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.

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:

• where you live (the rock type in your locality),
• your state of health (whether you require treatment or investigation in hospital that involves ionizing radiation ),
• your diet (salt substitutes contain potassium rather than sodium and the percentage of potassium that naturally occurs in the radioactive form is higher than that of sodium),
• your occupation (do you work in an environment that exposes you to nuclear radiation?)