There are two different approaches to applying the principle of justification in situations involving occupational and public exposures, which depend upon whether or not the source can be directly controlled. The first approach is used in the introduction of new activities where radiological protection is planned in advance and the necessary actions can be taken in relation to the source. Application of the justification principle to these situations requires that no planned exposure situation should be introduced unless it produces sufficient net benefit to the exposed individuals, or to society, to offset the radiation detriment it is expected to cause. The second approach is used where exposures can be controlled primarily by action to modify the pathways of exposure, and not by acting directly on the source. This is likely to be the case in existing and emergency exposure situations. In these circumstances, the principle of justifi­cation is applied when making the decision as to whether or not to take action to avert further exposure. Any decision taken to reduce doses — which will almost always have some disadvantages — should also be justified, in the sense that they should do more good than harm.

In both approaches, the responsibility forjudging the “justification” usually falls on governments, or national authorities, to ensure an overall benefit in the broadest sense to society and thus not necessarily to each individual. However, input to the justification decision may include many aspects that could be informed by users or other organisations, or persons outside of government. As such, justification decisions are often informed by some form of public consultation, depending upon, among other things, the size of the source concerned. There are many aspects of justification, and different organisations may be involved and responsible. In this context, radiological protection considerations serve only as one input to the broader decision process.