STRONTIUM,
RADIOACTIVE: Nuclear Power Plant Emissions
Effluent Concentrations :
Most of the radioactive strontium released to the environment occurred as a
result of atmospheric testing of nuclear weapons from 1945 to 1980. According to
the World Health Organization, the total amount of strontium-90 released to the
atmosphere from weapons testing was 1.6X10+7 Ci (6X10+17 Bq) from 1945-1980(1).
The accident at the Chernobyl nuclear power plant in April, 1986 also released
about 2.2X10+6 Ci (8.1X10+16 Bq) of strontium-89 and 2.2X10+5 Ci (8.1X10+15 Bq)
of strontium-90 into the atmosphere(2). On January 24, 1978, the Soviet
nuclear-powered satellite Cosmos 954 re-entered earth's atmosphere over the
Canadian Arctic, releasing an estimated 83 Ci of strontium-90(2). Between 1944
and 1972, about 64 Ci of strontium-90 and 700 Ci of strontium-89 was released
into the atmosphere at the DOE Hanford site in Washington state from the routine
operation of chemical plants used to separate plutonium from spent reactor
fuel(2). Radioactive strontium released in airborne and water effluents from the
normal operation of nuclear power plants is considered low in comparison to
releases from atmospheric weapons testing and the major releases following
accidents at nuclear power plants. Water effluents from 29 boiling water reactor
(BWR) and 45 pressurized water reactor (PWR) nuclear power plants in the United
States released a total of 0.2071 Ci, 0.1828 Ci, 4X10-5 Ci, and 0.0115 Ci of
strontium-89, strontium-90, strontium-91, and strontium-92, respectively in
1993(2). Airborne effluents were 5X10-4 Ci, 2X10-5 Ci, and 0.0027 Ci for
strontium-89, strontium-90, and strontium-91, respectively(2). The World Health
Organization estimated that approximately 54 Ci of strontium-90 were discharged
to the environment from all the nuclear power plants (241 total plants)
operating globally in 1980(1).
Environmental Fate/Exposure Summary :
Most of the radioactive strontium released to the environment occurred as a
result of atmospheric testing of nuclear weapons from 1945-1980. Nuclear weapon
testing injects radioactive material into the stratosphere, which results in
wide dispersal of radioactive strontium and other radionuclides. The World
Health Organization estimated the total amount of strontium-90 released to the
atmosphere from weapons testing was 1.6X10+7 Ci (6X10+17 Bq) during the period
of 1945-1980. The accident at the Chernobyl nuclear power plant in the Ukraine
(April 1986) also resulted in the release of about 2.2X10+6 Ci (8.1X10+16 Bq) of
strontium-89 and 2.2X10+5 Ci (8.1X10+15 Bq) of strontium-90 into the atmosphere.
Since the radioactive decay half-life of strontium-89 is relatively short (51
days), its global transport and the extent of human exposure is limited. The
half-life of strontium-90 is much longer (29 years) and some strontium-90
reached the upper atmosphere and was subsequently transported around the world.
Routine releases of radioactive strontium also occur from the operation and
maintenance of nuclear power plants, but these levels are insignificant when
compared to the levels released from the atmospheric testing of nuclear weapons
and the accident at the Chernobyl nuclear power plant. The environmental fate of
the radioactive forms of strontium is expected to be similar to those of the
stable (non-radioactive) form. When released to the atmosphere, radioactive
strontium exists in the particulate-phase and is removed by wet and dry
deposition. Strontium has moderate mobility in soils and sediments, and adsorbs
moderately to metal oxides and clays. Strontium bioconcentrates in aquatic
organisms and accumulates in bones of both aquatic and terrestrial animals. BCF
values for strontium-90 ranged from 48 to 3,400 in fish muscle, but were 2,400
to 63,000 in bones. Workers employed in the nuclear industry may be accidentally
exposed to strontium-89 and strontium-90 through oral, dermal, and inhalation
routes. Since atmospheric testing of nuclear weapons has been discontinued for
many years and Chernobyl-related fallout was low in the US, current exposure of
the general population of the US to radioactive strontium is expected to be low.
The primary route of exposure to radioactive strontium for the general
population is through ingestion of food, dairy products, and drinking water.
Strontium-90 is deposited directly onto plant and soil surfaces and may be
translocated to plants through foliar absorption and root uptake. Vegetation
consumed by animals such as cows, goats, reindeer, etc, may eventually transfer
strontium-90 to the human food chain through the ingestion of beef, milk, or
other dairy products. The average daily intake for strontium-90 in the US peaked
in 1968 at about 1.1 Bq/day and has slowly declined over the past 40 years to
less than 0.05 Bq/day. (SRC)
Artificial Pollution Sources :
The radioactive isotopes of strontium are formed during nuclear fission, in
commercial applications such as the generation of electricity at nuclear power
plants. The most abundant radioisotopes that are formed in this manner are
strontium-89 and strontium-90(1). The largest releases of strontium-89 and
strontium-90 have occurred as a result of atmospheric testing of nuclear
weapons, and the accident at the Chernobyl nuclear power plant(1).
Environmental Fate :
ATMOSPHERIC FATE: Strontium exists in the particulate phase in the atmosphere
and is removed from air by wet and dry deposition. The transport and
partitioning of particulate matter in the atmosphere is largely dependent upon
the physical properties of the matter such as size and density as well as the
meteorological conditions such as temperature, the microphysical structure of
the clouds, and rainfall rate. The particle size of most radionuclides released
to the atmosphere following the Chernobyl nuclear accident was in the range of
0.1?10 um(1). Particles <5 um in diameter usually have low deposition
velocities and are transported long distances before being removed from the
atmosphere. Strontium-90 had a larger particle size distribution than other
radionuclides such as cesium-137, and subsequently had greater deposition near
the source of the accident(1). Following the accident at the Chernobyl nuclear
power plant, the wet deposition velocity of strontium-90 measured at Tsukauba,
Japan from May 5 to May 30, 1986 ranged from 0.016 to 0.230 m/second, with the
largest values recorded during a period of heavy rainfall(1). The flux rate of
strontium-90 ranged from 0.038-0.62 Bq/sq m-day(1). The average total annual wet
deposition flux of strontium-90 in the United States was 0.2 Bq/sq m-year in
1990(2).
Disposal Methods :
Low-level radioactive waste (LLW) is a general term for a wide range of wastes.
Industries, hospitals, and medical, educational, or research institutions;
private or government laboratories; and nuclear fuel cycle facilities (e.g.,
nuclear power reactors and fuel fabrication plants) using radioactive materials
generate low-level wastes as part of their normal operations. These wastes are
generated in many physical and chemical forms and levels of contamination.
Sediment/Soil Concentrations :
SEDIMENT: The annual mean level of strontium-90 in sediment from a segment of
the Danube River, Hungary ranged from 47.3 to 192.9 pCi/kg for samples collected
from 1983 to 1988(1). The mean activity of strontium-90 in lucustrine and marine
sediments from Antarctica in 1989-1996 ranged from 4.59 to 20.5 pCi/kg and
<2.7 to 5.78 pCi/kg, respectively(2). Marine sediments in the vicinity of two
nuclear power stations in South Korea had strontium-90 activities 3.16 to 48.6
pCi/kg(2).
Prior History of Accidents :
The Chelyabinsk region of the southern Ural Mountains was one of the main
military production centers of the former USSR and included the Mayak nuclear
materials production complex in the closed city of Ozersk. Accidents, nuclear
waste disposal and day-to-day operation of the Mayak reactor and radiochemical
plant contaminated the nearby Techa River. The period of most releases of
radioactive material was 1949-56, with a peak in 1950-51. During the first years
of the releases, 39 settlements were located along the banks of the Techa River,
and the total population was about 28,000. Technical flaws and lack of expertise
in radioactive waste management led to contamination of vast areas, and the
population was not informed about the releases. The protective measures that
were implemented (evacuations, restrictions on the use of flood lands and river
water in agricultural production and for domestic purposes) proved to be
ineffective, since they were implemented too late. Approximately 7,500 people
were evacuated from villages near the River between 1953 and 1960. ... During
1949-56, 7.6x10+7 cubic meters of liquid wastes with a total radioactivity of
100 Pbq were released into the Techa-Isset-Tobol river system. ... Large
populations were exposed over long periods to external gamma radiation, due
largely to cesium-137 but also to other gamma-emitting radionuclides such as
zirconium-95, niobium-95 and ruthenium-106 present in the water and on the banks
of the Techa River. The internal radiation dose was from ingestion of
strontium-90 and cesium-137 over long periods....Systematic follow up of a
cohort of almost 30,000 individuals who received significant exposure from the
releases was begun in 1967. ... The preliminary results of follow-up from 1950
through 1989, which were analyzed in linear dose-response models for excess
relative risk, indicate an increased rate of mortality from leukemia and solid
tumors related to internal and external doses of ionizing radiation.
Soil Adsorption/Mobility :
The rate of strontium-90 adsorption as a function of aqueous sodium and
potassium ion concentrations was studied using aquifer sediments beneath waste
water ponds at the Idaho National Environmental and Engineering Laboratory (INEEL)(1).
Soil adsorption coefficients (Kd) in the range of 56 to 62 L/kg were measured
for initial aqueous sodium and potassium levels equal to or less than 300 mg/L
and 150 mg/L, respectively(1). A significant decrease in strontium-90 adsorption
was observed when dissolved levels of sodium and potassium increased. Kd values
decreased to 4.7 to 19 for sodium levels of 1,000 to 5,000 mg/L(1). These data
indicate that sodium and potassium compete with strontium for cation exchange
sites in the soil, and in areas with high salinity, the mobility of strontium
will be greater than in areas with low dissolved sodium and potassium levels.
Similar results have been observed for soils containing high levels of Mg+2 and
Ca+2 ions(2). A strontium-90 plume in glacial sediments was studied at the Chalk
River Nuclear Laboratory in Ottawa Canada(2). The plume migrated about 300
meters over the course of 30 years. The mobility of strontium-90 was greatest
following an accidental spill from a nearby nitrate processing plant that
accidentally released high levels of calcium and magnesium. The plume advanced
rapidly as the strontium-90 was outcompeted for cation adsorption sites by Mg+2
and Ca+2 ions, but slowed significantly as the levels of calcium and magnesium
declined(2).
General Manufacturing Information :
Strontium isotopes are some of the principal constituents of radioactive fallout
following detonation of nuclear weapons, and they are released in insignificant
amounts during normal operations of reactors and fuel reprocessing operations.
Their toxicity is higher, however, than that of other fission products, and
strontium-90 represent a particular hazard because of its long half-life,
energetic beta emission, tendency to contaminate food, especially milk, and high
retention in bone structure. /Strontium isotopes/
Major Uses :
The beta emission of strontium-90 and its progeny, yttrium-90, has found
applications in industry, medicine, and research. The radiation of yttrium-90 is
more penetrating than that of strontium. It is used with zinc sulfide in some
luminescent paints. Implants of strontium-90 provide radiation therapy for the
treatment of the pituitary gland and breast and nerve tissue. The radiation from
strontium has been used in thickness gauges, level measurements, automatic
control processes, diffusion studies of seawater, and a source of electrical
power. Because strontium-90 is one of the long-lived and most energetic beta
emitters, it might prove to be a good source of power in space vehicles, remote
weather stations, navigational buoys, and similar long-life, remote devices.
Both strontium-89 and strontium-90 have been used in physical chemistry
experiments and in biology as tags and tracers. /Strontium isotopes/
Major Uses :
Radioisotope thermoelectric generators (RTGs) use heat generated by decay of
radioactive isotopes to produce electric power. They have no moving parts and
can operate for decades without refuelling. They are used as a power supply
where frequent maintenance or refuelling is expensive or impractical. Most
terrestrial RTGs are fuelled with strontium-90. The largest known RTG was
fuelled with 25 PBq of strontium-90. An RTG typically contains about 2 PBq of
strontium. ... Strontium sources can have an oxide or titanate form.
/Strontium-90/
Plant Concentrations :
The average strontium-90 activity in lichens collected in the Arctic was
reported as 6.46 Bq/kg(1). Six species of plants collected in Bodenmais, Bavaria
in July, 1993 had strontium-90 levels as follows (leaves): Dryopteris
carthusiana, 82.2; Vaccinium myrtillus, 78.8; Athyrium filix femina, 68.7; Rubus
fruticosus, 43.2; Prenanthes purpurea, 29.0; Rubus idaeus, 24.9 Bq/kg dry
weight(2). The uptake of strontium-90 in 10 different vegetable crops grown in
contaminated soils was studied(3). The order of strontium-90 uptake in the
edible portions of the plants was Radish (root) > Snapbean (fruit) >
Cucumber (fruit) > Hot pepper (fruit) > Celery (stem) > Beet (root)
> Celery (leaf)> Sweet pepper (fruit) > Cauliflower (fruit) > Tomato
(fruit). The uptake of strontium-90 in soybeans, corn, alfalfa, and wheat was
studied in various soils, and the order of strontium-90 accumulation was
soybeans > corn, alfalfa > wheat(4). It was shown that the uptake and
accumulation of strontium-90 in contaminated soils can be significantly reduced
by liming the soil (increasing the pH), or growing crops in soils with high clay
contents(4).
Therapeutic Uses :
In contrast to the smaller amount of radioactivity utilized in diagnostic
nuclear medicine, larger amounts of radioactivity are intentionally chosen for
use in therapeutic nuclear medicine. Therapy in nuclear medicine involves oral,
intravenous, or intracavitary delivery of radionuclides in liquid form
(sometimes called "unsealed" radionuclides). The radionuclide is
chosen with the aim of ensuring that subsequent physiological redistribution
will concentrate the radioactivity in the target tissue and, at the same time,
reduce the radioactivity in surrounding normal tissues. Radionuclides suitable
for use in therapeutic nuclear medicine must either localize in their elemental
form (such as iodine uptake in the thyroid gland) or be bound to an appropriate
pharmaceutical or antibody. Radionuclides commonly used for therapeutic nuclear
medicine include: colloidal gold-198; iodine-131 as sodium iodine, meta-iodobenzylguanidine,
monoclonal antibodies; colloidal phosphorous-32; and Sr-89 chloride /from
table/. /Iodine-131, colloidal 32-P, strontium-89/
Other Chemical/Physical Properties :
Radioactive forms of strontium are continuously transformed to stable isotopes
by the natural process of radioactive decay. Strontium-90 has a radioactive
decay half-life of 29 years, while strontium-89 has a much shorter half-life (51
days). Strontium-90 decays by emission of a beta-particle with a maximum energy
of 0.546 MeV and the creation of a yttrium-90 isotope, which is also unstable.
Yttrium-90 decays by beta-particle and gamma ray emission to the stable
zirconium-90 isotope. Strontium-89 decays to yttrium-89 by emission of a
negative beta-particle with a maximum energy of 1.495 MeV.
Environmental Abiotic Degradation :
Radioactive forms of strontium are continuously transformed to stable isotopes
by the natural process of radioactive decay(1). Strontium-90 has a radioactive
decay half-life of 29 years, while strontium-89 has a much shorter half-life (51
days)(1). Strontium-90 decays by emission of a beta-particle with a maximum
energy of 0.546 MeV and the creation of a yttrium-90 isotope, which is also
unstable. Yttrium-90 decays by beta-particle and gamma ray emission to the
stable zirconium-90 isotope(1). Strontium-89 decays to yttrium-89 by emission of
a negative beta-particle with a maximum energy of 1.495 MeV(1).
Methods of Manufacturing :
Radioactive strontium, strontium-89 and strontium-90, does not occur in nature,
but is the direct result of anthropogenic activity. Strontium-89 and
strontium-90 are formed during nuclear reactor operations and during nuclear
explosions by the nuclear fission of uranium-235, uranium-238, or plutonium-239.
/Radioactive strontium/
Major Uses :
The radioactive isotope Strontium-89 (also known by the pharmaceutical brand
name Metastro) is used as a cancer therapeutic to alleviate bone pain.
Strontium-85 has been used in medical applications, such as radiologic imagining
of bones, in minor commercial applications, such as thermoelectric power
generation, as a beta-particle standard source, and in instruments that measure
thickness and density of materials. /Strontium-89 and 85/
Absorption, Distribution & Excretion :
Data on the short-term retention of strontium-85 in twenty-three human subjects
are presented. Following a single intravenous injection, body burdens were
measured in a total body counter facility at frequent intervals over periods
ranging up to several months. Eleven subjects were on metabolic balance regimens
in the hospital so that urines and stools were collected and assayed for
strontium-85 and Ca. This group includes examples of the extremes of skeletal
calcium metabolism including those with avid retention of Ca, normal or balanced
cases, and those with large daily loss of endogenous Ca. The amounts of
strontium-85 excreted soon after administration varied widely among individuals
and reflected the state of Ca metabolism for each person. Retention could be
expressed as a power function of time R = atb, with values of the slope b
ranging from -0.83 in cases of negative Ca balance to -0.12 in a case with large
positive balance. Normals ranged -0.27 to -0.29. Repetitive monitoring of knee
and tibia areas divulged no reliable correlation with total body retention. ...
/Strontium-85/
Environmental Bioconcentration :
Strontium has been shown to bioconcentrate and bioaccumulate in both terrestrial
and aquatic food chains(1). Maximum BCF values of 48 to 3,400 were reported for
fish muscle, while values in the range of 2,400 to 63,000 were reported for bone
in fish obtained from the Department of Energy Savannah River Site(1). Because
strontium and calcium are chemically similar, the concentration of calcium in
water can influence the bioaccumulation of strontium in biota. Organisms such as
fish bioaccumulate strontium with an inverse correlation to levels of calcium in
water. However, this correlation is not universal and does not apply to other
organisms such as algae and plants(1).
Probable Routes of Human Exposure :
Plants acquire strontium-90 through atmospheric deposition and uptake through
the roots. Root uptake from soil is the primary pathway. Cows, reindeer and
other animals consume vegetation containing strontium-90 and ultimately it may
be transferred to the human food chain via milk, beef, etc(1).
Other Chemical/Physical Properties :
DECAY PATHWAY: Strontium-90, half-life 28.79 years, decays via beta(-) emission
(100%, 546.0 keV maximum; 195.8 keV average energy) to yttrium-90, half-life
64.00 hours; decays via beta (-) emission (99.989%, 2280.1 keV maximum, 933.7
keV average energy) to zirconium-90, half-life stable.
Other Chemical/Physical Properties :
DECAY PATHWAY: Strontium-91, half-life 9.63 hrs, decays via beta(-) emission
(2707 keV) to yttrium-91, half-life 58.51 days. Yttrium-91 decays via beta(-)
emission (1544.8 keV) to zirconium-91, half-life stable
Other Chemical/Physical Properties :
DECAY PATHWAY: Strontium-92, half-life 2.71 hrs, decays via beta(-) emission
(1940 keV) to yttrium-92, half-life 3.54 hrs. Yttrium-92 decays via beta(-)
emission (3639 keV) to zirconium-92, half-life stable
Radiation Limits & Potential :
DECAY PATHWAY: Strontium-90, half-life 28.74 years, decays via beta(-) emission
(100%, 546.0 keV maximum; 195.8 keV average energy) to yttrium-90, half-life
64.10 hours; decays via beta (-) emission (99.989%, 2280.1 keV maximum, 933.7
keV average energy) to zirconium-90, half-life stable.
Radiation Limits & Potential :
DECAY PATHWAY: Strontium-91, half-life 9.63 hrs, decays via beta(-) emission
(2.699 MeV) to yttrium-91, half-life 58.51 days; decays via beta() emission
(1.544 MeV) to zirconium-91, half-life stable
Radiation Limits & Potential :
DECAY PATHWAY: Strontium-92, half-life 2.71 hrs, decays via beta(-) emission
(1.911 MeV) to yttrium-92, half-life 3.54 hrs; decays via beta(-) emission
(3.639 MeV) to zirconium-91, half-life stable
Analytic Laboratory Methods :
Strontium-90 is determined directly from its beta emission, before yttrium-90
grows in, by beta counting immediately (three to four hours) after it is
collected by precipitation. The chemical yield can be determined gravimetrically
by the addition of stable strontium, after the separation of calcium.
Alternatively, strontium-90 can be measured from the beta emission of yttrium-90
while it reaches secular equilibrium (two to three weeks). The yttrium-90 is
separated by solvent extraction and evaporated to dryness or by precipitation,
then beta counted. The chemical yield of the yttrium procedure can be determined
by adding stable yttrium and determining the yttrium gravimetrically.
General Manufacturing Information :
The only naturally occurring radioactive isotopes of strontium are the result of
spontaneous fission of uranium in rocks. Other nuclear reactions and fallout
from nuclear weapons test are additional sources of fission products.
Strontium-90 is a fission product of uranium-235, along with strontium-89, and
short-lived isotopes, strontium-91 to strontium-102. /Strontium-isotopes/
Ecotoxicity Excerpts :
/FIELD STUDIES/ Carcasses of jackrabbits and kangaroo rats (Dipodomys spp.) were
analyzed for strontium-90 after a fallout event from nuclear testing in Nevada.
One year after the contamination event, jackrabbits had about twice the
strontium-90 activity detected in rabbits collected another year later. It was
suggested that bioavailability of strontium-90 was highest within a year of a
nuclear test contamination event.
Atmospheric Concentrations :
Prior to the 1940's radioactive strontium was not present in the air at any
significant levels(1). Concentrations of strontium-90 peaked in 1963 at
approximately 1X10+7 Ci, coincident with the period of extensive nuclear weapons
testing(1). Since the signing of the Nuclear Test Ban Treaty of 1963,
atmospheric levels have steadily dropped. In 1975, the average concentration of
strontium-90 in the air over Southwestern Poland was 1.62 pCi/cu m(2).
Other Chemical/Physical Properties :
DECAY PATHWAY: Strontium-89, half-life 50.53 days, decays via beta(-) emission
(1495.1 keV) to yttrium-89, half-life stable
Other Chemical/Physical Properties :
Radioactive Half-life: Strontium-85: 64.95 days; Emission Types and Energies:
Electron capture energy (1.065 MeV)
Other Chemical/Physical Properties :
Radioactive Half-life: Strontium-89: 50.52 days; Emission Types and Energies:
Beta energy (1.497 MeV)
Other Chemical/Physical Properties :
Radioactive Half-life: Strontium-90: 29.1 yrs; Emission Types and Energies: Beta
energy (0.546 MeV)
Other Chemical/Physical Properties :
Radioactive Half-life: Strontium-91: 9.5 hours; Emission Types and Energies:
Beta energy (2.707 MeV)
Other Chemical/Physical Properties :
Radioactive Half-life: Strontium-92: 2.71 hours; Emission Types and Energies:
Beta energy (1.91 MeV)
Toxicity Summary :
The beta-particle emitters strontium-90, yttrium-90 and 32-P-phosphate ... are
bone-seeking radionuclides that attach to bone surfaces, from which they
irradiate the marrow, and the depth of penetration of the radiation often
exceeds that of similarly located alpha-particle emitters. Beta emissions from
strontium-90 have a limited ability to penetrate through tissue. For that
reason, radiostrontium must be internalized or placed in close contact with skin
before adverse health effects will occur. The "bone-seeking" behavior
of strontium is the basis for concern regarding oral or inhalation exposures to
the radioactive isotopes, particularly strontium-90, with its long half-life of
29 years and highly energetic 0.546 MeV beta particles, plus the 2.2 MeV beta
particles of its short-lived yttrium-90 decay product isotope. /Srontium-90,
yttrium-90 and 32-P-phosphate/
Medical Surveillance :
The standard method of bioassay for strontium is by analysis of urine excreta
samples. /For/ class D material, its rapid transport to the systemic compartment
makes urine sampling an accurate, reliable, and convenient means for bioassay
monitoring. In addition, the lack of any readily detectable gamma emissions
makes in vivo detection somewhat ineffective, although if sufficient strontium
is present, the bremsstrahlung can be detected by in vivo counting. Fecal
samples can also be analyzed; however, their collection is more difficult ...
Non-Human Toxicity Excerpts :
/LABORATORY ANIMALS: Acute Exposure/ /GASTROINTESTINAL SYSTEM/ Gastrointestinal
effects were observed in beagle dogs receiving single high doses (long-term
retained body burdens between 47 and 83 uCi/kg; 1.74 and 3.07 MBq/kg) of soluble
aerosols containing 90-SrCl2. Anorexia and, 2 days before death, bloody
diarrhea, developed in six dogs that died between 18 and 32 days after the
extreme radiation dose rate induced acute radiation syndrome. It is likely that
severe thrombopenia, one of the features of radiation-induced bone marrow
hypoplasia, contributed to hemorrhage in the gastrointestinal tract as elsewhere
in the body. In addition, some effects could have been due to inhaled 90-SrCl2
droplets being transported from the mucoid, ciliated nasopharyngeal and
tracheobronchial epithelia to the pharynx and then swallowed. The
gastrointestinal epithelium then would have been exposed directly to beta
emissions from radiostrontium for a day or two. Another report of the same study
described three exposed dogs that died at age >11 years with a malabsorption
syndrome. All of the dogs exhibited chronic diarrhea with anorexia, and at
necropsy, contained chronic degenerative and inflammatory lesions of the small
intestines. Their long-term retained burdens were 1.9 to 9.6 uCi/kg (70.3-355.2
kBq/kg) and the absorbed doses to the skeleton were calculated to be 530 to
5,600 rad (5.3-56 Gy). Although the authors could not firmly establish whether
the syndrome was a consequence of exposure or of age, the cumulative radiation
dose to the digestive tract was likely to have been very low and this argues
against strontium-90 as the cause. /Strontium-90 chloride/
Non-Human Toxicity Excerpts :
/OTHER TOXICITY INFORMATION/ /SKIN/ Experimental studies on pig and mouse skin
show that the effects produced are dependent on the range of the radiation
emission, the area of skin irradiated, the thickness of skin, and the degree of
skin penetration achieved by the radionuclide. For example, application of
sources of strontium-90, technicium-170 and promethium-147 (high-, medium- and
low-energy beta-particle emitters, respectively) to the skin of pigs (thick) or
mice (thin) in vivo resulted in a range of deterministic effects, varying from
slight breakdown of the most superficial layers of the epidermis, produced by
high doses from promethium-147, to extensive local damage and moist
desquamation, produced at about 28 Gy from large-area strontium-90 sources (22.5
mm in diameter). To produce the same effect with thulium, 80 Gy of
beta-radiation from this radionuclide were required. The thresholds for acute
tissue breakdown due to the larger-diameter sources of beta-radiation were 17 Gy
for 90-Sr/90-Y and 30 Gy for thulium-170. In contrast, the threshold for less
serious epidermal necrosis after irradiation by promethium-147 was 150 Gy. This
is important, since exposure of 50% or more of the total body surface led to
death of Chernobyl liquidators due to skin desquamation and subsequent infection
when the doses to the skin exceeded 30 Gy for penetrating beta radiation and
200-300 Gy for less energetic emitters. /Strontium-90, technicium-170,
promethium-147, and thulium-170/
Analytic Laboratory Methods :
Strontium-89 has a half-life of 50.5 d and is only present in fresh fission
material. If it is present with strontium-90, it can be determined by the
difference in activity of combined strontium-89 and strontium-90 (combined or
total strontium) and the activity of strontium-90. Total strontium is measured
by beta counting immediately after it is collected by precipitation, and
strontium-90 is measured by isolating yttrium-90 after ingrowth. Strontium-85
can be used as a tracer for determining the chemical yield of strontium-90
(determined by isolating yttrium-90), but its beta emission interferes with beta
counting of total strontium and must be accounted for in the final activity.
General Manufacturing Information :
Nearly all of the strontium-90 generated in the United States is present in
spent nuclear reactor fuel rods.
Disposal Methods :
Nuclear Regulatory Commission regulations separate low-level waste into three
classes: A, B, and C. The classification of the waste depends on the
concentration, half-life, and types of the various radionuclides it contains.
The NRC sets requirements for packaging and disposal of each class of waste.
Class A low-level waste contains radionuclides with the lowest concentrations
and the shortest half-lives. About 95 percent of all low-level waste is
categorized as Class A.
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.
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ More than 25,000 residents were exposed to external gamma
radiation as well as internally from fission products (primarily from
cesium-137, strontium-90, ruthinium-106, and zirconium-95) released into the
Techa river from the nearby Mayak plutonium production facility, predominately
in the early 1950s. Studies have been conducted of cancer mortality in residents
and their offspring, as well as pregnancy outcomes. Initial dose estimates were
based on average doses reconstructed for settlements. Efforts are ongoing to
estimate individual doses for members of this resident cohort. To date, there is
no evidence of a decrease in birth rate or fertility in the exposed population
and no increased incidence of spontaneous abortions or stillbirths. There is
some evidence of a statistically significant increase in total cancer mortality.
Current estimates of the excess absolute risk (EAR) of leukemia in this cohort
is 0.85 per 10,000 person-year Gy (95% confidence interval 0.2, 1.5), and for
solid tumors the relative risk estimate is 0.65 per Gy (95% confidence interval
-0.3, 1.0). Median dose estimates for soft tissue in this cohort are 7 mSv
(maximum 456 mSv), and for bone marrow are 253 mSv (maximum 2021 mSv). Estimates
of the relative risk for cancer of the esophagus, stomach and lung are similar
to those reported for atomic bomb survivors. There is no evidence of an increase
in cancer mortality in the offspring of exposed residents. There has also been
one study of persons living in the town of Ozyorsk exposed to fallout from the
nearby Mayak nuclear facility. An excess of thyroid cancer, 3-4 times expected
relative to rates for all of Russia, has been observed. The excess is somewhat
lower (1.5-2-fold higher) based on a comparison with Chelyabinsk Oblast rates.
No estimates of radiation dose were included in this study. /Cesium-137,
strontium-90, ruthinium-106, and zirconium-95 fission products/
Human Toxicity Excerpts :
/EPIDEMIOLOGY STUDIES/ Epidemiological studies have found little or no
association between oral exposure to radioactive strontium from fallout and
cancer effects in humans. In an epidemiological study using the Danish cancer
registry, no association was found between the incidence of thyroid cancer in
Denmark between 1943 and 1988 and the levels of skeletal incorporation of 90-Sr
from fallout. In another epidemiological study, data collected between 1959 and
1970 in a strontium-90 monitoring program in Glasgow, Scotland, were used to
identify three cohorts with respect to the hypothetical risk for leukemia and
non- Hodgkin's lymphoma, acute myeloid leukemia, all childhood cancers combined,
and bone tumors. The three cohorts were a high risk group born in 1963-1966
(exposed to high levels of fallout, i.e., strontium-90, at a young age), a
medium risk group born in 1959-1962 (exposed to high levels at an older age),
and a low risk group born after 1966. Cumulative incidences for all cancers,
leukemia and non-Hodgkin's lymphoma, and acute myeloid leukemia all showed a
secular (progressive, noncyclical) increasing trend for children born before
1982. However, the study found no evidence for increased risks of total cancers,
leukemia and Non-Hodgkin's lymphoma, or acute myeloid leukemia for cohorts born
during the period of highest fallout (radiostrontium) exposure. The few cases of
bone tumors showed a statistically nonsignificant increase for children born
during the 'high risk' period. In contrast, the Techa River population that was
exposed to contaminated water and food as a result of releases from a nuclear
weapons facility exhibited a significant increase in the incidence of leukemia.
/Strontium-90/
Non-Human Toxicity Excerpts :
/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ In response to concern
about the possible long-term biological effects of strontium-90 in fallout from
atmospheric nuclear weapons tests, a second lifespan study was conducted ... in
which beagle dogs were exposed to strontium-90 in utero and up to 540 days of
age. ... A total of 403 pure-bred beagle dogs (approximately equal numbers of
males and females) were divided into seven groups receiving logarithmically
spaced doses. The animals were derived from 125 dams fed strontium-90 from 40
days after breeding to 42 days after parturition when they weaned their pups.
The pups received strontium-90 in the same 90-Sr:calcium ratio as the dams daily
until they were 540 days of age. ... The median survival times at the four lower
doses ranged from 13.5 to 14.4 years, while that for the 162 pooled controls was
14.4 years, and those at the three higher doses were 2.2 to 12 years. ...
Primary sarcomas of bone were classified as osteosarcoma, chondrosarcoma,
fibrosarcoma, hemangiosarcoma and undifferentiated sarcoma. In all, 66 primary
bone sarcomas were found in 47 dogs, including four controls, multiple sarcomas
being found in one female control, four males at the highest dose and 10 females
at the two higher doses. All the bone sarcomas occurred at the four higher
doses, and 74% of these tumors were osteosarcomas; the remainder was made up of
other sarcoma types. The ratio of bone sarcomas of the appendicular skeleton to
those of the axial skeleton was 38:23. /Strontium-90/
Absorption, Distribution & Excretion :
Strontium-90 is now present in the skeletons of all living persons throughout
the world as a result of nuclear detonations. Since this isotope is nonuniformly
distributed within the adult skeleton, it is necessary to define this
distribution in order to more adequately estimate the resultant radiation hazard
as well as to evaluate and compare data from a variety of bones of different
individuals. The principal bones from many cadavers were analyzed. While some
skeletons were assayed very extensively, the bulk of the investigation centered
on rib, vertebrae and long bone shaft. In the case of adults, an aliquot of the
total body skeleton was also analyzed in each case. In adults the strontium-90
concentration per gram calcium in vertebrae, rib and long bone shaft is 1.8, 1.1
and 0.5 times skeletal average respectively. In newborns and young children, the
distribution is much more uniform although these data are more limited. These
findings together with the fact that stable strontium is uniformly distributed
throughout the adult skeleton show that the nonuniformity of strontium-90 is a
temporal function of changing diet. If radiation damage from strontium-90 is a
threshold phenomena, the distribution is of particular importance since the
highest local concentration areas will first exceed the threshold. If the damage
is nonthreshold in character, the distribution is still of some significance
since some areas (e.g. bone marrow) are presumably more susceptible to radiation
damage than other areas. /Strontium-90/
Environmental Water Concentrations :
DRINKING WATER: The EPA ERAMS program monitors ambient concentrations of
strontium-90 in drinking water at 78 sites in major population centers or near
selected nuclear facilities. The median activity of strontium-90 in drinking
water for 1995 was 0.1 picoCuries per liter (pCi/L)(1). Sites with the highest
levels of strontium-90, Detroit and Niagara Falls, recorded activities of 0.4
and 0.5 pCi/L, respectively(1). In a 1974 study, 0.09 pCi/L of strontium-90 was
measured in Los Angeles, California drinking water(1). In a survey that examined
169 wells used for public drinking water in California, 16 wells measured
recordable concentrations of strontium-90, with a range of 8 to 330 pCi/L(2).
Probable Routes of Human Exposure :
NIOSH (NOES Survey 1981-1983) has statistically estimated that 4,656 workers
(533 of these are female) are potentially exposed to strontium-90 in the US(1).
Workers employed in the nuclear industry may be exposed to strontium-89 and
strontium-90 through oral, dermal, and inhalation routes(2). The radioactive
half-life of strontium-89 is short in comparison to strontium-90; therefore, the
potential exposure to workers and the general population is considerably lower
for strontium-89 as compared to strontium-90. A case of accidental inhalation
and dermal exposure to strontium-90 was reported for two workers handling waste
containers holding strontium-90 waste(3). The strontium-90 intake for one of the
workers was estimated as 2.6X10+5 Bq and was 6.6X10+4 Bq for the second
employee(3).
Probable Routes of Human Exposure :
Current exposure of the general US population to strontium-89 and strontium-90
is expected to be low since atmospheric testing of nuclear weapons has been
discontinued for several years and Chernobyl-related fallout was low in the
United States(1). The primary route of exposure is through oral ingestion of
foods and water containing radioactive strontium and possibly inhalation of
aerosols(1).
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.
Other Occupational Permissible Levels :
The recommendations in the American National Standards Institute standard, ANSI
Z88.2-1992, "American National Standard For Respiratory Protection,"
are endorsed by the U.S. Nuclear Regulatory Commission and may be used by
licensees in establishing a respiratory protection program with the
/several/exceptions /including limitations that do not permit or greatly
restrict the use of quarter-facepiece respirators and supplied air respirators
and self-contained breathing apparatus (SCBA) that operate in the demand mode./
Toxicity Summary:
The beta-particle emitters strontium-90, yttrium-90 and 32-P-phosphate ... are
bone-seeking radionuclides that attach to bone surfaces, from which they
irradiate the marrow, and the depth of penetration of the radiation often
exceeds that of similarly located alpha-particle emitters. Beta emissions
from strontium-90 have a limited ability to penetrate through tissue. For that
reason, radiostrontium must be internalized or placed in close contact with skin
before adverse health effects will occur. The "bone-seeking" behavior
of strontium is the basis for concern regarding oral or inhalation exposures to
the radioactive isotopes, particularly strontium-90, with its long half-life of
29 years and highly energetic 0.546 MeV beta particles, plus the 2.2 MeV beta
particles of its short-lived yttrium-90 decay product isotope. /Srontium-90,
yttrium-90 and 32-P-phosphate/
Evidence for Carcinogenicity:
There is inadequate evidence in humans for the carcinogenicity of strontium-90.
/Strontium-90/
There is sufficient evidence in experimental animals for the carcinogenicity of
pure beta-particle emitters (hydrogen-3, phosphorus-32, strontium-90,
yttrium-90, yttrium-91 and promethium-147). /Tritium, phosphorus-32,
strontium-90, yttrium-91, promethium-147/
Human Toxicity Excerpts:
/EPIDEMIOLOGY STUDIES/ More than 25,000 residents were exposed to external gamma
radiation as well as internally from fission products (primarily from
cesium-137, strontium-90, ruthinium-106, and zirconium-95) released into the
Techa river from the nearby Mayak plutonium production facility, predominately
in the early 1950s. Studies have been conducted of cancer mortality in residents
and their offspring, as well as pregnancy outcomes. Initial dose estimates were
based on average doses reconstructed for settlements. Efforts are ongoing to
estimate individual doses for members of this resident cohort. To date, there is
no evidence of a decrease in birth rate or fertility in the exposed population
and no increased incidence of spontaneous abortions or stillbirths. There is
some evidence of a statistically significant increase in total cancer mortality.
Current estimates of the excess absolute risk (EAR) of leukemia in this cohort
is 0.85 per 10,000 person-year Gy (95% confidence interval 0.2, 1.5), and for
solid tumors the relative risk estimate is 0.65 per Gy (95% confidence interval
-0.3, 1.0). Median dose estimates for soft tissue in this cohort are 7 mSv
(maximum 456 mSv), and for bone marrow are 253 mSv (maximum 2021 mSv). Estimates
of the relative risk for cancer of the esophagus, stomach and lung are similar
to those reported for atomic bomb survivors. There is no evidence of an increase
in cancer mortality in the offspring of exposed residents. There has also been
one study of persons living in the town of Ozyorsk exposed to fallout from the
nearby Mayak nuclear facility. An excess of thyroid
cancer, 3-4 times expected relative to rates for all of Russia, has been
observed. The excess is somewhat lower (1.5-2-fold higher) based on a comparison
with Chelyabinsk Oblast rates. No estimates of radiation dose were included in
this study. /Cesium-137, strontium-90, ruthinium-106, and zirconium-95 fission
products/
/EPIDEMIOLOGY STUDIES/ Perinatal mortality rates in the regions of Ukraine and
Belarus surrounding the Chernobyl site increased in 1987, the year following the
Chernobyl accident. The same year, increases of perinatal mortality were also
observed in Germany and Poland, and the effect can be associated with the cesium
burden in pregnant women. After 1989, there is an unexpected second rise of
perinatal mortality in Belarus and Ukraine. This increase is shown to correlate
with the strontium content in pregnant women. The findings parallel an increase
of perinatal mortality in Germany following the atmospheric bomb tests in the
1950's and 1960's. While the effect from cesium is essentially limited to 1987,
the effect from strontium persists until the end of the study period in 1998.
The cumulative effect from strontium around Chernobyl outweighs the effect from
cesium by at least a factor of 10. This is contrary to the assertion that the
cesium content in the Chernobyl fallout was more than 10-times greater than the
strontium content. Thus, the dose factor presently used seems to severely
underestimate the effect of strontium on perinatal mortality. /Cesium and
strontium fallout/
/EPIDEMIOLOGY STUDIES/ In the Techa River population that was exposed to
radiostrontium and radiocesium in drinking water and food between 1949 and 1956,
an increase in the number of deaths from leukemia and solid cancers was
reported. In the exposed group, the standardized mortality rate was 140 (95% CI:
131-150) per 100,000 compared to 105 (95% CI: 101-109) per 100,000 in the
control group during the followup period (1950-1982). Absorbed doses to the red
bone marrow in the study group were between 17.6 and 164 rad (0.176 and 1.64 Gy).
No increase in cancer mortality was observed among offspring of exposed
individuals. /Radiostrontium and radiocesium/
/EPIDEMIOLOGY STUDIES/ Epidemiological studies have found little or no
association between oral exposure to radioactive strontium from fallout and
cancer effects in humans. In an epidemiological study using the Danish cancer
registry, no association was found between the incidence of thyroid cancer in
Denmark between 1943 and 1988 and the levels of skeletal incorporation of 90-Sr
from fallout. In another epidemiological study, data collected between 1959 and
1970 in a strontium-90 monitoring program in Glasgow, Scotland, were used to
identify three cohorts with respect to the hypothetical risk for leukemia and
non- Hodgkin's lymphoma, acute myeloid leukemia, all childhood cancers combined,
and bone tumors. The three cohorts were a high risk group born in 1963-1966
(exposed to high levels of fallout, i.e., strontium-90, at a young age), a
medium risk group born in 1959-1962 (exposed to high levels at an older age),
and a low risk group born after 1966. Cumulative incidences for all cancers,
leukemia and non-Hodgkin's lymphoma, and acute myeloid leukemia all showed a
secular (progressive, noncyclical) increasing trend for children born before
1982. However, the study found no evidence for increased risks of total cancers,
leukemia and Non-Hodgkin's lymphoma, or acute myeloid leukemia for cohorts born
during the period of highest fallout (radiostrontium) exposure. The few cases of
bone tumors showed a statistically nonsignificant increase for children born
during the 'high risk' period. In contrast, the Techa River population that was
exposed to contaminated water and food as a result of releases from a nuclear
weapons facility exhibited a significant increase in the incidence of leukemia.
/Strontium-90/
/BIOMONITORING/ The results of a follow up of a group of fifty-two persons
carrying body burdens of strontium-90 and radium-226 for a period of about 2500
days are given. The body burdens vary in the group from less than 10 per cent of
the maximum permissible to somewhat more than 100 per cent of the maximum
permissible burden. ... The large fluctuation in the strontium-90 excretion
observed from day to day and at different times of the day could be greatly
diminished by relating it to calcium excretion. No significant clinical changes
could be observed in the exposed group except the signs of radiation dermatitis
in some cases. A small but statistically significant increase in the number of
red cells, hemoglobin and hematocrit values could be detected, when comparing
the whole group to a group of healthy prospective blood donors. There was,
however, no significant difference in these indicators when comparing persons
with different levels of body burdens within the group. Karyological
investigation of bone marrow cells showed a statistically significant increase
in the occurrence of aneuploid cells as compared to healthy controls.
Differences in the occurrence of aneuploid cells found in groups with different
levels of body burden are at this stage of the study not statistically
significant. A significant increase in the rate of chromosomal aberrations could
be demonstrated in cases with cumulative body burdens higher than 10 per cent of
the maximum permissible. A single cell with a haploid set of chromosomes was
found in a female patient with the highest body burden. An increased rate of
nonagglutinable red cells was a frequent but not regular finding in the exposed
group and no relation to the size of the body burden could be established.
/Strontium-90 and radium-226/
/OTHER TOXICITY INFORMATION/ For most internal dosimetry purposes, strontium-90
and yttrium-90 are the nuclides of concern. These nuclides are found in
equilibrium in virtually all circumstances under which exposure is likely.
Although strontium separation operations have been performed in which pure
strontium-90 might be obtained, the rapid ingrowth of the yttrium-90 decay
product results in the secular equilibrium condition being achieved within about
2 weeks after separation. Thus, even if an exposure to pure strontium-90
occurred involving significant metabolic uptake and internal deposition, within
about 2 weeks of exposure equal quantities of both nuclides would be present in
the body. /Strontium-90 and Yttrium-90/
/OTHER TOXICITY INFORMATION/ /BONE/ The hazard of strontium-90 is primarily that
of internal contamination. In the body, it is deposited mainly in the bones and
due to its long biological half-life, it may result in beta-ray induced
hemopoietic tissue lesions and malignant bone growth. /Strontium-90/
/OTHER TOXICITY INFORMATION/ /HEMATOPOIETIC SYSTEM/ The Techa River population
exposed to chronic combined external gamma radiation and internal radiation due
to strontium-90 and cesium-137 exhibited alterations in hematological
parameters, including leukopenia, thrombocytopenia, and granulocytopenia. These
effects were observed in a portion of the exposed population that received
radiation doses to the bone marrow at rates in excess of 30-50 rem (0.3-0.5 Sv)
per year. These ... exposures were to multiple sources of radiation.
/Strontium-90 and cesium-137/
/OTHER TOXICITY INFORMATION/ /GENOTOXICITY/ Radioactive strontium has been shown
to be genotoxic to human cells in vitro. In lymphocytes from freshly-drawn human
blood, doses of 0.2 to 5.0 Gy (0.002 to 0.05 rad) increased the frequency of
chromosomal aberrations. Acentric aberrations (acentrics and double minutes)
increased at > or = to 0.2 Gy (0.002 rad), dicentric aberrations increased at
> or = to 0.5 Gy (0.005 rad), and there was a slight indication that the
frequency of centric rings increased at > or = to 3.0 Gy (0.03). In the same
study, results of an electrophoretic assay (comet assay) on single exposed
lymphocytes revealed that DNA damage ... occurred at doses as low as 0.2 Gy
(0.002 rad)... . Dose-related increases in micronucleus formation, predominantly
derived from acentric chromosomes, were reported in human lymphocytes irradiated
at doses between 0.3 and 3.0 Gy (0.003 and 0.030 rad). /Radioactive strontium/
Probable Routes of Human Exposure:
NIOSH (NOES Survey 1981-1983) has statistically estimated that 4,656 workers
(533 of these are female) are potentially exposed to strontium-90 in the US(1).
Workers employed in the nuclear industry may be exposed
to strontium-89 and strontium-90 through oral, dermal, and inhalation routes(2).
The radioactive half-life of strontium-89 is short in comparison to
strontium-90; therefore, the potential exposure to workers and the general
population is considerably lower for strontium-89 as compared to strontium-90. A
case of accidental inhalation and dermal exposure to strontium-90 was reported
for two workers handling waste containers holding strontium-90 waste(3). The
strontium-90 intake for one of the workers was estimated as 2.6X10+5 Bq and was
6.6X10+4 Bq for the second employee(3).
Current exposure of the general US population to strontium-89 and strontium-90
is expected to be low since atmospheric testing of nuclear
weapons has been discontinued for several years and Chernobyl-related fallout
was low in the United States(1). The primary route of exposure is through oral
ingestion of foods and water containing radioactive strontium and possibly
inhalation of aerosols(1).
Plants acquire strontium-90 through atmospheric
deposition and uptake through the roots. Root uptake from soil is the primary
pathway. Cows, reindeer and other animals consume vegetation containing
strontium-90 and ultimately it may be transferred to the human food chain via
milk, beef, etc(1).
Body Burden:
The distributions of strontium-90 in the body are significantly different for
males and females(1). As expected, the highest concentrations of strontium-90
are measured in the boney tissue. Males averaged and females averaged 10.4 and
65 pCi/kg (0.38 and 2.4 Bq/kg) wet weight, respectively(1). Males had a much
higher concentration of strontium-90 in muscle tissue compared to females. The
heart and psoas muscles had respective concentrations of strontium-90 for men
averaging 13.9 and 18.7 pCi/kg (0.51 and 0.69 Bq) wet weight versus respective
concentrations of 7.4 and 1.9 pCi/kg (0.27 Bq/kg and 70 mBq/kg) wet weight for
females (1). The strontium-90 activities in teeth collected from the Ukraine
ranged from 0.027 to 0.44 pCi/g(1). A worker that was accidently exposed to
strontium-90 while handling waste containers had a strontium-90 urinary
excretion rate of approximately 544 Bq/day, one day post exposure(2). The
urinary excretion rate decreased exponentially and was <1 Bq/day 212 days
later(2).
Average Daily Intake:
The AVDI of strontium-90 in the US peaked in 1963 at approximately 1.1 Bq/day
and has steadily decreased(1). The current AVDI of strontium-90 in the US is
less than 0.05 Bq/day(1).
Toxicity Summary:
The beta-particle emitters strontium-90, yttrium-90 and 32-P-phosphate ... are
bone-seeking radionuclides that attach to bone surfaces, from which they
irradiate the marrow, and the depth of penetration of the radiation often
exceeds that of similarly located alpha-particle emitters. Beta emissions
from strontium-90 have a limited ability to penetrate through tissue. For that
reason, radiostrontium must be internalized or placed in close contact with skin
before adverse health effects will occur. The "bone-seeking" behavior
of strontium is the basis for concern regarding oral or inhalation exposures to
the radioactive isotopes, particularly strontium-90, with its long half-life of
29 years and highly energetic 0.546 MeV beta particles, plus the 2.2 MeV beta
particles of its short-lived yttrium-90 decay product isotope. /Srontium-90,
yttrium-90 and 32-P-phosphate/
Evidence for Carcinogenicity:
There is inadequate evidence in humans for the carcinogenicity of strontium-90.
/Strontium-90/
There is sufficient evidence in experimental animals for the carcinogenicity of
pure beta-particle emitters (hydrogen-3, phosphorus-32, strontium-90,
yttrium-90, yttrium-91 and promethium-147). /Tritium, phosphorus-32,
strontium-90, yttrium-91, promethium-147/
Probable Routes of Human Exposure:
NIOSH (NOES Survey 1981-1983) has statistically estimated that 4,656 workers
(533 of these are female) are potentially exposed to strontium-90 in the US(1).
Workers employed in the nuclear industry may be exposed
to strontium-89 and strontium-90 through oral, dermal, and inhalation routes(2).
The radioactive half-life of strontium-89 is short in comparison to
strontium-90; therefore, the potential exposure to workers and the general
population is considerably lower for strontium-89 as compared to strontium-90. A
case of accidental inhalation and dermal exposure to strontium-90 was reported
for two workers handling waste containers holding strontium-90 waste(3). The
strontium-90 intake for one of the workers was estimated as 2.6X10+5 Bq and was
6.6X10+4 Bq for the second employee(3).
Current exposure of the general US population to strontium-89 and strontium-90
is expected to be low since atmospheric testing of nuclear
weapons has been discontinued for several years and Chernobyl-related fallout
was low in the United States(1). The primary route of exposure is through oral
ingestion of foods and water containing radioactive strontium and possibly
inhalation of aerosols(1).
Plants acquire strontium-90 through atmospheric
deposition and uptake through the roots. Root uptake from soil is the primary
pathway. Cows, reindeer and other animals consume vegetation containing
strontium-90 and ultimately it may be transferred to the human food chain via
milk, beef, etc(1).
Body Burden:
The distributions of strontium-90 in the body are significantly different for
males and females(1). As expected, the highest concentrations of strontium-90
are measured in the boney tissue. Males averaged and females averaged 10.4 and
65 pCi/kg (0.38 and 2.4 Bq/kg) wet weight, respectively(1). Males had a much
higher concentration of strontium-90 in muscle tissue compared to females. The
heart and psoas muscles had respective concentrations of strontium-90 for men
averaging 13.9 and 18.7 pCi/kg (0.51 and 0.69 Bq) wet weight versus respective
concentrations of 7.4 and 1.9 pCi/kg (0.27 Bq/kg and 70 mBq/kg) wet weight for
females (1). The strontium-90 activities in teeth collected from the Ukraine
ranged from 0.027 to 0.44 pCi/g(1). A worker that was accidently exposed to
strontium-90 while handling waste containers had a strontium-90 urinary
excretion rate of approximately 544 Bq/day, one day post exposure(2). The
urinary excretion rate decreased exponentially and was <1 Bq/day 212 days
later(2).
Average Daily Intake:
The AVDI of strontium-90 in the US peaked in 1963 at approximately 1.1 Bq/day
and has steadily decreased(1). The current AVDI of strontium-90 in the US is
less than 0.05 Bq/day(1).