Radionuclides in Ecosystems
Radioactive elements are part of our ecosystem, part of the air we breathe, the water we drink and the food we
eat.
Radionuclides can occur naturally, or can be man-made.
Over half of the average annual radiation exposure of people in the U.S. comes from natural sources.
About Radionuclides in Ecosystems
An ecosystem is a place with a one-of-a-kind combination of air, water and land. An ecosystem has habitats
that support plant and animal life. Ecosystem science focuses on all parts of the system, including the
interaction among the water, air, land, plants, humans and other animals. Ecosystem science can tell us how
minerals and other chemicals in nature (including radionuclides) move through Earth's different natural
systems.
Radionuclides enter an ecosystem in three ways:
As minerals present in Earth's original crust.
As radionuclides created by cosmic rays hitting atoms in Earth's atmosphere.
From human activity.
RADIONUCLIDES IN EARTH'S CRUST
Some radionuclides have been present in rocks since the formation of Earth. Others are their decay products.
Examples of these natural radionuclides include potassium-40, rubidium-87, uranium and thorium and decay
products, such as radium and radon.
These radionuclides end up naturally in soil, water and air. Rocks containing them are broken down into soil by
the weather, bacteria and fungi. When radionuclides are in soil particles, they can be blown around by wind.
Some will dissolve in water and end up in surface or ground water. Some radionuclides dissolve more easily
than others. Also, the makeup of the water affects how much of the radionuclide will dissolve.
More than half of the average annual radiation exposure of people in the U.S. comes from natural sources. The
natural radionuclide, radon', is the single biggest natural source of exposure. It comes from the breakdown of
radium. Breathing indoor air containing radon is the most common exposure route.
Radon is one radionuclide that dissolves easily in water. Radon concentration in water is usually low enough
that they are not a serious health threat. You can learn more about radium and radon in water on EPA's Radon
in Drinking Water" webpage.
RADIATION FROM SPACE
Cosmic rays come from stars, our sun, other stars and exploding stars. The rays continuously strike atoms in
Earth's atmosphere. The atmosphere stops most of the cosmic rays, however, the collisions leave some atoms
unstable (radioactive). These radioactive atoms are called cosmogenic radionuclides. They are rare, but some
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of them do reach Earth's surface and settle on the soil and water. Cosmic radiation is the main source of
carbon-14, which is used to date ancient artifacts.
RADIONUCLIDES FROM HUMAN USES OF RADIOACTIVE MATERIAL
Nature is the major source or of radionuclides in an ecosystem. Much smaller amounts of radionuclides come
from sources developed by humans. Examples include uranium mines, nuclear power plants and research
facilities that use radionuclides. However, for most people the annual exposure from these sources is very low.
Only in certain areas where there are open uranium and other mineral mines and mining wastes present is
there a serious health hazard.
Nuclear Weapons Testing: Mostly in the 1950s and 1960's, nuclear weapons tests released large
amounts of radionuclides that spread and remained in ecosystems until the radionuclides decayed
away. The last nuclear weapons test occurred in 1980, and most of the radionuclides, such as
strontium-90, have decayed away. Today, nuclear events include nuclear accidents and potentially
terrorist acts.
Nuclear Facility Releases: The small amounts of airborne radionuclides released from facilities that
handle and process radioactive materials can get into the soil, water or air. The facilities operating
permits allow only very small releases because they result in very small exposures.
Radioactive Waste: Improper disposal of radioactive waste is another way radionuclides can enter an
ecosystem. For example, water seeping thorough mining wastes can dissolve some radionuclides and
carry them into the water system. Public water systems are monitored carefully to make sure the
drinking water is safe. This kind of waste accounts for less than a tenth of one percent of the average
annual radiation exposure of Americans.
You can learn more about all of the different sources of radiation exposure at EPA's RadTown website'".
Rules and Guidance
U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA)
EPA's RadNetiv monitoring system is a national network of monitoring stations that regularly collect air,
precipitation, drinking water, and milk samples for analysis of radioactivity. EPA also develops standards for
disposal of nuclear waste and in some cases, oversees the disposal of radioactive material. EPA's National
Emissions Standards for Hazardous Air Pollutants for Radionuclides (RadNESHAPs)v sets regulatory limits for
radionuclide emissions from industrial sources.
U.S. DEPARTMENT OF AGRICULTURE (USDA)
USDA works with the U.S. Geological Service and U.S. Fish and Wildlife Service to ensure that radioactive
materials are disposed in places that prevent the radioactive material from ever entering the food chain.
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES (HHS), U.S. FOOD AND DRUG
ADMINISTRATION (FDA)
FDA monitors naturally occurring and man-made radionuclides in food as part of its Total Diet Studiesvi. FDA
establishes guidelines for preventing and addressing potentially contaminated crops and livestock during a
radiological emergency.
U.S. DEPARTMENT OF ENERGY (DOE)
DOE's Department of Environmental Management issues regulations related to spills, releases, and cleanup of
radiation in the soil on and around DOE facilities. DOE requires its facilities to limit how much radiation may be
released based on EPA's standards, and it ensures that all facility operators comply with these standards.
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THE STATES
The States have different programs relating to the protection of soil, crops and livestock. States apply EPA's
Protective Action Guides in the event of a radiological emergency. Some states have created more stringent
standards for disposal of radioactive material than the federal limits established by EPA.
What you can do
In most cases no special precautions are necessary.
If you use water from a private well, you should get your water tested for radionuclides.
It's important to test your home for radon. Testing at home is easy. There are many kinds of low-cost radon
test kits available by phone, online and in many stores. If you prefer, you can hire a professional to do the
testing. For more information about radon, its risk and what you can do to protect yourself, visit EPA's Radon
Website.
In a radiological emergency where food contamination may be an issue, listen for advisories from federal, state
or local public health officials. Common food handling safety actions can be taken to reduce the amount of
radioactive contamination in or on food such as washing, brushing or peeling the surface of the fruits or
vegetables.
Where to learn more
You can learn more about radionuclides in ecosystems by visiting the resources available on the following
webpage: http://www.epa.gov/radtown/ecosystems.htmltflearn-more.
' http://www.epa.gov/radon/
" http://www.epa.gov/radon/rnwater.html
"' http://www/epa.gov/radtown
iv http://www.epa.gov/radnet/
v http://www.epa.gov/radiation/neshaps/
vi http://www.fda.gov/Food/FoodScienceResearch/TotalDietStudy/default.htm
vii http://www.epa.gov/radon/
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