Sources of Background Radiation

⚛️ Sources of Background Radiation

Figure 1: Sources of background radiation in the UK — radon gas is by far the largest contributor

Background radiation comes from both natural and artificial sources. In the UK, natural sources account for about 85% of the total.

Natural Sources (approximately 85% of total)

• Radon gas (~50%) — The biggest single source. Radon is a radioactive gas produced when uranium-238 and thorium decay in rocks and soil. It seeps up through the ground and can accumulate in buildings, particularly in basements. It emits alpha radiation, which is especially harmful when inhaled because alpha particles are absorbed completely by lung tissue.
• Food and drink (~12%) — Natural radioactive isotopes such as carbon-14 and potassium-40 are present in all food. Since these are incorporated into our bodies, we have a small amount of radioactivity within us at all times.
• Cosmic rays (~10%) — High-energy particles from the Sun and other stars constantly bombard the Earth's atmosphere. Most are absorbed by the atmosphere, but some reach the ground. At high altitude (on aircraft or mountains) the atmosphere provides less shielding, so exposure increases significantly.
• Gamma radiation from ground and buildings (~10%) — Naturally occurring radioactive materials in rocks, soil, and building materials (stone, concrete) emit gamma radiation continuously.

Artificial Sources (approximately 15% of total)

• Medical uses (~14%) — X-rays, CT scans, and radioactive tracers used in diagnosis and treatment. This is the largest artificial source, and it varies greatly — most people have few medical exposures, but patients undergoing cancer radiotherapy receive very high doses.
• Nuclear weapons fallout and nuclear industry (~1%) — Fallout from past nuclear weapons tests still contributes a tiny amount. Nuclear power stations contribute less than 0.1% of average background radiation under normal operation.