Effectance, committed effective dose equivalent and annual limits on intake: What are the changes?

The International Commission on Radiological Protection has recently published draft recommendations which include proposals for new weighting factors, W_T for use in calculating effective dose equivalent, now called 'effectance'. The author outlines the concept of effectance, compares committed effectance with the old committed effective dose equivalence and goes onto discuss changes in annual limits on intakes and the maximum organ doses which would result from an intake of an ALI. It is shown that committed effectance is usually, but not always, higher than committed effective dose equivalent. ALIS are usually well below those resulting from the ICRP Publication 30 scheme. However, if the ALI were based only on a limit on effectance it would imply a high dose to specific organs for certain nuclides. In order to control maximum organ doses an explicit limit could be introduced. However, this would destroy some of the attractive features of the new scheme. An alternative would be a slight modification to some of the weighting factors.