The Committee discussed two papers on the properties, metabolism and dosimetry of tritium. The properties of tritium included its rapid transport and uptake in all biota, and its unusual propensities to exchange, bind with organic molecules and accumulate in DNA’s hydration shell.

A long-running debate existed over tritium’s RBE or wR: this was presently set at 1 for tritiated water (HTO). Experimental RBE values varied from 1 to 3; microdosimetric data suggested tritium’s RBE should be 2 or higher. The reports examined uncertainties in tritium’s RBE which suggested RBE values for HTO greater than 1. The Committee considered questions on the interpretation of the parameter RBE in the case of tritiated water. When distributed homogeneously throughout cellular and tissue water, its dosimetric effect would be close to zero. However when bound to biological molecules, its effect would be much larger than 1.

The reports also discussed current biokinetic and dosimetric models for HTO and organically bound tritium (OBT) together with their limitations. One report expressed the view that the current ICRP dosimetric approach for tritiated water did not take full account of long-lived OBT components resulting from HTO intake. The reports also described tritium’s transmutation effects, ionisation density effects, distribution effects and DNA doses. The few epidemiological studies on tritium were also briefly discussed. Concern was expressed that some epidemiological reports on possible effects of tritium exposure were anecdotal and not peer reviewed. A discussion took place on the dose coefficients for HTO and OBT. At present, tritium’s dose coefficients were extremely low: the lowest among common nuclides. Some members of the Committee agreed with the need to examine tritium’s dose coefficients with a view to increasing them: others disagreed. One report recommended wider recognition of tritium’s hazards; a 15-fold increase in HTO’s dose coefficient, with OBT’s dose coefficient 5-fold greater than that for HTO; and research to investigate possible teratogenic risks from exposures to high transient levels of HTO.

The Committee agreed that the tritium papers were very interesting and highly relevant to its remit. They agreed to return to the matter later in the year.


The Committee considered a paper which compared natural and man-made radioactivity. The author considered there was a difference in health risks between exposures to natural and anthropogenic radiation. However the Committee took the view that alpha radiation was the same whether it was emitted by natural or anthropogenic nuclides. The Committee were not persuaded that there was a difference between their effects. In addition, many nuclides were both natural and man-made in origin: it was scientifically untenable to suggest the effects from nuclides were different depending on whether they were anthropogenic or naturally-occurring. The Committee also considered a paper on radon dose, lung cancer and alpha radiation. The paper proposed the hypothesis that lung cancer was a very rare event resulting from a cluster of alpha hits in a short time from deposited hot particles. The Committee queried the report’s hypothesis on a number of grounds and asked the author to inform it if the article were to be peer reviewed or planned for publication.


The Committee discussed whether the issue of depleted uranium (DU) fell within the remit of CERRIE. Although DU was a chemical toxin it was also an internal emitter, so could be said to fall within its remit. However a number of reports had recently been issued on this subject. It was decided that the Committee would collect available information on health effects, and in the light of this, consider whether to examine the matter, taking into consideration the time that remained for the Committee’s deliberations.

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