&EPA
United States
Environmental Protection
Agency
Common Radcnmdicks
Found at Superfund Sites
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Office of Radiation
and Indoor Air 9200.1-34
Office of Solid Waste and PB 2001 963303
Emergency Response EPA 540/R-00-004
Washington, DC 20460 March 2002
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INTRODUCTION
This booklet contains two page fact sheets on some of the common radionuclides found at hazardous
waste sites across the nation. It is meant to help you understand more about the various radionuclides and to
assist the public in understanding how the federal government may apply legal requirements in the
Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). The CERCLA
requirements and regulations described in this document contain legally binding requirements. The information
in this booklet is not a substitute for those requirements and regulations, nor is it a regulation itself. Thus, it
does not impose legally-binding requirements on any party, including EPA, States, or the regulated
community, and may not apply to a particular situation based on the circumstances. EPA and State
decisionmakers retain the discretion to adopt approaches on a case-by-case basis that differ from this booklet
where appropriate. Any decisions regarding a particular facility will be made based on the applicable statutes
and regulations. Therefore, interested parties are free to raise questions and objections about the
appropriateness of the application of this booklet to particular situation, and EPA will consider whether or not
the recommendations or interpretations in the booklet are appropriate in that situation. EPA may change this
booklet in the future.
This booklet answers such questions as: How can a person be exposed to the radionuclide?, How
can it affect human health?, How it enters and leaves the body?, What levels of exposure result in harmful
effects?, What recommendations has the federal government made to protect human health from the
radionuclide?
What recommendations has the Environmental Protection Agency made to protect human health?
Information on recommendations EPA has made to protect human health from exposure to a
particular radionuclide are contained in each of the fact sheets. General recommendations EPA has made to
protect human health, which cover all radionuclides, are summarized below.
All actions to clean up contamination at CERCLA sites must be protective of human health and the
environment and comply with Applicable or Relevant and Appropriate Requirements (ARARs) unless a
waiver is justified. ARARs are often the determining factor in establishing cleanup levels at CERCLA sites.
However, where ARARs are not available or are not sufficiently protective, EPA generally sets site-specific
cleanup levels for carcinogens at a level that represents an excess upper bound lifetime cancer risk of between
10"4 to 10"6 to an individual under a reasonable maximum exposure (RME) scenario. This can be interpreted
to mean that an individual may have a one in 10,000 to one in 1,000,000 increased chance of developing
cancer because of exposure to a site-related carcinogen. The site-specific level of cleanup is determined using
the nine criteria specified in 40 CFR 300.430(e)(9)(iii) of the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). EPA has developed a standard approach for calculating radionuclide soil
concentrations that correspond to a cancer risk level of 1 x 10"6 and that protect against radionuclides moving
from the soil into the groundwater. This electronic calculating tool may be found on the internet at
http://epa-prgs.ornl.gov/radionuclides .
The Environmental Protection Agency OSWER Directive 9200.4-18, "Establishment of Cleanup Levels for
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CERCLA Sites with Radioactive Contamination". Attachment A provides a listing of Federal radiation
regulations that may be ARARs for Superfund cleanup actions. This list is not a comprehensive list of Federal
radiation standards and it does not include State standards which may be ARARs. It must also be cautioned
that the selection of ARARs is site-specific and those determinations may differ from those listed in OSWER
Directive 9200.4-18, Attachment A. To assess the potential for cumulative noncarcinogenic effects posed by
multiple contaminants, EPA has developed a hazard index (HI). The HI is derived by adding the noncancer
risks for site chemicals with the same target organ/mechanism of toxicity. When the HI exceeds 1.0, there
may be concern for adverse health effects due to exposure to multiple chemicals.
What radionuclides are listed in this booklet?
The radionuclides listed in this booklet are:
Americium-241
Cesium-137
Cobalt-60
Iodine
Plutonium
Radium
Radon
Strontium-90
Technetium-99
Thorium
Tritium
Uranium
If you have more questions about the radionuclides mentioned in this booklet or would like more
information on the U.S. Environmental Protection Agency's Superfund hazardous waste cleanup program,
please contact either EPA 's Superfund Hotline at 1-800-424-9346 or 1-800-535-0202 or EPA 's
Superfund Radiation Webpage http://www.epa.gov/oerrpage/superfund/resources/radiation/index.htm.
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GLOSSARY
Activity: See radioactivity.
Aerobic: Able to live or grow only where oxygen is present.
Alpha particle: A positively charged particle released spontaneously form the nuclei of some radioactive
elements.
Applicable or Relevant and Appropriate Requirements (ARARs): Any state or federal statute that pertains
to protection of human health and the environment in addressing specific conditions or use of a particular
cleanup technology at a Superfund site.
Background Concentration: The concentration of a substance in an environmental media (air, water, or
soil) that occurs naturally or is not the result of activities from operations at the site.
Becquerel: The international system (SI) units of activity equal to one nuclear transformation (disintegration)
per second.
Beta Particle: An electron emitted from the nucleus during radioactive decay.
Curie: The customary unit of radioactivity. A curie is equal to 37 billion disintegrations per second which is
approximately the rate of decay of 1 gram of radium.
Decay products: Nuclides produced during radioactive decay of some other nuclide.
Detection limit: The lowest concentration of a chemical that can reliably be distinguished from a zero
concentration.
Epidemiology: Study of the distribution of disease, or other health-related states and events in human
populations, as related to age, sex, occupation, ethnicity, and economic status in order to identify and alleviate
health problems and promote better health.
Fission: Transformation characterized by the splitting of a nucleus into two or more parts and the release of a
relatively large amount of energy.
Fission product: Nuclides produced during nuclear fission.
Gamma radiation : Penetrating high-energy, short-wavelength electromagnetic radiation (similar to X-rays)
emitted during radioactive decay. Gamma rays are very penetrating and require dense materials, such as lead
or steal, for shielding.
Groundwater: The supply of fresh water found beneath the Earth's surface, usually in aquifers, which supply
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wells and springs. Because ground water is a major source of drinking water, there is growing concern over
contamination from leaching agricultural or industrial pollutants or leaking underground storage tanks.
Half-life: The time in which half the atoms of a particular radioactive substance disintegrate into another
nuclear form.
Ingestion: The act or process of putting food, water, or other material into the body for digestion.
Inhalation: To draw air, vapor, etc. into the lungs; to breathe.
Isotope: One of two or more atoms that has the same number of protons but different number of neutrons.
Maximum Contaminant Level (MCL): EPA evaluates the health risks associated with various contaminant
levels to ensure that public health is adequately protected. The MCL, as it is commonly known, is the
maximum allowable concentration of a specific contaminant in public drinking water. Superfund sites are
cleaned up so that the level of contamination in the groundwater does not exceed the MCL for that
radionuclide. The MCLs for radionuclides are currently being revised. For further information concerning the
MCLs for radionucludides, please refer to the following Internet address:
http://www.epa.gov/safewater/radionuc.html
Neutron particle : A particle that is similar in mass to a proton, but carries no charge and is found in the
nucleus of every atom heavier than hydrogen.
Nucleus: The small, central, positively charged region of an atom that carries essentially all the mass.
Nuclide: A general term referring to all known isotopes, both stable and unstable, of the chemical elements.
Picocurie (pd): one-trillionth of a curie. A curie is equal to 37 billion disintegrations per second which is
approximately the rate of decay of 1 gram of radium.
Radioactivity: The mean number of nuclear transformations occurring in a given quantity of radioactive
material per unit time. The customary unit is the Curie (Ci). The International System unit of radioactivity is
the Becquerel (Bq).
Radioactive decay: The spontaneous transformation of an unstable atom into one or more different nuclides
accompanied by either the emission of energy and/or particles from the nucleus, nuclear capture or ejection of
orbital electrons, or fission.
Radionuclide: An unstable nuclide that undergoes radioactive decay.
"Reasonable maximum exposure " (RME) : The maximum exposure reasonably expected to occur in a
population.
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Superfund Program: The program operated under the legislative authority of the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA) that provided broad Federal authority to respond
directly to releases or threatened releases of hazardous substances that may endanger public health or the
environment.
Toxic: A poisonous or hazardous substance; having poisonous or harmful qualities.
Working Level(WL): Any combination of short-lived radon decay products in one liter of air that will result in
the ultimate emission of alpha particles with a total energy of 130 billion electron volts.
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*•<
: EPA Facts About
• Americium-241
July 2002
What is americium-241?
Americium is a man-made radioactive metal that exists
as a solid under normal conditions. Americium is
produced when plutonium absorbs neutrons in nuclear
reactors and nuclear weapons tests.
Americium occurs in several forms called isotopes.
The most common isotope is americium-241.
What are the uses of americium-241?
Americium when blended with beryllium is used as a
neutron source in the testing of machinery and in
thickness gauges in the glass industry. Americium also is
used as a radiation source in medical diagnostic devices
and in research. It is commonly used in minute amounts
in smoke detectors as an ionization source.
How does americium-241 change in the
environment?
Americium-241 is formed in the environment by the decay
of plutonium contamination from nuclear weapons
production and testing. Americium-241 is an unstable
isotope. As americium decays, it releases radiation and
forms "daughter" elements. The first decay product of
americium-241 is neptunium-237, which also decays and
forms other daughter elements. The decay process
continues until stable bismuth is formed.
The radiation from the decay of americium-241 and its
daughters is in the form of alpha particles, beta particles,
and gamma rays. Alpha particles can travel only short
distances and generally will not penetrate the outer layer
of human skin. Gamma rays can penetrate the body. Beta
particles are generally absorbed in the skin and do not
pass through the entire body. The time in which half the
atoms of a radioactive substance disintegrate to another
nuclear form is known as the half-life. The half-life of
americium-241 is about 432 years.
How are people exposed to americium-241?
Americium has been released to the environment primarily
by atmospheric testing of nuclear weapons.
Concentrations of americium introduced into the
environment through nuclear weapons production
operations have been negligible compared with those
released during atmospheric testing of nuclear explosives.
Weapon sites and industries that manufacture smoke
detectors are potential sources of exposure from
americium-241. Potential pathways of exposure include
ingestion, inhalation, and the external pathway from
gamma radiation.
How does americium-241 get into the body?
Americium can enter the body when it is inhaled or
swallowed. When inhaled, the amount of americium that
remains in the lungs depends upon the particle size and
the chemical form of the americium compound. The
chemical forms that dissolve easily may be absorbed
through the lung and pass into the blood stream. The
forms that dissolve less easily are typically swallowed
where some may pass into the blood stream and the
remainder will pass through the feces. However, some
undissolved material may also remain in the lung.
Is there a medical test to determine exposure
to americium-241?
Tests are available that can reliably measure the amount
of americium in a urine sample, even at very low levels.
These measurements can be used to estimate the total
amount of americium present in the body. There are also
tests to measure americium in soft tissues (such as body
organs), feces, bones, and breast milk. Whole body
testing and nasal smears may also be used to measure
americium in the body. These tests are not routinely
available in a doctor's office because special laboratory
equipment is required.
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How can americium-241 affect people's
health?
Because americium emits alpha particles, americium poses
a significant risk if enough is swallowed or inhaled. Once
in the body, americium tends to concentrate primarily in
the skeleton, liver, and muscle. It generally stays in the
body for decades and continues to expose the
surrounding tissues to radiation. This may eventually
increase a person's chance of developing cancer, but
such cancer effects may not become apparent for several
years. Americium, however, also can pose a risk from
direct external exposure.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to americium-241. General
recommendations EPA has made to protect human health,
which cover all radionuclides including americium-241, are
summarized in the Introduction section of this booklet.
EPA has established a Maximum Contaminant Level
(MCL) of 15 picocuries per liter (pCi/1) for total alpha
particle activity, excluding radon and uranium, in drinking
water. Americium-241 would be covered under this MCL.
For more information about how EPA addresses americium-
241 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.gov/superfund/resources/radiation/
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*•<
: EPA Facts About
• Cesium-137
July 2002
What is cesium-137?
Radioactive cesium-137 is produced spontaneously
when other radioactive materials such as uranium and
plutonium absorb neutrons and undergo fission.
Cesium-137 is therefore a common radionuclide
produced when nuclear fission, or splitting, of uranium
and plutonium occurs in a reactor or atomic bomb.
What are the uses of cesium-137?
Cesium-137 and its decay product, barium-137m, are used
for sterilization activities for food products, including
wheat, spices, flour, and potatoes. Cesium-137 is also
used in a wide variety of industrial instruments such as
level and thickness gauges and moisture density gauges.
Cesium-137 is also commonly used in hospitals for
diagnosis and treatment, as a calibration source, and large
sources can be used to sterilize medical equipment.
How does cesium change in the environment?
Cesium-137 decays in the environment by emitting beta
particles. As noted above, cesium-137 decays to a short
lived decay product, barium-137m. The latter isotope
emits gamma radiation of moderate energy, which further
decays to a stable form of barium.
Cesium-137 is significant because of its prevalence,
relatively long half life (30 years), and its potential effects
on human health. Cesium-137 emits beta particles as it
decays to the barium isotope, Ba-137m (half life = 2.6
minutes).
How are people exposed to cesium-137?
People may be exposed externally to gamma radiation
emitted by cesium-137 decay products. If very high doses
are received, skin burns can result. Gamma photons
emitted from the barium decay product, Ba-137m, are a
form of ionizing radiation that can pass through the
human body, delivering doses to internal tissue and
organs. People may also be exposed internally if they
swallow or inhale cesium-137.
Large amounts of cesium-137 were produced during
atmospheric nuclear weapons tests conducted in the
1950s and 1960s. As a result of atmospheric testing and
radioactive fallout, this cesium was dispersed and
deposited world wide.
Sources of exposure from cesium-137 include fallout from
previous nuclear weapons testing, soils and waste
materials at radioactively contaminated sites, radioactive
waste associated with the operation of nuclear reactors,
spent fuel reprocessing plants, and nuclear accidents.
Cesium-137 is also a component of low level radioactive
waste at hospitals and research facilities.
How does cesium-137 get into the body?
Cesium-137 can enter the body when it is inhaled or
ingested. After radioactive cesium is ingested, it is
distributed fairly uniformly throughout the body's soft
tissues. Slightly higher concentrations are found in
muscle; slightly lower concentrations are found in bone
and fat. Cesium-137 remains in the body for a relatively
short time. It is eliminated more rapidly by infants and
children than by adults.
Is there a medical test to determine exposure
to cesium-137?
Generally, levels of cesium in the body are inferred from
measurements of urine samples using direct gamma
spectrometry (ICRP Publication 54, 1988). Because of the
presence of the gamma-emitting barium daughter product,
a technique called whole-body counting may also be
used; this test relies on detection of gamma photon
energy. Skin contamination can be measured directly
using a variety of portable instruments. Other techniques
that may be used include the taking of blood or fecal
samples, then measuring the level of cesium.
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How can cesium-137 affect people's health?
Based on experimentation with ionizing radiation and
human epidemiology, exposure to radiation from cesium-
137 can result in malignant tumors and shortening of life.
Great Britain's National Radiological Protection Board
(NRPB) predicts that there will be up to 1,000 additional
cancers over the next 70 years among the population of
Western Europe exposed to fallout from the accident at
Chernobyl.
For scenarios involving nuclear accidents or waste
materials the magnitude of the health risk would depend
on exposure conditions, such as types of radioactivity
encountered, nature of exposure, and time period.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to cesium-137. General
recommendations EPA has made to protect human health,
which cover all radionuclides including cesium-137, are
summarized in the Introduction section of this booklet.
EPA, has established a Maximum Contaminant Level
(MCL) of 4 millirem per year for beta particle and photon
radioactivity from man-made radionuclides in drinking
water. Cesium-137 would be covered under this MCL.
The average concentration of cesium-137 which is
assumed to yield 4 millirem per year is 200 picocuries per
liter (pCi/1). If other radionuclides which emit beta
particles and photon radioactivity are present in addition
to cesuim-137, the sum of the annual dose from all the
radionuclides shall not exceed 4 millirem/year.
For more information about how EPA addresses
cesium-137 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.sov/superfund/resources/radiation
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*•<
: EPA Facts About
• Cobalt-6O
July 2002
What is cobalt-60?
The most common radioactive form of cobalt is cobalt-60
which is produced commercially and used as a tracer and
radiotherapeutic agent. It is produced in a process called
activation, when materials in reactors, such as steel, are
exposed to neutron radiation.
What are the uses of cobalt-60?
Cobalt-60 is widely used as a medical and industrial radiation
source. Medical use consists primarily of cancer radiotherapy.
Industrial uses include testing of welds and castings, and a large
variety of measurement and test instruments including leveling
devices and thickness gauges. It is also used to sterilize
instruments, and to irradiate food to kill microbes and prevent
spoilage.
How does cobalt-60 change in the
environment?
Cobalt-60 decays by beta and gamma emission to non-
radioactive nickel.
Most of the radiation from the decay of cobalt-60 is in the form
of gamma emissions; some is in the form of beta particles. Beta
particles are generally absorbed in the skin and do not pass
through the entire body. Gamma radiation, however, can
penetrate the body.
The time in which half the atoms of a radioactive substance
disintegrate to another nuclear form is known as the half-life.
The half-life of cobalt-60 is about 5.2 years.
How are people exposed to cobalt-60?
Most exposure to cobalt-60 takes place intentionally during
medical tests and treatments. Such exposures are carefully
controlled to avoid adverse health impacts. Cobalt-60 is
produced as a result of weapons testing or in other nuclear
reactions. Since cobalt-60 has a short half-life there is no
significant presence of the isotope in the general environment at
this time. Exposures have occurred as the result of improper
disposal of medical radiation sources, and the accidental melting
of cobalt-60 sources by metal recycling facilities.
How does cobalt-60 get into the body?
The major concern posed by cobalt-60 is from external exposure
to gamma radiation. Cobalt-60 can be swallowed with food or
inhaled in dust. Once in the body, some of it is quickly
eliminated in the feces. The rest is absorbed into the blood and
tissues, mainly the liver, kidney, and bones. This cobalt leaves
the body slowly, mainly in the urine.
Is there a medical test to determine exposure
to cobalt-60?
Cobalt in the body can be detected in the urine. In addition, a
procedure known as whole-body counting can measure the
amount of gamma ray-emitting radioactive material in the body
such as the amount of cobalt-60 that has been inhaled and is still
in the lungs. Other techniques that may be used include the
taking of blood or fecal samples, then measuring the level of
cobalt-60. These tests are more sensitive and more accurate if
done shortly after exposure.
How can cobalt-60 affect people's health?
Because cobalt-60 releases gamma rays, it can affect the health
of people nearby even if they do not ingest or inhale it.
Exposure to low levels of gamma radiation over an extended
period of time can cause cancer. The magnitude of the risk of
adverse health effects is depends on the quantity of cobalt-60
involved and on exposure conditions, such as time of exposure,
distance from an the source (for external exposure), and whether
the cobalt-60 was ingested or inhaled.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited to
recommendations EPA has made to protect human health from
exposure to cobalt-60. General recommendations EPA has made
to protect human health, which cover all radionuclides including
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cobalt-60, are summarized in the Introduction section of this
booklet.
EPA has established a Maximum Contaminant Level (MCL) of
4 millirem per year for beta particle and photon radioactivity
from man-made radionuclides in drinking water. Cobalt-60
would be covered under this MCL. The average concentration
of cobalt-60 which is assumed to yield 4 millirem per year is
100 picocuries per liter (pCi/1). If other radionuclides which
emit beta particles and photon radioactivity are present in
addition to cobalt-60, the sum of the annual dose from all the
radionuclides shall not exceed 4 millirem/year.
For more information about how EPA addresses cobalt-
60 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.sov/superfund/resources/radiation
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EPA Facts About
Iodine
July 2002
What is Iodine?
Iodine is a metal found throughout the environment in
a stable form, iodine-127, and as unstable radioactive
isotopes of iodine. These radioactive forms include
iodine-129 and iodine-131. Iodine-129 is produced
naturally in the upper atmosphere. Iodine-129 and
iodine-131 are also produced in nuclear explosions. In
addition, iodine-129 is released at very low levels into
the environment from facilities that separate and
reprocess nuclear reactor fuels, and from waste
storage facilities.
What are the uses of iodine?
Stable iodine-127 is used as a dietary supplement for
thyroid deficiencies. In addition, iodine-131, iodine-125,
and iodine-123 are used for imaging and iodine-131 for
therapy for treatment of various thyroid conditions.
How does iodine change in the environment?
Iodine-129 and 131 are two of the more common
radioactive forms of iodine. Both iodine-129 and iodine-
131 release radiation during the decay process by emitting
a beta particle and gamma radiation. The half life of
iodine-131 is relatively short at eight days while the half
life of iodine-129 is much longer at over fifteen million
years
How are people exposed to iodine ?
People can be exposed to all forms of iodine through the
food chain. However, current environmental levels of
radioactive iodine are low. In addition fish, bread, milk,
and iodized salt contain stable iodine.
Large quantities of radioactive iodine-131 have been
released into the environment by nuclear weapons and
the Chernobyl accident; however, the current inventory
of iodine 131 in the environment is very low. The reason
for this is iodine-131 has a very short half life. Iodine- 129
is naturally occurring in the environment, and it has also
been produced by nuclear weapons testing. The amount
of iodine-129 produced by nuclear weapons testing is less
than the inventory of naturally occurring iodine-129.
Iodine-129, however, is found in radioactive wastes from
defense-related government facilities and nuclear fuel
cycle facilities.
How does iodine get into the body?
Iodine is soluble in water which allows it to move easily
from the atmosphere into living organisms. For this reason
iodine can be concentrated in marine organisms. Iodine
can also be concentrated in grass where it then can be
ingested by cows and incorporated into their milk. Iodine
can be found on leafy vegetables and then consumed
directly by humans. Once iodine is ingested into the
human body, a portion of it is concentrated in the thyroid
gland and the rest excreted. The most probable means of
exposure to radioactive iodine is from a patient who has
been recently administered radioactive iodine for imaging
or therapeutic purposes.
The uptake of radioactive iodine by the thyroid is
inversely related to the intake of stable iodine. For this
reason protection from radioactive iodine following an
emergency release is accomplished by ingesting large
doses of stable iodine. It should be noted that large doses
of stable iodine can be a health hazard and should not be
taken except in an emergency and when directed by the
appropriate emergency response officials.
Is there a medical test to determine exposure
to iodine?
Since iodine is concentrated in the thyroid gland,
radioassay of the thyroid is used to determine the
exposure level from iodine. Whole body counts which
measure iodine gamma radiation can also be used to
measure iodine in the body.
How can iodine affect people's health?
The predominant health concern for radioactive iodine is
in the thyroid gland where it may induce nodules or
thyroid cancer. High doses of iodine are used to treat
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thyroid cancer. Lower doses of radioactive iodine will
result in reducing activity of the thyroid gland which will
result in lower hormone production in the gland. There is
a fine balance when treating thyroid problems with
radioactive iodine. Such treatments are only performed
when the benefits outweigh the risks. As with any
radioactive material, there is an incremental chance that a
cancer or other adverse health effect can result from that
incremental exposure to radioactive materials.
What recommendations has the
Environmental Protection Agency made to
protect human health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to iodine-131. General
recommendations EPA has made to protect human health,
which cover all radionuclides including iodine-131, are
summarized in the Introduction section of this booklet.
EPA has established a Maximum Contaminant Level
(MCL) of 4 millirem per year for beta particle and photon
radioactivity from man-made radionuclides in drinking
water. The average concentration of iodine-131, which is
assumed to yield 4 millirem per year, is 3 picocuries per
liter (pCi/1). If other radionuclides which emit beta
particles and photon radioactivity are present in addition
to iodine- 131, the sum of the annual dose from all the
radionuclides shall not exceed 4 millirem/year.
For more information about how EPA addresses
iodine 131 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www. epa. sov/superfund/resources/radiation/
index.htm
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EPA Facts About
Plutonium
July 2002
What is plutonium?
Plutonium is a radioactive metal that exists as a solid
under normal conditions. It is produced when
uranium absorbs an atomic particle such as a neutron.
Small amounts of plutonium occur naturally, but large
amounts have been produced in nuclear reactors as a
result of neutron irradiation.
Plutonium occurs in several forms called isotopes.
The most common plutonium isotopes are plutonium-
238, plutonium-239 and plutonium-240.
What are the uses of plutonium?
Plutonium-238 is used as a heat source to generate
thermoelectric power for electronic systems in satellites
and for heart pacemakers. Plutonium-239 is used primarily
in nuclear weapons. Plutonium-239 and plutonium-240 are
two of the most prevalent plutonium byproducts of
weapons testing.
How does plutonium change in the
environment?
Plutonium is not a stable element. As plutonium decays,
it releases radiation and forms decay products . For
example, the decay products of plutonium-238 and
plutonium-239 are uranium-234 and uranium-235,
respectively. The decay process continues until a stable,
non-radioactive decay product is formed.
Radiation is released during the decay process in the form
of alpha and beta particles, and gamma radiation. Alpha
particles can travel only short distances and generally will
not penetrate human skin. Beta particles are generally
absorbed in the skin and do not pass through the entire
body. Gamma radiation, however, can penetrate the body.
Plutonium-238, plutonium-239, and plutonium-240 are
isotopes of plutonium, and have half-lives of 87 years,
24,065 years, and 6,537 years respectively.
How are people exposed to plutonium?
Plutonium has been released to the environment primarily
by atmospheric testing of nuclear weapons and by
accidents at facilities where plutonium is used. The
amount of plutonium introduced into the environment
through nuclear weapons production operations have
been negligible compared with those released during
testing of nuclear explosives.
Plutonium-238, plutonium-239, and plutonium-240 are
alpha emitters. As a result, the potential for direct
exposure is minimal from these isotopes. When mixed in
soil on the ground these plutonium isotopes have a
potential risk that is predominantly from the inhalation
and ingestion pathways.
How does plutonium get into the body?
Plutonium can enter the body when it is inhaled or
swallowed. Once inhaled, the amount of plutonium that
remains in the lungs depends upon the particle size and
the chemical form of the plutonium. The chemical forms
that dissolve less easily may be absorbed or may remain
in the lung. The forms that dissolve less easily are often
swallowed. Plutonium swallowed with food or water is
poorly absorbed from the stomach, so most of it leaves
the body in the feces.
Is there a medical test to determine exposure
to plutonium?
Tests are available that can reliably measure the amount
of plutonium in a urine sample, even at very low levels.
There are also tests to measure plutonium in soft tissues
(such as body organs), feces, and bones. These
measurements can be used to estimate the total amount of
plutonium present in the body. These tests are not
routinely available in a doctor's office because special
laboratory equipment is required. Other medical tests for
plutonium include whole body counting for americium-
24land nasal smears.
-------
How can plutonium affect people's health?
Plutonium may remain in the lungs or move into the
bones, liver, or other body organs. The plutonium that is
not readily extracted stays in the body for decades and
continues to expose the surrounding tissue to radiation.
Plutonium inhaled or ingested will increase a person's
chance of developing cancer, but such cancer effects may
not become apparent for several years.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to plutonium. General
recommendations EPA has made to protect human health,
which cover all radionuclides including plutonium, are
summarized in the Introduction section of this booklet.
EPA has established a Maximum Contaminant Level
(MCL) of 15 picocuries per liter (pCi/1) for alpha particle
activity, excluding radon and uranium, in drinking water.
Plutonium would be covered under this MCL.
For more information about how EPA addresses
plutonium at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.eov/superfund/resources/radiation
-------
: EPA Facts About
• Radium
July 2002
What is radium?
Radium is a naturally occurring radioactive metal that
exists as one of several isotopes. It is formed when
uranium and thorium decay in the environment. In the
natural environment, radium is found at low levels in
soil, water, rocks, coal, plants, and food.
What are the uses of Radium?
In the early 1900's, radium was erroneously used to treat
rheumatism and mental disorders, and as a general tonic.
Radium was also used to make luminous paints for watch
dials, clocks, glow in the dark buttons, and military
instruments. Because of the health hazards from these
types of exposures the use of radium for these purposes
was discontinued. Radium has also been widely used in
medical therapy to irradiate cancerous cells in the body,
but this use has largely been replaced by other
radioactive materials or methods. Radium-226 has also
been used in medical equipment, gauges, and calibrators,
and in lightening rods. Alpha emitters such as radium and
plutonium can be used as components of a neutron
generator.
How does radium change in the environment?
Radium is not a stable element. As radium decays, it
releases radiation and forms decay products. Like
radium, many of these decay products also release
radiation and form other elements. The decay process
continues until a stable, nonradioactive decay product is
formed.
Radiation is released during the decay process in the form
of alpha and beta particles, and gamma radiation. Alpha
particles can travel only short distances and cannot
penetrate human skin. Beta particles are generally
absorbed in the skin and do not pass through the entire
body. Gamma radiation, however, can penetrate the body.
Isotopes of radium decay to form radioactive isotopes of
radon gas. Radium-224, radium-226, and radium-228, the
most common isotopes of radium, have half-lives of 3.5
days, 1,600 years, and 6.7 years respectively, after which
each forms an isotope of radon. Radon is known to
accumulate in homes and buildings.
How are people exposed to radium?
Since radium is present at relatively low levels in the
natural environment, everyone has some level of exposure
from it. However, individuals may be exposed to higher
levels of radium and its associated external gamma
radiation if they live in an area where there is an elevated
level of radium in soil. In addition, radium is particularly
hazardous because it continually produces radon which
can diffuse into nearby homes.
An individual can be exposed to radium if one comes into
contact with waste from 20th century ore at radium
processing facilities, former radium dial facilities, or
radium dials. In addition, exposure from radium can occur
if radium is released into the air from the burning of coal
or other fuels, or if drinking water taken from a source
that is high in natural radium is used. Individuals may
also be exposed to higher levels of radium if they work in
a mine or in a plant that processes ores. Phosphate rocks
which can contain relatively high levels of uranium and
radium are also a potential source of exposure. The
concentration of radium in drinking water is generally low,
but there are specific geographic regions in the United
States where higher concentrations of radium may occur
due to geologic sources.
Radium exposure therefore can be from gamma radiation
from radium decay products, lung exposure from radon
gas and its decay products, and inhalation and ingestion
exposure.
How does radium get into the body?
Radium can enter the body when it is inhaled or
swallowed. Radium breathed into the lungs may remain
there for months; but it will gradually enter the blood
stream and be carried to all parts of the body, with a
portion accumulating in the bones.
-------
If radium is swallowed in water or with food, most of it
(about 80%) will promptly leave the body in the feces.
The other 20% will enter the blood stream and be carried
to all parts of the body. Some of this radium will then be
excreted in the feces and urine on a daily basis; however,
a portion will remain in the bones throughout the person's
lifetime.
Is there a medical test to determine exposure
to radium?
Urine and bone biopsy tests are sometimes used to
determine if individuals have ingested or swallowed a
source of radioactivity such as radium. Radon, a decay
product of radium, can also be measured in air that is
exhaled from the body. Another technique, gamma
spectroscopy, can measure the amount of radioactivity in
portions of the body. These tests require special
equipment and cannot be done in a doctor's office. There
is no test that can detect external exposure to radium's
gamma radiation alone.
How can radium affect people's health?
Exposure to radium over a long period may result in many
different harmful effects. If inhaled as dust, or ingested as
a contaminant, risk is increased for several diseases
including, lymphoma, bone cancer, and hematopoietic
(blood-formation) diseases, such as leukemia, and aplastic
anemia. These effects take years to develop. If exposed
externally to radium's gamma radiation, risk of cancer is
increased in essentially all tissues and organs, though to
varying degrees. However, in the environment, the
greatest risk associated with radium is actually posed by
it's direct decay product radon. Radon has been shown
to cause lung cancer.
centimeters. These regulations under 40 CFR Part 192.12
are often ARARs at Superfund sites. The EPA OSWER
Directive 9200.4-25, "Use of Soil Cleanup Criteria in 40
CFR Part 192 as Remediation Goals for CERCLA sites"
provides guidance regarding when of 5 pCi/g is an ARAR
or otherwise recommended cleanup level for any 15
centimeters of subsurface radium contaminated soil other
than the first 15 centimeters.
If regulations under 40 CFR Part 192.12 are an ARAR for
radium in soil at a Superfund site, then Nuclear Regulatory
Commission regulations for uranium mill tailing sites
under 10 CFR Part 40 Appendix A, I, Criterion 6(6) may
possibly be an ARAR at the same site. Criterion 6(6)
requires that an estimate be made of the level of radiation,
called a "benchmark dose," that an individual would
receive after that site was cleaned up to the radium soil
regulations under 40 CFR Part 192.12. This benchmark
dose then becomes the maximum level of radiation that an
individual may be exposed to from all radionuclides,
except radon, in both the soil and buildings at the site.
The EPA OSWER Directive 9200.4-35P "Remediation
Goals for Radioactivelv Contaminated CERCLA Sites
Using the Benchmark Dose Cleanup Criterion 10 CFR Part
40 Appendix A. I. Criterion 6f6V provides guidance
regarding how Criterion 6(6) should be implemented as an
ARAR at Superfund sites, including using a radium soil
cleanup level of 5 pCi/g in both the surface and
subsurface when estimating a benchmark dose.
EPA has established a Maximum Contaminant Level
(MCL) of 5 picocuries per liter (pCi/1) for any combination
of radium-226 and radium-228 in drinking water. EPA has
also established a MCL of 15 pCi/1 for alpha particle
activity, excluding radon and uranium, in drinking water.
Radium-226 would also be covered under this MCL.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to radium. General recommendations
EPA has made to protect human health, which cover all
radionuclides including radium, are summarized in the
Introduction section of this booklet.
For uranium mill tailing sites with radium contamination,
EPA has established a radium level of 5 picocuries per
gram (pCi/g) above background as a protective health
based level for the cleanup of soil in the top 15
For more information about how EPA addresses
radium at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.sov/superfund/resources/radiation
-------
EPA Facts About
Radon
July 2002
What is radon?
Radon is a naturally occurring radioactive gas without
color, odor, or taste, that undergoes radioactive decay and
emits ionizing radiation. Radon comes from the natural
(radioactive) breakdown of uranium and thorium in soil,
rock and ground water and is found all over the U.S. The
largest fraction of the public's exposure to natural radiation
comes from radon, mostly from soil under homes. [There
are three forms of radon, but this document refers primarily
to radon-222 and its progeny.]
How does radon change in the environment?
The primary source of radon is from uranium in soils and rocks,
and in ground water. Over time uranium decays into radium, which
then decays directly into radon. (See EPA Facts About Radium
and Uranium.) Uranium is present naturally in all soil, although
quantities differ from place to place. Because radon is a gas and
chemically unreactive with most materials, it moves easily through
very small spaces such as those between particles of soil and rock,
to the soil surface. Radon is also moderately soluble in water, and
it can be absorbed by ground water flowing through rock or sand.
Radon also undergoes radioactive decay, during which it releases
ionizing radiation and forms "daughter" elements, known as decay
products. It is the release of radiation from this decay process
that leads to exposure and health risks from radon.
During the decay process, radiation is released in the form of alpha
particles, beta particles, and gamma rays. Alpha particles can
travel only short distances and cannot penetrate human skin.
However, when inhaled they can penetrate the cells lining the
lungs. Beta particles penetrate skin, but cannot pass through the
entire body. Gamma radiation can travel all the way through the
body. The health risk associated with each type of radiation is a
function of how and what parts of the body are exposed. The
half-life of uranium-238 is about 4.5 billion years. The half-life of
radon is 3.8 days.
How are people exposed to radon?
Outside air typically contains very low levels of radon (about 0.4
pCi/L of air). But it can build up to higher concentrations in
indoor air from soil under foundations of homes, schools, and
office buildings where it can seep into buildings. EPA estimates
that the national average annual indoor radon level in homes is
about 1.3 pCi/L of air. However, over 6 percent of all homes
nationwide have elevated levels at or above EPA's voluntary
action level of 4 pCi/L. Levels greater than 2,000 pCi/L of air have
been measured in some homes.
Although radon in indoor air from soil gas typically accounts for
the bulk of the total radon risk to individuals, people may also be
exposed to radon and its daughters through use of drinking water
from ground water that contains radon. When water that contains
radon is used in the home for showering, washing dishes, and
cooking, radon gas escapes from the water and goes into the air.
Radon in domestic water generally contributes only a small
proportion (about 1 to 2%) of the total radon in indoor air. Radon
levels in air and ground water will generally be higher in areas of
the country with rock types that contain high amounts of uranium
and radium, such as phosphate or granite.
How does radon get into the body?
Radon and its radioactive daughters can enter the body through
inhalation and ingestion. Inhaling radon is the main route of entry
into the body, with most of the radon being exhaled again.
However, some radon and its daughter products will remain in the
lungs where radiation released during the decay process passes into
the lung tissues causing damage. Radon is also produced in the
body from parent radium deposited in the body.
Is there a medical test to determine exposure to
radon?
Radon in human tissue is not detectable by routine medical testing.
However, several of its decay products can be detected in urine, in
lung and bone tissue, and by breath tests. These tests however are
not generally available to the public. They are also of limited value
since they cannot be used to determine accurately how much radon
a person was exposed to, nor can these tests be used to predict
whether a person will develop harmful health effects.
-------
How can radon affect people's health?
Exposure to radon and its daughters increases the chance that a
person will develop lung cancer. The increased risk of lung cancer
from radon primarily results from alpha particles irradiating lung
tissues. Most of the damage is not from radon gas itself, which is
removed from the lungs by exhalation, but from radon's short-lived
decay products (half-life measured in minutes or less). When
inhaled, these decay products may be deposited in the airways of
the lungs especially if attached to dust particles and subsequently
emit alpha particles as they decay further, resulting in damage to
cells lining the airways.
Radon is considered a known human carcinogen based on extensive
studies of exposure to human beings. In two 1999 reports, the
National Academy of Sciences (NAS) concluded that radon in
indoor air is the second leading cause of lung cancer in the U.S.
after cigarette smoking. The NAS estimated that the annual
number of radon-related lung cancer deaths in the U.S., is about
15,000 to 22,000. NAS also estimated that radon in drinking water
causes about 180 cancer deaths each year in the United States.
Approximately 89% of these cancer deaths are due to lung cancer
from inhalation of radon released to indoor air from the water, and
about 11 % are due to cancers of internal organs, mostly stomach
cancers, from ingestion of radon in water.
National Radon Hotline (800) 767-7236 or EPA's web site
http://www.epa.gov/iaq/radon.
There is currently a proposed Maximum Contaminant Level
(MCL) for radon in drinking water from community water
systems using ground water. The Safe Drinking Water Act directs
EPA to set both a maximum contaminant level (MCL) for radon in
drinking water, as well as an alternative, higher alternative
maximum contaminant level (AMCL) accompanied by a
multimedia mitigation program to address radon risks in indoor air.
This approach reflects radon's unique characteristics: that radon
released to indoor air from soil under homes and buildings in most
cases is the main source of exposure, with radon released from tap
water being a much smaller source of radon exposure. For more
information, contact the Safe Drinking Water Hotline at (800) 426-
4791 or EPA's web site at http://www.epa.gov/safewater.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited to
recommendations EPA has made to protect human health from
exposure to radon. General recommendations EPA has made to
protect human health, which cover all radionuclides including
radon, are summarized in the Introduction section of this booklet.
For uranium mill tailings sites, at which radon poses the major
health threat, EPA has established a limitation to exposure to
radon decay products of less than 0.02 Working Levels (WL).
These regulations under 40 CFR Part 192.12(b) are often ARARs
at Superfund sites with either radium or thorium contaminated soil.
In 1988, EPA and the U.S. Surgeon General issued a Health
Advisory recommending that all homes below the third floor be
tested for radon and fixed if the radon level is at or above 4
picocuries per liter (pCi/L), EPA's national voluntary Action
Level. EPA and the Surgeon General also recommend that schools
nationwide be tested for radon. (Exposure to 4 pCi/1 of radon
corresponds to an approximate annual average exposure of 0.02
WL for radon decay products in the home.) For more details, see
EPA's "A Citizen's Guide to Radon, September 1994, USEPA
#402-K92-001 and "Consumer's Guide to Radon Reduction",
August 1992, USEPA 402-K92-003. For copies, contact the
For more information about how EPA addresses radon at
Superfund sites, please contact either :
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
httv://www.eva.sov/suverfund/resources/radiation
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*•<
: EPA Facts About
• Strontium-9O
July 2002
What is strontium-90?
Radioactive strontium-90 is produced as a fission
byproduct of uranium and plutonium. Large amounts
of radioactive strontium-90 were produced during
atmospheric nuclear weapons tests conducted in the
1950s and 1960s. As a result of atmospheric testing
and radioactive fallout, this strontium was dispersed
and deposited on the earth.
What are the uses of strontium-90?
Strontium-90 is used as a radioactive tracer in medical and
agricultural studies. It is also used in thermoelectric
devices that are built into small power supplies for use in
remote locations, such as navigational beacons, remote
weather stations, and space vehicles. Strontium-90 is also
used in electron tubes, as a radiation source in industrial
thickness gauges, and for treatment of eye diseases.
How does strontium-90 change in the
environment?
Strontium-90 is not a stable isotope. Strontium-90 decays
to yttrium-90, which in turn decays to stable zirconium.
The isotopes of strontium and yttrium emit beta particles
as they decay. The release of radiation during this decay
process causes concern about the safety of strontium and
all other radioactive substances. Beta particles can pass
through skin, but they cannot pass through the entire
body.
The most common isotope of strontium is strontium-90.
Strontium-90 has a half-life of 29 years and emits beta
particles of relatively low energy as it decays. Yttrium-90,
its decay product, has a shorter half-life (64 hours) than
strontium-90, but it emits beta particles of higher energy.
How are people exposed to strontium-90?
Although external exposure to strontium-90 from nuclear
testing is of minor concern because environmental
concentrations are low, strontium in the environment can
become part of the food chain. This pathway of exposure
became a concern in the 1950s with the advent of
atmospheric testing of nuclear explosives. With the
suspension of atmospheric testing of nuclear weapons,
dietary intake has steadily fallen in the last 30 years.
These concerns have shifted somewhat to exposure
related to possible accidents at nuclear reactors or fuel
reprocessing plants, and exposure to high level waste at
weapons facilities. Strontium-90 is a component of
contaminated soils at radioactively contaminated sites
where nuclear fission has been used (e.g., research
reactors and nuclear power plants).
Accidents involving nuclear reactors such as Chernobyl
have released strontium into the atmosphere, which
ultimately settles to the earth's surface as fallout.
Chernobyl contributed the largest worldwide burden of
strontium-90 contamination, and a substantial portion of
the strontium-90 released was deposited in the former
Soviet Republics; with the rest being dispersed as fallout
worldwide.
How does strontium-90 get into the body?
Ingestion, usually through the swallowing of food or
water, is the primary health concern for entry of strontium
into the human body. Small dust particles contaminated
with strontium also may be inhaled, but this exposure
pathway is of less concern than the ingestion pathway.
After radioactive strontium is ingested, 20 to 30 percent of
it is absorbed from the gastrointestinal tract, while the rest
is excreted. Of the portion absorbed, virtually all (99
percent) of the strontium is deposited in the bone volume
or skeleton. The balance is distributed among the blood
stream, extracellular fluid, soft tissue, and bone surface,
where it may stay and decay or be metabolized and
excreted in urine and fecal matter.
Is there a medical test to determine exposure
to strontium-90?
Generally, levels of strontium in the body are measured by
urinalysis. As with most cases of internal contamination,
the sooner after an intake the measurement is made, the
more accurate it is.
-------
How can strontium affect people's health?
Strontium-90 behaves like calcium in the human body and
tends to deposit in bone and blood-forming tissue (bone
marrow). Thus, strontium-90 is referred to as a "bone
seeker" and exposure to it will increase the risk for several
diseases including bone cancer, cancer of the soft tissue
near the bone, and leukemia. Risks from exposure depend
on the concentration on strontium-90 in air, water, and
soil. At higher exposures, such as those associated with
the Chernobyl accident, or other conceivable scenarios
involving nuclear accidents or exposure to radioactive
waste materials, the cancer risks may be elevated. The
magnitude of this health risk would depend on exposure
conditions, such as amount ingested.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to strontium-90. General
recommendations EPA has made to protect human health,
which cover all radionuclides including strontium-90, are
summarized in the Introduction section of this booklet.
EPA has established a Maximum Contaminant Level
(MCL) of 4 millirem per year for beta particle and photon
radioactivity from man-made radionuclides in drinking
water. The average concentration of strontium-90 which
is assumed to yield 4 millirem per year is 8 picocuries per
liter (pCi/1). If other radionuclides which emit beta
particles and photon radioactivity are present in addition
to strontium-90, the sum of the annual dose from all the
radionuclides shall not exceed 4 millirem/year.
For more information about how EPA addresses
strontium-90 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.eov/superfund/resources/radiation/
index.htm
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*•<
: EPA Facts About
• Technetium-99
July 2002
What is technetium-99?
Technetium-99 (Tc-99) is predominantly an artificially
produced radioactive metal. Tc-99 also occurs naturally in
very small amounts in the earth's crust. Tc-99 was first
obtained from molybdenum but is also produced as a nuclear
reactor fission product of uranium and plutonium. All
isotopes of technetium are radioactive, and the most
commonly available forms are Tc-99 and Tc-99m.
In addition to being produced during nuclear reactor
operation, Tc-99 is produced in atmospheric nuclear
weapons tests. Metastable Tc-99 (Tc-99m), the shorter-
lived form of Tc-99, is also a component of nuclear reactor
gaseous and liquid effluent. Tc-99m is used primarily as a
medical diagnostic tool, and it can be found as a component
of industrial and institutional wastes from hospitals and
research laboratories..
What are the uses of technetium-99?
Tc-99 is an excellent superconductor at very low temperatures.
In addition, Tc-99 has anti-corrosive properties. Five parts of
technetium per million will protect carbon steels from corrosion
at room temperature. Tc-99m is used in medical therapy in
brain, bone, liver, spleen, kidney, and thyroid scanning and for
blood flow studies. Tc-99m is the radioisotope most widely
used as a tracer for medical diagnosis.
How does technetium-99 change in the
environment?
Technetium-99 is not a stable isotope. As Tc-99 decays, it
releases beta particles and eventually forms a stable nucleus.
Beta particles can pass through skin, but they cannot pass
through the entire body. The time required for a radioactive
substance to lose 50 percent of its radioactivity by decay is
known as the half-life. The half life of Tc-99 and Tc-99m is
210,000 years and 6 hours respectively.
How are people exposed to technetium-99?
Man-made Tc-99 has been found in isolated locations at federal
sites in the ground water beneath uranium processing facilities.
Tc-99 contamination at these selected sites is a concern if
individuals are exposed to Tc-99 through drinking contaminated
water and ingesting contaminated plants. The potential
exposure from external radiation by Tc-99 is minimal because
the isotope is a weak beta emitter. Tc-99m is not a concern at
these sites because of its short half-life. Tc-99 is also found in
the radioactive waste of nuclear reactors, fuel cycle facilities, and
hospitals.
In the natural environment, Tc-99 is found at very low
concentrations in air, sea water, soils, plants, and animals. The
behavior of Tc-99 in soils depends on many factors. Organic
matter in soils and sediments plays a significant role in
controlling the mobility of Tc-99. In soils rich in organic matter,
Tc-99 is retained and does not have high mobility. Under
aerobic conditions, technetium compounds in soils are readily
transferred to plants. Some plants such as brown algae living in
seawater are able to concentrate Tc-99. Tc-99 can also transfer
from seawater to animals.
How does technetium-99 get into the body?
At radioactively contaminated sites with Tc-99 contamination,
the primary routes of exposure to an individual are from the
potential use of contaminated drinking water and ingestion of
contaminated plants.
Technetium exposure may occur to persons working in research
laboratories that perform experiments using Tc-99 and Tc-99m.
Patients undergoing diagnostic procedures may receive
controlled amounts of Tc-99m, but also avoid a more invasive
diagnostic technique.
Is there a medical test to determine exposure
to technetium-99?
Special tests that measure the level of radioactivity from Tc-99
or other technetium isotopes in the urine, feces, hair, and exhaled
air can determine if a person has been exposed to technetium.
These tests are useful only if performed soon after exposure.
The tests require special equipment and cannot be done in a
doctor's office.
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How can technetium-99 affect people's health?
Once in the human body, Tc-99 concentrates in the thyroid
gland and the gastrointestinal tract. The body, however,
constantly excretes Tc-99 once it is ingested. As with any other
radioactive material, there is an increased chance that cancer or
other adverse health affects can result from exposure to
radiation.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited to
recommendations EPA has made to protect human health from
exposure to technetium-99. General recommendations EPA has
made to protect human health, which cover all radionuclides
including technetium-99, are summarized in the Introduction
section of this booklet.
EPA has established a Maximum Contaminant Level (MCL) of
4 millirem per year for beta particle and photon radioactivity
from man-made radionuclides in drinking water. Technetium-99
would be covered under this MCL. The average concentration
of technetium-99 which is assumed to yield 4 millirem per year
is 900 picocuries per liter (pCi/1). If other radionuclides which
emit beta particles and photon radioactivity are present in
addition to technetium-99, the sum of the annual dose from all
the radionuclides shall not exceed 4 millirem/year.
For more information about how EPA addresses
technetium-99 at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www.epa.sov/superfund/resources/radiation
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*•<
: EPA Facts About
• Thorium
July 2002
What is thorium?
Thorium is a naturally occurring radioactive metal that
is found at low levels in soil, rocks, water, plants and
animals. Almost all naturally occurring thorium exists
in the form of either radioactive isotope thorium-232,
thorium-230 and thorium-228. There are more than 10
other thorium isotopes that can be artificially
produced. Smaller amounts of these isotopes are
usually produced as decay products of other
radionuclides and as unwanted products of nuclear
reactions.
What are the uses of thorium?
Thorium is used to make ceramics, lantern mantles,
welding rods, camera and telescope lenses, and metals
used in the aerospace industry.
How does thorium change in the environment?
Thorium-232 is not a stable isotope. As thorium-232
decays, it releases radiation and forms decay products
which include radium-228 and thorium-228. The decay
process continues until a stable, nonradioactive decay
product is formed. In addition to thorium-232, thorium-228
is present in background. Thorium-228 is a decay product
of radium-228 and thorium-228 decays into radium-224.
The radiation from the decay of thorium and its decay
products is in the form of alpha and beta particles, and
gamma radiation. Alpha particles can travel only short
distances and cannot penetrate human skin. Beta particles
are generally absorbed in the skin and do not pass
through the entire body. Gamma radiation, however, can
penetrate the body.
The half-life of thorium-232 is very long at about 14 billion
years. Due to the extremely slow rate of decay, the total
amount of natural thorium in the earth remains fairly
constant, but it can be moved from place to place by
natural processes and human activities.
How are people exposed to thorium?
Since thorium is present at very low levels almost
everywhere in the natural environment, everyone is
exposed to it in air, food, and water. Normally, very little
of the thorium in lakes, rivers, and oceans is absorbed by
the fish or seafood that a person eats. The amounts in the
air are usually small and do not constitute a health hazard.
Exposure to higher levels of thorium may occur if a person
lives near an industrial facility that mines, mills or
manufactures products with thorium.
Thorium-232 on the ground is of a health risk because of
the rapid build up of radium-228 and its associated gamma
radiation. Thorium-230 is part of the uranium-238 decay
series. Thorium- 230 is typically present with its decay
product radium-226 and it is therefore a health risk from
gamma radiation from radium decay products, lung
exposure from radon gas and its decay products, and
inhalation and ingestion exposure.
How does thorium get into the body?
Thorium can enter the body when it is inhaled or
swallowed. In addition, radium can come from thorium
deposited in the body. Thorium enters the body mainly
through inhalation of contaminated dust. If a person
inhales thorium into the lungs, some may remain there for
long periods of time. In most cases, the small amount of
thorium left in the lungs will leave the body in the feces
and urine within days.
If thorium is swallowed in water or with food, most of it
will promptly leave the body in the feces. The small
amount of thorium left in the body will enter the
bloodstream and be deposited in the bones, where it may
remain for many years.
Is there a medical test to determine exposure
to thorium?
Special tests that measure the level of radioactivity from
thorium or thorium isotopes in the urine, feces, and
exhaled air can determine if a person has been exposed to
thorium. These tests are useful only if taken within a
short period of time after exposure. They require special
equipment and cannot be done in a doctor's office.
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How can thorium affect people's health?
Studies of workers have shown that inhaling thorium dust
will cause an increased risk of developing lung disease,
including lung cancer, or pancreatic cancer. Liver disease
and some types of cancer have been found in people
injected in the past with thorium in order to take special X-
rays. Bone cancer is also a potential health effect due to
the storage of thorium in the bone.
What recommendations has the Environmental
Protection Agency made to protect human
health?
EPA has established a Maximum Contaminant Level
(MCL) of 15 picocuries per liter (pCi/1) for alpha particle
activity, excluding radon and uranium, in drinking water.
Thorium would be covered under this MCL.
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to thorium. General
recommendations EPA has made to protect human health,
which cover all radionuclides including thorium, are
summarized in the Introduction section of this booklet.
For uranium mill tailing sites, EPA has established 5
picocuries per gram (pCi/g) of radium as a protective
health based level for the cleanup of the top 15
centimeters of soil. Since thorium decays into radium,
these regulations for radium under 40 CFR Part 192.12
have often been used as ARARs at Superfund sites for
thorium contaminated soil. The EPA OSWER Directive
9200.4-25, "Use of Soil Cleanup Criteria in 40 CFR Part 192
as Remediation Goals for CERCLA sites" provides
guidance regarding when 5 pCi/g of thorium is an ARAR
or otherwise recommended cleanup level for any 15
centimeters of subsurface thorium contaminated soil other
than the first 15 centimeters.
If regulations under 40 CFR Part 192.12 are an ARAR for
radium in soil at a Superfund site, then NRC regulations
for uranium mill tailing sites under 10 CFR Part 40
Appendix A, I, Criterion 6(6) may possibly be an ARAR at
the same site. Criterion 6(6) requires that an estimate be
made of the level of radiation, called a "benchmark dose,"
that an individual would receive after that site was
cleaned up to the radium soil regulations under 40 CFR
Part 192.12. This benchmark dose then becomes the
maximum level of radiation that an individual may be
exposed to from all radionuclides, except radon, in both
the soil and buildings at the site. The EPA OSWER
Directive 9200.4-35P, "Remediating Goals for
Radioactivelv Contaminated CERCLA Sites Using the
Benchmark Dose Cleanup Criterion 10 CFR Part 40
Appendix A, L Criterion 6(6)" provides guidance
regarding how Criterion 6(6) should be implemented as an
ARAR at Superfund sites, including using a radium soil
cleanup level of 5 pCi/g in both the surface and
subsurface when estimating a benchmark dose.
For more information about how EPA addresses
thorium at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
httv: //www. eva.sov/suverfund/re sources/radiation
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*•<
EPA Facts About
Tritium
July 2002
What is Tritium?
Tritium is a form of hydrogen that is radioactive, and
like hydrogen it reacts with oxygen to form water.
Tritium is produced naturally in the upper atmosphere
when cosmic rays strike atmospheric gases. Tritium
can also be produced by man during nuclear weapon
explosions, in reactors intended to produce tritium for
nuclear weapons, and by reactors producing
electricity.
What are the uses of tritium?
Tritium has been produced in large quantities by the
nuclear military program. It is also used to make luminous
dials and as a source of light for safety signs. Tritium is
used as a tracer for biochemical research, animal
metabolism studies and ground water transport
measurements.
How does tritium change in the environment?
Tritium is not a stable element. Tritium decays by emitting
a beta particle and turning into helium. The release of
radiation during this decay process causes concern about
the safety of tritium and all other radioactive substances.
The radiation from the decay of tritium is in the form of
beta particles which are of very low energy. Because of
this the particles cannot pass through the skin surface.
Tritium is the only radioactive isotope of hydrogen and
like hydrogen it reacts with oxygen to form water. The
transformation of tritium to tritiated water is a complex and
slow process. Tritium is a colorless, odorless gas with a
half-life of 12.3 years. Tritiated water moves through the
environment like ordinary water.
How are people exposed to tritium?
Although large quantities of tritium have been released
into the environment, the dose to humans is small. Tritium
was disbursed throughout the world by atmospheric
nuclear weapons tests that took place from the mid 1950s
to the early 1960s. The inventory of tritium in the
atmosphere peaked in 1963 and has been decreasing
rapidly since then. Levels of naturally occurring tritium in
the atmosphere produced by cosmic rays are constant,
and it is projected that levels of manmade tritium will be
comparable to natural tritium by 2030.
Tritium is currently produced by reactors producing
electricity. However, releases of tritium from these
facilities are at fractions of the natural background
production rates. Other sources of tritium include
government plants which have reprocessed reactor fuels.
Individuals can also be exposed to tritium broken exit
signs and luminous dial items that contain tritium.
Since tritium reacts similarly to ordinary hydrogen it is
incorporated into the body easily in the form of water.
Overall, since current world wide levels of tritium in the
environment from man-made and natural sources are low,
the risk to the average person from tritium is typically not
significant. Accidental exposure from elevated levels of
tritium from broken exit signs or other concentrated
sources, however can pose a health risk to individuals.
How does tritium get into the body?
Most tritium in the environment is in the form of tritiated
water which is dispersed throughout the environment in
the atmosphere, streams, lakes, and oceans. Tritium in the
environment can enter the human body as a gas or as a
liquid by ingestion and inhalation, and through the skin
by absorption. Once entered into the body, tritium tends
to disperse quickly so that it is uniformly distributed
throughout the body. The tritium distribution in tissue is
dependent on the amount of water contained in the
tissues. Tritium is rapidly excreted over a month or two
after ingestion.
Is there a medical test to determine exposure
to tritium?
Since tritium is distributed throughout the body within a
few hours after ingestion, levels within the body are
measured by collecting a urine sample and analyzing it for
tritium.
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How can tritium affect people's health?
With respect to chemical reactions, tritium reacts similarly
to ordinary hydrogen. Tritium therefore dilutes through
the body as ordinary water. Tritium concentration in soft
tissue and the associated dose to these tissues is
generally uniform and dependent on the water content of
the tissue. Because the water content in the body turns
over frequently, tritium is rapidly cleared from tissues.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Please note that the information in this section is limited
to recommendations EPA has made to protect human
health from exposure to tritium. General recommendations
EPA has made to protect human health, which cover all
radionuclides including tritium, are summarized in the
Introduction section of this booklet.
EPA has established a Maximum Contaminant Level
(MCL) of 4 millirem per year for beta particle and photon
radioactivity from man-made radionuclides in drinking
water. The average concentration of tritium which is
assumed to yield 4 millirem per year is 20,000 picocuries
(pCi/1). If other radionuclides which emit beta particles
and photon radioactivity are present in addition to tritium,
the sum of the annual dose from all the radionuclides shall
not exceed 4 millirem/year.
For more information about how EPA addresses
tritium at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
http://www. epa. sov/superfund/resources/radiation/
index.htm
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*•<
: EPA Facts About
• Uranium
July 2002
What is uranium?
Uranium is a radioactive metal that is present in low amounts
in rocks, soil, water, plants, and animals. Uranium and its
decay products contribute to low levels of natural
background radiation in the environment. Significant
concentrations of uranium occur naturally in some
substances such as phosphate deposits and uranium-
enriched ores.
How does uranium change in the environment?
Natural uranium is found in the environment in three forms,
called isotopes: uranium-234, uranium-235, and uranium-238.
Ninety-nine percent of natural uranium occurring in rock is
uranium-238. Uranium-235 accounts for just 0.72 percent of
natural uranium, but it is more radioactive than uranium-238.
Uranium-234 is the least abundant uranium isotope in rock.
Uranium is not a stable element. As uranium decays, it releases
radiation and forms decay products. Uranium-238 decay
products include uranium-234, radium-226, andradon-222. See
EPA Fact About Radon and Radium for additional information
on these radionuclides.
Natural uranium releases alpha particles and low levels of
gamma rays. Alpha particles can travel only short distances and
cannot penetrate human skin. Gamma radiation, however, can
penetrate the body.
The half-life for uranium-238 is about 4.5 billion years, uranium-
235 is 710 million years and uranium-234 is 250,000 years.
Because of the slow rate of decay, the total amount of natural
uranium in the earth stays almost the same, but radionuclides
can move from place to place through natural processes or by
human activities. Rain can wash soil containing uranium into
rivers and lakes. Mining, milling, manufacturing, and other
human activities also release uranium to the environment.
What are the uses of uranium?
Uranium-235 is used in nuclear weapons and nuclear reactors.
Depleted uranium (natural uranium in which almost all of the
uranium-235 has been removed) is used to make ammunition for
the military, guidance devices and compasses, radiation shielding
material, and X-ray targets. Uranium dioxide is used to extend
the lives of incandescent lamps used for photography and
motion pictures. Very small amounts of other uranium
compounds are used in photography for toning, in the leather
and wood industries for stains and dyes, and in the wool
industries. Uranium has also been used in the past in ceramics
as a coloring agent.
How are people exposed to uranium?
Uranium-238 and members of its decay chain which include
uranium-234, radium-226, and radon-220 are present in nature.
The members of the decay chain in undisturbed soil are present
often at concentrations that approximate that of the parent
uranium-238. Uranium ore contains all the daughter elements of
uranium-238 and uranium-235, but during uranium processing
the uranium-238, uranium-234 and uranium-235 are extracted
and chemically separated. This concentrated uranium product
which is generated at uranium mill tailing sites and uranium
processing facilities is a potential source of exposure to
individuals and the environment and is a primary concern for the
cleanup of these sites. Potential individual exposure at these
sites may be from different pathways, but because of the
mobility of uranium the ground water pathway is of particular
How does uranium get into the body?
Uranium can enter the body when it is inhaled or swallowed or
through cuts in the skin. About 99 percent of the uranium
ingested in food or water will leave a person's body in the feces,
and the remainder will enter the blood. Most of this uranium
will be removed by the kidneys and excreted in the urine within
a few days. A small amount of the uranium in the bloodstream
will be deposited in a person's bones, where it will remain for
several years.
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Alpha particles released by uranium cannot penetrate the skin,
so natural uranium that is outside the body is less harmful than
that which is inhaled, swallowed or enters through the skin.
When uranium gets inside the body, radiation and chemical
damage can lead to cancer or other health problems including
kidney damage.
Is there a medical test to determine exposure
to uranium?
Tests are available to measure the amount of uranium in a urine
or stool sample. These tests are useful if a person is exposed to
a larger-than-normal amount of uranium, because most uranium
leaves the body in the feces within a few days. Uranium can be
found in the urine for up to several months after exposure.
However, the amount of uranium in the urine and feces does not
always accurately show the level of uranium exposure. Since
uranium is known to cause kidney damage, urine tests are often
used to determine whether kidney damage has occurred.
How can uranium affect people's health?
In addition to the risks of cancer posed by uranium and all other
radionuclides, uranium is associated with non-cancer effects and
the major target organ of uranium's chemical toxicity is the
kidney. Radioactivity is a health risk because the energy
emitted by radioactive materials can damage or kill cells. The
level of risk is dependent on the level of uranium concentration.
What recommendations has the Environmental
Protection Agency made to protect human
health?
Superfund site, then NRC regulations for uranium mill tailing
sites under 10 CFR Part 40 Appendix A, I, Criterion 6(6) may
possibly be an ARAR at the same site, particularly if uranium-
234 or uranium-238 is a contaminant at the site. Criterion 6(6)
requires that an estimate be made of the level of radiation, called
a "benchmark dose," that an individual would receive after that
site was cleaned up to the radium soil regulations under 40 CFR
Part 192.12. This benchmark dose then becomes the maximum
level of radiation that an individual may be exposed to from all
radionuclides, except radon, in both the soil and buildings at the
site. The EPA OSWER Directive 9200.4-35P, "Remediating
Goals for Radioactivelv Contaminated CERCLA Sites Using the
Benchmark Dose Cleanup Criterion 10 CFR Part 40 Appendix
A, I. Criterion 6(6Y' provides guidance regarding how Criterion
6(6) should be implemented as an ARAR at Superfund sites,
including using a radium soil cleanup level of 5 pCi/g in both the
surface and subsurface when estimating a benchmark dose.
Please note that the information in this section is limited to
recommendations EPA has made to protect human health from
exposure to uranium. General recommendations EPA has made
to protect human health, which cover all radionuclides including
uranium, are summarized in the Introduction section of this
booklet.
EPA has established a Maximum Contaminant Level (MCL) of
30 micrograms per liter (ug/liter) for uranium in drinking water.
For uranium mill tailing sites, EPA has established 30 picocuries
per Liter (pCi/1) for uranium 234 and 238 as standards for
protecting groundwater. The EPA OSWER Directive 9283.1-14
"Use of Uranium Drinking Water Standards under 40 CFR 141
and 40 CFR 192 as Remediation Goals for Groundwater at
CERCLA sites" provides guidance regarding how these two
standards should be implemented as an ARAR at Superfund
sites.
For uranium mill tailing sites, EPA has established 5 picocuries
per gram (pCi/g) of radium as a protective health based level for
the cleanup of the top 15 centimeters of soil. If regulations
under 40 CFR Part 192.12 are an ARAR for radium in soil at a
For more information about how EPA addresses uranium
at Superfund sites, please contact either:
EPA 's Superfund Hotline
1-800-424-9346 or 1-800-535-0202
or EPA 's Superfund Radiation Webpage
httv://www.eva.sov/suverfund/resources/radiation
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