Natural radiation describes a class of physical phenomena that share a spontaneous loss of energy in the radiating body or system that results in a propagation of particles and/or waves that carry the ability to do work and thus change the energy state of an impacted body or system. In general terms, natural radiation usually refers to the spontaneous emission and transmission of subatomic particles through space from a radioactive source. Although the imprecise term "radiation" can refer to a varied group of physical phenomena including electromagnetic, particle, and acoustic radiation, most often it refers to the particles given-off by naturally radioactive elements, such as uranium. Accordingly, natural radiation usually is a term applied to the spontaneous energetic particle emission from natural elements as they decay from unstable nuclides to more stable elemental species.

Many radioactive elements have been artificially fabricated. Such elements, not found...