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Basic Information
Radiation can come from both natural and man-made sources. It is all around us and has been since the earth formed. It is, quite simply, part of our lives. RadTown USA is a virtual community showing a wide variety of radiation sources and uses as you may encounter them in everyday life. This page provides an overview of radiation and RadTown USA--its contents and how the information is organized.
On this page:
- What is Radiation?
- What is RadTown USA?
- How does radiation enter the environment?
- How is radiation used in communities?
- How are people exposed to radiation?
- Which sources should people be most concerned about? How can people avoid them?
- Who is protecting you
- How you can protect yourself
- Resources (how you can learn more)
What is Radiation?
It comes from outer space, the ground, and even from within our own bodies. Radiation is all around us and has been present since the birth of this planet. Radiation simply is part of our daily lives. The word, “radiation,” generally brings to mind nuclear power plants, nuclear weapons, or medical diagnostics and treatments. Nonetheless, we routinely encounter a variety of radiation sources every day, for example, smoke detectors, household appliances, electrical power lines, and even the sun.
Radiation is energy that travels in the form of waves or high speed particles and it makes up the electromagnetic spectrum. The electromagnetic spectrum is divided into two major categories: ionizing radiation and non-ionizing radiation. Ionizing radiation has enough energy to break chemical bonds in molecules or remove tightly bound electrons from atoms, thus creating charged molecules or atoms (ions). There are three major types of ionizing radiation: gamma rays and x-rays, alpha particles, and beta particles. Non-ionizing radiation has enough energy to move around the atoms in a molecule or cause them to vibrate, but not enough to remove electrons.
To learn more about ionizing and non-ionizing radiation go to our Understanding Radiation pages. Start with Radiation and Radioactivity.
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What is RadTown USA?
RadTown USA is a virtual community with a wide variety of radiation sources. We created RadTown to help you learn about the sources of radiation potentially found in a typical community — from radon in homes to a laser light show in a sports arena to radiation therapy in a hospital.
How does radiation enter the environment?
Remember
The RadTown Fact Sheets provide information on specific sources of radiation within communities and any potential for them to enter the environment.Radiation in our environment comes from both natural and man-made sources. In addition, mining and other commercial activities can disturb naturally-occurring radioactive materials by uncovering them. This can lead to direct exposure of individuals from radioactivity in the soil or to weathering which may release radioactive soils to the environment as air- and/or water-borne radioactivity. Ore processing activities also can concentrate naturally-occurring radioactive materials.
Naturally-Occurring Radionuclides
Naturally-occurring radionuclides originate from radioactivity in the Earth's crust and from the action of cosmic radiation on stable atoms (primarily) in the Earth's atmosphere:
- Many of the radionuclides in the Earth's crust were
formed along with Earth itself and have half-lives measured in billions of years. As a result, they are present in
essentially the same amount as they were when Earth
was formed. These radionuclides are known as "primordial
radionuclides.
(Many more naturally-occurring radionuclides than now exist were produced when the universe was formed several billion years ago, but most of them have decayed away.) - Radionuclides are continuously produced by the bombardment of stable atoms by cosmic rays, largely in the atmosphere. These are known as "cosmogenic radionuclides.
Man-Made Radionuclides
Since the discovery of naturally-occurring radioactive materials in 1896 and the first human-engineered release of energy from the atomic nucleus in 1939, scientists and engineers have developed a wide variety of applications for radioactive materials. In addition, research has led to the discovery and creation of additional radioactive elements. This widening manufacture and use of radioactive elements has led to environmental contamination, particularly during the period before the health and environmental effects of radiation were clearly understood and protective regulations put in place.
Man-made radioactivity in the environment comes from a variety of sources:
- Atmospheric testing of nuclear weapons during the 1950's and 1960's was once a major source of man-made radiation in the environment. Many of the radionuclides with shorter half-lives, such as strontium m-90 have now largely decayed away. Slowly decaying radionuclides such as americium-241 remain. (However, the result of their slow decay(long half-life) is that they give off very little radiation.)
- Facilities that produce weapons and manufacture items that use radioactive sources may release small quantities of radionuclides to the environment (Nuclear Regulatory Commission regulations allow small amounts of certain radionuclides to be released into the air or flushed down drains as liquids).
- "Orphan" sources are radioactive sources that have fallen out of regulatory control. Depending on their form, the pose different threats. Some can be broken with the resulting release of radioactive materials to the atmosphere. Some could expose people who are unfamiliar with sources, and inadvertently handle them. Others could be incorporated into scrap metal shipments and contaminate entire batches of metal when melted in a steel mill. Orphan sources also are potential components of improvised nuclear devices (dirty bombs).
- When items such as household smoke detectors containing americium-241 and exit signs containing tritium are discarded as ordinary trash, they go directly to municipal landfills, where the radionuclides they contain may enter ground water and be carried into the rest of the environment.
- Accidental releases such as the Chernobyl accident in the Ukraine release radionuclides to the environment.
- Improperly disposed medical waste also can be a source of radionuclides in the environment.
How is radiation used in communities?
Radiation has many uses. In fact, there are sources of radiation in virtually all communities. Here are a few of the many examples of radiation sources used in commercial applications, research, medical, and consumer products:
- Industrial particle accelerators are used in commercial applications such as the creation of ceramics, insulators, metals and plastics.
- Research facilities use radioactive materials in the development
of new products and in scientific studies.
- Medical - developing new cancer treatments.
- Agricultural - insect control, developing disease-resistant plants, and the production of fertilizers.
- Geology - to determine the age of rock formations and to study continental drift using naturally-occurring radionuclides in the soil and rock.
- Archaeology - carbon dating of artifacts, using the naturally-occurring radioactive element Carbon-14
- For many diseases, nuclear medicine is the most reliable method
to make diagnoses and determine appropriate treatments.
- Mammograms, CT Scans, MRIs, and other medical x-rays
- Radio pharmaceuticals and radioisotopes for diagnosing and treating cancer
- Many consumer products are treated with or contain radioactive
materials:
- Food irradiation
- Smoke detectors
- Sun lamps and tanning equipment
How are people exposed to radiation?
The answer to this question in large part depends on the specifics of an individual’s life. Our bodies are well adapted to some degree of exposure; humans evolved in the presence of radiation and have well developed mechanisms for repairing cell damage from it.
Knowing the annual dose received by an "average" person provides some perspective. The most recent data on the average annual dose in the U.S. come from a 1987 study by the National Commission on Radiation Protection and Measurement. At the time of the study, people in the U.S. received an average annual radiation dose of about 360 milli rem (one thousandth of a rem) per year.
This Pie Chart shows the relative contribution of various sources to the average annual dose.
Background Radiation
Most (82 percent) of the average annual dose in the 1987 study originated from "background" radiation. "Background" radiation includes naturally-occurring radiation:
- Radon in soil and water 55%
- Cosmic radiation 8%
- Terrestrial radiation from minerals such as uranium and radium in rock and soil 8%
- Radionuclides, primarily potassium-40, in living tissue 11%
The average is calculated from a range of doses that depend in part on where people live. Background levels in a particular geographic region depend on multiple factors:
- altitude (cosmic radiation increases with altitude)
- the content of soils (some areas have higher natural levels radon gas)
- local geology (e.g., geologic deposits of uranium and other radioactive elements)
Radiation from Man-Made Sources
The remaining 18% of the average annual dose was found to come from man-made sources:
- Medical x-rays, 11%
- Nuclear medicine 4%
- Consumer products 3%
- Other <1%
- Occupational 0.3%
- Fallout <0.3%
- Nuclear fuel cycle 0.1%
- Miscellaneous 0.1%
The average included individual variations related to several factors:
- exposure from medical procedures (e.g. x-rays, nuclear medicine), which accounted for the majority of man-made exposure
- occupation (e.g. uranium miners' greater exposure to radon, uranium, and other radionuclides)
- use of consumer products (e.g., smokers' inhalation of the radionuclides that tobacco leaves, radium watches, ceramics).
- other man-made factors (e.g., fallout from nuclear testing, proximity to abandoned uranium mines or areas contaminated by radioactive materials from manufacturing)
New NCRP Study
Since the completion of the NCRP studies in 1987, new medical technologies such as CT scans and MRIs have been developed and become widely used. Also, awareness, testing, and remediation of radon in homes and other buildings has increased. Because of these changes, the proportion of the U.S. population exposure represented by these two categories of sources has likely shifted. Current studies being conducted by the NCRP will show the degree of the shift.
NCRP is currently updating the study to account for a number of factors:
- increased use of medical procedures involving radiation (e.g., CT scans and MRIs)
- increased awareness and remediation of radon in homes, schools, and other buildings
- decay of radionuclides from nuclear weapons testing which ended in the 1970s
- atmospheric changes.
Which sources should people be most concerned about? How can people avoid them?
An individual’s level of exposure depends on factors both in and out of their control, so there isn't’t a precise, one-size-fits-all ranking of radiation hazards. There is no exposure that doesn't pose some risk, but the range of risk is very wide. The sources listed below do not represent all potential sources of exposure. They are presented to provide some sense of relative risk--to illustrate that there are extremes and there are opportunities to make choices.
Rare and Deadly
These sources are extreme and would result in radiation sickness and death within weeks, if not immediately. But these scary events are highly unlikely in the course of average people's lives:
- contact with a spent fuel rod (unused rods give off little radiation)
- involvement in a nuclear accident, working in the immediate area of a meltdown such as Chernobyl (an outdated reactor design not used in the U.S.)
- being in the impact zone of a nuclear bomb
Unlikely, but Dangerous
There are other, somewhat more common, sources that could result in serious exposure. People would generally not encounter them on a daily basis, but they are common enough that people should be aware of them:
- abandoned ("orphan") sealed radioactive sources. There have been numerous documented cases of individuals finding and keeping or even opening sealed sources from abandoned medical equipment or industrial gauges. (What do these look like?) Workers in the scrap metal industry are the most likely to encounter these since they are generally enclosed in metal shielding.
Common, Serious, Largely Avoidable
The most common source of potential, significant exposure is radon gas. Radon is a colorless, odorless, naturally occurring radionuclide that exists in soils and seeps into the air. It is a decay product of radium. If a house is built on soil that contains radon, it can seep into the house through cracks in the foundation or slab and accumulate in basements and lower floors. Inhaling it results in the release of high-energy particles directly to the lungs and surrounding tissues. It is a leading cause of lung cancer.
Because the concentration of radium that generates radon is highly variable in soils, so is the concentration of radon—two houses side by side can have vastly different levels. Buildings can be made safe, and all should be tested and remediated if necessary. (See Radon in Homes and Buildings.)
Optional, Significant Exposure
Avoidable Known Carcinogens
Smoking and overexposure to UV radiation (sun exposure and tanning equipment) have proven links to two types of cancer with high mortality rates: smoking to lung cancer and UV exposure to melanoma, particularly if exposure is received in childhood.
Benefits and Risks Must be Weighed, Track Exposure
Medical x-rays and nuclear medicine accounted for 15 percent of the average exposure in the 1987 NCRP study. New technologies and increased use of existing technologies have increased that percentage since then. This is a gray area in which risk and benefit must be weighed by individuals and their doctors.
Potential Carcinogens, Link Suspected but Unconfirmed
Exposure to radio frequency (RF) radiation has climbed rapidly with the advent of cell phones and other wireless technologies. Studies of the link between exposure to RF and to electric and magnetic frequency (EMF) radiation have found RF and EMF to be "potential carcinogens," but the data linking RF and EMF to cancer is not conclusive. World wide, health physicists (scientists who study the biological effects of radiation) continue to study the issue.
Avoidable, Risk
Flying takes passengers and crew to higher elevations where their exposure to cosmic radiation is increased. The exposure increases with frequency of flying and the accumulated.
Unavoidable, Low Risk
The human body is born with potassium-40 in its tissues and it is the most common radionuclide in human tissues and in food. We evolved in the presence of potassium-40 and our bodies have well-developed repair mechanisms to respond to its effects. The concentration of potassium-40 in the human body is constant and not affected by concentrations in the environment.
Who is protecting you
The responsibility for protecting the public from radiation is distributed among several federal agencies and the state governments. There are three federal agencies with primary responsibility for protecting people and the environment from harmful exposure to radiation: the Environmental Protection Agency, the Nuclear Regulatory Commission, and the Department of Energy.
| U.S. Environmental Protection Agency EPA primarily sets protective standards (limits) on exposure to radiation that other federal agencies and the states use in developing radiation protection regulations. |
| U.S. Nuclear Regulatory Commission NRC regulates civilian nuclear power and licenses the use of radioactive materials. |
| U.S. Department of Energy DOE oversees the production and management of nuclear weapons and is in charge of cleaning up federal lands contaminated with weapons-related radioactive contamination. DOE also manages national laboratories that conduct nuclear research. |
Other federal agencies have specific and important roles. For example:
| U.S. Food and Drug Administration, Center for Devices and
Radiological Health FDA's CDRH regulates the manufacture of radiation emitting devices, such as cell phones, x-ray machines, and medical devices. |
| U.S. Department of Transportation, Office
of Hazardous Materials Safety DOT's OHMS develops the national safety program that minimizes the risk to life and property inherent in commercial transportation of hazardous materials. |
| U.S. Federal Communications Commission The FCC regulates all nongovernmental sources of radiofrequency radiation including radar and radiofrequency transmitters. |
| U.S. Department of Homeland Security DHS focuses on preparedness, prevention, and response related to radiological emergencies and preventing the entry of radioactive materials through our ports. |
In addition, each state has its own radiation control program. Many have been delegated federal authority for state implementation of federal programs.
Each RadTown fact sheet provides an overview of the federal, state, and international organizations that protect people and the environment from unnecessary exposure to radiation.
How you can protect yourself
Three basic concepts apply to protecting yourself and your family from all types of ionizing radiation: time, distance, and shielding.
Basic Concepts of Radiation Protection
time 
shielding
distance
- Time: The amount of radiation exposure increases as the time spent near the source of radiation increases.
- Distance: The farther away people are from a radiation source, the less their exposure
- Shielding: The greater the thickness and density of shielding around a radiation source, the smaller the exposure.
Remember
RadTown Fact Sheets provide information on avoiding unnecessary exposure to radiation from particular sources of radiation that may be present in the community.Resources (how you can learn more)
Understanding
Radiation
10 October 2007, U.S. Environmental Protection Agency
This section of EPA's Radiation Protection Web site explains the basics of radiation, health effects, and radiation protection.
Radiation Protection
10 October 2007, U.S. Environmental Protection Agency
This Web site describes EPA's radiation protection activities and provides topical and reference information related to radiation protection.
Each RadTown fact sheet also provides links and descriptions of resources where you can find more in-depth information about specific sources of radiation potentially found in the community.