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

adionuclide. For instance discrepancies in dose assessments of several orders of magnitude
are possible between via inhalation or ingestion hypotheses of intake [97]. Accidental events
such as damage on radiation protection facilities or errors in the manipulation activities can
provide information on the most probable time of intake. When such events can't be
determined, a continuous and constant rate of intake can be realistically assumed.
Path of intake and time modality can be better established if the information on the
scenario of the contamination is integrated with available workplace monitoring
measurements. For instance anomalous level of air radioactivity concentration can suggest a
probable contamination via inhalation. Furthermore if multiple stage impactors are used to
sample the air in the working area, aerosol size distribution can also be determined and
condition of exposure can be realistically quantified. Sometimes nose wipe measurements can
be a useful way of discriminating a prevalent contaminatiuon via inhalation. Information on
chemical form of contaminating compound can also be obtained from air or surface
monitoring measurements.
Availability of multiple kinds of measurements on contaminated subjects such as
direct and undirect measurements is extremely useful because they provide information on
model accuracy in describing the numerous physiological processes and on the truthfulness of
initial assumptions.
Information strictly related to the health status of the subjects are also important
because it was already observed that pathologies and illnesses can significantly change the
biokinetic of a radionuclide in human body. Examples were already given in Durbin’ and
Khokhryakov’s studies [106, 114] where significant enhancement of Plutonium urinary
excretion was observed in subjects with different health impairments.
Finally data sets must cover a time period comparable with the effective half life of the
radionuclide in human body. In fact the shorter is time series of available measurements, the
greater the possibility of fitting them with different models or the same model but with
different initial assumptions (time or path of intake, chemical and physical characteristics,
etc.). In the specific case of Plutonium and other long-lived radionuclides time series from
several years up to decades could be necessary.
Unfortunately few data sets relating to Plutonium occupational exposures comply all
the aforementioned conditions. Among those ones available in scientific literature, two main
data sets should be considered: Manhattan Project Workers (MPW) and United States
Transuranium and Uranium Registries (USTUR) data sets. The former is composed by the
results of the monitoring of twenty-five male subjects who worked with Plutonium at what is
now the Los Alamos National Laboratory (Los Alamos, New Mexico, US) in the days of the
Manhattan Project during World War II. They were engaged in different activities under
extraordinarily cruel working conditions and therefore with high risk of Plutonium exposure,
mainly from recovery operations. They have been monitored for a long time and, for some of
these subjects, medical follow-up and bioassay measurements are available up to recent years
[107, 108, 117, 118, 119, 120]. The second data set relates to workers generally engaged in
Plutonium industries [121], even if the societies or laboratories were they carried out their
activities are less clearly stated. Some of the subjects included in this data set can also be
found in Manhattan Project workers data set under different codes.
Among all the contamination cases reported in the these two data sets, a further
selection should be carried out in order to facilitate the use of them for verification purposes
of Plutonium urinary excretion predicted by a model.
Firstly, measurements of urinary excretion should be available because other kind of
bioassays (feces or blood) or direct measurements of activity in organs and tissues offer only
indirect information on urinary excretion. The measurements should be always higher then
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