Most of the background radiation dose we receive in the UK is from natural sources (about half is inhaled as radon gas). About 15% of our annual dose comes from human activities such as X-rays in hospital or at the dentist or emissions from nuclear establishments.
Thus the figure on the right is for 'Mr. Average in the UK'. Such data is worked out using the radiation doses received by a lot of people living and working in a lot of different locations.
The background dose comes from five main sources:
Some radiation sources are natural but human activities also raise the background count we are exposed to.
The radiation dose you get in a year depends on:
Measuring Backgrount Rate
Before an experiment with a radioactive source is carried out the background rate must be established. This is done by switching on the Geiger-counter when the source is not present and recording the average activity for twenty minutes or so.
This value must then be deducted from any readings taken with the source present so that the true activity of the sample can be found.