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Background Radiation

Radiation Facts

  • Radionuclides can occur naturally or can be man-made.
  • Natural radiation sources contribute over half of the annual radiation exposure for an average person in the United States.

Radiation is a part of our day-to-day lives. It is a part of the air we breathe, the water we drink and the food we eat. 

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About Background Radiation

Background radiation is the radiation that is present in the natural environment. Natural background radiation is all around us, all of the time. It makes up over half of our yearly exposure to radiation. The amount of background radiation is different at every location. It depends on many factors, including:

This image shows the different pieces of an ecosystem and the different things that could affect it, like solar radiation, disturbances, nutrients, minerals, and organisms.
Source: U.S. National Park Service (NPS)

  • Radionuclides present in Earth’s crust.
  • Radionuclides created by cosmic rays hitting atoms in Earth’s atmosphere. If we are closer to outer space, we are more likely to interact with these radionuclides.
  • Human activity and industry, including byproducts and wastes from processes like water filtration and treatment.
  • Weather, which can help radionuclides from nuclear weapons testing settle back to Earth from the atmosphere.

Scientists study ecosystems to learn how minerals and other chemicals, like radionuclides, move through Earth’s different natural systems. This research is called ecosystem science. Ecosystem science studies every part of the system, including the interactions between water, air, land, plants, animals, and humans. Scientists study radionuclides as they move through ecosystems.

Radionuclides in Earth’s Crust

Some radionuclides have been present in rocks since the formation of the Earth. All radionuclides go through radioactive decay until they reach a stable state. Radioactive decay is the process in which a radioactive element turns into another element, releasing radiation in the process. Natural radionuclides found in the Earth’s crust include uranium and thorium. As they decay, they become other radionuclides such as radium and radon. These radionuclides end up naturally in soil, water and air.

Rocks containing natural radionuclides 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 radionuclides dissolve in water and end up in surface or groundwater.

This is an image of background layers of the earth

More than half of the average annual radiation exposure of people in the United States comes from natural sources. The natural radionuclide, radon, is the largest natural source of exposure. Radon is a natural radioactive gas that gets into homes and buildings. It is important to test your home for radon to reduce your exposure to radiation. Learn more about RadTown’s Radon in Homes, Schools and Buildings.

Radiation from Space

About 5% of the average annual radiation exposure for people in the United States comes from outer space. Our solar system’s sun, and other stars in the galaxy, emit a constant stream of cosmic radiation, which then regularly hits the Earth. When cosmic rays collide with atoms, they can make atoms radioactive. These radioactive atoms are called cosmogenic radionuclides. They are rare, but some of them do reach Earth’s surface and mix with soil and water. Learn more about Cosmic Radiation.

Cosmic radiation is the main source of carbon-14, which is used to date ancient artifacts. This technique is called carbon dating.

Radionuclides from Human Uses of Radioactive Material

Most radioactive material in the environment comes from natural sources. Much smaller amounts of radionuclides come from sources developed by humans. For example, uranium mines, nuclear power plants, and research facilities that use radionuclides sometimes add small amounts of radionuclides to the ecosystem. For most people, the annual exposure from these sources is very low. There may be a serious health hazard only in certain areas where open uranium, hard rock metal mines, other mineral mines or mining wastes are present.

  • Nuclear weapons testing: Mostly in the 1950s and 1960s, nuclear weapons tests released large amounts of radionuclides that spread and remained in ecosystems until the radionuclides decayed away. The Comprehensive Nuclear-Test Ban Treaty Organization (CTBTO) Exithas a network of radionuclide monitoring stations that detect radionuclide particles and noble gases, like xenon, which would indicate a nuclear test.
  • 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 EPA regulates how much radioactive materials can be released from these facilities. Learn more about Nuclear Power Plants.
  • 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 carefully monitored by your state, and must meet federal standards, to make sure the drinking water is safe.

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What You Can Do

  • Get your water tested for radionuclides. If you use water from a private well, you should get your water tested for radionuclides. Learn more about Natural Radionuclides in Private Well.
  • Test your home for radon. Testing at home is easy. Many kinds of low-cost radon test kits are available by phone, online and in stores. If you prefer, you can also hire a professional to do the testing. Learn more about radon, its risk and what you can do to protect yourself, on the EPA’s Radon website.

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