Behaviour of uranium and thorium in the human body and the environment
Background:
For monitoring and assessment of internal exposures, bioassay techniques have to be applied where in vivo measurements are not adequately sensitive. But for a number of radionuclides of significant radiotoxicity, the currently applied bioassay techniques are tedious, time consuming, and show too little sensitivity.
This is the case for some of the long-lived natural radionuclides. Further more, according to EURATOM directive 96/29, the occupational monitoring must also consider exposures due to natural radionuclides. This makes necessary a differentiation between occupational/accidental and exposure to natural radioactivity. Due to their limited sensitivity and the high expenses for measurements of very low activities of such radionuclides, the currently applied procedures are hardly able to accomplish these requirements.
On the other hand, the development of ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) in the last decades has reached a state so that instruments are now available of highest sensitivity in elemental analysis, i.e. detection limits of femtograms per milliliter, and clear separation of atomic masses. Applying high resolution devices (HR-ICP-MS) it is even possible to differentiate elemental masses from polyatomic ion interferences. In a number of publications the application of ICP-MS for measurements of long-lived radionuclides has been demonstrated. But in these experimental studies often the results published have been obtained only at high expenses in order to attain lowest detection limits and highest precision whereas accuracy is checked merely by a few authors. Therefore, starting from these considerations it is urgently required to evaluate to what extent ICP-MS can be applied for routine uses in incorporation monitoring. For this purpose, numerous factors influencing the measured values have to be studied and standard procedures for sample preparation and measurement have to be developed and validated. With regard to the significant differences in costs of the instruments and man power required, it will be ascertained which type of ICP-MS is required for the particular applications.
Topics of research:
- Optimisation of urine sampling with regard to the measurement of uranium and thorium in urine by ICP-MS
- Optimisation of sample preparation for ICP-MS measurements of uranium and thorium
- Optimisation of instrumental operating conditions and validation of ICP-MS measurements
- Calculation of factors influencing the interpretation of measured values of thorium and uranium
- Establishment of the background levels of urinary uranium/thorium excretion in non-exposed subjects
Methods:
- TIMS (Thermal Ionisation Mass Spectrometry)
High sensitivity, accuracy and precision - ICP-MS (Inductively Coupled Plasma – Mass Spectrometry)
Similar accuracy and precision to TIMS
High sample throughput, ease of use
Contact persons:
Dr. Vera Höllriegl, phone: +49 89 3187-3219
Dr. Uwe Oeh, phone: +49 89 3187-4247