Biological dosimetry assessments of a serious radiation accident in Bulgaria in 2011

Abstract

In 2011, a serious radiation accident occurred in Stamboliyski, Bulgaria, in an industrial sterilisation facility using very-high-activity (60)Co sources. For the five persons accidentally exposed, biological dosimetry based on dicentric analysis was performed in Sofia and in Paris, where the patients were transferred for treatment. Before completing the chromosomal dose assessment, and for the most exposed person, a preliminary cytogenetic evaluation based on electronically transmitted metaphase images was made. The averaged acute whole-body dose estimates for the five patients ranged from 5.2 to 1.2 Gy, and good agreement was obtained between the two laboratories. The patients were also assessed by their prodromal responses and depressed blood cell counts over the first week. The cytogenetic dose estimates were in good accord with those derived from the blood counts, and both techniques indicated that, for the two most seriously exposed persons both techniques indicated that the initial prodromal reactions had suggested somewhat less severe exposure.

Assessment of Cytogenetic Abnormalities by FISH in Lymphocytes from a Victim Accidentally Exposed to Cobalt-60

“…Four months post exposure, we still found very high frequencies of all kinds of radiationinduced chromosome aberrations. As expected of unstable aberrations, dicentrics decreased rapidly after exposure (0.96 ± 0.061 vs. 0.425 ± 0.042) [1]. This result correlates with other authors, who reported an average half-time disappearance of lymphocytes containing dicentrics and rings to be 130 days after an accident [14].…”

“…This result could be explained by the miscounting of some dicentrics, because pancentromeric probes were not used in order to be sure that every one was dicentric. In contrast, the frequency of translocations (0.714 ± 0.03 per metaphase cell) is close to the initial frequency of dicentrics (0.96 ± 0.061 per metaphase cell) found right after the accident, but lower [1]. Theoretically, the initial frequency of dicentrics should be similar to the frequency of translocations years after the accident, because of the mechanism of radiation-induced doublestrand breaks [15].…”

“…Blood samples were taken for differential blood counts and cytogenetic analysis for biodosimetry. These have been reported in separate publications [1,2]. The patients were treated in Paris with bone marrow growth factors.…”

“…The aim of this study was to evaluate in vivo by fluorescence in situ hybridization (FISH) the spectrum of induced chromosome aberrations four months after the accident in the most affected patient. Just after the accident,in our lab was estimated a whole body dose of 5.60 Gy (95% confidence interval 4.94-6.25) with an initial frequency of dicentrics of 0.96 ± 0.061 [1]. Conventional and molecular cytogenetic methods were applied to detect chromosome damage after accidental exposure to ionizing radiation.…”

Clinical Data from One Year Follow-up of Victims of the Radiation Accident with 60Co in Bulgaria

“…Brief information about the victims and the exposures (Grégoire et al 2013) is presented in Table 1. Five people were exposed for 5-10 min to very high-activity 60 Co sources, predominantly in the front lower part of the body.…”