Systematic review of experimental studies on the relative biological effectiveness of tritium

Abstract

Tritium ((3)H) is a radioactive isotope of hydrogen. A number of factors combine to create a good deal of interest in tritium doses, both to workers and to members of the public. Tritium is ubiquitous in environmental and biological systems and is very mobile due to its occurrence as water. In this study we systematically review experimental data relating to tritium exposure with a view to assessing its low dose limiting relative biological effectiveness (RBE(max)). Interpretation of published experimental studies is complicated by the fact that the reference radiations varied, and doses and dose rates were frequently much higher than those normally received by humans. The four available animal carcinogenicity studies gave RBE values of about 2.5 with chronically-delivered gamma-ray reference, and about 1.2 with chronically-delivered X-ray reference. However, because of problems associated with the design and interpretation of the experiments, we do not consider that these RBE values should be taken to apply to the induction of cancer at low doses (i.e. they should not be interpreted as RBE(max)). Combining the six studies with chronic gamma-ray reference, with adequate quantitative data that examined endpoints apart from cell survival and related endpoints, yields an aggregate RBE estimate of 2.19 (95% CI 2.04, 2.33); the analogous combined RBE estimate using the three studies with chronic X-ray reference groups is 1.17 (95% CI 0.96, 1.39). Again, problems with the design, in particular the range of doses used in some of these studies, mean that these RBE values should also probably not be interpreted as RBE(max).

Accidental release of tritiated water – toward a better radiological assessment

“…More recently, we have taken into account the special role of brain in human metabolism and made a careful analysis of all model input, expanding also the model for the case of infants and using recent results on RBE [15]. Comparing to the deterministic ICRP dose coefficients, our results are close (up to 30%) for HTO intake, when RBE is ignored.…”

Revue de l’état des connaissances des effets du tritium sur la santé et l’environnement au Canada – un outil pour orienter la surveillance réglementaire

“…• lorsque les rayons X sont utilisés comme référence, l'EBR est d'environ 1,4 (Little et Lambert, 2008) ; • lorsque le rayonnement gamma est utilisé comme référence, l'EBR est d'environ 2,2. La Publication 92 (ICRP, 2003) privilégie le choix du rayonnement gamma comme référence en s'appuyant sur le fait que les principes de radioprotection reposent principalement sur les données d'études des survivants de la bombe atomique et que ces survivants ont presqu'exclusivement été exposés à des rayons gamma.…”

Impact du tritium autour des centrales nucléaires EDF

“…Cette demande repose notamment sur la revue de toutes les expérimentations animales déjà publiées (Little et Lambert, 2008).…”