Sources of Background Radiation (WJEC GCSE Science (Double Award)): Revision Note
Sources of Background Radiation
There are two types of background radiation:
Natural sources
Artificial (man-made) sources
Natural Sources of Background Radiation
Radon gas from rocks and buildings
Airborne radon gas comes from rocks in the ground, as well as building materials e.g. stone and brick
This is due to the presence of radioactive elements, such as uranium, which occur naturally in small amounts in all rocks and soils
Uranium decays into radon gas, which is an alpha emitter
This is particularly dangerous if inhaled into the lungs in large quantities
Radon gas is tasteless, colourless and odourless so it can only be detected using a Geiger counter
Levels of radon gas are generally very low and are not a health concern, but they can vary significantly from place to place
For example, some areas may contain rocks and soil which emit higher concentrations of radon gas, such as Wales and Cornwall
Radon Concentration Map of the UK

Radon gas occurs naturally in all rocks and soils. The concentration of radon gas varies from region to region in the UK. The darker red regions show where higher radon concentrations are more likely to occur
Cosmic rays from space
The sun emits an enormous number of protons every second
Some of these enter the Earth’s atmosphere at high speeds
When they collide with molecules in the air, this leads to the production of gamma radiation
Other sources of cosmic rays are supernovae and other high energy cosmic events
Carbon-14 in biological material
All organic matter contains a tiny amount of carbon-14
Living plants and animals constantly replace the supply of carbon in their systems hence the amount of carbon-14 in the system stays almost constant
Radioactive material in food and drink
Naturally occurring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elements
Some foods contain higher amounts such as potassium-40 in bananas
However, the amount of radioactive material is minuscule and is not a cause for concern
Artificial Sources of Background Radiation
Nuclear medicine
In medical settings, nuclear radiation is utilised all the time
For example, X-rays, CT scans, radioactive tracers, and radiation therapy all use radiation
Nuclear waste
While nuclear waste itself does not contribute much to background radiation, it can be dangerous for the people handling it
Nuclear fallout from nuclear weapons
Fallout is the residue radioactive material that is thrown into the air after a nuclear explosion, such as the bomb that exploded at Hiroshima
While the amount of fallout in the environment is presently very low, it would increase significantly in areas where nuclear weapons are tested
Nuclear accidents
Nuclear accidents, such as the incident at Chernobyl, contribute a large dose of radiation to the environment
While these accidents are now extremely rare, they can be catastrophic and render areas devastated for centuries
Examiner Tips and Tricks
The sources that make the most significant contribution are the natural sources:
Radon gas from rocks and buildings
Food and drink
Cosmic rays
Make sure you remember these for your exam!
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