Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) simply exist all around us. For example many areas have Radon and require mitigation of the radiation from Radon.
TENORM is the result of industrial activity. Naturally occurring radioactive materials are everywhere, and activities like oil drilling can bring more materials to the surface. Generally it's at very low concentrations.
Background radiation is the ubiquitous ionizing radiation that people are exposed to, including natural and artificial sources.
Background Radiation Equivalent Time, or BRET, is a unit of measurement of ionizing radiation dosage. One BRET is the equivalent of one day worth of average human exposure to background radiation. The unit is also referred to as BERT (Background Equivalent Radiation Time).
A banana equivalent dose (abbreviated BED) is a unit of radiation exposure, defined as the additional dose a person will absorb from eating one banana. The measure is about 9.82×10−8 sieverts or about 0.1 μSv was suggested for a 150 gram banana. The source? Banana's are excellent sources of Potassium, and every time Potassium exists it comes with radioactive Potassium-40.
Environmental radioactivity is produced by radioactive materials in the human environment. While some radioisotopes, such as strontium-90 (90Sr) and technetium-99 (99Tc), are only found on Earth as a result of human activity, and some, like potassium-40 (40K), are only present due to natural processes, a few isotopes, e.g. tritium (3H),
result from both natural processes and human activities. The
concentration and location of some natural isotopes, particularly uranium-238 (238U), can be affected by human activity.
Radioecology is a branch of ecology,
which studies how radioactive substances interact with nature; how
different mechanisms affect the substances’ migration and uptake in food chain
and ecosystems. Investigations in radioecology might include aspects of
field sampling, designed field and laboratory experiments and the
development of predictive simulation models.