Validation of biokinetic models for strontium. Analysis of the Techa River and Chernobyl data

The ICRP models used in radiation protection to estimate doses resulting from internal irradiation are based on biokinetic models for different radionuclides. Strontium-90 was one of the main sources of environmental contamination due to accidents in the ''Mayak'' plutonium production complex (Southern Urals, 1949-1956) and the Chernobyl accident (1986). Over 800 measurements of bone-autopsy, and 31,000 Whole body Counter 90Sr measurements for Techa River population were made at URCRM (Chelyabinsk). Measurements of 90Sr contents in skeleton were performed for residents of the area contaminated due to Chernobyl accident (RPI, Kiev). These unique data allowed to validate the predictions of 90Sr biokinetic models at different times after ingestion, and in the case of complicated rate of intake. Model validation can be considered as best approach for quantifying the reliability of the model's predictions. Available data on 90Sr content in human skeleton were analyzed. 90Sr measurements cover the long period after start of intake: from 2 to 45 years after contamination (Techa River data). Model predictions for all age groups were compared with Techa River and Chernobyl data. For adult persons calculated and measured values of 90Sr body content were found to be very close, especially over the first 15 years after the major intake. After the majority of measured people had attained the age of 45 years and changes of calcium metabolism resulted in a significant increase of strontium elimination rate. The particularities of bone mineral turnover in old persons are not considered in the framework of the ICRP model. The latter feature resulted in a divergence between the model curve and the results of 90Sr measurements for old persons. For children and adolescents the differences between calculated values and measured 90Sr body contents are more significant. The comparison of different strontium biokinetic models is discussed in the paper. (author)