Monitoring of Cytogenetic Damages in Peripheral Lymphocytes of Children
Living in Radiocontaminated Areas of Belarus
Ludmila S. MIKHALEVICH
Institute of Genetics and Cytology, Academy of Sciences of Belarus,
F.Skorina st., 27, 220072, Minsk, Republic of Belarus.
Tel: (0172) 68-49-18. Fax: (0172) 68-49-17.
E-mail: igc%bas32.basnet.minsk.by@demos.su
The cytogenetic monitoring of Belarussianchildren was started by the Human Radiation
Cytogenetics Group of the Institute of Genetics andCytology of the Academy of Sciences of Belarus inJune 1986. Groups of children for cytogenetic
examination were formed on the basis ofadministrative division of the territory (Table 1).
The aims of the present work is to analyse the dataof 1986 as a practical case of cytogenetic method in
the assessment of absorbed dose in children from
Gomel region affected by the Chernobyl APS
catastrophe, and to compare the data of cytogenetic
examination of 1986 with the results obtained in thefollowing years.
In this connection, we examined children
evacuated from 10 villages within the 30-km zone of
Bragin district, Gomel region, exposed to short-time(2 weeks) radiation, mainly due to fallout ofshort-lived radionuclides, and children residing insettlements in Bragin and Khoiniki district, Gomel
region. The data of radiation monitoring of theradiocontaminated areas are given as of July 1, 1989
(7).
The results of cytogenetic examination of children
in Minsk, and Braslav of Vitebsk region, were used asa control. Selection of the children was random.
Significance of the differences was calculated by
t-Students test.
Conventional methods (9-10) were used for
preparing cytogenetic specimens. Blood samples weretaken and transferred to the laboratory for cultivating
within the same day. Fetal calf serum (10%, Minsk),
phytohemagglutinin Difco P, 100 IU penicillin/ml in
0.5 ml of blood were added to the culture medium,
consisting of Eagle's minimal essential medium(Moscow). For each individual 2-3 cultures were set
up. 200- 300 cells per child were examined forasymmetrical chromosomal aberrations (dicentrics,
centric rings, and excess acentric fragments) andchromatid aberrations (breaks, exchanges ).
In Table 2 are presented group-average data on
chromosome aberration yield for 60 children from 10
villages in the 30-km zone of Bragin district. The
children were evacuated on May 7-8, 1986 to a"clean" zone in Minsk region (two weeks after the

The complicated radiation situation in Belarus
conditioned by the large scale and irregularity ofradioactive precipitation as a result of the Chernobyl
APS catastrophe, resulted in a number of different
sources of irradiation to children.
In the first period after the catastrophe, short-lived
isotopes, mainly I-131, made the principal
contribution to the formation of irradiation tochildren. Dose values for thyroid in children turnedout 3-10 times as high as in adults /1-2/. The situation
having arisen after the Chernobyl disaster ischaracterized by different duration of contact withradiation and by diversity of pollution comprising
irradiation from external and incorporated
radionuclides. An intensive radionuclide mixture
discharge continued till 10th of May. Their large
quantity was released into the environment from thedestroyed reactor for 2 weeks more.
Regretfully, information on genetic important dosein children population based on the data of physicaldosimetry is practically absent. Counts ofchromosome aberrations in peripheral blood
lymphocytes (PBL) of the people who live inparticular radioecological conditions are at present themost objective biological indicator of radiation
effects. Chromosome injuries are the earliest and themost significant among intracellular reactions toionizing radiation; they can be calculated precisely.
Therefore, the WHO, IAEA and UNSCEAR
documents /3-5/ recommend to use cytogenetic
methods in order to estimate the value of doseabsorbed by organism.
The necessity of using methods of biologicaldosimetry and, in particular, traditional cytogenetic
analysis of unstable chromosome aberrations - such as
dicentrics and ring chromosomes - was confirmed
repeatedly in the studies of the consequences ofpeople's
overexposureindifferent
nuclearcatastrophes /6/. However, it is considered that the useof unstable type aberrations in biological dosimetry is
not possible in remote times after overexposure /7/. It
is connected with the fact that the frequency of cells
having dicentric and ring chromosomes is decreases
with the course of time after irradiation.

178

Table 1. Districts from which the study cohorts were sampled and their contamination levels
Radionuclide contamination (Ci/km2)
VillageCs-137
Sr-90
Pu-23930-km zone of Bragin district, Gomel region
v. Nudichi
18.38
3.02
0.0503v. Ilichi
22.03
3.44
0.0140v. Glukhovichi
13.26
1.81
0.0201v. Refalov
20.48
3.35
?
v. Kozeluzhtsy
20.43
3.60
0.0106v. Jasmentsy
9.00
3.69
?
v. Krug-Rutka
3.80?
v. Gorodistche
6.00
0.97
0.0030v. St. Urkovichi
1.40
v. Krivichi
3.45
0.98
0.0188Bragin districtt. Bragin
19.23
1.79
0.0418v. Burki
11.0
0.7?
v. Mikulichi
17.0
0.95
?
Khoinik district
t. Khoinik
6.0
0.93
?
v. Novoselki
19.1
1.97
?
v. Rudnoe
14.0
3.0
?
v. Rudakovo
10.0
1.83
?
Narovlya districtt.Naovlya
17.0
0.9
?
Control zonec. Minsk
0.04
0.02
0.0016t. Braslav
0.04
0.02
0.0016
Table 2. Cytogenetic damages in peripheral blood lymphocyte of children evacuated from the 30-km
zone of Bragin district and residing in Bragin town examined in 1986.
No. of Cells with aberr.
No. of children
No. of cells
No. of dic/ring(mean per 100
Settlement
examinedscoredper cellcells±SE)30-km zone (10 villages)
60
18000
0.00956.8±0.2
t. Bragin
15
3900
0.00537.7±0.4
Control
18
3000
0.00061.4±0.2
Chernobyl
nuclearaccident).
Cytogenetic
examinations were conducted in August, 1986.
A statistically significant increase of the level ofaberrant metaphases, aberrations per 100 cells,
including markers of radiation effect, namely,
dicentrics and centric rings, was revealed for all thegroups examined. Thus, the level of chromosome-typeexchanges in the spectrum of chromosome aberrations
in children's lymphocytes varied from 0.0065 per cell
to 0.0133 in different villages. The population average
number of dicentrics/rings per cell in the children
from the evacuation zone was 0.0095, being 0.0006 in
the control.
Because of poor organization of radiation
monitoring in the first months after the Chernobyl
accident, the data of biological dosimetry havebecome more and more important. Biodosimetry

179

Table 3. Whole-body dose of liquidators and of a group of children evacuated from the 30-km zoneof Bragin district
Liquidators (1)Children from 30-km zone (our own data)
Whole-body dose (rem)% of examined
Whole-body dose (rem)% of examined
5-10
30
1-20
10
10-25
47
20-30
26
30-40
32
25-50
7.3
40-50
32
Table 4. Distribution of children by Iodine-131 content in thyroid and liver according to theγ-radiation exposure dose rate measured on 7-8 May 1986
% of examined with exposure rate
γ-radiation exposurein area of neckin area of liver
rate (µR/h)
10-49
16.1
50-99
27.5
45.2
100-20045
35.5
200-350
27.5
700
1.6
Table 5.

Radionuclides in organisms of children from Gomel region
Concentration of minimum/maximum value, Ci/lRadionuclides
Blood
Urine
Cesium-134
0.127х10-9 - 1.17х10-9
0.199х10-9 - 9.751х10-9
0.57 х10-9 - 2.5 х10-9
Cesium-137
0.13 х10-9 - 6.86х10-9-9-8
1.586х10-8 - 6.7 х10-8
Potassium-40
2.073х10 - 6.70х10-9-90.973х10-9 - 0.34 х10-9
Zirconium-95
0.97 х10 - 1.46х10-9-9Antimony-125
2.45 х10 - 0.21х10
Silver-110
6.7 х10-10- 5.6х10-11
Ruthenium-106
0.648х10-9 - 2.162х10-9
Cerium-144
0.648х10-8 - 2.23 х10-9
Zinc-65
1.189х10-9 - 1.1 х10-10
district and born before the catastrophe represent thesame groups of high genetic risk as the liquidators do.
Based on the data of measurement of radioactive
Iodine-131 content (7-8 May 1986) with portable
γ-irradiation dosemeters, only 27% of examinedpeople had the indices of exposure dose rate from 50
to 100 µR/h, the rest - from 100 and higher (Table 4).
The comparison of distribution of children by thewhole-body irradiation dose (on the basis of
cytogenetic examination) with internal dose forthyroid and liver by intake of radioactive iodine
isotopes into the organism for the same period,
showed the qualitative correspondence of both
distributions, i. e. with the shift to the side of higher
doses.
In order to confirm the presence of radionuclides
in children organisms, the direct analysis was carriedout of γ-radiating radionuclides in their biologicalmedia. The radionuclides in blood and urine of 37
children from the age of 4 to 15 from controlled areas
were studied at the Institute of Nuclear Energy of the
Academy of Sciences of Belarus by means ofγ-spectrometer “ADKAM-300” of “ORTEC” firm(USA). It was established that the next radionuclides

carried out on the basis of our findings by using
different standard curves (4,12-13) to evaluateabsorbed dose has shown that the recorded level ofchromosome aberrations in children evacuated fromthe 30-km zone of Bragin District and residing in
Bragin town corresponds to the dose of 200-500 mSv.
According to the data of the Institute ofRadiological Medicine (Belarus) based on themethods of physical dosimetry, radiation doses
received by residents of those districts for 1986 to
1988 did not exceed 155 mSv. The reasons of thediscrepancies in the estimated doses require further
thorough investigation .
According to the estimations of EC/IAEA/WHO/1, 11/ the highest doses were obtained by theliquidators of the consequences of the Chernobyl APS
catastrophe. The dose of whole-body irradiation
spreads as follows (Table 3): 30% of studied people
obtained 5-10 rem; the majority of liquidators namely, 47% - obtained 10-25 rem, and only 7.3% 25-50 rem /1/. Our data of biological dosimetry ofchildren from the 30-km zone show the shift of dose
distribution to the side of higher dose. Consequently,
the resettled children and the children living in Bragin180

Table 6.

Sample of the cohorts and observed yields of unstable chromosomal aberrations in 1986
No. of Cells with
No. ofAverage No. of children
No. of cells
aberr. (mean per
Settlement
dic/ring perage (y)examinedscoredcell
100 cells±SE)
Gomel region
Bragin district
v. Burki
7-14
6
1500
0.00555.7±0.6v. Mikulichi
7-14
17
4250
0.00636.8±0.4
Narovlya districtt. Narovlya
12
7
1750
0.00414.9±0.5
Minsk
Control 1985
18
3000
0.00061.4±0.2
Control 1986
174250
0.00061.5±0.2

Table 7.

Sample ofSettlement
Gomel region
Khoiniki district
t. Khoiniki
v. Novoselki
v. Rudnoe
Narovlya districtt. Narovlya
Control

the cohorts and observed yields of unstable chromosomal aberrations in 1987
No. of Cells with
No. ofAverage No. of children
No. of cells
aberr. (mean per
dic/ring perage (y)examinedscoredcell
100 cells±SE)

1-6
1-6
1-6

5
6
10

652
700
2050

3.7±0.7
7.6±1.0
9.8±0.6

0.00920.01430.0098

5
17

1250
4250

6.4±0.7
1.5±0.19

0.00640.0006by the liquidators. Regretfully, these dose
commitments were not taken into account before, andstill are not considered in recent assessment ofobtained doses values.
In the second stage (1987-1991), prolonged
external and internal irradiation for account oflong-lived radionuclides of cesium, strontium,
plutonium and others is the particularity of doseformation of the children living permanently on
radiocontaminated territories, in addition to the early
formed dose during the 1st stage including the thyroid
irradiation. It should be noted that in most cases thesame children were not examined in the samples.
The cytogenetic effect specific for radiation action
was also revealed in children in Bragin town
examined in 1988. A similar picture was observed in agroup of children in Bragin, examined in 1991 byusing the micronuclei method under cytokinetic block(10). The results confirmed the fact that an increased
level of chromosome aberrations remained inlymphocytes of the children. The number of detectedbinuclear cells with micronuclei was 5.3 times higher
than the number in the control. Such situation wasarisen, obviously, as a result of relatively balanced
state between formation of mutation anddisappearance both on the level of blood-producing
cells and on that of peripheral blood.

were present in blood: Cesium-134, Cesium-137,
Potassium-40,
Zirconium-95,
Antimony-125,
Silver-110. In the urine, the next radionuclides were
found besides above-mentioned: Carbon-14 (June1986), Ruthenium-106, Cerium-144, Zinc-65,
Zirconium-95 (1986-1987-1988). There were found intheexcrement:
Cesium-134,
Cesium-137,
Potassium-40 (Table 5).
Table 6 shows the principal results of cytogenetic
examination of children residing in Burki and
Mikulichi villages of Bragin district and Narovlya
town of Narovlya district of Gomel region. In allgroups, the number of cells with unstable aberrations dicentrics and centric rings - differed significantly
from the control one. The dose values calculated on
the basis of cytogenetic analysis of unstable
aberrations are proximate to the doses obtained by thechildren of Bragin town shown in Table 2.
Thus acute and prolonged irradiation obtained by
the children in Bragin district and Bragin town wereconsiderable in the first period (first weeks andmonths after the accident) and, obviously, conditioned
not only by short-lived isotopes (molybdenum,
technetium, lanthanum, barium), inert gases (xenon,
krypton) and I-131, but also by long-lived isotopes ofcesium, strontium and plutonium /1/. They arecomparable (and even higher) with the dose obtained181

time change of the dose structure due to increase ofinternal contribution to the total radiation dose.
According to available data, Cs-137 and Cs-134
contents in the examined children's organisms in
Khoiniki and Bragin districts, Gomel region, in
1987-1988 varied between 0.18 and 9.14 µCi (thedata were obtained by a whole body counter).
However, no correlation was revealed between the
total γ-activity of the organism and the yield ofchromosome aberrations. In this connection, thedecrease of dose rate from external (1, 17-18) andincorporated (1,18) γ-sources on one side, and theincrease of accumulation of α- (1, 19) and β-sources(1,20), on the other side, deserve attention.
The present results have shown that the level ofcytogenetic damages in human cells was higher in allradiocontaminated regions than in the control. Thus,
In the 2nd period the high tempo of mutation process
is characteristic in peripheral blood lymphocytes of all(100%) examined groups of children in Gomel region,
as well as the appearance of multiple aberrations incells of considerable part of children. The task offollowing surveys is the detailed characterization of
peculiarities in the 2nd and the 3rd periods ofmutation process dynamics in populations of somatic
cells of children in Belarus.

However, the more complicated picture ofmutation process was discovered in lymphocytes ofyounger children (age from 1 to 6). In the spring of1987 clinical and cytogenetic examination was carriedout of 21 children, aged 1-6 years, residing
permanently in the settlement of Khoiniki and in thevillages of Novoselki and Rudnoe, Khoiniki district,
Gomel region. The data obtained indicated anincreased level of chromosome aberrations in culturesof peripheral blood lymphocytes of these children's
groups: 3.7+0.7; 7.6+1.0; 9.8+0.5 % of aberrant
metaphases, respectively, as compared to 1.5-0.5% in
the control (Table 7). In all examined groups
chromosomal aberrations of exchange type were
found - dicentrics and centric rings - the frequency ofwhich was over one degree as high as that of control
group. The highest frequency of dicentrics and rings
as well as of cells containing such type of aberrations
was revealed in the children of Novoselki and Rudnoe
villages.
In spring of 1987 and 1988 cytogenetic
examination of the same children of Bragin and
Khoiniki districts was conducted in dynamics. The
first examination was carried out 12 months after the
Chernobyl nuclear accident. An interval between thefirst and the second examinations was also 12 months.
The increase of chromosome type aberrations from
5.2+0.5% in 1987 to 8.7+0.6% in 1987 (p<0.001) was
observed. A significant increase in the cell number
with 2-4 aberrations (from 16.4+3.3% in 1987 to
27.0+3.4% in 1988, p<0.01) was observed in the samechildren. Cells with 2 and more aberrations were notfound in the control.
It was shown experimentally that the external
irradiation dose of population in radiocontaminatedareas of Belarus had stabilized by 1989-1990;
meantime, strontium radionuclides content inorganisms of the people had increased 2.5-5 times ascompared with pre-accident period /1/. Probably, theincrease of the level of chromosomal aberrations withthe course of time and appearance of multiple injuries
in cells of small children are connected with thissituation.
Some "rogue" cells, which were named by Awa
and Neel (15) , were found by the present authors inlymphocytes of the children in Khoiniki and Bragin
districts almost a year after the Chernobyl accident.
Single "rogue" cells were detected by otherresearchers in various groups of children living in theradiocontaminated areas of Belarus (16). However,those authors do not ascribe emergence of "rogue"
cells to radiation exposure, though we consider thequestion doubtful.
More frequent occurrence of cells with 3 or 4
aberrations with increase of the time of children
staying in the radiocontaminated areas of Khoiniki
and Bragin districts seems to be associated with theConclusion
The presented data of cytogenetic investigation ofdifferent groups of children affected by ionizing
radiation as a result of the Chernobyl APS catastrophe
allow to make the following conclusions:- The use of cytogenetic method in theinvestigation of children born before the Chernobyl
accident made possible to reveal significant increaseof unstable chromosomal aberrations as comparedwith control groups.
- The absorbed dose of 200-500 mGy wasevaluated for the children from the 30-km zone of
Bragin district and Bragin town with the use ofmaterials of cytogenetic investigation conducted in
1986.
- It is shown that the level of unstable typeaberration in young children is rather increasing withthe course of time than decreasing. The appearance ofmultiaberrant cells in children several years after the
Chernobyl APS catastrophe, probably, testifies theeffect of dense ionizing radiation of plutonium and its
fission products on children.
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