THE INTERNATIONAL CHERNOBYL PROJECT · International Chernobyl Project described in the present Overview and monitored its implementation. The aims of The aims of the Project were

THE INTERNATIONALCHERNOBYL PROJECT

AN OVERVIEW

ASSESSMENT OF RADIOLOGICAL CONSEQUENCESAND EVALUATION OF PROTECTIVE MEASURES

REPORT BY AN INTERNATIONAL ADVISORY COMMITTEE

THE INTERNATIONAL CHERNOBYL PROJECT

AN OVERVIEW

Assessment of Radiological Consequencesand Evaluation of Protective Measures

Report by an International Advisory Committee

ST1/PUB/884

ISBN 92-0-129091-8

Printed by the IAEA in Vienna

© IAEA, 1991

THE INTERNATIONAL CHERNOBYL PROJECT

AN OVERVIEW

Assessment of Radiological Consequencesand Evaluation of Protective Measures

Report by an International Advisory Committee

Acknowledgements

The International Advisory Committee wishes to thank the large number of people who were involved in somany different ways in the International Chernobyl Project — the governments, institutions and organizations whodonated the time of their staff and the many individuals who gave of their own time for this important work. Gratitudeis expressed to the governments and commercial companies which provided equipment and supplies, without whichsome major parts of the work could not have been carried out. The complete acknowledgement list is included inthe Technical Report.

It is impossible to overestimate the value of the assistance and contribution of the many authorities at the Ail-Union and Republic levels, and the scientists, experts, technical and administrative staff and members of the publicwho co-operated with the visiting Project teams. Thanks are also due to the population and the authorities (includingphysicians, nurses and other staff of hospitals and polyclinics) in the settlements visited.

A considerable debt of gratitude is due to the IAEA Secretariat, who overcame the many difficulties inherentin an effort of such complexity.

Prefaceby the Chairman of the

International Advisory Committee

It was my privilege to act as Chairman of the International Advisory Committee (IAC), which was composedof prominent experts in different fields. They were called together by the various participating organizations of theUnited Nations system and the Commission of the European Communities. The IAC approved the work plan for theInternational Chernobyl Project described in the present Overview and monitored its implementation. The aims ofthe Project were to examine assessments of the radiological and health situation in areas of the USSR affected bythe Chernobyl accident and to evaluate measures to protect the population.

The task assigned to the IAC was a formidable one. There were unavoidable constraints on the time, man-power and funds available for the assignment. The Project was centred on questions of continuing mass relocationof people and sought to provide sound scientific bases for decisions yet to be made.

The Project teams applied their collective expertise and experience to sort facts from misconceptions andradiation effects from effects not related to radiation exposure. They obtained and examined vast quantities of datain their task to understand the present situation and to draw conclusions on the further steps that might be takento alleviate the consequences of the Chernobyl accident.

The IAC set out to conduct an independent, scientifically authoritative study and to provide a readily under-standable report that could assist the authorities in deciding how to proceed. Only time will show the significanceof our contribution.

My profound thanks go to all those who contributed to this work: the members of the Committee; theconsultants; the task leaders; the team leaders and all the experts who participated; the secretariat of the Project;and the many officials of the USSR, the BSSR, the RSFSR and the UkrSSR who gave their time and efforts to assistthe Project.

Itsuzo ShigematsuRadiation Effects Research Foundation

Hiroshima, Japan

Editorial NoteThis Overview presents the conclusions and recommendations of the International Advisory Committee which

directed the project on the Radiological Consequences in the USSR from the Chernobyl Accident: Assessment ofHealth and Environmental Effects and Evaluation of Protective Measures (hereinafter referred to as 'the InternationalChernobyl Project'). For a more detailed scientific account, the reader is referred to the full Technical Report, in whichthe various technical chapters have been written by the relevant task leaders of the Project. It is the primary authorita-tive document of the Project. While the wording of the conclusions and recommendations presented in the Overviewhas been agreed upon by the members of the Committee, the additional parts of the document were compiled fromthe Technical Report and provide a summary of the evidence on which the conclusions and recommendations arebased.

CONTENTS

Chapter One: The International Chernobyl Project 1

Chapter Two: Environmental Contamination 10

Chapter Three: Radiation Exposure of the Population 19

Chapter Four: Health Impact 27

Chapter Five: Protective Measures 36

Appendix: Historical Portrayal 47

Epilogue 55

International Advisory Committee 57

Chapter One:The International Chernobyl Project

Introduction

The accident at the Chernobyl power plant occurredon 26 April 1986. A brief chronology of some relevantevents up to the inception of the International ChernobylProject is given overleaf and a more extensive accountis presented in the Appendix.

In October 1989, the Government of the USSR for-mally requested the International Atomic EnergyAgency (IAEA) to carry out:

"... an international experts' assessment of theconcept which the USSR has evolved to enable thepopulation to live safely in areas affected by radio-active contamination following the Chernobylaccident, and an evaluation of the effectiveness of thesteps taken in these areas to safeguard the health ofthe population."

The response was a proposal for a multinational team toundertake an assessment of the radiological situation inthe three affected Soviet Republics — the UkrainianSoviet Socialist Republic (UkrSSR), the ByelorussianSoviet Socialist Republic (BSSR) and the Russian SovietFederated Socialist Republic (RSFSR). The Interna-tional Chernobyl Project was thus arranged, with theparticipation of the Commission of the European Com-munities (CEC), the Food and Agriculture Organizationof the United Nations (FAO), the International LabourOffice (ILO), the United Nations Scientific Committeeon the Effects of Atomic Radiation (UNSCEAR), theWorld Health Organization (WHO) and the WorldMeteorological Organization (WMO). The Project wasformalized at a February 1990 meeting in Moscow at theheadquarters of the USSR State Committee on the Utili-zation of Atomic Energy. Some twenty-five representa-

tives of the USSR, the BSSR, the UkrSSR and the IAEAtook part in discussions on the goals of the Project andthe methods to be used in achieving them.

The Government of the USSR had already benefitedfrom international assistance with this problem. TheWHO sent a team of experts in June 1989, as did theLeague of Red Cross and Red Crescent Societies in early1990. The final report of the WHO group concludedinter alia that: "... scientists who are not well versedin radiation effects have attributed various biological andhealth effects to radiation exposure. These changescannot be attributed to radiation exposure, especiallywhen the normal incidence is unknown, and are muchmore likely to be due to psychological factors and stress.Attributing these effects to radiation not only increasesthe psychological pressure in the population and pro-vokes additional stress related health problems, it alsoundermines confidence in the competence of the radia-tion specialist." The Report of the League of Red Crossand Red Crescent Societies indicated inter alia that:"Among the health problems reported it was felt thatmany of these, though perceived as radiation effects bothby the public and by some doctors, were unrelated toradiation exposure. Little recognition appears to havebeen given to factors such as improved screening of thepopulation and changed patterns of living and of dietaryhabits. In particular, psychological stress and anxiety,understandable in the current situation, cause physicalsymptoms and affect health in a variety of ways."

It was clear that the assessment of the Chernobyl acci-dent had already involved extensive efforts and it wouldnot be necessary for the Project to undertake a totallynew, comprehensive assessment of the situation. Rather,the task would be to assess the quality and correctnessof the existing results. Secondly, to be manageable, the

1

Chapter One: The International Chernobyl Project

CHRONOLOGY OF MAJOR EVENTS

26 April 1986

27 April 1986

6 May 1986

6 May 1986

6 May 1986

31 May 1986

May 1986

July 1986

November 1986

- 1987 -

Accident occurs 01:23. Governmen- April 1987tal Commission formed

Evacuation of Pripyat takes place

End of 10 days of atmospheric December 1987release of radioactive material fromthe core

Introduction of 'temporary permissi- _ble levels' for drinking water andfoodstuffs

Evacuation of the population withinthe prohibited zone completed

Revision of 'temporary permissiblelevels'

'Temporary dose limits' for thepopulation set at 100 mSv (internaland external) annual total dose

First summarized contamination map(not published until 1989)

•Completion of the 'sarcophagus'construction

'Temporary dose limits' for thepopulation reduced to 30 mSv annualtotal dose (subsequently lowered to25 mSv for 1988)

September 1988

March 1989

April 1989

October 1989

Completion of the work begun inMay 1986 for protecting the watersystem

Revision of the 'temporary per-missible levels' established 31 May1986

'Temporary dose limits' for thepopulation reduced to 25 mSv annualtotal dose

Council of Ministers of USSR adoptsthe 350 mSv lifetime dose forrelocation to be implemented as of1 January 1990

Contamination maps officially pub-lished in the three Republics

BSSR Academy of Sciences registersdisagreement with the 350 mSv life-time dose concept and makes newproposals

USSR requests the IAEA to organizean international assessment of theconsequences of the accident and theprotective measures taken

international assessment would have to focus on the keyissues of concern to the population and policy makers,namely: the true extent of the contamination; the past,current and future radiation exposure of the population;the actual and potential health effects; and the adequacyof measures being taken to protect the public.

The work of recommending an approach for examin-ing these issues was given to a group of ten scientists,who, accompanied by two members of the USSR

Supreme Soviet, travelled on a fact finding missionthrough the affected Republics over the period25-30 March 1990. Their visit enabled them to learnfirst hand about the requirements of the Project. Thegroup met with officials in Moscow and the Republiccapitals and with representatives of scientific organiza-tions, hospitals, clinics and agricultural centres in theaffected areas and in the cities of Kiev, Gomel andMoscow.


But it was in the encounters with the people of theUSSR, from the first meeting at the airport in Kiev to thelast question at a packed town hall, that the dimensionsof the task became clear. Plans for the Project werepresented to residents of seven settlements in the threeRepublics, who were invited to share their feelings andask questions. The international scientists found them-selves responding to very human concerns. Anxietyabout children's health and worries over the adequacy ofthe Government's proposed measures for limiting theradiation exposures over their lifetime dominated thediscussions. There was an atmosphere of mistrustdirected at the authorities and also at many in thescientific and medical communities.

Following the visit, an International Advisory Com-mittee of scientists from ten countries and seven interna-tional organizations was established to direct the Projectand be responsible for its findings. Members were calledtogether by international organizations participating inthe Project from well known institutes and universitiesto represent a spectrum of disciplines, from the radiationspecialist to the medical practitioner and the psycho-logist. The twenty-one member Committee met in Kievand Minsk from 23 to 27 April 1990 under the chair-manship of Dr. Itsuzo Shigematsu, Director of theRadiation Effects Research Foundation in Hiroshima,Japan.

The Committee agreed upon a detailed work plan.This would be constrained by a compelling need to com-plete the project in one year and by the limitation on theresources available. The Committee would need to relyon the availability of specialized professionals whowould volunteer their time.

Goals and Scope

The International Chernobyl Project was not intendedto have the rigour and comprehensiveness of anelaborate long term research study. Nor was it evenremotely intended to duplicate the voluminous existing

assessments of the environmental contamination, theradiation exposures of the population and possible healtheffects due to exposures resulting from the accident. Theintention was to have a multidisciplinary group of inter-national experts critically examine the extensive infor-mation, address the key issues and put together anunderstandable picture of the current situation.

The goals of the Project, in short, were to examineassessments of the radiological and health situation inareas of the USSR affected by the Chernobyl accidentand to evaluate measures to protect the population.

Thirteen districts in the USSR have been officiallyidentified as having a ground level l37Cs contaminationin excess of 1 Ci/km2 (37 kBq/m2)1. Approximately25 000 km2 are defined as affected areas with groundconcentration levels of l37Cs in excess of 5 Ci/km2

(185 kBq/m2). Of this total, approximately 14 600 km2

are located in the BSSR, 8100 km2 in the RSFSR and2100 km2 in the UkrSSR. The Project deals with theseaffected areas. It was not in its terms of reference toexamine the prohibited region (approximately 30 km inradius) around the damaged reactor itself, except todescribe the measures taken to contain the accident in theearly post-accident phase. It deals exclusively with theradiological consequences for the people living in theaffected areas at the time the assessment began in 1990.From official USSR reports, this population is approxi-mately 825 000, of which 45 per cent live in the BSSR,24 per cent in the RSFSR and 31 per cent in the UkrSSR.

Work Plan

The work plan adopted called for examining thevalidity of the official methodologies and findings, and

' Units of the Systeme international d'unites (SI) aregenerally used worldwide. However, in the USSR earlier unitsare still used and the original data were usually presented inthese units. The data in this Overview are therefore expressedin both units.


10000

8000

6000

1a(D

< 4000

2000

Q

-

_

_

-

—

n—

n n •

IUUU

800

U)

c0>

I 600

ito

~o

| 400E3Z

200

927(2!

-

_

_

-

)72 )0) (Number of people)

413(113100)

330 I — I(95700)

—

70(9700)

n

202167 (204200)

(80900)

6726 (29700) 23

(4600) f— I (19200)r— i 1 1

BSSR RSFSR UkrSSR BSSR RSFSR UkrSSR

!37Cs surface contamination

| | 185-555 kBq/m2 (5-1 S> Ci/km2)

| | 555-1480 kBq/m2 (15-40 Ci/km2)

^ > 1480 kBq/m2 (> 40 Ci/km2)

Geographical framework. The international assess-ment focused on the approximately 25 000 km2 inthe BSSR, the RSFSR and the UkrSSR officiallyreported to have a caesium surface contaminationlevel in excess of 185 kBq/m2 (5 Ci/km2) andparticularly on those areas with a level greater than1480 kBq/m2 (40 Ci/km2). The assessment excludedthe prohibited zone (30 km in radius) around theChernobyl reactor. [Doc. A/45/342 E/1990/102,United Nations Economic and Social Council,Geneva, 9 July 1990.]

i37Cs surface contamination

| | 185-555 kBq/m2 (5-15 Ci/km2)

| | 555-1480 kBq/m2 (15-40 Ci/km2)

> 1480 kBq/m2 (> 40 Ci/km2)

Demographic framework. The international assess-ment addressed the radiological consequences for theapproximately 825 000 people living in 2225 settle-ments in the BSSR, the RSFSR and the UkrSSR. It didnot include those people who had lived in contami-nated areas but had since moved from those areas.Nor did the Project address possible consequencesfor the so-called 'liquidators', i. e. the recovery wor-kers occupationally exposed at the Chernobyl plantsite. [Doc. A/45/342 E/1990/102, United NationsEconomic and Social Council, Geneva, 9 July 1990.]


February 1990

Preliminary meeting

March 1990

Preparation

Work plan

Implementation

Fact finding mission

April 1990

International Advisory Committee meeting

May 1990 - January 1991

Work plan implementation

Environmentalcontamination

February 1991

Draft report

Final report

Report preparation

March 1991

International Advisory Committee meeting

21-24 May 1991

International conference

The International Chernobyl Project. The Project was organized in response to a USSR Government requestfor an international assessment of the radiological consequences of the Chernobyl accident. The multinationaleffort was directed by the International Advisory Committee and included the participation of the CEC, FAO,IAEA, ILO, UNSCEAR, WHO and WMO. Five tasks defined the Project implementation: historical portrayal ofthe events leading to the current radiological situation, the evaluation of the environmental contamination, the

evaluation of the radiation exposure of the population, the assessment of the health impact from radiationexposures and the evaluation of the protective measures.


independently verifying them through field samples,laboratory analyses and internationally recognized cal-culational techniques. A portrayal of the major historicalevents would also be prepared to provide the necessarybackground to more fully understand the complexity ofthe situation and the interrelated nature of the Project'sgoals.

The work covered five areas or 'tasks':

Task 1: Compilation of a historical portrayal ofevents leading to the current radiologicalsituation (see Appendix)

Task 2: Evaluation of the environmental contamina-tion assessments

Task 3: Evaluation of the radiation exposureassessments

Task 4: Assessment of clinical health effects fromradiation exposure and evaluation of thegeneral health situation

Task 5: Evaluation of protective measures

The Project selected, in co-operation with localauthorities, a number of settlements in the contaminatedareas of concern in order to perform the necessarysurveys. Some of the settlements were located in areasof relatively high soil surface contamination while otherswere located in areas of relatively low soil surface con-tamination but with the potential for high radiation dosesto people. In this Overview, these settlements are called'surveyed contaminated settlements'.

Settlements were also selected outside the contami-nated areas of concern to serve as references for com-parative purposes. These settlements are called'surveyed control settlements'.

The surveyed contaminated settlements were:

BraginDaletaGdenGomelKhojniki

NovozybkovNovye BabovichiOvruchPolesskoeRakitnoe

KomrinKorchevkaKormaMalozhinMichul'nyaMikulichiMilchaNarodichiNovoe Mesto

SavenkiSavichiSlovechnoStaroe Vasil'kovoStarye BabovichiSvyatskVeprinZhatkaZlynka

The surveyed control settlements were:

ChemerKhodichiKirovskKrasilovka

SurazhTrokovichiUnecha

Not all the settlements were used in all the tasks ofthe Project.

A parallel consideration was the desire of the affectedpopulation to receive practical information about howthey could deal with the radiological situation. Projectexperts concluded that there was a poor understanding inthe affected areas of the scientific principles underlyingradiation and its effects (as is generally the case through-out the world) and that this was at the root of many ofthe medical and social problems observed. Therefore, inaddition to the main tasks of the Project, several infor-mation exchange activities were carried out in order toenhance the level of understanding among the localscientific community of the problems involved.

Participation

The Project was carried out on a completely volun-tary basis by a closely co-operating team of some200 experts associated with research institutes, universi-ties and other organizations in 25 countries and 7 multi-


INFORMATION EXCHANGE ACTIVITIES

MEDICAL SEMINARS

Three-day seminars were held in July 1990 in a numberof villages in each of the three Republics to broaden theknowledge of the general practitioners and health adminis-trators. More than 1200 local experts joined the visitingteam of four international specialists in discussing theresults of long term studies on radiation induced and relatedillnesses, the ways such illnesses can be diagnosed andtreated and the methods that are used to study cancer andother diseases in populations exposed to radiation.

AGRICULTURAL ACTIVITIES

A fact finding mission to the USSR in August 1990 iden-tified the concerns of farmers and farm workers aboutliving and working in a contaminated agricultural environ-ment. At a one-week workshop in Norway in September1990, USSR agricultural scientists and ministry officialsfrom the three Republics learned about Norwegian tech-niques for reducing caesium contamination in milk and

meat derived from grazing animals and a series of trialsusing so-called caesium binders were started. DuringOctober and November, a series of one-day seminars wereheld in villages in the three affected Republics, with Projectexperts discussing with some 1300 collective fanners, farmworkers, veterinarians and others from the local agricul-tural community how to use these practical methods andother techniques for soil management in contaminatedenvironments.

RADIOECOLOGY SEMINAR

To help local experts better understand the assessmentof human radiation exposures following environmentalreleases of radionuclides, a five-day seminar was held inKiev in January 1991. More than 200 specialists in radiobi-ology, radioecology, environmental science and publichealth from the three affected Republics took part in discus-sions on such topics as environmental monitoring, thebehaviour of radionuclides in the biosphere and therelevance of these nuclides for people.

national organizations. The time devoted to the Projectwas volunteered by governments, institutes, companiesor the experts themselves. Nearly 50 missions to theUSSR were completed between March 1990 and January1991. The IAEA Laboratory at Seibersdorf along with13 laboratories in six countries participating on a volun-tary basis were involved in the collection and analysis ofsamples. The Laboratory carried out an intercomparisonexercise with participating laboratories from the USSR.Governmental authorities and commercial companies infive countries donated equipment and supplies, radiationmonitors and computing time to back up the Projectwork.

The Project received the full support of the USSRGovernment and the Governments of the BSSR, theRSFSR and the UkrSSR. Assistance took various forms,including the participation of local scientists in intercom-parison exercises, extensive discussions with Projectscientists, and assistance in the collection and prepara-tion of field samples and in carrying out medical exami-nations of the population in the affected areas. Most ofthe logistic support for the Project was provided by theUSSR Ministry of Atomic Power and Industry. Therewere open and frank conversations with authorities,scientists and especially local citizens that greatly helpedthe international experts' understanding of the situation.


Constraints and Limitations

The conclusions and recommendations of theInternational Chernobyl Project were approved bythe International Advisory Committee (IAC) at itsmeeting in Vienna from 18 to 22 March 1991 andthey are based upon the radiological and healthassessments carried out by the Project. The technicaldetails of these assessments are to be found in theextensive Technical Report, to which referenceshould be made for further information.

The conclusions and recommendations are subjectto the constraints and limitations of the Projectdesign. These constraints and limitations should berecognized so that the conclusions and recommenda-tions are not interpreted to be more or less than iswarranted by the Project. Ideally, the Project teamswould have had sufficient time and resources toexamine exhaustively and verify independently all theinformation available to them as well as to carry outmore extensive independent analyses. Such compre-hensive efforts were not feasible nor were theyaltogether warranted. More limited objectives werenecessary and were adopted for a number of reasons:the time available to complete the Project waslimited; the data provided to the Project teams werenot always adequate; the evaluation of the radiologi-cal situation immediately after the accident could nolonger be independently assessed because of the timethat had elapsed and the consequent decay of shortlived radio-isotopes; the number of availableindependent experts as well as their time werelimited; the thousands of square kilometres that werecontaminated could not be thoroughly monitored orsystematically surveyed for 'hot spots' of contamina-tion; and the hundreds of thousands of people livingin these areas could not be individually examined.Finally, the Project survey was concerned principallywith human problems and relevant environmentalconsiderations such as agricultural contamination;

consequences of the accident for other species werenot specifically considered.

Efforts were therefore directed to the assessmentof data, techniques and methodologies employed toestimate contamination levels, doses2 and healtheffects, and to the evaluation of radiological protec-tion policies. Sufficient data were obtained indepen-dently to enable the Project teams to formulateindependent judgements.

In order to assist the authorities of the USSR, theBSSR, the RSFSR and the UkrSSR, major effortswere devoted to the urgent need to provide guidancewith respect to radiological protection measures(including the 'safe living concept') and theassociated radiological protection practices and poli-cies. The radiological considerations influencing apolicy such as relocation (for example, the radiationdoses and risks averted by relocating populations)had to be evaluated within the context of the resultingpsychological, social and economic factors.

An assessment was made of the health of personswho had been residing in settlements in the contami-nated areas of concern since the time of the accident.This was done by examining the population for poten-tial health effects due directly to radiation as well ashealth effects that may have occurred as a result offactors related to the accident but not due to radiationexposure. Since there were few baseline data forthese populations from the time before the accident,it was necessary to compare results for these peoplewith those for other people living in the region butoutside the contaminated areas of concern.

As the Project was directed at those currentlyliving in the contaminated areas, the radiological

2 The word 'dose', unless otherwise specified, isgenerally used to mean 'effective dose', i.e. the totalabsorbed dose appropriately weighted for the harmfulnessof the radiation type and the susceptibility to harm ofhuman tissues.

8


health effects to the more than 100 000 people evacu-ated from the prohibited zone around the Chernobylsite were considered only for those currently living inthe areas under review. Nor did the Project addresshealth effects for the large number of emergencypersonnel (the so-called 'liquidators') who werebrought into the region temporarily for accidentmanagement and recovery work. The health of thisoccupationally exposed population is reportedlybeing monitored at medical centres throughout theUSSR.

Some issues received comparatively little atten-tion, owing primarily to the unavailability of neces-sary and sufficient data. For example, it was notpossible to corroborate the early contamination ofland and the exposures of the public due to iodineisotopes. Nor were the early remedial protective

actions undertaken (e.g. thyroid blocking by iodineprophylaxis and evacuation) subject to thoroughevaluation.

Despite the limitations of time and financialand human resources, the International AdvisoryCommittee is of the opinion that the Projectrepresents a much needed international humanitarianand scientific response to the needs of the authoritiesand the people of the USSR who were affected by theChernobyl accident.

The International Advisory Committee acknow-ledges the many problems in a study of such breadth.Nonetheless, the work has involved leading andeminent international scientific investigators andmedical specialists who endorse its adequacy and itsresults. It is a significant step in the evaluation of theconsequences of the accident.

Chapter Two:Environmental Contamination

The Problem

The Chernobyl accident involved the largest shortterm release from a single source of radioactivematerials to the atmosphere ever recorded. Of thematerials released from the reactor core, four elementshave dominated the short term and long term radiologi-cal situation in the affected areas of the USSR: iodine(primarily I31I), caesium (l34Cs, l37Cs), strontium(primarily ^Sr) and plutonium (239Pu, 240Pu). In addi-tion, highly radioactive fuel fragments (hot particles)were released.

Aerial radiation measurements and environmentalsampling begun shortly after the accident showed thatthe highest level of environmental contamination was inthe area around the reactor that would eventuallybecome the prohibited zone. Elsewhere in the SovietUnion, changing wind conditions and sporadic rainfallover the ten-day release phase resulted in a very unevenpattern of radioactive fallout within areas of the BSSR,the RSFSR and the UkrSSR.

Heavy rainfall combined with local conditions tocreate pockets ('hot spots') of exceptionally high surfaceradioactivity levels resulting in external dose rates thatwere as much as five thousand times the dose rate dueto the natural background. Once releases had beenhalted, changes in contamination patterns resulted fromradioactive decay (primarily of I3II, which decaysalmost totally within three months) and normal weather-ing processes which caused the migration of contamina-tion into the soil and the dispersion of soil particlesthrough the runoff of surface waters.

Information from continuing aerial surveys andenvironmental sampling has been used to derive officialsurface contamination maps which display the ranges ofsurface concentration of caesium, strontium and pluto-

nium. Officially published in 1989, the maps havestirred controversy among scientists and residents.About 25 000 km2 and 2225 settlements in the threeRepublics are officially defined as having a l37Cssurface contamination in excess of 185 kBq/m2

(5 Ci/km2). For the residents there were crucialquestions:

• Did the official maps describe the actual surfacecontamination?

• Were the water resources contaminated?• Could locally produced milk and food be safely

consumed?

Objectives and Approach

It was clear from the outset that this internationalassessment could not expect to duplicate the four-yearefforts of local experts to assess the environmental con-tamination of such a vast land mass. Project expertssought to examine the official assessments through athree part approach.

Firstly, they reviewed official data and the practicesused for data collection and reporting. The official datawere presented in the form of surface contaminationmaps for 137Cs, ^Sr and 239Pu and tables for nearly500 settlements in the three Republics containing surfacecontamination values for l37Cs and ^Sr, along withcontamination values for environmental samples andfood. Local data from regional and Republic instituteswere considered.

Secondly, the Project teams visited twenty govern-mental institutes and laboratories to review their prac-tices and facilities for sampling and analysingenvironmental materials and food. Reportedly, these

10

Chapter Two: Environmental Contamination

Official maps. Maps showing isopleths of surface contamination for caesium, strontium andPlutonium worn made available to Urn Project and used for reference purposes, Officially publishedin 1989 by the USSR State Committee on Hydrometeorology and Environmental Monitoring, Moscow,the maps are reportedly derived from aerial radiation surveys and soli sampling in settlements inknown and suspected areas of contamination. These maps can be found in a separate cover.

particular institutes contribute substantially to the offi-cial assessment process. An intercomparison exerciseusing reference materials containing known quantities ofradioactive substances was carried out to evaluate theanalytical capabilities of those laboratories which wereproviding the bulk of the information in the threeRepublics.

Finally, the Project teams used independent methodsand equipment for surveying the radioactivity on theground, and in the soil, sediments, air, water, vegeta-tion, milk and food. Given the large number of settle-ments affected and the limited resources available to theProject, only grab sampling and spot measurementswere undertaken. Of the surveyed contaminated settle-ments, the majority are located in the areas withI37Cs surface contamination levels above 555 kBq/m2

(15 Ci/km2), while a few have lower contaminationsof between 37 kBq/m2 (1 Ci/km2) and 185 kBq/m2

(5 Ci/km2). In addition, measurements were made insix control settlements defined as areas with contamina-tion below 37 kBq/m2 (1 Ci/km2) to verify that theycould serve as control settlements for the Project medi-cal teams. The environmental and food samplescollected were analysed for radioactivity at laboratoriesin six countries.

Work in Detail

REVIEWING OFFICIAL DATA AND PRACTICES

A key element of the study was a review of the offi-cial methodology for deriving the surface contamination

maps. As formalized documentation was not readilyavailable, the team relied on direct discussions with localexperts.

The contamination maps are reportedly based on datafrom aerial gamma radiation monitoring surveys and theanalyses of soil samples collected at locations known orsuspected to be affected by radioactive fallout. Theaerial surveys which were started immediately after theaccident are presently carried out twice yearly. There isa central environmental database in Obninsk and data-bases in each of the Republics. While information isexchanged among the institutes at the regional andRepublic levels, the results of radiation measurementsobtained at the Ail-Union level are not normally trans-ferred to the Republic authorities.

The review of official practices and discussions withlocal experts indicated a well developed infrastructurefor assessing radioactivity in environmental materialsand food. Institutes with experienced staff range in sizefrom small laboratories with only regulatory controlfunctions to major research bodies. No detailed informa-tion was provided on the relative contribution of eachinstitute to the environmental assessment process or onquality assurance programmes for ensuring the qualityof the analyses and the reliability of the results.

Surface and, to a lesser extent, groundwaterresources are extensively sampled. Rivers and reser-voirs in the affected areas are sampled and a speciallyequipped research ship regularly monitors contamina-tion along the Dnepr River. The Project team notedproblems of caesium and strontium cross-contaminationin local laboratory preparations and analyses of water

11


and sediment samples which could cause an overestima-tion of the contamination.

The levels of contamination of milk and meat aremonitored. Milk is screened for caesium at dairies andcollective farms before processing. Animals selected forslaughter are checked and meat is checked at processingplants and at random at food shops before sale. Asinformation on the calibration of the measuring instru-ments was not available, the Project teams were unableto evaluate the accuracy of the official measurements.

INDEPENDENT PROJECT SURVEYS

Independent Project surveys were conducted inselected settlements over a six month period inmid-1990, using internationally accepted methods andequipment. These included external gamma dose ratemeasurements in indoor and outdoor locations as well assoil, water, air and food sampling. The results were usedto assess the official maps of surface contamination bycaesium, strontium and plutonium and to enhance under-standing of the environmental contamination in theaffected areas.

VALIDATING OFFICIAL RESULTS

An intercomparison exercise organized by the IAEALaboratory at Seibersdorf provided a yardstick for judg-ing the validity of official data. The 13 institutes thattook part are reported to be the most heavily engaged insampling and laboratory analyses of environmentalmaterials and foods. The institutes analysed 'blind'samples of (radionuclides measured): soil (^Sr, 239Pu,l37Cs, 226Ra); milk powder (^Sr, 134Cs, l37Cs, '"K);simulated air filters (^Sr, l37Cs, ""Co, 133Ba, 2l°Pb);and vegetation (""Sr, l34Cs, 137Cs, *°K) and reportedthe results together with the associated numerical uncer-tainties. The IAEA Laboratory compared their resultswith the recommended (i.e. 'reference') values.

The reported results for l37Cs in soil agreed wellwith the recommended values. On the other hand,results for strontium and plutonium in soil showed a ten-dency for overestimation (by as much as a factor offour). A similar tendency for overestimation was notedfor strontium in milk (by as much as a factor of nine) andfor caesium in milk (by as much as a factor of three).While results for strontium in vegetation appear gener-ally reliable, there was an observed slight tendency tounderestimate caesium. In simulated air filters theresults for caesium were in agreement with recom-mended values while the results for strontium deviatedby 30-50 per cent.

Dose Rate Measurements

Project dose rate surveys in Bragin, Novozybkov,Polesskoe and Daleta were used to examine the officialassessments of the range of average values of l37Cssurface contamination in these settlements. Over2000 measurements were made of the gamma dose rate,which were converted and compared with the officialsurface l37Cs contamination values.

Sampling Programme

Soil

Project soil core samples in Novozybkov, Bragin,Polesskoe and Daleta were also used to determine theradionuclide concentrations at different depths and toexamine the official assessments of the range of averagevalues of l37Cs surface contamination in these settle-ments. A limited number of selected soil samples fromBragin, Daleta and Polesskoe were independently ana-lysed for plutonium (239Pu and 240Pu) and strontium(^Sr) surface activity in the topsoil.

Water Resources

Water samples were taken in 16 settlements in theBragin, Novozybkov and Ovruch regions to determine

12


(a) (b)

| | 0-0.4

| | 0.4-1.0 Dose rate (

| | 37-370 (1-10)

| | 370-810(10-30)

| | >810 (>30)

137Cs surface contamination(kBq/m2 (Ci/km2))

Correlation of Project measurements of dose rate with official values of caesium surface contamination forthe settlement of Bragin, BSSR. Project surveys using independent methods and equipment provided generalcorroboration of the levels of surface contamination due to caesium given in official maps. As illustrated herefor the settlement of Bragin, Project measurements of gamma dose rates in air (a) correlated with the caesiumcontamination values for that settlement as officially reported by the Byelorussian Department of the All-UnionInstitute for Agricultural Radiology, Gomel, BSSR (b). Both data sets indicated a variable pattern of surfacecontamination, with the highest activity concentration recorded in undisturbed locations and the lowest on hardsurfaces that presumably have weathered or have been decontaminated.

whether deposited radionuclides had contaminateddrinking water. The sites included hand dug wells,public water supplies, ponds, lakes and rivers. In addi-tion, sediment samples were taken from lakes, ponds,rivers and reservoirs to assess caesium penetration andto determine the hazards for aquatic systems. The water

samples had caesium concentrations usually below thelimit detectable by the instruments used. However, sedi-ment samples from areas with relatively high groundcontamination show elevated levels in the top layers,representing a potential source of future contaminationof biota in these areas.

13


_sUL i37cs surface contamination (kBq/m2)

1114

]885

Project measurements of caesium soil contamination in Novozybkov, RSFSR. Project efforts to confirm theofficial values for caesium surface contamination included surveying the radioactivity in the topsail in selectedsettlements. As illustrated here for the settlement ofNovozybkov, independent sampling oftopsoil contaminationindicated caesium values ranging from 470 to 1114 kBq/m2 (12. 7 to 30.1 Ci/km2). These data are in reasonableagreement with the range of average values of 555 to 1480 kBq/m2 (15 to 40 Ci/km2) officially reported for thatsettlement by the USSR State Committee on Hydrometeorology and Environmental Monitoring, Moscow.

14


RSFSR

52 [ 3398

600| 1763

15

2915

BSSR1999

10 100 1000137Cs surface contamination (kBq/m2)

10000

] Project estimates Official estimates

Comparison of Project measurements of caesiumsoil contamination with official values of caesiumsurface contamination for settlements of the BSSRand the RSFSR. Limited Project sampling ofcaesium contamination in topsails in five settlementsof the BSSR and four settlements of the RSFSRindicated values that were consistent with the rangeof the official values based on comprehensive surveyscarried out since the accident and reported for thesesettlements by the USSR State Committee onHydrometeorology and Environmental Monitoring,Moscow.

Strontium

5400 [ |38600

37000 ••174000

36Plutonium

740

<3700

200 600 1000 2000 6000 10000 20000 60000 100000Surface contamination (Bq/m2)

[ | Project estimates | | Official estimates

Comparison of Project measurements of strontiumand plutonium soil contamination with officialvalues for surface contamination in the Braginregion, BSSR. The Project concluded that analyticalresults for a limited set of soil samples correspondedto the reported estimates for plutonium but werelower than those for strontium. As illustrated here forsettlements in the Bragin region, the measurements ofstrontium contamination suggest the potential foroverestimation in the official values reported by theUSSR State Committee on Hydrometeorology andEnvironmental Monitoring, Moscow.

Air Food and Milk

Wind, ploughing and other activities cancause deposited fallout to be resuspended into theair, where the radioactive dust could be inhaled.Air samples were taken in 12 settlements to deter-mine the concentration of resuspended particles.Sampling sites were mainly outdoor locations,such as playgrounds and agricultural areas. Althoughthe measurements indicate low gamma and alphaoutdoor air concentrations, heavy rainfall duringthe period of the investigations and the seasonalcoverage of soils with vegetation could havelimited the resuspension and contributed to the lowreadings.

Food samples representative of the total diet for asingle day were collected from residents of settlements inthe Bragin, Novozybkov and Ovruch regions. The radio-active contamination of food collected from the commer-cial sector in the surveyed settlements was generallyfound to be below guidance values for internationaltrade. However, in a few samples the levels were con-siderably higher than these values; this may have been aresult of lack of compliance with official recommenda-tions regarding the consumption of locally produced orcollected food. Results for B7Cs levels in milk samplesfrom settlements in the Bragin, Novozybkov and Ovruchregions showed a similar pattern.

15


Bragm __.region 5 81BSSR L-1

region' 3\

Ovnichregion isl

Codex guidance level

\

1 630

,

1 800

J I I I I I0 500 1000

'"Cs activity concentration (Bq/kg wet wt.)

General Conclusions

Measurements and assessments carried out underthe Project provided general corroboration of thelevels of surface contamination for caesium asreported in the official maps that were made availableto the Project. Analytical results from a limited set ofsoil samples obtained by the Project teamscorresponded to the surface contamination estimatesfor plutonium but were lower than those forstrontium.

The concentrations of radionuclides measured indrinking water and, in most cases, in food from theareas investigated were significantly below guidelinelevels for radionuclide contamination of food movingin international trade and in many cases were belowthe limit of detection.

Project measurements of caesium concentration intotal diet samples from settlements in the Braginregion, BSSR, the Novozybkov region, RSFSR andthe Ovruch region, UkrSSR. Project analyses of alimited number of total diet samples (e.g. bread,potatoes, vegetables) collected from residents ofeleven settlements indicated a relatively large varia-tion in the measured levels of caesium contamination.As illustrated here, the measured values for all elevensettlements in the three regions were below thoserecommended by the responsible authorities and alsobelow the guidance level for radionuclide contamina-tion with 137Cs (1000 Bq/kg) established by theCodex Alimentarius Commission (1989) for foodmoving in international trade. For two settlements inthe Ovruch region, which officially have a low levelof caesium surface contamination, a few samples oflocally produced food showed elevated contaminationlevels. This suggests a high transfer factor betweensoil contamination and food contamination in thoseareas surrounding the settlements.

Detailed Conclusions

CAPABILITIES OF SOVIET LABORATORIES

The analytical capabilities of Soviet laboratoriesappeared to be adequate. There is an extensive infra-structure for the analysis of environmental and foodsamples. The range of performance of the Sovietlaboratories that participated in the intercomparisonexercise was broad, but similar to that found inprevious international comparison exercises. The fewproblems identified, including the tendency to over-estimate strontium, did not significantly affect theuse of data for conservative dose assessmentpurposes.

The field studies which were assessed, eventhough they excluded 'hot spots', appeared to giveadequate results for the average values characterizingsurface deposition in a region. In accordance with themethodology that reportedly had been used, 'hotspots' that had been identified were systematically

16


excluded in the reported estimation of average sur-face deposition for a given region and were not listedin the detailed data provided to the Project teams.

The extensive surface water sampling programmesare adequate. Certain problems during samplingand/or analytical procedures could lead to possibleoverestimation of the concentrations of radionuclidesin water.

Insufficient information was available to evaluateair sampling equipment and procedures. Although therelative contributions from airborne resuspension ofradioactive materials to dose are believed to beminor, it should be noted that the occurrence of air-borne resuspension, particularly during agriculturalactivities or dry periods, cannot be excluded.

Rapid screening and sophisticated techniques usedlocally for monitoring commercially available foodfrom production to consumption appeared to be satis-factory. The relevant instrument calibration tech-niques could not be evaluated sufficiently by theProject owing to the lack of detailed technicalinformation.

INDEPENDENT PROJECT SURVEYS

A variety of surveillance methods were used in thesurveyed contaminated settlements and the surveyedcontrol settlements to estimate surface contamination.The ranges of average values of surface contamina-tion due to the deposition of caesium on the groundgiven in the official maps made available to theProject were corroborated. On the basis of the limitednumber of soil samples independently analysed forplutonium and strontium, the results for plutoniumwere found to correspond to the reported estimates,whereas a potential for overestimation in the reporteddata for strontium was identified.

The radioactive contamination of drinking waterresources that were sampled in the surveyed con-taminated settlements was found by the Project teamto be significantly lower than the intervention levelsestablished by the authorities.

The radioactive contamination of food sampleswas found to be in most cases below the interventionlevels established by the responsible authorities in thesettlements surveyed. In some settlements, milk fromindividual farms and food collected in natural areas incontravention of official recommendations could becontaminated above these levels.

Recommendations

Local laboratories should, as is customary, beconfidentially notified of the Project findings ofrelevance for them and should take appropriateremedial actions where needed. Local laboratorieswhich have participated in the intercomparisonexercise should be informed confidentially of theirperformance so that they can rectify problems wherenecessary.

Quality assurance programmes to assure con-sistently reliable results should be in place in locallaboratories. These laboratories should participateregularly in international intercomparison pro-grammes and international intercalibration exercises.

A programme should be established to assess thesignificance of 'hot spots'. Research programmes onthe characteristics of hot particles and their occur-rence in the environment are warranted and should becontinued.

Water sampling and analytical techniques shouldbe improved to comply with established procedures.The potential for long term contamination of waterbodies, possibly leading to contamination of theaquatic food chain, should be investigated. Researchshould be planned to study radionuclide behaviour in

17


ecosystems, and desorption of strontium from sedi-ments in surface water bodies and its impact onagriculture through irrigation practices.

It may be advantageous to consider the future usein the USSR of validated models to predict radionu-clide levels in food. The use of these models could becost effective in the long term and reduce the need forextensive sample analysis.

All data from the BSSR, the RSFSR and theUkrSSR related to radiological contamination shouldbe shared with the USSR Central Data Bank inObninsk so as to be made available to all Republics.

All such information should also be made available torelevant institutes and institutions.

A programme should be implemented to derivemore detailed official large scale contaminationmaps.

A collaborative programme of air sampling andanalysis should be established between the locallaboratories and die network of international labora-tories set up by the IAEA Laboratory at Seibersdorfin order to obtain more definitive information on therelevance of die resuspension and inhalationpathways.

18

Chapter Three:Radiation Exposure of the Population

The Problem

Many people living in the areas affected by theChernobyl accident remain anxious about the radiationexposure situation. Information on radiation risk is notwell understood by the public and there is little grasp ofthe magnitude of the additional risk imposed by the post-Chernobyl contamination.

In the first few weeks after the accident, the signifi-cant radiation exposure to the population was due to the1311 radionuclide. This could have been inhaled from theplume, though that represented only a minor pathway forpopulation exposure. More important were the drinkingof milk from cows grazing on contaminated pastures andthe consumption of contaminated leafy vegetables.

Increasingly, as time passed, the largest proportion ofthe exposure arose from the l37Cs radionuclide as aresult of both exposure to external irradiation from sur-face contamination and internal exposure resulting fromthe consumption of contaminated food. It is difficult tobe precise about how much radiation dose has alreadybeen received or will be received. Variations in soil con-ditions and in eating habits obviously render precisionimpossible and make the evaluation of past and futureexposure difficult.

Key questions are:

• How accurate were the official estimates ofradiation exposure?

• What were the radiation exposures to the popula-tion in the early days after the accident?

• What are the current and future radiationexposures to those remaining in the affected areas?


As with the environmental contamination evaluation,Project experts did not duplicate the past efforts, butsought to assess the official exposures through a threepart approach.

Firstly, there was a review of official information onradiation doses to people living in seven settlementsselected for study. Each of these settlements has a l37Csground contamination greater than 555 kBq/m2

(15 Ci/km2) and in each instance non-contaminatedfood is provided commercially and there is a ban on theconsumption of locally produced food. The Projectteams visited over twenty institutes and governmentministries in the BSSR, the RSFSR and the UkrSSR,where they examined and discussed dose calculationmethodology. Attempts were made to reconstruct thedose estimates using the official information providedand direct discussions with local experts. However, thiswork was hampered by gaps in information, particularlyin regard to the methods used to estimate I3II thyroiddoses and past levels of caesium contamination infood.

Secondly, the Project teams assessed the radiationexposure of the selected populations using interna-tionally recognized methods and their own indepen-dently compiled database obtained through extensivefieldwork in mid-1990. They measured external radia-tion exposures for some 8000 residents and performedwhole body monitoring of 9000 individuals for internalcontamination. The whole body measurements werevalidated in French and Austrian laboratories and in theIAEA Laboratory at Seibersdorf.

19

Chapter Three: Radiation Exposure of the Population

500

400

•? 300

1o>«Q 200

100

BraginV

Korma NovozybkovC

Zlynka

BSSRY

RSFSR

NarodichiV

YUkrSSR

Polesskoe;

Official estimates Project estimates

Comparison of Project reconstructed estimates with official estimates for radiation doses to the population inselected settlements. From the Project review of official dose estimation methods, it was concluded that the offi-cial procedures for estimating doses were scientifically sound and that the methodologies used were intended tooverestimate the doses. As illustrated here for seven surveyed settlements in the BSSR, the RSFSR and theUkrSSR, the Project reconstructed estimates for internal and external doses due to caesium and strontium werelower by a factor of 2-3 than the values officially reported by the Institute of Biophysics, Moscow.

Finally, the independent Project estimates werecompared with the official dose values. While there areshortcomings in extrapolating exposures from theProject's relatively small population samples, the infor-mation is adequate for a valid assessment of the overallpopulation radiation exposure. Although some of theofficial reports lack clarity with respect to mathematicalformulation and the selected values of parameters, thebasic scientific assumptions in the dose calculationswere found to be sound.

Work in DetailREVIEW OF OFFICIAL DATAAND METHODOLOGY

Although Project experts obtained reasonableamounts of information from official data on environ-mental contamination and the radiation exposure of thepopulation, the information was not sufficient to allowthem to make calculations of individual radiation dosesto residents. During the international review it was not

20


3.2

0.8

O 0.7q103 0.6

ID

f 0.5

0.4

0.3

0.2

0.1

n n n nBragin Korma Veprin Novozybkov Zlynka Polesskoe

BSSR RSFSR UkrSSR

| | Children | | Adults

Official estimates of absorbed dose to the thyroidfrom radioiodine exposures. Since the short livedradioiodines had completely decayed by the time ofthe international assessment, Project teams wereunable to independently verify the doses officiallyreported by the Institute of Biophysics, Moscow. Thereported doses were based both on thyroid measure-ments made during the early stage after the accidentand on assumptions concerning the intake of food andmilk contaminated by radioiodine. Local scientistsare re-evaluating the results of their measurementsmade during this early stage. As illustrated here, theabsorbed thyroid doses reported in 1989 for six settle-ments in the BSSR, the RSFSR and the UkrSSR indi-cated mean doses for children (from birth to sevenyears) that vary from less than 0.2 Gy to 3.2 Gy.Absorbed dose is defined as the energy absorbed perunit mass of tissue.

possible to obtain a clear demonstration of how the offi-cial methodology was applied. Project experts consid-ered it useful to attempt to reconstruct the official doseestimates using the official methodology. The externaldoses projected for 1990-2056 could be consistentlyderived for all seven settlements using the officialmethodology. There were differences from reportedinternal doses, however, when estimates were madeaccording to the official methodology, sometimes by afactor of three. This was due to uncertainties in inputdata for concentrations of caesium in milk. The lack ofbasic input data for 131I made reconstruction of thyroiddose estimates impossible.

INDEPENDENT PROJECT DOSE ASSESSMENT

The Project's independent dose assessment employedinternationally recognized methods along with anindependently compiled database (principally fromUSSR sources) for each of the seven settlements.

The methods used were primarily those developed byUNSCEAR, as these are easy to apply, well documentedand familiar to research workers worldwide. The doseevaluations were made in such a way that they could becompared with the official values reported for twoperiods: 1986-1989 and 1990-2056. Direct measure-ments were made of external and internal doses ofpeople living in surveyed settlements. As in the officialassessment, it was conservatively assumed that therewould be no future restrictions on the consumption oflocally produced food.

A total of 8000 personal radiation dosimeters (filmbadges) were distributed during mid-1990 to residents ofthe surveyed contaminated settlements. The results,which were independently read in a French laboratory,were given directly to the population in February 1991.While the intent was to cover all age groups in the popu-lation, most of the children were on holiday outside ofthese areas during the summer campaigns. The parti-cipants were instructed to carry the dosimeters in apocket of their clothing on the upper half of the body and

21


100

80

O. 60oo.

2£ 40

a.

20

| | < 0.2 (limit of detection)

I I 0.2-0.99

1.0-4.5

>4.5

RSFSR

Dose (mSv)

UkrSSR

Project measurements of external dose to the population in selected settlements. For independent measurementof external dose, 8000 film badge dosimeters were distributed to inhabitants of seven settlements in the BSSR,the RSFSR and the UkrSSR. As illustrated here, 90 per cent of the results were below the detection limit(of 0.2 mSv)for a two-month exposure period. The French Service central de protection contre les rayonnementsionisants (SCPRI) provided the dosimeters and measured their recorded doses.

to place the instrument at the bedside during the night.Ninety per cent of the results were below the limit ofdetection. Higher measurements were recorded mainlyfor people living in the highly surface contaminatedareas or working for long periods in open fields orforests. In the rare cases of unusually high values,it is suspected that the dosimeters may have beenimproperly used.

About 9000 people were monitored for internalirradiation in mid-1990. A mobile laboratory equippedwith four whole body counters measured caesiumlevels in residents of the seven surveyed contaminatedsettlements. The results of these whole body measure-ments indicate little relationship between the amount ofl37Cs ground contamination and the amount of caesiumin the body.

22


100

80

60

40

20

CO

- 10.6p

90

8.0

7.0

60

5.0

4.0

3.0

2.0

1.0

W

Bragin Korma Veprin

BSSR

Whole bodyJ measurement

estimates

Novozybkov Zlynka Polesskoe

RSFSR UkrSSR

^^ Environmental| transfer model

estimates

Comparison of Project estimates of internal dosesbased on whole body measurements with resultsbased on environmental transfer models. A majorProject field effort was the direct measurement ofcaesium in the body of local residents. More than9000 inhabitants of settlements in the BSSR, theRSFSR and the UkrSSR were monitored usingportable whole body counters provided by SCPRl. Asillustrated here, the Project dose estimates are eightto thirty times lower than those derived by means ofenvironmental transfer models. The differencesreflect the impact of restrictions imposed on the con-sumption of food produced in the contaminated settle-ments. The environmental transfer model assumes norestrictions on local food consumption (and wouldtherefore predict a higher caesium body content).

16

15

o- /CD— 7 -

Daleta

Vo>

5

Rakitnoe

Ovruch

Novozybkov^

Kormal

Polesskoe

I

Zlynka

JBragin

Veprin^

0 200 400 600 800 1000 1200

Average 137Cs surface contamination (kBq/m2)

Relationship between Project measurements ofcaesium incorporated in the body of selected popula-tions and official values for caesium surface con-tamination. Project results from whole bodycounting indicated that there is not a direct relation-ship benveen the amount of caesium incorporated inthe body of people living in the surveyed areas andthe official values for surface contamination in thoseareas. As illustrated here, high levels of body con-tamination were found for residents of the settlementsof Ovruch, Rakitnoe and Daleta in the UkrSSR,where the surface contamination is lower than in theother settlements surveyed. These high levels areprobably due to the high transfer factor between soilcontamination and food contamination in this area ofthe UkrSSR, and could indicate non-compliance withofficial recommendations regarding the consumptionof locally produced food and milk.

23


Externalirradiation

80 1160

60 130

Internalirradiation(caesium)

60 1230

Total(includingstrontium)

400

Official estimates

100 200 300Dose (mSv)

| | Project estimates

400

Comparison of Project estimates and officiallyreported estimates for radiation dose to the popula-tion in selected settlements. Project dose estimatesderived independently were compared with the offi-cial values for the population in the selected settle-ments as reported by the Institute of Biophysics,Moscow. As illustrated here, the Project estimateswere lower than the officially reported dose esti-mates. Overall, there is general agreement within afactor of 2-3 (see footnote 5).

COMPARISON OF DOSE ESTIMATES

The final step was the comparison of the dose esti-mates derived independently by experts and the offi-cially reported values for the population in the surveyedcontaminated settlements. In all cases the independentestimates were lower than the officially reported dosevalues, but overall there is general agreement to withina factor of 2-3.

General Conclusions

The official procedures for estimating doses werescientifically sound. The methodologies that wereused were intended to provide results that would notunderestimate the doses. Independent measurementsin individual residents monitored for external and forinternal exposure from caesium incorporated into thebody yielded results that would be predicted on thebasis of calculational models. Independent Projectestimates for the surveyed contaminated settlementswere lower than the officially reported doseestimates3.


EXTERNAL EXPOSURE

The external exposure due to deposited radio-nuclides is, in most areas, the most significant contri-butor to dose, especially in those areas where foodrestrictions have been applied. The reported metho-dology for calculations of external dose is beingconfirmed by local measurements using thermo-luminescence dosimetry.

Independent measurements of external exposurewere carried out under the auspices of the IAEA forthe Project. Eight thousand film badge dosimeterswere distributed to residents of seven settlements.Ninety per cent of the results were below the detec-tion limit of 0.2 mSv for a two month exposureperiod. This result is in agreement with what wouldbe expected on the basis of calculational models.

These estimates were derived on the basis of dosesdue to l37Cs and *°Sr; where appropriate, shorter livedisotopes of caesium and strontium were also taken intoaccount.

24


INTERNAL EXPOSURE

Doses from incorporation of caesium in the firstfour years after the accident were estimated by theauthorities on the basis of measurements of incor-porated caesium, including both 134Cs and 137Cs.The procedure for estimating doses from thesemeasurements is in accordance with that used in theindependent evaluations made under the Project.

Official estimates of projected doses due tothe intake of caesium are based on a number ofinfluencing factors, including an assumed half-timeof 14 years for 137Cs in the environment. Thisassumption is designed to ensure that doses are notunderestimated and is prudent.

Official estimates of doses due to the intake ofstrontium in the first four years after the accidentwere based on a metabolic model and measurementsof strontium in foods, or on an assumed ratio ofstrontium to caesium in foods if no data on strontiumwere available.

Official estimates of projected doses due to theintake of ^Sr in the diet were made on the assump-tion of an environmental half-time of 10 years; thisassumption was not referenced, but is stated to bederived from experience gained after the accident ata nuclear materials production plant in Kyshtym inthe USSR in 1957.

On the basis of the results of an intercomparisdnprogramme with the participation of local labora-tories and the IAEA Laboratory using standardizedphantoms, it can be concluded that the accuracyobtained in local whole body measurements forcaesium is adequate for radiological protectionpurposes.

Whole body counting of caesium was carried outunder the auspices of the IAEA for the Project andcovered more than 9000 people in nine settlements.The results indicated generally lower body contentsof caesium than would be predicted on the basis of

most models of environmental transfer, dietary intakeand metabolism. Similar results for whole bodycounting of caesium have been reported in othercountries.

Absorbed thyroid doses due to iodine were offi-cially reported on the basis of thyroid measurementsmade in the early stages after the accident andassumptions concerning intake. Mean absorbedthyroid doses for children from birth to seven yearsold were officially reported to vary from less than0.2 Gy to 3.2 Gy for seven surveyed contaminatedsettlements.4 However, since the iodine had com-pletely decayed by the time of the Project, noindependent verification of the reported absorbedthyroid doses was possible.

DOSE ESTIMATE COMPARISON

Independent estimates of doses were made for thesurveyed contaminated settlements on the basis ofaverage deposition results. It could not be assumedthat such generalized dose estimation assumptions orenvironmental modelling calculations wouldaccurately reflect the local soil conditions, agricul-tural practices and living habits in the surveyed con-taminated settlements but the results could beexpected to provide a general basis for comparisons.

The ranges in the estimates of 70 year(1986-2056) doses were as follows:

Independent estimates for the surveyedcontaminated settlements:

External doseInternal dose (caesium)

60-130 mSv20- 30 mSv

Total (including strontium): 80-160 mSv

4 The maximum reconstructed absorbed thyroid dose(in Bragin) was officially reported as 30-40 Gy.

25


Officially reported estimates for the samesettlements:

External doseInternal dose (caesium)

80-160 mSv60-230 mSv

Total (including strontium): 150-400 mSv

Independent Project estimates for the surveyedcontaminated settlements were lower than the offi-cially reported dose estimates. Overall, there isagreement to within a factor of 2-3 between theindependent estimates and the officially reportedestimates.5

Recommendations

The official procedures for dose assessmentreported to the Project use deterministic models that

5 These conclusions were drawn on the basis of esti-mated or reported doses from external exposure due to allrelevant radionuclides and internal exposures due to l34Cs,l37Cs and ""Sr. Doses to the thyroid from I3II and othershort lived isotopes of iodine and their precursors have alsobeen considered.

are designed not to underestimate doses. Probabilisticdose assessment methods should be developed so thatmore realistic estimates of dose are eventually avail-able and uncertainties in the calculation are fullyassessed.

Over the next few decades it should be possible toextend scientific knowledge of environmental trans-fer factors by studies in the contaminated areas ofconcern. Measurement of external exposure rate,caesium body burden and the caesium and strontiumcontent of foodstuffs should be continued.

Although the potential relative contributions fromresuspension to dose are believed to be minor, evenfor outdoor workers, doses should be assessed forcritical groups such as agricultural workers.

Local scientists should participate more actively ininternational dose assessment validation studies. Suchactivities include intercomparisons of environmentaltransfer models and internal and external dosimetryintercomparisons.

Local scientists should participate more actively ininternational programmes on both the formal level(for example, through attendance at seminars,symposia and conferences) and the informal level toprovide an exchange of information on technologythat can be applied to the effective solution of dosi-metric problems. Support should be given forspecialists to gain experience working in foreignlaboratories.

26

Chapter Four:Health Impact

The Problem

The suspected health impact of the Chernobyl acci-dent has unquestionably been of overriding concernamong the population. There had been continuingreports of a higher incidence of illness among thoseresiding in the affected areas. No doubt, the heightenedsensitivity to health issues led to an increased registra-tion of complaints and a greater number of diagnoses ofboth serious and non-serious illnesses.

Public and professional uncertainty and concerncentred on the following questions:

• What health problems were related to theChernobyl accident?

• What health effects were due directly to radiationexposure?

• What health effects may be expected in the future?


In an attempt to assess the reported increases in ill-ness attributed to the Chernobyl accident and to dealwith the concerns, a two step approach was used in theProject. The first step was to review official data at keymedical centres and institutes. The next step was toexamine people in both surveyed contaminated and sur-veyed control settlements and to compare the results.Because medical data before 1986 are sparse, the healthof inhabitants from the surveyed contaminated settle-ments had to be compared with that of a similar popula-tion living in surveyed control settlements wherecontamination levels are lower but socioeconomic condi-tions are similar. The examination results were reviewedby Project teams of doctors and epidemiologists, who

employed a limited version of a commonly usedepidemiological approach to determine the health risk.Additionally, a nutrition expert reviewed data inMoscow and the three Republics, and a field teamvisited 13 settlements to conduct total diet studies.

Any health effects study initiated four years after theaccident was bound to have weaknesses and limitationsand this one was no exception. To begin with, the studywas limited to the population continuing to be exposedto radiation from the accident, namely those who remainin the surveyed contaminated areas. It would not havebeen possible to search out and conduct medicalexaminations on those who had left.

The study concentrated on small to moderate sizerural villages and towns since these were located in areasof higher contamination than the larger cities. The typeof settlements and the population groups studied cannotbe taken as entirely representative of the situation in thelarger cities of the affected areas. Nutritional differencesdue to variations in food availability and consumptionwould undoubtedly contribute to differences in healthstatus.

There were serious limitations in the data officiallyprovided. Internal correlation of the diverse data as wellas correlation with the Project data were extremelydifficult because of deficiencies in the equipment andmethodology that had been used.

Work in Detail

SELECTION OF SURVEYED CONTAMINATEDAND SURVEYED CONTROL SETTLEMENTS

The selection of the settlements was made by themedical task force. The settlements were chosen to

27

Chapter Four: Health Impactf

popu

latio

rca

l at

tent

io*

ro

ro

cH

0

Ul

C

<D 0)

Per

cent

ane

edin

g

o

on

c

-

"nn Fir-2 5

nn3 nn 1

—

10 40 60Age in 1990

| | Surveyed control | | Surveyed contaminated

Project assessment of the general health of thepopulation in selected settlements. The Projectassessment of reported increases in illness attributedto the Chernobyl accident included an investigation ofthe general health of the population in selected settle-ments. Independent medical examinations of inhabi-tants of both surveyed contaminated and surveyedcontrol settlements revealed no health disorders thatcould be attributed directly to radiation exposure, butdid indicate significant non-radiation-related healthdisorders among the adult population. As illustratedhere, Project results indicated that 10-15 per cent ofthe adult population examined in both surveyed con-taminated and surveyed control settlements should bereferred to a physician for follow-up medical care.

be representative of the various communities in thestudy region (ranging in population from 3000 to15 000). The surveyed control settlements had socio-economic structures similar to the seven surveyedcontaminated settlements.

Since the field teams could examine only a small por-tion of the population it was necessary to choose arepresentative group. A statistical sampling scheme wasdesigned to take into account the anticipated clinicalhealth problems.

In smaller villages patients were selected by year ofbirth, in larger villages by month and year of birth. Theaim was to examine various age groups of 20 peopleeach, which, depending on the size of the settlement,represented between 10 per cent and 80 per cent of thepopulation. Approximately 250 people were examinedin each settlement. In all, 1356 people were examined.

Cadmium

Sudan USA

Country

1 Mercury

Surveyedsettlements

Lead

Dietary intake of toxic elements of inhabitants ofsurveyed settlements compared with that of popula-tions of other countries. Project analytical resultsfor food, tissue and environmental samples lent nosupport to public concerns about the possibleenvironmental dispersion of toxic elements used at theChernobyl plant site shortly after the accident. Asillustrated here, the dietary intake of cadmium,mercury and lead by people surveyed by Projectteams was low compared with that recorded forpeople in Italy, Sudan and the United States ofAmerica. All values are expressed as percentages ofthe relevant provisional tolerable intake defined byWHO and FAO. The data are calculated for 80 kgbody weight.

28

Chapter Four: Health Impact

Oo

^E

2 5 10 40 60Age in 1990

] Surveyed control ] Surveyed contaminated

Project results for absolute lymphocyte count in resi-dents of selected settlements. Project haematologi-cal investigations of residents of selected settlementsfound some young children with low haemoglobinlevels and low red cell count. However, there were nostatistically significant differences between values forany age group of those examined in surveyed con-taminated and surveyed control settlements. Nodifference was found between the settlement popula-tions when leucocytes and platelets were examined.As illustrated here, independent field counting of theabsolute lymphocyte level in people of all ages doesnot reveal any marked difference in levels betweensurveyed contaminated and surveyed control villages.Nor are there any significant variations from data ofother countries. (The normal range varies with age.)The immune systems of those examined (as judged

from the lymphocyte level and the prevalence of otherdiseases) do not appear to have been significantlyaffected by the accident.

-4.96-

4 -

E5

CO

-0.60-

> Normal range

10

] Surveyed control

Age in 1990

| | Surveyed contaminated

Project results for thyroid stimulating hormone ofchildren in selected settlements. Owing to thesusceptibility of the thyroid gland to radioiodineexposure, the international assessment gave particu-lar investigative attention to possible thyroid dis-orders in individuals. Project results for thyroid sizesand size distribution and thyroid nodules in thoseexamined are similar to those reported for popula-tions in other countries. No statistically significantdifferences were found in those examined for thyroidstimulating hormone (TSH) or for the thyroid hor-mone (free T4). As illustrated here, independent ana-lyses using radioimmunoassay methods found noabnormalities in the thyroid function of children2-10 years old, nor was there any statistically signifi-cant difference observed between the thyroid func-tioning of children examined from the surveyedcontaminated and surveyed control settlements.

29


80

Age hi 1990 Age In 1990

.._.._.. USSR

I. USA

___ Surveyed control

_._•... Surveyed contaminated

Comparison of Project results for height and weight of children in selected settlements with published norms.A comparison of the results of Project examination of the growth patterns of children in both the surveyedcontaminated and surveyed control settlements with published norms indicated that the children are generallyhealthy and their diet is adequate. As illustrated here, independent medical examinations of nearly 800 childrenaged 2-10 years indicated no significant differences in (a) the height and (b) the weight of those living in thesurveyed contaminated and surveyed control settlements. Growth rates for both groups are well within publishednorms for populations of the USSR and the United States of America. Data for the 5th and 95th percentiles ofthe USSR population were reported by A.F. Zyb, et al., "The measurement of thyroid gland size in healthychildren and teenagers by ultrasound methods", Paediatrics, May 1990 (in Russian). Data for the 5th and 95thpercentiles of the USA population were reported by P. K Hamill, et al., "Physical growth: national center forhealth statistics percentiles ", American Journal of Clinical Nutrition, March 1979, Vol. 32, No. 3, pp. 607-629.

REVIEW OF OFFICIAL DATA

The first step in the assessment of the general healthsituation in the surveyed contaminated areas was toreview and locate the available medical data dealing withthe population of interest to this study. Two Projectdoctors met with 73 different scientists during23 separate meetings in Moscow, Kiev and Minsk.During these meetings, in addition to collecting the

information that would provide the basis for the reviewof the USSR data, the doctors discussed the goals and theoutline of the Project. This laid the groundwork neces-sary for the visits of three international teams of expertsto conduct independent medical examinations in thethree Republics affected by the Chernobyl accident.These data were reviewed at a later date by seven

doctors and epidemiologists that visited the relevantinstitutions in Moscow, Kiev, Minsk and Obninsk.

Concurrently, a review of the available nutritionaldata and a limited independent assessment of the nutri-tional status of the population were conducted. A nutri-tion expert visited institutions in Moscow, Kiev, Gomeland Minsk to review the data and a team visited13 settlements in the three Republics to conduct a totaldiet study.

INDEPENDENT MEDICAL EXAMINATIONS

The largest part of this assessment was carried outthrough missions by three medical field teams, each ofwhich spent two weeks conducting medical examina-tions of the population. These examinations were made

30


for evaluation purposes only. Any persons found to bein need of further examination or treatment werereferred to local health authorities. In many cases theresults of the Project examinations were entered into thelocal clinical medical records. The populations sampledwere statistically selected and rigorous quality controlon the data collected was implemented.

These missions were designed to address the medicalconcerns of the population and the perceived healtheffects as outlined by local scientists and physicians, aswell as to look for radiation effects that had beendocumented in other studies unrelated to Chernobyl.Each team included specialists in radiation effects,pediatrics, haematology, thyroid diseases, ultrasoundexamination and internal medicine, as well as represen-tatives from WHO. On one trip there was also an expert

in psychological and psychiatric disorders. The areasstudied were divided roughly into:

— Past medical history— General psychological state— General health condition— Cardiovascular status— Growth parameters— Nutrition— Thyroid structure and function— Haematology and immune system

deficiencies— Neoplasms— Cataracts— Biological dosimetry— Foetal and genetic anomalies.

30

X

10.0

9.0

=• 8.0

1,0

I 6.0

S 5.0£E 4.05 3.0

2.0

1.0

0

Upper level of normal range

Surveyed control Surveyed contaminated

Khodichi Surazh ChemerKirovsk I UnechaI Kirov

BSSR RSFSR

I Trokovichil—r-jUkrSSR

Bragin Korma Veprin Zlynka PolesskoeI I Novozybkov I Narodichi II „ > <__^_J v—^—J

UkrSSRBSSR RSFSR

Project results for blood lead levels in children from selected settlements. Project analyses of lead levels inthe blood of children from selected settlements indicated that environmental exposure to lead was low. Asillustrated here, the analyses of 185 samples taken from children aged 2-5 years in both surveyed contaminatedand surveyed control settlements were found to be well within the normal range (up to 29 pg/dl).

31


General Conclusions

There were significant non-radiation-relatedhealth disorders in the populations of both surveyedcontaminated and surveyed control settlementsstudied under the Project, but no health disorders thatcould be attributed directly to radiation exposure.The accident had substantial negative psychologicalconsequences in terms of anxiety and stress due to thecontinuing and high levels of uncertainty, the occur-rence of which extended beyond the contaminatedareas of concern. These were compounded bysocioeconomic and political changes occurring in theUSSR.

The official data that were examined did not indi-cate a marked increase in the incidence of leukaemiaor cancers. However, the data were not detailedenough to exclude the possibility of an increase in theincidence of some tumour types. Reported absorbedthyroid dose estimates in children are such that theremay be a statistically detectable increase in theincidence of thyroid tumours in the future.

On the basis of the doses estimated by the Projectand currently accepted radiation risk estimates, futureincreases over the natural incidence of cancers orhereditary effects would be difficult to discern, evenwith large and well designed long term epidemic-logical studies.


CURRENT HEALTH EFFECTSATTRIBUTED TO RADIATION

Reported adverse health effects attributed to radia-tion have not been substantiated either by those localstudies which were adequately performed or by thestudies under the Project.

Many of the local clinical investigations of healtheffects had been done poorly, producing confusing,often contradictory results. The reasons for thesefailures included: lack of well maintained equipmentand supplies; poor information through lack of docu-mentation and lack of access to scientific literature;and shortages of well trained specialists. Neverthe-less, despite these obstacles, a number of the localclinical studies were carefully and competently per-formed and the Project team was able to corroboratethe results in most cases.

SPECIFIC RESULTS OFPROJECT FIELD STUDIES

Field studies were undertaken of continuous resi-dents of rural surveyed contaminated settlements(with surface contamination higher than 555 kBq/m2

(15 Ci/km2) due to caesium) and surveyed controlsettlements of 2000 to 50 000 persons, using an agematched study design. The studies were performed inthe second half of 1990 and relate to the health statusat that time. The strategy of the study, to elucidatemajor health problems identified by general clinicalexaminations and sophisticated laboratory tests, wasadequate to answer most concerns of the population.There was no exhaustive testing of each individual,and the study did not resolve all questions relating topotential health effects.

Psychological Disorders

There were many important psychologicalproblems of anxiety and stress related to theChernobyl accident and in the areas studied under theProject these were wholly disproportionate to the bio-logical significance of the radioactive contamination.These problems are prevalent even in the surveyedcontrol settlements. The consequences of the accidentare inextricably linked with the many socioeconomic

32


and political developments that were occurring in theUSSR.

A large proportion of the population have seriousconcerns; these people are not acting in an irrationalway that could be termed radiophobic. The vastmajority of adults examined in both die surveyed con-taminated settlements and the surveyed control settle-ments visited either believed or suspected they had anillness due to radiation.

Most adults in both surveyed contaminated andsurveyed control settlements were native to the localarea and virtually all have stated that they have livedin the settlements since birth and therefore relocationis a major concern. While only about 8 per cent ofadults in surveyed control settlements wanted to relo-cate, the adults in the surveyed contaminated settle-ments were so concerned that 72 per cent wanted torelocate. The percentages of the population who thinkthat the Government should relocate the whole popu-lation are higher: 20 per cent and 83 per cent,respectively.

General Health

The children who were examined were found to begenerally healthy. Field studies indicated that therewere a significant number of adults in both surveyedcontaminated and surveyed control settlements withsubstantial medical problems, with 10 per cent toIS per cent (excluding hypertensive adults) requiringmedical care.

Cardiovascular Disorders

There were many hypertensive adults; however,the statistics related to both systolic and diastolicblood pressure were similar for both surveyed con-taminated and surveyed control settlements, and bothwere comparable with published values for Moscowand Leningrad.

Nutrition

Diet appeared to be limited in range but adequate.No significant differences in reported eating habitswere found between surveyed contaminated and sur-veyed control settlements. No detrimental effects ongrowth due to voluntary or official dietary restric-tions imposed as a result of die accident were found.There were no significant differences between thegrowth rates of children in surveyed contaminatedand surveyed control settlements, and the rates forboth groups are well within published USSR andinternational norms. Adults were generally over-weight by international standards in all areas studied.Intake and excretion of iodine were found to be at thelow end of the acceptable range. Most other dietaryconstituents and components were found to be ade-quate; however, vitamin intake was not examined.Dietary intakes of toxic elements (lead, cadmium,mercury) were low in comparison with those reportedfor many other countries and were well below diemaximum tolerable intake levels specified by interna-tional organizations. Blood lead levels were alsoinvestigated and were found to be well within thenormal range.

Thyroid Gland Disorders

No abnormalities in either thyroid stimulatinghormone (TSH) or thyroid hormone (free T4) werefound in children examined. No statistically signifi-cant difference was found between surveyed contami-nated and surveyed control settlements for any agegroup.

Mean thyroid sizes and the size distributions werethe same for populations of surveyed contaminatedand surveyed control settlements. Thyroid noduleswere extremely rare in children; they occurred in upto IS per cent of adults in both surveyed contaminatedand surveyed control settlements. Project results are

33


similar to those reported for populations in othercountries.

Haematology

Some young children with low haemoglobin levelsand low red cell counts were identified. However,there were no statistically significant differencesbetween values for any age group of the populationin surveyed contaminated and surveyed control settle-ments. No difference was found between the popula-tions when leucocytes and platelets were examined.Immune systems (as judged from the lymphocytelevel and the prevalence of other diseases) do notappear to have been significantly affected by theaccident.

Neoplasms

Review of USSR data indicated that reportedcancer incidence had been rising for the last decade(starting before the Chernobyl accident occurred) andhas continued to rise since the accident. The Projectteam considered that there had been incompletereporting in the past and could not assess whether therise is due to increased incidence, methodologicaldifferences, better detection and diagnosis or othercauses. The data did not reveal a marked increase inleukaemia or thyroid tumours since the accident;however, owing to the classification scheme used andother factors, the possibility of an increase in the inci-dence of these tumours cannot be excluded. Onlyhearsay information relating to such tumours wasavailable.

Radiation Induced Cataracts

There was no evidence of radiation inducedcataracts in the general population.

Biological Dosimetry

Chromosomal and somatic cell mutation assaysare still being completed on adults who had workedoutdoors, since their exposures were assumed to bethe highest. So far, no significant difference has beenfound between adults living in surveyed contaminatedand surveyed control settlements. The data obtainedwere consistent with the Project dose estimates.

Foetal and Genetic Anomalies

Review of USSR data for settlements in contami-nated areas of concern as well as for the Republics asa whole indicated relatively high infant and perinatalmortality levels. These levels prevailed before theaccident and appear to be decreasing. No statisticallysignificant evidence was found of an increase inincidence of foetal anomalies as a result of radiationexposure.

POTENTIAL DELAYED HEALTH EFFECTS

Available data reviewed do not provide an ade-quate basis for determining whether there has been anincrease in leukaemia or thyroid cancers as a con-sequence of the accident. The data were not detailedenough to exclude the possibility of an increase inthe incidence of some tumour types. On the basis ofthe doses estimated by the Project and currentlyaccepted radiation risk estimates, future increasesover the natural incidence of all cancers or hereditaryeffects would be difficult to discern, even with largeand well designed long term epidemiological studies.Reported estimates of absorbed thyroid dose inchildren are such that there may be a statisticallydetectable increase in the incidence of thyroidtumours in the future.

34


Recommendations

GENERAL HEALTH AND POTENTIALACCIDENT CONSEQUENCES

The adverse health consequences of relocationshould be considered before any further relocationtakes place.

Consideration should be given to the introductionof programmes to alleviate psychological effects.These might include informational programmes forthe public. There should also be educational pro-grammes set up for teachers and local physicians ingeneral preventive health care and radiation healtheffects.

The current policy of annual physical examina-tions is conceptually adequate for the health needs ofthe general population in the contaminated areas ofconcern. However, certain high risk groups (such aschildren with high absorbed thyroid doses) will needspecific medical programmes based on their potentialrisks.

Energetic action should be taken to improve thestandard of medical, diagnostic and research equip-ment and the availability of medical supplies,manuals and spare parts.

Clinical and research investigations should eippha-size the use of appropriate control groups, standardsand quality control procedures.

Improvements should be made in the statisti-cal, data collection and registry systems used bylocal scientists by the adoption and application ofinternationally accepted standards and methods.

There should be increased opportunities for infor-mation exchange and greater availability of scientificliterature for local health professionals.

POTENTIAL DELAYED HEALTH EFFECTS

In view of the limited resources available, the con-cept of the WHO Scientific Advisory Group on theHealth Effects of Chernobyl, namely to concentrateon prospective cohort studies of selected high riskpopulations, should be endorsed. It is impractical,owing to the extreme difficulty and cost, to conductlong term studies or to evaluate all persons who livein the affected Republics.

GENERAL PUBLIC HEALTH ISSUES IN THEAFFECTED REPUBLICS

Action should be taken on adult hypertension anddental hygiene as major health issues. The need forcontinuing programmes for iodization of salt shouldbe re-evaluated; if these are found to be necessary,the effectiveness of the chemical process should beassessed.

35

Chapter Five:Protective Measures

The Problem

A number of protective measures were institutedby the authorities after the accident to limit the radiationexposure of the population. These included earlycountermeasures (such as sheltering, administration ofstable iodine and evacuation) introduced largely to dealwith the effects from the plume of radioactive materialspassing over areas near the reactor. Intermediate andlong term countermeasures (such as relocation, restric-tion of foods, agricultural measures and decontamina-tion) were taken to deal with lower, but still significant,levels of radiation from surface and soil contamination.

Situations posing radiation hazards can be dividedinto two categories:

• Situations that result from the introduction ormodification of radiation practices that can there-fore be anticipated in advance; these require interalia the setting of dose limits to restrain the antici-pated increase in the radiation exposure that willresult from the practice; and

• Unforeseen, de facto situations, including post-accident contamination and emergencies, whichcall for intervention in the normal lives of thepublic to reduce the higher than normal radiationdoses to levels as low as reasonably achievableunder the prevailing circumstances.

Although international guidance and criteria on inter-vention existed before the accident, experience in theirapplication was very limited, especially in the area oflong term protective measures. The magnitude of theChernobyl accident and the extent of the areas affectedby it raised issues that had not been previously

addressed. Inevitably, under these circumstances, anevolutionary approach had to be developed for the prac-tical implementation of the criteria, especially for relo-cation. Because of this lack of previous experience thisevolving process, which affected the lives of manypeople, caused many problems. Particular concern wasexpressed about the concept put forward by the USSRauthorities of a 350 mSv 'lifetime dose limit'.

Decisions on protective measures became engulfed inthe changing socioeconomic situation in the USSR. Itwas these socioeconomic factors that dominated thegeneral thinking, almost to the exclusion of moredetailed considerations about radiological protectionprinciples.


Project experts primarily examined those protectivemeasures taken or proposed from 1990 onwards by theauthorities. This was a central issue in the USSR requestfor an international study. A more limited evaluationwas also made of measures taken prior to 1990, tounderstand how past actions may have influenced orconstrained future options. These measures were com-pared with international recommendations and evaluatedfor their appropriateness.

The current international radiological protection prin-ciples for situations requiring intervention following anaccident are as follows:

• The proposed intervention should do more goodthan harm, i.e. the reduction in the expected radia-tion harm resulting from the reduction in doseshould be sufficient to justify the harm and costs,including social costs, of the intervention itself;and

36

Chapter Five: Protective Measures

• The form, scale and duration of the interventionshould be optimized so that the net benefitachieved by the reduction in dose (i.e. the benefitfrom the reduction in the radiation harm less theharm associated with the intervention itself) ismaximized.

The dose limits recommended internationally areintended for use in the control of practices and do notapply to intervention. The use of these or any other pre-determined dose limits as the basis for deciding on inter-vention could involve measures out of proportion to thebenefits obtained, which would conflict with the princi-ple of justification. Therefore, the application of doselimits for deciding on the need for, or scope of, interven-tion is not recommended.

These principles guided the Project work on evaluat-ing the protective measures.

Towards the end of the Project a number of 'decisionconferences' were held with decision makers at both theRepublic and Ail-Union levels to enable the decisionproblems to be structured efficiently and to clarify andsummarize for the Project the socioeconomic and politi-cal factors that have influenced the decision makingprocess in the affected Republics.

Work in Detail

EARLY COUNTERMEASURES

Sheltering, thyroid blocking by the administration ofstable iodine and evacuation were introduced in varyingdegrees in the first days following the accident. Thereported radiation levels which triggered these counter-measures were well below the threshold doses at whichacute early effects of radiation occur.

Intervention levels for evacuation, in terms of doselevels projected over the first week after the accident,were established for both whole body and individualorgan exposures.

People were allowed to continue living in areas onlyif the projected doses were less than the interventionlevel. The authorities introduced evacuation measures assoon as it was established that the predicted doses werelikely to exceed the intervention level. If the dose rateon the first day after the accident exceeded 1 mSv/h(0.1 rem/h), evacuation was immediate and compul-sory. In areas with a dose rate of 0.1-0.3 mSv/h(0.01-0.03 rem/h), only women and children wereevacuated. Below a dose rate of 0.1 mSv/h(0.01 rem/h), no evacuation was introduced.

LONGER TERM COUNTERMEASURES:RELOCATION AND FOOD RESTRICTIONS

The current radiological protection task in theaffected areas is complicated by the large extent of theareas contaminated and the belief of the population thatthey are living in conditions that are very dangerous.The Supreme Soviet of the USSR established aprogramme with financial compensation for the two-year period 1990-1992 for relocation and a number ofmeasures to improve the living conditions in the affectedsettlements. Different relocation concepts have beenproposed: they include 'temporary annual dose limits','lifetime dose limit' and a surface contaminationconcept. In addition, contamination levels for variousfoodstuffs are in force.

Relocation Measures

Temporary Annual Dose Limits

Following the accident, die Ministry of Health of theUSSR, on the recommendation of its National Commis-sion for Radiological Protection, implemented a previ-ously prepared regulation establishing a temporaryannual dose limit of 100 mSv (10 rem) for whole bodyirradiation of the population in the first year after anaccident. The USSR Ministry of Health also approvedtemporary annual dose limits for the years 1986-1989.

37


800

|

600

400

200

Whole body

5000

4000

3000

I 2000CO

<

1000

Separate organs

ICRP IAEA WHO CECV. }

YInternational guidance

USSR ICRP IAEA WHO CEC

International guidance

USSR

Criteria for evacuation of the population in the early phase of the Chernobyl accident. While the Project teamwas not able to investigate in detail many of the early protective actions taken by the responsible authorities,it was judged that the general response of the authorities was broadly reasonable. As illustrated here, the inter-vention levels of absorbed dose for evacuation applied in the early phase of the post-accident response by theauthorities were consistent with general guidance prevailing at the time of the accident (the vertical columns indi-cate the upper and lower levels of the guidance values.)

180

160

140

£ 120

S. 100§ 80Q 60

40

20

0

(a)

125

100 •

1986 1987 1988 1989 1986- 1989

100Dose (mSv)

150 170

'Temporary annual dose limit' for the intermediate phase and reported estimated dose distribution. Duringthe intermediate phase of the post-accident response (1986-1989) new intervention levels of dose were estab-lished under the name 'temporary annual dose limits' (a). As illustrated here, the 'accumulated temporary doselimit' for 1986-1989 totalled 180 mSv. The officially reported dose estimates (b) for residents in areas withground contamination greater than 15 Ci/km2 (555 kBq/m2) showed a distribution with an average dose muchlower than 180 mSv.

38


Lifetime Dose Limit

In late 1988 the USSR National Commission forRadiological Protection recommended a lifetime doselimit of 350 mSv (35 rem) as the intervention level forrelocation. It was to be implemented beginning on1 January 1990. This limit was defined as the total inter-nal and external individual dose that would be accumu-lated by a child born in 1986 during a 70 year lifetime,and was to include the doses since 26 April 1986. Thelifetime dose limit of 350 mSv (35 rem) was said to givea high degree of safety as it included doses receivedfrom the date of the accident. Doses from the past wereincluded in order to reassure the public that there wouldbe no measurable biological effects from the projectedlifetime doses.

Surface Contamination Concept

In April 1990 the Supreme Soviet of the USSRintroduced a surface contamination concept as acriterion for both relocation and improvement of livingconditions in an attempt to move away from dose relatedconcepts. In this programme, relocation would be com-pulsory for people living in areas with a caesium surfacecontamination level above 40 Ci/km2 (1480 kBq/m2).As part of the programme to improve living conditions,people living in areas with contamination levels in therange 15-40 Ci/km2 (555-1480 kBq/m2) would be paidcompensation of 30 roubles per month and relocationwould be obligatory for pregnant women and childrenand optional for others. The programme would providecompensation of 15 roubles per month to people livingin areas with contamination levels in the range of1-15 Ci/km2 (37-555 kBq/m2) but relocation wouldnot be an option.

Food Restrictions

The intervention levels for foodstuffs apply to totalfood intake. In the first two months or so after the acci-dent, the main source of internal radiation dose was13'l, which was ingested mainly in milk from dairy

herds grazing in contaminated pastures. In order to limitthe iodine intake, temporary control levels were set forits content in milk and dairy products and strict radio-logical monitoring of all dairy products was started.Similar measures were taken to limit the intake ofcaesium (137Cs) in food, which remained the mostimportant source of radiation after the iodine had sub-stantially decayed. Internal contamination was reducedby restrictions on the consumption of contaminatedfood. Maximum permissible levels of contamination inbasic food products were set by the USSR Ministry ofHealth. In addition, the Republics and regions had theauthority to set their own levels.

1986 1987 1988 1989

Intervention levels of dose for food restriction. Theintervention levels of dose far food Restriction estab*lished by die authorities -were brotidiy consistent withinternational guidance prevailing at the time of theaccident. H* Project conducted tka\ "higher valuesof intervention levels would have been justifiable".Moreover, ' 'doses actually received... were substan-tially lower than the prescribed intervention levels ofdose, typically by a factor of 2-4".

39


LONG TERM RELOCATION CRITERIA

Long term relocation concepts were established at longer term, albeit well intentioned, generally exceed whatfirst on the basis of a lifetime dose of 350 mSv (35 rent) as would have been strictly necessary from a radiological pro-the intervention level for relocation, the so-called 'lifetime tection viewpoint." The table gives estimates of dosedose limit'. Subsequently, a surface contamination of averted for the various intervention concepts. The Commit-40 Ci/km2 (1480 kfiq/m2) was introduced as die inter- tee concluded that "measures are not justified on radiologi-vention level for relocation. The bases on which the criteria cal protection grounds; however, any relaxation of thefor relocation were derived were not wholly consistent current policy would almost certainly be counterproductivewith the principles currently recommended internationally, in view of the present high levels of stress and anxietyHowever, the International Advisory Committee concluded amongst inhabitants of the contaminated areas of concernthat "The protective measures taken or planned for the and people's present expectations."

Criterion

Temporaryannualdoselimit

Lifetimedose limit

Surfacecontamination

Yearof Level

application

1986 100 mSv per annum1987 30 mSv per annum1988 25 mSv per annum1989 25 mSv per annum

1990 350 mSv lifetime

1990 >40 Ci/km2 surface1990 < 15 Ci/km2 surface

Lifetime dose avertedLifetime dose averted from external radiation

from external radiation and residual(mSv) ingestion dose

(mSv)

-140 <240-130 <230-150 <260

- 60 <130

- 80 <160- 30 < 80

Systematic monitoring of the levels of contaminationof food products was also undertaken. There are threelevels in this control system, ranging from expertmonitoring provided by specialist organizations to massmonitoring by many different units in the food andagriculture industry.

A range of countermeasures has been developed andtaken with the aim of permitting the production of foodwith contamination below maximum permissible levels;

some of these measures have had the secondary benefitfor agricultural workers of reducing the external dosefrom deposited contamination and the inhalation ofresuspended radioactive materials.

DECISION CONFERENCES

The process of decision making for interventionpurposes is extremely complex and involves many

40


factors, including non-radiation-related factors. It wastherefore thought appropriate to hold five decision con-ferences, one in each of the affected Republics, one atthe All-Union level, and, subsequently, one at whichrepresentatives from the earlier conferences met to builda decision model that represented the main issues andconcerns.

The main aims of these conferences were to identifythe key socioeconomic and political issues influencingthe protective measures and to illustrate the potentialbenefits of formal techniques for the resolution of com-plex problems. The choice of participants was a matterfor the USSR and relevant Republic authorities.

Each decision conference began with a general dis-cussion of the key issues and concerns. The followingissues were regularly raised: the scale of the accident,the need for a safe living concept, health problems,stress, relocation, the lack of trust and understanding,the continuing risk from the 'sarcophagus' covering thedamaged reactor and the risk of water pollution. Therewas a consensus concerning the attributes or criteriaagainst which each strategy had to be evaluated. Themedical effects arising from stress in the populationsconcerned and public acceptability were the drivingforces or major criteria in evaluating strategies for thefuture. Reductions in radiological effects were of secon-dary importance compared with public acceptance. Theconferences achieved a considerable consensus on thestructure of the decision model and on the generalpattern of relocation and protection strategies toconsider.

All decision conferences discussed and evaluated arange of strategies for implementing relocation andother protective measures. All people receiving pro-jected doses in excess of an upper level would be relo-cated. Those receiving projected doses between an upperlevel and a lower level would be subject to protectivemeasures other than relocation and might also receivesome compensation. All those receiving doses below thelower level would not be subject to any protectivemeasures.

Long term countermeasures proposed (for example,'relocation' or 'safe living', which is understood as thewhole spectrum of actions envisaged in the threeRepublics for the non-relocated population, includingthe provision of clean food) ranged in cost per unitcollective dose averted from 300 000 to over1 000 000 roubles ($200 000-$700 000) per man-sievert. This range may be compared with values usedin western Europe for radiological protection decisionsrelated to the introduction or modification of practices of$10 000-$20 000 per man-sievert.

The lifetime doses for the period 1990-2060 areexpected to total about 50 000 man • Sv in the threeRepublics. In the decision processes in the Republics,therefore, it was apparent that the reduction of objectivehealth effects was of less overall importance thanmatters having to do with public acceptance. The con-siderable expenditures allocated to future counter-measures seemed disproportionate to the effectiveradiological protection achieved by relocation.

Socioeconomic and political issues have thus becomethe most important factors in the official decisionprocess. It should be recognized that ignoring the cost-benefit ratio of severe countermeasures such as reloca-tion is inappropriate. If the population believe thatcountermeasures are introduced with the prime purposeof protecting them against health effects, they will pressdecision makers to reduce intervention levels evenfurther. The decision makers, striving for broad publicacceptance of their decisions to calm popular unrest,may reduce the levels even when they are aware that thiswill not effect any significant improvement in the healthconditions and may cause the misallocation of scarceresources in the name of radiological protection.

It is, therefore, of great importance that decisionmakers inform the population of all aspects of their deci-sions, especially when the intervention levels chosen arebased mainly on socioeconomic or political, rather thanradiological protection, objectives. Otherwise, the popu-lation will be misled and the radiological protectioncommunity will be mistrusted.

41


General ConclusionsThe unprecedented nature and scale of the

Chernobyl accident obliged the responsible authori-ties to respond to a situation that had not been plannedfor and was not expected. Thus, many early actionshad to be improvised. The Project teams were notable to investigate in detail many actions taken by theauthorities owing to the complexity of the events.In those cases in which the Project teams were ableto assess these actions, it was found that thegeneral response of the authorities had been broadlyreasonable and consistent with internationally estab-lished guidelines prevailing at the time of theaccident. Some measures could doubtless have beenbetter or taken in a more timely manner, but theseneed to be viewed in the context of the overallresponse.

The protective measures taken or planned for thelonger term, albeit well intentioned, generally exceedwhat would have been strictly necessary from a radio-logical protection viewpoint. The relocation andfoodstuff restrictions should have been less extensive.These measures are not justified on radiological pro-tection grounds; however, any relaxation of thecurrent policy would almost certainly be counter-productive in view of the present high levels of stressand anxiety amongst inhabitants of the contaminatedareas of concern and people's present expectations. Itis recognized, however, that there are many socialand political factors to be taken into consideration,and the final decision must rest with the responsibleauthorities. At any rate, no modification introducedshould lead to more restrictive criteria.

Detailed ConclusionsEVACUATION AND THYROID BLOCKING

The intervention levels of dose for evacuationestablished by the authorities were consistent withinternational guidance at the time of the accident.

The general policy for administration of stableiodine established by the authorities was in compli-ance with the international guidance at the time of theaccident. The numerical values of the interventionlevels, however, were not in full agreement withthose recommended internationally.

The resources required to evaluate the practicalimplementation of these two protective measureswere far in excess of those available within theProject. Consequently, only a superficial analysiswas made of these aspects, on which no furtherconclusions can be made.

SURFACE DECONTAMINATION

Efforts were made after the Chernobyl accidentover a period of several months to reduce externalexposure due to radioactive materials that werereleased in the accident and deposited on surfaces.The wide range of measures taken included: theremoval of soil to a depth of 10-15 cm; asphaltingand covering soil with gravel, broken stones, sandor clean soil; daily mechanized washing; surfacewashing; demolition of structures; and burial ofwaste. These measures are reported to have beenmoderately effective; however, the Project teams didnot specifically investigate these reports.

FOOD RESTRICTIONS

Criteria

The basis on which the intervention levels for foodrestrictions established by the authorities werederived was broadly consistent with internationalguidance prevailing at the time of the accident. Therewas, however, considerable ambiguity in the interna-tional guidance. Furthermore, the derived levels ofradionuclide concentrations for various foodstuffs

42


established by the authorities were based on con-sideration of the most exposed persons, i.e. the criti-cal group, as opposed to the average individual in theaffected group.

With allowance made for the differences in formu-lation between the respective criteria, the interventionlevels established by the authorities are at the lowerbound of the range recommended internationally. Inview of the scale of the accident, the extent overwhich restrictions were needed and the shortcomingsin food supply and distribution in the areas con-cerned, higher values of intervention levels wouldhave been justifiable.

Impact

Doses actually received due to the ingestion ofcontaminated foodstuffs were substantially lowerthan the prescribed intervention levels of dose,typically by a factor of 2-4, and as a consequencefoodstuffs may have been restricted unnecessarily.

The social consequences, including costs, ofbanning the consumption of foodstuffs were in manycases disproportionate to the doses averted.

Relaxation of the criteria for foodstuffs should beconsidered as a preferable alternative to relocationwhen overall health, social and economic effects:aretaken into account. Continuing restrictions on theconsumption of domestically produced food in:thecontaminated areas of concern imply for some peoplea serious deterioration in the quality of life whichmay only be remedied by relocation to areas whereprevious lifestyles can be resumed. The relativelylow intervention levels adopted for foodstuffrestrictions may have exacerbated these problems.

An immense and largely successful effort has beenmade by the authorities to contain the agriculturalconsequences of the Chernobyl accident. Greatefforts have also been made to reduce radiation risksto the population as a whole and to agricultural

workers and their families in particular. The negativesocial effects of agricultural countermeasures couldbe further reduced by employing certain types ofcaesium binder.

RELOCATION

Criteria

The bases on which the criteria for relocation werederived by the authorities are not wholly consistentwith the principles currently recommended interna-tionally; this, however, does not necessarily implythat the quantitative criteria adopted areinappropriate.

In establishing relocation criteria, there werevarious conceptual misunderstandings and termino-logical problems among the parties concerned(including central and local authorities) that con-tributed to many of the present problems:

• The use of imprecise terminology and the mis-understanding and/or misrepresentation ofsome fundamental radiological protection con-cepts and principles, on the part of both thescientific community and others, have been aSource of much needless confusion and dis-agreement in the USSR. This, taken togetherwith the considerable delays in developingpolicy and effectively communicating it, hasbeen largely responsible for the failure to reacha broad consensus on relocation policy. More-over, it has contributed to a loss of confidenceon the part of the affected population in themeasures being taken in their interest.

• , One of the more important misunderstandingsor misrepresentations has been confusion over,and lack of recognition of, the very differentorigins and purposes of the dose limits recom-mended internationally for controlling planned

43


increases in radiation exposure and those of thedose levels at which intervention is prompted toreduce existing radiation exposures. Doselimits per se are not the appropriate levels atwhich to intervene following an accident. Thedose averted by relocation is the relevant quan-tity for judging the radiological benefits of relo-cation and, where practicable, quantitativecriteria should be expressed in terms of thisquantity.

It is not evident that considerations of averted dosewere at the origin of all the criteria that have beenproposed by the authorities. Criteria may also beformulated in terms of other, more useful derivedquantities that are surrogates for averted dose (forexample, contamination level, annual dose, lifetimedose or dose rate). A number of these have been usedin the USSR, each having merits and disadvantages.In particular, surface contamination is not generallyapplicable for dose estimates because there is a strongdependence of dose estimates on local soil conditions,food consumption habits and lifestyle.

Social Impact

It appears that due account has not been taken bythe authorities of the many negative aspects of reloca-tion in formulating the relocation policy. There areindications from studies in other areas that the massrelocation of people leads to a reduction in averagelife expectancy (through increased stress and changesof lifestyle) and a reduced quality of life in a newhabitat.

In applying a lifetime dose criterion for relocation,it is inappropriate to take account of past doses. Inter-vention may reduce the risk of adverse health effectsin proportion to the dose averted but it can have noinfluence on doses already received before the inter-vention. For dose ranges below the threshold for

deterministic effects, it is conceptually unsound andin contradiction to the principles for intervention totake past doses into account. There are, however, cir-cumstances in which the total, past and projected,doses received may be the relevant quantity, forexample in judging the need for and extent of anylong term medical follow-up or care of those exposedas a result of the accident.

The cautious approach adopted (i.e. overesti-mates) in the estimation of doses to people living inthe contaminated areas of concern, on the groundsthat this was in their best interest, was inappropriatein principle and contradictory to the fundamentalobjectives of intervention. It had two important nega-tive consequences: firstly, the radiological conse-quences of continuing to live in contaminated areaswere overstated and this contributed to additional andunnecessary fear and anxiety in the population;secondly, and more importantly, some people will berelocated needlessly.

The average levels of individual lifetime dose thatcould potentially be averted by relocation, promptedby either the 350 mSv (35 rem) or the 40 Ci/km2

(1480 kBq/m2) criterion, are of the same order as orless than the doses due to average natural backgroundradiation.

It is not clear that the modest nature of the dosesthat could be averted by relocation, and their assumedrisks, are fully appreciated by either the population ofthe contaminated areas of concern or many of thosepeople advocating a more stringent regime. The extraincremental risk to which an individual remaining ina contaminated area would be exposed would be mar-ginal in comparison with risks experienced in every-day life and in itself would not justify such a radicalmeasure as relocation.

Policy Reappraisal

On strictly radiological protection grounds, therecan be little if any justification for the adoption

44


of more restrictive relocation criteria than thosecurrently adopted in the All-Union programme (i.e.40 Ci/km2, or 1480 kBq/m2). Indeed, a reasonablecase could be made for a relaxation in the policy, i.e.for an increase of the intervention levels.

A much larger number of people than those livingin settlements with contamination levels in excess of40 Ci/km2 (1480 kBq/m2) are to be relocated; thedoses averted by the relocation of these people will besignificantly less than the modest values alreadyindicated. The implications of this are that morerestrictive criteria are being adopted in practice.

Many factors, other than those of a strictly radio-logical protection nature, have had an important andpossibly overriding influence on relocation policy.The need to restore public confidence, which hasbeen seriously eroded for many reasons over the pastfive years, to reduce anxiety and to gain broad accep-tance for the policy was identified to be particularlyimportant. In ongoing reappraisals by the authoritiesof the relocation policy, these factors are beingassigned much greater weight than factors of a strictlyradiological protection nature. The relative impor-tance to be attached to the various factors is,however, a matter for the relevant authorities.

Future changes in relocation policy will inevitablybe constrained by past actions. Notwithstandingthe merits of and technical justification for a changein policy, acceptance of major changes would bedifficult to achieve, particularly where these involveda relaxation in the criterion previously adopted. Arelaxation in the current relocation policy (i.e. ahigher intervention level) would, however, almostcertainly be counterproductive given the verydifficult social conditions in the contaminated areasof concern. There can be no justification on radio-logical protection grounds for the adoption of a morerestrictive policy. This should be strongly resistedunless there are overriding considerations of a socialnature.

Recommendations

PROTECTIVE MEASURES

Arrangements should be made in the future for thecompilation of a comprehensive and agreed databasecontaining all relevant information on the implemen-tation and the efficacy of the protective measurestaken and this should be processed into a coherentframework.

A complete and detailed evaluation should bemade of the protective measures taken (or planned tobe taken) in order to validate the conclusions of theProject study. This should cover all aspects related toradiological protection, i.e. the doses, the costs andthe efficacy of the protective measures.

Agricultural measures that may have a lessadverse impact on traditional agricultural practicesshould be investigated.

PUBLIC INFORMATION

Factors that may influence the acceptability to thelocal population of continued habitation of settle-ments in the contaminated areas of concern should befurther identified and analysed.

More realistic and comprehensive informationshould be provided to the public on the levels of doseand risk consequent upon their remaining in the con-taminated areas of concern. These risks should becompared with risks experienced in everyday life andwith risks from other environmental contaminants,e.g. radon and industrial emissions.

RESOURCE ALLOCATION

A comparison should be made between the effec-tiveness of resources allocated to the mitigation of theconsequences of the accident and those allocated else-

45


where to other programmes for public health individual settlements, chosen to encompass theimprovement. range of different characteristics encountered, in

An assessment should be undertaken of the cost order to confirm the validity of the conclusionsand effectiveness of relocation for a number of reached for average settlements.

46

Appendix

Historical Portrayal

Sources for this appendix include published materialon the Chernobyl accident and the interviews conductedby Project experts with people living in the affectedareas as well as with governmental officials and scien-tists. This portrayal is in no way intended to implyjudgements based on hindsight or to detract from thecourage of those who acted to save the lives of others,or to criticize those who made difficult decisions on thebasis of limited information.

Emergency Actions at the Site

In the early hours of Saturday 26 April 1986, an acci-dent which was to have global repercussions occurred atUnit 4 of the Chernobyl nuclear power plant in theUkrSSR. Seconds past 01:23 Moscow time, two explo-sions in quick succession blew the roof off the Unit 4reactor building. Concrete, graphite and debris escapedthrough a hole which exposed the reactor core. Smokeand fumes along with a large amount of radioactivematerial rose in a hot plume almost 2 km high to becarried throughout the western portions of the USSR, toeastern and western Europe, and — in much smalleramounts — through the Northern Hemisphere. Heavierdebris and particles fell near the site while lighterparticles were carried west and north of the plant to thesurrounding areas and neighbouring Soviet Republics.

Fires broke out on the roof of the adjoining turbinebuilding. Fire, along with clouds of steam and dust,filled the Unit 4 building. Alarms went out to fire unitsin the region and within minutes plant firemen arrived.None of the firemen had been trained in fighting firesinvolving radioactive materials. Some set to work withplant personnel in the turbine hall and the Unit 4 build-ing while others climbed to the roof of Unit 3, wherethey had to deal with burning graphite from the exploded

core. By dawn on Saturday all but the graphite fire in thecore had been extinguished.

An explosion of this nature had not been consideredpossible by many Soviet nuclear experts and the initialreports of core destruction by workers who entered theUnit 4 building were not believed. Operators continuedto direct water into the reactor building in a vain attemptto cool the reactor core and this contaminated waterflowed to building levels that crossed to other units,causing later contamination problems.

Rescue workers, firemen and operating personnelwere generally unaware of the seriousness of the radia-tion risk. The high radiation levels could not be meas-ured with available monitoring equipment and in someareas must have exceeded 100 Gy/h. Personnel had nodosimeters to measure their radiation dose and manywere seriously irradiated. Less than an hour into theemergency the first case of acute radiation syndromewas evident. The number of persons, present at thereactor site in the early hours of 26 April who showedclinical effects due to radiation exposure or burnswas 203.

Signals indicating a serious accident involving anexplosion, fire and radiation from Chernobyl weretransmitted automatically to the State Committee on theUtilization of Atomic Energy in Moscow moments afterthe accident. As the information accumulated, eventhough the magnitude of the accident had not yet beenfully established, it was decided to send key people fromMoscow to direct operations. Top officials were calledtogether as a Governmental Commission to provide theauthority to mobilize resources. The plant managementdid not have the resources or authority to manage theresponse to an accident of this scale and it was theGovernmental Commission itself that directed opera-tions. Unit 3 was shut down around 03:00, an hour anda half after the accident, while Units 1 and 2 were not

47

Appendix: Historical Portrayal

shut down until the following night, about 24 hourslater.

Army forces were asked to carry out the first radio-logical assessment and to assist in controlling the fires.Early measurements showed neutron emissions, indicat-ing continuing nuclear reactions in the destroyed Unit 4core. As the accident would be more devastating if itspread to the other units, the Governmental Commissiongave first priority to graphite fires.

The plant emergency plan was not suitable for anaccident with large and continuous releases of radio-active material. Emergency facilities and emergencyequipment were insufficient. There were no individualdosimeters for the emergency response units and noautomatic radiation monitoring stations in the environs.Civil defence authorities specified possible shelters andproposed that the Pripyat town executive committeeinform the population by radio of the radiation danger,but this was only done on Sunday just before theevacuation.

High radiation levels forced the GovernmentalCommission to move its headquarters from the town ofPripyat, 3 km from the reactor, to the town ofChernobyl, IS km south-southeast of the plant, on4 May. There were now thousands of people working onthe site and the organizational responsibility to providethem with equipment and food was transferred to theDeputy President of the Council of Ministers of theUSSR, who set up an operations management centre.

With the destroyed core open to the atmosphere, itwas decided to cover the crater with heat absorbent andfiltering materials. Airforce pilots flew hundreds ofhazardous missions over the core, from 27 April to10 May, in helicopters rigged to drop tonnes of boron,lead, clay, sand and dolomite.6 A growing concern was

6 The materials were chosen for specific purposes: boronto absorb neutrons and to prevent the reactor from becomingcritical again; lead to absorb heat and act as shielding; clay andsand to filter out radioactive panicles; and dolomite to give offcarbon oxide to reduce the flow of oxygen to the graphite fire.

the possibility that molten fuel would reach the water inthe pressure suppression pools below the core, causingsteam explosion and further releases. Under extremelydifficult conditions and in a radioactive environment,military volunteers managed to rig up temporary pipingto pump out water that had filled the normally drysecond level. The command team also undertook theinstallation of a concrete slab underneath the damagedreactor to prevent any molten fuel from damaging thefloor structure and leaking into the ground below.

Evacuation of the Prohibited Zone

EVACUATING PRIPYAT

Early on Saturday 26 April the explosion and fire atthe plant were reported to BSSR and UkrSSR anddistrict civil defence authorities. Within hours, aUkrSSR headquarters had been set up in Pripyat andpolice established roadblocks to prevent all but emer-gency vehicles from entering. By noon, regular radia-tion monitoring had begun in and around Pripyat. Thehighest readings were found just to the west of the plant,but the wind was light, slowing the spread of radioactivematerial. Civil defence officials prepared for Pripyat'sevacuation although only the USSR Government had theauthority to initiate it.

By the evening, radiation levels were up to1000 times natural background radiation (0.1 mSv/h) inPripyat. Although the radiological situation was not yetconsidered alarming, the physicists on the GovernmentalCommission were recommending evacuation as theywere uncertain about the condition of the reactor coreand the future course of the accident. The Commissiondecided at about 22:00 to evacuate the population on the

next day, 27 April. They contacted transport officialsfrom as far away as Kiev and arranged for more than athousand buses, which arrived throughout the night.Officials in the nearby towns of Polesskoe and Ivankovwere alerted to prepare for receiving the evacuees.

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Evacuation routes were chosen in accordance with arearadiation measurements and precise instructions forleaders, drivers, police and evacuees were prepared.

Meanwhile, because of the obvious severity of theaccident — the explosion had been heard, smoke and firewere visible, civil defence forces were monitoring thecity, injured were arriving at the hospital and plantworkers had alerted their families and others — someofficials took action on their own initiative. Theywarned others to stay indoors and distributed availablepotassium iodide tablets. Some teachers, recallingearlier civil defence training, cancelled Saturday out-door events. They kept students indoors and attemptedto prevent contaminated outdoor air from entering thebuildings. Other people decided to leave Pripyat by trainor river boat before the service would be cut off, andthose who could left by car before roadblocks would bein place.

Officially, life in Pripyat was allowed to proceedmore or less normally on Saturday. Steps were taken toprevent panic. Civil defence officials did not use facemasks until after the evacuation as there had not beenenough to supply the children. An amusement parkwhich had been brought back into use only a few daysbefore was open, with many people present. There wereno official warnings or instructions to stay indoors andno systematic distribution of potassium iodide tablets.

At 07:00 on Sunday morning, 27 April, the head ofthe Governmental Commission confirmed the decisionto evacuate Pripyat. He met with Pripyat town officialsat 10:00 and instructed them to prepare for evacuationat 14:00. Around noon, a short official announcementwas broadcast to city residents to pack provisions forthree days and to be ready to leave at 14:00. The nearly1200 buses assembled near the town of Chernobyl wereset in motion in a line several kilometres long and theevacuation of Pripyat began at 14:00, just over 36 hoursafter the accident.

The number of people to be transported was less thanthe projected 44 600 as some had already left or wereaway for the weekend. There was adequate transport and

the evacuation went smoothly. In less than three hoursthe city was emptied of all but those with official duties.The evacuees were taken in by individual families intowns or villages in the surrounding regions.

EXPANDING THE EVACUATION ZONE

On 28 April, the civil defence authorities of theUkrSSR and the USSR proposed the establishmentof a 10 km exclusion zone around the plant. On 2 May,high governmental officials arrived from Moscow.Prime Minister Ryzhkov, who could call upon the indus-trial resources of the USSR, created an operationalgroup of the Politburo Central Committee to direct thenational effort. Fundamental decisions could now betaken regarding necessary work as well as the contribu-tions and participation required from organizationsthroughout the USSR.

On 2 May it was decided to evacuate people from azone of 30 km radius around the reactor; this zonebecame known as the prohibited zone. The evacuation ofthe entire prohibited zone was completed on 6 May. Itwas an undertaking requiring transport of thousands ofpeople and thousands of farm animals. The zone wasfenced off and access has been controlled ever since.While the area still remains evacuated, numerous peopleenter and leave to work at the site and in cleanup andresearch activities in the town of Chernobyl. A substan-tial number of people who left their homes later returnedsurreptitiously and some families have reportedly beenallowed to return in less contaminated southern areas ofthe zone. In addition to the 30 km prohibited zone, eva-cuations were carried out from territories east and westof the zone where radiation levels exceeded 50 /*Sv/h(5 mrem/h). On 10 May a dose rate map was drawn withisopleths: a rate of 200 /iSv/h (20 mrem/h) formed theboundary of the prohibited zone (about 1100 km2 inarea), 50 /*Sv/h (5 mrem/h) the boundary of the evacua-tion zone (3000 km2) and 30 pSv/h (3 mrem/h) that ofthe strict controlled zone (8000 km2), from whichchildren and pregnant women had to be temporarily

49


evacuated. The maps of contamination by long lived iso-topes prepared in June and July 1986 showed that re-settlement had to be carried out from an additional29 settlements in the BSSR and 4 in the RSFSR.

Securing the Site

It was necessary to isolate the destroyed and contami-nated reactor building. Engineers decided on a structuralcovering with a span of 55 m that used remaining wallsas supports. Design work and construction proceededquickly, allowing Unit 4 to be enclosed inside a concreteand steel shell by mid-November 1986. In order tomonitor conditions inside the structure, both gammaradiation and temperatures are measured in various loca-tions. Approximately 96 per cent of the fuel remains inthe reactor and the premises of Unit 4. A steadilydecreasing gamma dose rate indicates that the fuel is ina stable condition.

Because of the difficult conditions under which itwas built, as well as the need to ventilate it, the'sarcophagus' was not sealed from the environment.Spaces exist between construction elements in the upperpart of the structure and there are holes in the roof toprovide natural convection inside. The spaces are moni-tored for radioactive emissions.

Radiation Release and Transport

It is estimated that 25 to 50 million curies of radio-active elements were released from the reactor core. Theintense heat increased the release of the volatile isotopesof iodine and caesium. There were approximatelyten million curies of iodine released and approximatelytwo million curies of caesium. The releases did notoccur in a single large event. In the five days thatfollowed the initial release, the release rate declined,reaching a minimum of approximately 15 per cent of theinitial release rate. During the following four days the

release rate increased to about 70 per cent of the initialrate. A sudden drop to less than 1 per cent of the initialrate then occurred, with a continuing decline thereafter.

During the first day, the plume above the plantreached 1800 m. By the following day, the maximumheight was 1200 m, with the bulk of the material beingreleased not exceeding 600 m. From the third dayonward, the plume did not exceed 600 m.7 At the timeof the accident, surface winds were light and variable,but at 1500 m altitude the winds were 8-10 m/s from thesoutheast. Material carried to this height was transportedtowards Finland and to Sweden, where radioactivity wasfirst detected outside the USSR on 27 April. MoscowTV broadcast news of the accident on the evening ofMonday 28 April.

By 7 May, maps of radiation levels over the Euro-pean territory of the USSR were completed on the basisof data collected by aerial surveys. From then on, theUSSR Hydrometeorology Institute released data ona daily basis with forecasts of transfer trajectoriesat various altitudes which were transmitted to localauthorities and to the Ministries of Health andAgriculture.

Protection of Rivers andthe Kiev Reservoir

One of the more critical issues was the potential forcontamination of the water system and from the firstdays after the accident, studies of water contaminationwere begun by the State Committee on Hydrometeoro-logy. Monitoring of radionuclide concentrations in thearea of the River Dnepr and its tributary the Pripyat indi-cated that contamination was principally from fallout

7 The volatile elements iodine and caesium were detectedat even greater altitudes (6-9 km), with traces also in die lowerstratosphere. The heavier elements, such as cerium, zirco-nium, neptunium and strontium, were of significance only inlocal deposition within the USSR.

50


since there was a sharp reduction in radionuclideconcentration as the airborne contamination decreased.

In the very first days after the accident, estimateswere made of the concentrations of radioactive contami-nation in water bodies due to the fallout and of projectedconcentrations if rainfall were to bring additional radio-active contaminants from the ground into the water sys-tem. Calculations showed that in the event of intensiverainfall in the vicinity of the River Pripyat, the concen-tration of the most critical radioactive isotope ^Srwould not exceed the limits set for drinking water bythe USSR regulations, provided releases from the reac-tor would soon be terminated. Later measurementsconfirmed this forecast.

Owing to the heavy fallout in the immediate vicinityof the reactor, the nature of the soils in the area and thedirect connection through the nearby cooling pond toKiev's principal reservoir on the River Dnepr north ofKiev, a good deal of effort was made to slow the move-ment of long lived radionuclides (such as 137Cs and^Sr) through ground or surface water. There werethree major undertakings. First, 140 dams and dikeswere built to limit runoff from the site area into the cool-ing pond and the adjacent River Pripyat. Second, aseries of existing silt traps at the bottom of the rivers, thepond and the reservoir were scoured. Third, an 8 kmlong barrier, 30-35 m deep, was built around the plantdown to the impermeable clay layer to prevent the flowof radioactive water towards the River Dnepr.

Decontamination

After the major releases from the plant had subsided,decontamination was undertaken to reduce dose rates inareas from which the population had not been moved.Primary attention was given to municipal buildings suchas schools, nurseries and hospitals while contaminatedbuildings of lesser importance were demolished and thewaste buried.

At first, officials declared that much of the evacuatedterritory could be reoccupied after decontamination.However, in many cases decontaminated surfacesquickly became recontaminated owing to resuspensionof radionuclides migrating from land, vegetation andstructural surfaces. The most effective decontaminationproved to be natural processes ('biological decontamina-tion') such as decay and migration into the ground, andactive decontamination work in most settlements hasbeen discontinued.

Intervention Measures

After the initial evacuations, the USSR NationalCommission on Radiological Protection formulatedintervention criteria for reducing exposure due to con-taminated food and water. The main sources of exposurechanged with time, as did the measures taken to controlthem. In the first few months, exposure was due toradioiodine in milk from cows that had grazed on con-taminated pastures and this was dealt with through inter-vention measures such as the provision of potassiumiodide and the supply of clean milk. At the same time,the problem of radioiodine and other nuclides depositedon fresh vegetables was addressed through interventionmeasures such as the supply of clean food. Over the longterm, the principal exposure was due to 137Cs in milk,meat and other foods and this was dealt with throughintervention measures restricting food production andconsumption, and changes in agricultural management.

ESTABLISHING THE SAFE LIVING CONCEPT

The radiation protection situation was complicated bythe extent of the areas contaminated and the huge controlprogramme necessary for measuring both environmentaland food contamination. A number of safe living con-cepts have been proposed, including a temporary doselimit introduced during the first year, a lifetime doselimit concept, a two-tier lifetime dose limit concept, a

51


dose rate concept and a surface contamination concept.The USSR Ministry of Health introduced a maximumtemporary dose limit of 100 mSv (10 rem) for the firstyear after the accident. A set of additional temporarydose limits for the years 1987-1989 were laterapproved.

By early 1987, it became increasingly apparent thatthe food and behavioural restrictions were having amajor impact on everyday life in the three Republics.Authorities recognized that the system of restrictions onfarming in the predominantly rural, agricultural regionswould not be satisfactory in the long term. In late 1988they proposed a lifetime 'safe living concept' that was todefine radiological conditions under which people werenot subject to restrictions on their diet or lifestyle. Thisset the lifetime dose limit over 70 years from the timeof the accident at 350 mSv (35 rem). The limit was anaction/no-action level concept. The concept wasapproved by the Council of Ministers of the USSR inSeptember 1988.

By the beginning of 1989, however, the lifetime doselimit concept was being seriously criticized. Proponentsof the concept argued that lower values would result insevere disruption as a result of excessive relocation. Asa result of mounting criticism it was expanded to a two-tier system. This modified version included a lower levelof lifetime dose (70 mSv (7 rem)) below which no actionwas to be taken. Between the lower and the upper levels(still 350 mSv (35 rem)), varying measures would beintroduced. Above the upper level, relocation remainedcompulsory.

In April 1990 the Supreme Soviet of the USSRintroduced a surface contamination concept as acriterion for both relocation and payment of compensa-tion. This divides the affected areas into three classes ofzones8: those with a surface contamination level of

caesium above 40 Ci/km2 (1480 kBq/m2); those withlevels in the range 15-40 Ci/km2 (555-1480 kBq/m2);and those in the range 1-15 Ci/km2 (37-555 kBq/m2).Relocation and other forms of compensation woulddepend upon which zone a settlement was in.

The policies on protective measures and relocationwere not understood by the general public and con-tributed to a distrust of both the scientific and politicalauthorities. Growing reports of widespread healtheffects also had a particularly strong impact on thepublic. This situation was not helped by officials whobegan attributing public fears to 'radiophobia' or undueconcern about radiation and its health effects. When the'safe living concept' was announced in early 1989, itimmediately became the target of criticism in the threeaffected Republics where many people, including scien-tists, disagreed with the permitted radiation exposurelimits.

This was done despite the fact that there is no simplerelationship between the surface contamination level andannual dose or lifetime dose because of differences in transferfactors, living conditions and eating habits.

Soviet Requests for Assistance

The current situation in the USSR is reflected in aresolution "On the Political Evaluation of the ChernobylNuclear Power Station Disaster and Progress inEliminating its Aftermath" which was adopted in July1990 at the 28th Congress of the Communist Party of theSoviet Union:

"...the CPSU Central Committee Politburo, theUSSR Council of Minister, the Central Committeesof the Communist Parties of the Ukraine and Byelo-russia, and the Councils of Ministers of the Ukraineand Byelorussia, failed to assess the scale of thedisaster and its possible consequences promptlyenough, or to work out and resolutely implement agovernment concept of safe residence in contami-nated areas.

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Social tensions in the afflicted areas are rising. This In 1989, during the period of ferment leading tois prompted by the long and unjustified secrecy sur- the resolution of the Congress, international organiza-rounding the Chernobyl tragedy, the conflicting tions were asked to help investigate the general healthevaluations, especially of the medical aspects, and the and welfare situation. The WHO sent a team of officialsshortage of unbiased information made available to in 1989, as did the League of Red Cross and Redthe population about the actual state of affairs. Crescent Societies in early 1990. It was in October of

1989 that the USSR Government made its request to theThe Congress admits that the measures taken to IAEA for assistance, resulting in the present study whicheliminate the aftermath of the Chernobyl disaster was carried out under the International Advisorywere unsatisfactory and insufficient." Committee.

53

Epilogue

The accident at Chernobyl had a societal impactunparalleled in industrial history. The early conse-quences resulted in the evacuation of more than100 000 people and involved hundreds of thousands ofrescue workers. Vast populations in the BSSR, theRSFSR and the UkrSSR continue to live with stress andanxiety due to the lingering uncertainty about the future.The International Chernobyl Project launched in 1990was an important step in assisting the affected popula-tion. Additional initiatives are already under way to dealwith the many consequences of the accident.

In response to Governmental appeals for assistance,the United Nations system has launched a number ofactivities. The General Assembly adopted, on21 December 1990, resolution 45/190, which requeststhe Secretary General:

" ... to support efforts made within the UnitedNations system by the Administrative Committee onCo-ordination and the Inter-Agency Committee fordie Response to Nuclear Accidents to harmonize,strengthen and co-ordinate international projectsdealing with mitigating the consequences of thedisaster at Chernobyl ..."

The resolution urgently appealed:

" ... to all States members of the international com-munity, intergovernmental and non-governmentalorganizations, the business community, scientificbodies and individuals to continue to provide allappropriate support and assistance to the areas mostaffected by the accident at die Chernobyl nuclear

power plant, in full co-ordination and co-operationwith envisaged or planned efforts of the UnitedNations system."

The United Nations Secretary General has appointedthe Director General of the United Nations Office inVienna to co-ordinate assistance within the UnitedNations system. A task force is currently concentratingits efforts on the enormous economic and social con-sequences. The Inter-Agency Committee for theResponse to Nuclear Accidents, formed shortly after theChernobyl accident, is encouraging its United Nationssystem members to carry out research aimed at betterunderstanding environmental contamination, agricul-tural measures, radiological protection and emergencymanagement following a large release of radioactivematerial.

The World Health Organization is proceeding withplans for a long term international programme for thestudy of medical aspects of the Chernobyl accident andfor die establishment in die USSR of a WHO interna-tional centre to study radiation medical problems.

The BSSR, the UkrSSR and the USSR recently estab-lished the Chernobyl Centre for International Research.The area around Chernobyl affords opportunities forscientific investigations into post-accident conditions.The IAEA will have a role in the development and co-ordination of research at the Centre as well as in thedissemination of die results.

International collaboration in die growing number ofhumanitarian and scientific efforts will be an essentialingredient in fully alleviating die consequences of dieChernobyl accident.

55

International Advisory Committee

Shigematsu, I. (Chairman)Radiation Effects Research Foundation, Hiroshima, Japan

Rosen, M. (Vice Chairman)International Atomic Energy Agency, Vienna

Members

Anspaugh, L.R.Lawrence Livermore National Laboratory, Livermore,

California, United States of America

Bar'yakhtar, V.G.Academy of Sciences, Kiev,

Ukrainian Soviet Socialist Republic

Bennett, E.G.United Nations Scientific Committee on the

Effects of Atomic Radiation, New York

Coppee, G.H.International Labour Office, Geneva

Coulon, R.Commissariat a l'6nergie atomique, Fontenay-aux-Roses,

France

Fry, F.National Radiological Protection Board, Chilton, Didcot,

United Kingdom

Gheorghiev, G.K.Food and Agriculture Organization of the United Nations,

Rome

Gubanov, V.A.State Committee on the Rectification of the

Consequences of Chernobyl,Moscow, Union of Soviet Socialist Republics

Jovanovich, J.University of Manitoba, Winnipeg, Manitoba, Canada

Kelly, N.Commission of the European Communities, Brussels

Kuramoto, A.Research Institute for Nuclear Medicine and Biology,

Hiroshima University Hospital, Hiroshima, Japan

Lee, T.R.University of St. Andrews, St. Andrews, Fife,

United Kingdom

Mettler, F.A-., Jr.University of New Mexico, Albuquerque,New Mexico, United States of America

Salo, A.Centre for Radiation and Nuclear Safety, Helsinki, Finland

Smales, E.Department of Health and Social Security, London,

United Kingdom

Steinhausler, F.University of Salzburg, Salzburg, Austria

Stepanenko, A.V.Academy of Sciences, Minsk,

Byelorussian Soviet Socialist Republic

Voloshchuk, V.V.Committee on the Rectification of the

Consequences of Chernobyl,Moscow, Russian Soviet Federated Socialist Republic

Waight, P.World Health Organization, Geneva

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Documents

THE INTERNATIONAL CHERNOBYL PROJECT · International Chernobyl Project described in the present Overview and monitored its implementation. The aims of The aims of the Project were