Choice of organ retention model for evaluating concentration factor and internal exposure dose

There are problems in evaluating C.F. from chemical analysis data as well as isotopic equilibrium data obtained by tracer experiments when C.F. is utilized a parameter of internal exposure. The former method gives only static value obtained at a certain age of animals. Usually it is difficult to know detailed character of biological specimen analysed. Though with the latter method, we can easily collect various information on experimental animals in vivo, it has another neck point. With some nuclides, it is difficult to observe equilibrium between organisms and environmental water within a limited experimental period. The kinetic study says there are more patterns of which turnover of a nuclide between organism and surrounding does not obey one compartment model kinetics. The kinetics of some nuclides shows better fit to a power function model. This means the presence of the deposition mechanism into a certain organ, where C.F. should be theoretically of infinite value. It is recommended, we should take account of specific character of turnover of each element for varied biological factors and should know the broad range of estimating C.F.. (author)