Introduction : A severe radiation accident occurred on 14 June 2011, in an industrial irradiation facilities for medical equipment sterilization with very high-activity gamma sources. Five people were exposed for 5 to

10 minutes to 60Co source (137 TBq). The absorbed doses are 5.63 Gy for P1 to 1.25 Gy for P5 [6]. We put into practice the plans for medical care provision in radiation accidents and the developed procedures for

injury severity assessment, the decision-making algorithm regarding subsequent treatment and therapy of persons affected. The activities performed for initial assessment of the severity of injury of irradiated patients

was published in RPD journal [4]. Based on predictive assessments of the severity of radiation damage, it was decided that the victims required hospitalization at a specialized haematology clinic, where treatment with

growth factors to help haemopoiesis recovery was used. The aim of this report is to present the results of one year follow-up of the victims.

Results and discussion

The patients’ blood analysis results are presented in Tables 1, 2, 3 and 4.

P1: The restoration of WBC count is registered around days 60 after irradiation. From day 76, a decline to the lowest level of personal reference limit was established. By the end of the first year values remain lower than

average. Lymphocytes did not reach reference levels throughout the period of observation. Granulocytes reaches upper control levels at days 55 to 65 after exposure. Then a statistically significant decreasing trend was

registered between 170-210 days. At the end of the year the values were stabilized to the control level (Table 1).

P2 (Table 2): After treatment, the values of WBC were within the personal reference range at day 70 after exposure, after then leukocytes decline to the lower control level and in few cases under the limit. Lymphocytes

fluctuate, but in most cases the values were below the lower limit of the control value. Granulocytes were persistently elevated above the control at day 70 after exposure, and then reached normal values. Within the year

(from days 55–62 and 176-207) single macrocytes were registered.

P3: After initially registered increase above the normal range at day 70 after exposure, leukocytes decreased to the lower limit and remained unchanged throughout the one year observation period. Lymphocytes did not

reach normal values, as established in the other patients (Table 3). Similar to P2, granulocytes of P3 were elevated above the control until day 70 after exposure, and then decreased below the lower control limit.

P5 (Table 4). was considered first degree METREPOL [5] and was not treated with growth factors, since in such cases spontaneous recovery of bone marrow is expected. Values below the lower control limit for

leukocytes were registered until day 55 after exposure and then the results were within the normal limits. In lymphocytes were observed fluctuations with prevalence at or below the lower normal limit. Granulocytes were

in referents limits. Microtcityc anemia with slight hypochromic RBC was noted to 90 days after exposure.

The results for PLT in all patients submitted of therapy with growth factor were registered below lower personal limits. For P5 the result was in normal ranges. Hypoplasia of bone marrow was detected for patients 1, 2

and 3, one year after the accident.

The most common effects stochastic effects after radiation accident are leukemia’s, solid tumors and reduce life span by showing them tied with different latency [7, 8]. The majority of radiogenic tumors have no dose

threshold [10] and a risk of cancer development increases with radiation dose. Studies of patients after the Chernobyl accident showed that during the first five years after it happened, the peripheral blood indicators

returned practically to normal values although transient moderate cytopenia was observed in many victims. Reduction was registered mainly in thrombocytes and, to a lesser extent, in neutrophils and lymphocytes. There

was little, if any, reduction in either hemoglobin or erythrocytes. For both the group of ARS survivors and the group of persons with unconfirmed ARS, haematopoiesis has generally recovered [2, 3]. Even with exposure

below 1Gy, lymphocytopenia is registered in 42.9% and 28.6% for granulocytopenia [10]. Instability in hematopoiesis and registered suppress cellular and humoral immunity and nonspecific resistance mechanisms [1,

8] is a significant risk factor for the development of stochastic effects. It is estimated that leukemia and myelodisplastic syndrome develop more frequently in subjects with persistent cytopenias [2].

Medical Follow-up of Persons Accidentally Exposed to 60Co in Bulgaria

J. DJOUNOVA, I. GULEVA

National Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria

Methods

Examinations are conducted by a physician, a neurologist, and a radiobiologist. Hematology tests are performed. Standard laboratory methods are used. Morphological characteristics of different types of blood cells and

parallel count of leukocyte components are evaluated microscopically on blood smears stained with May-Grunwald and Giemsa. The obtained results are compared to the victims' personal reference limits obtained at

annual monitoring.

Conclusions

The registered value below lower reference limit for WBC, lymphocytes, granulocytes and platelets is a potential risk factor for development of hemopoietic malignancy. It is essential to perform a long term follow up of

the victims in term to early recognize the lattes effects of exposure to ionizing radiation.

Indices Personal

Referent Limit (X±sd) n=26

P5

DAY 48 51 55 58 62 65 69 76 90 104 118

WBC(109/L) 6.05 ± 1.05

*2.9

*4.6

*3.95 6.5 5.9 7.4 5.6 5.3 5.4 7.5 6.0

GRAN(109/L) 3.87 ± 1.03

*2.01 3.13

*2.73 4.94 4.72 5.48 3.81 3.98 3.94 5.70 4.14

Ly(109/L) 1.51 ± 0.39

*0.72 1.19

*0.83 1.10

*0.83 1.48 1.46

*0.95 1.19 1.57 1.2

MO(109/L) 0.34 ±0.01

*0.17

*0.28 0.39 0.45 0.35 0.44 0.34 0.37 0.27 0.38 0.66

EO(109/L) 1.49 ± 0.87 - 0.46 0.39 0.19 0.12 0.15 0.11 0.21 0.16 0.3 0.18

RBC(1012

/L) 4.18 ± 0.39 3.53 *3.73

*3.76 3.83 3.80 3.90 4.01 3.67 3.88 4.19 4.31

HGB(g/L) 127 ± 7.45 *105

*116

*115

*119 123 122 124

*113

*116 130 132

#HCT (%) 36 - 48 33 33 33 34 35 34 36 33 35 37 38

PLT (G/L) 265 ± 63 220 328 250 267 249 289 273 237 218 244 263

Table 4: Blood analysis of Patient 5 (P5)

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*value below Personal Referent Limit; value above Personal Referent Limit – italic;

#HCT value – normal range for women (population data)

* EPR Conference 2015, IAEA Headquarters Vienna, Austria