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. It is also in building materials and items we commonly use. Public Health England and its predecessor organisations have calculated the exposure of the UK population from naturally occurring and artificial sources of ionising radiation periodically since 1974.
The graphic is available here