[en] The presentation and re-tabulation of data concerning population exposure are discussed in outline in relation to the NRPB 1978 report on the U.K., and arising from uncertainty about conversion factors from exposure in WLM to effective dose equivalent in the case of exposure to radon decay products. It is suggested that two conversion factors are required, one for exposure in the general environment, and one for exposure in mines, and that these conversion factors, should be, in round numbers, about 5 and 10 mSv per WLM, respectively. The diagram of effective dose equivalent as shown in the 1978 report is reconstructed to take into account the modifications suggested. (U.K.)