Hence an alpha particle, which would deposit its entire energy over a very short distance, causes far more damage per unit of energy than a gamma ray, which deposits its energy over a longer track. The weight of biological matter in which the energy is deposited is also important. The sensitivities of different organs also vary. The RBE varies according to the organ exposed, the age of exposure, and other factors. A single factor, called the quality factor, for converting deposited energy in rad is used for regulatory purposes, even though this represents a considerable simplification of real life risks.
Alpha radiation is far more damaging per unit of energy deposited in living tissue.
The current quality factor generally used for neutrons is 10. The DCFs used for regulatory purposes are derived from a combination of a variety of experimental data and mathematical models. A unit of equivalent absorbed dose of radiation which takes into account the relative biological effectiveness of different forms of ionizing radiation, or the varying ways in which they transfer their energy to human tissue. For beta and gamma radiation, the quality factor is taken as one, that is, rem equals rad. For alpha radiation, the quality factor is taken as 20, that is, rems equal 20 times rads.