-3population.
Milk is more readily sampled and analyzed than are humans.
Using the conventional (although perhaps inaccurate) assumptions for the
infant of 30% 733
1
uptake in the thyroid, an effective retention half-time
of 7.6 days and a thyroid weight of 2 grams; an intake of 58,500 picocuries
of yi3t delivers a dose of 1.0 rad to the thyroid.
In the 1962 incident
the average intake for consumption of 1 liter of milk per day was 58,000
pe ysl from Pendleton's 39 milk farms scattered throughout Utah @ 3),
somewhat lower intake of 37,000 pe I
131
A
(the corresponding infant thyroid
dose is 0.63 rad) was obtained by the U. S. Public Health Service for the
*
Salt Lake City milk pool (49)
.
Unfortunately, ysl was not measured in
milk or people throughout Utah during Nevada testing prior to 1962.
This
seriously limits the accuracy of the remaining methods for estimation of
yt exposure.
C.
GAMMA ACTIVITY IN PASTURES
The arrival of fallout causes an increase in y-ray “background”.
ysl is but one component of this activity.
the I"
131
Fortunately, variations in
/total activity ratios can be reduced by correcting the y-reading
to a standard reference time such as l-day after detonation using the
relation ©) that the total activity varies approximately as (time)~+-*,
the 1131/rotal ratio will still depend on which element was fissioned
w?35 or P79) , whether yi31 selectively holds back or falls out relative
to the other fission products
(fractionation), and how much of the total
*The Salt Lake City milk pooled sample is made up of equal volumes
of milk from each of 14 dairies (of unequal size) which supply milk to
Salt Lake City (not the entire state).