Genetic Consequences of the Chernobyl Accident for Belarus Republic
Gennady LAZJUK, Yukio SATOW*, Dmitri NIKOLAEV, Irina NOVIKOVA
Belarus Institute for Hereditary Diseases, Minsk 220053, Belarus
Hiroshima Bunka Women’s Junior College, Asaminami-ku, Hiroshima 731-01, Japan
uncertainties. Only direct methods, which count thefinal effect, with all their drawbacks, can provide
accurate information on genetic losses. We haveestimated possible genetic consequences for theresidents of Belarus Republic due to the Chernobyl
accident by studying malformations found in legalmedical abortuses and by counting congenital
anomalies in fetuses and newborns.

IntroductionNumerous studies have shown that agreat number of residents in Belarus, Russia and theUkraine were exposed to radiation due to radioactive
nuclides ejected from the Chernobyl reactor, which
increased genetic load, manifested in particular, as
chromosome aberrations (Lazjuk G.I. et al., 1990;
Pilinskaya M.A. et al., 1994; Sevankaev A.V. et al.,1995). The increase was registered for unstable andstable, chromatid and chromosome types of aberrations(Stepanova E.I., Vanyurikhina E.A. 1993, Vorobtsova
I.E., Bogomazova A.N., 1995, Sevankaev A.V. et al.,1995). Proceeding from the findings that the number ofdicentric and ring chromosomes (which are the mainindicator of radiation mutagenesis at chromosomelevel) was increasing simultaneously with the increaseof other aberrations which are common for chemicalmutagenesis (Pilinskaya M.A. et al., 1994; LazutkaJ.R., 1996) and from the fact that actual mutation
incidences exceeded the calculated figures for thedoses obtained (Pilinskaya M.A. et al., 1992,Sevankaev A.V. et al., 1995), one can not exclude thepossibility that chromosome aberrations found in thepopulation affected by the Chernobyl disaster arecaused not only by ionizing radiation but also by
various mutagenes, and the doses based on physicaldosimetry could be underestimated.
It is quite obvious that the level of chromosome
aberrations can be used as a biological indicator of
harmful mutagenic effects on the organism. However,
the method is not yet capable of (or only partially suitedfor) detecting the actual genetic risk even in the cases
when aberrations are found in gametes, not inperipheral blood lymphocytes as usually done. The
study of the dynamics of genetic losses, as spontaneousabortions and perinatal death due to inheritedanomalies, and the study of the dynamics of malformed
children births are probably the most reliable methods
to determine genetic risk due to any mutagenic factor
affecting the population, including ionizing radiation.
This is related to the fact that there are a great sequenceof events (gamete selection, preimplantation andembryonal death) occurring between gamete mutations(to say nothing about a somatic one) and births ofchildren with congenital diseases. It is nearly
impossible to count them and this leads to various

Dynamics of anomalies found in legal medial
abortuses
The incidence of anomalies has been studied inembryos and fetuses obtained from pregnant women in
Minsk-city (control) and in the areas under thoroughradiological control (TCA). Contaminated areas inGomel and Mogilev regions with 137Cs of 15 Ci/km2(555 kBq/m2) and more are placed into the category ofthoroughly controlled areas. Five to 12 week abortuses
were obtained through curettage and examined bypathoembryologists at Belarus Institute for Hereditary
Diseases. The investigation was carried out using
dissection under a stereo-microscope. If required, serial
histological sections were additionally studied. In allcases the age of embryos or fetuses was determinedusing the system developed at the Carnegie Institute.
Malformation frequency was determined not for thenumber of examined abortuses, but for the number of
examined organs, since after the curettage not allorgans were always suitable for the examination.
Moreover, since some anomalies are observed bypersistence of the structures characteristic of particular
stages of embryonic development, when counting
particular anomaly, only embryos whose age exceeded
the age of corresponding physiological persistence
were taken into consideration. All anomalies found at
dissection and histological examination have beenrecorded. In total, 33,376 abortuses, including 2,701
abortuses obtained from TCA, have been studied forthe period from 1986 (the second half) to 1996.
The results are partially presented in Table 1. As thetable shows, malformation frequency for legal medical
abortuses from TCA is considerably higher than thatfrom Minsk-city, which has been observed for both
periods of pre-Chernobyl 6 year and post-Chernobyl 11year. It should be mentioned that the total frequency of
7.21 in TCA during 1986 to 1995 has been found lower
than it was in 1992 (9.87) (Lazjuk G.I. et al., 1996).
Significant increase has not been found forThis report was published in Gijutsu-to-Ningen, No.283,pp.26-32, Jan/Feb. 1998 (in Japanase).

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Table 1 Frequency of Malformations Found in Induced Abortuses in Belarus
Regions under study
Minsk
1980-1985
1986-1996

MalformationsTCA
1986-1995

The number of abortuses examined

10,16820,507

2,701

Malformation frequency to the number of examinedsamples (%)
including:

5.60

4.90

7.21*

CNS anomalies

0.32

0.53

0.54

polydactyly

0.63

0.53

0.79

reduction limb defects

0.07

0.10

0.28

*

- significant difference (P<0.05)

by ionizing radiation due to the Chernobyl accident.
However, dependence on contamination withradioactive Cs can not be excluded for the 1% increaseover the control (51-50) recorded in 54 regions and for
33% increase (83-50) in 17 regions.

anomalies most characteristic for radiation exposure;the central nervous system and anomalies with thegreatest contribution of de novo mutations (polydactylyand reduction limb defects). However, tendency of
their number increase is rather obvious, especially forreduction limb defects.

Such increase can be explained by at least 4 factors.
a) Higher birth frequency of malformed children after
the Chernobyl accident is considered to be not atrue increase of anomalies in embryos, but only anartifact, the result of more complete registration, inother words, it is the result of closer interest in«disaster areas»,b) teratogenic effects of embryo exposure toradioactivity from the Chernobyl Nuclear Station,c) the result of gamete mutations in either parent due
to additional exposure on gonads, ord) the result of a complex of negative factors
including the Chernobyl disaster (radiation plus
chemical pollutants, poor nutrition, alcoholism).
Artifactual origin of increasing number of CM
under the long-term National Monitoring, as it is inBelarus, is virtually excluded, firstly, by counting of
only unambiguously diagnosed CM, secondly, byconstant control of registration completeness by theresearchers from Belarus Institute for Hereditary
Diseases, thirdly, by practically equal frequencies
before the Accident in various regions and, finally, by
the correlation between the increase of CM frequency
and the level of contamination.
Teratogenic effect is excluded, since the doses
received by intrauterine fetus for a teratogenic
terminational (or crucial) period were below threshold.
No woman who gave birth to a malformed child, hasreceived over 55 mSv for the period starting from theaccident till the end of the 1st trimester. The 1sttrimester includes the terminal period of neural tubedefects,
themostcharacteristiccongenital
malformation for radiation teratogenesis. No
significant increase of nervous system CM has beenfound in newborns and abortuses recorded in theNational Monitoring (Tables 1 and 2).

Dynamics of congenital malformations innewborns
The birth frequency of children with congenital
malformations (CM) was studied based on the National
Monitoring which has been functioning throughout thewhole Republic since 1979. Congenital malformations
unambiguously diagnosed in neonatal period areregistered irrespective of the level of technical facilities
of a medical institution. In each case of congenital
malformation, the diagnosing physician fills in a
special form registration, which is sent to the Minsk
Genetic Center. The scientists of Institute for
Hereditary Diseases verify the record completenessand diagnosis during regular trips to the areas, orduring consultations with families at the Center.
Anencephaly, severe spina bifida cystica, cleft lips
and/or palate, polydactyly, reduction limb defects
leading to disability, esophageal atresia, anorectalatresias,
Down’ssyndromeandmultiple
malformations are registered both in stillborns and infetuses obtained through induced abortion after
prenatal diagnostics. The results are presented in Table
2 for the 137Cs contaminated areas and for the control.
Thirty regions, where 137Cs contamination density was
found to be less than 1.0 Ci/km2, were taken as thecontrol.
It is clearly seen that the total CM frequency
increased both in the control and in the areas
contaminated with 137Cs. Moreover, as the level ofcontamination becomes higher, the greater increase of
malformed children birth is seen. While the 50%
increase is shown in the control, it is 83 % in the areas
with contamination over 15 Ci/km2. It is quite obviousthat the increase of CM in the control can not be caused
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Table 2 Incidence of Obligatory Registered Malformations in Belarus for 1982 to 1995
(per 1000 neonates)
Malformation

Anencephaly
Spina bifida
Cleft lip and/orpalate
Polydactyly
Limb reduction
defects
Esophageal atresia
Anorectal atresia
Down’s syndrome
Multiple
malformations
Total

Areas contaminated with Cs-137
22>1 Ci/km>15 Ci/km
17 regions
54 regions
1982-1985
1987-1995
1982-1985
1987-1995
0.28
0.44
0.24
0.64*
1126
48
226
0.58
0.89
0.67
0.95*
2353
132
335
0.63
0.94
0.70
0.92*
25
56
137
324
0.10
1.02*
0.30
0.66*
46160
232
0.150.49*
0.18
0.35*
629
36
123
0.08
0.08
0.12
0.15
35
23
53
0.05
0.08
0.08
0.10
25
16
35
0.91
0.84
0.86
1.03
3650
170
362
1.04
2.30*
1.41
2.09*
41
137
277
733
3.87
7.07*
4.57
6.90*
151
422
899
2423

Control(30 regions)
1982-1985
0.35
23
0.64
42
0.50
33
0.26
17
0.20
13
0.11
70.03
20.63
41
1.18
77
3.90
255

Percent increase
before and after
83
51
Chernobyl*Significant difference (p - 0.05) between the values for 1982-1985 and for 1987-1995.

1987-1995
0.49
630.94*1200.95*
1210.52*66
0.20
260.14180.0680.92*
117
1.61*
205
5.84*
744
50

Vitebsk region, which is considered the most safe forradioactive contamination. The values of average
cumulative dose were calculated at Institute ofRadiation Medicine for individuals of 18 years of age
and older in those regions. They represent thecombined external and internal exposure since theChernobyl accident.

Thus, the most probable cause leading to theincrease of birth of malformed children in Belarus is anincreased level of mutations due to chronic additionalexposure of the population or a complex of negativefactors. This can be indirectly evidenced by;a) an increased level of mutations in peripheral blood
lymphocytes in the population of Belarus, theUkraine and Russia, who has received additional
exposure (Lazjuk G.I. et al., 1995; Pilinskaya M.A.
et al., 1992; Vorobtsova E.A., Bogomazova A.N.,
1995);b) the most marked increase of CM frequency ingeneral and CMs with great contribution of de novo
mutations (polydactyly, reduction limb defects andmultiple CM) in the area with 137Cs contamination
density of 15 Ci/km2 and above. At the same time,
an increase of malformed children due to trisomies(Down’s syndrome is an example), which are denovo mutations, has not been found.
To determine a possible relation of increased CM
frequency with additional radiation, dependency ofCM frequency on additional radiation dose in Gomeland Mogilev regions (excepting large industrial cities)
was investigated and compared with the control data in

Table 3 shows the result of the analysis. Average
cumulative doses per each 1% increase of CM in thecontaminated regions over the CM increase in thecontrol region are calculated to be 0.31 mSv and 0.20
mSv, for Gomel region and Mogilev region,
respectively. Based on these values we can estimate adoubling dose of genetic effects due to radiation
exposure to be 0.02 - 0.03 Sv. Our estimate of doublingdose is considerably smaller than the value of 1 Sv
adopted by ICRP and UNSCEAR. This suggests thatgenetic effects of radiation exposure is much higher
than it has been usually considered, or the physicaldosimetry used to obtain dose values of the populationsignificantly underestimated the real doses.

Conclusions
176

Table 3 Comparison of CM frequencies with additional radiation doses obtained by rural populationof Belarus at the age of 18 years and older
Region underobservation

Frequency of CM per 1000 births
1982-85

1987-95

4.06±0.39

7.45±0.24

Gomel region

Averagecumulative doseby Chernobyl(mSv)
1986-94

Cumulative
dose per %Increase of CM(mSv/%)

13.40

0.31

8.82

0.20

0.24

-Increase: 83 %3.50± 0.53

6.41±0.30

Mogilev region
Increase: 83 %Vitebsk region

3.60±0.635.04±0.27

Increase: 40 %4. Sevankaev A.V. et al. Chromosome aberrations in
Lymphocytes of Residents of Areas Contaminatedby Radioactive Discharges from the ChernobylAccident. Radiat.Protect.Dosim. 1995, V.58, N.4,
P. 247-254..
5. Pilinskaya M.A., et al., Cytogenetic Indicator ofIrradiation among the People Suffering fromAffected Factors by the Chernobyl Accident,
Tsitologiya i genetika, 1992, V.26, N.6, P.6-9 (inRussian).
6. Pilinskaya M.A. et al., Cytogenetic Monitoring ofthe People Affected by the Accident at theChernobyl NPP, Tsitologiya i genetika, 1994, V.28,N.3, P.18-25 (in Russian).
7. Stepanova E.I. and Vanyurikhina E.A., Clinical andCytogenetic Characteristics of Children of thePeople Who Experienced Radiation Syndrome of 1and 2 Level As the Result of the Chernobyl
Accident, Tsitologiya i genetika, 1993, V.27, N.4,
P.10-13 (in Russian).
8. Vorobtsova E.I. and Boromazova A.N., Stable
Chromosome Aberration in Lymphocytes inPeripheral Blood of the Persons Affected As theResult of the Accident at ChNPP, Radiatsionnaya
biologiya i ragioekologiya, 1995, V.35, N.5,P.636-639 (in Russian).
9. J.R. Lazutka. Chromosome Aberrations and Rogue
Cells in Lymphocytes of Chernobyl Clean-up
Workers. Mutat.Res. 1996, V.350, P. 315-329.

Long-term studies have shown the evidence ofincreased frequency of anomalies in embryos of theresidents in Belarus. They are manifested as increased
malformation frequencies found in medical abortuses
and increased frequencies of CM revealed innewborns. The causes for such increases have not been
determined clearly. However, the correlation of
anomaly increase found in embryos with the level ofcontamination density of the areas, and the correlationof CM frequency with group average doses, as well as
the increase of CMs with great contribution of
dominant de novo mutations, evidence a radiation
factor playing a certain role in the dynamics of CM.

References
1. Lazjuk G.I. et al. Cytogenetic effects of additional
exposure to low levels of ionizing radiation.
Zdravoochraneniye Beloruss ii, 6: 38-41, 1990 (inRussian).
2. Lazjuk G.I. et al. Frequency changes of inheritedanomalies in the republic of Belarus after theChernobyl accident. Radiat.Protect.Dosim., 1995,V.62, N.1/2, P.71-74.
3. Lazjuk G.I. et al. Possible Genetic Consequences of
the Chernobyl Nuclear Accident on Belorussians.
The Chernobyl Accident (Thyroid Abnormalities inChildren, Congenital Abnormalities and OtherRadiation Related Information. The First Ten Years.
1996. Hiroshima, P.177-185.

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