~ 20 «
Januery 1957 = dob
April 1957 - 6.75
February 1957~ 8.17
March 1957 - 7,38
May 1957 ~ 9.79
June 1957 - 10.91
July 1957 = 17.33
Interestingly enough, British data on milk Sr-90 from six loca-
tions for October, 1956, range from 4.6 to 10.3.(5). The same month
Mandan, North Dakota milk contained 8.9 ppo Sr.90/gm Ca and Perry, New
York milk 5.68,
This was in spite of the fact that there was more
strontium-90 in the corresponding United States soils than in the Mnited
Kingdom soils.
Undoubtedly milk Sr-90 reflects to a significant degree
not only uptake of Sr-90 into the animal food from soil but also Sr-90
that has adhered to the plants in the field and hence has by-passed the
soil.
Thus, the milk data to some extent reflect rate of fallout.
Analyses for Cs-137 have been done on milk and other material
including living human beings and human urine.
Anderson and Langham
(2) have out forth strong arguments for the concept that soil and plant
data on Cs-137 which is generally very poorly taken up by plants but
is readily taken up by animals might be used as an index of accumulated
fallout in soil and of rate of fallout onto plants.
Radioactivity
from Cs-137 in all anlyses are very small in terms of natural radio-
active potassium-40, in humans about 1/20th.
Having e half-retention
time in the human body of about 140 days it is not likely to build up
Significantly with a constant intake.
In other words, the Cs-137 con-
tent of humans reflects rather well the intake rate, while as will be
seen later, the Sr-90 content of humens reflects its build-up in the
soil and the Sr-90 to calcium ratio of the diet,