> -l2- of individual doses is not contemplated. Actual doses received by individuals will vary according to age, size, metabolism, and customs, as well as variations in their environ- ment. These variations are said to make it impossible to determine the maximum individual doses. In practice it is feasible to take account of these sources of variability by the selection of appropriate — critical groups within the population, provided the critical group is small enough to be homogeneous with respect to age, diet and those aspects of behavior that affect the doses received. Such a group should be representative of those individuals in the population expected to receive the highest dose. ICRP believes that it will be reasonable to apply the appropriate dose Limit for members of the public to the mean dose of this group. . bow ™. The inate variability within an apparently homogeneous group means that some members of the critical group will receive doses somewhat higher than the dose limit. At the very low levels of risk implied, the health consequence is likely to be minor whether the dose limit is marginally or substantially exceeded. Limitation of exposure of whole populations is achieved partly by limiting the individual doses and partly by limiting the number of persons exposed. It is of the utmost importance to avoid actions that may prove to be a serious hazard later, when correction may be impossible or costly. np rape Ege wet IR tees oe tee em . preewes s erery me hor