Review of biodosimetry in Chernobyl liquidators

Transcription

1 Review of biodosimetry in Chernobyl liquidators Oleg Belyakov Radiation Biologist Applied Radiation Biology and Radiotherapy Section Division of Human Health International Atomic Energy Agency

2 Contents Introduction Chernobyl accident Liquidators Doses Conclusions Acknowledgments OvB BIODOSE-21, Hiroshima, Japan 12 June

3 This presentation is based on the Chernobyl Liquidators Project, which was discontinued in 2000 and currently offline OvB BIODOSE-21, Hiroshima, Japan 12 June

4 Annually published number of scientific liquidator related papers (source: Medline database) 60 Number of published papers Year OvB BIODOSE-21, Hiroshima, Japan 12 June

5 Part I. Chernobyl accident...the most serious accident in the history of the nuclear industry... International conference: One decade after Chernobyl Vienna, Austria 8-12 April 1996 OvB BIODOSE-21, Hiroshima, Japan 12 June

6 1:23 am on Saturday, 26 April 1986 OvB BIODOSE-21, Hiroshima, Japan 12 June

7 Release rate of radioactive substances Core inventory on 26 April 1986 Nuclide Half-life Activity (PBq) Total release during the accident Percent Activity of (PBq) inventory Xe d I d ~1760 Te h ~1150 Cs y ~54 Cs y ~ (from Chernobyl ten years on. Radiological and health impact, NEA Committee on Radiation Protection and Public Health. OECD Nuclear Energy Agency, 1995) OvB BIODOSE-21, Hiroshima, Japan 12 June

8 Accident s fall-out The accident left its fall-out trail on 23% of the territory of Belarus, wherein more than 2 million people lived, on 4.8% of the territory of Ukraine, and on 0.5 % of the territory of Russia. Density of contamination with the Cesium-137 of these territories constitutes more than 1 Ci/sq.km. (from The International Chernobyl Project. Technical report, 1991). OvB BIODOSE-21, Hiroshima, Japan 12 June

9 Part II. Liquidators... the heroism of the liquidators may have long-lasting value, not only by preventing an even worse catastrophe but also by helping guide future radiation safety standards Science 272:360 OvB BIODOSE-21, Hiroshima, Japan 12 June

10 Synonyms for liquidators The word "liquidator" is derived from the Russian verb which means "to eliminate or, more specifically, to eliminate consequences of an accident" in narrow meaning. CLEAN-UP WORKERS RECOVERY WORKERS EMERGENCY WORKERS SALVAGE PERSONAL LIQUIDATORS MITIGATION WORKERS AMELIORATORS OF THE CHERNOBYL ACCIDENT DECONTAMINATION WORKERS RESCUERS OF CONSIQUENCES OF CHERNOBYL S DISASTER OvB BIODOSE-21, Hiroshima, Japan 12 June

11 Definition Liquidators - people who were directly involved in clean-up operations in the accident zone within 30 km from the destroyed reactor in (from Ilyin L.A. Chernobyl: myth and reality. Moscow, Megapolis, 1995) OvB BIODOSE-21, Hiroshima, Japan 12 June

12 The legal definition There are a few different official definitions for liquidator in countries of the former USSR: Russia, Belarus, Ukraine, Baltic states. According to Russian legislation a liquidator is a person who was engaged in clean-up work after the Chernobyl accident at the permanent eviction zone. This territory surrounds the Chernobyl station and is located partly on the territory of Russia. It is not defined by a simple radius around the plant but by a pollution level of >1.5x10 6 Bq/m 2 (40 Ci/km 2 ) and represents an area from where the population was evacuated in The legal definition is criterion for inclusion in national medico-dosimetric Chernobyl registries. OvB BIODOSE-21, Hiroshima, Japan 12 June

13 definition, a large number of ad hoc workers, including operators of the plant, emergency volunteers such as fire-fighters, and military personnel, as well as many non-professional personnel. All these people became known by the Russian term likvidator. About 200,000 liquidators worked in the region of Chernobyl during the period , when radiation exposures were highest. They were among some 600,000 to 800,000 persons who were registered as involved in activities relating to alleviating the consequences of the accident. This includes persons who participated in the cleanup after the accident (including cleaning up around the reactor, construction of the sarcophagus, decontamination, road building, and destruction and burial of contaminated buildings, forests and equipment), as well as many other general personnel who worked in the territories designated as contaminated and who generally received low doses. OvB BIODOSE-21, Hiroshima, Japan 12 June

14 How many? 300, ,000 Ilyin L.A. Chernobyl: myth and reality. Moscow, Megapolis, up to 800,000 an Assessment by the NEA Committee on Radiation Protection and Public Health OECD Nuclear Energy Agency in Chernobyl ten years on. Radiological and health impact, , ,000 (about 200,000 in ) International conference: One decade after Chernobyl Vienna, Austria 8-12 April ,100 All-Union (later State) Distribution Register (USSR, ) 168,000 The Russian National Medical Dosimetric Registry, January 1, 1996 about 600,000 The radiological consequences of the Chernobyl accident. European Commission. Brussels, , ,000 Scientific journal papers, OvB BIODOSE-21, Hiroshima, Japan 12 June

15 The most realistic estimation thousand people Ilyin L.A. Chernobyl: Myth and reality. Moscow, Megapolis, OvB BIODOSE-21, Hiroshima, Japan 12 June

16 Classifications of the Chernobyl liquidators Time oriented Task oriented Organisational structure OvB BIODOSE-21, Hiroshima, Japan 12 June

17 Time scale of the Chernobyl accident cleanup work Early liquidators Liquidators Liquidators Time oriented grouping of liquidators Initial stage Early stage Late stage Stages of the clean-up work The Chernobyl Accident Evacuation of Pripyat Sarcophagus construction was completed Dissolution of the Soviet Union Events Time 26 April April 1986 November OvB BIODOSE-21, Hiroshima, Japan 12 June

18 Liquidators of different years. Data from All-Union (later State) Distribution Register Year Number of liquidators , , , , ,100 (from Ilyin L.A. Chernobyl: myth and reality. Moscow, Megapolis, 1995) OvB BIODOSE-21, Hiroshima, Japan 12 June

19 Types of liquidators and level of exposure People who were at the site during the explosion Samoilenko group - the roof of the third unit - about 5000 Sarcophagus builders - a few tens of thousands people 476 persons of staff, including 200 members on-duty personnel CNPS Sarcophagus workers, 15 About 300 construction workers (at the 5th construction site) Other groups of liquidators about Dose increase OvB BIODOSE-21, Hiroshima, Japan 12 June

20 How many? Ministry of Interior Affairs of the Russian Federation (3,326 persons) USSR Ministry of the Interior Affairs, 1991 (32, 111 persons) Police Federal Counter- Intelligence Service (1,093 persons) Professional military (mainly officers) 20% 80% 20,508 persons 90,000 persons KGB USSR Servicemen Reservists Military and paramilitary Ministry of Railways of the Russian Federation (1,242 persons) Scientists, including Institute of Biophysics of the Ministry of Health of the Russian Federation (19,236 persons) Personnel on Chernobyl Nuclear Power Station and from other stations Medical and sanitary personnel Construction workers Others (drivers, service workers etc.) Liquidators ± in total This group is very heterogeneous, different subgroups were under different command during clean-up works. Data about liquidators is stored in files of different organisations, subject to multiple rearrangements during years past since the Chernobyl accident. OvB BIODOSE-21, Hiroshima, Japan 12 June

21 Interaction of medical departments of military operative groups during clean up work after the Chernobyl accident From: Chizh I.M. The experience of the medical service of the Armed Forces in the cleanup of the aftereffects of the accident at the Chernobyl Atomic Electric Power Station. Voen Med Zh, 1996, 317:6, 4-15, 80, in Russian. Departments of the Defence ministry Operative group of the Central Military Medical department of the Defence ministry Scheme by General-Colonel I.M.Chizh, head of the Central Military Medical department of the Russian Ministry of Defence, head of the Medical Service of the Russian Military Forces. Medical department of Operative group of the Defence ministry Medical department of Operative group of the Civil Defence forces Operative group of the Ministry of Health Medical department of Operative group of the Prikarpatsky ( At Carpathians ) Military District (sector 3) management, co-ordination, interaction radiation safety control scientific-methodological support co-ordination of the radiation control work on Chernobyl NPP Medical department of Operative group of the Kievsky (Kiev) Military District (sector 2) Medical department of Operative group of the Belorussky (Belorusian) Military District (sector 2) OvB BIODOSE-21, Hiroshima, Japan 12 June

22 Cohorts of liquidators Russia 1 Russia 2 Belorus 3 Ukraine 2 Baltic Countries 4 Estonia Latvia Lithuania mainly Ivanov V.K., Tsyb A.F. Chernobyl radiation risks: assessments of morbidity, mortality and disability rates according to the data of the National Radiation and Epidemiological Registry, Nagasaki Symposium Radiation and Human Health. Elsevier Science B.V., 1996: Liktarev I.A., Chumak V.V. Overview of the Chernobyl liquidator database. 44 th Annual Meeting of the Radiation Research Society, April 14-17, 1996, Chicago. Book of Abstracts. 3 Ilyin L.A. Chernobyl: myth and reality. Moscow, Megapolis, Bigbee WL. Jensen RH. Veidebaum T. Tekkel M. Rahu M. Stengrevics A. Kesminiene A. Kurtinaitis J. Auvinen A. Hakulinen T. Servomaa K. Rytomaa T. Obrams GI. Boice JD Jr. Glycophorin A biodosimetry in Chernobyl cleanup workers from the Baltic countries BMJ. 312(7038):1078-9, 1996 Apr The National Chernobyl Registry of Russia, as quoted by Liktarev and Chumak 2. 6 The national registry of Ukraine OvB BIODOSE-21, Hiroshima, Japan 12 June

23 Sex distribution of the Chernobyl liquidators Women consisted of less than 1% of the Russian cohort of the Chernobyl liquidators (Pitkevitch et al., 1997). They were mainly members of staff of the Chernobyl Nuclear Power Plant and medics participated in clean-up work. Tsvelev (Tsvelev et al., 1997) has mentioned 37 womenliquidators in his paper. Israeli cohort of liquidators consisted of 47 men and 8 women (Kordysh et al., 1995). Kordysh, E., Goldsmith, J., Quastel, M., Poljak, S., Merkin, L., Cohen, R. and Gorodischer, R. (1995). Health effects in a casual sample of immigrants to Israel from areas contaminated by the Chernobyl explosion. Environ Health Perspect, 103:10, Pitkevitch, V.A., Ivanov, V.K., Tsyb, A.F., Maksyoutov, M.A., Matiash, V.A. and Shchukina, N.V. (1997). Exposure levels for persons involved in recovery operations after the Chernobyl accident. Statistical analysis based on the data of the Russian National Medical and Dosimetric Registry (RNMDR). Radiat Environ Biophys, 36:3, Tsvelev, I., Kira, E., Bezhenarq, V. and Grebeniuk, A. (1997). The nature of the changes in the immunity of the women who worked in the cleanup of the sequelae of the accident at the Chernobyl Atomic Electric Power Station and were evacuated from the radioactively contaminated area. Voen Med Zh, 318:1, 38-42, 80 OvB BIODOSE-21, Hiroshima, Japan 12 June

24 Distribution of liquidators from Russian cohort by age at the moment of arrival to the Chernobyl area (30 km zone). Age group Number of liquidators Percentage ,180 1, ,905 7, ,097 12, ,323 31, ,116 32, ,587 10, ,294 2, , , Cohort is consisted of 114,504 selected cases, average age is 34,3 years (from Ivanov, V.K., Rastopchin, E.M., Gorsky, A.I. and Ryvkin, V.B. (1998). Cancer incidence among liquidators of the Chernobyl accident: solid tumors, Health Phys, 74:3, ) OvB BIODOSE-21, Hiroshima, Japan 12 June

25 Sources of information Registries Large scale projects i.e. The International Chernobyl Project, 1991 (), Thyroid cancer screening program among Chernobyl liquidators from Baltic countries and The Ukrainian American Chernobyl Ocular Study (UACOS) Scientific papers and books about 2000 sources Proceedings of conferences i.e. International conference: One decade after Chernobyl Vienna, Austria 8-12 April 1996 Non-scientific literature and Internet publications USSR medical registers All Union (later State) Distribution Register National registers Russian National Medical and Dosimetric Registry USSR ministry's registers USA-Canada Chernobyl Immigrant Registry Immigrant registers: Israeli registry Other national registers: Belorusian, Ukrainian, Estonian, Latvian, and Lithuanian OvB BIODOSE-21, Hiroshima, Japan 12 June

26 Hierarchical structure of the All-Union (later State) Distribution Register Soviet Union Registry Ministry of Health Ministry Registers Ministry of Health in Republics Regional Hospital Ministry of Defence USSR Ministry of Internal Affairs USSR KGB USSR Sub-regional Hospital Transport Ministry USSR (from Tsyb AF. Ivanov VK. Airapetov SA. Gagin EA. Maksiutov MA. Rozhkov OV. Stadnik OE. Chekin SIu. Saakian AK. Radiation-epidemiological analysis of the data of State Registry of persons exposed to radiation due to the Chernobyl AES accident. Vestn Akad Med Nauk SSSR. (11):32-6, 1991, in Russian) OvB BIODOSE-21, Hiroshima, Japan 12 June

27 Structure of the (Russian) National Radiation and Epidemiological Registry All-Union Registry of persons exposed to radiation Consists of information about people including Chernobyl liquidators in 1992 National Radiation and Epidemiological Registry The Registration List of persons exposed to radiation The Registry of Interdepartmental Expert Councils The Chernobyl Registry (since 1992 the Russian National Medical and Dosimetric Registry) (from Ivanov VK, Tsyb AF The Chernobyl accident and radiation risks: dynamics of epidemiological rates morbidity, disability and death rates according to the data in the national registry. World Health Stat Q 1996;49(1):22-28) OvB BIODOSE-21, Hiroshima, Japan 12 June

28 Registration groups of the Russian National Medical and Dosimetric Registry 4% Liquidators % Evacuees and the resettled Residents % 3% Childred born from liquidators of (from Ivanov VK, Tsyb AF The Chernobyl accident and radiation risks: dynamics of epidemiological rates morbidity, disability and death rates) according to the data in the national registry. World Health Stat Q 1996;49(1):22-28) OvB BIODOSE-21, Hiroshima, Japan 12 June

29 Part III. Doses...attempts to validate the official doses with sophisticated biological dosimetry methods have so far proved discouraging Science 272:360 OvB BIODOSE-21, Hiroshima, Japan 12 June

30 How dosimetric data was collected? Individual physical dosimetry - very rare Estimated doses (from maps of contamination and documents) in most cases Documented Individual doses Registry OvB BIODOSE-21, Hiroshima, Japan 12 June

31 Annual number of liquidators and their documented doses from the Russian National Medical and Dosimetric Registry Year of employment in the zone Number of liquidators Mean absorbed dose, Gy (from Ivanov V.K., Tsyb A.F. Chernobyl radiation risks: assessments of morbidity, mortality and disability rates according to the data of the National Radiation and Epidemiological Registry, Nagasaki Symposium Radiation and Human Health. Elsevier Science B.V., 1996: 31-42) OvB BIODOSE-21, Hiroshima, Japan 12 June

32 Distribution f(d) of external exposure doses for liquidators registered in the RNMDR All liquidators OvB BIODOSE-21, Hiroshima, Japan 12 June

33 Distribution f(d) of external exposure doses for 1986 liquidators registered in the RNMDR 1986 liquidators OvB BIODOSE-21, Hiroshima, Japan 12 June

34 Distribution f(d) of external exposure doses for 1987 liquidators registered in the RNMDR 1987 liquidators OvB BIODOSE-21, Hiroshima, Japan 12 June

35 Distribution f(d) of external exposure doses for 1988 liquidators registered in the RNMDR 1988 liquidators OvB BIODOSE-21, Hiroshima, Japan 12 June

36 Distribution f(d) of external exposure doses for 1989 liquidators registered in the RNMDR 1989 liquidators 5475 OvB BIODOSE-21, Hiroshima, Japan 12 June

37 Distribution f(d) of external exposure doses for 1990 liquidators registered in the RNMDR 1990 liquidators 1004 OvB BIODOSE-21, Hiroshima, Japan 12 June

38 Methods of retrospective biodosimetry Unstable chromosome aberration analysis. Stable chromosome aberration analysis with fluorescent in situ hybridisation (FISH). Stable chromosome aberration analysis with G-banding. Micronucleus tests. Glycophorin A test (GPA). HPRT mutation test (Moore, 1997). Tooth enamel electron spin resonance dosimetry. Minisatellite test (Dubrova 1996, Dubrova 1997). OvB BIODOSE-21, Hiroshima, Japan 12 June

39 Unstable chromosome aberration analysis The method is based on scoring unstable chromosome aberration (rings and dicentrics) in lymphocytes of peripheral blood. Due to the instability of these types chromosome aberration this method is useful only a few years (better - months) after irradiation. The threshold of sensitivity is about 0.1 Gy for whole body low LET radiation. OvB BIODOSE-21, Hiroshima, Japan 12 June

40 Stable chromosome aberration analysis (FISH) The method is based on scoring stable chromosome aberrations (translocations and insertions) detected with fluorescent in situ hybridisation of whole chromosomes. Requires complex procedures and technical equipment. May be use decades after exposure. The threshold of sensitivity is a few cgy but this method is not feasible for doses less than 0.2 Gy because of the expense and time needed for analyses. The spontaneous level of stable chromosome aberrations is not well established. OvB BIODOSE-21, Hiroshima, Japan 12 June

41 Glycophorin A somatic cell mutation assay Performed by two-colour immunofluorescence flow cytometry on peripheral blood erythrocytes. Based of measuring N/0 variants of erythrocytes, which display a phenotype consistent with loss of expression of the GPA (M) allele. Can be performed only on individuals who are heterozygous at this locus that codes for the N/M blood group antigens (approximately half of population). Very prompt but requires complex and expensive equipment. Threshold of sensitivity - about Gy. OvB BIODOSE-21, Hiroshima, Japan 12 June

42 Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry (RNMDR) and results of biodosimetry: liquidators Source Number Mean age, Physical Biodosimetry, Gy of people in 1996 dosimetry, Gy Un.Ch.A. 1 St.Ch.A. 2 RNMDR 3, 1986 liquidators Snigiryova, Bauchinger et al, 1997; 1986 liquidators Construction of sarcophagus Roof or vicinity of reactor, Granath, Natarajan month et al, 1996; Roof or vicinity of reactor, liquidators month km or beyond 30 km zone Pooled data CAPS staff ( ) Schevchenko, Physicians Burkart et al, 1996; Dosimetrists liquidators Drivers Sarcophagus builders Pooled data Sevan kaev, Lloyd et al, 1995; 1986 liquidators Sevan kaev, Lloyd et al, 1995; 1987 liquidators Vorobtsova et al, 1994; liquidators RNMDR 3 ; 1987 liquidators Unstable chromosome aberration test (Qdr) 2 Stable chromosome aberration test (FISH) 3 Russian National Medical and Dosimetric Registry, documented doses OvB BIODOSE-21, Hiroshima, Japan 12 June

43 Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry and results of biodosimetry: liquidators Source Number of people Mean age, in 1996 Physical dosimetry, Gy Biodosimetry 1, Gy RNMDR 2, 1988 liquidators Sevan kaev, Lloyd et al, ; 1988 liquidators RNMDR 2, 1989 liquidators Sevan kaev, Lloyd et al, 1995; 1989 liquidators Unstable chromosome aberration test (Qdr) 2 Russian National Medical and Dosimetric Registry, documented doses OvB BIODOSE-21, Hiroshima, Japan 12 June

44 Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry and results of biodosimetry: liquidators Source Number of Mean age, Physical Biodosimetry, Gy people in 1996 dosimetry, Gy St.Ch.A. 1 GPA 2 RNMDR 3, liquidators Snigiryova, Working Bauchinger et al, With documented 1997; doses Without documented liquidators doses Pooled data Bigbee, Tekkel et al, 1996; liquidators Stable chromosome aberration test (FISH) 2 Glycophorin A somatic cell mutation assay 3 Russian National Medical and Dosimetric Registry, documented doses OvB BIODOSE-21, Hiroshima, Japan 12 June

45 Multiple end-point assessment of the effects of exposure on the liquidators Multiple end-point assessment of the effects of exposure on the liquidators was performed using stable chromosome aberration analysis (FISH), the Glycophorin A test (GPA) and the HPRT mutation test during collaborative study between LLNL, Moscow and St. Petersburg scientists Correlation between the end points of the bioassays and documented doses was low and non-significant. No correlation was found between the different methods of biodosimetry. Dose estimation published only for stable aberration analysis. Source Number Year of Results of biodosimetry, Gy Calibration of people participation Un.Ch.A. (Dic) St.Ch.A. (FISH) G-banding curve Moore et al, ? 0.09 Own, LLNL Pilinskaya, Estimated Pilinskaya, from Lazutka, ? 0.50 Bender at al, 1988 (from Moore, D. H., 2nd, Tucker, J. D., Jones, I. M., Langlois, R. G., Pleshanov, P., Vorobtsova, I., Jensen, R. A study of the effects of exposure on cleanup workers at the Chernobyl nuclear reactor accident using multiple end points. Radiat Res : ) OvB BIODOSE-21, Hiroshima, Japan 12 June

46 Verification of the doses from RNMDR Prof. Ilyin applied the special statistical method based on the analyses of the dependency H(d)/Ind from d, where d is a step of the histogram of liquidators dose distribution, and H(d) is d-entropy of distribution. It was shown that 60% of registered individual doses for the whole contingent of the liquidators differ from the real exposure doses. It was estimated that 7% of the liquidators received doses of more than 0.25 Gy. Using the theory of hybrid lognormal distribution a real external dose distribution for the liquidators was obtained. Number of liquidators in a dose interval, %/LgD Distribution of external γ-rays doses for liquidators in 1986 according to RNMDR data (1) and results of Ilyin s calculation (2) (from Ilyin, LA, Kriuchkov, VP, Osanov, DP, Pavlov, DA The irradiation levels of the participants in the cleanup of the aftermath of the Chernobyl accident in and the verification of the dosimetric data. Radiats Biol Radioecol : , n Russian) Dose, Gy OvB BIODOSE-21, Hiroshima, Japan 12 June

47 Response from RNMDR Pitkevich et al published a paper with response to Prof.Ilyin s analysis: Pitkevich, VA, Ivanov, VK, Chekin, Siu, Tsyb, AF. Exposure levels of persons involved in cleaning-up after the Chernobyl AES accident and included in the Russian State Medical and Dosimetric Registry (letter). Radiats Biol Radioecol : (in Russian) The authors made the conclusion that the method of dose verification developed in the paper and based on d-entropy of statistical distribution failed to be scientifically founded. The second conclusion was that results present evidence that RNMDR data do not contain a considerable part of "distorted" values even if the above mentioned method is taken as valid. OvB BIODOSE-21, Hiroshima, Japan 12 June

48 Biodosimetry data 126 liquidators were examined by FISH in a collaborative study between LLNL, Moscow and St. Petersburg scientists. The shape of biodosimetry distribution is much different from that obtained using estimated doses from the liquidators dosimetry cards. The mean population exposure based on cytogenetic analysis is 9 cgy, while the mean based on the estimated doses is 25 cgy (range from 2 cgy to 2.7 Gy). Since detailed information on the source of the estimated doses is not available, authors are more inclined to believe the results of the biodosimetry. Distribution of exposure of liquidators to ionising radiation (from Moore, D. H., 2nd, Tucker, J. D., Jones, I. M., Langlois, R. G., Pleshanov, P., Vorobtsova, I., Jensen, R. A study of the effects of exposure on cleanup workers at the Chernobyl nuclear reactor accident using multiple end points. Radiat Res : ) OvB BIODOSE-21, Hiroshima, Japan 12 June

49 Do recorded doses overestimate true doses received by Chernobyl clean-up workers? Fluorescence in situ hybridisation has been applied to quantify stable chromosome aberrations among 118 Estonian clean-up workers (10.3 cgy mean recorded dose; 25 cgy maximum), 29 Estonian population controls and 21 American controls was conducted by three laboratories. A clear association with increased levels of stable chromosome aberrations was seen with increasing age and tobacco use No correlation with recorded doses. Authors conclude that recorded doses for Estonian clean-up workers substantially overestimate their average bone marrow doses. Future studies may not be sufficiently powerful to detect increases in leukaemia or cancer. (from Littlefield, L.G., McFee, A.F., Salomaa, S.I., Tucker, J.D., Inskip, P.D., Sayer, A.M., Lindholm, C., Makinen, S., Mustonen, R., Sorensen, K., Tekkel, M., Veidebaum, T., Auvinen, A. and Boice, J.D., Jr. (1998). Do recorded doses overestimate true doses received by Chernobyl cleanup workers? Results of cytogenetic analyses of Estonian workers by fluorescence in situ hybridization. Radiat Res, 150:2, ) OvB BIODOSE-21, Hiroshima, Japan 12 June

50 Overexposed groups Sarcophagus workers group is consisted of 15 scientists from Kurchatov Atomic Energy Institute, Moscow, who monitored status of the sarcophagus from 1986 to People who were on site during the accident ( early liquidators ). Some data of imitation modelling available from Institute of Biophysics of the Ministry of Health of the Russian Federation. Prof. Bauchinger examined a group of 12 highly irradiated early liquidators in HMGU (former GSF). OvB BIODOSE-21, Hiroshima, Japan 12 June

51 The Sarcophagus is the protective structure covering destroyed Reactor No. 4 "Elephant foot" - fuel form inside the reactor building The Sarcophagus, December 1986 OvB BIODOSE-21, Hiroshima, Japan 12 June

52 Dose estimates of sarcophagus workers No Year of Date of start work at Total physical Sampling Results of retrospective biodosimetry (Gy) birth Chernobyl Dose, Gy 1 Qdr 2 ESR Sept May Sept Sept Oct Aug Sept Aug Estimated with quartz fibre electrometers; 2 Unstable chromosome aberration test ; 3 Tooth electron spin resonance retrospective dosimetry A. Sevan'kaev, D. Lloyd, A. Edwards and V. Moiseenko (1995) High exposures to radiation received by workers inside the Chernobyl sarcophagus. Radiation Protection Dosimetry, 59:2, OvB BIODOSE-21, Hiroshima, Japan 12 June

53 A comparison of the results of dose estimation by the imitation modelling method with chromosome aberration biodosimetry in early liquidators Liquidators subgroup Time of staying Exposure rate, R/hour Imitation modelling dose, Gy Biodosimetry dose, Gy 1 Reactor hall workers 19 min h 32 min h 42 min Turbine 2 h 47 min hall workers 2 h 57 min h 27 min min h 20 min 2 h 00 min h 30 min 500 and Fire-fighters 3 h 25 min min h 50 min Construction 1 h 40 min workers on 5 2 h 00 min and 6 block 1 h 00 min h 00 min Collective dose Results of unstable chromosome aberration test (from Kruchkov V.P. and Nosovsky A.B., eds. Retrospective Dosimetry. Kiev, 1996.) OvB BIODOSE-21, Hiroshima, Japan 12 June

54 Prof. Bauchinger examined group of 12 highly irradiated victims with acute radiation syndromes No Year of birth Brief case report Results of biodosimetry (Gy) Qdr 1 FISH Worked at the reactor during the accident Worked within the power plant during the accident (40 m from the reactor) Worked outside the power plant during the accident (500 m from the reactor) Stayed for 3-4 h at about 50 m from the reactor Technician at the reactor during night of the accident Worked at the reactor during the accident Worked at the reactor during the accident Worked within the power plant during the accident (100 m from the reactor) Worked within the power plant during the accident (150 m from the reactor) Worked at the reactor during the accident Worked as watchman during the night of the accident, stayed close to the reactor for 1 day and 2 nights Arrived to work on the morning after the accident; worked 1 h at 400 m from the reactor Results of unstable chromosome aberration test; 2 Results of retrospective biodosimetry with stable chromosome aberration test K. Salassidis, E. Schmid, R. Peter, H. Braselmann and M. Bauchinger (1994) Dicentric and translocation analysis for retrospective dose estimation in humans exposed to ionising radiation during the Chernobyl nuclear power plant accident. Mutat Res, 311:1, OvB BIODOSE-21, Hiroshima, Japan 12 June

55 Sources of 1986 year liquidators collective dose based on analysis of the marching routs. A cohort from Institute of Biophysics, Moscow Collective dose of 1986 liquidators 100% Dose due to superficial exposure 5% Dose due to external exposure 95% Dose due to internal exposure Exposure from contaminated clothes Dose received % Dose received % Dose received due to professional activity 60% Dose received due to non-professional activity 19% Dose received during work 17% Dose received during transportation to the place of work 43% OvB BIODOSE-21, Hiroshima, Japan 12 June

56 Part IV. Conclusions A uniform, comprehensive, carefully planned and properly financed international program of study should be implemented within the framework of Russia, Belarus and Ukraine which, in addition to local scientists, would also involve leading experts from different countries around the world Ilyin L.A. Chernobyl: myth and reality. Moscow, Megapolis, 1995 OvB BIODOSE-21, Hiroshima, Japan 12 June

57 What we know about liquidators? Different estimation of liquidator numbers Some knowledge about physical documented doses Imitation modelling-dose estimates Some results of retrospective biodosimetry Diversity of opinions OvB BIODOSE-21, Hiroshima, Japan 12 June

58 Why? Possible reasons Doses received by liquidators were relatively small. Protracted irradiation has weaker effect. Information about physical doses is not reliable. Normal population is more resistant to irradiation than was assumed. Clean-up operations were extremely successful and protection of liquidators was efficient. Direct disinformation in the early stages of clean-up works by the Soviet authorities and the socio-political processes of the dissolution of the Soviet Union distorted the picture. The effects of the heavily affected subgroup of liquidators were diluted with a large number of non-affected people. OvB BIODOSE-21, Hiroshima, Japan 12 June

59 Conclusions The liquidator group is very heterogeneous. Documented physical doses and biodosimetry data are generally consistent of a level of about Gy for the whole group. The necessity of a large scale complex screening program for liquidators is evident. Monitoring the overexposed group of liquidators could give essential information concerning the consequences of the Chernobyl accident. Verification of documented doses e.g. by biodosimetry is essential. OvB BIODOSE-21, Hiroshima, Japan 12 June

60 Acknowledgments I am grateful to Prof.K.-R.Trott and Prof.F.Steinhäusler for their help and advice during my work on this report, to Prof.M.Robbins, Prof. M.Bauchinger, Dr.D.C.Lloyd, Dr.V.V.Moiseenko, Dr.M.Quastel, Dr.W.L.Bigbee and Radiation Research Society for help in literature search work. OvB BIODOSE-21, Hiroshima, Japan 12 June