer of soil at Rocky
Flats and at Palomares have not led to any situations of concern with
respect to a possible airborne pathway to man.
As discussed in the
following section, the situation is expected to be even more favorable
with respect to possible airborne plutonium at Bikini.
Particle Size in Soil.
Determination of the size of individual particles
of plutonium oxide or plutonium oxide agglomerated with soil is almost
impossible after the particle has reached the earth's surface and become
mixed with other particles.
It is the opinion of Dr. John Harley, HASL,
and Dr. Wright Langham, LASL, that particle size studies of plutoniumbearing soil at Bikini or elsewhere would be unprofitable.
Most particle
size determinations for studies on plutonium are made on fallout
samples collected by cascade impactor or selective filters.
A number
of particle size determinations were made on samples collected following
Project 57 (during Operation PLUMBOB, NTS during 1957) and Operation
ROLLER COASTER (Tonopah Test Range, 1963).
A report of particle size determinations on air samples collected
by cascade impactors following the Double Tracks event of ROLLER COASTER,
indicated particle sizes ranging from 2.5 microns diameter to more than
35 microns diameter.
To gain entry into lungs, the plutonium oxide
must be in very fine "respirable" particles (i.e., less than 10 mic