These include the use of X-rays for radiography and tomography, and radioactivity in nuclear medicine. On average, a person receives 2000 microsieverts a year from natural background radiation. An additional dose from medical use of radiation depends on your medical history. Radiation doses in cancer therapy may be larger still. Some people receive more radiation than others.
Radioactive fallout affects mainly our food and drink.
Some foods like olives and brazil nuts accumulate more radioactivity than others. The human race has evolved over millions of years in this radioactive environment. In everyday life we cannot avoid the majority of natural radiation. However, near local sources of radiation you should use distance, time and radiation shielding to provide protection. Staying further away from the source reduces your dose, but if it is necessary to approach a source you should minimise the time spent near it, and if it is strong, you should ensure that adequate shielding is maintained between you and the source.