X rays
      Radiation used in medicine is the largest source of man-made radiation to people. Most of 
      our exposure is from diagnostic x-rays. Physicians use x-rays in more than half of all medical 
      diagnoses to determine the extent of disease or physical injury. Long wave-length X-rays are
      usually used in X-ray photographs. However, they are dangerous because they can damage 
      living cells deep in the body.


     Fallout from nuclear explosives testing
      Radiation from nuclear explosives testing only accounts to a small percentage to the 
      background radiation.  Nuclear weapon testings produces fission products which are 
      radioactive, they include tritium (3H),  iodine-131 (131I), iodine-129 (129I), 
      cesium-37 (137Cs), strontium-90 (90Sr).


      Radioactive materials released to the environment from 
      nuclear power plants

       Nuclear power reactors, which use uranium, supply us with electricity. Our ability to
       produce power using radioactive materials reduces our reliance on fossil fuels. Nuclear 
       power plant operations account for less than a hundredth of a percent of the average our 
       total radiation exposure. Workers at nuclear power plants receive higher doses of radiation,
       but the overall dose is extremely low.
 
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