IAEA International Atomic Energy Agency

Review of biodosimetry in Chernobyl liquidators

Oleg Belyakov Radiation Biologist

Applied Radiation Biology and Radiotherapy Section Division of Human Health

IAEA

Contents

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• Introduction • Chernobyl accident • Liquidators • Doses • Conclusions • Acknowledgments

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This presentation is based on the “Chernobyl Liquidators Project”, which was discontinued in 2000 and currently offline

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IAEA 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998

0

10

20

30

40

50

60

Num

ber o

f pub

lishe

d pa

pers

Year

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Annually published number of scientific liquidator related papers (source: Medline database)

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“...the most serious accident in the history of the nuclear industry...”

International conference: One decade after Chernobyl Vienna, Austria 8-12 April 1996

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Part I. Chernobyl accident

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1:23 am on Saturday, 26 April 1986

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(from “Chernobyl ten years on. Radiological and health impact”, NEA Committee on Radiation Protection and Public Health. OECD Nuclear Energy Agency, 1995)

Release rate of radioactive substances

Core inventory on 26 April 1986

Total release during the accident

Nuclide Half-life Activity (PBq)

Percent of

inventory

Activity (PBq)

Xe33 5.3 d 6 500 100 6500 I131 8.0 d 3 200 50 - 60 ~1760

Te132 78.0 h 2 700 25 - 60 ~1150 Cs134 2.0 y 180 20 - 40 ~54 Cs137 30.0 y 20 - 40 ~85 280

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(from “The International Chernobyl Project. Technical report”, IAEA 1991).

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.

Accident’s fall-out

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“... 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

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Part II. Liquidators

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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.

Synonyms for liquidators

LIQUIDATORS

EMERGENCY WORKERS

CLEAN-UP WORKERS

RECOVERY WORKERS

SALVAGE PERSONAL

DECONTAMINATION WORKERS

AMELIORATORS OF THE

CHERNOBYL ACCIDENT

RESCUERS OF CONSIQUENCES OF

CHERNOBYL’S DISASTER

MITIGATION WORKERS

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Liquidators - people who were directly involved in clean-up operations in the accident zone within 30 km from the destroyed reactor in 1986-1991. (from Ilyin L.A. Chernobyl: myth and reality. Moscow, “Megapolis”, 1995)

Definition

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• 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 >1.5x106 Bq/m2 (40 Ci/km2) and represents an area from where the population was evacuated in 1986-1987.

• The legal definition is criterion for inclusion in national medico-dosimetric Chernobyl registries.

The legal definition

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“...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 1986-1987, 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.”

IAEA definition, 1996

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300,000 - 320,000 Ilyin L.A. Chernobyl: myth and reality. Moscow, “Megapolis”, 1995.

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”, 1995

600,000 - 800,000 (about 200,000 in 1986-1987) International conference: “One decade after Chernobyl” Vienna, Austria 8-12 April 1996

293,100 All-Union (later State) Distribution Register (USSR, 1986-1989)

168,000 The Russian National Medical Dosimetric Registry, January 1, 1996

about 600,000 The radiological consequences of the Chernobyl accident. European Commission. Brussels, 1996

200,000 - 600,000 Scientific journal papers, 1988-1997

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How many?

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300 - 320 thousand people Ilyin L.A. Chernobyl: Myth and reality. Moscow, “Megapolis”, 1995.

The most realistic estimation

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Time oriented

Organisational structure

Task oriented

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Classifications of the Chernobyl liquidators

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26 April 1986 27 April 1986 November 1986 1991

The Chernobyl Accident

Evacuation of Pripyat

“Sarcophagus” construction was completed

Dissolution of the Soviet Union

Initial stage

Early liquidators

Late stage

Liquidators 1988-1991

Early stage

Liquidators 1986-1987

Stages of the clean-up

work

Time oriented grouping of liquidators

Events

Time

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Time scale of the Chernobyl accident clean-up work

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(from Ilyin L.A. Chernobyl: myth and reality. Moscow, “Megapolis”, 1995)

Liquidators of different years. Data from All-Union (later State) Distribution Register

Year Number of liquidators

1986 138,390 1987 85,556 1988 26,134 1989 43,020

1986-1989 293,100

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1986 1987 1988 1989

Other groups of liquidators about 300 000

People who were at the site during the

explosion

476 persons of staff, including 200 members on-duty personnel CNPS

About 300 construction workers (at the 5th construction site)

“Samoilenko group” - the roof of

the third unit - about 5000

Sarcophagus builders - a few tens of thousands people

Sarcophagus workers, 15

Types of liquidators and level of exposure

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Dose increase

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KGB USSR

Federal Counter- Intelligence Service

(1,093 persons)

Liquidators 300 000±20 000 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.

20% 80% 20,508 persons 90,000 persons

Military and paramilitary

Reservists

Servicemen

Professional military

(mainly officers)

Police

USSR Ministry of the Interior Affairs, 1991

(32, 111 persons)

Ministry of Interior Affairs of the Russian

Federation (3,326 persons)

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.)

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How many?

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Medical department of Operative group of the Belorussky (Belorusian) Military District (sector 2)

Operative group of the Central Military Medical department

of the Defence ministry

Medical department of Operative group of the Defence ministry

Departments 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)

Medical department of Operative group of the Kievsky (Kiev) Military District (sector 2)

management, co-ordination, interaction radiation safety control scientific-methodological support co-ordination of the radiation control work on Chernobyl NPP

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.

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.

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Interaction of medical departments of military “operative groups” during clean up work after the Chernobyl accident

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1Ivanov 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, 1995. Nagasaki Symposium Radiation and Human Health. Elsevier Science B.V., 1996: 31-42.

2Liktarev I.A., Chumak V.V. Overview of the Chernobyl liquidator database. 44th 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”, 1995. 4Bigbee 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 27.

5The National Chernobyl Registry of Russia, as quoted by Liktarev and Chumak2. 6The national registry of Ukraine

Russia1 Russia2 Belorus3 Ukraine 2 Baltic Countries4 Estonia Latvia Lithuania

1986-1989 1986-1987 1986-1996 1986-1987 mainly 1986-1987 118 335 152 0005 63500 123 5366 4836 5709 5446

Cohorts of liquidators

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• 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 women-liquidators 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, 936-41.

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, 149-60.

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

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Sex distribution of the Chernobyl liquidators

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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, 1986-1995. Health Phys, 74:3, 309-15)

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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 15-19 2,180 1,9 20-24 8,905 7,78 25-29 4,097 12,31 30-34 36,323 31,72 35-39 37,116 32,41 40-44 11,587 10,12 45-49 3,294 2,88 50-54 664 0,58 55-59 263 0,23 ≥60 75 0.00

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• Large scale projects

i.e. The International Chernobyl Project, 1991 (IAEA), 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

• Registries USSR medical registers

USSR ministry's registers

All Union (later State) Distribution Register

National registers

Russian National Medical and

Dosimetric Registry

Other national registers: Belorusian, Ukrainian, Estonian,

Latvian, and Lithuanian

Immigrant registers:

USA-Canada Chernobyl Immigrant Registry

Israeli registry

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Sources of information

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(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)

Sub-regional Hospital

Regional Hospital

Ministry of Health in Republics

Soviet Union Registry Ministry of Health

Ministry Registers

Ministry of Defence USSR

Ministry of Internal Affairs USSR

KGB USSR

Transport Ministry USSR

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Hierarchical structure of the All-Union (later State) Distribution Register

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National Radiation and Epidemiological Registry

The Registry of Interdepartmental Expert Councils

The Registration List of persons exposed to radiation

All-Union Registry of persons exposed to radiation Consists of information about 659 292 people including 284 919 Chernobyl liquidators in 1992

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)

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Structure of the (Russian) National Radiation and Epidemiological Registry

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(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)

35%

3%58%

4%Liquidators 152 325

Evacuees and theresettled 12 889

Residents 251 246

Childred born fromliquidators of 1986-1988 18 816

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Registration groups of the Russian National Medical and Dosimetric Registry

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“...attempts to validate the official doses with sophisticated biological dosimetry methods have so far proved discouraging”

Science 272:360

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Part III. Doses

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How dosimetric data was collected?

Documented “Individual”

doses

Registry

Individual physical

dosimetry - very rare

Estimated doses (from maps of contamination

and documents) in most cases

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(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, 1995. Nagasaki Symposium Radiation and Human Health. Elsevier Science B.V., 1996: 31-42)

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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

1986 46 575 0.159 1987 48 077 0.0895 1988 18 208 0.033 1989 5 475 0.032

1986-1989 118 335 0.105

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Distribution f(D) of external exposure doses for liquidators 1986-1990 registered in the RNMDR

All liquidators 119 426

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Distribution f(D) of external exposure doses for 1986 liquidators registered in the RNMDR

1986 liquidators 46 575

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Distribution f(D) of external exposure doses for 1987 liquidators registered in the RNMDR

1987 liquidators 48 077

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Distribution f(D) of external exposure doses for 1988 liquidators registered in the RNMDR

1988 liquidators 18 208

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Distribution f(D) of external exposure doses for 1989 liquidators registered in the RNMDR

1989 liquidators 5475

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Distribution f(D) of external exposure doses for 1990 liquidators registered in the RNMDR

1990 liquidators 1004

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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).

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• 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.

Unstable chromosome aberration analysis

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• 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.

Stable chromosome aberration analysis (FISH)

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• 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 0.2-0.25 Gy.

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Glycophorin A somatic cell mutation assay

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Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry (RNMDR) and results of biodosimetry: liquidators 1986-1987

Source Number Mean age, Physical Biodosimetry, Gy of people in 1996 dosimetry, Gy Un.Ch.A.1 St.Ch.A.2

RNMDR3, 1986 liquidators 46 575 43 0.159 Snigiryova, Bauchinger et al, 1997; 1986 liquidators 35 41 0.19 0.23 0.19

Construction of sarcophagus 5 0.07 Granath, Natarajan

Roof or vicinity of reactor, 4-7 month

5 0.31

et al, 1996; 1986 liquidators

Roof or vicinity of reactor, 0-3 month

5 0.27

10-30 km or beyond 30 km zone

11 0.15

Pooled data 26 0.19 CAPS staff (1986-1987) 83 0.322

Schevchenko, Physicians 37 0.150 Burkart et al, 1996; Dosimetrists 23 0.267

1986 liquidators Drivers 60 0.178 Sarcophagus builders 71 0.244 Pooled data 274 0.242

Sevan’kaev, Lloyd et al, 1995; 1986 liquidators 601 0.2 Sevan’kaev, Lloyd et al, 1995; 1987 liquidators 175 0.15 Vorobtsova et al, 1994; 1986-1987 liquidators 161 0.2

RNMDR3; 1987 liquidators 48 077 43 0.089

1 Unstable chromosome aberration test (Qdr) 2 Stable chromosome aberration test (FISH) 3 Russian National Medical and Dosimetric Registry, documented doses

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Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry and results of biodosimetry: liquidators 1988-1989

Source Number of people

Mean age, in 1996

Physical dosimetry, Gy

Biodosimetry1, Gy

RNMDR2, 1988 liquidators 18 208 43 0.033 Sevan’kaev, Lloyd et al, 1995; 1988 liquidators

60 0.15

RNMDR2, 1989 liquidators 5 475 43 0.032 Sevan’kaev, Lloyd et al, 1995; 1989 liquidators

16 0

1 Unstable chromosome aberration test (Qdr) 2 Russian National Medical and Dosimetric Registry, documented doses

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Comparison of dosimetry data from the Russian National Medical and Dosimetric Registry and results of biodosimetry: liquidators 1986-1989

Source Number of Mean age, Physical Biodosimetry, Gy people in 1996 dosimetry, Gy St.Ch.A.1 GPA2

RNMDR3, 1986-1989 liquidators 118 335 43 0.105 Snigiryova, Working 1986-1995 17 51 0.39

Bauchinger et al, 1997;

With documented doses 34 45 0.26 0.27

1986-1989 liquidators

Without documented doses 17 45 0.27

Pooled data 1986-1995 52 44 0.27

Bigbee, Tekkel et al, 1996; 1986-1989 liquidators

782 0.04-0.08

1 Stable chromosome aberration test (FISH) 2 Glycophorin A somatic cell mutation assay 3 Russian National Medical and Dosimetric Registry, documented doses

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(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 1997 148:5 463-75)

• 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 .

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Multiple end-point assessment of the effects of exposure on the liquidators

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, 1997 126 1986-1989? 0.09 Own, LLNL Pilinskaya, 1996 125 1986 0.07 Estimated Pilinskaya, 1996 10 1986 0.30 from Lazutka, 1995 33 1986-1989? 0.50 Bender at al,

1988

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• 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.

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 1986-1987 and the verification of the dosimetric data. Radiats Biol Radioecol 1995 35:6 803-28 , n Russian)

Dose, Gy

Number of liquidators in a dose interval, %/LgD

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Verification of the doses from RNMDR

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• 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 1996 36:5 747-57 (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”.

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Response from RNMDR

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•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 1997 148:5 463-75)

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Biodosimetry data

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• 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, 237-49)

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Do recorded doses overestimate true doses received by Chernobyl clean-up workers?

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• Sarcophagus workers group is consisted of 15 scientists from Kurchatov Atomic Energy Institute, Moscow, who monitored status of the sarcophagus from 1986 to 1995.

• 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).

Overexposed groups

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"Elephant foot" - fuel form inside the reactor

building

The Sarcophagus, December 1986

The Sarcophagus is the protective structure covering destroyed Reactor No. 4

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1 Estimated with quartz fibre electrometers; 2 Unstable chromosome aberration test ; 3 Tooth electron spin resonance retrospective dosimetry

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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, 85-91 .

Dose estimates of “sarcophagus workers”

No Year of Date of start work at

Total physical

Sampling Results of retrospective biodosimetry (Gy)

birth Chernobyl Dose, Gy1 Qdr2 ESR3 1992 13.1 -

1 1958 Sept 1988 11.6 1993 12.2 - 1994 12.6 - 2 1947 May 1986 17.1 1992 8.4 9.3

1994 8.0 - 1991 4.1 3.7 3 1933 Sept 1986 3.6 Sept 1992 3.3 - Oct 1992 6.0 - 1993 4.7 - 4 1955 Aug 1986 2.0 1991 2.7 - 1992 5.5 - 5 1956 Sept 1989 1.5 1991 1.0 - 6 1946 Aug 1989 0.9 1991 0.5 -

IAEA (from Kruchkov V.P. and Nosovsky A.B., eds. Retrospective Dosimetry. Kiev, 1996.)

OvB BIODOSE-21, Hiroshima, Japan 53 12 June 2013

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, Gy1

Reactor hall workers 19 min 1800 3-6 2.6 2 h 32 min 400-600 5-15 10.9 1 h 42 min 400-600 3.5-10.5 10.1

Turbine 2 h 47 min 100-200 1.4-5.6 8.7 hall workers 2 h 57 min 400 5.9-12 8.2

1 h 27 min 400 3.0-6.0 7.5 45 min –

1 h 20 min 400 1.5-5.3 3.6

2 h 00 min 600 6.0-12.0 7.1 1 h 30 min 500 and 1000 5.6-11.3 12.5

Fire-fighters 3 h 25 min 50 0.85-1.7 0.8 40 min 1500 5-10 10 1 h 50 min 300 2.8-5.5 2.8

Construction 1 h 40 min 150-200 1.3-3.4 3.4 workers on 5 2 h 00 min 150-200 1.5-4.0 2.2 and 6 block 1 h 00 min 180-240 0.9-2.4 2.1

3 h 00 min 180-240 2.7-7.2 4.0 Collective dose - - 50-139 97

1 Results of unstable chromosome aberration test

IAEA OvB BIODOSE-21, Hiroshima, Japan 54 12 June 2013

Prof. Bauchinger examined group of 12 highly irradiated victims with acute radiation syndromes

1 Results of unstable chromosome aberration test; 2 Results of retrospective biodosimetry with stable chromosome aberration test

No Year of birth Brief case report Results of biodosimetry (Gy)

Qdr1 FISH2

1 1931 Worked at the reactor during the accident 4.9 4.4

2 1950 Worked within the power plant during the accident (40 m from the reactor) 3.3 3.1

3 1959 Worked outside the power plant during the accident (500 m from the reactor) 3.9 2.8

4 1945 Stayed for 3-4 h at about 50 m from the reactor 5.1 4.0 6 1941 Technician at the reactor during night of the accident 4.0 3.8 7 1960 Worked at the reactor during the accident 3.5 1.9 8 1957 Worked at the reactor during the accident 2.3 1.6

9 1960 Worked within the power plant during the accident (100 m from the reactor) 5.8 4.3

10 1913 Worked within the power plant during the accident (150 m from the reactor) 3.3 3.4

11 1959 Worked at the reactor during the accident 2.6 2.0

13 1964 Worked as watchman during the night of the accident, stayed close to the reactor for 1 day and 2 nights 2.4 2.1

13 1938 Arrived to work on the morning after the accident; worked 1 h at 400 m from the reactor 1.1 2.2

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, 39-48 .

IAEA

Collective dose of 1986 liquidators

100%

Dose received due to professional activity

60%

Dose received due to non-professional activity

19%

Dose received 26.04.86-04.04.86

79%

Dose received 05.05.86-31.12.86

16%

Exposure from contaminated

clothes

Dose due to external exposure

95%

Dose due to superficial exposure

5%

Dose due to internal exposure

Dose received during work

17%

Dose received during transportation to the place of work

43%

OvB BIODOSE-21, Hiroshima, Japan 55 12 June 2013

Sources of 1986 year liquidators’ collective dose based on analysis of the marching routs. A cohort from Institute of Biophysics, Moscow

IAEA

“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 56 12 June 2013

Part IV. Conclusions

IAEA

• 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 57 12 June 2013

What we know about liquidators?

IAEA

• 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 58 12 June 2013

Why? Possible reasons…

IAEA

Conclusions

OvB BIODOSE-21, Hiroshima, Japan 59

• The liquidator group is very heterogeneous . • Documented physical doses and biodosimetry

data are generally consistent of a level of about 0.1-0.2 Gy for the whole group.

• The necessity of a large scale complex screening program for liquidators 1986-1987 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.

12 June 2013

IAEA

Acknowledgments

OvB BIODOSE-21, Hiroshima, Japan 60

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.

12 June 2013