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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.

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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.

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How does radiation enter the environment?

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:

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:

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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:

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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:

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:

Radiation from Man-Made Sources

The remaining 18% of the average annual dose was found to come from man-made sources:

The average included individual variations related to several factors:

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:

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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:

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:

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.

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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.

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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

RadTown Fact Sheets provide information on avoiding unnecessary exposure to radiation from particular sources of radiation that may be present in the community.

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Resources (how you can learn more)

Understanding Radiation
March 2009. U.S. Environmental Protection Agency, Radiation Protection
This web site explains the basics of radiation and radioactivity, health effects, and radiation protection.

Radiation Protection
February 2009. U.S. Environmental Protection Agency
This web site describes the Environmental Protection Agency's 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.

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