[en] Literature data show that the activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in traditional building materials vary within a range of two orders of magnitude. If allowance is made for the increasing use for building purposes of industrial wastes with high levels of activity, the range of activity concentrations even may extended over four powers of ten. The resulting radiation exposures vary in the same manner and exceed in part the mean values of natural terrestrial radiation exposure. It is therefore desirable to conduct more extensive experimental investigations and to formulate radiation protection standards for building materials. (author)