Thursday, September 20, 2012

Natural Radiation Sources & Man made.

Sources of Radiation Exposure | Radiation Protection | US EPA

Jump to main content.

Sources of Radiation Exposure

RadTown USA Image

RadTown USA

Explore an interactive, virtual community of houses, schools, laser light shows, construction equipment, flying planes, and moving trains. Each place in RadTown helps you learn about radiation sources or radiation- treated items you might find there.

Though you may have never been aware of it, radiation is, and always has been, all around us. Natural, “background” radiation has been with us since the birth of the universe. Today modern medical procedures utilize various types of radiation to save lives and heal patients. This page provides information on the most common sources of radiation exposure.

Get e-mail updates when this information changes.

On this page:

Radiation is a Fact of Life image

Radiation is a Fact of Life

A slide show on radiation sources from the International Atomic Energy Association (IAEA)

Natural Radiation Sources


You cannot see it, smell it, or taste it, but radon is the leading source of natural radiation exposure and the second leading cause of lung cancer. Where does it come from? Well, usually from soil, but it is found everywhere. The ground that we all walk and build our homes upon contains varying levels of naturally occurring radioactive elements that decay into radon gas, which can seep into homes and become a health concern. To learn what you can do to protect yourself and your family, please see

Cosmic (Space) Radiation

Outer space is full of various types of radiation, such as heavily charged particles and gamma rays. Fortunately, Earth has an atmosphere that helps absorb and filter them out, which protects us from high doses of cosmic radiation. However, some radiation is able to make it through. The dose of cosmic radiation that you receive varies depending on the altitude of the area in which you live. Since air is thinner at higher elevations, less cosmic radiation is filtered out than it is at lower altitudes with thicker air.

Top of page

Other Natural Radiation Sources

Other natural sources, such as radiation naturally present in our own bodies and radiation from elements in the ground ("Terrestrial" in addition to radon gas), are also all around us. The following chart from the National Council on Radiation Protection and Measurement (NCRP) shows all sources of natural radiation exposure and the percentage of our annual dose that comes from each source:

Man made Radiation Exposure

Medical Radiation Exposure

The National Council on Radiation Protection and Measurement exit EPA(NCRP) published a study in 2009 that found that nearly half of the radiation to which the US population is exposed comes from medical sources such as CT scans, x-rays, and nuclear medicine. While individual exposure from medical sources varies considerably depending on the number and types of procedures that one undergoes, the NCRP has indicated that medical radiation exposure is much more common now than ever before. Thanks to advancements in modern science and medicine, doctors are now better able to diagnose ailments and save lives through the use of these procedures. For more information on radiation emitting products and procedures, please see the Food and Drug Administration’s Center for Devices and Radiological Health.

Other Man made Sources of Radiation Exposure

While the primary source of man made radiation exposure comes from medical sources, there are various other sources that expose us to small amounts of radiation. Information on other sources of radiation exposure can be found on our RadTown educational website. For a more technical resource please see United Nations Scientific Committee on the Effects of Atomic Radiation: SOURCES AND EFFECTS OF IONIZING RADIATION. exit EPA

Top of page


Jump to main content.

Facts and information on Chernobyl