Collaborative exercise on the use of FISH chromosome painting for retrospective biodosimetry of Mayak nuclear-industrial personnel

Purpose: To investigate within the framework of a multilaboratory study the suitability of FISH chromosome painting to measure so-called stable transl ocations in peripheral lymphocytes of Mayak nuclear-industrial workers (fro m the Southern Urals) and their use for retrospective biodosimetry. Material and methods: Chromosome analyses were carried out from 69 workers who had received protracted occupational radiation exposures (0.012-6.065 G y) up to similar to 40 years before blood sampling. Twenty-one unexposed pe ople living in the same area were controls. A multicolour FISH-painting pro tocol with the target chromosomes 1, 4 and 8 simultaneously with a pancentr omeric probe was used to score potentially transmissible chromosome-type ab errations (reciprocal translocations 2B and related 'one-way' patterns I-II I according to the S&S classification). Results: Individual biodosimetry estimates were obtained in terms of these potentially long-term surviving aberration types based on the linear compon ent of a low dose-rate gamma -ray calibration curve produced using identica l staining and scoring protocols. For comparison, the workers' personal and total background doses were converted to red bone marrow doses. The estima ted doses were mainly lower than would be predicted by the calibration curv e, particularly at accumulated higher dose levers. Conclusions: Owing to the limited life-time of circulating T-lymphocytes, t he long-term persistence of translocations in vivo requires the assumption of a clonal repopulation of these naturally senescing cells from the haemop oietic stem cell compartments. Obviously such a replacement cannot be fully achieved, leading to a temporal decline even of the yield of transmissible aberrations types. Assuming further a highly selective capacity of stem ce lls against any type of chromosomal damage and the fact that one must rely on partial genome findings, the potential of FISH chromosome painting for r etrospective dose reconstruction is probably limited to a decade or so afte r high-level protracted radiation exposure.