Direct biological dosimetry in Chernobyl clear-up workers

Full text: In cases of large-scale radiological accidents like Chernobyl (1986) the estimation of somatic risk to exposed populations became a problem due to lack of direct physical dosimetry data. In such conditions the necessarily information can be obtained from biological dosimetry, firstly by chromosomal aberrations analysis in human peripheral blood lymphocytes. Conventional cytogenetic assay have been carried out in 130 persons recruited as clean-up workers ('liquidators') to the Chernobyl zone in 1986-87 yrs. Blood sampling was performed during 1 year post-irradiation, in 100 persons p to 0.5 year. The aberrations of choice for biological dosimetry were unstable chromosome exchanges (dicentrics and centric rings with accompanying acentric fragments). The dose calculations have been done using the linear term of the dose-response curve built with acute gamma-irradiation of blood in dose range up to 1 Gy. The distributions of biological doses were investigated in groups of liquidators with doses in documents ranging 17-140, 175-230, 250, 260-365, 440-1030 mSv and in the group of non-monitored persons. The weak correlation between monitored individual doses and biological doses was shown; the biological and physical dose distribution peculiarity in monitored groups is discussed. The distribution of individual aberration frequencies and the average yield of chromosomal exchanges in monitored and non-monitored liquidators were identical. The common cohort analysis (monitored and non-monitored persons) showed that the individual aberration yields distribution among liquidators was strictly randomised in accordance with Poissonian statistics. The cytogenetic dose estimations obtained can be of great value for somatic effects risk assessment in post-Chernobyl cohorts