BIOKINETICS OF URANIUM IN RATS CONTAMINATED BY REPEATED INHALATIONS : IMPLICATIONS FOR THE MONITORING OF NUCLEAR WORKERS
M. Monleau , E. Blanchardon , V. Chazel , M. Claraz , G. Duménil , F. Paquet , chemical and biological approaches in Environment, organisé par l'école doctorale "sciences de l'environnement" d'Aix-Marseille, 6-10/09/2004, Hyères, France.
Inhalation of airborne uranium compounds is one of the major health risks for nuclear workers. For radiation protection purposes, the ICRP dosimetric model is applied to calculate dose coefficients, retention and excretion functions for workers exposed to radionuclides. The model for a chronic contamination is represented by the addition of successive acute intakes. The aim of this work was to test this hypothesis by (1) comparing the theorical and experimental biokinetics of repeated inhalation of UO2 and (2) investigating the biokinetic consequences of UO2 inhalations on a subsequent acute inhalation of UO4. Rats were exposed to uranium aerosols using a nose-only inhalation system. For the UO2 repeated inhalations, the rats were exposed 1 hour per day, 2 days per weeks for 3 weeks. Three rats per condition were sacrificed 1, 3, 7, 16 and 30 days after the end of the contamination period. Organs, urine and faeces were mineralised to determine the uranium content by kinetic phosphorescence analysis (KPA). The theoretical and experimental biokinetics of the UO2 repeated inhalations have been compared and were found to be similar. In this case, the addition of successive acute intakes may be used to simulate a repeated contamination. The comparison between UO4 biokinetics preceded or not by repeated UO2 inhalations allowed to appreciate the importance of the history of exposure. Preliminary results showed that urinary excretion of UO4 seems to be modified by previous repeated UO2 inhalations. The influence of the UO2 inhalation time pattern is now investigated by comparing the effects of repeated or acute UO2 inhalations on an acute UO4 inhalation. The knowledge of the biokinetics of repeated contaminations by uranium could conduct to a better understanding of the effects of uranium inhalation on the respiratory tract clearance and absorption to blood, and could allow to improve the monitoring of workers exposed to contamination by airborne uranium.