United States
Environmental Protection Agency
Office of Superfund
Remediation and
Technology Innovation
Directive 9230.1-48
EPA-540-R-012-015
May 2014
Superfund Radiation Risk Assessment:
A Community Toolkit
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Introduction
This toolkit was developed by the U.S. Environmental Protection Agency (EPA) to help
the public understand more about the risk assessment process used at Superfund sites
with radioactive contamination. The toolkit is made up of a collection of 22 fact sheets
that provide information that may be important to the risk assessment process for
Superfund sites with radioactive contamination. Not all of these fact sheets will be
useful at all sites. It is recommended EPA staff working on a site provide only the fact
sheets that are useful for the public at that specific site. The fact sheets will also be
available on the Internet for any interested members of the public. The fact sheets in
this toolkit are:
1. Superfund Radiation Fact Sheet (10 pages)
2. Superfund Radiation Risk Assessment Fact Sheet (8 pages)
Attachment A: Compendium of Information on the Preliminary Remediation Goal (PRG)
and Dose Compliance Concentration (DCC) Calculators
3. Primer on EPA PRG and DCC Calculators (1 page)
4. Preliminary Remediation Goals (PRG) Calculator (1 page)
5. Dose Compliance Concentration (DCC) Calculator (1 page)
6. Building Preliminary Remediation Goals (BPRG) Calculator (1 page)
7. Building Dose Compliance Concentration (BDCC) Calculator (1 page)
8. Surface Preliminary Remediation Goals (SPRG) Calculator (1 page)
9. Surface Dose Compliance Concentration (SDCC) Calculator (1 page)
Attachment B: Compendium of Information on Radionuclides Commonly Found at
Superfund Sites
lO.Primer on Radionuclides Commonly Found at Superfund Sites (2 pages)
ll.Americium-241(2 pages)
12.Cesium-137 (2 pages)
13.Cobalt-60 (2 pages)
14.lodine (2 pages)
15.Plutonium (2 pages)
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16.Radium (3 pages)
17.Radon (3 pages)
18.Strontium-90 (2 pages)
19.Technecium-99 (2 pages)
20.Thorium (3 pages)
21.Tritium (2 pages)
22.Uranium (2 pages)
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I
1
Superfund Radiation Fact Sheet
What is Superfund? The Superfund program is administered by U.S. Environmental
Protection Agency (EPA) in cooperation with state and tribal governments. It allows
EPA to clean up hazardous waste sites and to force responsible parties to perform
cleanups or reimburse the government for cleanups led by EPA.
For a variety of reasons, hazardous
commercial and industrial wastes were
mismanaged and may pose unacceptable
risks to human health and the
environment. This waste was dumped on
the ground or in waterways, left out in
the open, or otherwise improperly
managed. As a result, thousands of
hazardous waste sites were created
throughout the United States. These
hazardous waste sites commonly include
manufacturing facilities, processing
plants, landfills, and mining sites.
Superfund was established in 1980 by an
act of Congress, giving EPA the funds and
authority to clean up polluted sites
Goals of Suoerfund:
1 Protect human health and the
environment by cleaning up
polluted sites
• Involve communities in the
Superfund process
1 Make responsible parties pay for
work performed at Superfund
Superfund is the informal name for the
Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA).
In 1980, Congress enacted CERCLA in
response to growing concerns over the
health and environmental risks posed by
hazardous waste sites. This law was
enacted in the wake of the discovery of
chemically contaminated toxic waste
dumps such as Love Canal and Valley of
the Drums in the 1970s.
Some Superfund sites contain radioactive
contamination. This document was
developed by EPA to answer questions
about radiation hazards and how EPA
assesses health risks from potential
exposure to radioactive contamination at
Superfund sites.
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What are atoms?
To understand radiation and
radioactivity, it is important to
understand atoms.
Atoms are the very small particles that
make up our bodies and everything
around us. Atoms consist of a central
nucleus made up of protons and
neutrons. Protons are positively charged,
while neutrons have no charge. Electrons
have a negative charge and orbit (or go
around) the nucleus. Most atoms are
neutral, which means they have the same
number of protons and electrons. Atoms
that are not neutral are called ions.
Atomic Structure
4
Electron
An atom consists of a central nucleus (made
of protons and neutrons) orbited by
electrons
An element is a specific type of atom. All
atoms of an element have the same
number of protons. For example, all
atoms of oxygen have eight protons,
while all uranium atoms have 92 protons.
It is possible for atoms of the same
element to have different numbers of
neutrons. These various forms are called
isotopes. For example, while all atoms of
oxygen have eight protons, isotopes of
oxygen can have from four to 16
neutrons.
What is Radiation?
Radiation is energy that travels in the
form of waves or high-speed particles.
There are two types of radiation:
• Non-ionizing radiation is low energy.
It includes radio waves, microwaves,
and visible light. Non-ionizing
radiation can generate heat, but it
does not have enough energy to
remove electrons from atoms.
• Ionizing radiation is high energy. It
can remove tightly bound electrons
from an atom. Ionizing radiation can
be harmful to humans by damaging
living tissue and increasing cancer risk.
X-rays are a familiar form of ionizing
radiation.
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Common Types of Radiation
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In this fact sheet, the term "radiation"
will mean ionizing radiation.
What is Radioactivity?
Some isotopes of certain atoms are
unstable. When these unstable atoms
release ionizing radiation in the form of
waves or particles, it is called
radioactivity. A radioactive atom is called
a radionuclide. When a radionuclide
emits (gives off) radiation, it is said to
decay. There are three main types of
radiation given off when a radionuclide
decays:
• Alpha particles are heavy, relatively
slow moving, particles. They can be
blocked by a piece of paper or by skin.
However, radionuclides that give off
alpha particles can be very harmful if
they enter your body in other ways
such as through the air, food, or water
because your internal organs are not
protected by skin.
Beta particles are light weight,
relatively fast moving particles. They
can be blocked by a thin piece of
metal or wood. Beta particles can
penetrate (pass through) the outer
layer of skin and cause radiation
burns. Like alpha particles, beta
particles can damage your health if
they enter your body.
Gamma rays are waves of pure energy
that often accompany beta and alpha
particles. Gamma rays can pass
through the body and damage internal
organs. A thick wall of metal or
concrete is needed to absorb gamma
radiation.
Radiation Penetrating Power
Alpha"
Beta
Gamma
A/\A
,
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Ionizing Radiation Found at Superfund Sites
Alpha Particles
Beta Particles
Gamma Rays
Description
Two protons and two
neutrons bound together
into a single particle
Heaviest and slowest
moving type of ionizing
radiation
Positively charged
Made up of an electron
ejected from nucleus
Fast moving, low mass
particle
Negatively charged
Pure energy traveling
at the speed of light
Often accompanies
the emission of alpha
or beta particles
Has no rest mass and
no charge
Ionizing
Power
• HIGH
• Interacts strongly with
surrounding material
• Very energetic
• MODERATE
• Interact less strongly
than alpha particles but
more strongly than
gamma rays with
surrounding material
• LOW
• Since they have no
mass and no charge,
gamma rays interact
with matter less than
alpha and beta
particles
Penetrating
Power
LOW
Travels no more than a
few centimeters in air
Can be stopped by a sheet
of paper
Unable to penetrate skin
MODERATE
Able to travel several
meters through air
Can be stopped by a
thin layer of metal or
plastic
Can penetrate outer
layers of skin
HIGH
Able to travel
hundreds of meters
through air
Can be stopped by a
thick concrete wall
Able to pass through
the human body
Human
Health
Effects
No health effects from
external exposure since
they are unable to
penetrate skin
Very harmful if alpha-
emitting radionuclide is
taken into the body by
ingestion,r breathing, or
through an open wound
Can cause skin burns
from external exposure
Harmful if taken into
the body (though not
usually as harmful as
alpha particles)
Can cause harm from
external exposure
Can pass into the
body and cause
internal radiation
exposure
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What happens to radionuclides as
they decay?
As radionuclides decay, they become new
elements called daughter products,
which are also known as decay products.
These daughter products may or may not
be radioactive themselves. If a daughter
product is also radioactive, it in turn will
decay to form a different daughter
product. This process will continue until a
stable, nonradioactive product is formed.
The radioactive decay of a radionuclide
and all of its daughters is known as a
decay chain.
What is half-life?
The rate a radionuclide decays is its half-
life. Half-life is defined as the amount of
time it takes for half of the amount of a
substance to emit radiation and change
to a different substance. Radionuclide
half-lives can be very long or very short.
For example, uranium-238 has a half-life
of 4.5 billion years, while carbon-11 has a
half-life of only a few minutes.
How is radioactivity measured?
Radioactivity is measured by the activity
of a material. The activity is the number
of radionuclides that decay each second.
EPA often uses a unit called a curie to
measure activity. One curie is 37 billion
decays per second. This unit is too large
to use at most Superfund sites to assess
radiation risk, so EPA usually uses a unit
called a picocurie. One picocurie is equal
to one trillionth of a curie, or about 2.2
radionuclide decays per minute.
EPA measures radioactive contamination
by the number of picocuries measured in
a specific amount of contaminated
material. Soil contamination, for
example, is measured in picocuries per
gram.
Why are radionuclides harmful to
human health?
The human body is made up of atoms.
When radionuclides decay, they release
alpha, beta, and gamma radiation. This
radiation can break the bonds between
the atoms, damaging living tissue and
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DNA. Usually, our bodies can repair this
type of damage, but sometimes there
may be too much damage to repair. This
damage to living tissue and DNA can lead
to cancer or other health effects. The risk
of cancer increases as exposure to
radiation increases.
How can you be exposed to harmful
radiation?
Radionuclides cause the most harm when
they are inside of the body. There are
three ways to be exposed to
radionuclides:
• Inhalation - Breathing contaminated
vapors, dust particles, or radon gas.
• Ingestion - Eating contaminated food,
drinking contaminated water, or
accidentally ingesting small amounts
of contaminated dust or soil.
• External - Radiation emitting out from
a source such as radioactively
contaminated soil or object, and then
penetrating from outside of the body.
How is radiation exposure
measured?
Under most situations, radiation
exposure is measured in dose. Dose is
related to the amount of radiation
absorbed by a person's body. The unit for
radiation dose that EPA uses is the
millirem. Millirem relates the absorbed
dose of radiation to the amount of
biological damage from the radiation.
However, radiation exposure at
Superfund sites is measured by cancer
risk. All radionuclides can cause cancer,
and the cancer risk increases as exposure
increases. Not all radiation has the same
biological effect, even when the absorbed
dose is the same, however. Therefore,
EPA's use of cancer risk accounts for the
different types of radiation as well as its
effects on different parts of the body.
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How does EPA calculate risks to
human health from radiation
exposure at Suoerfund sites?
EPA assesses the health effects of
radiation by calculating excess cancer risk
posed by radioactive contamination.
Excess cancer risk is the additional
probability that a person exposed to the
contamination will develop cancer over a
lifetime.
EPA considers excess cancer risk to be
any risk above the protective range. The
protective range is a probability that a
person exposed to radioactive and
chemical contaminants will have between
a one in ten thousand and a one in a
million chance of developing cancer,
known as the 10~4 to 10~6 cancer risk
range.
It is important to note that, even in the
protective range, most people will have
less of a chance of developing cancer
than these numbers indicate. EPA uses
assumptions about exposure levels that
are higher than most people's actual
exposure.
EPA may also calculate health risk from
radiation exposure in dose per year,
measured in millirem per year. Some
regulations at Superfund sites are based
on what EPA has calculated to be
acceptable dose limits per year.
What is background radiation?
Radiation is everywhere in our
environment. The average person in the
United States receives a radiation
exposure of approximately 620 millirems
per year from both natural and man-
made sources. For examples of radiation
in our environment, see the chart
"Relative Doses from Radiation Sources"
on page 9. These examples include
cosmic radiation from space, medical
procedures, radiation found naturally in
the soil and water, and indoor radon.
However, at Superfund sites, EPA is
comparing radioactive pollution at the
site with background radiation of the
same radionuclides where the pollution
occurs, such as in the soil and water.
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Some Common Ways to be Exposed to
Radionuclides at Contaminated Sites
Residential Soil Exposure
Breathing in Dust
Particles External $
Exposure
Eating Fruits and
Vegetables
Incidental Soil
ingestion
Agricultural Soil Exposure
Breathing in Dust Eating Fruits and
Particles Consuming Vegetables
Eating Fish, Por*'£°?f'
External Chjck*n> and and M.Ik
Incidental Soil
Exposure
Ingestion
Soil to Ground Water Exposure
Drinking Water
Tap Water Exposure
Breathing in Vapors
Drinking Water
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RELATIVE DOSES FROM RADIATION SOURCES
Millirem Doses
Radon in average home
200 millirem
(annual)
Diagnostic radiology
50 millirem
(annual)
Mammogram
30 millirem
(single procedure)
Cosmic radioactivity
27 millirem
(annual)
Chest x-ray
4 millirem
(single procedure)
Gastrointestinal series
1,400 millirem
(single procedure)
Cosmic radiation living
in Denver
50 millirem
(annua!)
Natural radioactivity
in the body
40 millirem
(annua!)
Terrestrial radioactivity
28 millirem
(annual)
Cosmic radiation living
at sea level
24 millirem (annual)
Living near a nuclear
power station
< 1 millirem on average
(annual)
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What if I want More Information?
If you would like to learn more about
EPA's Superfund program, you may want
to read the document "This is Superfund:
A Community Guide to EPA's Superfund
Program," available online at:
http://www.epa.gov/superfund/commun
itv/todav/pdfs/TIS%20FINAL%209.13.11.
fidf
If you have questions about this
document, you can contact Stuart Walker
of EPA bye-mail at
walker.stuart@epa.gov or by telephone
at (703) 603-8748.
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s^
Superfund Radiation Risk Assessment
Fact Sheet
The Superfund program uses a process called risk assessment to calculate health risks
posed by hazardous contamination and waste. A risk assessment conducted at
Superfund sites with radioactive contamination is divided into four parts:
1. Data Collection and Evaluation
2. Exposure Assessment
3. Toxicity Assessment
4. Risk Characterization
The first three steps allow EPA to answer key questions about the contaminated site:
• What type of radioactive contamination is present?
• Where is the radioactive contamination located?
• How could people be exposed to the contamination?
• What are the potential harmful health effects from the contamination?
• And what are the uncertainties?
All of this information is then incorporated in the risk characterization, which is used to
make a decision about how to clean up the site.
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Step 1: Data Collection and Evaluation
During Data Collection and Evaluation, EPA has to find out how the site became
contaminated and what radionuclides are present. This step is a four-part process.
1. Information Gathering
In the first step, EPA collects
information about the site. Information
can be collected in many ways,
including:
• Looking at old photographs of the site
• Studying maps of the site and
surrounding areas
• Reading documents related to the site
• Interviewing community members
who are knowledgeable about the
site.
By gathering this information, EPA can
gain a better understanding of the
history and geography of the site and
what activities may have taken place
there.
Community Involvement
Community involvement is important in
the EPA risk assessment process. By
engaging the community in the process,
we are able to gain local information
and insight into the site and its history.
This information can allow us to better
understand risks to the public near the
2. Field Survey
Next, EPA uses special equipment to
find areas that may be contaminated.
Hand-held instruments are used for
smaller areas, but larger sites may
require equipment mounted on a van,
tractor, or aircraft.
3. Sample Collection
Samples are collected from
contaminated areas identified in the
field survey. It is important that samples
are collected in the right places so that
no radionuclides are missed. For
example, samples may be collected
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from soil, air, water, fish, and
vegetation in multiple locations.
4. Determining list of radionuclides
Samples collected are then sent to a
laboratory to be analyzed.
The result of all the sampling and
laboratory work is a list of radionuclides
found at the site and the concentration
(or amount) of those radionuclides.
Understanding Background Radiation
Many of the same radionuclides that
contaminate a Superfund site also occur
naturally. As a result, samples are also
collected in uncontaminated areas
surrounding the site. These samples allow
EPA to determine local background
concentrations. Understanding background
concentration allows EPA to decide which
radionuclides will require the most focus
during the investigation.
At this point, it is not known if the levels
of these radioactive contaminants could
be harmful. The next step of the risk
assessment process evaluates whether
the contamination from the site may
pose a risk to human health.
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Step 2: Exposure Assessment
Exposure assessments are used to calculate the amount of exposure to radionuclides
on a site that is likely to occur for people near the site (such as residents, workers, and
visitors). This assessment is important because radiation that cannot reach you
cannot hurt you.
Once it is known which radionuclides are
on the site, their concentrations, and
where they are, calculations are made to
estimate the amount of radiation people
may be exposed to. Many factors are
included in making these calculations,
such as:
• How much air people breathe.
• How much water they drink and use
for other purposes.
• How much time people spend near
the contaminated site. (Someone
who lives near the site, for example,
would have a different exposure level
than someone working at or visiting
the site.)
All of this information is then used to
determine how much contact people
have with the radioactive contamination.
Community Involvement
The public can be exposed to radiation at
Superfund sites through many daily
activities. By working with the public, EPA
can learn how people in the area could
come into contact with the radionuclides
from a Superfund site.
Unique community interaction with the
environment, such as eating wild fish and
game or locally grown foods, is also
considered to account for other potential
routes of exposure.
Now that the types of radionuclides and
the extent of exposure to them have
been determined, the next step is to
understand harmful health effects from
this exposure.
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Step 3: Toxicity Assessment
The toxicity assessment phase answers two key questions: what potential harmful
health effects can the radionuclide cause, and how much exposure to the
radionuclide does it take to pose a significant risk to people?
The toxicity assessment is concerned with
the potential for radionuclides to cause
cancer. All radionuclides can cause cancer
and are assumed to be potentially
harmful even at low doses. The risk of
cancer from radiation increases as the
exposure increases. Uranium
radionuclides are the only radionuclides
where the noncancer effects are also
considered during Superfund site
cleanup.
In estimating the toxicity of a
radionuclide, EPA must take into account
the type of radiation it emits and how the
radiation affects different organs in the
Understanding Radiation Toxicity
At much higher radiation exposures than
would be expected at a Superfund site,
harmful effects can be produced in a
relatively short time. An example of this is
the sickness seen in atomic bomb survivors.
Since exposure at Superfund sites is usually
much lower, EPA focuses primarily on the
cancer risk from exposure to radionuclides.
body. Alpha particles, for example, inflict
about 20 times more damage to living
tissue than beta particles or gamma rays.
In addition, different organs in the body
have different cancer rates even when
exposed to the same level of radiation. As
a result, EPA must consider both whole
body radiation exposure as well as
specific organ exposure for certain
radionuclides.
EPA has developed two methods to
assess the harmful effects of exposure to
specific radionuclides:
• Slope factors provide cancer risk
posed by lifetime exposure to specific
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radionuclides. Slope factors also take
into account the type of exposure
(inhalation, ingestion, or external).
Dose conversion factors (DCFs)
convert concentration of specific
radionuclides (in air, soil, water, or
food) to a radiation dose based on a
person's type of exposure.
EPA uses this information, combined with
the exposure assessment, to calculate
how toxic the radionuclides are at the
Superfund site.
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Step 4: Risk Characterization
Risk characterization is the final phase in a Superfund radiation risk assessment. From
the data collection and evaluation phase, we developed a list of radionuclides, and the
concentrations of those radionuclides, found at the site. We learned from the
exposure assessment phase who is exposed, how they are exposed, and how much of
the radioactive contaminants they are exposed to. And from the toxicity assessment,
we found out how toxic these contaminants could be based on the exposure. During
the risk characterization, we use all of this information to calculate the risk of
potential health effects from exposure to radionuclides at the site.
Health risk is based on the excess risk of
cancer from exposure to radioactive
contamination. This risk is described in
terms of the probability that an exposed
individual will develop cancer over a
lifetime as a result of that exposure.
EPA generally considers excess cancer
risk in the range of 1 out often thousand
people to 1 out of one million people, or
10"4to 10"6, as a protective range for both
chemical and radioactive contaminants. If
a site is contaminated with radionuclides
and cancer-causing chemicals, cancer risk
is combined for both. Most people will
have less chance of getting cancer than
these numbers indicate because EPA uses
assumptions about exposure to
contaminants that are designed to ensure
that everyone at a site is protected,
including vulnerable populations such as
children.
Once the health risks from the site are
understood, the list of radionuclides
found at the site is reviewed and a
determination is made as to which
radionuclides pose a significant risk. This
information, as well as information about
risks to the environment, can now be
used to develop a cleanup plan that will
make the site safe for both current and
future uses, protecting human health and
the environment.
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What if I want More Information?
If you would like to learn more about
EPA's risk assessment process for
radiation at Superfund sites, you may
want to watch the video "Superfund
Radiation Risk Assessment and How You
Can Help: An Overview" available online
at:
http://www.epa.gov/superfund/health7c
ontaminants/radiation/radvideo.htm.
You may also read documents that EPA
has written to help its own staff in
conducting risk assessments for radiation
at Superfund sites. The "Radiation Risk
Assessment at CERCLA Sites: Q & A" is a
good place to start since it provides an
overview for EPA staff of the material
available for them to use. This document
is available online at:
http://www.epa.gOv/superfund/health/c
ontaminants/radiation/pdfs/riskqa-
second.pdf.
If you would like to learn more about
EPA's Superfund program, you may wish
to read "This is Superfund: A Community
Guide to EPA's Superfund Program." This
guide is available online at:
http://www.epa.gov/superfund/commun
itv/todav/pdfs/TIS%20FINAL%209.13.11.
jadf.
If you have questions about this
document, you can contact Stuart Walker
of EPA bye-mail at
walker.stuart@epa.gov or by telephone
at (703) 603-8748.
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Attachment A
Compendium of Information on the
Preliminary Remediation Goal (PRG)
and Dose Compliance Concentration (DCC) Calculators
-------
_,
Primer on PRG and DCC Calculators
What are the Preliminary
Remediation Goal (PRG) and Dose
Compliance Concentration (DCC)
calculators?
The PRG and DCC calculators were
developed to help EPA staff and others
who are assessing radiation at
Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA
or Superfund) sites. The PRG calculators
are used to identify the amount of
radiation that equals the 10"4 to 10"6
cancer risk range that EPA considers
protective. The DCC calculators are used
to determine the amount of radiation
that equals a dose-based regulation that
is measured in millirem per year.
How do the PRG and DCC
calculators work?
The calculators use a series of equations
to estimate radiation concentrations that
EPA considers protective. They include
assumptions about how people live at the
site and the site itself, including the
weather. These assumptions can be
adjusted to more accurately reflect the
situation at your site.
What is an Applicable or Relevant
and Appropriate Requirement
(ARAR)?
An ARAR is an environmental law or
regulation from the federal government
or a state government that addresses
conditions or a particular cleanup
technology at a Superfund site.
All actions to clean up contamination at
Superfund sites must be protective of
human health and the environment and
comply with ARARs, unless a waiver is
justified. ARARs are often the deciding
factor in establishing cleanup levels at
CERCLA sites.
The DCC calculators may be used for
developing cleanup levels if an ARAR is a
dose-based millirem regulation.
What if I want more information?
There are 1-page fact sheets describing
each of the six PRG and DCC calculators.
If you have questions about the PRG or
DCC calculators, you can contact Stuart
Walker of EPA by e-mail at
walker.stuart@epa.gov or by telephone
at (703) 603-8748.
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Preliminary Remediation Goals (PRG) Calculator/**
(I tN^tt/
^/Stuart Walker-walker.stuart@epa.gov, (703)603-8748
•<§/ Office of Superfund Remediation and Technology Innovation, US Environmental Protection Agency
PRG: http://epa-prgs.ornl.gov/radionuclides
What is PRG?
PRG stands for Preliminary
Remediation Goal.
PRGs are the initial cleanup goals at
a Superfund site and usually are
not final cleanup levels.
Used when there is no appropriate
government regulation of cleanup
levels.
PRG Calculator
The PRG Calculator is a tool that allows EPA to calculate initial cleanup
levels for radiation in soil, water, and air at Superfund sites.
Uses slope factors to calculate cleanup levels based on a target cancer
risk of 10'6.
• Slope factors provide cancer risk posed by lifetime exposure to
specific radionuclides. Slope factors also take into account the type
of exposure (inhalation, ingestion, or external) and amount of
exposure. For example, a resident on a site would expect to have a
different exposure level than a worker on the same site.
• Target cancer risk of 10"6 means that a person exposed to the
contamination has a one in a million chance of developing cancer.
(Target is based on highest estimated level of exposure. Most
people will have less of a chance of developing cancer.)
The exposure pathways calculated by the PRG calculator are shown in
the diagrams below.
How does the PRG Calculator Work?
Slope Factors
PRG Equations
^
PRG Calculation
Residential Land Use
Industrial Land Use
Agricultural Land Use
Outdoor (or Composite) Worker: Soil Exposure
Breathing in Dust
Particles
It ft.
Indoor Worker: Soil Exposure
External
Exposure
Incidental Soil
Ingestion
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it
,
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Ireathing in Dust
Particles
A1A-* A A
Breathing in Dust
Particles External
Exposure
Resident: Soil Exposure
Eating Fruits and
Vegetables
Incidental Soil
lestion
Agricultural: Soil Exposure
Breathing in Dust
Particles
External
Exposur
Eating Fish,
Chicken, and
Eggs
Eating Fruits and
Consuming Vegetables
Pork, Beef,
and Milk _^_ incidental Soil
Ingestion
Tapwater Ingestion Exposure
Drinking Water
Fish Ingestion Exposure
Eating Fish
•
-------
Dose Compliance Concentration (DCC) Calculator
- // Stuart Walker - walker.stuart@epa.gov, (703) 603-8748
ox Office of Superfund Remediation and Technology Innovation, US Environmental Protection Agency
DCC: http://epa-dccs.ornl.gov/
What is DCC?
DCC stands for dose compliance
concentrations.
DCCs are cleanup levels that
correspond to a specific dose of
radiation.
Superfund is NOT a dose-based
program.
Soil to Groundwater Exposure
DCC Calculator
• The DCC Calculator is a tool that allows EPA to calculate cleanup levels
in soil, water, and air that correspond to a specific dose of radiation at
a Superfund site. The calculator uses dose conversion factors (DCF) in
calculating radiation dose.
• Dose is the amount of radiation absorbed by a person's body.
• DCFs use concentration of a radionuclide in soil, air, water, and food
to determine the dose of radiation a person at a contaminated site
is exposed to. DCFs also take into account the type of exposure
(inhalation, ingestion, or external) in determining dose.
• Superfund takes into account cancer risk, not radiation dose, in
deciding cleanup levels. The DCC calculator is useful to show
compliance with existing regulation of cleanup levels that may be in
place.
How does the DCC Calculator Work?
Dose Conversion
Factors
DCC Equations
Outdoor (or Composite) Worker: Soil Exposure
Breathing in Dust
Particles
External
Exposure
i i »
iMmjl
Incidental Soil
Ingestion
1-
JMl-a
Indoor Worker: Soil Exposure
DCC Calculation
5 "
*-
Residential Land Use
Industrial Land Use
Agricultural Land Use
... Eating Fruits and
Breathing in Dust .yffffffff. ^.Vegetables
Particles External
Exposure
Drinking Water
Breathing in Vapors
Incidental Soil
estion
Agricultural: Soil Exposure
Fish Ingestion Exposure
External
Exposure
Incidental Soil
Ingestion
Breathing in Dust
Particles
Eating Fruits and
Consuming Vegetables
Pork, Beef,
I Milk ^___ incidental Soil
Ingestion
-------
Building Preliminary Remediation Goals (BPRG) Calculator
'
3 Stuart Walker - walker.stuart@epa.gov, (703) 603-8748
.\y Office of Superfund Remediation and Technology Innovation, US Environmental Protection Agency
BPRG: http://epa-bprg.ornl.gov
What is BPRG?
BPRG stands for Building Preliminary
Remediation Goal.
BPRGs are the initial cleanup goals
for contamination inside of buildings
at a Superfund site and usually are
not final cleanup standards.
Used when there is no appropriate
government regulation of cleanup
levels.
Used for residential and
commercial/industrial indoor worker
exposure.
External
Resident: Contaminated Building
Materials
BPRG Calculator
The BPRG Calculator is a tool that allows EPA to calculate
radiation cleanup levels inside of buildings at Superfund sites.
Uses slope factors to calculate cleanup levels based on a target
cancer risk of 10'6 .
• Slope factors provide cancer risk posed by lifetime exposure
to specific radionuclides. Slope factors also take into account
the type of exposure (inhalation, ingestion, or external) and
the amount of exposure. For example, a resident on a site
would expect to have a different exposure level than a worker
on the same site.
• Target cancer risk of 10~6 means that a person exposed to the
contamination has a one in a million chance of developing
cancer. (Target is based on highest estimated level of
exposure. Most people will have less of a chance of
developing cancer.)
The exposure pathways used by the BPRG calculator are shown
in the diagrams below.
Indoor Worker: Contaminated
Building Materials
External Exposure External Exposure
How does the BPRG Calculator work?
Slope Factors
BPRG Equations
BPRG Calculation
Residential Land Use
Industrial (Indoor
worker)
Resident: Ambient Air
Surrounded by
Radioactive Material
Indoor Worker: Ambient Air
Indoor Worker: Settled Dust
External Exposure Breathing
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External Exposure Ingestion of Dust
-------
Building Dose Compliance Concentration (BDCC) Calculator /£
** x 7
StuartWalker-walker.stuart@epa.gov, (703) 603-8748
Office of Superfund Remediation and Technology Innovation, US Environmental Protection Agency
BDCC: http://epa-bdcc.ornl.gov
What is BDCC?
BDCC stands for building dose
compliance concentrations.
BDCCs are cleanup levels that
correspond to a specific dose of
radiation in radioactively
contaminated buildings.
Superfund is NOT a dose-based
program.
Used for residential and
commercial/industrial indoor worker
exposure.
Resident: Settled Dust
External
BDCC Calculator
The BDCC Calculator is a tool that allows EPA to calculate
cleanup levels that correspond to a specific dose of radiation in
radioactively contaminated buildings at a Superfund site. The
calculator uses dose conversion factors (DCF) in calculating
radiation dose.
• Dose is the amount of radiation absorbed by a person's body.
• DCFs use concentration of a radionuclide in soil, air, water,
and food to determine the dose of radiation a person at a
contaminated site is exposed to. DCFs also take into account
the type of exposure (inhalation, ingestion, or external) in
determining dose.
Superfund takes into account cancer risk, not radiation dose, in
deciding cleanup levels. The DCC calculator is useful to show
compliance with previously existing regulation of cleanup levels
that may be in place.
Below are some exposure pathways considered by the DCC.
How does the BDCC Calculator work?
Dose Conversion
Factors
BDCC Equations
BDCC Calculation
Residential Land Use
Industrial (Indoor
worker)
Surroun
Radioactive Material
Indoor Worker: Contaminated
Building Materials
External Exposure External Exposure
Indoor Worker: Ambient Air
Indoor Worker: Settled Dust
External Exposure Breathing
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External Exposure
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-------
Surface Preliminary Remediation Goals (SPRG) Calculator | A
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. «j StuartWalker-walker.stuart@epa.gov, (703)603-8748
A
-------
Surface Dose Compliance Concentration (SDCC) Calculator
StuartWalker-walker.stuart@epa.gov, (703)603-8748
Office of Superfund Remediation and Technology Innovation, US Environmental Protection Agency
SDCC: http://epa-sdcc.ornl.gov
What is SDCC?
SDCC stands for surface dose
compliance concentrations.
SDCCs are cleanup levels that
correspond to a specific dose of
radiation for radioactive
contamination on hard surfaces.
Superfund is NOT a dose-based
program.
Used for residential, indoor worker,
and outdoor worker exposure.
2D Exposure to Fixed Settled Dust
on Finite Slabs (Outdoor Worker)
Dose Conversion
Factors
SDCC Calculator
The SDCC Calculator is a tool that allows EPA to calculate radiation
cleanup levels that correspond to a specific dose from contaminated,
hard, outside surfaces (streets, sides of buildings.) The calculator uses
dose conversion factors (DCF) in calculating radiation dose.
• Dose is the amount of radiation absorbed by a person's body.
• DCFs use concentration of a radionuclide in soil, air, water, and food to
determine the dose of radiation a person at a contaminated site is
exposed to. DCFs also take into account the type of exposure
(inhalation, ingestion, or external) in determining dose.
Superfund takes into account cancer risk, not radiation dose, in deciding
cleanup levels. The DCC calculator is useful to show compliance with
previously existing regulation of clean-up levels that may be in place.
Below are some exposure pathways considered by the SDCC Calculator.
3D Exposure to Fixed Settled Dust I 3D Exposure to Fixed
on Outdoor Surfaces (Indoor Contaminated Building Materials
Worker) (Outdoor Worker)
SDCC Calculator
SDCC Equations
SDCC Calculation
Industrial Land Use
Residential Land Use
Outdoor Worker
2D Exposure to Fixed
Contaminated Finite Slabs
(Resident)
-------
Attachment B
Compendium of Information on
Radionuclides Commonly Found at Superfund Sites
-------
'%>
\
Xs
Primer on Radionuclides
Commonly Found at Superfund Sites
What is the purpose of these fact
sheets?
The information in these fact sheets is
intended to help the public understand
more about the various radionuclides
commonly found at Superfund sites.
What information is in these fact
sheets?
These fact sheets answer questions such
as:
• How can a person be exposed to
the radionuclide?
• How can it affect human health?
• How does it enter and leave the
body?
• What levels of exposure result in
harmful effects?
• What recommendations has the
U.S. Environmental Protection
Agency (EPA) made to protect
human health from exposure to
radionuclides?
How does EPA calculate risks to
human health from radiation
exposure at Superfund sites?
EPA assesses the health effects of
radiation by calculating excess cancer
risk caused by radioactive
contamination. Excess cancer risk is the
probability that a person exposed to the
contamination will develop cancer over
a lifetime.
EPA considers excess cancer risk to be
any risk above the protective range. The
protective range is a probability that a
person exposed to radioactive and
chemical contaminants will have
between a one in 10,000 and a one in a
million chance of developing cancer,
known as the 10"4 to 10"6 cancer risk
range.
It is important to note that even in the
protective range, most people will have
less of a chance of developing cancer
than these numbers would indicate. The
actual change is lower because EPA uses
assumptions about exposure levels that
are higher than most people's actual
exposure.
-i-
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EPA may also calculate health risk from
exposure to radiation in dose per year,
measured in millirems per year. Some
regulations at Superfund sites are based
on what EPA has calculated to be
acceptable dose limits per year.
What is an Applicable or Relevant
and Appropriate Requirement
(ARAR)?
An ARAR is an environmental law or
regulation from the federal government
or a state government that addresses
conditions or a particular cleanup
technology at a Superfund site.
All actions to clean up contamination at
Superfund sites must be protective of
human health and the environment and
comply with ARARs, unless a waiver is
justified. ARARs are often the deciding
factor in establishing cleanup levels at
Superfund sites.
What radionuclides are listed in
these fact sheets?
The following radionuclides are those
most frequently encountered at EPA
Superfund sites and are described in a
series of EPA fact sheets.
Americium-241
Cesium-137
Cobalt-60
Iodine isotopes
Plutonium isotopes
Radium isotopes
Radon
Strontium-90
Technetium-99
Thorium isotopes
Tritium
Uranium isotopes
What if I want More Information?
If you have questions about the
radionuclides described in this
document, you can contact Stuart
Walker of EPA by e-mail at
walker.stuart@epa.gov or by telephone
at (703) 603-8748.
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?
I
^o
Facts about Americium-241
AV
What is americium-241?
Americium is a man-made radioactive metal. It is
produced in nuclear reactors and during nuclear
weapons tests when plutonium absorbs
neutrons.
Americium occurs in several forms called
isotopes. The most common isotope is
americium-241.
What are the uses of americium-241?
Americium is commonly used in very small
amounts in smoke detectors. It is blended with
the element beryllium and is used as a neutron
source to measure the quantity of water present
in soil, as well as moisture and density for
quality control in highway construction.
Americium is also used as a source of radiation
in medical research and in medical diagnostic
devices.
How does americium-241 change in the
environment?
Americium-241 is introduced into the
environment by the decay of plutonium that is a
contaminant from nuclear weapons production
and testing and potentially by certain types of
nuclear reactors. Americium-241 is an unstable
isotope. Therefore, 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 the stable element
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 required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. The half-life of
americium-241 is about 432 years.
How are people exposed to americium-
241?
Most americium that has been released into the
environment has come from atmospheric
testing of nuclear weapons. Some americium
has also been released through nuclear weapons
production, but this amount is small compared
with the amount released during atmospheric
testing.
Nuclear weapon sites, certain types of nuclear
reactors, and industries that manufacture smoke
detectors are potential sources of exposure to
americium-241. Potential pathways of exposure
include ingestion, inhalation, and external
exposure from gamma radiation.
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How does americium-241 get into the
body?
Americium can enter the body when it is inhaled
or swallowed. When it is inhaled, the amount of
americium that remains in the lungs depends on
the size of the particle and the chemical form of
the americium compound. Some americium
compounds dissolve easily. These compounds
are absorbed through the lungs and enter 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 un-
dissolved material that stays in the body goes to
the bones, where it can remain for decades.
Is there a medical test to determine
exposure to americium-241?
Yes, 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 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.
How can americium-241 affect people's
health?
Americium poses a significant risk if enough is
swallowed or inhaled because americium emits
alpha particles. 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 exposure
may eventually increase a person's chance of
developing cancer, but these cancer effects may
not become apparent for several years.
Americium, however, also can pose a risk from
direct external exposure through gamma ray
emissions.
What recommendations has the U.S.
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 at Superfund
sites (the 10~4 to 10~6 cancer risk range), which
cover all radionuclides including americium-241,
are summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 15 picoCuries per liter (pCi/L) for
total alpha particle activity, excluding radon and
uranium, in drinking water. Americium-241 is
covered under this MCL.
For more information about how EPA addresses
americium-241 at Superfund sites Contact Stuart
Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
-2-
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EPA Facts about Cesium-137
What is cesium-137?
Radioactive cesium-137 is produced
spontaneously when other radioactive
materials, such as uranium and plutonium,
absorb neutrons and undergo fission. Fission is
the process in which the nucleus of a
radionuclide splits into smaller parts. Cesium-
137 is a common radionuclide produced when
nuclear fission 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 in food sterilization, including
wheat, spices, flour, and potatoes. Cesium-137 is
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.
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. The time
required for a radioactive substance to lose 50
percent of its radioactivity by decay is known as
the half-life. Cesium-137 is significant because of
its prevalence, relatively long half life (30 years),
and its potential effects on human health.
Barium-137, the daughter product of cesium-
137 decay, has a half-life of 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, barium-137m, can
pass through the human body, delivering
radiation exposure 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 worldwide.
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 operation of nuclear reactors,
spent fuel reprocessing plants, and nuclear
accidents such as Chernobyl and Fukushima.
Cesium-137 is also a component of low-level
radioactive waste at hospitals, radioactive
source manufacturing, and research facilities.
How does cesium-137 get into the body?
Cesium-137 can enter the body when it is
inhaled, ingested, or absorbed through the skin.
After radioactive cesium is ingested, it is
-1-
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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. 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 taking
blood or fecal samples, then measuring the level
of cesium.
How can cesium-137 affect people's
health?
Based on experimentation with ionizing
radiation and human epidemiology, exposure to
radiation from cesium-137 can cause cancer.
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 in Western Europe
exposed to fallout from the accident at
Chernobyl.
The magnitude of the health risk would depend
on exposure conditions for scenarios involving
nuclear accidents or waste materials, such as:
• Types of radioactivity encountered,
• Nature of exposure, and
• Length of exposure.
What recommendations has the U.S.
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 at Superfund sites (the
10"4 to 10"6 cancer risk range), which cover all
radionuclides including cesium-137, are
summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems 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 millirems per year, is 200
picoCuries per liter (pCi/L). If other radionuclides
that emit beta particles and photon radioactivity
are present in addition to cesuim-137, the sum
of the annual dose from all the radionuclides
cannot exceed 4 millirems/year.
For more information about how EPA addresses
cesium-137 at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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i* • r
B
X^J
EPA Facts about Cobalt-60
What is cobalt-60?
The most common radioactive form of cobalt is
cobalt-60. It 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 source of radiation. Medical use
consists primarily of cancer radiotherapy.
Industrial uses include testing welds and castings
and a large variety of measurement and test
instruments, such as 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 required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. The half-life of cobalt-60
is about 5.3 years.
How are people exposed to cobalt-60?
Most exposure to cobalt-60 takes place
intentionally during medical tests and
treatments. These 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 a 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
-1-
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inhaled and is still in the lungs. Other techniques
that may be used include collecting 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. Health risks increase with
the amount of cobalt-60, duration of exposure,
distance from the source (for external
exposure), and whether the cobalt-60 was
ingested or inhaled.
What recommendations has the U.S.
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 at Superfund sites (the
10"4 to 10"6 cancer risk range), which cover all
radionuclides including cobalt-60, are
summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems 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 that is assumed to
yield 4 millirems per year is 100 picoCuries per
liter (pCi/L). If other radionuclides that emit beta
particles and photon radioactivity are present in
addition to cobalt-60, the sum of the annual
dose from all the radionuclides cannot exceed 4
millirems/year
For more information about how EPA addresses
cobalt-60 at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
-2-
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'^s
EPA Facts about Iodine
A^x
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 is used 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 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 iodine-131 is relatively short,
at 8 days, while the half life of iodine-129 is
much longer, at more than 15 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 testing and the Chernobyl and
Fukushima nuclear power plant accidents;
however, the current level of iodine 131 in the
environment is very low. The reason is that
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 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
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and the rest is 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 after 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 that 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. This health
effect is of particular concern for children and
pregnant women. High doses of iodine are used
to treat thyroid cancer. Lower doses of
radioactive iodine will result in reducing the
activity of the thyroid gland, which in turn will
result in lower hormone production in the gland.
There is a fine balance when treating thyroid
problems with radioactive iodine. These
treatments are administered only when the
benefits outweigh the risks. As with any
radioactive material, there is an incremental
chance that a cancer can result from that
incremental exposure to radioactive materials.
What recommendations has the U.S.
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 at Superfund sites (the
10~4 to 10~6 cancer risk range), which cover all
radionuclides including iodine-131, are
summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems 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 millirems per year, is 3
picoCuries per liter (pCi/L). If other radionuclides
that emit beta particles and photon radioactivity
are present in addition to iodine-131, the sum of
the annual dose from all the radionuclides
cannot exceed 4 millirems/year.
For more information about how EPA addresses
iodine at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation
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EPA Facts about Plutonium
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 source of heat 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 common byproducts of
weapons testing.
Ho w 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. 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; however, internal exposure to
alpha radiation is a concern. 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 required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. Plutonium-238,
plutonium-239, and plutonium-240 are isotopes
of plutonium, and have half-lives of 87 years for
plutonium-238, 24,065 years for plutonium-239,
and 6,537 years for plutonium-240.
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
is very small 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 from these isotopes is
minimal. When mixed in soil on the ground,
these plutonium isotopes pose a potential risk
that is predominantly from inhalation and
ingestion.
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How does plutonium get into the body?
Plutonium can enter the body when it is inhaled
or swallowed. Once it is inhaled, the amount of
plutonium that remains in the lungs depends on
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-241 and 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 these cancer
effects may not become apparent for several
years.
What recommendations has the U.S.
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 at Superfund
sites (the 10~4 to 10~6 cancer risk range), which
cover all radionuclides including plutonium, are
summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 15 picoCuries per liter (pCi/L) for
alpha particle activity, excluding radon and
uranium, in drinking water. Plutonium is covered
under this MCL.
For more information about how EPA addresses
plutonium at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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EPA Facts about Radium
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 1900s, radium was wrongly 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. The
use of radium for these purposes was
discontinued because of the health hazards from
these types of exposures. Radium has also been
widely used in radiation treatment of cancer,
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 lightning 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 particles, 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. The time required for a
radioactive substance to lose 50 percent of its
radioactivity by decay is known as the half-life.
The half lives are 3.5 days for radium-224,1,600
years for radium-226, and 6.7 years for radium-
228, the most common isotopes of radium, 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 continuously
produces radon, which can diffuse into nearby
homes.
An individual can be exposed to radium through
contact with waste from ore at former radium
processing facilities, former radium dial facilities,
or radium dials. In addition, exposure to radium
can occur if radium is released into the air from
burning coal or other fuels, or if drinking water
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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 as a result of 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 percent) will promptly leave
the body in the feces. The other 20 percent 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?
Urinalysis and bone biopsy tests are sometimes
used to determine if individuals have ingested 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 its direct decay product radon.
Radon has been shown to cause lung cancer.
What recommendations has the U.S.
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 at Superfund sites (the
10"4 to 10"6 cancer risk range), which cover all
radionuclides including radium, are summarized
in the fact sheet "Primer on Radionuclides
Commonly Found at Superfund Sites."
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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 cleanup of soil in the top 15 centimeters.
These regulations under 40 Code of Federal
Regulations (CFR) Part 192.12 are often
Applicable or Relevant and Appropriate
Requirements (ARARs) at Superfund sites. The
EPA document "Use of Soil Cleanup Criteria in 40
CFR Part 192 as Remediation Goals for CERCLA
Sites" provides guidance to EPA staff regarding
when the use of 5 picoCuries per gram (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. This document is available online
at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/u mtrcagu.pdf.
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 be an ARAR at
the same site. Criterion 6(6) requires that the
level of radiation, called a "benchmark dose,"
that an individual would receive be estimated
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
document "Remediation Goals for Radioactively
Contaminated CERCLA Sites Using the
Benchmark Dose Cleanup Criterion 10 CFR Part
40 Appendix A, I, Criterion 6(6)" provides
guidance to EPA staff 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 in estimating a benchmark dose. This
document is available online at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/pa rt40.pdf.
EPA has established a Maximum Contaminant
Level (MCL) of 5 picoCuries per liter (pCi/L) for
any combination of radium-226 and radium-228
in drinking water. EPA has also established a
MCL of 15 pCi/L for alpha particle activity,
excluding radon and uranium, in drinking water.
Radium-226 is covered under this MCL.
For more information about how EPA addresses
radium at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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EPA Facts about Radon
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 groundwater 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.)
Ho w does radon change in the
environment?
The primary source of radon is from uranium in
soils and rocks and in groundwater. 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 groundwater
flowing through rock or sand. Radon undergoes
radioactive decay, when 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 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 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 picoCuries per liter [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, more
than 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
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drinking water from groundwater that contains
radon. Radon gas escapes from the water and
goes into the air when water that contains
radon is used in the home for showering,
washing dishes, and cooking. Radon in domestic
water generally contributes only a small
proportion (about 1 to 2 percent) of the total
radon in indoor air. Radon levels in air and
groundwater 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 percent of these
cancer deaths are caused by lung cancer from
inhalation of radon released to indoor air from
the water, and about 11 percent are a result of
cancers of internal organs, mostly stomach
cancers, from ingestion of radon in water.
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What recommendations has the U.S.
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 at Superfund sites (the 10"
4 to 10~6 cancer risk range), which cover all
radionuclides including radon, are summarized
in the fact sheet "Primer on Radionuclides
Commonly Found at Superfund Sites."
EPA has established a limitation to exposure to
radon-222 and radon-220 decay products of less
than 0.02 Working Levels (WL) for uranium mill
tailings sites, where radon poses the major
health threat. These regulations under 40 Code
of Federal Regulations (CFR) Part 192.12(b) are
often Applicable or Relevant and Appropriate
Requirements (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 pCi/L,
EPA's national voluntary action level. EPA and
the Surgeon General also recommend that
schools nationwide be tested for radon.
(Exposure to 5 pCi/L of radon-222, or 7.5 pCi/L
of radon-220, 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, USEPA402-K92-003. For copies, contact
the National Radon Hotline (800) 767-7236 or
EPA's web site
http://www.epa.gov/iaq/pubs/index.html.
There is currently a proposed Maximum
Contaminant Level (MCL) for radon in drinking
water from community water systems using
groundwater. The Safe Drinking Water Act
directs EPA to set both an MCL for radon in
drinking water, as well a higher alternative
maximum contaminant level 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 visit EPA's
web site at
http://water.epa.gov/drink/index.cfm.
For more information about how EPA addresses
radon at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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EPA Facts about Strontium-90
What is strontium-90?
Radioactive strontium-90 is produced when
uranium and plutonium undergo fission. Fission
is the process in which the nucleus of a
radionuclide breaks into smaller parts. 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 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. Additionally, strontium-90 is used in
electron tubes, radioluminescent markers, 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.
The time required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. 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 (such as research reactors
and nuclear power plants).
Accidents involving nuclear reactors such as
Chernobyl and Fukushima have released
strontium into the atmosphere, which ultimately
settles to the earth's surface as fallout.
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Chernobyl contributed the largest worldwide
amount of strontium-90 contamination, and a
substantial portion of the strontium-90 released
was deposited in the former Soviet Republics,
with the rest being spread as fallout worldwide.
How does strontium-90 get into the
body?
Ingestion, usually through swallowing 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 digestive
tract, while the rest is excreted through feces.
Of the portion absorbed, virtually all (99
percent) of the strontium is deposited in the
bones or skeleton.
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 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 of
strontium-90 in air, water, and soil. At higher
exposures, such as those associated with the
Chernobyl accident, the cancer risks may be
elevated. The magnitude of this health risk
would depend on exposure conditions, such as
the amount ingested.
What recommendations has the U.S.
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 at Superfund
sites (the 10"4 to 10"6 cancer risk range), which
cover all radionuclides including strontium-90,
are summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems per year for beta
particle and photon radioactivity from man-
made radionuclides in drinking water. The
average concentration of strontium-90 that is
assumed to yield 4 millirems per year is 8
picoCuries per liter (pCi/L). If other radionuclides
that emit beta particles and photon radioactivity
are present in addition to strontium-90, the sum
of the annual dose from all the radionuclides
cannot exceed 4 millirems/year.
For more information about how EPA addresses
strontium-90 at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
-2-
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<\£D Srxi^S.
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EPA Facts about Technetium-99
<&,
l/l//)ot is technetium-99?
Technetium-99 (Tc-99) is a radioactive metal.
Most technetium-99 is produced artificially, but
some also occurs naturally in very small
amounts in the earth's crust. Technetium-99
was first obtained from the element
molybdenum, but it 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 technetium-99 and technetium-99m.
In addition to being produced during nuclear
reactor operation, technetium-99 is produced in
atmospheric nuclear weapons tests. Metastable
technetium-99 (technetium-99m), the shorter-
lived form of technetium-99, is also a
component of gaseous and liquid effluent from
nuclear reactors. Technetium-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?
Technetium-99 is an excellent superconductor at
very low temperatures. In addition, technetium-
99 has anti-corrosive properties. Five parts of
technetium per million will protect carbon steels
from corrosion at room temperature.
Technetium-99m is used in medical therapy in
brain, bone, liver, spleen, kidney, and thyroid
scanning and for blood flow studies.
Technetium-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
technetium-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 is 210,000 years for
technetium-99 and 6 hours for technetium-99m.
How are people exposed to technetium-
99?
Man-made technetium-99 has been found in
isolated locations at federal sites in the
groundwater beneath uranium processing
facilities. Technetium-99 contamination at these
selected sites is a concern if individuals are
exposed to technetium-99 by drinking
contaminated water and ingesting contaminated
plants. The potential exposure from external
radiation by technetium-99 is minimal because
the isotope is a weak beta emitter. Technetium-
99m is not a concern at these sites because of its
short half-life. Technetium-99 is also found in
the radioactive waste of nuclear reactors, fuel
cycle facilities, and hospitals.
In the natural environment, technetium-99 is
found at very low concentrations in air, sea
water, soils, plants, and animals. The behavior of
technetium-99 in soils depends on many factors.
Organic matter in soils and sediments plays a
significant role in controlling the mobility of
-1-
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technetium-99. In soils rich in organic matter,
technetium-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 technetium-99. Technetium-99 can
also transfer from seawater to animals.
How does technetium-99 get into the
body?
At radioactively contaminated sites with
technetium-99 contamination, the primary
routes of exposure to an individual are from the
potential use of contaminated drinking water
and ingestion of contaminated plants. Exposure
may occur to persons working in research
laboratories that conduct experiments using
technetium-99 and technetium-99m. Patients
undergoing diagnostic procedures may receive
controlled amounts of technetium-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 technetium-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 administered soon after exposure.
The tests require special equipment and cannot
be done in a doctor's office.
How can technetium-99 affect people's
health?
Once in the human body, technetium-99
concentrates in the thyroid gland and the
gastrointestinal tract. The body, however,
constantly excretes technetium-99 once it is
ingested. As with any other radioactive material,
there is an increased chance that cancer or
other adverse health effects can result from
exposure to radiation.
What recommendations has the U.S.
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 at Superfund
sites (the 10~4 to 10~6 cancer risk range), which
cover all radionuclides including technetium-99,
are summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems per year for beta
particle and photon radioactivity from man-
made radionuclides in drinking water.
Technetium-99 is covered under this MCL. The
average concentration of technetium-99 that is
assumed to yield 4 millirems per year is 900
picoCuries per liter (pCi/L). If other radionuclides
that emit beta particles and photon radioactivity
are present in addition to technetium-99, the
sum of the annual dose from all the
radionuclides cannot exceed 4 millirems/year.
For more information about how EPA addresses
technetium-99 at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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EPA Facts about Thorium
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 that 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 naturally 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 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 thorium-
232 is very long at about 14 billion years. As a
result of 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-232 is
typically present with its decay product radium-
224, which will produce radon-220 gas, also
known as thoron, and its decay products that
result in lung exposure. Thorium-230 is part of
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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-226 decay
products, lung exposure from radon-222 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
administered within a short period of time after
exposure. They require special equipment and
cannot be done in a doctor's office.
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 to take special
X-rays. Bone cancer is also a potential health
effect through the storage of thorium in the
bone.
What recommendations has the U.S.
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
thorium. General recommendations EPA has
made to protect human health at Superfund
sites (the 10~4 to 10~6 cancer risk range), which
cover all radionuclides including thorium, are
summarized in the fact sheet "Primer on
Radionuclides Commonly Found 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
cleanup of the top 15 centimeters of soil. Since
thorium decays into radium, these regulations
for radium under 40 Code of Federal Regulations
(CFR) Part 192.12 have often been used as
Applicable or Relevant and Appropriate
Requirements (ARARs) at Superfund sites for
thorium-contaminated soil. The EPA document
"Use of Soil Cleanup Criteria in 40 CFR Part 192
as Remediation Goals for CERCLA Sites" provides
guidance to EPA staff regarding when 5 pCi/g of
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thorium is an ARAR or otherwise recommended
cleanup level for any 15 centimeters of
subsurface soil contaminated by thorium other
than the first 15 centimeters. This document is
available online at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/u mtrcagu.pdf.
If regulations under 40 CFR Part 192.12 are an
ARAR for radium in soil at a Superfund site, then
Nuclear Regulatory Commission (NRC)
regulations for uranium mill tailing sites under
10 CFR Part 40 Appendix A, I, Criterion 6(6), may
be an ARAR at the same site.
Criterion 6(6) requires that the level of radiation,
called a "benchmark dose," that an individual
would receive be estimated 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 document
"Remediating Goals for Radioactively
Contaminated CERCLA Sites Using the
Benchmark Dose Cleanup Criterion 10 CFR Part
40 Appendix A, I, 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. This document is
available online at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/part40.pdf.
EPA has established a Maximum Contaminant
Level (MCL) of 15 picoCuries per liter (pCi/L) for
alpha particle activity, excluding radon and
uranium, in drinking water. Thorium is covered
under this MCL.
-3
For more information about how EPA addresses
thorium at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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EPA Facts about Tritium
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 (such as EXIT signs). Tritium is used
as a tracer for biochemical research, animal
metabolism studies, and groundwater 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. As a result, 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 complex and slow.
The time required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. 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 that
generate electricity. Other sources of tritium
include government plants that have
reprocessed reactor fuels. Individuals can also
be exposed to tritium via 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, the risk to the average person from
tritium is typically not significant since current
world-wide levels of tritium in the environment
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from man-made and natural sources are low.
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 depends 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.
How can tritium affect people's health?
With respect to chemical reactions, tritium
reacts similarly to ordinary hydrogen. Therefore,
tritium dilutes through the body as ordinary
water. Tritium concentration in soft tissue and
the associated dose to these tissues is generally
uniform and depends on the water content of
the tissue. Tritium is rapidly cleared from tissues
because the water content in the body turns
over frequently.
What recommendations has the U.S.
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 at Superfund sites (the
10~4 to 10~6 cancer risk range), which cover all
radionuclides including tritium, are summarized
in the fact sheet "Primer on Radionuclides
Commonly Found at Superfund Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 4 millirems per year for beta
particle and photon radioactivity from man-
made radionuclides in drinking water. The
average concentration of tritium that is assumed
to yield 4 millirems per year is 20,000 picoCuries
(pCi/L). If other radionuclides that emit beta
particles and photon radioactivity are present in
addition to tritium, the sum of the annual dose
from all the radionuclides cannot exceed 4
millirems/year.
For more information about how EPA addresses
tritium at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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sfe
V
q^
EPA Facts about Uranium
l/l//)ot 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, and radon-222. See
"EPA Facts 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 time required for a radioactive substance to
lose 50 percent of its radioactivity by decay is
known as the half-life. 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.
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Uranium ore contains all the daughter elements
of uranium-238 and uranium-235, but the
uranium-238, uranium-234, and uranium-235
are extracted and chemically separated during
processing. 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
cleanup of these sites. Potential individual
exposure at these sites may be from different
pathways, but the groundwater pathway is of
particular concern because of the mobility of
uranium.
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.
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 noncancer 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 depends on the level of uranium
concentration.
What recommendations has the U.S.
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
uranium. General recommendations EPA has
made to protect human health at Superfund
sites (the 10~4 to 10~6 cancer risk range), which
cover all radionuclides including uranium, are
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summarized in the fact sheet "Primer on
Radionuclides Commonly Found at Superfund
Sites."
EPA has established a Maximum Contaminant
Level (MCL) of 30 micrograms per liter (jag/liter)
for uranium in drinking water. For uranium mill
tailing sites, EPA has established 30 picoCuries
per liter (pCi/L) for uranium-234 and -238 as
standards for protecting groundwater. The EPA
document "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
Applicable or Relevant and Appropriate
Requirement (ARAR) at Superfund sites. This
document is available online at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/9283 1 14.pdf.
Also 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. These
regulations under 40 Code of Federal
Regulations (CFR) Part 192.12 are often ARARs
at Superfund sites. The EPA document "Use of
Soil Cleanup Criteria in 40 CFR Part 192 as
Remediation Goals for CERCLA Sites" provides
guidance to EPA staff regarding when 5 pCi/g is
an ARAR or otherwise recommended cleanup
level for any 15 centimeters of subsurface soil
contaminated by radium other than the first 15
centimeters. This document is available online
at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/u mtrcagu.pdf.
If regulations under 40 CFR Part 192.12 are an
ARAR for radium in soil at a Superfund site, then
Nuclear Regulatory Commission (NRC)
regulations for uranium mill tailing sites under
10 CFR Part 40 Appendix A, I, Criterion 6(6), may
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 the level of radiation,
called a "benchmark dose," that an individual
would receive be estimated 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 could be exposed to from all
radionuclides, except radon, in both the soil and
buildings at the site. The EPA document
"Remediating Goals for Radioactively
Contaminated CERCLA Sites Using the
Benchmark Dose Cleanup Criterion 10 CFR Part
40 Appendix A, I, 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. This document is
available online at:
http://www.epa.gov/superfund/health/contami
nants/radiation/pdfs/pa rt40.pdf.
For more information about how EPA addresses
uranium at Superfund sites
Contact Stuart Walker of EPA:
(703) 603-8748 or walker.stuart@epa.gov,
or visit EPA's Superfund Radiation Webpage:
http://www.epa.gov/superfund/resources/radiation/
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