A biokinetic model for molybdenum radionuclides : new experimental results

The ability to describe in a realistic way the biokinetics of radionuclides in the human body is an important requirement in order to get a reliable dose estimation after incorporation of radioactive substances. Recent experimental data have shown the need to introduce relevant modifications to the current model of the biokinetics of molybdenum adopted by ICRP. A new series of investigations, conducted on healthy human volunteers using stable isotopes of Mo as tracers, has been undertaken in order to improve the knowledge of some of the new features outlined in the preliminary investigations. In particular, the results presented here deal with the dependence of the biokinetic parameters on the mass of Mo administered and on its content in the body. The clearance of Mo from blood plasma is not influenced by the administration of different amounts of Mo; the opposite is true for urinary excretion, which is the process adopted by the organism to regulate the body content of Mo rapidly. This fact can be of some importance in deciding a proper intervention after an accidental incorporation of Mo radionuclides.