article_snippet.sent: The other, natural half occurs from radioactive compounds in soil and building materials like concrete and brick.
article_snippet.sent: The small amount of mineral potassium in the human body is also  radioactive.
article_snippet.sent: Particles from space interact with the atmosphere and Earth's magnetic field to generate cosmic radiation.
article_snippet.sent: Sources are said to include gamma ray bursts, solar flares and supernovae.
article_snippet.sent: It is what's known as ionising, which means particles can alter charged particles from atoms that can potentially cause chemical changes in body tissue.