Ionising radiation exposure of the UK population, published June 2025

Life on Earth has evolved and survived for two billion years while constantly exposed to radiation of various kinds. Sources of ionising radiation can be found in soils, in our air and water, and in us. Because it occurs in our natural environment, we encounter it every day through the food we eat, the water we drink, and the air we breathe. Additionally, humans have harnessed radiation for use in industry, electricity generation, communications, medicine and even the home. The development of novel radioactive materials in the 1940s led to dramatic advances, particularly in medical diagnostics and therapy.

The UK Health Security Agency and its predecessor organisations have calculated the exposure of the UK population from naturally occurring and artificial sources of ionising radiation periodically since 1974.

UK average annual radiation dose: 2.6 mSv

Dose is a general term for a quantity of ionising radiation. It is a measure of the amount of energy transferred to a material, such as the body, by that radiation. Unless otherwise specified, the doses referred to within these pages are effective doses, which are calculated for the whole body, taking account of the type of ionising radiation and the sensitivity of the part(s) of the body that received the exposure. The unit for effective dose is the sievert, which has the symbol Sv. One sievert is a large unit, so often a dose is given in thousandths of a sievert - a millisievert (mSv) - or even millionths of a sievert - a microsievert (µSv).

Collective dose is the total dose to a group of people. The collective dose is equal to the average dose (in Sv) over that group multiplied by the number of people in that group. This gives the unit man Sv. These pages mostly refer to the collective dose to the UK population, but in some cases the collective dose to a smaller group, for example all workers in the civil nuclear industry, may be given.

The table above contains a link for each major source to a page about that source of radiation. There is also a link to a page about all the minor sources of radiation.

The table shows that on average each person in the UK receives 2.6 mSv of radiation dose per year. It must be remembered that this is an average, estimated by dividing the total collective dose over all sources by the UK population size. In reality, each person's exposure will vary depending on factors such as where they live and work, whether they have received any medical exposures, or been on any flights.

The information below and in the linked pages contain a few terms that may not be familiar, but the glossary towards the end of this section should help explain them.

Sources of exposure

The table and chart show that almost all our radiation dose typically comes from six major sources of exposure:

• inhalation of radon and thoron gases in non-occupational settings (44% contribution to the total)
• occupational exposure from natural sources, radon and cosmic radiation (4%) (This is almost all from radon exposure. Radon can build up in any building in the same way as it can in the home. Occupational exposure from radon can therefore occur in any building such as offices, factories and shops, without the presence any other source of radiation.)
• cosmic radiation in non-occupational situations (13%)
• intakes of natural radionuclides other than radon and thoron (10%)
• terrestrial gamma radiation (14%) and
• patient exposures from diagnostic medical procedures (16%)

Overall, five out of the six main sources of exposure are from natural sources, contributing 84% of the total collective dose. Only patient exposure from diagnostic medical uses of radiation results from man-made sources. The breakdown of exposures by source of radiation is presented in different way to that in the previous review (Oatway, Jones et al. 2016). The collective doses from both radon and thoron and cosmic radiation are now split into occupational and non-occupational exposures. There is no actual decrease in the dose from radon and thoron. All other sources give the same, or very similar contributions to the previous review. As well as the six main sources of exposure, there are some minor sources of exposure:

• occupational exposure other than from natural radon and cosmic radiation. This includes the civil nuclear fuel cycle, the oil and gas industry, the defence sector, education and research, and medical, dental, veterinary and industrial uses.
• discharges of radioactive material into the environment
• nuclear weapons fallout
• accidental releases of radioactive materials
• exposure to consumer products containing radioactive materials
• exposure of members of the public from transport of radioactive material

The contribution from each of these to the total collective dose is very low, with these six minor sources making in total just under 0.3% of the total collective dose.

Changes in collective and average doses compared to previous estimates

Compared to the previous review of exposure of the UK population from ionising radiation (Oatway, Jones et al. 2016), some of the sources of exposure considered have seen an increase, while others have seen a decrease. Overall, the increases in collective doses exceed the decreases, and it is seen that the total annual collective dose has increased from 170,000 man Sv to 174,000 man Sv. Points of note about changes in collective dose are:

• For non-occupational exposure to radon and thoron, exposure to cosmic radiation at ground level, intake of radionuclides other than radon and thoron, terrestrial gamma radiation, and nuclear weapons fallout, it is assumed that the whole UK population is exposed. The collective dose is estimated by multiplying an average individual dose by the size of the population. In the previous review a population size of 62 million was assumed, while now a population size of 67 million has been used (Office for National Statistics 2022). This leads to an increase in collective dose over time that would occur because of the increased population in the UK, even if the average individual dose remains the same.
• For UK passengers taking flights receiving cosmic radiation exposure at altitude, an increased number of flights compared to the previous review has caused an increase in collective dose. It is assumed that only a subset of the UK population is exposed.
• For people receiving medical exposures, it is assumed that only a subset of the UK population is exposed. Compared to the previous review, the collective dose from medical exposures has decreased, because it has been decided to exclude doses to non-target organs from therapeutic uses of ionising radiation that were included in the previous review. The collective dose given is therefore only from diagnostic medical uses and is slightly lower than the previous estimate.
• There has been a decrease, compared to the previous review, in the estimate of occupational exposure from radon. This is largely from exposure in above ground workplaces, with the collective dose estimated by multiplying the average individual dose by the number of people assumed to be exposed. Previously it was assumed that the whole UK population was exposed, but this most recent estimation uses the estimated size of the working population has been used, leading to a substantial decrease in collective dose.

While the collective dose has increased, the average individual dose has decreased from 2.7 mSv to 2.6 mSv per year. To make sense of this, both the size of the exposed population and the size of the UK population must be considered.

Once collective doses from all sources of exposure have been added together, this total is divided by the size of the UK population to give an average individual dose across the whole population. For exposures where it has been assumed that the whole UK population has been exposed, an increase in collective dose arising from an increase in population size will then be balanced out when the collective dose is divided out by the same UK population.

However, where it assumed that only a subset has been exposed, any increase in collective dose will then be divided by the whole UK population, which is larger than the exposed population. The result is that the contribution to each person is smaller, and particularly when the UK population has increased, this can make the average dose smaller, even when the collective dose has increased.

Glossary

Average dose:It is often not possible to give an exact individual dose as the individual dose to each person will vary depending on specific circumstances and behaviours. In these cases, an average dose may be given. The average dose may be given for a limited group, eg the average dose over all people receiving a chest x-ray, or to all people in the UK. An average dose may be calculated by dividing the total, or collective dose, received by a group or population evenly between everyone in that group. Average doses can be useful to compare relative doses from different types of exposure, but it does not mean that everybody in the group is receiving that dose. Some people will receive a higher dose, some will receive a lower dose. For some types of exposure (eg medical exposure or occupational exposure), many people from the UK population will not receive a dose at all.

Becquerel: The becquerel (symbol Bq) is the unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. One becquerel is actually a small amount of radioactivity, so we often find ourselves using multiples, for example a thousand becquerels - a kilobecquerel (kBq).

Collective dose: It can be useful to consider the total dose to a group of people. This is known as the collective dose and can be the total dose to a specified group (eg all the people working in the civil nuclear industry) or may extend to cover the whole population. The collective dose is equal to the average dose (in Sv) over that group multiplied by the number of people in that group. This gives the unit man Sv.

Consumer product: Personal and household goods such as timepieces, smoke alarms, and gas mantles that contain radioactive material for functional reasons.

Cosmic radiation:Naturally occurring radiation, including charged particles, x-rays and gamma rays, that continually bombards the earth.

Decay: The process of spontaneous transformation of a radionuclide. The decrease in the activity of a radioactive substance.

Decay chain: A radioactive decay chain is a series of radioactive decays where unstable atoms transform into more stable ones over time, releasing radiation in the process. For example, uranium-238 decays into thorium-234, releasing an alpha particle. Thorium-234 then decays into protactinium-234, also emitting an alpha particle. This process continues until a stable element, such as lead-206, is formed.

Dose: For ionising radiation, the quantity of absorbed energy is called a "dose". Unless specified otherwise, this report considers effective dose, which is calculated for the whole body, accounting for the type of radiation and the sensitivity of individual organs in the body that may be exposed. This report considers both collective dose and average dose.

Dose rate: The amount of dose received in a specified time period, for example Sieverts per hour (Sv h-1).

Effective dose: A measure of the energy deposited in the whole body, considering both the type of radiation and the sensitivities of various tissues and organs. Effective dose, frequently abbreviated to dose, uses the unit sievert, symbol Sv.

External radiation: Radiation coming from a source external to the body.

Internal radiation: Radiation coming from a source that has been taken inside the body, for example, by inhalation or ingestion of radioactive material.

Ionising radiation: Radiation that produces ionisation in matter, ejecting or 'kicking out' an orbiting electron from an atom. Examples are alpha particles, gamma rays, X-rays and neutrons. When these radiations pass through the tissues of the body, they have sufficient energy to damage DNA.

Individual dose: This is the dose to one person. This may be a dose from a specific event (eg the dose from an x-ray examination) or the dose over a period of time (eg the dose per year from cosmic radiation). Sometimes the exact individual dose may be known, or an average may be used.

Isotope: An isotope is a variation of an element. Isotopes of the same element have the same number of protons but different numbers of neutrons, meaning they will behave the same chemically but have different masses. Some isotopes can be radioactive, whereas others can be stable.

Nuclear medicine: Term usually applied to the use of radionuclides for diagnosing or treating disease in patients.

Occupational exposure: Exposure to radiation while working. Occupational exposure occurs in a range of sectors. While many workers receive no radiation exposure above natural levels similar to that which they receive at home, some groups of workers are exposed to higher levels of radiation that require careful control.

Radiation: Radiation encompasses emissions of particles or a wide range of energies. This review is concerned with higher energy ionising radiation that has the potential to cause harm to the body.

Radioactive: Possessing the property of radioactivity.

Radioactivity: All matter is made of atoms, which may be stable or unstable. A stable isotope will remain the same over time, but if it is unstable it means that at some point it will spontaneously change by undergoing radioactive decay. We refer to any nuclide that is unstable as a radionuclide. The average number of decays per second from a large collection of nuclei is called the activity of that sample, and is measured in Becquerels (Bq).

Radionuclide: An unstable atom that emits ionising radiation.

Radiotherapy: Term applied to the use of radiation for treating disease, usually cancers, in patients.

Radon: Radon is colourless, odourless radioactive gas. It is formed by the radioactive decay of the small amounts of uranium that occur naturally in all rocks and soils.

Sievert (Sv): The sievert is a unit of dose. One sievert is a large unit, so often a dose is given in thousandths of a sievert - a millisievert (mSv) - or even millionths of a sievert - a microsievert (µSv).

Terrestrial gamma radiation: Continuous external irradiation, from gamma emitting radionuclides present in all geologies, including soils and rocks.

X-ray: A discrete quantity of electromagnetic energy without mass or charge. Emitted by an X-ray machine.

References

Oatway, W. B., et al. (2016). Ionising radiation exposure of the UK population: 2010 review. PHE CRCE Series. Chilton (UK), Public Health England. PHE-CRCE-026.

Office for National Statistics (2022). "Estimates of the population for the UK, England, Wales, Scotland and Northern Ireland, Mid-2021 Dataset.", retrieved 25/03/24.