160
THE SHORTUR-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
rems per week.
The External Dose Commitice
makes several exceptions, especially in the case
of the skin. There are many other variations
perhaps that are even more important. For
example,
we
should
have
values
for
the
various chemical forms of the radionuclides.
So thereis a lot of work yet to be done and we
will be happy when wefinish the present set of
valucs for about 150 new radionuclides that
we are including in the revised handbook.
The answer is “No,” in the forthcoming revision of the Handbook wedo not plan to make
anydistinction between the various organs with
the exception of the thyroid. MPC values are
based on two principal criteria: 1), 0.3 rems
per week to the organ, or 2) in the case of
hone seekers, an amount that will give a dose
corresponding to that received from 0.1 micro-
gram of radinm deposited in the bone.
Dr. Lanenam. I think it is pretty obvious
that part of the difficulty on this particular
subject centers around the fact that the ex-
perimental biologist and his experiments can
not keep up with Dr. Morgan and his pencil.
One more question.
Capt. Beynerr (BuShips Navy). We are
currently considering adapting our meters to
measure the external hazard to a considerable
extent by not a beta-gamma ratio, but a ratio
of shallow dosage to deep dosage which will
be based on a mean depthof the mytotic laver
of the skin. IT would like to ask Dr. Morgan
whether such @ meter would be properly used
for contamination hazard determination in
view of varying depths of the dangerous areas
in the internal organ?
Dr. Monrean. I think that some compromises
have to be reached in designing instruments to
measure the damage from beta emitters.
I think the answer to your question is yes, that
such an instrument would be very valuable.
Weare doing essentially the same thing in the
revision of our film badge, so that we will have
UPTAKE OF IODINE-131 IN HUMAN AND BOVINE THYROIDS
FOLLOWING DETONATION -OF NUCLEAR WEAPONS
one very thin window that will give us readings
By Mancarer R. Wuire and Harvin B, Jongs
that will correspond very closely to the dose
delivered at a depth of about 10 mg/em? tissue
equivalent. I think in any monitoring system
one should have a device that will indicate
the exposure from the beta radiation.
I don’t
helieve this has much dircet relationship to the
beta dose.
University of California. Radiation Laboratory, Berkeley, California
Beginning with the finding of measurable uptake of radioactive iodine(I) in thyroid tissue
in the periods following nuclear explosions
1 was not quite sure of the implication here
relative to the internal emitters. Along with
the external monitoring system, one has to
monitor the urine and try to determine what
the internal dose is. T am not sure that I got
{Van Middlesworth 1, 2], Donner Laboratory
has maintained a routine assay of 1content
of beef thyroids obtained from local slanghier
houses and more recently of human thyroids
nation meter as the device which measures
the probable hazard from internal dosage, and
fornia and Western cattle (U. C, R. L. Report
your question.
Capt. Bennerr. We consider the contamiwe wondered whether the standards that we are
setting for the external meter would be equally
applicable for a contamination meter.
Dr. Morgan. I want to look into the detailed standards before [ could answer that
question. Perhaps we could get together.
which could be obtained on autopsyin the San
Francisco area. The I"! concentrations of beef
thyroids were reported for 1955 Northern Cali-
3355,
March 1956).
This report confirmed
the Van Middlesworth observation and established the maximum uptake between March
and September 1955 as 6.4 millimicrocuries of
I™per gram of beef thyroid and a total inte-
grated maximum dose to the thyroid of cattle
of about 1 rep for the Spring and Summer of
1955. This activity apparently was the result
of the several detonations atthe Nevada testing
site. After the last test in mid-May 1955, the
maximum activityin beef thyroids declined fol-
lowing closely the natural half-life of !. Upon
this evidence and the additional evidence of a
promptrise in thyroid activity following nuclear
explosion, it may be concluded that beef thyroids are in rapid equilibrium with iodine fallout. Van Middlesworth has recently shown
that human thyroid EF"! concentration roughly
parallels bovine thyroid in radioiodine content,
and that the human thyroid concentration is
less than approximately 1/250th of the cattle
thyroid concentration. The times of maximum
iodine concentration in human or cattle thyroids evincided.
This report includes 151 human thyroids and
1,000 beef thyroids assayed for 1 content Oc-
tober 1955 to October 1956.
Two periods of
slight T™ content are recorded in December
1955 and January 1956 respectively, and two
periods of concentration of I approaching or
exceeding 1 millimicrocurie per gram of beef
thyroid which appeared in March and May
1956. Theactivity which appeared in March
died awayin detectable concentration in newly
obtainedbeef thyroids with ahalf-decline period
of 8 days. The radioactivity which began in
May 1956 maintained a value of 1 to 2.6 millimicrocuries per gram of beef thyroid during the
entire period, June to October 1956 in spite of
isotopic decay. Presumedly this reflected multiple additions to the atmospheric level of ['.
At all times of increased [™levels, some cattle
appeared to have low concentrations of I".
These cattle were usually described as feed-lotfed (see Table below). Range-fed cattle during
all periods of collection of samples had the
greatest concentration of I. Range-fed and
feed-lot-fed cattle differ by a factor of 50 to 100
in usual concentration. Somefeed-lot animals
appear to have appreciable concentrations of
thyroid 17", but the simplest assumption to explain this inconsistent uptake is the lack of re-
liability of information on feeding procedures
preceding marketing of beef. Additionally
there is the problem of difficult evaluation of
161