Clinical data from one year follow-up of victims of the radiation accident with 60Co in Bulgaria.

A severe radiation accident occurred on 14 June 2011 in an industrial irradiation facility for medical equipment sterilization in Bulgaria. Five people were exposed for 5-10 min to a 60Co source containing 137 TBq. The Emergency Department of the National Centre of Radiobiology and Radiation Protection (NCRRP), Bulgaria, put into practice the plans for providing medical care in radiation accidents and the procedures developed for assessment of injury severity, the decision-making algorithm regarding subsequent treatment, and the therapy for persons affected. The activities performed for initial assessment of the severity of injury of irradiated patients were published in 2012. Based on predictive assessments of the severity of radiation damage, it was decided that the victims required hospitalization at a specialized hematology clinic. Percy Hospital in Paris was chosen for this purpose. The aim of this report is to present the results of 1-y follow-up for three of the victims. Sadly, 1 mo after the accident, Patient 4 died from a heart attack. The medical opinion was that this was not a direct outcome of the irradiation. Patient 5 was only followed up for 4 mo (118 d) because medical follow-up is voluntary, and despite repeated calls, the patient did not respond. Medical examinations by a physician as well as hematology and biochemical tests were performed using standard laboratory methods. The obtained results were compared to the victims' personal reference limits obtained from annual health monitoring. After the accident, the recovery to normal content of peripheral blood cells was observed in all victims. Nevertheless, there were observed cases of thrombocytopenia, granulocytopenia, and leucocytopenia at various times after exposure. During the period of observation, morphological changes in red blood cells such as anisomicrocitosis, macrocytes, megalocytes, and polychromatic erythrocytes were demonstrated. During the 1-y observation period, all victims showed immediate hematopoietic recovery within 2 mo after irradiation. Slight hypocellularity of bone marrow was noted at the end of the year.