URANIUM, RADIOACTIVE: Nuclear Power Plant Emissions
Major Uses :
Uranium-234: Dental fixtures; Uranium-235: Fuel for nuclear power plants and
naval nuclear propulsion systems, fluorescent glassware, colored glazes, and
wall tiles. /from table/ /Isotopes/
Major Uses :
Uranium-238. Used in dental fixtures like crowns and dentures to provide natural
color and brightness and in fuel for nuclear power plants and naval nuclear
propulsion. /Uranium-238/
Major Uses :
Uranium is used primarily in nuclear power plants; most reactors require uranium
in which the uranium-235 content is enriched from 0.72% to about 3%. /Uranium
NOS/
Other Hazardous Reaction :
Neutrons are primarily released from nuclear fission ... . The natural decay of
radionuclides does not include emission of neutrons. This is mainly a health
hazard for workers in a nuclear power facility or victims of a nuclear
explosion. Unique among the particles of radioactivity, when neutrons are
stopped or captured they can cause a previously stable atom to become
radioactive. This is the principle behind radioactive fallout.
General Manufacturing Information :
In both nuclear weapons and nuclear fuel production, after being mined and
milled, uranium must be converted to uranium hexafluoride gas, which is then
enriched and converted to uranium oxide or metal. If enrichment is carried to
about 90%, the uranium may be used to make nuclear weapons or to fuel naval
warships; alternatively, the uranium may be enriched by only a small percentage
for use in civilian nuclear energy facilities. Metallic uranium is capable of
reacting with both air and water exothermically; because of this reactivity, the
more stable uranium oxide is the most commonly used fuel in reactors. While this
form is more stable, it has poor thermal conductivity, necessitating the use of
small-diameter fuel rods. The fuel is in the form of high melting point ceramic
pellets, about 0.5 inches in diameter and 1 inch long, in which UO2-enriched to
3-4% uranium-235 is dispersed. These pellets are stacked end to end in zirconium
alloy or stainless steel tubes about 12 feet long (called cladding) and then
sealed to retain the fission products that are produced during operation. These
fuel filled tubes are then assembled in groups of 8 x 8 to 17 x 17 arrays into
fuel rod assemblies. About 500 of these assemblies make up the core of a nuclear
power reactor. For a frame of reference, a single pellet contains the energy
equivalent of about one ton of coal or 3 barrels of oil. /Uranium fuel/
Artificial Pollution Sources :
Combustion of coal is a significant source of enhanced natural radioactivity.
When coal is burned, some of the radioactivity is released directly to the
atmosphere, but a significant fraction is retained in the bottom ash. Enhanced
concentrations of uranium have been found on the ground around coal-fired power
plants(1).
Prior History of Accidents :
An incident occurred at a plant near Tomsk in the Russian federation in 1993 in
which individual exposures were low and few in number. The Tomsk site featured
one of Russia's three operating plutonium production reactors. The Tomsk
reactors were built to produce plutonium and to supply steam for the city's
district heating plant. Reprocessing, which involves the use of chemical
processes to separate uranium and plutonium from spent nuclear fuel, occurs at
the plant. Under certain conditions, the chemical solutions can cause an
explosion. In April 1993, a tank containing a blend of paraffin and tributyl
phosphate chemically exploded, resulting in the involuntary release of uranium,
plutonium, niobium, zirconium and ruthenium. The tank had a volume of 34.1 cu m,
and held 25 cu m of solution. The solution contained 8,773 kg of uranium, and
about 310 kg of plutonium. The total amount of radioactivity in the solution was
approximately 20.7 TBq (559.3 Ci). The explosion caused substantial damage to
the facility and contaminated a largely unpopulated area of about 123 sq km. The
release from the tank was estimated to be 4.3 TBq (115 Ci) of long-lived
isotopes. Radioactive material spread to the north-east and fallout was detected
over an area of 120 cu km. Gamma radiation 20 times higher than the norm was
measured in the area that received the most fallout. The personnel who assisted
in putting out the flames received the maximum radiation dose of 2 mSv (200 mrem).
The accident could have had more serious local consequences if the wind had
carried the contamination to two large nearby cities. ...Several operational
errors, such as improper mixing of chemicals in the reprocessing tank, and
possible design flaws, such as inadequate tank ventilation, were identified as
contributors to the accident.
Prior History of Accidents :
United Nuclear Fuels Recovery Plant, 24 July 1964 This accident occurred in a
chemical processing plant ... designed to recover highly enriched uranium from
scrap material ... shipped to the plant as uranyl nitrate solution in 55 gallon
drums . ... The uranyl nitrate was then purified and concentrated by solvent
extraction using tributyl phosphate mixed with kerosene as the organic wash.
After the final acid strip, the purified uranyl nitrate solution was bubbled
through a column containing a fixed charge of ... trichloroethane (TCE). ... /
On the day of the accident/ the operator assigned to work the solvent extraction
columns ... mistook a bottle/ containing high concentration solution for one
containing TCE. The bottle was transported by cart, and then hand carried...
After arriving ..., the operator poured the contents of the bottle into the
makeup vessel already containing sodium carbonate solution that was being
agitated by a stirrer. The critical state was reached when nearly all of the
uranium had been transferred. The excursion (1.0 to 1.1x10+17 fissions) created
a flash of light, splashed about 20% of the solution out of the vessel and onto
the ceiling, walls, and operator. The operator who fell to the floor, regained
his footing and ran from the area to an emergency building. ... An hour and a
half after the excursion, the plant superintendent and shift supervisor entered
the building with the intent of draining the vessel... the change in geometry...
apparently added enough reactivity to create a second excursion ... The
estimated yield of the second excursion was 2 to 3x10+16 fissions... That the
second excursion had occurred was not realized until dose estimates ... were
available. The supervisor received about 100 rad, while the superintendent
received about 60 rad. ... The radiation dose to the operator as a result of the
initial excursion was estimated to be about 10,000 rad. He died 49 hrs later.
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ A retrospective cohort study was conducted among 6,781
white male employees who had worked at /an/ Oak Ridge ... nuclear material
fabrication plant for at least 30 days during 1947-74; vital status was
determined for 6477 workers, and the cohort was followed-up until the end of
1979. Among 3,490 monitored workers, the mean cumulative alpha-particle dose to
the lung was 82 mSv (range, 0-3.1 Sv), and the mean cumulative external
whole-body penetrating dose from gamma-radiation was 9.6 mSv (0-4.3 Sv). When
compared with the rates for white men in the USA, the mortality rates from all
causes combined, cardiovascular diseases and from most site-specific cancers
were decreased. Increased rates of cancers of the lung, brain and central
nervous system were seen in comparison with national and state rates.
Dose-response trends were detected for death from lung cancer with respect to
cumulative exposure to alpha-particles and gamma-radiation, the most pronounced
trend being found for exposure to gamma-radiation among workers who received
> or = to 0.05 Sv of alpha-particles. ... No dose-response trend in mortality
from brain or central nervous system cancer was found. /Enriched uranium/
Preventive Measures :
A nuclear fission chain reaction in a reprocessing plant is an accident that
must be carefully guarded against. Although such a critical reaction is not
likely to generate sufficient energy to be mechanically destructive, it emits
intense neutron and gamma radiation that can kill nearby plant personnel and may
release radioactive fission products outside the plant. ... Nuclear criticality
safety has been codified in American National Standards published by the
American Nuclear Society, ... . Even after using these standards, the design or
operation of equipment in which fissile material is to be processed should be
reviewed for criticality safety by an expert. And even after such review, some
reprocessing systems may have novel features whose safety can be verified only
by experiment. /Fissile uranium and plutonium/
Methods of Manufacturing :
The first step in the process /of preparing uranium fuel/ is mining;
historically, this has involved subterranean or open-pit ore rock removal and
now also involves liquid in-situ leaching of unconsolidated deposits. ... The
next steps in the production of uranium fuel, aimed at concentrating the
uranium, are usually carried out near the mine to save on transportation costs.
... The product of these concentration steps contains perhaps 40-70% uranium by
weight and is generally shipped to a central processing plant to be further
refined. This purification is either by digestion with nitric acid and
extraction of the resulting uranyl nitrate into an organic solvent, or by
conversion to UF6 and fractional distillation of that volatile compound. At this
stage, all naturally occurring radioactive progeny have been removed from the
uranium which is considered to be chemically pure... . While some nuclear
reactor types ... use natural uranium as fuel, others require enriched uranium.
If such uranium-235 enrichment is required, the purified uranium in an
appropriate chemical form is transferred to an isotope separation plant. Isotope
separation of uranium-238, uranium-235, and uranium-234 may be achieved by a
number of processes including gaseous diffusion, centrifugal or laser
enrichment. The enriched uranium is then processed and fabricated into
appropriate forms for use in nuclear reactors. The by-product of this enrichment
process is depleted uranium, often in the form of UF6. /Uranium fuel/
Prior History of Accidents :
With the beginning of the nuclear age also came criticality events of varying
kinds where individuals were exposed to large amounts of radiation. Criticality
refers to the chain reaction of fissionable atoms that results in the release of
energy. It is the basic operating principle behind fission bombs and nuclear
reactors and is an efficient means of generating energy. Two criticality events
occurred in Los Alamos in 1945 during experiments in which scientists performed
what was called "tickling the dragon." In the 1940s determining the
amount of fissionable material necessary to precipitate a chain reaction was
less of a calculation and more trial and error. Harry Daghlian and Louis Slotin,
two scientists involved in the development of the first atomic bomb, were to
bring subcritical amounts of fissionable material together to see if a reaction
would occur. Both men died of ARS following exposure to high levels of radiation
released during these experiments. Since 1945, there have been numerous
criticality events, the most recent occurring in Tokaimura, Japan in 1999. In
this instance, workers making fuel for nuclear reactors allowed too much uranium
to enter an improper container. The critical event that resulted killed one
worker and caused the evacuation of all the people living within 350 meters of
the manufacturing plant.
Prior History of Accidents :
Oak Ridge Y-12 Plant, 16 June 1958 This accident occurred ... in a process
designed to recover enriched uranium, U(93) from various solid wastes. The solid
wastes would be dissolved in nitric acid, purified, concentrated, and then
converted to uranium tetrafluoride. A similar system, using newer technology,
had been installed and was operating... . However, because of delays in the
startup of the UF4 conversion equipment, the solution it produced was being
transferred ... for final conversion. ... Unknown to anyone at the time /of the
accident/, uranyl nitrate had been leaking /through a valve/ from the early hrs
of the previous shift until early afternoon when one of the operators checked
it. The operators completed the leak check and opened the valves to drain the
water into a drum. One operator remained near the drum to monitor the situation
for any unusual conditions. Because another valve was already ope, the flow
pattern from the vessels permitted the uranyl nitrate solution to precede the
water./ The operator looked into the drum and noticed yellow-brown fumes risking
from the liquid. He stepped away from the drum and within a few seconds saw a
flue flash indicating that an excursion had occurred. Almost immediately, the
criticality alarm sounded, and the building was evacuated. ... The most likely
source of initiation was neutrons from (alpha, neutron) with the oxygen in the
water. ... A reasonable estimate is that the first spike contributed 6x10+16
fissions of the total yield of 1.3x10+18 fissions. The second excursion ...
occurred in 14 seconds. ... The excursions for the next 2.6 minutes appear to
have been no greater than about 1.7 times the average power. ... Eight people
received significant radiation doses (461 to 28.8 rem). At least one person owes
his life to the fact that prompt and orderly evacuation plans were followed.
Toxicity Summary :
Uranium occurs in granite, metamorphic rock, lignite, monazite sand, and
phosphate deposits at concentrations on the order of 0.5 to 5 ppm. All uranium
isotopes are radioactive. Uranium nitrate, sulfate, chloride, fluoride, and
acetate are either soluble in water or dissolved by dilute acids. Several uanium
oxides (e.g., uranium dioxide (UO2), uranyl oxide (UO3), uranium octoxide (U3O8)
have very low solubility in water. ... Uranium can exist in valences of +3, +4,
+5, or +6, but U+6 is the most stable, and it exists principally as the uranyl
cation (UO2)+2. The uranyl compounds (+6) are of most importance biologically
because the uranic compounds (+4) are usually oxidized to +6 during absorption
into the body. Natural uranium, by itself, will not sustain a nuclear chain
reaction; however, in the presence of a moderator or enrichment with less stable
nuclides such as uranium-235, it may do so (2). Daily intake of uranium in food
and water varies from approximately 1- 5 ug U/d daily in uncontaminated regions
to 13-18 ug/d or more in uranium mining areas. A 70 kg, non-occupationally
exposed 'Reference Man' living in Europe or in the United States has an
estimated total body uranium content of about 22 ug. Uranium is absorbed from
the intestine or by the lungs, enters the bloodstream, and is rapidly deposited
in the tissues, predominantly kidney and bone, or excreted in the urine. Renal
toxicity is a major adverse effect of uranium, but the metal has toxic effects
on the cardiovascular system, liver, muscle and nervous system as well (1).
Uranium accumulates in bone in a manner similar to that of radium; therefore,
its alpha particles would presumably be nearly as effective in the production of
osteogenic sarcomas. Sarcomas have been produced in mice after exposures to high
specific activity uranium-232 and uranium-233 (2). According to the ACGIH, there
is debate as to what acute concentration of uranium in the kidney constitutes
the NOAEL. Substantial damage has been found when the renal uranium
concentration exceeded 3 ug/g in rodents. Other studies indicate that 2 ug/g in
the rat kidney causes transient proteinuria. Morrow and associates in 1982
calculated that 0.3 ug/g was a threshold concentration for acute renal injury in
the dog. This value has been challenged on the grounds that the half-life value
used by Morrow et al was too long. Renal toxicity in rats... has been detected
at 1 ug U/g wet weight after treatment with 5 ug U/day for 14 days. The basis of
the uranium-induced renal toxicity is related to (UO2)+2 competition for Mg+2
and Ca+2 adenosine-5'triphosphate (ATP) binding sites and subsequent disruption
of active transport in the cells of the proximal tubule and associated
structures. Toxicity to the lungs may also be associated with alpha radiation
from inhalation of insoluble forms of uranium. Chronic inhalation by monkeys,
dogs, and rats of natural uranium as UO2 at 25 mg/cu m resulted in pulmonary
fibrosis and malignant pulmonary neoplasia; the latter appeared to be a direct
result of alpha radiation. A series of studies at a uranium enrichment plant
noted an excess of lung cancer deaths among 18,869 white male workers and an
excess of death from central nervous system (CNS) cancer. Subsequent
case-control studies found a relationship between lung cancer and work exposure
but failed to find such a relationship with cancer of thee CNS. A more recent
follow-up confirmed the excess deaths from lung and CNS cancers in this cohort
and found excess deaths from renal cancer, lymphosarcomas and multiple myeloma.
For lung cancer, but not for the other cancers, a dose-response relationship was
found, an observation consistent with the lung cancers among dogs chronically
exposed to uranium. These data suggest that radiation is the limiting factor for
enriched or insoluble uranium (2). One effect of exposure to ionizing radiation
is to reduce regeneration of injured tissue, an observation that may account for
the finding that radiation enhances the toxicity of uranium for the kidneys of
mice and dogs (2). According to Taylor and Taylor, any possible direct risk of
cancer or other chemical- or radiation-induced health detriments from uranium
deposited in the human body is probably less than 0.005% in contrast to an
expected indirect risk of 0.2% to 3% through inhaling the radioactive inert gas
radon, which is produced by the decay of environmental uranium-238 (1).
Other Chemical/Physical Properties :
DECAY PATHWAY: Uranium-235, half-life 7.038X10+8 years, decays via alpha
emission, 4679 keV (55% 4398 keV; 5.7% 4215 keV; 5.0% 4596 keV) and gamma
emission (abs intensities: 57.2% 185.7 keV; 10.96% 143.8 keV) to thorium-231,
half-life 25.52 hours. Thorium-231 decays via beta(-) emission, 0.389 MeV (35%,
305 keV maximum, 85.1 keV average; 37%, 288 keV maximum, 79.9 keV average;
12.8%, 206.1 keV maximum, 55.7 keV average; 12%, 287.3 keV maximum, 79.6 keV
average) and 12% gamma emission (abs intensities: 14.5% 25.6 keV; 6.6% 84.2 keV)
to protactinium-231, half-life 32,760 years. /Uranium-235 and its progeny/
Radiation Limits & Potential :
DECAY PATHWAY: Uranium-235, half-life 7.038X10+8 years, decays via alpha
emission, 4679 keV (55% 4398 keV; 5.7% 4215 keV; 5.0% 4596 keV) and gamma
emission (abs intensities: 57.2% 185.7 keV; 10.96% 143.8 keV) to thorium-231,
half-life 25.52 hours. Thorium-231 decays via beta(-) emission, 0.389 MeV (35%,
305 keV maximum, 85.1 keV average; 37%, 288 keV maximum, 79.9 keV average;
12.8%, 206.1 keV maximum, 55.7 keV average; 12%, 287.3 keV maximum, 79.6 keV
average) and 12% gamma emission (abs intensities: 14.5% 25.6 keV; 6.6% 84.2 keV)
to protactinium-231, half-life 32,760 years.
Other Chemical/Physical Properties :
DECAY PATHWAY: Uranium-238, half-life 4.468X10+9 years, decays via alpha
emission, 4270 keV (79.0% 4198 keV; 20.9% 4151 keV) to thorium-234, half-life
24.10 days. Thorium-234 decays via beta(-) emission (70.3%, 198.5 keV maximum,
52.7 keV average; 19.2%, 103.7 keV maximum, 27.0 keV average) to
protactinium-234, half-life 6.75 hours. Protactinium-234 decays via beta(-)
emission (33.0%, 471.5 keV maximum, 137 keV average; 19.4%, 642.4 keV maximum,
194 keV average; 12.4%, 472.1 keV maximum, 137 keV average) to uranium-234,
half-life 245,500 years /Uranium-238 and its progeny/
Radiation Limits & Potential :
DECAY PATHWAY: Uranium-238, half-life 4.468X10+9 years, decays via alpha
emission, 4270 keV (79.0% 4198 keV; 20.9% 4151 keV) to thorium-234, half-life
24.10 days. Thorium-234 decays via beta(-) emission (70.3%, 198.5 keV maximum,
52.7 keV average; 19.2%, 103.7 keV maximum, 27.0 keV average) to
protactinium-234, half-life 6.75 hours. Protactinium-234 decays via beta(-)
emission (33.0%, 471.5 keV maximum, 137 keV average; 19.4%, 642.4 keV maximum,
194 keV average; 12.4%, 472.1 keV maximum, 137 keV average) to uranium-234,
half-life 245,500 years
Major Uses :
Source of fissionable isotope uranium-235; source of plutonium by neutron
capture, electric power generation. /Natural uranium/
Plant Concentrations :
Uranium-238 was detected in the tissue of grasses, mixed forbs, and big
sagebrush collected at various sites around an uranium mining and milling
operation in Wyoming. Concentrations were 130 mBq/g in tissue of plants growing
at the edge of a tailing impoundment and 407 mBq/g in plants growing on bare
tailings. The background concentration of uranium-238 in plants was 4.4 mBq/g(1).
Non-Human Toxicity Excerpts :
/OTHER TOXICITY INFORMATION/ In addition to its natural presence at high
concentrations in some areas, uranium has several civilian and military
applications that could cause contamination of human populations, mainly through
chronic ingestion .... The present study ... evaluated rats chronically exposed
to depleted uranium in their drinking water (1 mg/(rat-day)) for 9 months. ...
CYP3A1 mRNA expression was significantly higher in the brain (200%), liver
(300%), and kidneys (900%) of exposed rats compared with control rats, while
CYP3A2 mRNA levels were higher in the lungs (300%) and liver (200%), and CYP2B1
mRNA expression in the kidneys (300%). Expression of CYP1A1 mRNA did not change
significantly during this study. /The nuclear receptor/ PXR mRNA levels
increased in the brain (200%), liver (150%), and kidneys (200%). Uranium caused
/nuclear receptor/ CAR mRNA expression in the lungs to double. Expression of
/the nuclear receptor/ RXR mRNA did not change significantly in the course of
this study, nor did the hepatic activity of CYP2C, CYP3A, CYP2A, or CYP2B.
Uranium probably affects the expression of drug-metabolizing CYP enzymes through
the PXR and CAR nuclear receptors. /Depleted uranium/
Probable Routes of Human Exposure :
Occupational exposure to uranium may occur through inhalation and dermal contact
with this compound at workplaces where uranium is produced or used(SRC). Some
operations in which exposure to uranium compounds may occur is through the
liberation of these compounds from mining, grinding, and milling of ores, use of
insoluble compounds as chemical intermediates in preparation of uranium
compounds, use for nuclear technology, use in nuclear reactors as fuel and to
pack nuclear fuel rods, liberation from burning of uranium metal chips and
smelting operations, use as catalysts for many reactions and in the production
of fluorescent glass(1-3). The general population may be exposed to uranium via
ingestion of food(4) and drinking water(5) with these compounds and from
deployment of nuclear warheads containing uranium(SRC).
Absorption, Distribution & Excretion :
Inhalation hazards from uranium result primarily from the alpha emissions.
Inhalation of uranium particles and deposition into the respiratory system are
dependent on particle size. ... Uranium in the lungs has been shown to exhibit a
wide range of retention values. Clearance may occur through physical processes
removing particles that are not embedded into the lung by cilia motion to the
esophagus. Uranium particles that are soluble in lung fluid are chemically
dissolved, and the ions are transported into the bloodstream where they are
further distributed. Uranium particles remaining in the lung constitute a
potential radiological hazard as they impart their alpha emission energy into
the surrounding absorbing tissue, potentially causing significant damage within
a small sphere around each particle. Particles removed from the lung to the
bloodstream primarily represent a potential chemical hazard. The significance of
these hazards is evaluated using models of uptake and removal recommended by
national and international scientific radiation protection organizations. The
lung model described in ICRP Publication 66 (ICRP 1994) uses solubility Types of
F (fast), M (moderate), and S (slow). In comparison to previous models, this
model better describes deposition, retention, and clearance data and decouples
physical and chemical clearance processes. /Uranium particles/
Analytic Laboratory Methods :
Total uranium may be determined by gross alpha analysis. Individual
radionuclides of uranium, uranium-234, uranium-235, and uranium-238, can be
determined by their alpha-particle emissions. Mass spectrometry also can be used
for longer-lived isotopes of uranium. Uranium radionuclides are collected by
evaporating the sample to dryness on a stainless steel planchet, by
microprecipitation with a carrier, such as lanthanum or cerium fluoride, or
electrodeposition on a platinum or stainless steel disc. In each of these
techniques, care must be taken to ensure that a single oxidation state is
achieved for the uranium prior to the collection technique. Total alpha activity
is determined with a gas-flow proportional counter or an alpha liquid
scintillation system. Individual radionuclides are measured by alpha
spectrometry. Alpha emissions from uranium-232 are used as a tracer to determine
chemical recovery. /Uranium isotopes/
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ ... a cohort of 18,869 white men ... had been employed
between 1943 and 1947 at a uranium conversion and enrichment plant in Oak Ridge,
Tennessee, USA, and /were/ followed-up until 1974. Workers in certain
departments (especially chemical workers) were exposed to high average air
concentrations of uranium dust (up to 500 ug/cu m of air in 1945). In comparison
with mortality rates for white men in the USA, the standard mortality rationss
for various causes in the entire cohort were generally < 1.00. After
correction for unascertained deaths and missing death certificates, the SMR for
lung cancer was 1.22 (95% CI, 1.10-1.36). Adequate data on smoking habits were
not available in this study. The SMRs for various causes, including lung cancer,
did not tend to be higher among 8,345 workers who were employed in areas where
uranium dust was present or among 4,008 of these 8,345 workers who were employed
for one year or longer at the plant. ... /Uranium dusts/
Ecotoxicity Excerpts :
/FIELD STUDIES/ Assessment of the risk of impact from most radionuclides is
based on the total radiological dose rate to the organism of concern. However,
for uranium there can be greater risk from chemical toxicity than radiological
toxicity (depending on the isotopic composition). Chemical ecotoxicity of
uranium is dependent on several environmental parameters. The most important are
carbonate content, because of the formation of soluble carbonate complexes, and
divalent cation content (Ca++ and Mg++), because of their competitive
interaction with the uranyl ion (UO2++). This study summarizes the literature
available to set PNECs (predicted no-effect concentrations) for chemical
toxicity of uranium to non-human biota. The corresponding radiological doses
were estimated, and as expected chemical toxicity proved to be the greater
concern. There were limited data from some types of biota; however, PNECs for
the types of biota of interest were as follows: terrestrial plants - 250 mg U/kg
dry soil; other soil biota - 100 mg uranium/kg dry soil; freshwater plants -
0.005 mg uranium/L water; freshwater invertebrates - 0.005 mg uranium/L water;
freshwater benthos - 100 mg uranium/kg dry sediment; freshwater fish at water
hardnesses of: <10 mg CaCO3 /L (very soft water) - 0.4 mg uranium/L water; -
10 - 100 mg CaCO3 /L (soft water) - 2.8 mg uranium/L water; and - >100 mg
CaCO3/L (hard water) - 23 mg uranium/L water; or - as a function of hardness -
0.26 (hardness as mg CaCO3/L); mammals - 0.1 mg uranium/kg body weight/day.
/Uranium compounds/
Artificial Pollution Sources :
During a 3 to 4 year period, concn of uranium-238, uranium-234, thorium-230,
thorium-232 and thorium-238 were determined in soils and native vegetation at
various sites around a typical uranium mining and milling operation in Wyoming.
Plant/soil concn ratios for uranium and thorium isotopes were estimated for (1)
exposed, weathered tailings, (2) the edge of a tailings impoundment, (3) an area
downwind from exposed tailings, (4) a reclamation area and (5) several
background, native range locations. The uranium-238/uranium-234 concn ratio of
0.9 to 1.1 in soil and vegetation indicated near-radioactive equilibrium of both
radionuclides at all locations. Mean conc of the uranium and thorium isotopes in
background soil ranged from 44 to 52 mBq/g. Concns of uranium-238 and
thorium-230 in soil and vegetation were elevated above background at all sites
disturbed by mining and milling activities. Uranium conc in tailings and
invading vegetation were an order of magnitude greater than in the background
locations, whereas thorium-230 concns were elevated above background by some two
orders of magnitude. No demonstrable differences in radionuclide concn between
plant groups and collection years were found. The observed concentration ratio
values for uranium-238 and thorium-230 of 0.81 and 0.69, respectively, for
vegetation growing on exposed tailings were elevated above native range by
factors of 9.0 and 3.6, respectively, and generally higher than other published
values. Exceptionally high concentration ratio values for thorium-230 (1.9-2.9)
observed near the tailings impoundment demonstrate that under certain
conditions, vegetation can accumulate thorium-230 to a much greater extent than
previously reported. Vegetation concns were lower for thorium-232 relative to
thorium-230 and thorium-228 at locations where they are present at similar soil
concns.
Environmental Fate :
TERRESTRIAL: During a 3 to 4 year period, concn of Uranium-238, Uranium-234,
Thorium-230, Thorium-232, and Thorium-228 were determined in soils and native
vegetation at various sites around a typical uranium mining and milling
operation in Wyoming. Plant/soil conc ratios for uranium and thorium isotopes
were estimated for (a) exposed, weathered tailings, (b) the edge of a tailings
impoundment, (c) an area downwind from exposed tailings, (d) a reclamation area
and (e) several background, native range locations. The Uranium-238/Uranium-234
conc ratio of 0.9 to 1.1 in soil and vegetation indicated near-radioactive
equilibrium of both radionuclides at all locations. Mean conc of the uranium and
thorium isotopes in background soil ranged from 44 to 52 mBb/g. Conc of
Uranium-238 and Thorium-230 in soil and vegetation were elevated above
background at all sites disturbed by mining and milling activities. Uranium conc
in tailings and invading vegetation were an order of magnitude greater than in
the background locations, whereas Thorium-230 conc were elevated above
background by some two orders of magnitude. No demonstrable differences in
radionuclide conc between plant groups and collection years were found. The
observed concentration ratio values for Uranium-238 and Thorium-230 of 0.81 and
0.69 for vegetation growing on exposed tailings were elevated above native range
by factors of 9.0 and 3.6, respectively, and generally higher than other
published values(1).
Major Uses :
Used in nuclear fuels, compass components, x-ray agents, and in nuclear weapons
/Radioactive uranium/
Antidote and Emergency Treatment :
A critical reaction involving nuclear fuel or the detonation of a nuclear
weapons emits intense neutron and gamma radiation that can kill nearby personnel
and release large quantities of fission products into the surrounding
environment. Specific procedures for the emergency treatment and medical
follow-up of persons exhibiting Acute Radiation Syndrome (ARS) are provided in
the IONIZING RADIATION record.
Absorption, Distribution & Excretion :
As part of an epidemiological study, doses from intake of radionuclides were
estimated for workers employed during a 52-year period at the Rocketdyne/Atomics
International facility in California. The facility was involved in a variety of
research programs, including nuclear fuel fabrication, spent nuclear fuel
decladding, and reactor operation and disassembly. Most of the documented
intakes involved inhalation of enriched uranium (U), fission products, or
plutonium (Pu). Highest doses were estimated for a group of workers exposed to
airborne uranium aluminide (UAl(x)) during the fabrication of reactor fuel
plates. Much of the exposure to UAl(x) occurred early in the fuel fabrication
programme, before it was recognized that intake and lung retention were being
underestimated from urinary data due to an unexpected delayed dissolution of the
inhaled material. In workers who had been removed from exposure, the rate of
urinary excretion of U increased for a few months, peaked, and then declined at
a rate consistent with moderately soluble material. This pattern differs
markedly from the monotonically decreasing absorption rates represented by the
default absorption types in the Human Respiratory Tract Model (HRTM) of the
International Commission on Radiological Protection (ICRP). This paper
summarizes the findings on the behavior of UAl(x) in these workers and describes
material-specific parameter values of the HRTM based on this information.
/Uranium aluminide/
Impurities :
The natural uranium isotopes decay by alpha emission. The decay products are
also radioactive and form "decay chains " that ultimately lead to a
stable isotope of lead. /Uranium progeny/
General Manufacturing Information :
Working level (WL): any combination of short-lived radon daughters in one liter
of air that will result in the emission of 1.3x10+5 MeV of potential energy.
Working-level month (WLM): a unit of exposure to air concentrations of potential
energy released from radon daughters. One working-level month is defined as the
exposure to an average of 1 WL for a working month of 170 hours.
Other Chemical/Physical Properties :
Uranium-233, half-life 158,500 years, decays via alpha emission, 4.729 MeV, to
thorium-229, half-life 7,340 years.
Other Chemical/Physical Properties :
Uranium-234, half-life 244,500 years, decays via alpha emission, 4602 MeV, to
thorium-230, half-life 77,000 years
Other Chemical/Physical Properties :
Uranium-235, half-life 7.04X10+8 years, decays via alpha emission, 4.155 MeV, to
thorium-231, half-life 25.52 hours
Other Chemical/Physical Properties :
Uranium-238, half-life 4.468X10+9 years, decays via spontaneous fission and
alpha emission, 1.889 and 4.042 MeV, repectively, to thorium-234, half-life
24.10 days
Other Chemical/Physical Properties :
Uranium-239, half-life 23.54 minutes hrs, decays via beta(-) emission, 1.809 MeV,
to neptunium-239, half-life 2.355 days
Other Chemical/Physical Properties :
Uranium-240, half-life 14.1 hrs, decays via beta(-) emission, 0.1015 MeV, to
neptunium-240, half-life 65 minutes
Preventive Measures :
The uranium isotopes (viewed as contaminants) that will increase due to the
recycled uranium feed are 232-U, 234-U, and 236-U. The health and safety risks
of 236-U are similar to those of natural uranium because its specific activity
and radiation emissions are similar. ...The isotope in recycled uranium
presenting the greatest potential radiological hazard from external sources is
232-U. 232-U a daughter product of neutron activation of 231Pa. The health
hazards of 232-U are primarily due to the rapid buildup of gamma activity of its
decay products, particularly from 228-Th /and the presence of 232-U may need to
be considered to provide adequate worker protection/. /Recycled uranium feed/
Radiation Limits & Potential :
DECAY PATHWAY: Uranium-233, half-life 159,200 years, decays via alpha emission,
4,909 keV (84.4% 4824 keV; 13.2% 4783 keV)), to thorium-229, half-life 7,340
years.
Radiation Limits & Potential :
DECAY PATHWAY: Uranium-234, half-life 245,500 years, decays via alpha emission,
4859 keV (71.4% 4775 keV; 28.4% 4722 keV), to thorium-230, half-life 75,380
years
Medical Surveillance :
In vivo analysis is most useful for characterizing inhalation exposure of class
W /(retention in weeks)/ or Y /(retention in years)/ compounds of uranium by
lung counting. /The level at which assurance of detection occurs/ are generally
not sufficiently low to provide reliable information about systemic distribution
of soluble uranium at occupational levels. The 235-U decays with emission of an
energetic (186-keV) photon in high abundance that is used for in vivo monitoring
of enriched uranium workers. The other long-lived uranium isotopes emit only low
yields of low-energy photons (<60 keV), which are easily attenuated by body
tissue and have limited usefulness for in vivo analysis. Internal exposures to
aged depleted uranium can be measured in vivo by taking advantage of several
photons of moderate energy (63 to 93 keV) emitted by the 234m-Pa daughter of
234-Th, which are both short-lived daughters of 238-U. /Radioactive uranium/
Human Toxicity Excerpts :
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ At the highest doses in the domain of
10,000 rads (100 gray), the reaction is immediate. One example is that of an
individual who worked in a uranium-235 recovery plant ... He inadvertently
poured a container held under his left arm, filled with a solution of
uranium-235-enriched uranium, into a barrel already containing a similar
solution. He apparently lost track of how much fissionable material the barrel
contained. The amount he added exceeded criticality. There was a blue flash as
the liquid exploded, and he was drenched with the radioactive fluid. He
immediately became disoriented. His coworkers did a partial decontamination. He
was taken by ambulance to a series of hospitals which refused admission. An
admitting hospital was finally located, and he was installed in an evacuated
emergency ward, placed on a rubber sheet and further decontaminated by sponging
with wet towels. During the night, his blood pressure dropped sufficiently to
warrant continuous intravenous vasopressor medication. The next morning, his
left arm and the left side of his face abruptly became severely edematous. In
spite of the vasopressor medication, he went into irreversible shock and died
that afternoon about 22 hr after exposure. This pattern is known as the central
nervous system/cardiovascular syndrome. /U-235 enriched uranium/
Human Toxicity Excerpts :
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ A criticality accident occurred on
September 30, 1999, at the uranium conversion plant in Tokai-mura
(Tokai-village), Ibaraki Prefecture, Japan. When the criticality occurred, three
workers saw a "blue-white glow," and a radiation monitor alarm was
sounded. They were severely exposed to neutron and gamma-ray irradiation, and
subsequently developed acute radiation syndrome (ARS). One worker reported
vomiting within minutes and loss of consciousness for 10 to 20 seconds. This
worker also had diarrhea an hour after the exposure. The other worker started to
vomit almost an hour after the exposure. The three workers, including their
supervisor, who had no symptoms at the time, were brought to the National Mito
Hospital by ambulance. Because of the detection of gamma-rays from their body
surface by preliminary surveys and decreased numbers of lymphocytes in
peripheral blood, they were transferred to the National Institute of
Radiological Sciences (NIRS), which has been designated as a hospital
responsible for radiation emergencies. Dose estimations for the three workers
were performed by prodromal symptoms, serial changes of lymphocyte numbers,
chromosomal analysis, and sodium-24 activity. The results obtained from these
methods were fairly consistent. Most of the data, such as the dose rate of
radiation, its distribution, and the quality needed to evaluate the average
dose, were not available when the decision for hematopoitic stem cell
transplantation had to be made. Therefore, prodromal symptoms may be important
in making decisions for therapeutic strategies, such as stem-cell
transplantation in heavily exposed victims. /Enriched uranium/
Human Toxicity Excerpts :
/CASE REPORTS/ /KIDNEY/ Delayed renal effects were observed after a male worker
at a uranium enrichment plant was accidentally exposed to a high concentration
of uranium tetrafluoride powder for about 5 minutes in a closed room. While
renal parameters were normal during an initial 30-day observation period, the
patient showed signs of nephrotoxicity beginning at post-accident day 68 as
indicated by significantly elevated levels of urinary proteins, nonprotein
nitrogen, amino acid nitrogen/creatinine, and decreased phenolsulfonpthalein
excretion rate. These abnormalities persisted through day 1,065 but gradually
returned to normal values. The authors used uranium urinalysis data and a
pharmacokinetic model to estimate a kidney dose of 2.6 ug uranium/g kidney on
post-accident day 1. /Uranium tetrafluoride powder/
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ The association between exposure to uranium dust and
death from lung cancer was investigated among workers who had been employed for
at least 183 days in any of four /U.S./ uranium processing or fabrication plants
... . Among workers who had potentially been followed-up for at least 30 years,
787 deaths from lung cancer were identified from death certificates. One control
was matched to each case on race, sex and birth and hire dates within three
years. Health physicists estimated the annual doses to the lung from exposure
primarily to insoluble uranium compounds for each person ... . The odds ratios
for death from lung cancer for seven groupings of the cumulative internal dose
to the lung showed no increase in risk with increasing dose. There was a
suggestion of an effect of exposure for workers who had been hired at the age of
45 years or older. Further analyses with the cumulative external doses of
thorium, radium and radon did not reveal a clear association between exposure
and increased risk, nor did categorization of the workers by facility ... .
/Uranium dusts/
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ In a retrospective cohort study of mortality in 995 white
men who had been employed for more than 30 days at a uranium processing facility
in upstate New York between 1943 and 1949 ... increased standardized mortality
ratios (SMR) were observed for all causes of death (SMR, 1.18; 95% CI,
1.07-1.30, 429 deaths), laryngeal cancer (SMR, 4.47; 95% CI, 1.44-10.43; five
deaths), all circulatory disease (SMR, 1.18; 95% CI, 1.04-1.35, 227 cases),
arteriosclerotic heart disease (SMR, 1.19; 95% CI, 1.01-1.39, 159 cases), all
respiratory disease (SMR, 1.52; 95% CI, 1.04-2.14, 32 cases) and pneumonia (SMR,
2.17; 95% CI, 1.26-3.47, 17 cases). No association was found with length of
employment or work in the most hazardous areas of the plant. The rate of death
from lung cancer was not increased (SMR, 0.97; 95% CI, 0.60-1.48, 21 cases). The
internal doses from uranium were given only for the lung: 40% of the cohort
received 10-100 mSv/year and 38% received >100 mSv/year; the remainder of the
cohort received <10 mSv/year, or the value was unknown. /Radioactive uranium,
NOS/
Human Toxicity Excerpts :
/OTHER TOXICITY INFORMATION/ Several studies have been conducted of uranium
millers and of individuals involved in other uranium processing operations. ...
These workers are not exposed to high concentrations of radon gas in air but may
be exposed to alpha and beta-particles from inhaled or ingested uranium dust.
Inhalation of insoluble uranium particles is the major pathway for exposure of
the lung. ... Some studies of workers in uranium processing plants thus showed
an elevated rate of mortality from lung cancer, but the finding was not
consistent in all studies. The doses to the lung were relatively low. The rates
of death from cancers at other sites were increased in some studies, but the
small number of cases and lack of consistency between the findings reduce their
significance. /Inhaled and ingested uranium dust/
Environmental Fate/Exposure Summary :
Natural uranium consists of isotopic mixtures of uranium-234, uranium-235, and
uranium-238. Uranium may be classified into three categories based on the
percentage composition of each of the three isotopes: natural uranium, enriched
uranium, and depleted uranium. Natural uranium, including uranium ore, is
comprised of 99.284% uranium-238, 0.711% uranium-235, and 0.005% uranium-234 by
mass. Uranium may be introduced into the atmosphere in the natural process of
erosion and wind activity or by the intentional or accidental release of uranium
from mining and milling activities, by uranium processing facilities, or by
burning coal. Natural processes or human activities may alter the normal crustal
distribution of naturally occurring radioactive materials, resulting in what has
been termed technologically enhanced naturally-occurring radioactive material (TNORM).
No new radioactivity is produced by the enhancement, but uranium, its isotopes,
and its progeny are redistributed in such a way that real exposure or the
potential for human exposure may increase. Uranium enrichment and fuel
fabrication facilities also release small amounts of uranium to the atmosphere.
Contamination of surface water and groundwater by effluents from uranium mining,
milling, and production operations has been documented. Contamination of
groundwater and surface water can also occur by water erosion of tailings piles.
Uranium may also be released from radioactive waste disposal sites. Uranium
radionuclide concentrations in ground waters from the Hanford Site (Richland,
WA) indicate that uranium is highly sorbed. The phosphate rocks of Florida and
southeastern Idaho and neighboring areas contain as much as 120 ppm uranium.
Trace amounts of uranium progeny remaining in the fertilizer result in the
distribution of about 120 Ci (180 metric tons) per year over U.S. agricultural
lands. Combustion of coal is a source of enhanced natural radioactivity. When
coal is burned, some of the radio-uranium is released directly to the
atmosphere; however, a large fraction is retained in the bottom ash. Sampling of
soils and vegetation around a typical uranium mining and milling operation in
Wyoming suggest that plants may accumulate uranium isotopes. Uranium sorption is
likely due to its reduction from the hexavalent state, where it is introduced
via surface waters, to the tetravalent state found in the confined aquifers. The
distribution of radionuclides is very similar in all of the confined aquifiers
and significantly different from the distribution observed in the unconfined and
surface waters. (SRC)
Other Environmental Concentrations :
The mining and milling of uranium produce large quantities of low-level
radioactive waste(1). In a study of German mineral water, the measured uranium
concns ranged from 0.04-60 ug/l(2). Uranium-238 was found as a contaminant in
phosphate fertilizers used in Saskatchewan, Canada ranging from 0.01-174.56
mg/kg(3). It was shown that 7-9% of uranium in these fertilizers is available to
plants for uptake(3). Uranium was detected in municipal sludges from various
cities across the United States in 1980 ranging from none detected to 27 ppm
(dry weight)(4). The highest concns were found in sludge samples taken from Los
Angeles, California, Philadelphia, Pennsylvania, and Seattle, Washington(4).
Methods of Manufacturing :
Fluorine is used in the nuclear energy industry to produce gaseous uranium
hexafluoride by the direct fluorination of solid uranium tetrafluoride. The
desired uranium-235 is then separated as the hexafluoride by a gaseous diffusion
process. /Uranium-235/
General Manufacturing Information :
Uranium that has been processed to raise the concentration of uranium-235 is
referred to as enriched uranium. The extent of enrichment depends on the
intended end use of the uranium. Commercial light water reactors are designed
for use with the uranium-235 enriched to around 3%. Higher enrichment is
required for; high-temperature gas-cooled reactors, naval nuclear propulsion
reactors, most research reactors and weapons. The uranium-235 enrichment process
also increases the concentration of uranium-234. The higher activity of enriched
uranium is due more to increased uranium-234 than to increased uranium-235.
/Enriched uranium/
General Manufacturing Information :
The official definition of depleted uranium (DU) given by the US Nuclear
Regulatory Commission (NRC) is uranium in which the percentage fraction by
weight of uranium-235 is less than 0.711%. Typically, the percentage
concentration by weight of the uranium isotopes in DU used for military purposes
is: uranium-238: 99.8%; uranium-235: 0.2%; and uranium-234: 0.001%. /Depleted
uranium/
General Manufacturing Information :
The isotope most dangerous from the point of view of radiation, uranium-235,
comprises less than 1% of natural uranium, but is enriched during the production
of nuclear fuels. Higher fractions of uranium-235 increase the irradiation risk.
/Uranium-235/
Major Uses :
Uranium-234 /is used in/ nuclear research, with potential use in fission
detectors for counting fast neutrons. /Uranium-234/
Major Uses :
Early in the twentieth century, the only use of uranium was in the production of
a brown-yellow tinted glass and glazes; it was a byproduct of the extraction of
radium, which was used for medicinal and research purposes. Since the
mid-twentieth century, the most important use of uranium is as a nuclear fuel,
directly in the form of uranium-233 and uranium-235, fissionable radionuclides,
and in the form of uranium-238 that can be converted to fissionable
plutonium-239 by thermal neutrons in breeder reactors.
Preventive Measures :
Shielding is probably the most widely used (and most effective) method of
reducing beta doses from uranium. Relatively lightweight, cheap, and flexible
shielding (e.g., plastic or rubber mats) has been used effectively. ...
Generally, the less dense shielding materials are used whenever possible to
eliminate bremsstrahlung as well as beta radiation fields. Protective clothing
commonly worn in the nuclear industry can also afford beta dose reduction. ...
Dose to the lens of the eye can be effectively reduced through the use of
ordinary glasses, safety glasses, or face shields. Such eye protection should be
required when workers are dealing with the high beta fields from concentrated
uranium decay products./Uranium and its progeny/
Disposal Methods :
Low-level waste disposal occurs at commercially operated low-level waste
disposal facilities that must be licensed by either the Nuclear Regulatory
Commission or Agreement States. ... There are three existing low-level waste
disposal facilities in the United States /Barnwell, SC, Richland, WA, Envirocare
in Utah/ that accept ... low-level waste. All are in Agreement States. .
/Radioactive materials/
Disposal Methods :
Disposal of ... wastes /containing uranium/ should follow guidelines set forth
by the Nuclear Regulatory Commission. /Uranium and compounds/
Antidote and Emergency Treatment :
On September 30, 1999, three workers were severely exposed to neutrons and gamma
rays in a criticality accident that occurred at a uranium conversion facility in
Tokai-mura, Ibaraki Prefecture, Japan. Radiochemical analyses of phosphorus-32
and calcium-45 induced by neutrons in bone matrix were carried out after the
deaths of two of the victims. It was found that more than several million
becquerels of both nuclides had been produced in their body skeletons. Results
showed non-homogeneous distributions of neutron fluence in the bodies, from
which it could be deduced how both workers were positioned relative to the
fission source during exposure, i.e., at the moment of the first nuclear
excursion. For the victim who died first, the activities in the central part of
his body were more than those of his extremities. Also, in the central part of
his body, the right side showed more activities than the left side. As for the
second man, the activities indicated rather uniform exposure to neutrons to the
whole body although the geometrical distribution of the activity varied enough
to assume his orientation. Such information on the geometrical distribution of
neutron-induced radioactivities in the skeleton can be used to reconstruct the
posturing of the victims, which is necessary to estimate their apparent absorbed
doses.
Human Toxicity Excerpts :
/OTHER TOXICITY INFORMATION/ /GENOTOXICITY/ Blood samples from 115 smokers
(23-52 years of age) working in a nuclear fuel manufacturing facility who had
been exposed to uranyl compounds over 1-25 years (mean lung dose, 90 mSv) were
analyzed for various types of chromosomal aberrations. ... A significant
increase in the frequency of chromosomal aberrations was found in the exposed
smokers when compared with the control smokers. Smokers in the control group had
a higher frequency of chromosomal aberrations than non-smokers, suggesting a
clastogenic effect of smoking. The chromosomal aberrations observed in the
exposed smokers were attributed to the cumulative effect of smoking and exposure
to uranyl compounds. /Uranyl compounds/
Human Toxicity Excerpts :
/OTHER TOXICITY INFORMATION/ There are two hazards connected with exposure to
uranium compounds: the renal damage caused by the chemical toxicity of soluble
uranium compound, and the injury caused by the ionizing radiation resulting from
the disintegration of uranium isotopes. Which of these two hazards will be
limiting factor for exposure to uranium compounds depends on the solubility of
the compound, its route of administration and its isotope composition. The
isotope most dangerous from the point of view of radiation, uranium-235
comprises <1% of natural uranium, but is enriched during the production of
nuclear fuels. Higher fractions of uranium-235 increase the irradiation risk. As
retention time in the body is the important factor for the radiological damage,
exposure to insoluble particles that are deposited and retained in lung for long
time constitues a radiological hazard. ...Chemical toxicity... will be the
limiting factor after exposure to soluble uranium compounds, when large
quantities of the element will pass through the kidney. /Uranium compounds/
Non-Human Toxicity Excerpts :
/GENOTOXICITY/ Depleted uranium (DU) is a radioactive heavy metal coming from
the nuclear industry and used in numerous military applications. Uranium
inhalation can lead to the development of fibrosis and neoplasia in the lungs.
As little is known concerning the molecular processes leading to these
pathological effects, some of the events in terms of genotoxicity and
inflammation were investigated in rats exposed to DU by inhalation. Our results
show that exposure to DU by inhalation resulted in DNA strand breaks in broncho-alveolar
lavage (BAL) cells and in increase of inflammatory cytokine expression and
production of hydroperoxides in lung tissue suggesting that the DNA damage was
in part a consequence of the inflammatory processes and oxidative stress. The
effects seemed to be linked to the doses, were independent of the solubility of
uranium compounds and correlating with the type of inhalation. Repeated
inhalations seemed to induce an effect of potentiation in BAL cells and also in
kidney cells. Comet assay in neutral conditions revealed that DNA damage in BAL
cells was composed partly by double strands breaks suggesting that radiation
could contribute to DU genotoxic effects in vivo. All these in vivo results
contribute to a better understanding of the pathological effect of DU
inhalation. /Depleted uranium/
Absorption, Distribution & Excretion :
Comprehensive studies on the radiotoxicological risk of an intermediate compound
UO4, which is not specified in ICRP Recommendations, were motivated by its
increased use in the nuclear fuel cycle and the lack of information such as
physico-chemical and biokinetic properties. The aim of this work was to give an
experimental basis for assessing the appropriate limits on intake for workers
exposed to UO4 and to provide guidance for the interpretation of personal
monitoring data. Particle size measurement of the UO4 dust indicated a geometric
diameter D of 0.5 um, which corresponds to an activity median aerodynamic
diameter (AMAD) of 1.1 um. In vitro experiments conducted in culture medium
showed that UO4 is a soluble compound with 66.2% dissolved in 1.9 d and 33.8% in
78 d. Results of dissolution obtained with macrophages showed a significant
decrease of 50% at 1 d in terms of solubility. Biokinetic data in the rat
obtained from two in vivo studies involving intratracheal instillation in rats
indicated half-times in the lung of 0.5 d (96.6%) and 27 d (3.4%) for an initial
lung deposit (ILD) of 195 ug, and 1.2 d (90.3%) and 38 d (9.7%) for an ILD of
7.6 ug. Absorption parameters to blood as defined in the ICRP Publication 66
human respiratory tract model were calculated with the specific software GIGAFIT
and led to the rapid fraction fr (0.800 to 0.873), the rapid rate sr (0.525 to
0.928/day), and the slow rate ss (1.57 x 10-2 to 2.42 x 10-3/day). Effective
dose coefficients by inhalation for this UO4 compound using the in vivo
experimental results were calculated to be between 0.52 and 0.70x10-6 Sv per Bq.
Comparison of these values with effective dose coefficients defined in ICRP
Publication 68 for workers showed that UO4 could be considered as a fast soluble
compound of Type F. /UO4/
Threshold Limit Values :
The Physical Agents TLV Committee accepts the occupational exposure guidance of
the International Commission on Radiological Protection (ICRP). Ionizing
radiation includes particulate radiation (e.g., alpha particles and beta
particles emitted from radioactive materials, and neutrons from nuclear reactors
and accelerators) and electromagnetic radiation (e.g., gamma rays emitted from
radioactive materials and X-rays from electron accelerators and X-ray machines)
with energy greater than 12.4 electron-volts (eV) ... The guiding principle of
radiation protection is to avoid all unnecessary exposures. ICRP has established
principles of radiological protection. There are (1) the justification of a work
practice: No work practice involving exposure to ionizing radiation should be
adopted unless it produces sufficient benefit to the exposed individuals or the
society to offset the detriment it causes. (2) The optimization of a
workpractice: All radiation exposures must be kept as low as reasonably
achievable (ALARA), economic and social factors being taken into account. (3)
The individual dose limits: The radiation dose from all relevant sources should
not exceed the /ICRP/ prescribed dose limits.
Special Reports :
The United States Transuranium and Uranium Registries (USTUR) is operated, for
the U. S. Department of Energy (DOE) Office and Health Studies, by Washington
State University (WSU) in Richland, Washington. The program began as the U.S.
Plutonium Registry in 1968 and, through the years, it has branched out to
include other heavy radioactive metals such as uranium, americium, and thorium.
The Registries are a unique research program studying the distribution,
dosimetry, and possible biological effects of those metals in the human body.
Samples of body organs are acquired post-mortem from volunteer donors who worked
with the radioactive metals and who, at some time during their work history, had
an established intake of those metals into their bodies. ... The USTUR maintains
the National Human Radiobiological Tissue Repository (NHRTR) at the Richland
location ... Donors to the USTUR typically have worked at government sites where
plutonium, americium, or uranium were processed and many worked there during the
development of nuclear weapons or during the cold-war years. ... During the past
30 years, the USTUR has received autopsy samples from about 360 donors. Of
these, 24 have been whole body donations, providing a unique opportunity for the
thorough investigation of the distribution of actinides in the human body.
Approximately 5,000 organ samples were collected and analyzed for isotopes of
uranium, plutonium, thorium, and americium resulting in more than 15,000
analytical results for various organs of the body.
Special Reports :
U.S. Nuclear Regulatory Commission; Regulatory Guide 8.34 - Monitoring Criteria
and Methods to Calculate Occupational Radiation Doses. 1992/ Available at http://www.nrc.gov/reading-rm/doc-collections/reg-guides/occupational-health/active/8-34/index.html
as of September 25, 2006
MORE ABOUT HEALTH EFFECTS
Toxicity
Summary:
Uranium occurs in granite, metamorphic rock, lignite, monazite sand, and
phosphate deposits at concentrations on the order of 0.5 to 5 ppm. All uranium
isotopes are radioactive. Uranium nitrate, sulfate, chloride, fluoride, and
acetate are either soluble in water or dissolved by dilute acids. Several uanium
oxides (e.g., uranium dioxide (UO2), uranyl oxide (UO3), uranium octoxide (U3O8)
have very low solubility in water. ... Uranium can exist in valences of +3, +4,
+5, or +6, but U+6 is the most stable, and it exists principally as the uranyl
cation (UO2)+2. The uranyl compounds (+6) are of most importance biologically
because the uranic compounds (+4) are usually oxidized to +6 during absorption
into the body. Natural uranium, by itself, will not sustain a nuclear
chain reaction; however, in the presence of a moderator or enrichment with less
stable nuclides such as uranium-235, it may do so (2). Daily intake of uranium
in food and water varies from approximately 1- 5 ug U/d daily in uncontaminated
regions to 13-18 ug/d or more in uranium mining areas. A 70 kg,
non-occupationally exposed 'Reference Man' living in Europe or in the United
States has an estimated total body uranium content of about 22 ug. Uranium is
absorbed from the intestine or by the lungs, enters the bloodstream, and is
rapidly deposited in the tissues, predominantly kidney and bone, or excreted in
the urine. Renal toxicity is a major adverse effect of uranium, but the metal
has toxic effects on the cardiovascular system, liver, muscle and nervous system
as well (1). Uranium accumulates in bone in a manner similar to that of radium;
therefore, its alpha particles would presumably be nearly as effective in the
production of osteogenic sarcomas. Sarcomas have been produced in mice after
exposures to high specific activity uranium-232 and uranium-233 (2). According
to the ACGIH, there is debate as to what acute concentration of uranium in the
kidney constitutes the NOAEL. Substantial damage has been found when the renal
uranium concentration exceeded 3 ug/g in rodents. Other studies indicate that 2
ug/g in the rat kidney causes transient proteinuria. Morrow and associates in
1982 calculated that 0.3 ug/g was a threshold concentration for acute renal
injury in the dog. This value has been challenged on the grounds that the
half-life value used by Morrow et al was too long. Renal toxicity in rats... has
been detected at 1 ug U/g wet weight after treatment with 5 ug U/day for 14
days. The basis of the uranium-induced renal toxicity is related to (UO2)+2
competition for Mg+2 and Ca+2 adenosine-5'triphosphate (ATP) binding sites and
subsequent disruption of active transport in the cells of the proximal tubule
and associated structures. Toxicity to the lungs may also be associated with
alpha radiation from inhalation of insoluble forms of uranium. Chronic
inhalation by monkeys, dogs, and rats of natural uranium as UO2 at 25 mg/cu m
resulted in pulmonary fibrosis and malignant pulmonary neoplasia; the latter
appeared to be a direct result of alpha radiation. A series of studies at a
uranium enrichment plant noted an
excess of lung cancer deaths among 18,869 white male workers and an excess of
death from central nervous system (CNS) cancer. Subsequent case-control studies
found a relationship between lung cancer and work exposure but failed to find
such a relationship with cancer of thee CNS. A more recent follow-up confirmed
the excess deaths from lung and CNS cancers in this cohort and found excess
deaths from renal cancer, lymphosarcomas and multiple myeloma. For lung cancer,
but not for the other cancers, a dose-response relationship was found, an
observation consistent with the lung cancers among dogs chronically exposed to
uranium. These data suggest that radiation is the limiting factor for enriched
or insoluble uranium (2). One effect of exposure to ionizing radiation is to
reduce regeneration of injured tissue, an observation that may account for the
finding that radiation enhances the toxicity of uranium for the kidneys of mice
and dogs (2). According to Taylor and Taylor, any possible direct risk of cancer
or other chemical- or radiation-induced health detriments from uranium deposited
in the human body is probably less than 0.005% in contrast to an expected
indirect risk of 0.2% to 3% through inhaling the radioactive inert gas radon,
which is produced by the decay of environmental uranium-238 (1).
Evidence for Carcinogenicity:
There is inadequate evidence in humans for the carcinogenicity of natural
uranium. There is limited evidence in experimental animals for the
carcinogenicity of natural uranium. There is inadequate evidence in experimental
animals for the carcinogenicity of uranium-233. /Uranium/
Internalized radionuclides that emit alpha-particles are carcinogenic to humans
(Group 1).
A1; Confirmed human carcinogen. /Uranium (natural), soluble and insoluble
compounds, as U/
Human Toxicity Excerpts:
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ At the highest doses in the domain of
10,000 rads (100 gray), the reaction is immediate. One example is that of an
individual who worked in a uranium-235 recovery plant
... He inadvertently poured a container held under his left arm, filled with a
solution of uranium-235-enriched uranium, into a barrel already containing a
similar solution. He apparently lost track of how much fissionable material the
barrel contained. The amount he added exceeded criticality. There was a blue
flash as the liquid exploded, and he was drenched with the radioactive fluid. He
immediately became disoriented. His coworkers did a partial decontamination. He
was taken by ambulance to a series of hospitals which refused admission. An
admitting hospital was finally located, and he was installed in an evacuated
emergency ward, placed on a rubber sheet and further decontaminated by sponging
with wet towels. During the night, his blood pressure dropped sufficiently to
warrant continuous intravenous vasopressor medication. The next morning, his
left arm and the left side of his face abruptly became severely edematous. In
spite of the vasopressor medication, he went into irreversible shock and died
that afternoon about 22 hr after exposure. This pattern is known as the central
nervous system/cardiovascular syndrome. /U-235 enriched uranium/
/CASE REPORTS/ /KIDNEY/ A small cohort of Gulf War veterans involved in friendly
fire incidents where DU shells (penetrators) were used is being followed
prospectively to assess the health effects from inhalation, wound contamination,
and systemic absorption of retained DU metal fragments. A group of 33 soldiers
was first evaluated in 1993/1994 ... They had elevated concentrations of urinary
uranium, and mean urine uranium excretion was significantly higher in soldiers
with retained metal fragments compared to those without fragments (4.47 vs. 0.03
ug/g creatinine). No evidence of a relationship between urine uranium and
abnormal renal function could be demonstrated. In a subsequent follow-up of the
same cohort, 29 of the original 33 were examined in 1997 and their results
compared to 38 non-DU exposed, but Gulf War deployed soldiers. The correlation
between 1994 and 1997 24-hr urinary uranium determinations was highly
significant (Rsq = 0.8623) and urine uranium was again correlated with the
presence of retained DU fragments. Exposed soldiers (with and without fragments)
had 24-hr urinary uranium results ranging from 0.01 to 30.74 ug/g creatinine,
whereas the nonexposed group's results ranged from 0.01 to 0.047 ug/g creatinine.
The persistence of elevated uranium excretion suggests ongoing mobilization from
a storage depot and results in chronic systemic exposure. Again, no renal
abnormalities were found but neurocognitive examinations demonstrated a
statistical relationship between urine uranium levels and lowered performance on
computerized tests assessing performance efficiency. Elevated urinary uranium
was also statistically related to a high prolactin level (> 1.6 ng/mL; p =
.04). Uranium was also detected in the semen of 5 of 17 exposed veterans, but in
none of 5 nonexposed veterans ... These findings ... document elevated urinary
uranium excretion and small, but measurable, biochemical effects on the
neuroendocrine and central nervous systems 7 yr after first exposure. /Depleted
uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ A criticality accident occurred on
September 30, 1999, at the uranium conversion plant
in Tokai-mura (Tokai-village), Ibaraki Prefecture, Japan. When the criticality
occurred, three workers saw a "blue-white glow," and a radiation
monitor alarm was sounded. They were severely exposed to neutron and gamma-ray
irradiation, and subsequently developed acute radiation syndrome (ARS). One
worker reported vomiting within minutes and loss of consciousness for 10 to 20
seconds. This worker also had diarrhea an hour after the exposure. The other
worker started to vomit almost an hour after the exposure. The three workers,
including their supervisor, who had no symptoms at the time, were brought to the
National Mito Hospital by ambulance. Because of the detection of gamma-rays from
their body surface by preliminary surveys and decreased numbers of lymphocytes
in peripheral blood, they were transferred to the National Institute of
Radiological Sciences (NIRS), which has been designated as a hospital
responsible for radiation emergencies. Dose estimations for the three workers
were performed by prodromal symptoms, serial changes of lymphocyte numbers,
chromosomal analysis, and sodium-24 activity. The results obtained from these
methods were fairly consistent. Most of the data, such as the dose rate of
radiation, its distribution, and the quality needed to evaluate the average
dose, were not available when the decision for hematopoitic stem cell
transplantation had to be made. Therefore, prodromal symptoms may be important
in making decisions for therapeutic strategies, such as stem-cell
transplantation in heavily exposed victims. /Enriched uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ The accident /in a reactor using ...
uranium rods moderated by heavy water/ exposed six individuals and resulted in
one fatality. The individuals were designated H, V, G, M, D, and B. The total
doses they received were 3.23, 4.36, 4.14, 4.26, 4.19, and 2.07 Gy,
respectively. Exposure was relatively uniform over the body. By day 10
postexposure all patients except Patient B had granulocyte levels between 800
and 1500/uL and by day 20 the values had fallen to 20 to 100. For Patient B with
a dose of 2.07 Gy (207 rad) the granulocyte level had decreased to 1000/uL by
day 20. /Enriched uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ The accident occurred in a gaseous
diffusion facility as a result of enriched uranium accumulation in oil in a
vacuum pump. When an operator turned on the pump, the criticality alarm sounded
and he saw a flash of light. Fission yield for two excursions was estimated to
be 1.2X10+15. the operator was sent to the hospital with an estimated dose of
about 2 Gy. He experienced mild radiation sickness. /Enriched uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ ... There was an accident in a
building that housed various operations concerning highly enriched uranium. The
accident occurred in a glove box in which there was an excess accumulation of
uranium during filtration of uranyl oxalate precipitate. The operator was
looking through the glove box window and saw a bulge in the vessel fabric and
there was a release of gas and precipitate. The yield was estimated to be about
1X10+17 fissions. The operator picked up the precipitate and put it back into
the filter vessel. Within seconds he became ill. Within 17 hours after the
accident the specific activity of sodium-24 in the operator's blood was 245 Bq/cu
cm. This correlated to an estimated dose of about 30 Gy. The operator died 12
days after the accident. There were five other workders in the room, and they
received dose upward of 3 Gy and all suffered from radiation sickness but
recovered. /Enriched uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ /Three workers were involved in an
accident occuring when enriched uranyl nitrate solution was being poured
manually from one vessel into other bottles/. There was an immediate blue flash
and fissile material was ejected about 5 m above the vessel. Yield was estimated
to be about 2 X 10+17 fissions. A fourth worker, who was 2.5 m away, was also
exposed. They were all decontaminated and transferred to a hospital. The
estimated exposures were 60 Gy for the three workers who lifted the tank and 6
Gy for the fourth worker. The three massively exposed workers died in 5 to 6
days. The fourth worker was exposed to a very heterogeneous gamma and neutron
radiation (20 Gy on the left side of the body and 3 Gy on the right) and
developed an acute radiation sickness and subsequently suffered a number of
health problems, including cataracts. She survived more than 25 years after
exposure. /Enriched uranyl nitrate/
/CASE REPORTS/ /KIDNEY/ Only a few studies on renal tubular dysfunction in
chronically exposed workers have been conducted. ...Increased tubular enzyme
catalase /was reported/ in the urine of 46 exposed chemical workers, but the
results were not controlled for differences in urinary concentration.
...Increased excretion of total amino-nitrogen and some individual amino acids
/was measured/ in 18 exposed workers. ...Low-level beta2-microglobulinuria and
aminoaciduria /was found/ in 39 uranium mill workers. /Uranium compounds/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ This accident occurred in a
copper-reflected 90% enriched uranium core assembly. The operator incorrectly
transcribed the thickness of the reflector to be used and dropped the upper
copper hemisphere onto the bottom assembly. When this happened, he saw a flash
of light. He then left the area and reported the accident to the engineer and
health physicist. The fission yield was estimated to be about 2X10+17 in one
burst and a total of 1X10+19 fissions. The experimenter received an unusually
high neutron/gamma ratio (about 15) with estimated doses of 45 Gy from neutrons
and 3.5 Gy from gamma rays. Doses to the hands were estimated to be 200 to 300
Gy. ... Edema on the hands and forearms, as well as pain, was severe and by 24
hours there was moist desquamation. Also at 24 hours postexposure the chest
radiograph indicated interstitial edema. At the end of the second day, there was
marked hypotension and oliguria ... . Because of the life-threatening nature of
the combined local and whole-body injuries, amputation of both arms at the
mid-humeral level was performed on the third day. After this, there was
continued hypotension ... . The patient died 66 hours postexposure. /Enriched
uranium/
/CASE REPORTS/ /ACUTE RADIATION SYNDROME/ The accident occurred in ... 1999
during preparation of ... enriched uranium oxide powder... . There was a blue
flash... ; Patient S recalls feeling pain in the neck, chest, arms, and hands
and had numbness in some fingers. Patients O an S left for a decontamination
shower ... . Patient O vomited several times with in 5 to 25 minures and lost
consciousness for about 2 to 3 minutes. During transport /to a regional
hospital/ Patient O vomited twice and had two episodes of diarrhea. Patient O
was hypotensive .... All three patients were transferred /5 hr after the
incident to a hospital specializing in radiological sciences/. Upon arrival,
Patient O had erythema of the arms, face, and trunk and complained of pain in
the jaw and abdomen. His blood pressure recovered /with treatment/. Diarrhea
continued for 4 days ... The dose was estimated /to be 16 to > 20 Gy/.
Patient S felt nausea within an hr and vomited several times in the ambulance.
Upon arrival at the hospital, his face was tender and swollen and there was
salivary inflammation. His dose was estimated /to be 6 to 10.4 Gy/. ... Patient
Y had slight nausea on the way to the hospital ... /and/ transient hypoxemia.
There was never any epilation. /The estimated dose was 1to 4.5 Gy./ He had mild
bone marrow depression that recovered and he was discharged on day 82
postexposure. Treatment ... during the first 3 days was directed at inhalation
of uranium, control of the gastrointestinal syndrome, electrolyte and fluid
balance, prevention of bone marrow failure by administration of G-CSF (200 to
500 ug/day), and control of vascular injury by administration of pentoxifylline
(900 mg/day orally). /Despite a peripheral bone marrow stem cell transplant from
a sister and other treatments, Patient O/died from multiple organ failure on day
83 postexposure. Patient S received a female fetal cord blood transplant /and
medications/ to prevent graft-vs.-host disease. ... He was also given rG-CSF (5
to 10 ug/kg) and erythropoietin (100 IU/kg) ... and thrombopoietin (5 ug/kg) ...
Radiation stomatitis appeared at day 10 postexposure and erythema and blistering
of the hands and feet began on day 21. Epilation also occurred ... . /Six to
seven months post-exposure he developed chronic, antibiotic-resistant pneumonia
and severe radiation fibrosis of the skin ... He developed renal failure and
died 211 days postexposure. /Enriched uranium oxide/
/CASE REPORTS/ /KIDNEY/ Delayed renal effects were observed after a male worker
at a uranium enrichment plant was
accidentally exposed to a high concentration of uranium tetrafluoride powder for
about 5 minutes in a closed room. While renal parameters were normal during an
initial 30-day observation period, the patient showed signs of nephrotoxicity
beginning at post-accident day 68 as indicated by significantly elevated levels
of urinary proteins, nonprotein nitrogen, amino acid nitrogen/creatinine, and
decreased phenolsulfonpthalein excretion rate. These abnormalities persisted
through day 1,065 but gradually returned to normal values. The authors used
uranium urinalysis data and a pharmacokinetic model to estimate a kidney dose of
2.6 ug uranium/g kidney on post-accident day 1. /Uranium tetrafluoride powder/
/EPIDEMIOLOGY STUDIES/ A retrospective cohort study was conducted among 6,781
white male employees who had worked at /an/ Oak Ridge ... nuclear
material fabrication plant for at
least 30 days during 1947-74; vital status was determined for 6477 workers, and
the cohort was followed-up until the end of 1979. Among 3,490 monitored workers,
the mean cumulative alpha-particle dose to the lung was 82 mSv (range, 0-3.1 Sv),
and the mean cumulative external whole-body penetrating dose from
gamma-radiation was 9.6 mSv (0-4.3 Sv). When compared with the rates for white
men in the USA, the mortality rates from all causes combined, cardiovascular
diseases and from most site-specific cancers were decreased. Increased rates of
cancers of the lung, brain and central nervous system were seen in comparison
with national and state rates. Dose-response trends were detected for death from
lung cancer with respect to cumulative exposure to alpha-particles and
gamma-radiation, the most pronounced trend being found for exposure to
gamma-radiation among workers who received > or = to 0.05 Sv of
alpha-particles. ... No dose-response trend in mortality from brain or central
nervous system cancer was found. /Enriched uranium/
/EPIDEMIOLOGY STUDIES/ ... a cohort of 18,869 white men ... had been employed
between 1943 and 1947 at a uranium conversion and enrichment plant
in Oak Ridge, Tennessee, USA, and /were/ followed-up until 1974. Workers in
certain departments (especially chemical workers) were exposed to high average
air concentrations of uranium dust (up to 500 ug/cu m of air in 1945). In
comparison with mortality rates for white men in the USA, the standard mortality
rationss for various causes in the entire cohort were generally < 1.00. After
correction for unascertained deaths and missing death certificates, the SMR for
lung cancer was 1.22 (95% CI, 1.10-1.36). Adequate data on smoking habits were
not available in this study. The SMRs for various causes, including lung cancer,
did not tend to be higher among 8,345 workers who were employed in areas where
uranium dust was present or among 4,008 of these 8,345 workers who were employed
for one year or longer at the plant.
... /Uranium dusts/
/EPIDEMIOLOGY STUDIES/ The association between exposure to uranium dust and
death from lung cancer was investigated among workers who had been employed for
at least 183 days in any of four /U.S./ uranium processing or fabrication plants
... . Among workers who had potentially been followed-up for at least 30 years,
787 deaths from lung cancer were identified from death certificates. One control
was matched to each case on race, sex and birth and hire dates within three
years. Health physicists estimated the annual doses to the lung from exposure
primarily to insoluble uranium compounds for each person ... . The odds ratios
for death from lung cancer for seven groupings of the cumulative internal dose
to the lung showed no increase in risk with increasing dose. There was a
suggestion of an effect of exposure for workers who had been hired at the age of
45 years or older. Further analyses with the cumulative external doses of
thorium, radium and radon did not reveal a clear association between exposure
and increased risk, nor did categorization of the workers by facility ... .
/Uranium dusts/
/EPIDEMIOLOGY STUDIES/ In a retrospective cohort study of mortality in 995 white
men who had been employed for more than 30 days at a uranium processing facility
in upstate New York between 1943 and 1949 ... increased standardized mortality
ratios (SMR) were observed for all causes of death (SMR, 1.18; 95% CI,
1.07-1.30, 429 deaths), laryngeal cancer (SMR, 4.47; 95% CI, 1.44-10.43; five
deaths), all circulatory disease (SMR, 1.18; 95% CI, 1.04-1.35, 227 cases),
arteriosclerotic heart disease (SMR, 1.19; 95% CI, 1.01-1.39, 159 cases), all
respiratory disease (SMR, 1.52; 95% CI, 1.04-2.14, 32 cases) and pneumonia (SMR,
2.17; 95% CI, 1.26-3.47, 17 cases). No association was found with length of
employment or work in the most hazardous areas of the plant.
The rate of death from lung cancer was not increased (SMR, 0.97; 95% CI,
0.60-1.48, 21 cases). The internal doses from uranium were given only for the
lung: 40% of the cohort received 10-100 mSv/year and 38% received >100 mSv/year;
the remainder of the cohort received <10 mSv/year, or the value was unknown.
/Radioactive uranium, NOS/
/EPIDEMIOLOGY STUDIES/ The relationship between exposure to low level ionizing
radiation and health among uranium processing workers was studied. The facility
was in operation between 1943 and 1949. Workers were exposed to chlorine,
hydrofluoric acid, lead sulfate, nickel, nitric acid and nitrogen oxides,
silicon dioxide, sulfuric acid, uranium dust, and uranium hexafluoride. The
study cohort consisted of 995 white male workers employed longer than 30 days.
Radiation hazards were assessed by measurement of radon-222 and airborne
uranium, surface contamination, analysis of urine, and film badge records.
Workers were allowed to work 2 hr per day when processing ores with a high
radon-222 content. The data for the last 24 mo of operation indicated the
highest cumulative dose for a worker was about 20 millisieverts (mSv). Long term
occupational exposure was evaluated in a subcohort that received 150 mSv/year or
more. Statistically significant increases in death from all causes were found.
The mortality pattern among 149 workers who were exposed for more than 1 yr to
radiation above 100 mSv/yr was the same as that for the entire study group. No
significant deviation from expected rates were observed for any specific cause
of death in this subcohort. Significantly increased mortality was seen in the
entire worker population for cancer of the larynx and for pneumonia. No healthy
worker effect was seen when standardized mortality ratios were analyzed for
selected causes of death using cutoff dates at the end of 1950, 1960, and 1970.
The length of employment in the most hazardous sites of the facility had no
effect on mortality outcome. /Low level ionizing radiation from uranium/
/EPIDEMIOLOGY STUDIES/ It is well known that uranium miners are at an increased
risk of lung cancer. Whether they also have an increased risk for other cancer
sites remains under discussion. The aim of this study was to examine the
leukemia risk among miners. ... An individually matched case-control study of
former uranium miners in East Germany was conducted with 377 cases and 980
controls. ... Using conditional logistic regression models, a dose-response
relationship between leukemia risk and radon progeny could not be confirmed.
Yet, a significantly elevated risk is seen in the category > or = 400 mSv
when combining gamma-radiation and long-lived radionuclides. /The authors
concluded that/ the results suggest that an elevated risk for leukemia is
restricted to employees with a very long occupational career in underground
uranium mining or uranium processing. Moreover, the study does not support the
hypothesis of an association between exposure to short-lived radon progeny and
leukemia risk. /Uranium mining/
/EPIDEMIOLOGY STUDIES/ In a population based retrospective cohort study /the
authors/ studied cancer risk in Danish soldiers deployed to the war in the
Balkans. In particular, leukemia, earlier linked to ammunition enforced with
depleted uranium (DU) in other deployed soldiers, was a concern. Military
personnel, 13,552 men and 460 women, without known cancer at first deployment to
the Balkans, January 1, 1992 to December 31, 2001 were followed through December
2002. ...96 cases of cancer, 84 among men (standardized incidence ratio (SIR)
0.9) and 12 among women (SIR 1.7) /were found/ . Only four male bone cancers
(SIR 6.0), with three during the first year of follow-up, exceeded expectations.
Earlier reports on increased risk of leukemia and testis cancer among deployed
military personnel to the Balkans are not corroborated by /this/ study.
/Depleted uranium/
/BIOMONITORING/ /GENOTOXICITY/One of the negative environmental impacts of the
last armed conflict in Bosnia and Herzegovina was the use of radioactive
ammunition containing depleted uranium. The United Nations Environment Programme
measurements detected higher radioactivity at several examined sites in Bosnia
and Herzegovina. One of those places is in the area of Hadzici, close to
Sarajevo. This research included an evaluation of genetic load in human
lymphocytes due to exposure to depleted uranium. The study included individuals
who were located in the area of Hadzici and who were directly exposed to
depleted uranium. The control blood samples were taken from individuals who
lived in West Herzegovina which is considered environmentally uncontaminated.
The results of the micronucleus cytochalasin-B test in peripheral blood
lymphocytes showed increased micronuclei frequencies in the exposed group.
/Depleted uranium/
/BIOMONITORING/ Medical surveillance of a group of U.S. Gulf War veterans who
were victims of depleted uranium (DU) "friendly fire" has been carried
out since the early 1990s. Findings to date reveal a persistent elevation of
urine uranium, more than 10 yr after exposure, in those veterans with retained
shrapnel fragments. The excretion is presumably from ongoing mobilization of DU
from fragments oxidizing in situ. Other clinical outcomes related to urine
uranium measures have revealed few abnormalities. Renal function is normal
despite the kidney's expected involvement as the "critical" target
organ of uranium toxicity. Subtle perturbations in some proximal tubular
parameters may suggest early although not clinically significant effects of
uranium exposure. A mixed picture of genotoxic outcomes is also observed,
including an association of hypoxanthine-guanine phosphoribosyl transferase (HPRT)
mutation frequency with high urine uranium levels. Findings observed in this
chronically exposed cohort offer guidance for predicting future health effects
in other potentially exposed populations and provide helpful data for hazard
communication for future deployed personnel. /Depleted uranium/
/BIOMONITORING/ Health effects stemming from depleted uranium (DU) exposure in a
cohort of Gulf War veterans who were in or on US Army vehicles hit by friendly
fire involving DU munitions are being carefully monitored through the Baltimore
Veterans Affairs (VA) DU Follow-Up Program initiated in 1993. DU exposure in
this cohort has been directly measured using inductively coupled plasma-mass
spectrometer (ICP-MS) isotopic analysis for DU in urine specimens. Soldiers with
embedded DU fragments continue to excrete elevated concentrations of U in their
urine, documenting ongoing systemic exposure to U released from their fragments.
Biennial surveillance visits provide a detailed health assessment that includes
basic clinical measures and surveillance for early changes in kidney function,
an expected target organ for U. Tests also include measurements of genotoxicity
and neuroendocrine, neurocognitive and reproductive function. With the exception
of the elevated urine U excretion, no clinically significant expected U-related
health effects have been identified to date. Subtle changes in renal function
and genotoxicity markers in veterans with urine U concentrations greater than
0.1 microg(-1) creatinine, however, indicate the need for continued surveillance
of these DU-exposed veterans. /Depleted uranium/
/OTHER TOXICITY INFORMATION/ /GENOTOXICITY/Cultured peripheral blood lymphocytes
from 116 smokers and 80 non-smokers who were occupationally exposed to uranyl
compounds were analyzed for sister chromatid exchange. ... A significant
increase in sister chromatid exchange frequency was observed among both smokers
and nonsmokers exposed to uranyl compounds when compared with their respective
controls. In controls, a significant increase in the frequency of sister
chromatid exchange was observed in smokers when compared with non-smokers. /Uranyl
compounds/
/OTHER TOXICITY INFORMATION/ /GENOTOXICITY/ Blood samples from 115 smokers
(23-52 years of age) working in a nuclear
fuel manufacturing facility who had been exposed to uranyl compounds over 1-25
years (mean lung dose, 90 mSv) were analyzed for various types of chromosomal
aberrations. ... A significant increase in the frequency of chromosomal
aberrations was found in the exposed smokers when compared with the control
smokers. Smokers in the control group had a higher frequency of chromosomal
aberrations than non-smokers, suggesting a clastogenic effect of smoking. The
chromosomal aberrations observed in the exposed smokers were attributed to the
cumulative effect of smoking and exposure to uranyl compounds. /Uranyl
compounds/
/OTHER TOXICITY INFORMATION/ Several studies have been conducted of uranium
millers and of individuals involved in other uranium processing operations. ...
These workers are not exposed to high concentrations of radon gas in air but may
be exposed to alpha and beta-particles from inhaled or ingested uranium dust.
Inhalation of insoluble uranium particles is the major pathway for exposure of
the lung. ... Some studies of workers in uranium processing plants
thus showed an elevated rate of mortality from lung cancer, but the finding was
not consistent in all studies. The doses to the lung were relatively low. The
rates of death from cancers at other sites were increased in some studies, but
the small number of cases and lack of consistency between the findings reduce
their significance. /Inhaled and ingested uranium dust/
/OTHER TOXICITY INFORMATION/ Inhalation of poorly solubilizable uranium
particles results in a radiologic risk to the lung. Other target organs for
radiation effects are tracheobronchial lymph nodes, bone, bone marrow, and
kidney. It has generally been estimated that the radiation risk does not exceed
the chemical nephrotoxicity for soluble uranium until the enrichment is 5% to 8%
uranium-235 by weight, but the relative risk between chemical and radiation
risks continues to be an open question. /Poorly soluble uranium particles/
/OTHER TOXICITY INFORMATION/ The potential of radiation exposure from depleted
uranium is small as it emits alpha particles that do not penetrate human skin.
However, taken internally as shrapnel, it irradiates tissues and carries the
risk of uranium nephrotoxicity. /Depleted uranium/
/OTHER TOXICITY INFORMATION/ Prolonged contact with the skin might cause
radiation damage to the skin. /Uranium and insol cmpd as uranium/
/OTHER TOXICITY INFORMATION/ Because DU is only weakly radioactive, very large
amounts of dust (on the order of grams) would have to be inhaled for the
additional risk of lung cancer to be detectable in an exposed group. Risks for
other radiation-induced cancers, including leukemia, are considered to be very
much lower than for lung cancer. Erythema (superficial inflammation of the skin)
or other effects on the skin are unlikely to occur even if DU is held against
the skin for long periods (weeks). /Depleted uranium/
/OTHER TOXICITY INFORMATION/ In those studies where a higher incidence of lung
cancer has been found in uranium miners, the cancer is probably due to radon and
its daughter products, not to uranium itself. In fact, there is no convincing
evidence that uranium is carcinogenic. /Uranium NOS/
/OTHER TOXICITY INFORMATION/ /BONE//Researchers/ estimate the risk of bone
sarcoma from chronic ingestion of natural uranium, assuming a linear dose
response function for radium-226 and proportionality of the energy deposited in
the skeleton by uranium isotopes with that of radium-226. For ingestion of
uranium in water or food, or both, at a constant avg rate of 5 picoCi/day (7.5
ug/day of natural uranium), /the researchers/ est that over a 7 yr lifetime the
risk of bone sarcoma induction is 1.5 bone sarcomas/million persons for
uranium-233, uranium-234, uranium-235, uranium-236, or uranium-238 if the dose
response is linear, and that in a million people in the USA the bone sarcomas
occurring naturally over a lifetime would number about 750. /Uranium isotopes/
/OTHER TOXICITY INFORMATION/ There are two hazards connected with exposure to
uranium compounds: the renal damage caused by the chemical toxicity of soluble
uranium compound, and the injury caused by the ionizing radiation resulting from
the disintegration of uranium isotopes. Which of these two hazards will be
limiting factor for exposure to uranium compounds depends on the solubility of
the compound, its route of administration and its isotope composition. The
isotope most dangerous from the point of view of radiation, uranium-235
comprises <1% of natural uranium, but is enriched during the production of nuclear
fuels. Higher fractions of uranium-235 increase the irradiation risk. As
retention time in the body is the important factor for the radiological damage,
exposure to insoluble particles that are deposited and retained in lung for long
time constitues a radiological hazard. ...Chemical toxicity... will be the
limiting factor after exposure to soluble uranium compounds, when large
quantities of the element will pass through the kidney. /Uranium compounds/
/OTHER TOXICITY INFORMATION/ Very little health-related research has been
undertaken specifically on depleted uranium. The major reason for this is the
extensive research undertaken on natural and enriched uranium, both of which
pose a greater radiological hazard and an identical toxicological chemical
hazard to depleted uranium. /Depleted uranium/
/OTHER TOXICITY INFORMATION/ A by-product of the uranium enrichment process,
depleted uranium (DU) contains approximately 40% of the radioactivity of natural
uranium yet retains all of its chemical properties. After its use in the 1991
Gulf War, public concern increased regarding its potential radiotoxicant
properties. ... Heavy-metal nephrotoxicity has not been noted in ... Gulf War
veteran cohort studies despite markedly elevated urinary uranium excretion.
/Depleted uranium/
/OTHER TOXICITY INFORMATION/ Uranium from the environment enters the human body
by ingestion with food and drink and by inhalation of respirable airborne
uranium-containing dust particles or aerosols. Daily intake of uranium in food
and water varies from approximately 1 to approximately 5 micrograms U/d daily in
uncontaminated regions to 13-18 micrograms/d or more in uranium mining areas. A
70 kg, non-occupationally exposed 'Reference Man' living in Europe or in the
United States has an estimated total body uranium content of about 22
micrograms. Uranium is absorbed from the intestine or by the lungs, enters the
bloodstream, and is rapidly deposited in the tissues, predominantly kidney and
bone, or excreted in the urine. In the bloodstream, uranium is associated with
red cells, and its clearance is relatively rapid. Renal toxicity is a major
adverse effect of uranium, but the metal has toxic effects on the cardiovascular
system, liver, muscle and nervous system as well. Any possible direct risk of
cancer or other chemical- or radiation-induced health detriments from uranium
deposited in the human body is probably less than 0.005% in contrast to an
expected indirect risk of 0.2% to 3% through inhaling the radioactive inert gas
radon, which is produced by the decay of environmental uranium-238 ... /Uranium
compounds/
/OTHER TOXICITY INFORMATION/ A chronic kidney burden of 3 mg-U/g-kidney has
historically been the basis for development of action levels for bioassay
monitoring of workers who are chronically exposed to uranium (Hursh and Spoor
1973). Studies by Morrow et al. (1982) with the highly transportable and toxic
form of uranium, UO2F2, indicated that steady-state kidney concentrations of 3
mg/g in dogs were sufficient to produce indications of uranium poisoning.
Although UO2F2 is not handled at Hanford, it is prudent for bioassay monitoring
purposes to assume a renal toxicity threshold of less than 3 mg/g of kidney.
Based on recent studies by a number of investigators, Rich et al. (1988)
suggested that the ?no effect? threshold for uranium in kidney is 1.1 mg/g.
Hanford adopted a ?no effect? threshold of 0.4 mg/g as a sustained kidney burden
value, based on one-third of the Rich value, rounded to one significant figure.
This sustained kidney burden approach is now replaced for Hanford applications
by a peak kidney concentration approach, using the 1.1 mg/g value for both
chronic and acute exposure scenarios. Additional publications have raised some
question as to the appropriate magnitude for an assumed ?no effects threshold
level? of article, Leggett (1989) noted that results and conclusions of studies
have varied widely and that ?apparent discrepancies may be due largely to
differences in 1) perceptions and/or definitions of toxicity, 2) sensitivity of
the measurements of kidney damage or dysfunction, 3) patterns of exposure (for
example, acute versus chronic), and 4) sensitivity to renal U in different
species.? Leggett concluded ?it may be prudent to lower this long-standing
guidance level [of 3 mgU/g] by roughly an order of magnitude until more is known
about subtle physiological effects of small quantities of U in the kidneys.?
Similar sentiment was expressed by SuLu and Zhao (1990) in recommending a
maximum safe uranium burden in the kidney of 0.26 mg/g, based on a 10-fold
safety factor below mild kidney impairment observed in one human case at 2.6 mgU/g.
Considering Leggett noted that the early researchers cited ranges of much less
than 5 mg/g, probably 2 to 3 mg/g? rather than absolute values, the question of
a 1.1 mg/g v