only after hundreds of rep were accumulated and tumors only after
1500 or more," The permissible level referred to is that recom
mended by the NCRP for industrial workers, The Committee noted
that although "some children have accumilated a measurable amount
of radicastive strontium in their bodies, the amount is quite
small--a thousandth of what is considered a permissible dose, The
Committee concluded, “then, that Strontium-90 is not a current
threat, but if there were any substantial increase in the rate of
contaminatison in the atmosphere, it sould become one,"
Committee on Meteorologizel Aspects of Atomis Radiation
Chairman - Harry Wexler ~ U, 5S. Weather Bureau
In this part of the report there is the fullest discus—
sicn of fallcut from nuzlear weapons, They distinguish between
kilcton bursts when the cloud does not penetrate to the strato-
sphere ard megaton bursts where the cloud does,
They estimate
that with surface bursts, i,e,, where the fireball touches the
ground 70-80% of the residual radisacstivity falls out nearby, i.e.,-
with small weapons a few miles, with larger cnes up to 300 miles
or more,
They emphasize the ease of predicting this "nearby" fall-
out pattern after the fazt and the problem of predicting its pre
cise pattern pricr to detsnation.,
They speak of intermediate fallout, i.e., material of
small particle size released below the stratosphere and some 80%
of which falls cut within three weeks in the same hemisphere in
which it originated and tending to uneven distribution associated
with rainfall and wind patterns alcng a broad band in the same
general latitude as that of its origin, Finally, they refer to
delayed fallout of material which has gained entry into the strato-—
sphere,
Jt is slow with an average storage time in the stratosphere
of 10 years, plus or minus five years,
AEC believes the latter
figure ~ five years - is the more likely, This delayed fallout
tends to distribute itself more ocr less uniformly over the surface
of the earth over the years.
\
NAS
They state that "at present, the amcunt cf Sr 90 in the
stratosphere from nuclear weapons tests is far tco small to approach
maximum permissible concentration even if it were all deposited now,"
They urged a continuing pregram to check on the amount of radioactivity in the stratosphere as necessary so that if there were to
be a greatly increased rate of thermonuclear weapons testing activi-
ties we would know at the earliest moment whan it was time to slow
down in terms of potential hazard from Sr 90 to man,
There is also a discussion of the radioactivity from fallout cf the intermediate and delayed varisty, They point out that it