Dose assessment based on the translocation frequency in T-lymphocytes: development and validation of biodosimetry...

The objective of the study was to develop and validate a method (biodosimetry system) for estimating red bone marrow (RBM) doses from internal exposure to ⁸⁹Sr and ⁹⁰Sr using FISH-based biodosimetry in T-lymphocytes. The method includes assessment of doses to T-lymphocytes and RBM using: data on chromosome translocation frequencies; a calibration curve data; a model of age-related dynamics and kinetics of T-cells; a biokinetic model for strontium; and a dosimetric model for ^89,90Sr. Conversion factors from chromosome translocation frequencies to T-cell-doses and then to RBM-doses were estimated. The biodosimetry system was validated by comparing FISH-based doses and doses obtained from physical dosimetry for residents of Techa riverside settlements (205 persons; 221 blood samples; dose range according to physical dosimetry data from 0.04 to 4.8 Gy). The Techa River (Southern Urals, Russia) was contaminated with radioactive waste in the 1950s. In general, the validation confirms the biodosimetry system applicability. However, the method does better for group dose estimation and has large uncertainties for individual cases. The statistical distributions of "biodosimetric doses" are significantly wider than doses based on physical measurements. In all dose groups identified on the basis of physical dosimetry, there are donors with undetected radiation-induced translocations. The detection limit of individual dose assessments using FISH-based biodosimetry (about 0.5 Gy) is discussed.