Ionising radiation: dose comparisons
Published 18 March 2011
© Crown copyright 2011
This publication is licensed under the terms of the Open Government Licence v3.0 except where otherwise stated. To view this licence, visit nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@nationalarchives.gov.uk.
Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned.
This publication is available at https://www.gov.uk/government/publications/ionising-radiation-dose-comparisons/ionising-radiation-dose-comparisons
Ionising radiation has enough energy to cause damage to cells which can increase the risk of cancer later in life. However these risks to health are actually low and ionising radiation is widely used in cancer therapy. In general the health effects of ionising radiation are dependent on the dose received. While low doses increase the risk of cancer later in life, very high doses act like a poison and can be fatal.
In the UK, Public Health England calculated that on average people are exposed to about 2.7 millisieverts (mSv) of radiation a year. A millisievert is a measure of radiation dose which accounts for the fact that ionising radiation can affect different parts of the body to differing degrees. The millisievert dose also allows for the different effects of different types of radiation, x rays, gamma rays, neutrons, alpha particles and beta particles.
The 2.7 mSv dose that people in the UK are exposed to comes from a number of sources. Many building materials contain low degrees of natural radioactivity and radon gas seeps from the ground into all buildings, so the largest exposure is to naturally occurring radiation in homes and workplaces. There are also significant contributions from naturally occurring radioactivity in food and from medical exposures.
1. Comparison of doses from sources of exposure
| Source of exposure | Dose |
|---|---|
| Dental x-ray | 0.005 mSv |
| 100g of Brazil nuts | 0.01 mSv |
| Chest x-ray | 0.014 mSv |
| Transatlantic flight | 0.08 mSv |
| Nuclear power station worker average annual occupational exposure (2010) | 0.18 mSv |
| UK annual average radon dose | 1.3 mSv |
| CT scan of the head | 1.4 mSv |
| UK average annual radiation dose | 2.7 mSv |
| USA average annual radiation dose | 6.2 mSv |
| CT scan of the chest | 6.6 mSv |
| Average annual radon dose to people in Cornwall | 6.9 mSv |
| CT scan of the whole spine | 10 mSv |
| Annual exposure limit for nuclear industry employees | 20 mSv |
| Level at which changes in blood cells can be readily observed | 100 mSv |
| Acute radiation effects including nausea and a reduction in white blood cell count | 1000 mSv |
| Dose of radiation which would kill about half of those receiving it in a month | 5000 mSv |