Assessing harm from radiation

The assessment of harm to people from radiation exposure can be divided into two categories. The first is the quantitative estimation of the probability or number of effects of different types. The second is the structured application of judgements as to the relative importance of the different effects and, if appropriate, their aggregation. The most recent data on radiation risks has been used to set up a system of dosimetry that allows for the different characteristics of various radiations in causing damage to tissues and the different probabilities of tissues developing fatal or non-fatal cancers or changes leading to hereditary effects. Since the best description of the excess probability of cancer induction from radiation now appears to be one that is related to the underlying probability, the radiation-induced harm is dependent on the characteristics of the exposure population. Some of the judgements as to the relative importance of the different effects have been built into the dosimetric quantities. This applies particularly to the relationship between fatal and non-fatal cancers and between cancers and hereditary effects; however the time distribution of effect is also of importance. All of these aspects have been taken into account by the International Commission on Radiological Protection in producing their latest recommendations on standards for protection. (author)