Are the risks from tritium exposures underestimated?

Tritium is a radionuclide that will be further used and produced in fusion reactors. The tritium toxicity is well-known but its health consequences are more difficult to evaluate, due to difficulties for assessing doses and to the very few cases of contamination over the years. The assessment of risks resulting from tritium exposure is based on ICRP models that enable calculation of doses in the tissues, by the use of a weighting factor W.R., based on the relative biological effectiveness of the various radioactive emissions. Some authors are currently asking for a revision of the weighting factor to be used for the beta emission of tritium, based on its potential incorporation into DNA. A review of the recent relevant publications published on this subject shows that the relative biological effectiveness of tritium is not so different from that of gamma emissions, which are taken as reference radiations. This is in favour of keeping the current weighting factor of 1 for beta emissions of tritium, value initially proposed and then reaffirmed by the ICRP. (authors)