text: The action of neutrons on stable isotopes can form radioisotopes, for instance the neutron bombardment (neutron activation) of nitrogen-14 forms carbon-14. This radioisotope can be released from the nuclear fuel cycle; this is the radioisotope responsible for the majority of the dose experienced by the population as a result of the activities of the nuclear power industry.
  Nuclear bomb tests have increased the specific activity of carbon, whereas the use of fossil fuels has decreased it. See the article on radiocarbon dating for further details.