EVALUATING THE RELIABILITY OF BIOKINETIC AND DOSIMETRIC MODELS AND PARAMETERS USED TO ASSESS INDIVIDUAL DOSES FOR RISK ASSESSMENT PURPOSES

The National Council on Radiation Protection and Measurements (NCRP) i s in the final stages of preparation of a document discussing the reli ability of biokinetic and dosimetric models and parameters used to ass ess individual doses for risk assessment purposes. An effort is made i n the NCRP document to identify the strengths and weaknesses of the cu rrently used biokinetic and dosimetric models, to evaluate the main ca uses of uncertainty associated with important parameters and to show, by way of examples, how an uncertainty analysis can be carried out. It is recognised, however, that most of the information available to con duct a detailed quantitative analysis relates only to a few radionucli des and that many gaps have to be filled in a subjective manner. As an exercise, members of the NCRP group were asked to estimate in a subje ctive manner the reliability of the dose coefficients published in ICR P Publication 30 for a list of about 20 radionuclides commonly associa ted with nuclear facilities. For each radionuclide, the chemical form was specified and two populations were considered: (1) healthy adult m ales, and (2) special groups expected to receive higher doses per unit intake than the average. According to the information provided by the members of the NCRP group, the effective dose received by most health y males should be within a factor of 10 of the ICRP 30 value for most radionuclides and within a factor of 20 for special groups. This paper summarises the main issues that are discussed in the NCRP document wi th respect to the identification and application of procedures for the assessment of the reliability of dose coefficients for estimation of risks to individuals.