Natural radioactivity is given by radioactive material of terrestrial origin (primarily U-238, U-235, Th-232 and their descendants, as well as K-40), of varying geological abundance, significantly different from one place to another. This is compounded by radionuclides of cosmogenic origin (H-3, Be-7, C-14 etc.). All these earth crust and cosmogenic radionuclides, together with cosmic radiation, form the natural background of ionizing radiation acting upon the living organisms on our planet.
Natural radioactivity, a basic component of the environment, has significantly changed since the past century due to human activities including: mining for, processing and use of fertilisers in agriculture and non-conventional materials in building, etc. Thus the radioactivity concept needed to be reconsidered, i.e. to be subjected to control and surveillance due to its potential implications for human health.
Natural radioactivity (natural radionuclides) exists in the earth crust, on the surface or in depth (NORM- naturally occurring radioactive materials). In the processing, product manufacturing, such materials may be exposed / released into the environment (TENORM – technologically enhanced naturally occurring radioactive materials).
