Radiation

摘要

Radiation is energy in the form of particles or electromagnetic waves. Based on the effects it can produce in matter, two classes of radiation have been defined: ionizing and non-ionizing. ^1a Ionizing radiation has sufficient energy to remove electrons from atoms and break atomic bonds. Both classes can alter the genetic material (DNA) of a cell. Approximately 80% of our exposure to ionizing radiation is from natural sources, usually at very low dose rates, such as cosmic rays and naturally occurring radioactive elements in the Earth’s crust and air. ^2a Most of the artificial (man-made) radionuclides (unstable nuclei of atoms) released into the global environment have come from nuclear weapons tests. Other artificial sources of ionizing radiation include nuclear facilities, uranium mines, mills and plants and X ray devices.