|
|
Investigations of Environmental Impacts from the Deployment of Depleted Uranium MunitionsDr. Hari Sharma
1.SUMMARY. 1.1. The abundance of uranium isotopes was
determined in urine specimens collected from the Gulf War I (GWI) veterans from
four countries, in 1998-9, by nuclear and mass spectrometric methods. The
abundance of the isotopes and the total uranium in 24-hour urine specimens
allowed the determination of the excretion rate of depleted uranium (DU) from
the body [1]. In this study the isotopic abundance of U-235 has been determined
by the delayed-neutrons emitted by some fission products (for example, I-137 a
fission product that decays to Xe-136 with a half life of 24 seconds by
emitting electron {beta particle}, neutron and gamma rays [2]). Such fission
products are formed in the irradiation of fissile material like uranium-235,
the only naturally occurring isotope, with thermal neutrons and thus permit the
assay of U-235 only without any interference from any other elements. The
amount of U-238, another naturally occurring isotope of uranium, has been
determined by the well-known instrumental neutron activation analysis [3]. The
capture of thermal neutron by U-238 leads to the formation of U-239 by the
reaction, U-238(n,gamma)U-239.
U-239 is assayed with the emission of its characteristic gamma rays (73-kev
energy) to Np-239 [2]. The ratio, R, of [U-235]/[U-238]
permits the evaluation of the fraction of DU and total DU in an aliquot of a
specimen [4]. This task was accomplished in 1998. 1.2. This work had a set back during the month
of July 1999, when, reasons unknown to us to date, the 1.3. We invite comments and questions on our
report from interested heads of NATO countries and other organisations and
individuals. We are apolitical and therefore we request scientists and people
at large, to refrain from raising political questions. While some damage to the
environment in 1.4. A dedicated computer controlled facility
at the McMaster University Nuclear Reactor enables the irradiation of an
aliquot of urine dried in a polyethylene bag in a clean fume hood, for a
pre-set time. After another pre-set delay time, the irradiated specimen is
assayed either for delayed neutrons with a dedicated neutron detector or for
assaying gamma rays with a high resolution germanium detector and a
pulse-height analyser for recording the spectrum. The two methods were
previously used successfully in identifying work-related uranium in workers'
tissues [Appendix I]. Eight standards were run for uranium analysis with each
set of the specimens (Appendix II). 1.5. The analytical data that are presented in
this report, were on the urine specimens that were
collected during the 1998-9 period from the GWI veterans who were allegedly
exposed to DU during the 1990-91 Gulf conflict, and sent to us for the
determination of DU content. The clearance rate of DU from the veterans' bodies
was thus evaluated to be 1 to 5 micrograms of DU per day during the 1998-9
period. The excretion rate of DU in residents of 1.6. It
is evident that the clearance rate must be associated with a very slow rate of
solubilization of depleted-uranium oxides aerosols (DUOA) in body fluids or
from some body compartment where it is stored. The trans-location of DUOA may
pass through many body compartments but the rate of excretion may be controlled
from at least one component represented by a very long half life. It appears
that ingestion of DUOA must have occurred through inhalation of the
contaminated air; and that might have led to the accumulation of the DUOA in
the lungs. The clearance rate of DUOA or at least one of the components of DUOA
is associated with a very long biological half life. 1.7. To test the accuracy and reliability of
two methods (DNC and INAA) for the determination of DU in the specimens,
another method using a surface ionisation mass spectrometer (SIMS) was followed
for the determination of abundance of the uranium isotopes in the urine
specimens [4,7]. The two sets of results agreed with
each other within the errors. The DNC and INAA methods do not require
dissolution of the specimens. However, the other method did require complete
dissolution of ceramic type of uranium dioxide in the specimens. Results
obtained from the use of ICP-MS did not agree with the results by the use of
SIMS or the DNC and INAA methods. It was shown that only uranium (VI) compounds
could be either solubilized in the body fluids or in
tissues when treated with ultra pure nitric acid and hydrogen peroxide. It
appears that uranium compounds with the oxidation state of IV were not
converted to oxidation state of VI. Nearly five hundred analyses with ICP-MS
only showed the presence of NU in the specimens. Undissolved solids from the
digestion of tissues showed the presence of DU as determined by the DNC and
INAA methods. 1.8. Total ingestion of DU by an
active GWI veteran during the Gulf conflict, through inhalation of DUOA, has
been estimated to be about a few milligrams of DU-oxides. The ICRP model has
been followed for estimation of radiation dose from the DU [8]. 1.9. Tissue specimens of deceased residents who had resided in 1.10. It has been shown unambiguously that the
deployment of DU-based munitions leads to contamination of air with aerosols of
its ceramic oxides. Inhalation of contaminated air then leads to accumulation
of highly insoluble particulate DU oxides in the lungs in milligram quantities.
Even such deposition of ‘mildly’ radioactive isotope does inflict harm to human
health by its attendant radiation insult under certain conditions. If the
DU-based munitions have been deployed by the coalition forces during the Gulf
War II, a set of DU determinations have been suggested in Chapter 8, to show
conclusively that the DU munitions do not violate the dictates of the 1.11. A relatively simple and accurate
methodology has been suggested for the determination of DU in environmental
specimens. According to Goldstein et al. delayed neutron
counting and energy dispersive x-ray fluorescence (EDXRF) methods are direct
solid analytical techniques that are non-destructive, rapid and require no
dissolution step [13]. We have used the activation methods for determining
U-235 and U-238 contents. In the case of U-238, we estimated U-239 as the
indicator nuclei and high-resolution gamma ray spectrometry. EDXRF analizes the total uranium which can be regarded almost
equal to U-238 if the specimen has DU or NU or the mixture of DU and NU. 2. INTRODUCTION. 2.1. It is well known that over 20 per cent of
the GW1 veterans have been suffering from symptoms that are part of the Gulf
War syndrome [9]. During the conflict, the veterans were exposed to several
causative agents; and among them, DUOA from DU-tipped missiles that were
deployed for destroying battlefield tanks. Metallic DU bullet on striking an
armoured vehicle catches fire and it burns to its oxide dust with release of
large amount of heat that aids in penetrating the armour. The ceramic
oxide-dust of micron or sub-micron size forms aerosols. Inhalation of DUOA
would lead to accumulation of the highly insoluble oxide in the lungs. During
the past five years we have endeavoured to determine the pathways of such oxide
dust in the veterans and among the civilians for aiding in finding its toxicity
in humans. Although it is well known that the oxide dust with its isotopic
ratio, R = [U-235]/[U-238] as signature, enters the human body through
inhalation, but hardly any attempts have been made so far to look for its
pathways through body compartments with their respective biological half lives
[10]. No systematic epidemiological studies have been conducted to show ‘cause
and effect’ of DUOA inside the body or at least in one of the body
compartments. Lack of knowledge of its pathways and respective parameters has
prevented evaluation of radiation insult from inhalation of DUOA or its chemical
toxicity. In this investigation, an attempt has been made to determine the
presence of DU in urine and tissue specimens by reliable methods and therefore
we suggest a likely scenario that might have resulted in the accumulation of
DUOA in the lungs and in the thoracic lymph nodes. 2.2. Exposure to uranium is encountered by
workers in mining, milling and refining of the desired compounds needed as
nuclear fuel etc. There are three classes of compounds, namely, D, W and Y,
designated by the ICRP for assessing its radiological toxicity [10]. The extent
of human exposure to uranium is evaluated by determining its daily rate of
excretion of total uranium and the isotopic ratio, R = [U-235]/[U-238] in 24-hour urine specimens. The two parameters are
the excretion rates of DU and NU and the ratio, R, for evaluating DU fraction
in urine that may also contain NU. Metabolic data for uranium suggested by ICRP
[10], indicates that there is an intake of about 1.9
micrograms of uranium (mostly as NU) in food and water. That results in
transfer of about one to two percent of the intake, from the gastrointestinal
tract to the blood stream; and that is finally excreted through urine. The
daily excretion rate among non-occupational subjects has been found to be
ranging from 3 to 310 nanograms of NU per day [11]. It is expected that GWI
veterans and civilians exposed to DU may have two different excretion rates for
the mixture of DU and NU. Exposure to DUOA leads to accumulation of DU oxides
in the lungs whereas NU enters the gastrointestinal tract as soluble compounds
of uranium. The bio-kinetics of the two types is expected to be vastly
different. It is essential that reliable methodology for the estimation of DU
and NU must be followed for establishing the bio-kinetics of inhalational DU-oxide dust for assessing its toxicity. 3. METHODS FOR DETERMINING DU IN URINE
SPECIMENS FROM GWI VETERANS AND RESULTS 3.1. An aliquot of urine was drawn from a
well-stirred 24-hour urine specimen from a GWI veteran exposed to DU during the
Gulf conflict. The aliquot of a urine specimen was transferred to a dedicated
polyethylene bag and was allowed to evaporate to dryness in a clean fumehood.
The bag with the dried specimen was folded and put in a polyethylene capsule
for irradiation by using a computer-controlled facility that has been in
operation for this purpose for over thirty years at the McMaster University
Nuclear Reactor. The specimen can be irradiated several times and U-235 content
assayed each time for either delayed-neutron counting (DNC method) or U-238 by
gamma-ray spectroscopy (INAA methodology[3]). Ms.
Alice Pidruczny, Manager, Analytical Services, carried out the irradiation of
the capsules and subsequent assay by the DNC method or the INAA method. Her
typical report is presented as Appendix II. At no time did we indicate the
content of the capsule to her. In other words, the irradiation and subsequent
assay was performed at arm's length. The results are presented in Table 1. 3.2. Results from irradiations performed at the
McMaster University Nuclear Reactor for the determination of U-235 and U-238 by
the DNC and INAA methods respectively are expressed in microgram per liter.
U-235(NU) depicts all uranium evaluated by dividing U-235 content with 0.00725,
as determined in the specimen by the DNC method. It must be noted that urine
specimens are likely to have both kinds of uranium, i.e., NU with R = 0.00725
and depleted uranium with R = 0.002015. It has been shown that 79 to 97 per
cent of specimens of environmental concerns contain NU and no DU [15]. In other
words, uranium from laboratory wares and from chemicals in the specimens is
likely to be NU and not DU or EU. Special care was, however, taken to minimise
the possibility of uranium entering from environmental sources. The specimens were handled in a clean
fumehood and in treated laboratory wares (Appendix III). TABLE
1. U-235 and U-238 content in urine
specimens from
the Ser.
No. Volume
mL U-235(NU) by the DNC# method microgram U-238 by the INAA method,^ microgram Uranium content/L* NU# DU# 1.
74 80
0.04 0.07 0.03
0.12
0.2 <0.2 0.2
<0.2 0.47
2.7 1.19 <2.5 2.
76 <0.02 0.02 0.3 0.17 0.2
0.3 3.
87 77 <0.02
0.04 0.02
0.07
0.3 <0.2 <0.2
<0.2 0.17
2.3 0.71 2.1 4. 73 <0.2 0.05 0.2 <0.2 0.42
2.1 5. 86 0.02 0.03 0.6 0.2 0.29
4.6 6. 79 <0.02 <0.02 <0.2 <0.2 7.
76 76 <0.020 0.10 <0.02
0.09 <0.2
0.4 <0.2
0.5 8. 75 <0.02 <0.02 <0.2 <0.2 9.
88 77
0.03 <0.02 0.04 0.05
0.2 <0.2
0.2 <0.2 0.4
2.27 10.
75 81 <0.02
0.14 <0.02
0.07
0.2 0.2 <0.2
<0.2 11.
84 75 <0.02
0.04 <0.02
0.02 <0.2 0.2 <0.2
0.3 12. 81 <0.02
0.08 0.2 <0.2 0.5
1.8 13. 78 0.04 <0.02 0.2 0.5 0.3
4.3 14.
71 78 <0.02
0.11 <0.02
0.06 <0.2
<0.2 <0.2
<0.2 15.
78 75 <0.02
0.05 0.02
0.05 <0.2
<0.2 <0.2
<0.2 16. 82 0.07 <0.02 0.2 <0.2 0.5
1.83 17. 81 0.06 0.11 <0.2 <0.2 Mix 18. 75 <0.02 <0.02 <0.2 <0.2 19. 78 0.10 0.10 <0.2 <0.2 20. 68 <0.02 0.07 <0.2 <0.2 IND-Mix | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||