Radiation Dose Calculator Background Information
Have You Tried the Radiation Dose Calculator?
This tool helps you see where your largest sources of radiation dose come from and how they compare to each other.
The information on this page provides additional context for the Radiation Dose Calculator. The Calculator is maintained to reflect the latest radiation science. Updates to previous versions involved adding or removing values to align with the latest science. These updates also consider how radiation sources are used in our lives and improve communication about the sources of radiation and their impact on your annual dose estimate.
On this page:
Background Radiation
Background radiation encompasses all radiation found in nature, such as radon gas and terrestrial radiation from the ground, cosmic radiation from space, and radiation from food. Background radiation makes up a large share of your annual dose because you’re being exposed regularly. The longer the exposure, the higher the dose.
Radon levels in the home can often be the biggest contributor to your dose from background radiation. There are ways to reduce radon levels in your home. Other resources of radiation, such as cosmic radiation from space, terrestrial radiation, and radiation from food are mostly unavoidable.
Learn more about Background Radiation.
Radon
Radon is a natural radioactive gas that you can’t see or smell. It comes from the natural decay of uranium and radium found in nearly all rocks and soils. Elevated levels of radon have been found in every state. You can test your home for radon to determine if there are high levels of radiation that you should reduce.
Terrestrial Radiation
Terrestrial radiation levels vary by location. Areas with higher concentrations of uranium and thorium in surface soils generally have higher radiation levels.
Cosmic Radiation
Cosmic radiation is emitted by the sun from sunspots, solar flares, coronal mass ejections (CMEs) and proton storms. The Earth’s atmosphere works like a shield, keeping out large amounts of this radiation, but small amounts reach the earth. Radiation dose from cosmic radiation increases the higher you are above sea level.
Default Values
There are two default values in the calculator that are the same for everybody in the U.S., and are automatically filled in:
- Radiation from Food and Water: Some foods contain naturally-occurring radionuclides such as potassium, carbon, and radium. Because the amount of radiation is very small, these foods do not pose a radiation risk. Learn more at Natural Radioactivity in Food.
- Radioactive Fallout from Nuclear Weapons Testing: Aboveground nuclear weapons tests were conducted between 1945 to 1980, which resulted in radioactive fallout that fell from the atmosphere and settled on plants and water. Today there is very little fallout that still exists in the environment. Learn more at Radioactive Fallout from Nuclear Weapons Testing.
Consumer Products/Services
The radiation from consumer products and services usually makes up only a small amount of your annual radiation dose. This is because most people do not encounter these sources on a daily basis. Smoking is an exception—smoking regularly can significantly increase your annual radiation dose.
Building Materials
Some building materials, such as granite, brick, and marble, contain natural radioactivity from elements in the Earth’s crust. For example, granite contains naturally-occurring uranium, thorium, potassium and their radioactive decay products. Brick contains the radioactive materials uranium and thorium. Concrete may contain materials that are naturally radioactive such as fly ash, which is created by burning coal. The amount of radiation released from these materials is typically extremely low.
- Learn more about Natural Radioactivity in Building Materials
- Learn more about Granite Countertops and Radiation Protection
Flights
Radiation from flying comes from cosmic radiation. When you travel by airplane, you are closer to outer space, which increases exposure to cosmic radiation. The latitude, altitude, and duration of the flight are the main factors determining the radiation dose from it. The Calculator estimates dose using an average of 1000 miles for each flight duration. Security screening of people at airports does not use radiation or give you a dose of radiation.
- View Facts About Radiation from Air Travel
- Learn more about Radiation and Airport Security Scanning
- View Frequently Asked Questions on Cabinet X-ray Systems for Baggage Screening
Cigarettes
Cigarettes contain carcinogenic chemicals and radioactive materials that contribute to the formation of cancer. Tobacco plants and their leaves will uptake radioactive materials from radon in fertilizer, along with naturally-occurring radon in surrounding soil and rocks. These radioactive compounds remain in tobacco products made from these plants.
Industrial Sources
You might think living near nuclear power plants and coal-fired power plants increases your radiation dose, but the dose from nearby industrial sources is extremely low.
Nuclear Power Plants
During normal operation, nuclear power plants release very low amounts of radioactive materials into the air and these releases are strictly regulated and monitored.
Coal-fired Power Plants
Generally, the waste produced by coal-fired power plants, such as fly ash, is only slightly more radioactive than the average soil in the United States. The level of radiation in waste from coal-fired power plants is typically minimal. Ninety-nine percent (99%) of fly ash from smokestacks is captured by filters.
Radiation in Medicine
Medical imaging procedures can often deliver doses in the range reported by the Radiation Dose Calculator and much higher. When justified, modern medical imaging procedures confer benefits that far outweigh health risks from radiation exposure. Imaging technologies can reduce the need for exploratory surgeries to enable treatment, possibly prolonging life. Conversations with your healthcare professionals can help you understand the medical need for procedures requiring the use of radiation. It is important to remember that the decision to undergo medical imaging should be based on clinical grounds rather than the cumulative doses from prior radiation exposure. The dose calculator provides information on common medical procedures including radiography, nuclear medicine, computed tomography, and fluoroscopy.
- Learn more about Medical X-ray Imaging
- Learn more about Ionizing Radiation and Diagnostic Examinations
Radiography (x-rays)
To generate diagnostic images, x-rays are projected from an x-ray tube towards the patient. In the resulting image, the tissues and organs appear as various shades of black and white as different organs allow different amounts of the x-ray beam to pass through them. For example, bone tissue will block more of the x-rays, creating underexposed regions in the final image, which show up as white. Dental x-rays and mammograms are also a type of radiograph or x-ray examination.
Nuclear Medicine
A nuclear medicine study involves injecting a compound into the body that contains a radionuclide to generate images. The compound is called a radiopharmaceutical, a tracer, or radiotracer. The injected radionuclide emits gamma rays. These gamma rays have sufficient energy such that a significant number of them can pass through the body. These gamma rays are then detected by an external imaging camera. The camera uses advanced computational algorithms to create an image of where that radionuclide is distributed throughout the body. By attaching the radionuclide to compounds that target and bind to cancer cells, nuclear medicine studies allow us to find cancerous cells to determine the extent of their spread, or to evaluate the effectiveness of cancer treatments. Radioactive compounds have enabled other medical advancements, such as perfusion exams which can create images of heart tissue.
Computed Tomography (CT Scans)
Computed tomography (CT scan) allows us to obtain detailed three-dimensional images of the body using x-rays. The patient lies on the table of a CT scanner that moves in and out of the donut-shaped ring of the CT scanner. The ring contains an x-ray tube and image receptor that may rotate as fast as five times per second around the patient to obtain many different pictures from all angles. Computational algorithms are then used to show many different two-dimensional images, or "slices," from the 3-D images. This enables doctors to get many views of the area at different depths and from different angles. CT scans were formerly called computed axial tomography scans, or CAT scans. Axial scans are still being performed today, but newer technologies have been introduced that are not limited to axial scans.
Fluoroscopy
Fluoroscopy makes use of pulsing x-ray beams to show movement inside the body in real-time on a monitor. The use of this technology allows us to view the movement of a body part, instruments, or contrast agents through the body. This technology may be used for a wide range of examinations and procedures to diagnose or treat patients. For example, with contrast agents, such as a barium enema, this technology can be used to view the gastrointestinal tract. Other uses of fluoroscopy may include guiding catheters through the circulatory and urinary system, visualizing blood vessels (angiography), or placement or devices, such as stents to open narrowed blood vessels.
What Sources Go In the Radiation Dose Calculator
Radiation doses in the Calculator are informed by the latest science and reports from scientific advisory bodies, like the National Council on Radiation Protection and Measurements (NCRP). For example, many of the medical procedures included in the Calculator are informed by a recent report on medical exposures of patients in the United States. The exclusion of a medical procedure from the Calculator may be attributed to it being uncommon, or impossible to generate a reliable estimate of dose.
The Calculator does include:
Sources of high public interest.
Living near a nuclear power plant is a good example of how public interest influences what is included in the Calculator. The annual dose from living near a nuclear power plant is extremely low and would not warrant inclusion were it not for the public interest on this topic.
Sources that could contribute a large amount of radiation to a person's annual dose.
The sources included in the Calculator are significant and may contribute a noticeable amount to your total annual dose. Some doses may make up a much greater percentage than others.
The Calculator does NOT include:
Radiation worker doses.
People who work with radiation are protected by laws that limit their allowable radiation exposure annually and often require routine monitoring and safety procedures. The Calculator does not include doses from radiation work as it is not a common experience for the general population. Radiation workers interested in learning more about their exposure levels should contact their organization's Radiation Safety Office.
Sources that are no longer common or relevant.
Airport security screening equipment is an example of a dose that is less relevant now compared to the past. Airport security used to be in the Calculator but is no longer included due to changes in screening equipment technology.
Sources that give off only non-ionizing radiation.
Some sources, like Electric and Magnetic Fields (EMF), are of high public interest but are not included because they are non-ionizing. Non-ionizing radiation has enough energy to move atoms in a molecule, but not enough to remove electrons from atoms. Ionizing radiation, which has enough energy to move atoms, is a more dangerous type of radiation. Other types of non-ionizing radiation not included in this tool are radio waves, visible light and microwaves.