Towards an appropriate limit for exposure of the general public to radium

Recent reports have highlighted uncertainties about the calculation of dose to man from ingested radium. In specific cases of release to the environment, exposure pathways for the public can be described and a critical group defined. The ICRP suggests a reduction in occupational limits by 1/10 for exposure of the general public (i.e. 5 mSv a-1) where it can be demonstrated that this limit is only occasionally reached. Recognising that there are uncertainties in dose calculations particularly for children, the IAEA recommends that where there is internal exposure of infants or children, the dose to the general public should be limited to 0.5 mSv a-1 or 1/100 of the occupational limit. The ICRP also recommends that where the actual dose to the critical group regularly approaches a significant proportion of the limit over a long period, then a factor of 1/50 should be applied to the occupational limit, giving an allowable dose of 1 mSv a-1. Given such low recommended dose rates, careful study of critical pathways, diet, uptake mechanisms and transfer coefficients and other factors, followed by a detailed monitoring of foodchains to demonstrate compliance with these international recommendations, is necessary