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Medical consequences of the Chernobyl Nuclear Power Plant accident in Ukraine
International Congress Series 1258 (2003) 105 – 114
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Medical consequences of the Chernobyl Nuclear Power Plant accident in Ukraine Volodymyr G. Bebeshko * Research Center for Radiation Medicine, Academy of Medical Sciences of Ukraine, 53 Melnikov Street, Kiev 04050, Ukraine
Abstract. A 17-year experience of the Research Center for Radiation Medicine (RCRM), Academy of Medical Sciences of Ukraine, on the medical effects of the Chernobyl Nuclear Power Plant accident is reviewed. Results of RCRM in-house studies and international cooperative works are presented. Prospective future directions of international cooperative investigations are considered. D 2003 Published by Elsevier B.V. Keywords: Chernobyl Nuclear Power Plant accident; Medical effects; Clean-up workers; Evacuees; Inhabitants of contaminated territories
1. Introduction Almost 17 years have passed since the events at the Chernobyl Nuclear Power Plant (NPP), but even today scientists in many countries are still interested in the problem concerning the consequences of the accident in Ukraine, primarily related to the state of health of today’s and future generations. According to the decision of UNSCEAR, the government of the former USSR and the World Health Organization, the scale of the Chernobyl NPP accident is unanimously recognized as unprecedented. The Chernobyl accident was the most serious accident with radiation exposure (UNSCEAR, 2000). A need emerged for large-scale governmental measure. The complex series of measures undertaken in our country allowed us to protect the health of Soviet people from the possible negative radiation effects (Dr. E. Chazov, USSR Minister of Health, 1988). The Chernobyl accident, the most serious in the history of the nuclear power industry, cost the lives and damaged the health of workers at the power plant and created the
* Tel.: +380-44-213-3045; fax: +380-44-213-7202. E-mail address: [email protected] (V.G. Bebeshko). 0531-5131/ D 2003 Published by Elsevier B.V. doi:10.1016/S0531-5131(03)01212-3
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potential to adversely affect the health of many other people, e.g. accident recovery workers and people residing in areas which became contaminated with radioactivity (Dr. H. Nakajima, Director General, WHO, 1996). This review is aimed to show the Chernobyl medical effects at the level of 17-year section. 2. Results and discussion We recognize the phenomenon of the Chernobyl NPP accident factors not only as external irradiation and inhalation intake of radionuclides, but also as a high degree of chemical pollution (Fig. 1), changes of life conditions, inadequate perception of radiation danger, social and economic transformations of the post-accidental period. The number of radioactive substances released in the period from 6 May 1986 was 2 1018 Bq without taking into account tritium and short-life noble gases (Table 1). Nuclides released into environment led to radiation contamination at a density of 137Cs above 1 Ci/km2 through 36 000 hectares of territories of Ukraine in 78 districts of 12 regions. Plutonium releases were localized almost completely in the 30-km zone. Strontium contamination exceeded safe limits in northwest direction. Five thousand tons of chemical substances (lead, bentonite, etc.), thrown from helicopters on the destroyed reactor for suppressing the release of radioactive substances, formed a lava mass inside the reactor.
Fig. 1. Lead pollution (mg/kg) in Ukraine.
V.G. Bebeshko / International Congress Series 1258 (2003) 105–114
107
Table 1 The most important fractions of radionuclides released from destroyed reactor Radinuclide
Half-life (days)
Core inventory (Bq)
Estimated released fraction (%)
Krypton 85 Xenon 133 Iodine 131 Tellurium 132 Cesium 134 Cesium 137 Ruthenium 106 Strontium 89 Strontium 90 Plutonium 238 Plutonium 239 Plutonium 240 Plutonium 241 Curium 242
3930 5.27 8.05 3.25 750 11 000 368 53 10 000 31 500 8 900 000 2 400 000 4800 164
3.3 1016 7.3 1018 3.1 1018 3.2 1018 1.9 1017 2.9 1017 2.0 1018 2.3 1018 2.0 1017 1.0 1015 8.5 1014 1.2 1015 1.7 1014 2.6 1016
100 100 50 15 33 33 3 4 4 3 3 3 3 3
For the beginning of 2003, the number of survivors in the Ukraine exceeded 2.5 million: 240 800 clean-up workers, including 79 survivors of acute radiation syndrome (ARS), 56 377 evacuees, more than 1.8 million residents of territories contaminated with radionuclides, and 502 377 children—offspring of irradiated parents. The majority of clean-up workers were irradiated within the range of 250 mSv. Nowadays, 79 ARS survivors are residing in Ukraine (34—1st degree, 36—2nd degree, 9—3rd degree) and 92 for whom the ARS diagnosis was not confirmed during verification. The other ARS survivors are residing in Belarus—2; Kazakhstan—1; Azerbaijan—1; Moscow—14. Our Department for Radiation Pathology has no data about their situation. The problem of dose evaluation still remains acute 17 years after the accident. Dosimetric passportisation by the majority of settlements for the year 2000 revealed dose loadings not exceeding 1 mSv. Only 50% of individuals are included in existing registries, with official information about irradiation doses requiring verification and requiring improvement in the methodology of dose reconstruction. The Polissya regions require specific attention as, against the background of low contamination levels, increased concentrations of radionuclides intake are usual. Nowadays, the following international studies are being conducted on the problems of dosimetry and radiation hygiene: – – – –
clean-up workers retrospective dosimetry: leukemia and cataract (up to 2004); database for clean-up workers dosimetry (up to 2003); individual irradiation doses determined for children with thyroid cancer (up to 2004); international dosimetric group for improvement of biological dosimetry: enamel paramagnetic resonance (EPR) and fluorescence in situ hybridization (FISH) (up to 2004).
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Directions for subsequent cooperation are as follows: – improvement of registries of irradiated individuals; – implementation of new biological dosimetry methods; – study of abnormally high incorporation of radionuclides in residents of territories with low contamination levels. Deterministic, stochastic and combined effects have to be taken into account to evaluate the impact of the accident on human health. Deterministic effects in the outlook of bone marrow syndrome of 134 individuals irradiated in doses of 1 –12 Gy ended for 28 individuals in a fatal outcome in the first three months after the accident and 23 died in 1987 –2002. Different somatic diseases, including delayed neuropsychiatric complications and radiation lesions of skin, were established in the ARS survivors. Development of cataracts coincided with the dose loadings. The survivors demonstrate an excess of diseases of the all types of pathology. During the first 3– 6 months after the accident other medical effects were observed: – enlargement of thyroid with excess of T3 and T4 hormones in blood; – acute respiratory reactions (rhynolaryngotracheobronchites); – acute reactions of the digestive tract connected with high ionization of air by chemical pollutants; – phobic reactions with formation of chronic distress syndrome; – increased incidence of different classes of diseases connected with the involvement of a high number of specialists and improvement of quality of diagnostics. International studies of deterministic effects were limited by the establishment of the international database on the impact on the health condition of ARS patients (Ukraine, Russia, Germany and Netherlands) and the study of cataracts (USA – Ukraine, 1998). Possible directions for subsequent studies could be: – improvement and support of the international data base; – study of the late radiation conditioned pathology of skin in over-irradiated individuals; – establishment of a bank of tissues and DNA for over-irradiated individuals including individuals with ontological and oncohematological diseases; – molecular, biological and pathophysiological studies. Among clean-up workers who in 2000 numbered 240 000, the number of sick persons is increasing progressively. There are data about possible excess of cardiovascular, cerebrovascular, thyroid and other nontumor pathology among clean-up workers, but subsequent studies are needed to draw final conclusions. Stochastic effects among irradiated individuals: – There is no doubt about the increase of thyroid cancer incidence among children irradiaed at the age of 0– 18. Excess of thyroid cancer incidence is expected among clean-up workers of 1986. Today, people will try also to talk about it.
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– There is an increased tendency of leukemia cases among clean-up workers who worked in 1986 – 1987 and received considerable irradiation doses. Statistically significant data are obtained only for the Russian cohort of clean-up workers. No considerable excess of leukemia cases in Ukraine and Belarus was revealed. – No considerable excess of leukemia cases among children and adults residing in contaminated areas in the three suffered states was revealed. – There was not sufficient evidence about the correlation of radiation exposure of cleanup workers, evacuees and inhabitants of territories contaminated with radionuclides and detection of excess of diseases with solid tumors. – Stable chromosome aberrations were detected in somatic cells of survivors. It is necessary to prove whether these aberrations will lead to increased incidence of diseases among the offspring of victims. Preliminary cancer data in the 1986/1987 recovery operation workers suggested an excess of these indices in 1990 – 1993, but there are some difficulties with this statement which have to be discussed (Table 2). We are talking about statistical power and time aspects of cancer diagnostics, and their validation, including the international aspect. – The number of thyroid cancer patients started to increase 5 years after the Chernobyl accident and continues to increase now. – According to the data of the Ukrainian National Registry, 1791 thyroid cancer cases were detected up to 2000 among children and adolescents aged 0 – 17 years at the time of irradiation. According to the preliminary data, the highest excess of thyroid cancer cases was detected among clean-up workers in 1991– 1993 and 1994 – 1997. The number of thyroid cases observed among clean-up workers of 1986/1987 is essentially higher than the expected (Table 3). Primary nonverified data suggested excess in the frequency of leukemia and lymphomas among clean-up workers. Verification will be done by the cooperative case-control study effected by the USA and Ukraine concerning leukemia, myelodysplasia and multiple myeloma in the cohort of above 110 000 clean-up workers which will be completed in 2004. Unfortunately, no investigation of lymphomas among clean-up workers has been conducted.
Table 2 All cancers (ICD-9: 140 – 208) in recovery operation workers of 1986/1987 Observation period
Person-years
Observed number of cases
Expected number of cases
Standardized incidence ratio (%)
95% confidence interval
1990 – 1997 1990 – 1993 1994 – 1997
577 536 263 084 314 452
1496 538 958
1354 443 911
110.5 121.5 105.1
104.9 – 116.1 111.2 – 131.8 98.5 – 111.8
Data were derived from Ukrainian cancer registry (preliminary).
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Table 3 Thyroid cancer (ICD-9: 193) in recovery operation workers of 1986/1987 Observation period
Observed number of cases
Expected number of cases
Standardized incidence ratio (%)
95% confidence interval
1990 – 1997 1990 – 1993 1994 – 1997
37 13 24
8.4 3.3 5.1
442.7 393.0 475.2
300.0 – 585.3 179.4 – 606.6 285.1 – 665.4
Among irradiated children, any case of leukemia or lymphoma was not detected (Fig. 2). Evaluation in the noncontaminated Poltava region revealed the same dynamics. Myelodysplasia was detected in 114 irradiated individuals, but many cases require verification; this work is being conducted now. Clean-up workers demonstrated an essential increase in chromosome aberrations, which has stable character in individuals with myelodysplastic syndrome. The number of mutations of T-cell receptor among clean-up workers revealed the time-dependent decrease as a result of chromosome aberrations in children evacuated and residing in contaminated territories. Nowadays, the following international studies on oncology are implemented: – leukemia, myelodysplasis and multiple myeloma among clean-up workers in Ukraine (since 1997); – thyroid cancer among children (since 1997); – thyroid cancer in population (descriptively) (since 1998); – leukemia in population of adult and children (descriptively) (since 1998); – tissues bank on thyroid (since 2000).
Fig. 2. Prevalence of leukemia and lymphoma in children (1980 – 1997). The two vertical axes indicate the number of cases (left) and the morbidity per 100 000 children (right).
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Directions for future studies could be determined as: – – – –
thyroid cancer among clean-up workers (case-control); breast cancer in women clean-up workers (case-control); molecular studies of radiation induced leukemias; international expertise and verification of leukemia, myelodysplasia and thyroid cancer cases among clean-up workers in registries; – somatic mutations among clean-up workers and their offspring. Among the other types of impact on the health of survivors during the 17 years after the accident, neuropsychic and cardiovascular diseases prevail. However, the following phenomena are noted: – – – – – –
worsening of the state of health of clean-up workers; increase in the number of disabled persons among clean-up workers; decrease in birth rate; worsening of health condition of neonates; excess of complicated pregnancies; poor state of health of children.
Certainly, other nonradiation risk factors influenced the state of health of clean-up workers of 1986/1987. Under almost unchanged indices of primary incidence, the prevalence of diseases is progressively growing, first of all among clean-up workers of 1986/1987 (Fig. 3). This increase was especially pronounced in the 12 years after the accident as compared with non-irradiated adult inhabitants of the Ukraine.
Fig. 3. Incidence and prevalence of diseases in recovery operation workers by the period of their work in Chernobyl zone. The vertical axis indicates the number of cases per 100 000 population.
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The disability rate among clean-up workers is increasing considerably, especially among those irradiated with doses of 250 mSv and above. The increase in the number of pathological conditions is detected for the majority of nontumor diseases. The incidence and prevalence (Fig. 4) of nervous system pathology is increasing. Functional disorders detected in the first years after the accident are transformed into organic disorders. Primary incidence spread of cardiovascular system diseases and endocrine system diseases is increasing. Bronchopulmonary system disorders started to be detected from 1992. Squamous metaplasia and cell atypia of bronchial epithelium are revealed in cases of atrophic and sclerotic changes. Under high primary morbidity, the spread of gastrointestinal tract diseases is increasing among clean-up workers. The spread of this pathology is especially high among individuals continuing to work in the 30-km zone around the NPP up to the present day. In the remote period (12 –14 years after the accident), different types of immunological disorders among clean-up workers of 1986 can be determined (Fig. 5). Indices of mortality among clean-up workers do not exceed those in the non-irradiated population of the Ukrainian inhabitants. For nontumor diseases, there are few international investigations: – investigation of interactions between cell immunity and metabolites of arachidonic acid among clean-up workers has been implemented in 1998 –2000 (by NATO grant in cooperation with the Palladin Institute for Biochemistry, National Academy of Sciences of Ukraine, and the University in Lyon, France). – Descriptive creation of a database concerning psychological disorders among clean-up workers was started in 2000. Possible directions for future investigations to be considered are as follows: – incidence of and mortality from cardiovascular pathology; – impact of external irradiation and inhalation of radionuclides;
Fig. 4. Prevalence of nervous system pathology in recovery operation workers and non-exposed people by observation periods: (1) 1987 – 1988; (2) 1989 – 1991; (3) 1992 – 1996; (4) 1997 – 2000.
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Fig. 5. Type of immune function disorders in emergency radiation workers of 1986 observed 12 – 14 years after irradiation.
– impact on health condition of personnel in the 30-km zone and the ‘‘Shelter’’ object during works on decommissioning of the Chernobyl NPP; – nontumor thyroid pathology connected with thyroid irradiation; – brain damage as a result of low doses of irradiation; – molecular and biological studies and the establishment of tissue banks. Among adult evacuees, cases of nontumor diseases and primary incidence are higher than in the adult population of the Ukraine in general. Indices of annual dynamics of the extent of diseases among evacuees suggest the highest indices in individuals who evacuated during the first 2 days after the accident. This could be explained by the highest dose loading on the contingencies presumably from the city of Pripyat. On the other hand, rationality of late evacuation of inhabitants of the 30-km zone settlement (at 19th –50th day) is doubtful. Data about the relative cumulative risk of separate diseases among individuals included in the clinical and epidemiological registry are the highest for maculodystrophy of the retina. All of these data, however, need subsequent verification. The Ukraine is now in the condition of a demographic crisis connected with the excess of mortality over the birth rate. Mortality indices in zones have the same dynamics as the control excluding the excess mortality index in the second zone. At first glance, the decrease of mortality among neonates looks quite paradoxical. Probably, factors such as planned birth under difficult social and economic conditions, early registration of pregnant women in the outpatient clinic and care of problematic neonates influence this index. In a complex study, the number of healthy children is decreasing progressively with the increase of radioiodine dose absorbed by the thyroid. In the context of nontumor diseases in a population of survivors, the following international studies are implemented: – incidence and mortality among children in contaminated territories (descriptively) (since 1993);
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– brain damage in utero (descriptively)(since 1993); – diet (since 1999). Prospective future directions of investigations could be considered as follows: – – – –
incidence and mortality from cardiovascular pathology among evacuees; thyroid irradiation and somatic pathology; stress and public information; molecular and biological studies and the establishment of tissue banks.
3. Conclusions (1) Deterministic effects were detected only among clean-up workers of 1986; (2) The clear excess of non-oncological disorders under the complex interaction of irradiation and other factors in subsequent years was widespread among clean-up workers. Laboratory data suggested an increase in markers of radiation impact; (3) Preliminary data demonstrated the presence of late stochastic effects, requiring subsequent study; (4) There are contradictions in the data about the frequency of genetic and hereditary diseases connected with irradiation as a result of the Chernobyl catastrophe.
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Medical consequences of the Chernobyl Nuclear Power Plant accident in Ukraine Volodymyr G. Bebeshko * Research Center for Radiation Medicine, Academy of Medical Sciences of Ukraine, 53 Melnikov Street, Kiev 04050, Ukraine
Abstract. A 17-year experience of the Research Center for Radiation Medicine (RCRM), Academy of Medical Sciences of Ukraine, on the medical effects of the Chernobyl Nuclear Power Plant accident is reviewed. Results of RCRM in-house studies and international cooperative works are presented. Prospective future directions of international cooperative investigations are considered. D 2003 Published by Elsevier B.V. Keywords: Chernobyl Nuclear Power Plant accident; Medical effects; Clean-up workers; Evacuees; Inhabitants of contaminated territories
1. Introduction Almost 17 years have passed since the events at the Chernobyl Nuclear Power Plant (NPP), but even today scientists in many countries are still interested in the problem concerning the consequences of the accident in Ukraine, primarily related to the state of health of today’s and future generations. According to the decision of UNSCEAR, the government of the former USSR and the World Health Organization, the scale of the Chernobyl NPP accident is unanimously recognized as unprecedented. The Chernobyl accident was the most serious accident with radiation exposure (UNSCEAR, 2000). A need emerged for large-scale governmental measure. The complex series of measures undertaken in our country allowed us to protect the health of Soviet people from the possible negative radiation effects (Dr. E. Chazov, USSR Minister of Health, 1988). The Chernobyl accident, the most serious in the history of the nuclear power industry, cost the lives and damaged the health of workers at the power plant and created the
* Tel.: +380-44-213-3045; fax: +380-44-213-7202. E-mail address: [email protected] (V.G. Bebeshko). 0531-5131/ D 2003 Published by Elsevier B.V. doi:10.1016/S0531-5131(03)01212-3
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potential to adversely affect the health of many other people, e.g. accident recovery workers and people residing in areas which became contaminated with radioactivity (Dr. H. Nakajima, Director General, WHO, 1996). This review is aimed to show the Chernobyl medical effects at the level of 17-year section. 2. Results and discussion We recognize the phenomenon of the Chernobyl NPP accident factors not only as external irradiation and inhalation intake of radionuclides, but also as a high degree of chemical pollution (Fig. 1), changes of life conditions, inadequate perception of radiation danger, social and economic transformations of the post-accidental period. The number of radioactive substances released in the period from 6 May 1986 was 2 1018 Bq without taking into account tritium and short-life noble gases (Table 1). Nuclides released into environment led to radiation contamination at a density of 137Cs above 1 Ci/km2 through 36 000 hectares of territories of Ukraine in 78 districts of 12 regions. Plutonium releases were localized almost completely in the 30-km zone. Strontium contamination exceeded safe limits in northwest direction. Five thousand tons of chemical substances (lead, bentonite, etc.), thrown from helicopters on the destroyed reactor for suppressing the release of radioactive substances, formed a lava mass inside the reactor.
Fig. 1. Lead pollution (mg/kg) in Ukraine.
V.G. Bebeshko / International Congress Series 1258 (2003) 105–114
107
Table 1 The most important fractions of radionuclides released from destroyed reactor Radinuclide
Half-life (days)
Core inventory (Bq)
Estimated released fraction (%)
Krypton 85 Xenon 133 Iodine 131 Tellurium 132 Cesium 134 Cesium 137 Ruthenium 106 Strontium 89 Strontium 90 Plutonium 238 Plutonium 239 Plutonium 240 Plutonium 241 Curium 242
3930 5.27 8.05 3.25 750 11 000 368 53 10 000 31 500 8 900 000 2 400 000 4800 164
3.3 1016 7.3 1018 3.1 1018 3.2 1018 1.9 1017 2.9 1017 2.0 1018 2.3 1018 2.0 1017 1.0 1015 8.5 1014 1.2 1015 1.7 1014 2.6 1016
100 100 50 15 33 33 3 4 4 3 3 3 3 3
For the beginning of 2003, the number of survivors in the Ukraine exceeded 2.5 million: 240 800 clean-up workers, including 79 survivors of acute radiation syndrome (ARS), 56 377 evacuees, more than 1.8 million residents of territories contaminated with radionuclides, and 502 377 children—offspring of irradiated parents. The majority of clean-up workers were irradiated within the range of 250 mSv. Nowadays, 79 ARS survivors are residing in Ukraine (34—1st degree, 36—2nd degree, 9—3rd degree) and 92 for whom the ARS diagnosis was not confirmed during verification. The other ARS survivors are residing in Belarus—2; Kazakhstan—1; Azerbaijan—1; Moscow—14. Our Department for Radiation Pathology has no data about their situation. The problem of dose evaluation still remains acute 17 years after the accident. Dosimetric passportisation by the majority of settlements for the year 2000 revealed dose loadings not exceeding 1 mSv. Only 50% of individuals are included in existing registries, with official information about irradiation doses requiring verification and requiring improvement in the methodology of dose reconstruction. The Polissya regions require specific attention as, against the background of low contamination levels, increased concentrations of radionuclides intake are usual. Nowadays, the following international studies are being conducted on the problems of dosimetry and radiation hygiene: – – – –
clean-up workers retrospective dosimetry: leukemia and cataract (up to 2004); database for clean-up workers dosimetry (up to 2003); individual irradiation doses determined for children with thyroid cancer (up to 2004); international dosimetric group for improvement of biological dosimetry: enamel paramagnetic resonance (EPR) and fluorescence in situ hybridization (FISH) (up to 2004).
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Directions for subsequent cooperation are as follows: – improvement of registries of irradiated individuals; – implementation of new biological dosimetry methods; – study of abnormally high incorporation of radionuclides in residents of territories with low contamination levels. Deterministic, stochastic and combined effects have to be taken into account to evaluate the impact of the accident on human health. Deterministic effects in the outlook of bone marrow syndrome of 134 individuals irradiated in doses of 1 –12 Gy ended for 28 individuals in a fatal outcome in the first three months after the accident and 23 died in 1987 –2002. Different somatic diseases, including delayed neuropsychiatric complications and radiation lesions of skin, were established in the ARS survivors. Development of cataracts coincided with the dose loadings. The survivors demonstrate an excess of diseases of the all types of pathology. During the first 3– 6 months after the accident other medical effects were observed: – enlargement of thyroid with excess of T3 and T4 hormones in blood; – acute respiratory reactions (rhynolaryngotracheobronchites); – acute reactions of the digestive tract connected with high ionization of air by chemical pollutants; – phobic reactions with formation of chronic distress syndrome; – increased incidence of different classes of diseases connected with the involvement of a high number of specialists and improvement of quality of diagnostics. International studies of deterministic effects were limited by the establishment of the international database on the impact on the health condition of ARS patients (Ukraine, Russia, Germany and Netherlands) and the study of cataracts (USA – Ukraine, 1998). Possible directions for subsequent studies could be: – improvement and support of the international data base; – study of the late radiation conditioned pathology of skin in over-irradiated individuals; – establishment of a bank of tissues and DNA for over-irradiated individuals including individuals with ontological and oncohematological diseases; – molecular, biological and pathophysiological studies. Among clean-up workers who in 2000 numbered 240 000, the number of sick persons is increasing progressively. There are data about possible excess of cardiovascular, cerebrovascular, thyroid and other nontumor pathology among clean-up workers, but subsequent studies are needed to draw final conclusions. Stochastic effects among irradiated individuals: – There is no doubt about the increase of thyroid cancer incidence among children irradiaed at the age of 0– 18. Excess of thyroid cancer incidence is expected among clean-up workers of 1986. Today, people will try also to talk about it.
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109
– There is an increased tendency of leukemia cases among clean-up workers who worked in 1986 – 1987 and received considerable irradiation doses. Statistically significant data are obtained only for the Russian cohort of clean-up workers. No considerable excess of leukemia cases in Ukraine and Belarus was revealed. – No considerable excess of leukemia cases among children and adults residing in contaminated areas in the three suffered states was revealed. – There was not sufficient evidence about the correlation of radiation exposure of cleanup workers, evacuees and inhabitants of territories contaminated with radionuclides and detection of excess of diseases with solid tumors. – Stable chromosome aberrations were detected in somatic cells of survivors. It is necessary to prove whether these aberrations will lead to increased incidence of diseases among the offspring of victims. Preliminary cancer data in the 1986/1987 recovery operation workers suggested an excess of these indices in 1990 – 1993, but there are some difficulties with this statement which have to be discussed (Table 2). We are talking about statistical power and time aspects of cancer diagnostics, and their validation, including the international aspect. – The number of thyroid cancer patients started to increase 5 years after the Chernobyl accident and continues to increase now. – According to the data of the Ukrainian National Registry, 1791 thyroid cancer cases were detected up to 2000 among children and adolescents aged 0 – 17 years at the time of irradiation. According to the preliminary data, the highest excess of thyroid cancer cases was detected among clean-up workers in 1991– 1993 and 1994 – 1997. The number of thyroid cases observed among clean-up workers of 1986/1987 is essentially higher than the expected (Table 3). Primary nonverified data suggested excess in the frequency of leukemia and lymphomas among clean-up workers. Verification will be done by the cooperative case-control study effected by the USA and Ukraine concerning leukemia, myelodysplasia and multiple myeloma in the cohort of above 110 000 clean-up workers which will be completed in 2004. Unfortunately, no investigation of lymphomas among clean-up workers has been conducted.
Table 2 All cancers (ICD-9: 140 – 208) in recovery operation workers of 1986/1987 Observation period
Person-years
Observed number of cases
Expected number of cases
Standardized incidence ratio (%)
95% confidence interval
1990 – 1997 1990 – 1993 1994 – 1997
577 536 263 084 314 452
1496 538 958
1354 443 911
110.5 121.5 105.1
104.9 – 116.1 111.2 – 131.8 98.5 – 111.8
Data were derived from Ukrainian cancer registry (preliminary).
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Table 3 Thyroid cancer (ICD-9: 193) in recovery operation workers of 1986/1987 Observation period
Observed number of cases
Expected number of cases
Standardized incidence ratio (%)
95% confidence interval
1990 – 1997 1990 – 1993 1994 – 1997
37 13 24
8.4 3.3 5.1
442.7 393.0 475.2
300.0 – 585.3 179.4 – 606.6 285.1 – 665.4
Among irradiated children, any case of leukemia or lymphoma was not detected (Fig. 2). Evaluation in the noncontaminated Poltava region revealed the same dynamics. Myelodysplasia was detected in 114 irradiated individuals, but many cases require verification; this work is being conducted now. Clean-up workers demonstrated an essential increase in chromosome aberrations, which has stable character in individuals with myelodysplastic syndrome. The number of mutations of T-cell receptor among clean-up workers revealed the time-dependent decrease as a result of chromosome aberrations in children evacuated and residing in contaminated territories. Nowadays, the following international studies on oncology are implemented: – leukemia, myelodysplasis and multiple myeloma among clean-up workers in Ukraine (since 1997); – thyroid cancer among children (since 1997); – thyroid cancer in population (descriptively) (since 1998); – leukemia in population of adult and children (descriptively) (since 1998); – tissues bank on thyroid (since 2000).
Fig. 2. Prevalence of leukemia and lymphoma in children (1980 – 1997). The two vertical axes indicate the number of cases (left) and the morbidity per 100 000 children (right).
V.G. Bebeshko / International Congress Series 1258 (2003) 105–114
111
Directions for future studies could be determined as: – – – –
thyroid cancer among clean-up workers (case-control); breast cancer in women clean-up workers (case-control); molecular studies of radiation induced leukemias; international expertise and verification of leukemia, myelodysplasia and thyroid cancer cases among clean-up workers in registries; – somatic mutations among clean-up workers and their offspring. Among the other types of impact on the health of survivors during the 17 years after the accident, neuropsychic and cardiovascular diseases prevail. However, the following phenomena are noted: – – – – – –
worsening of the state of health of clean-up workers; increase in the number of disabled persons among clean-up workers; decrease in birth rate; worsening of health condition of neonates; excess of complicated pregnancies; poor state of health of children.
Certainly, other nonradiation risk factors influenced the state of health of clean-up workers of 1986/1987. Under almost unchanged indices of primary incidence, the prevalence of diseases is progressively growing, first of all among clean-up workers of 1986/1987 (Fig. 3). This increase was especially pronounced in the 12 years after the accident as compared with non-irradiated adult inhabitants of the Ukraine.
Fig. 3. Incidence and prevalence of diseases in recovery operation workers by the period of their work in Chernobyl zone. The vertical axis indicates the number of cases per 100 000 population.
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The disability rate among clean-up workers is increasing considerably, especially among those irradiated with doses of 250 mSv and above. The increase in the number of pathological conditions is detected for the majority of nontumor diseases. The incidence and prevalence (Fig. 4) of nervous system pathology is increasing. Functional disorders detected in the first years after the accident are transformed into organic disorders. Primary incidence spread of cardiovascular system diseases and endocrine system diseases is increasing. Bronchopulmonary system disorders started to be detected from 1992. Squamous metaplasia and cell atypia of bronchial epithelium are revealed in cases of atrophic and sclerotic changes. Under high primary morbidity, the spread of gastrointestinal tract diseases is increasing among clean-up workers. The spread of this pathology is especially high among individuals continuing to work in the 30-km zone around the NPP up to the present day. In the remote period (12 –14 years after the accident), different types of immunological disorders among clean-up workers of 1986 can be determined (Fig. 5). Indices of mortality among clean-up workers do not exceed those in the non-irradiated population of the Ukrainian inhabitants. For nontumor diseases, there are few international investigations: – investigation of interactions between cell immunity and metabolites of arachidonic acid among clean-up workers has been implemented in 1998 –2000 (by NATO grant in cooperation with the Palladin Institute for Biochemistry, National Academy of Sciences of Ukraine, and the University in Lyon, France). – Descriptive creation of a database concerning psychological disorders among clean-up workers was started in 2000. Possible directions for future investigations to be considered are as follows: – incidence of and mortality from cardiovascular pathology; – impact of external irradiation and inhalation of radionuclides;
Fig. 4. Prevalence of nervous system pathology in recovery operation workers and non-exposed people by observation periods: (1) 1987 – 1988; (2) 1989 – 1991; (3) 1992 – 1996; (4) 1997 – 2000.
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Fig. 5. Type of immune function disorders in emergency radiation workers of 1986 observed 12 – 14 years after irradiation.
– impact on health condition of personnel in the 30-km zone and the ‘‘Shelter’’ object during works on decommissioning of the Chernobyl NPP; – nontumor thyroid pathology connected with thyroid irradiation; – brain damage as a result of low doses of irradiation; – molecular and biological studies and the establishment of tissue banks. Among adult evacuees, cases of nontumor diseases and primary incidence are higher than in the adult population of the Ukraine in general. Indices of annual dynamics of the extent of diseases among evacuees suggest the highest indices in individuals who evacuated during the first 2 days after the accident. This could be explained by the highest dose loading on the contingencies presumably from the city of Pripyat. On the other hand, rationality of late evacuation of inhabitants of the 30-km zone settlement (at 19th –50th day) is doubtful. Data about the relative cumulative risk of separate diseases among individuals included in the clinical and epidemiological registry are the highest for maculodystrophy of the retina. All of these data, however, need subsequent verification. The Ukraine is now in the condition of a demographic crisis connected with the excess of mortality over the birth rate. Mortality indices in zones have the same dynamics as the control excluding the excess mortality index in the second zone. At first glance, the decrease of mortality among neonates looks quite paradoxical. Probably, factors such as planned birth under difficult social and economic conditions, early registration of pregnant women in the outpatient clinic and care of problematic neonates influence this index. In a complex study, the number of healthy children is decreasing progressively with the increase of radioiodine dose absorbed by the thyroid. In the context of nontumor diseases in a population of survivors, the following international studies are implemented: – incidence and mortality among children in contaminated territories (descriptively) (since 1993);
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– brain damage in utero (descriptively)(since 1993); – diet (since 1999). Prospective future directions of investigations could be considered as follows: – – – –
incidence and mortality from cardiovascular pathology among evacuees; thyroid irradiation and somatic pathology; stress and public information; molecular and biological studies and the establishment of tissue banks.
3. Conclusions (1) Deterministic effects were detected only among clean-up workers of 1986; (2) The clear excess of non-oncological disorders under the complex interaction of irradiation and other factors in subsequent years was widespread among clean-up workers. Laboratory data suggested an increase in markers of radiation impact; (3) Preliminary data demonstrated the presence of late stochastic effects, requiring subsequent study; (4) There are contradictions in the data about the frequency of genetic and hereditary diseases connected with irradiation as a result of the Chernobyl catastrophe.