Rand report on Depleted Uranium
http://www.vitalsource.org/gulfwar/govrep/rand2.htm
http://www.gulflink.osd.mil/library/randrep/du/
Source:
http://www.gulflink.osd.mil/library/randrep/du/mr1018.7.chap2.html
======================================================
This study is very misleading because DU IS very
different from natural uranium. (see commentary of
dr. L.A. Dietz on this subject)
Uranium bone concentration increases with age
A plot of the data for uranium in bone ash for the 12 countries is shown in
Figure 2.3. The bone ash data fit a log-normal distribution better than a
normal distribution. The geometric mean is 7.3 µg/kg ash (88 mBq 238U/kg
ash), with a geometric standard deviation of 4.2, indicating a very skewed
distribution. This spread is related to dietary habits and to the water
concentration in particular. The arithmetic mean of bone ash data is 11 ± 11
µg/kg ash (130 mBq 238U/kg ash) with a range of 0.4 to 51 µg/kg ash (5 to 610
mBq 238U/kg ash). In short, bone ash data provide an insight into the amount
of uranium that naturally distributes in the bone in various countries. We
find a 100-fold difference across countries, with concentrations increasing
with age. These data show that what is high in one area may be normal in
another but that areas with higher rates do not have known resulting adverse
health consequences. Given that depletion of uranium does not alter its
chemical properties, and that radiation from DU is less than from natural
uranium, exposure to DU at these levels would appear not to have known
adverse health consequences.
Dist------most in bone
Figure 2.5 shows the average distribution of 238U in the body from chronic
intake, calculated from Table 2.1 and standard organ weights (Fisenne, 1993).
The organ contents in decreasing amount are skeleton (380 mBq), muscle (132
mBq), fat (110 mBq), blood (25 mBq), lungs (12 mBq), liver (5.4 mBq), and
kidneys (2.4 mBq). The total body content is 670 mBq (56 µg).
Lung damage
Lung damage resulting from inhalation of uranium oxides is usually
noncancerous alveolar epithelium damage of type II cells. The responses to
chronic injury are hyperplasia, hypertrophy, and metaplasia (HHS, 1997b). In
animal studies, lung and tracheobronchial lymph node fibrosis was reported in
animals exposed by inhalation to 5.1 mg UO2/m3 (3.4 nCi/m3) for three years
(Leach et al., 1970).
Animal studies have also examined pulmonary damage from exposure to uranium
oxides. Exposure to 5 mg UO2/m3 for more than three years did not result in
damage to the lungs, but minimal fibrosis, suggestive of radiation injury,
was occasionally observed in the tracheobronchial lymph nodes of dogs and
monkeys and lungs of monkeys (Leach et al., 1970, 1973). Alpha radiation
doses were estimated to have been greater than 500 rads in the lungs and
greater than 7,000 rads in tracheobronchial lymph nodes. Lung fibrosis is
consistent with relatively short-term high exposure rate in animal
experiments.
Early studies of humans were conducted from about 1860 into the early 1900s,
during which time uranium was administered as a therapeutic agent for
diabetes because it had been shown to increase glucose excretion (Hodge,
1973).
Outside the military or industrial settings, the major portion of the natural
body burden of uranium for typical civilians is derived from ingested and
inhaled material. There is a limited amount of natural uranium in the air we
breathe, the food we eat, and water we drink. The origin of the uranium may
be natural, or it may have been contributed to the environment by man-made
sources, such as application of uranium-containing superphosphate fertilizer
to crop land or combustion of fossil fuel.
The schematic in Figure 2.2 depicts how uranium interacts with the body.
Inhaled, ingested, or embedded fragments reach the blood after solubilizing
either at the site of entry or at some other location in the body where they
end up. For instance, some inhaled uranium enters the blood from the lungs,
and some of the uranium originally in the lungs ends up in the
gastrointestinal tract as a result of mucociliary clearance from the
respiratory tract and subsequent swallowing. Uranium then accumulates to some
degree in all organs. As discussed, the major portion of uranium in blood is
excreted in the urine, with the remainder distributed mostly to bone and soft
tissue.[2] There are few data to show the content and distribution of uranium
in human tissue from inhalation and ingestion from natural sources. Fisenne
et al. (1988, 1993) summarized all of the published data for uranium in human
tissue and blood. The measurements are shown in Table 2.1. The normal range
for the total mass of uranium in a human being is 2-62 µg (ERDA, 1975; USUR,
1984; Wrenn, 1985; Fisenne, 1986; Fisenne, 1994).
GI effects resulting from high levels of inhalation have been reported. In a
case study, a male worker at a uranium-enrichment plant was accidentally
exposed in a closed room to inhalation of a high concentration of UF4
(estimated radioactivity of 187 nCi/m3) for about five minutes. Six days
after the accident, the patient reported dizziness, nausea, and loss of
appetite. On the ninth day after the accident, the clinical findings were
loss of appetite, abdominal pain, diarrhea, tenesmus, and pus and blood in
the stool. By the thirtieth day after the accident and at follow-up seven
years later, all clinical findings had returned to normal (Zhao and Zhao,
1990). The clinical findings were undoubtedly due to the chemical effects of
UF4. In corresponding animal studies, exposure to enriched uranium damaged
elements of the GI tract.
Natural uranium is inhaled daily in very small amounts by all persons.
Estimates made from measurements of air concentrations in New York City show
that about 1 µg of uranium is inhaled each year by each person. The source of
this uranium is mostly resuspended soil particles of very small diameter.
----------
[6]About 10 percent of the amount inhaled is solubilized and goes to the
blood where it is excreted or deposited in the kidney, liver, other organs,
and the skeleton.
[7]In autopsy results, excess uranium in organs of highly exposed
occupational workers (inhaling 40 to 50 mg of uranium) has been measured as
long as 38 years after exposure (Kathren and Moore, 1986).
[2]Deposition of the uranyl and other heavy-metal ions in bone is believed to
involve competition with calcium for reaction with superficial phosphate
groups. Some heavy-metal ions also replace calcium in the crystal structure
of bone (Voegtlin and Hodge 1949; Hursh and Spoor, 1973).
[3]The published data are reported in various units, particularly the
skeletal values. The reported concentration units are in micrograms or mBq,
per unit wet weight, per unit dry weight, per cubic centimeter of wet bone,
per unit ash weight, or per gram of calcium. In some cases it is not stated
whether the bone marrow was removed. It is of value to convert across the
various units to compare data, and data for different bone types. It is
necessary to convert to activity per unit wet bone when estimating radiation
doses to cells on bone surfaces, the targets for carcinogenesis. The
following data apply for osseous tissue (i.e., bone with normal water content
in hydroxyapatite plus the collagen matrix) (Fisenne et al., 1988).
Top
|