Problems Related to the Evaluation of Critical Group Doses

The identification of the critical group in a given population and the evaluation of the doses received by its members is considered a necessary addition to the estimation of the average doses from various sources of exposure to ionising radiations. It is usually clear that the critical group doses are more or less upper limits of the actual personal doses. This definition gives a measure of freedom to the upper values and reduces the credibility of comparisons between estimates provided by different groups. In some cases the critical group doses are evaluated as averages for a properly defined part of the population. In this case the averages often appear to be quite dependent on the definition of 'proper'. These problems are demonstrated and discussed for certain cases of exposure of the Greek population to natural and artificial sources of ionising radiation. It would seem that critical group dose values should be presented together with intervals of confidence. These intervals would be quite acceptable if they were comparable with the uncertainty in the personal doses due to exposure to natural sources of ionising radiations.