Cytogenetic indices in blood lymphocites of individuals from the staff working on new confinement buildining in Chornobyl NPP zone.

Objective. Сytogenetic indication of possible exposure of contracting staff individuals, performing work on dismantling the ventilation pipe of "Shelter" object of Chornobyl NPP (ShO). Materials and methods. Cytogenetic examination of 12 individuals among the employees of contractors performing work on dismantling the ventilation pipe of ShO was provided. For comparison individuals who had no contact with the radiation factors for the profession activity were examined. Routine analysis method of uniformly stained chromosomes of peripheral blood lymphocytes was used. 11 388 metaphase plates were analyzed. Results. In contracting staff mean group frequency of aberrant lymphocytes, chromosome (dicentrics, acentrics, abnormal monocentrics) and chromatide type aberrations is significantly higher than such frequency in the comparison group. Three staff persons had individual frequency of specific markers of exposure - dicentric chromosomes with accompanying fragments significantly higher than their mean population level and the average frequency in the comparison group. It indicates the probability of their excess radiation when working in Chornobyl NPP local zone. Cells with two chromosome exchanges and one multiaberrant cell were registered in staff with the absence of such in control persons. The calculated estimated radiation doses of two staff persons were 87-123 mGy and and one person 210-240 mGy of acute exposure respectively. Conclusion. Calculated by frequency of dicentric chromosomes tentative "biological" doses of three staff persons show a more significant radiation effect comparing to the data of physical dosimetry.