page_title: Environmental radioactivity
section_title: Man-made
hierarchical_section_title: Environmental radioactivity / Man-made
caption_attribution_description: English: Per capita thyroid doses in the continental United States of Iodine-131 resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site. 日本語: アメリカ国立癌研究所、「ネバダ核実験のI-131の甲状腺被曝推定」1997年
context_page_description: Environmental radioactivity is produced by radioactive materials in the human environment. While some radioisotopes, such as strontium-90 and technetium-99, are only found on Earth as a result of human activity, and some, like potassium-40, are only present due to natural processes, a few isotopes, e.g. tritium, result from both natural processes and human activities. The concentration and location of some natural isotopes, particularly uranium-238, can be affected by human activity.
context_section_description: The additional radioactivity in the biosphere caused by human activity due to the releases of man-made radioactivity and of Naturally Occurring Radioactive Materials (NORM) can be divided into several classes.
  Normal licensed releases which occur during the regular operation of a plant or process handling man-made radioactive materials.
  For instance the release of ⁹⁹Tc from a nuclear medicine department of a hospital which occurs when a person given a Tc imaging agent expels the agent.
  Releases of man-made radioactive materials which occur during an industrial or research accident.
  For instance the Chernobyl accident.
  Releases which occur as a result of military activity.
  For example, a nuclear weapons test.
  Releases which occur as a result of a crime.
  For example, the Goiânia accident where thieves, unaware of its radioactive content, stole some medical equipment and as a result a number of people were exposed to radiation.
  Releases of naturally occurring radioactive materials (NORM) as a result of mining etc.
  For example, the release of the trace quantities of uranium and thorium in coal, when it is burned in power stations.
caption: Per capita thyroid doses in the continental United States resulting from all exposure routes from all atmospheric nuclear tests conducted at the Nevada Test Site from 1951–1962.
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