DNA is the primary target for the induction of biological effects from radiation in all living
organisms. There are broad similarities in radiation responses from different organisms, and yet
wide differences in radiation sensitivity. The range in lethality from acute exposure to radiation
various by three to four orders of magnitude among organisms, with mammals being among the
most sensitive and viruses being among the most radioresistant (Whicker and Schultz, 1982).
Radiation protection of the environment: providing knowledge and skills to the user
community
Tom Hinton
French Institute for Radiation Protection and Nuclear Safety Page 3 of 7
18-Mar-14
https://wiki.ceh.ac.uk/x/hI9BBw
Damage from radiation is initiated by ionization. Ionization occurs if the radiation has sufficient
energy to eject one or more orbital electrons from the atom in which it interacts. Ionizing
radiation is characterized by a large release of energy (approximately 33 eV per event), an
amount that is more than enough to break strong chemical bonds (e.g. only 4.9 eV are required to
break a C=C bond; IAEA 2010)
The ionization process and resulting charged particles can subsequently produce significant
damage to biological cells. Such damage is often referred to as direct effects. Much of the
biological damage from radiation, however, is due to indirect effects from free radicals (
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