Dose Calculation About NORM Regulations in Japan In-depth Data Glossary Information for specialists

  What is a Naturally Occurring Radioactive Material?

  "Nuclide" means type of atomic nucleus; a nuclide that releases radiation is a radionuclide. Radionuclides are classified as "artificial" (artificial radionuclides) and "natural origin" (naturally occurring radionuclide). Naturally occurring radionuclides can be subdivided to "those that were carried from space during the period of Earth formation" and "those naturally generated by the effect of cosmic rays." A material that includes artificially generated radionuclides is called "artificial radioactive material." A material that includes naturally occurring radionuclides is called "Naturally Occurring Radioactive Material"(NORM).

Naturally occurring radionuclides from space during Earth formation

Th-232 series
U-238 series

Naturally occurring radionuclides generated by effects of cosmic rays


  During the Earth formation period, there were many types of naturally occurring radionuclides on the earth. These radionuclides repeat the radioactive decay process by releasing a variety of radiation types before finally altering into steady nuclides that stop emitting radiation. However, the speed of alteration for each radionuclide differs, and some radionuclides that decay slowly remain even now, 4.6 billion years after the Earth was born. Thus, all natural resources such as soil, rock, ore, coal, and petroleum existing on the Earth today include naturally occurring radionuclides. Their levels differ according to areas or materials.

  Since the naturally occurring radionuclides included in rocks or soil could be ingested through such foods as vegetable and meat, a little amount of naturally occurring radionuclides would exist in the human body.
  Matters in Question
  At present, details on the specific level of radioactivity concentration in each material are not completely understood, nor is the actual amount of radiation exposed to users. If a material for industry usage includes naturally occurring radionuclides in high concentrations, the workers could be unknowingly exposed to high-levels of radiation. Moreover, even in short-term exposure could be dangerous when handling products, by-products, or waste containing highly concentrated naturally occurring radionuclides. On this basis, the International Commission on Radiological Protection (ICRP) suggested in its 1990 Recommendations Publication that exposure to naturally occurring radioactive materials for industrial use should be controlled as occupational exposure. In Japan, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), which is a regulatory body for NORM, compiled guidelines in June 2009. These guidelines require voluntary self-regulation by users who intend to handle the materials specified by MEXT. For details, see "Guidelines for NORM"on the home page.
  Unlike artificial radioactive materials, naturally occurring radioactive materials do not leak high amounts of radiation or create casualties that result in acute disorders of the human body. However, the future risk of cancer or genetic disorder would be slightly increased. To learn more about the effect of radiation, see "Radiation effects".
  Activities of Japan
  National Institutes for Quantum and Radiological Science and Technology (QST) is developing an original database for information on radiation exposure due to the industrial use of NORMs. This database reflects measurement records and refers to pertinent literatures, providing reassurance to the general public in addition to extensive data regarding NORM for researchers and regulators. Moreover, methods for reducing radiation exposure caused by NORM are being studied.
Return to the top of this page