Doses and risks from tritiated water and environmental organically bound tritium

This short review provides an explanation of the calculation and use of the ICRP protection quantities, equivalent and effective dose, including the simplifications introduced by using radiation and tissue weighting factors. It discusses the dose coefficients (SvBq^-1 intake) provided by ICRP for intakes of tritiated water (HTO) and organically bound tritium (OBT) and considers uncertainties in the human and animal data on which they are based, including information on the relative biological effectiveness (RBE) of tritium beta particles compared to gamma and x-rays. The review also addresses the specific issue of dose coefficients for ingestion of OBT in Cardiff Bay fish. A distinction is drawn between the adequacy of the ICRP calculation of effective dose to a reference person for the purposes of planning and regulatory control, and the calculation of best estimates of dose and risk to individuals. ICRP will continue to use a radiation weighting factor of 1 for all low LET radiations in the calculation of effective dose, but specific RBE data should be used in risk estimates. Uncertainties in dose coefficients are small for HTO but greater for OBT. The generic consideration of OBT provided by ICRP may not be appropriate for specific organic forms such as OBT in fish.