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Radiation is part of everyday life. We are all exposed to radiation from natural sources e.g. radon gas and manmade activity e.g. for medical reasons.
The term ‘radiation dose’ is used to describe the amount of energy absorbed by a material from ionising radiation passing through it. The most common measure of radiation dose to people is called ‘effective dose’.
The effective dose takes account of the different sensitivities of organs in the body and the effects of different types of radiation. Effective dose is measured in units called Sieverts (symbol Sv). As a Sievert is a large dose of radiation, in most cases radiation dose will be given in Microsieverts (one-millionth of a Sievert) or in Millisieverts (one thousandth of a Sievert – symbol mSv).
In the UK, Public Health England has calculated that on average people receive an annual radiation dose of 2.7 Millisieverts, mostly from natural sources.
Further information comparing radiation doses from different sources of exposure is available via this Public Health England webpage.