Chromosomal Aberrations in Blood Lymphocytes of the Residents of 30-km
Chornobyl NPP Exclusion Zone
Larysa BEZDROBNA, Tetyana TSYGANOK, Olena ROMANOVA, Larysa TARASENKO,
Volodymyr TRYSHYN, Ludmila KLIMKINA
Institute for Nuclear Research, National Academy of Science of Ukraine,
Prospekt Nauki, 47, Kyiv-28, 03680, Ukraine: tel.+380 –44-265-47-36, interdep@kinr.kiev.ua

Abstract
A comparative сytogenetic examination of 33 self-settlers in the 30 km ChNPP Exclusion Zone
and 31 residents in villages of Yahotyn district, Kyiv region was carried out in 1998-99. The levels ofsoil contamination of their residential areas with 137Cs, 90Sr and 238,239+240Pu were 74–477 kBq/m2,
33–288 kBq/m2and 1.5-10.0 kBq/m2, respectively for the former, and 1.9–5.8 kBq/m2, 0.6–2.8
kBq/m2 and 0.01-0.05 kBq/m2, respectively for the latter. Using various data about the radiation
situation in the Exclusion Zone, the effective doses on whole-body of the self-settlers were estimatedto be 30–333 mSv for the whole residing period after the accident. The mean frequencies of aberrant
cells and chromosomal aberrations for the Zone self-settlers were significantly higher than those forthe residents in Yahotyn district, while the values of the latter group were found to be above thespontaneous levels reported in literatures. The individual variability in the distribution of the same
indices was significantly larger for the self-settlers than for the Yahotyn residents. The comparedgroups also differ in the distribution of aberrations in cells. A repeated examination of 20 Zone selfsettlers was conducted in 2001. A significant decrease in chromosome type aberration frequency was
found at the expense of fragments frequency decrease. However, the total frequency of chromosomal
aberrations didn’t differ in 1998-99 and in 2001.

INTRODUCTION
After the Chornobyl accident on 26th of April 1986, the territory within a 30-km radius from ChNPP
was separated as Exclusion Zone. The people residing in this area were evacuated during 4-7th of May.
However, right from the first days and weeks after the evacuation some people have been returning to theZone villages without permission. In addition, nearly 100 people were not evacuated at all. They are called“self-settlers”. The number of them was about 500 people in 1986 in the Ukrainian part of the Exclusion
Zone territory, 1200 – in 1988, 660 – in the end 1998 and 477 – in 2001. Up to 80 % of them are old age
pensioners. They lead relatively isolated life, farm and consume mostly food products grown in Zone,
which determines their permanent external and internal irradiation.
It is a well-known fact that one of the most significant effects of radiation is destabilization of genetic
structures of somatic cells leading to an increase in the risk of somatic diseases, first of all, of cancers. In
order to investigate the efficiency of long-term permanent suprabackground radiation in the conditions of
Exclusion Zone we have been conducting periodically cytogenetic examinations of self-settler groups
from 1995. The first examination was carried out using micronucleus test on cultures of peripheral blood
lymphocytes. A significant increase was revealed in the micronuclei frequency in cells of the Zone selfsettlers of the age up to 55, compared to that of Kyiv residents of the same age [1,2]. These findings
pointed out an expediency of further investigations. In this work we present the results of chromosomal
aberration frequency in blood lymphocytes of ChNPP Exclusion Zone residents investigated in the end of
1998 – beginning of 1999, and in 2001.

277

SUBJECTS AND METHODS OF STUDY
The subjects of examination
In 1998-1999 we examined 33 people residing in the villages in Exclusion Zone, locatednorthwestward (Stari Shepelychi, Rudnya Illinetska, Lubyanka) and southeastward (Opachychi, Kupovate,
Horodyshche, Paryshiv) of ChNPP. These people returned to their homes in Exclusion Zone mostly inJune 1986 - April 1987 after the evacuation. For comparison we have simultaneously examined 31 people(control group) from the inhabitants of the villages in Yahotyn district, Kyiv region. The climatic andsocioeconomic conditions as well as health care of both examined groups were analogous. Table 1
represents the data on the radionuclide contamination in soil of residing areas of the people observed. The
group of comparison was formed to match age, sex and smoking status of the ChNPP Exclusion Zone selfsettlers (Table 2). None of the persons of the control group had had any conscious contact with radiation
factor except for routine medical radiological diagnostic procedures and had not been exposed tochemotherapy. In 2001 20 people among the 33 Zone self-settlers observed in 1998-1999 were repeatedly
examined. At the moment of obtaining of blood samples no one from those examined had any acute illness
or exacerbation of chronic diseases. The participation in examination was voluntary. A special
questionnaire was offered to the examined persons and all data obtained were entered into a database.
The cytogenetic protoco
Venous blood samples were obtained in field conditions, either in the places of residence of theTable 1. Density of radionuclide contamination in soil in ChNPP Exclusion Zone and villages in
Yahotyn district, Kyiv region, kBq/m2.
13790
238.239+240
Cs
Sr
Pu
RegionInhabited locality

ChNPP Exclusion
Zone

Yahotyn district,
Kyiv region

Rudnya Illinetska

129.5±25.9

70.3±22.2

1.5

Lubyanka

407.0±101.7

144.3±31.7

5.9Stari Shepelychi

477.3±118.9

288.6±85.1

10.0

Paryshiv

115.4±22.0

54.0±11.3

2.2

Opachychi

214.6±59.2

133.2±25.9

5.6

Kupovate

107.0±22.2

44.4±14.8

3.0

Horodyshche

74.0±14.2

33.3±6.3

2.6

Sulymivka, Chernyakhivka

1.9 – 2.9

0.64

0.01

Lozovyi Yar, Chervone

2.6

0.96

0.04

Panfily

5.0

0.8

0.04 – 0.1

Kapustyntsi

5.0

0.8

0.02 – 0.04

Yahotyn

2.9 – 5.8

0.9 – 2.8

0.03 – 0.05

Sex

Smoking status

Table 2. Characteristics of examined groups.
Group
ChNPP
Exclusion
Zone
Yahotyndistrict,
Kyiv region

Range of effective equivalentdoses, mSv
Red bone
Whole bodymarrow

NumberofpersonsAge(range,mean),
in yearsF

M

Nonsmokers

Smokers

30 – 333

13 - 630

33

24 – 6853.9±1.7

17

16

28

5

-

-

31

23 – 7251.5±2.2

18

13

26

5

278

examined people or in rural outpatient clinics. All samples were drawn into vacutainers containing heparinas antocoagulant. Samples were transported within eight hours in Kyiv to Laboratory of Radiobiology ofInstitute for Nuclear Research, National Academy of Science of Ukraine.
Lymphocytes culture and cytogenetic slide preparation were conducted according to [3]. 0.25 ml ofwhole-blood have been cultivated in 3 ml of RPMI-1640 medium supplemented with 15% fetal bovine
serum with 1.5 % phytohaemagglutinin-Р (Sigma, USA) for 48 h at 37°С in darkness. Colchicine in final
concentration of 7.5mg/ml was added to the culture 3 hours prior to fixation. The slides were preparedfollowing a standard technique, using for hypotonia - 75mМ solution of КCl and for fixation – ethanolacetic acid (3:1), for chromosome staining - Giemsa stain (2 % solution). All slides were encoded. The
slides were studied with oil immersion using x900 magnification. On the average 380 metaphases meeting
the required standards from every person were studied. Analysis was conducted by means of visual partial
karyotype determining. We counted all chromatid type aberrations including chromatid fragments andchromatid exchanges, and all chromosome type ones, such as paired acentric fragments (including
isochromatid deletions), interstitial deletions, dicentric chromosomes (dic.) and centric rings (c.r.),abnormal monocentrics, which could emerge as the result of terminal and interstitial deletions, reciprocaltranslocations and insertions. The blank gaps were not taken into account.
Doses estimation
Individual effective equivalent irradiation doses (both external and internal on whole body and redbone marrow) of the Zone self-settlers were determined by calculational methods. Dose reconstructing
was based on the data of the mean density of soil contamination of residential areas with radionuclides of
137
Cs, 90Sr, 238,239,240Pu and 241Am together with the time and duration of personal residence in Zone in the
post-accident period. Also the data were used from representative measurements of exposure dose rate inhouses and homesteads; 137Cs and 90Sr content in nutritional products of local origin; individual 137Cs
content in the bodies of examined people measured by a whole body counter.
Statistical Analysis
Characteristic distribution of chromosomal aberrations among the examined persons was determinedby means of χ2 test. Significance of the differences between the groups was estimated with χ2-test,
Wilcoxon-Mann-Whitney U-test, Students t-criterion and Fisher test. Age-relation was estimated bymeans of the Spearman ranks correlation coefficient [4,5].
RESULTS AND DISCUSSION
Cytogenetic examination in 1998-1999
Frequency of aberrant cells and chromosomal aberrations:
Distribution of the examined persons by the number of chromosomal aberrations per 100 analyzed
lymphocytes is shown in Fig. 1. The obtained distributions fit the normal type in both of the Zone selfsettlers and the village residents of Yahotyn district: for the Yahotyn district group – χ2<χ20.01 and for theZone group – χ2<χ2 0.05. As is seen from the bar chart (Fig. 1), one third of the Zone self-settlers showed
the frequency of chromosomal aberrations exceeding the maximum value of this parameter in thecomparison group. The comparison of individual distributions by the number of aberrant cells andchromosomal aberrations per 100 cells showed a significant difference between two groups (χ2>χ20.01).
However, the comparison utilizing the U-criterion revealed that the distribution of persons by thechromosomal aberrations frequency statistically significantly differs in two groups only when the resultsof persons younger than 60 years old were compared (р < 0.001). The inter-individual variation(dispersion) and the mean group frequency of aberrant cells and chromosomal aberrations in peripheral
blood lymphocytes were significantly higher for the Zone self-settlers than for the Yahotyn district
inhabitants (Table 3). V.Yu. Nugis [6] observed that the increase of individual variation in frequencies of
279

45
40
Subjects, %

35
30
25
20

ChNPP exclusion zone

15

Yahotyn district

10
5
0

1

3

5

7

9

11

CA per 100 cells

Fig. 1. Distribution of examined persons by the number of chromosomal aberrations (CA) per
100 cells.
chromosomal damages in the population signals chronic exposure to genotoxic factors. It is noteworthy
that higher levels of aberrant cells (3.20±0.15 %) (mean±SEM, here and below) and chromosomal
aberrations (3.51 ±0.17 %) than those usually reported for the "clean" regions were found in the
inhabitants of the Yahotyn district. According to a generalized data on the spontaneous level ofmutagenesis for the year 2000 reported by our Russian colleagues, the frequencies of aberrant cells andchromosomal aberrations in blood lymphocytes are 2.13±0.08 % and 2.21±0.14 %, respectively [7]. The
data of the same authors also indicates that the mean frequency of chromosomal aberrations in the early
70-th was 1.19±0.06 % [8]. A generalized cytogenetic monitoring of healthy population of Ukraine up to1986 testifies that before the Chornobyl accident the frequency of aberrant cells and chromosomal
aberrations in peripheral blood lymphocytes of the Ukrainian population were 1.43±0.16 % and1.47±0.19 %, respectively [9]. The above allows us to assume that the registered parameters ofmutagenesis in Yahotyn district are caused not only by the age of the examined persons (65% of themwere 50+ according to Zone self-settlers group age structure), but also by general deterioration of theenvironment during the period after 1986.
Two persons from the Exclusion Zone and one Yahotyn district resident had one multiaberrant celleach (we referred cells having more then 7 aberrations to multiaberrant).
Age dependency of chromosomal aberrations:
Age dependency of chromosomal aberrations frequency in blood lymphocytes was analyzed by themethod of the Spearman ranks correlation coefficients. A strong age dependency was observed in thegroup of Yahotyn district: the Spearman ranks correlation coefficient was 0.71 (р < 0.0005), while it was
Table 3. Frequency of aberrant cells and chromosomal aberrations per 100 lymphocytes from
ChNPP Exclusion Zone and Yahotyn district residents.
(individual range; mean ±SD).
NumberNumber of
Chromosome
Multiaberrant
Group
Aberrant cellsofanalyzedaberrations
cells
personscells
ChNPP Exclusion
Zone

33

11789

1.92 – 10.20
5.02±1.95

2.24 – 10.80
5.32±2.10

0.017±0.066

Yahotyn district,
Kiev region

31

12273

1.82 – 5.50
3.20±0.84

1.82 – 6.00
3.51±0.97

0.009±0.25

280Table 4. Frequency of various types of chromosomal aberrations per 100 cells in the Exclusion
Zone self-settlers and the residents in Yahotyn district.
(individual range, M±SEM )Chromatid type
Chromosome type
Group

ChNPP
Exclusion
Zone
Yahotyndistrict,
Kyiv
regionfragments

dicentrics + centric rings
Interwithsticial.
without
total
deletions fragment fragment

abnormalmonocentrics

total

0-1.3

0 - 1.4

0.3-5.6

0.10
±0.03

0.33
±0.06

0.23
±0.05

2.16
±0.24

0 - 0.5

0 - 0.25

0 - 0.5

0 - 0.8

0.3- 2.5

0.08
±0.03

0.05
±0.02

0.13
±0.03

0.12
±0.03

1.18
±0.13

breaksexchanges

total

0.6-5.6

0-1.0

1.0-6.6 0.3-4.9

0-0.5

0-1.0

0- 0.9

3.01
±0.24

0.13
±0.04

3.14
±0.24

1.59
±0.20

0.02
±0.02

0.22
±0.05

1.0- 4.0

0 - 3.0

1.0-4.0

0 - 2.2

0 - 0.5

2.31
±0.12

0.02
±0.01

2.33
±0.12

0.89
±0.12

0.04
±0.02

–0.23 (р> 0.05) for the Zone group, i.e. in the latter group even some tendency to an inverse relationshipwith age is observed. It might be caused by the influence of additional factors in ChNPP Exclusion Zone,in particular, by the influence of radiation factor and perhaps by lower sensitivity of the elderly people(60+) to it. The similar results were obtained in our previous studies in which micronucleus test was
utilized [2].
Ratio of chromosomal aberration types:
Table 4 shows the results of the analysis of frequency of various types of chromosomal aberrations inperipheral blood lymphocytes. Correlation between chromatid type and chromosome type aberrations inboth groups corresponds to the ratio reported in the literature for spontaneous mutagenesis (2:1 – 1.5:1)[8]. The proportion of chromosome type aberrations in self-settlers’ lymphocytes does not significantly
differ from that of the control group; 39.2±2.8 % and 33.6±2.9 %, respectively (t=1.4, р=0.16).
The induction of chromosome type aberrations is known to be characteristic for radiation exposure.
Their mean group frequency in lymphocytes of the self-settlers was increased 1.8-fold compared with thatof the Yahotyn residents, but at the same time there was a 1.3- fold increase in the frequency of chromatid
type aberrations.
Chromosome type aberrations:Exchange rearrangements are the most specific markers of radiation exposure. Unstable chromosome
exchanges (dic. and c.r.) were detected in 60 % of the Zone self-settlers and in 45 % of the Yahotyn
district inhabitants. In the Zone self-settlers’ cells unstable exchanges occurred on the average 2.5 times
more often than in the control group of Yahotyn district. In both groups the majority of unstableexchanges were accompanied by fragments. Routine staining of stable chromosome exchanges (abnormal
monocentrics) also revealed a significant increase of mean group frequency in the Zone self-settlers (1.9fold) with one third of the examined self-settlers and 16 % of Yahotyn district residents simultaneously
revealing both stable, and unstable aberrations.
Reported spontaneous levels of unstable chromosome exchanges vary within the range of 0.03 % and
0.3 % [7, 10-12]. According to [11,13] the mean population frequency of the total dic. and c.r. is taken as
0.13 % – 0.16 %. Up to 1986 these damages were registered in the rural population of Ukraine with thefrequency of 0.05 per 100 metaphases [9]. In our research we have revealed dic. and c.r. in the control
area residents with the frequency of 0.13±0.03 %, i.e. 2.6 times exceeding the pre-Chornobyl accident
level for agricultural regions of Ukraine, but comparable with the mean population one.
The frequency of paired fragments per 100 metaphases was 1.59 ±0.20 in lymphocytes of the Zone
self-settlers versus 0.89±0.12 in lymphocytes of the control group, while the mean pre-Chornobyl accident281

level for the rural population of Ukraine was 0.47 [9]. Reported spontaneous levels of paired fragments are
0.25 – 0.65 per 100 cells [7, 10, 14]. It should be noted that in our research the increase of frequency ofpaired fragments in the Zone self-settlers is caused to a great extent by the excess of the number ofisochromatid deletions. In addition in the course of analysis attention was paid to the fact that in cells of
the Zone self-settlers some paired fragments were shown to be much longer than those usually observed.
Chromatid type aberrations:
As seen in Table 4, a significant increase of chromatid type aberrations per 100 metaphases of
3.14±0.24 was registered in the Zone self-settlers compared with the value of 2.33±0.12 in Yahotyn
district residents. The pre-accident level for the rural population and the currently reported spontaneouslevels of this indices were 1.05 [9] and 0.6 –1.5 [7, 10, 14], respectively.
Thus, in the conditions of chronic irradiation the frequency both of chromosome type (at the accountof single- and two-hit damages) and chromatid type aberrations increased in lymphocytes of the Zone
self-settlers. The elevated frequency of single-hit acentrics in the presence of two-hit dic and c.r. ischaracteristic for continuous exposure to low dose rates of low-LET radiation [15]. Increase of theacentrics frequency was revealed in cells of persons having been exposed to occupational irradiation for
20 years [10].
It is difficult to interpret the causes of the increase of chromatid type aberrations, which ischaracteristic for non-radiation mutagenesis, in the Zone self-settlers. Probably, the influence of chemicalmutagenes in places of the Zone self-settlers’ residence is not worse than in the Yahotyn district villages.
Since the time of the accident no pesticides or other fertilizers have been utilized in the Exclusion Zone,
while traces of the pre-accident soil contamination are still found. As for the salts of heavy metals wedetermined the elevated content of zinc and cadmium (in comparison with standard index) in crops grownin the self-settlers’ homesteads. The levels of air contamination in the villages by nitrogen and carbon
oxides, ozone and heavy metals aerosols do not exceed maximum allowable concentration [16]. It is
unlikely that the self-settlers use more medications in comparison with the Yahotyn district residents.
The following assumptions were made in the literature concerning the increase of chromatid typedamages due to prolonged irradiation: a) reparation of chromosome damages in conditions of low dose
rate irradiation results in partial transition of chromosome type aberrations to the class of chromatid typeaberrations [17]; b) the low doses of radiation cause instability of the chromosome system, which
increases sensitivity to other forms of mutagenes, such as viruses, chemical factors [18]. Data are available,according to which radionuclides in low doses affect cells more likely as chemical mutagenes, toxins than
2.5

0.5

0.3

2

0.4

0.25

1.5

0.3

1

0.2

0.5

0.1

0.2
0.15

0

0

1

2

3

0.1
0.05
1

2

3

0

1

2

Fig. 2. Distribution of aberrant cells by the number of aberrations per cell in lymphocytes of thegroups of ChNPP Exclusion Zone self-settlers (■) and the residents of Yahotyn district(□). % of the total number of examined cells.
-Left: total chromosome type aberrations-Center: total chromosome type exchanges-Right: unstable chromosome type exchanges282

as radiation sources [19].
Distribution of aberrations in cells:
The important information for finding out the type, dose and uniformity of mutagenic exposure is the
distribution of aberrations in cells. In both groups of the Zone self-settlers and the Yahotyn district
residents we have found persons having cells with two and three chromosome type aberrations. Somepersons had even two or three such cells (two self-settlers and four persons from Yahotyn district ).
In such cells of the Yahotyn district residents aberrations are represented mainly by acentrics, whichmight be caused by the past viral infection [20] without clinical manifestations. Among the Zone selfsettlers’ cells with several chromosome type aberrations, cells prevail with 2-3 chromosome exchanges.
Six self-settlers had such cells, and in five of them cells with 2 unstable exchanges were revealed, which ischaracteristic for exposure to radiation factor. One cell with two unstable exchanges with accompanying
fragments was also found in one of Yahotyn district residents (27 years old), which probably testifies tothe fact of some unaccounted irradiation in the region considered “radiation clean”.
The comparison of the distributions of aberrant cells by the number of aberrations per cell is shownin Fig.2 for all chromosome type aberrations, all chromosome type exchanges and unstable chromosome
type exchanges. A significant inter-group differences was revealed by χ2 criterion (χ2>χ20.01 ) between the
Yahotyn district residents and the Zone self-settlers.
Cytogenetic examination in 2001
Time trend of chromosome aberration:
In order to investigate the dynamics of cytogenetic effects in the Zone self-settlers, 20 people from33 already examined in 1998-99 were repeatedly analyzed in 2001. As it is seen in Table 5 this analysis
has not revealed any changes in the mean group frequency not only of quantitative aberrations(metaphases with 47 chromosomes and tetraploids) but also of the total qualitative chromosome damages;
the frequencies of aberrant cells and the number of aberrations per aberrant cell.
Table 5. Dynamics of cytogenetic effects in the peripheral blood lymphocytes of the ChNPP Exclusion
Zone residents. (Number of examined persons - 20 )Number of
Frequency per 100 cells (individual range, M±SEM )NumberNumber ofYear ofpersonsofaberrations
Metaphases
examinawith
Aberrant“Rogue” Chromosome per aberrant
analyzedwith 47
Tetraploids
tion“rogue”
cells
cells
aberrations
cells
cell
chromosome
cells
2.2–10.8
1.9–10.2
1.06
7
0.14
1998-996978
0.73±0.14
0.48±0.10
5.79±0.55
5.44±0.52
2.2–10.4
2.2–9.5
1.08
4
0.09
2001
7923
0.75±0.10
0.39±0.07
5.41±0.49
4.99±0.41

Table 6. Dynamics of frequency of different type chromosomal aberrations in the blood
lymphocytes of the ChNPP Exclusion Zone residents. (Number of examined persons - 20)
Frequency per 100 cells ( individual range, M±SEM )Year ofexamination

19981999
2001

Chromatid type

Chromosome typebreaksexchanges

total

fragments

inerstitialdeletions

1.0–5.6
3.0±0.33
1.2–8.1
3.53
±0.40

0–1.0
0.16
±0.07
0–0.9
0.29
±0.07

1.0–6.6 0.3–4.9
3.17
1.77
±0.33 ±0.30
1.2–9.0 0–2.0
0.79*
3.82
±0.45 ±0.14

0–0.5
0.025
±0.025
0–0.4
0.07
±0.03

* P<0.05

283

dicentrics + centric rings
withwithout
fragment fragment
0–0.9
0–0.5
0.29
0.10
±0.081
±0.04
0–1.0
0–0.8
0.18
0.27
±0.06
±0.06

total
0–1.3
0.39
±0.09
0–1.4
0.45
±0.09

abnormaltotal
monocentrics
0–1.4 0.3–5.9
0.32
2.58
±0.08
±0.35
0–0.9 0.2–2.8
1.63*
0.25
±0.16
±0.06

Studying the dynamics of different types of chromosome damage showed a significant decrease in
the mean group frequency of chromosome type aberrations at the expense of a decrease in the yield offragments, i. e. single-hit lesions. No alteration was found in the mean group frequencies of two-hit
chromosome exchanges induction (Table 6).
“Rogue” cells:
We also analyzed the dynamics of “rogue” cell incidence, using the conventional definition of“rogue” cell proposed by M. A. Pilinskaya [21]. It has been proposed to refer to the cell as “rogue”, whencontaining more than one lesion with at least one of them being chromosome type exchange aberration.
Table 7 shows an aberration spectrum seen in “rogue” cells. “Rouge” cells of the Zone residents contained
mostly 2-3 chromosome exchanges. Some self-settlers were indicated to have several “rogue” cells. There
were also “rogue” cells similar to those described by Awa and Neel [22] that contain policentrics and“double minutes”. It is important to note that two individuals (encoded #15 and #29) were shown to have“rogue” cells in 1998 as well as in 2001. Individuals encoded #1 and #2 belonged to the same family. Oneof them exhibited “rogue” cells in 1998 and the other in 2001. In the inhabitants of the control Yahotyn
district “rogue” lymphocytes mostly contained one chromosome exchange per cell.
The mean frequency of “rogue” cell incidence among analyzed lymphocytes in the first and second
examinations of groups involving 20 individuals were 0.14 and 0.09 per 100 cells, respectively (Table 6).
The frequency of these cells among lymphocytes analyzed in 1998-99 from the whole group of selfsettlers consisting of 33 individuals was 0.10 per 100 cells. Therefore, this value was generally similar to
Table 7. Aberration spectrum in “rogue” peripheral blood lymphocytes of Exclusion Zone
self-settlers and residents of Yahotyn district, Kyiv region.
238,239,240

Group

Pu,
Am,
kBq/m2
241

Coded No.
1

1-2

Year of examination
1998 – 1999 (n=33)
2(dic+ace);tr, dic+ace
tr, del, ace;
2tr, cr, dic+ace, 2min;tric, dic+ace, min

2

ChNPP
Exclusion
Zone

1–2

8

dic+ace, tr, del

1– 4

19*

dic, del29

tr, 2(dic+ace)

15
12

tr, acedic, del62(dic+ace)

21

dic+ace, del2–4

2 – 10
4 – 10
10 – 40

32
30*
18

1y
Yahotyn
11ydistrict,
12y
Kyiv region
0.02 – 0.1
18y
20y
n=31
26y
27y
* - individuals examinated in 1998-99 only.

2001 (n=20)

tetrac, min, 2ace;
2tr in tetraploid;
dic+ace, tr

2dic, dic+ace
2dic, del, 10ace;
2dic
2(dic+ace)
dic+ace, 2ace
dic+ace, deldic, ace
dic+ace, ace
cr+ace, dic+ace
dic, 2deltr, ace284the values of both investigation periods for 22 self-settlers, and 1.5-fold higher than that for Yahotyn
district residents' lymphocytes (0.06 per 100 cells).
Cells containing multiple chromosome exchanges had been also found in residents of Belarus andRussia [23, 24]. According to [21] no “rogue” cells had been found in course of the examination of rural
population of Ukraine before the Chornobyl accident.
According to the reported data, cells with two unstable exchanges are observed in acute general
irradiation starting from a dose of 100 cGy onward [25]. Effective whole body doses of irradiation for the
self-settlers due to external and internal irradiation, reconstructed by us till the beginning of 1999, did notexceed 33 cSv and on red bone marrow - 63 cSv. Probably, emerging of cells with multiple chromosomal
aberrations under low dose radiation exposure could be connected with the presence of hypersensitive
lymphocyte subpopulation [26]. In the case of the Zone self-settlers we intend most probably to assume
that the incidence in blood of extremely “rouge” cells is due to non-uniform internal irradiation owing togetting into the body of α- emitting transuranium elements. It is likely that 238,239,240Pu and 241Am get into
the body first of all with aerosols and probably with vegetative nutrition products. 241Am content isaccumulating on the Zone territory following β-decay of 241Pu. During the post-accident years its amountincreased from 0.003 to 0.04 PBq [27]. At the period of our investigations the level of soil contamination
by 241Am in the Zone appeared to coincide with the contamination level by all Pu-isotopes. Taking thissituation into account, researches connected with transuranium elements content, particularly 241Am, as
the most available of thosein nutrition products of the Zone residents are very important.
CONCLUSION
The results of our examination of ChNPP Exclusion zone self-settlers testify to the destabilizing
effect of continuous low dose rate irradiation on genetic structures of somatic cells in conditions of livingin the areas contaminated with radionuclides and to the expediency of cytogenetic monitoring of the
population. The data obtained from studying of cytogenetic effects dynamics show that 12-15 years after
the accident the level of chromosome damages in ChNPP Exclusion Zone self-settlers’ lymphocytes
comes to a plateau. The comparison of the results of cytogenetic examination of Yahotyn district
inhabitants with the reported data on spontaneous levels of chromosomal damage allows us to assume theactivation of mutagenesis in this region.
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