Radiation has benefited mankind in many ways, including its use as an energy source and an indispensable tool in medicine. Since the turn of the 20th century, society has sought ways to harness its potential, while at the same time recognizing that radiological exposures need to be carefully controlled. Out of these efforts, and the work of many dedicated professionals, the principles of justification, optimization, and limitation have emerged as guiding concepts.
Justification means that the use of radiation, from any radiation source, must do more good than harm. The concept of optimization calls for the use of radiation at a level that is as low as reasonably achievable (ALARA). Dose constraints, or limitation, are meant to assist in reaching optimization and protection against harm by setting recommended numerical levels of radiation exposure from a particular source or sources. Together, these three principles form the bedrock of the international radiation protection system that drives decision-making and supports societal confidence that radiation is being used in a responsible manner.