Dynamic analysis of chromosome aberrations in three victims of the Tokai-mura criticality accident

Purpose: To investigate the dynamics of chromosome aberrations in the blood cells of three workers severely exposed to neutrons and gamma-rays in a criticality accident that occurred in Tokai-mura, japan, in 1999. Materials and methods: The change with time of the frequency of chromosome aberrations in the three patients was examined using a new analysis to score drug-induced prematurely condensed ring chromosomes (PCC-R) and a conventional metaphase analysis. Results: The frequencies and cellular distributions of PCC-R, dicentrics and rings did not change significantly among the samples obtained at 9-48 h after the accident while the first depletion of lymphocytes occurred. The distributions of these aberrations in the cells of two patients showed a slight overexpression compared with a Poisson distribution reflecting neutron and non-uniform exposures. The dose-response curve of rings paralleled that of dicentrics, but not PCC-R. The half-lives of PCC-R (8.5 months) and of rings (8.7 mouths) were shorter than that of dicentrics (13.5 months). Conclusions: In the three patients of the Tokaj-mura accident lymphocytes in the circulating and extravascular pools had reached equilibrium at 9 h, and highly damaged lymphocytes did not selectively move away from the circulatory system during the first rapid depletion of lymphocytes after exposure. Data on the in vivo half-life of PCC-R as well as dicentrics and rings obtained in the present study may be useful for retrospective dosimetry.