Plutonium Biokinetics in Human Body A. Luciani - Kit-Bibliothek - FZK

From Table 3.1.2 it turns out that the ratio of the geometric means are very close to 1.
The geometric mean of the Plutonium urinary excretion observed in Langham’s subjects in
the considered time period is on average 7% smaller than the same value for Talbot’s
subjects; for the fecal excretion a discrepancy of 12% was observed. Such percentages point
out that, on average, the geometric means for the two data sets are not significantly different.
The mean maximum and minimum values of the urinary excretion of Plutonium for
Langham’s subjects on average are +17% and –26 % of the observed values for Talbot’s
subjects, respectively. Only the fecal excretion of Plutonium has a maximum value that on the
average is 82% greater, but a more careful analysis of the data has shown that this is due
mainly to just one subject. By eliminating the excretion data of this subject, the deviation is
already reduced to +50%. Large deviations of the maximum and minimum values for the two
data sets can be easily found because these values relate to a single subject, and not to all the
subjects of the group as the geometric mean previously calculated.
According to the previous considerations too, Langham’s and Talbot’s data sets can be
considered as only one group of data, particularly when they are used to calculate a mean to
be adopted as a reference value of Plutonium excretion. Therefore the values for the urinary
excretion of Plutonium from all the subjects of the two groups were averaged by calculating
the geometric mean for each time point. Analogously the geometric means of the data for
Plutonium fecal excretion and blood content were calculated. From now on the term
“experimental data” will refer to such geometric mean values calculated on the whole group
of subjects from Langham’s and Talbot’s studies.
The effect of a subject’s gender on the excretion of Plutonium should be also
considered. Studies [100, 101] have recently pointed out slight but constant differences
between the urinary excretion of Plutonium between male and female subjects. Unfortunately
the small number of female subjects in Langham’s study doesn’t allow confirming such
observation. Langham's study is based mainly on male subjects and therefore even the
empirical curves available in the literature, most of which were derived from such data to
evaluate the urinary and fecal excretion, primarily relate to Plutonium biokinetics in men. The
few curves, calculated from data other than Langham’s, as in Khokhryakhov et al. [114],
relate mainly to male subjects as well.
This reflects also the most realistic situations in nuclear professional environment
where most of the workers involved were and are of male gender. Therefore from now on the
present work will essentially consider the biokinetics of Plutonium in male adult subjects.
In order to study and develop a model for Plutonium biokinetics in humans the
experimental data we previously analyzed are of foremost importance. However, whereas for
the first 4-5 months after injection a certain number of measurements is available,
measurements on humans beyond this time are rare. Therefore the use of published excretion
functions becomes inevitable for evaluating Plutonium urinary excretion at long time after
intake. The choice of an empirical curve should comply with the following conditions:
• The number of data from which the curve was calculated should be as large as possible;
• The curve should agree with the few available experimental data for long time after
injection;
• Eventual good agreement of the empirical curve provided in the same study but relating
to other bioassays (such as Plutonium fecal excretion or blood contents) should be
considered.
For a preliminary qualitative comparison in Figure 3.1.1 and Figure 3.1.2 the daily
percentage of Plutonium excreted in the urine calculated from the various empirical curves is
presented together with the available measurements. It can be already seen as the former
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