The Other Report on Chernobyl (TORCH)
An independent scientific evaluation of health and environmental effects 20
years after the nuclear disaster providing critical analysis of a recent report by
the International Atomic Energy Agency (IAEA) and the World Health
Organisation (WHO)
Ian Fairlie PhD, UK
David Sumner DPhil, UK
Afterword by
Professor Angelina Nyagu, Ukraine
Foreword by
Rebecca Harms, MEP, Germany
Commissioned by Rebecca Harms, MEP, Greens/EFA in the European
Parliament
Supported by the Altner-Combecher Foundation and the Hatzfeldt Foundation
Berlin, Brussels, London, Kyiv
April 2006
1
Acknowledgements
This report was financed by Rebecca Harms, MEP, of the Greens/EFA Party in the
European Parliament, the Altner-Combecher Foundation and the Hatzfeldt Foundation.
The publishers are grateful in particular to Herr Günter Altner, Frau Altner and Herr Graf
Hatzfeldt for their support.
------
The authors thank Dr M DeCort of DG-TREN of the European Commission for permission
to reproduce plates from the Atlas of Caesium Deposition on Europe after the Chernobyl
Accident (1998) EUR Report 16733. Office for Official Publications of the European
Communities, Luxembourg. The authors also thank Dr Y Demidchik for permission to
reproduce figure 4.2.
The authors thank Dr K Baverstock, Professor Y Dubrova, U Fink and Dr W Neumann for
their helpful comments on drafts of the report. The authors also thank Dr E Cardis, Dr GN
Kelly, Dr E Lyman, Professor A Nyagu, Dr T Ruff, M Schneider, J Simmonds and others
for their helpful information. They also thank Margit Göbel, Silke Malorny and Anna
Turmann for their expert administrative help.
Any errors, of course, remain the sole responsibility of the authors.
2
Table of Contents
Acknowledgements..............................................................................................................1
Foreword by Rebecca Harms..............................................................................................4
EXECUTIVE SUMMARY AND CONCLUSIONS.................................................................6
Chapter 1. Introduction......................................................................................................13
AIMS OF THE REPORT.......................................................................................................13
SCOPE AND LIMITATIONS...................................................................................................13
RADIATION AND RADIOACTIVITY.........................................................................................14
Uncertainty.................................................................................................................14
Difficulties with Epidemiology Studies.........................................................................15
Polarised Views on Radiation Risks...........................................................................15
RECOMMENDED READING LIST..........................................................................................17
Chapter 2. The Chernobyl Accident and Source Term......................................................18
THE ACCIDENT.................................................................................................................18
SOURCE TERM.................................................................................................................19
Reactor Inventory.......................................................................................................21
RELEASE ESTIMATES FOR MAIN NUCLIDES.........................................................................22
Estimates for Cs-137 and I-131..................................................................................23
The Question of Plate-Out..........................................................................................23
ANNEX 2A: EXCERPT FROM OECD/NEA (1995)................................................................25
ANNEX 2B. ORIGINAL TABLE REPRODUCED FROM SICH (1996).............................................26
ANNEX 2C. DERIVATION OF CS-137 AND I-131 SOURCE TERMS...........................................27
Chapter 3. Dispersion and Deposition of Chernobyl Fallout..............................................29
INTRODUCTION.................................................................................................................29
DEPOSITION DENSITY MEASUREMENTS..............................................................................30
Official Reactions........................................................................................................35
CS-137 FROM TEST BOMB FALLOUT..................................................................................35
CONTAMINATION LEVELS - WHAT DO THEY MEAN?...............................................................37
CS-137 CONTAMINATION..................................................................................................38
EFFECTS THROUGHOUT EUROPE.......................................................................................40
CONTINUING HIGH LEVELS OF CONTAMINATION...................................................................41
RESTRICTED REPORTING BY UNSCEAR (2000) AND IAEA/WHO (2005A, 2005B)..............42
ANNEX 3A. CHERNOBYL CONTAMINATION BY AREA IN EACH COUNTRY...................................44
ANNEX 3B. FUTURE EFFECTS FROM CHERNOBYL................................................................45
Chapter 4. Health Effects Resulting from the Chernobyl Accident.....................................46
INTRODUCTION.................................................................................................................46
(1) THYROID CANCER.......................................................................................................47
How many more thyroid cancers can we expect?......................................................49
Thyroid cancer in adults..............................................................................................50
3
Thyroid cancers outside Belarus, Ukraine and Russia...............................................51
(2) LEUKAEMIA.................................................................................................................52
Leukaemia in cleanup workers...................................................................................52
Leukaemia in residents of contaminated areas..........................................................52
Leukaemia in other European countries.....................................................................53
(3) OTHER SOLID CANCERS...............................................................................................54
Cancers in cleanup workers.......................................................................................54
Breast cancer in Belarus, Ukraine and Russia...........................................................55
Bladder and Kidney Cancer........................................................................................55
Cancer in other European countries...........................................................................55
(4) NON-CANCER EFFECTS................................................................................................55
(a) Cataract Induction.................................................................................................56
(b) Cardiovascular diseases.......................................................................................56
(5) HERITABLE EFFECTS....................................................................................................57
(6) MENTAL HEALTH AND PSYCHOSOCIAL EFFECTS.............................................................58
ANNEX 4. RADIATION DOSE UNITS.....................................................................................59
Chapter 5. Collective Doses..............................................................................................60
INTRODUCTION.................................................................................................................60
A. Collective Dose Estimates for Belarus, Ukraine and Russia..................................61
B. Collective Doses in the Rest of Europe..................................................................62
C. Collective Doses in the Rest of the World (excluding the whole of Europe)...........62
D. Global Collective Doses.........................................................................................63
COLLECTIVE DOSES FROM LONG-LIVED NUCLIDES..............................................................63
COMPARISON WITH OTHER RELEASES................................................................................64
ANNEX 5A. BENNETT'S STUDY..........................................................................................65
ANNEX 5B. COLLECTIVE DOSE ESTIMATES IN EUROPEAN COUNTRIES...................................66
Chapter 6. Predicted Excess Cancer Deaths.....................................................................67
PREDICTIONS FOR BELARUS, UKRAINE AND RUSSIA............................................................67
GLOBAL PREDICTIONS OF EXCESS CANCER DEATHS...........................................................67
Radiation Risk Estimates and DDREFs......................................................................68
Inappropriate Comparisons with Background Radiation.............................................69
ANNEX 6A. COLLECTIVE DOSE AND THE LINEAR NO-THRESHOLD THEORY............................70
ANNEX 6B. INAPPROPRIATE COMPARISONS WITH BACKGROUND RADIATION..........................71
Chapter 7. Conclusions......................................................................................................72
Afterword...........................................................................................................................75
References to Main Report................................................................................................80
Acronyms and Abbreviations.............................................................................................90
4
Foreword by Rebecca Harms
„There are two compelling reasons why this tragedy must not be forgotten. First, if we forget Chornobyl, we
increase the risk of more such technological and environmental disasters in the future. Second, more than
seven million of our fellow human beings do not have the luxury of forgetting. They are still suffering, every
day, as a result of what happened 14 years ago. Indeed, the legacy of Chernobyl will be with us, and with
our descendants, for generations to come."
Kofi Annan
UN Secretary General in April 2000
"We did not yet possess a system of imagination, analogies, words or experiences for the catastrophe of
Chernobyl."
Svetlana Alexiyevich
Writer from Belarus
In August 1986, four months after the Chernobyl disaster, Morris Rosen, head of the Division of
Nuclear Safety of the Vienna based International Atomic Energy Agency (IAEA), declared: "Even if
there was a Chernobyl type accident every year, I would still consider nuclear power an interesting
type of energy production".1 After a gigantic explosion and a ten day blazing fire had spread two
hundred times the amount of radioactivity of the combined releases of the Hiroshima and Nagasaki
bombs all over the planet, after the evacuation of over one hundred thousand people, the IAEA's
chief nuclear safety officer considered an annual repetition of such a catastrophe an acceptable
hypothesis. This man was the most powerful person in the IAEA on the issue of nuclear safety
between 1981 and 1996, when he retired from his position then as Assistant Director General for
Nuclear Safety. Breathtaking.
Rosen's post-Chernobyl declaration sheds a particular light on the mission statement of the IAEA,
which stipulates that the Agency "develops nuclear safety standards and, based on these
standards, promotes the achievement and maintenance of high levels of safety in applications of
nuclear energy, as well as the protection of human health and the environment against ionizing
radiation". Frightening.
When the IAEA in September 2005 released two reports on the environmental effects (coordinated
by the IAEA) and health impacts (coordinated by the World Health Organisation - WHO) of the
Chernobyl accident, numerous people and NGOs were suspicious about intentions and content.
The IAEA is not neutral. Its primary role, as defined on its website, is "to promote safe, secure and
peaceful nuclear technologies". The IAEA led interagency cooperation with the WHO is not a
coincidence. An 1959 agreement between both organisations stipulates: "Whenever either
organization proposes to initiate a program or activity on a subject in which the other organization
has or may have a substantial interest, the first party shall consult the other with a view to adjusting
the matter by mutual agreement." The term is well chosen: "adjusting the matter".
For the Swiss medical doctor Michel Fernex, the consequences are straight forward: "This
Agreement explains why the WHO action plan for Chernobyl, IPHECA2, launched as late as
5 years after the catastrophe, was designed by the IAEA, it explains why the proceedings of the
WHO Chernobyl Conference (Geneva 1995) were never published, and why the inter-agency UN
report on Chernobyl3 still indicates, against all evidence, that Chernobyl caused 32 deaths, 200
irradiated and 2,000 thyroid cancers (in children and teenagers only), those being the IAEA and
UNSCEAR4 figures, and not those of WHO and OCHA5."
1
Le Monde, 28 August 1986
2
International Programme on the Health Effects of the Chernobyl Accident
3
dated 6 February 2002
4
United Nations Scientific Committee on the Effects of Atomic Radiation
5
United Nations Office for the Coordination of Humanitarian Affairs
5
On 5 September 2005 an IAEA press release entitled "Chernobyl: The True Scale of the Accident",
stated: "A total of up to four thousand people could eventually die of radiation exposure from the
Chernobyl nuclear power plant (NPP) accident nearly 20 years ago, an international team of more
than 100 scientists has concluded."
The IAEA statement was widely disseminated by the international media and raised an outcry
amongst independent experts and environmental organisations that considered that the release
scandalously downplayed the true scale of the disaster. However a solid scientific critique was
missing.
I decided to commission an independent analysis of the IAEA/WHO reports in order to clarify the
science basis for the assertions. You are holding the result of the study, The Other Report on
Chernobyl or TORCH, by Ian Fairlie and David Sumner, in your hands. It becomes clear from
their conclusions that the IAEA had indeed issued a seriously misleading statement about the
WHO findings on health impact that forecasts, rather than 4,000, close to 9,000 excess cancer
deaths. However, other evaluations estimate the death toll from cancer alone to between 30,000
and 60,000, most of them outside the most intensely affected countries Ukraine, Belarus and
Russia. In fact, the TORCH report also shows that more radioactivity was released from the reactor
than previously thought and that more than half of the fallout came down in Europe outside the
former Soviet Republics.
The excellent Afterword from renowned Ukrainian expert Prof. Angelina Nyagu, President of the
Kiev based association "Physicians of Chernobyl", reveals a number of additional issues that were
not the focus of the main report but highlight the scale of the ongoing drama. Ukrainian experts
estimate, for example, that the economic damage to Ukraine will be $200 billion until 2015. In
comparison, Ukraine's GDP in 2001 was $37 billion. In 1992 Ukraine spent 15% of its State budget
dealing with the aftermath of Chernobyl. While the figure has dropped to 5% in recent years, there
are many issues that remain unresolved. Some of these are extremely urgent, including the fact
that close to 10,000 people continue to live in zones of compulsory evacuation.
The present report cannot make up for the 20 years of systematic downplaying, secrecy,
misinformation and misunderstanding of the effects of the Chernobyl catastrophe. But it does make
a significant contribution to the better understanding of what is at stake when the nuclear industry
and its lobby as well as some political leaders want us to agree to a new round of nuclear folly. It is
stunning to what extent the energy sector, in East and West, has never experienced its
Perestroïka, has never been exposed to Glasnost. It is the responsibility of political leaders to take
up the debate on energy policy and, beyond the commemorations of the 20th anniversary of what
will remain an ongoing disaster, guarantee a truly democratic decision making process that takes
into account the experiences from the past in order to design a sustainable energy future for all.
The aftermath of the Chernobyl disaster is far from mitigated. Not even on a technical level. The
conditions at the reactor site, in particular concerning spent fuel and waste management at the
other three Chernobyl units, represent significant additional risks to be solved under very difficult
radiological conditions. However, nuclear waste and contamination in many other places around
the world from activities often decades ago still await a costly solution. Nobody can guarantee that
another accident of Chernobyl dimensions or worse won't happen tomorrow. In most countries a
large majority of the people do not want any more nuclear power plants. It is about time that
industrial, economic and political leaders listen. No more Chernobyl.
6
EXECUTIVE SUMMARY AND CONCLUSIONS
On 26 April 2006, twenty years will have passed since the Chernobyl nuclear power plant
exploded, releasing large quantities of radioactive gases and particles throughout the
northern hemisphere. While the effects of the disaster remain apparent particularly in
Belarus, Ukraine and Russia, where millions of people are affected, Chernobyl's fallout
also seriously contaminated other areas of the world, especially Western Europe.
The Other Report on Chernobyl (TORCH) provides an independent scientific examina-
tion of available data on the release of radioactivity into the environment and subsequent
health-related effects of the Chernobyl accident. The Report also critically examines recent
official reports on the impact of the Chernobyl accident, in particular two reports by the "UN
Chernobyl Forum" released by the International Atomic Energy Agency (IAEA) and the
World Health Organisation (WHO) in September 20056, which have received considerable
attention by the international media.
Many uncertainties surround risk estimates from radiation exposures. The most
fundamental is that the effects of very low doses are uncertain. The current theory is that
the relationship between dose and detrimental effect is linear without threshold down to
zero dose. In other words, there is no safe level of radiation exposure. However the risk, at
low doses, may be supralinear, resulting in relatively higher risks, or sublinear, resulting in
relatively lower risks.
Another major source of uncertainty lies in the estimates of internal radiation doses, that is,
from nuclides, which are inhaled or ingested. These are important sources of the radiation
from Chernobyl's fallout. Uncertainties in internal radiation risks could be very large,
varying in magnitude from factors of 2 (up and down from the central estimate) in the most
favourable cases, to 10 or more in the least favourable cases for certain radionuclides.
The Accident
Early on April 26 1986, two explosions in Chernobyl unit 4 completely destroyed the
reactor. The explosions sent large clouds of radioactive gases and debris 7 - 9 kilometres
into the atmosphere. About 30% of the reactor's 190 tons of fuel was distributed over the
reactor building and surrounding areas and about 1-2% was ejected into the atmosphere.
The reactor's inventory of radioactive gases was released at this time. The subsequent
fire, fuelled by 1,700 tons of graphite moderator, lasted for eight days. This fire was the
principal reason for the extreme severity of the Chernobyl disaster.
How Much Radioactivity Was Released?
The World Health Organisation (WHO) has estimated that the total radioactivity from
Chernobyl was 200 times that of the combined releases from the atomic bombs dropped
on Hiroshima and Nagasaki. The amount of radioactivity released during a radiological
event, is called the ‘source term'. It is important because it is used to verify nuclide
6
IAEA/WHO Health Effects of the Chernobyl Accident and Special Health Care Programmes. Report of the
UN Chernobyl Forum Expert Group "Health" (EGH) Working draft[0], July 26 2005. IAEA/WHO
Environmental Consequences of the Chernobyl Accident and their Remediation. Report of the UN Chernobyl
Forum Expert Group "Environment" (EGE) Working draft[0], August 2005
7
depositions throughout the northern hemisphere. From these, collective doses and
predicted excess illnesses and fatalities can be estimated.
Of the cocktail of radionuclides that were released, the fission products iodine-131,
caesium-134 and caesium-137 have the most radiological significance. Iodine-131 with its
short radioactive half-life7 of eight days had great radiological impact in the short term
because of its doses to the thyroid. Caesium-134 (half-life of 2 years) and caesium-137
(half-life of 30 years) have the greater radiological impacts in the medium and long terms.
Relatively small amounts of caesium-134 now remain, but for the first two decades after
1986, it was an important contributor to doses.
Most of the other radionuclides will have completely decayed by now. Over the next few
decades, interest will continue to focus on caesium-137, with secondary attention on
strontium-90, which is more important in areas nearer Chernobyl. Over the longer term
(hundreds to thousands of years), the radionuclides of continuing interest will be the
activation products, including the isotopes of plutonium, neptunium and curium. However,
overall doses from these activation products are expected to remain low, compared with
the doses from caesium-137.
The authors have reassessed the percentages of the initial reactor inventories of caesium-
137 and iodine-131 which were released to the environment. They conclude that official
figures underestimate the amounts released by 15% (iodine-131) and 30% (caesium-137).
Dispersion and Deposition of Chernobyl Fallout
During the 10 day period of maximum releases from Chernobyl, volatile radionuclides were
continuously discharged and dispersed across many parts of Europe and later the entire
northern hemisphere. For example, relatively high fallout concentrations were measured at
Hiroshima in Japan, over 8,000 km from Chernobyl.
Extensive surveying of Chernobyl's caesium-137 contamination was carried out in the
1990s under the auspices of the European Commission. The largest concentrations of
volatile nuclides and fuel particles occurred in Belarus, Russia and Ukraine. But more than
half of the total quantity of Chernobyl's volatile inventory was deposited outside these
countries.
Russia, Belarus and Ukraine received the highest amounts of fallout while former
Yugoslavia, Finland, Sweden, Bulgaria, Norway, Rumania, Germany, Austria and
Poland each received more than one petabecquerel (1015 Bq or one million billion
becquerels) of caesium-137, a very large amount of radioactivity.8
In area terms, about 3,900,000 km2 of Europe was contaminated by caesium-137 (above
4,000 Bq/m2) which is 40% of the surface area of Europe. Curiously, this latter figure
does not appear to have been published and, certainly has never reached the public's
consciousness in Europe. Also 218,000 km2 or about 2.3% of Europe's surface area was
contaminated to higher levels (greater than 40,000 Bq/m2 Cs-1379). This is the area cited
by IAEA/WHO and UNSCEAR, which shows that they have been remarkably selective in
their reporting.
7
Half-life is the time it takes for half of a given amount of a radionuclide to decay.
8
Cf. the EU limit of 600 Bq per kg of caesium-137 in dairy foods
9
Compared with contamination levels in the Chernobyl exclusion zone > 555,000 Bq/m2.
8
In terms of their surface areas, Belarus (22% of its land area) and Austria (13%) were
most affected by higher levels of contamination. Other countries were seriously affected;
for example, more than 5% of Ukraine, Finland and Sweden were contaminated to high
levels (> 40,000 Bq/m2 caesium-137). More than 80% of Moldova, the European part of
Turkey, Slovenia, Switzerland, Austria and the Slovak Republic were contaminated to
lower levels (> 4,000 Bq/m2 caesium-137). And 44% of Germany and 34% of the UK were
similarly affected.
The IAEA/WHO reports do not mention these comprehensive datasets on European
contamination by the European Commission. No explanation is given for this omission.
Moreover, the IAEA/WHO reports do not discuss deposition and radiation doses in any
country apart from Belarus, Ukraine and Russia. Although heavy depositions certainly
occurred there, the omission of any examination of Chernobyl fallout in the rest of Europe
and the northern hemisphere is questionable.
Restrictions on Food Still in Place
In many countries, restriction orders remain in place on the production, transportation and
consumption of food still contaminated by Chernobyl fallout.
• In the United Kingdom restrictions remain in place on 374 farms covering 750 km2 and
200,000 sheep.
• In parts of Sweden and Finland, as regards stock animals, including reindeer, in natural
and near-natural environments.
• In certain regions of Germany, Austria, Italy, Sweden, Finland, Lithuania and Poland
wild game (including boar and deer), wild mushrooms, berries and carnivore fish from
lakes reach levels of several thousand Bq per kg of caesium-137.
• In Germany, caesium-137 levels in wild boar muscle reached 40,000 Bq/kg. The
average level is 6,800 Bq/kg, more than ten times the EU limit of 600 Bq/kg.
The European Commission does not expect any change soon. It has stated10:
"The restrictions on certain foodstuffs from certain Member States must therefore
continue to be maintained for many years to come." (emphases added)
The Health Impacts - So Far...
The immediate health impact of the Chernobyl accident was acute radiation sickness in
237 emergency workers, of whom 28 died in 1986 and a further 19 died between 1987 and
2004. The long-term consequences of the accident remain uncertain. Exposure to ionising
radiation can induce cancer in almost every organ in the body. However, the time interval
between the exposure to radiation and the appearance of cancer can be 50 to 60 years or
more. The total number of cancer deaths from Chernobyl most likely will never be fully
10
Andris Piebalgs, European Commission, written answer to Question P-1234/05DE by MEP Rebecca
Harms dated April 4, 2005
9
known. However the TORCH Report makes predictions of the numbers of excess cancer
deaths from published collective doses to affected populations.
Thyroid Cancer
Up to 2005, about 4,000 cases of thyroid cancer occurred in Belarus, Ukraine and Russia
in those aged under 18 at the time of the accident. The younger the person exposed, the
greater the subsequent risk of developing thyroid cancer.
Thyroid cancer is induced by exposures to radioactive iodine. It is estimated that more
than half the iodine-131 from Chernobyl was deposited outside the former Soviet Union.
Possible increases in thyroid cancer have been reported in the Czech Republic and the
UK, but more research is needed to evaluate thyroid cancer incidences in Western
Europe.
Depending on the risk model used, estimates of future excess cases of thyroid cancer
range between 18,000 and 66,000 in Belarus alone. Of course, thyroid cancers are also
expected to occur in Ukraine and Russia. The lower estimate assumes a constant relative
risk for 40 years after exposure; the higher assumes a constant relative risk over the whole
of life. Recent evidence from the Japanese atomic bomb survivors suggests that the latter
risk projection may be more realistic.
Leukaemia
The evidence for increased leukaemia is less clear. Some evidence exists of increased
leukaemia incidence in Russian cleanup workers and residents of highly contaminated
areas in Ukraine. Some studies appear to show an increased rate of childhood leukaemia
from Chernobyl fallout in West Germany, Greece and Belarus.
Other Solid Cancers
Most solid cancers have long periods between exposure and appearance of between
20 and 60 years. Now, 20 years after the accident, an average 40% increased incidence in
solid cancer has already been observed in Belarus with the most pronounced increase in
the most contaminated regions. The 2005 IAEA/WHO reports acknowledge preliminary
evidence of an increase in the incidence of pre-menopausal breast cancer among women
exposed at ages lower than 45 years.
Non-Cancer Effects
Two non-cancer effects, cataract induction and cardiovascular diseases, are well
documented with clear evidence of a Chernobyl connection. Lens changes related to
radiation have been observed in children and young people aged between 5 and 17 living
in the area around Chernobyl. A large study of Chernobyl emergency workers showed a
significantly increased risk of cardiovascular disease.
Heritable Effects
It is well known that radiation can damage genes and chromosomes. However the
relationship between genetic changes and the development of future disease is complex
and the relevance of such damage to future risk is often unclear. On the other hand, a
number of recent studies have examined genetic damage in those exposed to radiation
from the Chernobyl accident. Studies in Belarus have suggested a twofold increase in the
10
germline minisatellite mutation11 rate. Analysis of a cohort of irradiated families from
Ukraine confirmed these findings. However the clinical symptoms which may result from
these changes remain unclear.
Mental Health and Psychosocial Effects
While seeming to downplay other effects, the recent IAEA/WHO reports clearly recognise
the vast mental, psychological and central nervous system effects of the Chernobyl
disaster: "The mental health impact of Chernobyl is the largest public health problem
caused by the accident to date. The magnitude and scope of the disaster, the size of the
affected population, and the long-term consequences make it, by far, the worst industrial
disaster on record."
The origins of these psychosocial effects are complex, and are related to several factors,
including anxiety about the possible effects of radiation, changes in lifestyle - particularly
diet, alcohol and tobacco - victimisation, leading to a sense of social exclusion, and stress
associated with evacuation and resettlement. It is therefore difficult to state exactly how
much of these symptoms are directly related to Chernobyl related radiation exposures.
Collective Doses
Radiation exposures are mainly measured in two ways: individual doses and collective
doses. Individual doses are measured or calculated per person and collective doses are
the sum of individual doses to all exposed persons in a defined area, for example a
workforce, a country, a region, or indeed the world. The use of collective doses is
particularly relevant in cases where large population groups are exposed to relatively low
individual doses over long periods of time. The estimation of collective doses is an
indispensable tool to evaluate potential future health effects of radiation.
It is necessary to identify clearly the time periods over which a collective dose is estimated.
For example, the exposed populations in Belarus, Ukraine and Russia received
approximately one third of a 70-year collective dose in the first year after Chernobyl.
Approximately another third was received in the next nine years (ie 1987 to 1996), and
the remaining third will be received approximately between 1997 and 2056.
The IAEA/WHO reports estimate the collective dose to Belarus, Ukraine and Russia is
55,000 person sieverts, which is the lower end of a range of evaluations reaching over
300,000 person sieverts. The IAEA/WHO restrict their time estimate to 2006, and fail to
present estimates for European and worldwide collective doses: these are significant
limitations.
The most credible published estimate for the total worldwide collective dose from
Chernobyl fallout is 600,000 person sieverts making Chernobyl the worst nuclear
accident by a considerable margin. Of this total collective dose, approximately:
- 36% is to the populations of Belarus, Ukraine and Russia
- 53% is to the population of the rest of Europe
- 11% is to the population of the rest of the world12
11
Human germline mutations are those that affect sequences of repeated DNA and thus the genes of the
germinal or reproductive cells (the egg and the sperm).
11
Estimated Future Excess Cancer Deaths
Excess cancer deaths can be estimated from published collective doses. For Belarus,
Ukraine and Russia, published estimates range between 4,000 and 22,000 excess cancer
deaths. For the world, published estimates range between 14,000 and 30,000. These
estimates depend heavily on the risk factor used: different scientists use different factors.
Recent studies indicate that currently-used risks from low doses at low dose rates may
need to be increased.
The IAEA, in its 5 September 2005 press release "Chernobyl: The True Scale of the
Accident" stated that up to 4,000 people could eventually die of radiation exposure from
Chernobyl. This figure has been quoted extensively by the world media. However the
statement is misleading, as the figure calculated in the IAEA/WHO report is actually 9,000
fatalities.
Depending on the risk factor used (ie the risk of fatal cancer per person sievert), the
TORCH Report estimates that the worldwide collective dose of 600,000 person sieverts
will result in 30,000 to 60,000 excess cancer deaths, 7 to 15 times the figure release in
the IAEA's press statement.
Conclusions
The full effects of the Chernobyl accident will most certainly never be known. However,
20 years after the disaster, it is clear that they are far greater than implied by official
estimates. Our overall conclusion is that the unprecedented extent of the disaster and its
long-term global environmental, health and socio-economic consequences should be fully
acknowledged and taken into account by governments when considering their energy
policies.
In summary, the main conclusions of the Report are:
• about 30,000 to 60,000 excess cancer deaths are predicted, 7 to 15 times greater
than the figure of 4,000 in the IAEA press release
• predictions of excess cancer deaths strongly depend on the risk factor used
• predicted excess cases of thyroid cancer range between 18,000 and 66,000 in
Belarus alone depending on the risk projection model
12
It is remarkable that the author of these evaluations published in 1995 and 1996 (see hereunder), that
have not found their way into the 2005 IAEA/WHO studies, was also the Chairman of the Chernobyl Forum
that coordinated the 2005 IAEA/WHO studies.
• Bennett B (1995) Exposures from Worldwide Releases of Radionuclides. In Proceedings of an
International Atomic Energy Agency Symposium on the Environmental Impact of Radioactive Releases.
Vienna, May 1995. IAEA-SM-339/185
• Bennett B (1996) Assessment by UNSCEAR of Worldwide Doses from the Chernobyl Accident in
Proceedings of an IAEA Conference One Decade after Chernobyl: Summing up the Consequences of the
Accident, Vienna, 8-12 April 1996.
12
• other solid cancers with long latency periods are beginning to appear 20 years after
the accident
• Belarus, Ukraine and Russia were heavily contaminated, but more than half of
Chernobyl's fallout was deposited outside these countries
• fallout from Chernobyl contaminated about 40% of Europe's surface area
• the most credible published collective dose is estimated to be about 600,000 person
sievert, more than 10 times greater than the 55,000 estimate by the IAEA/WHO in
2005
• about 2/3rds of Chernobyl's collective dose was distributed to populations outside
Belarus, Ukraine and Russia, especially to western Europe
• caesium-137 released from Chernobyl is estimated to be about a third higher than
official estimates
Recent IAEA/WHO studies
Our verdict on the two recent IAEA/WHO studies on Chernobyl's health and environmental
effects respectively is mixed. On the one hand, we recognise that the reports contain
comprehensive examinations of Chernobyl's effects in Belarus, Ukraine and Russia. On
the other hand, the reports are silent on Chernobyl's effects outside these countries.
However most of Chernobyl's fallout fell outside Belarus, Ukraine and Russia. Collective
doses from Chernobyl's fallout to populations in the rest of the world, especially in western
Europe, are twice those to populations in Belarus, Ukraine and Russia. This means that
these populations will suffer twice as many predicted excess cancer deaths, as the
populations in Belarus, Ukraine and Russia.
The failure to examine Chernobyl's effects in the other countries does not seem to lie with
the scientific teams but within the policy-making bodies of IAEA and WHO. In order to
rectify this omission, we recommend that the WHO, independently of the IAEA, should
commission a report to examine Chernobyl's fallout, collective doses and effects in the rest
of the world, particularly in western Europe.
___________________________________________
13
Chapter 1. Introduction
1. On April 26 2006, 20 years will have passed since the world's worst industrial
accident. The disaster is now a generation away, yet the word ‘Chernobyl' still resonates
throughout the world, and its effects are still apparent particularly in Belarus, Ukraine and
Russia, the three countries most affected by the disaster. As this report will show,
Chernobyl fallout also seriously contaminated other areas of the world. In the United
Kingdom, for example, over 2,500 kilometers from Chernobyl, more than 360 farms are
still subject to restrictions because of Chernobyl contamination. Ultimately, fallout from
Chernobyl was distributed over the entire northern hemisphere.
Aims of the Report
2. The report aims to provide an impartial scientific examination of mainly health-
related effects of Chernobyl, and to critically examine recent official reports on Chernobyl
from a European point of view. Although the subject matter of the report is clearly
scientific, we have tried to write the report in plain English ensuring we explain our terms
and avoid jargon, in order to make the report more accessible to members of the public. In
some cases, the complexity of the matter may have defeated our intentions, but we have
tried to keep the report simple and understandable.
3. The five main chapters of the report cover source term matters, dispersal and
deposition issues, health effects, collective doses and predicted excess cancer deaths.
Chapter 2 discusses official estimates of the total amount of radioactivity released by the
explosions and subsequent fire at Chernobyl. This chapter derives our own estimates of
the releases of the most important nuclides, Cs-137 and I-131, which are greater than
official estimates. Chapter 3 illustrates the extremely wide diffusion of Chernobyl fallout
over Europe and the northern hemisphere. Chapter 4 discusses the incidences of thyroid
cancer, leukaemias, solid cancers and non-cancer effects appearing in Belarus, Ukraine
and Russia and elsewhere. Chapter 5 estimates collective dose estimates world-wide, and
Chapter 6 predicts excess cancer deaths from Chernobyl fallout.
Scope and Limitations
4. Several hundred official and unofficial reports and books have been written about
Chernobyl. Web searches for the word "Chernobyl" reveal over 38,000 scientific citations
in Google Scholar and about 3,000 peer-reviewed articles in scientific journals in PubMed
(http://www.ncbi.nlm.nih.gov/entrez/). Therefore it was necessary to focus on what to us
were the most important issues: source term, dispersal and deposition, health effects,
collective doses and predicted excess cancer deaths. Unfortunately, the time available did
not permit us to examine the socio-economic effects of the disaster, the ecologic effects
(see Moller and Mousseaux, 2006; Moller et al, 2005) and the present state of the
destroyed reactor at Chernobyl and its sarcophagus. These serious subjects deserve
detailed examination in other reports.
5. Our emphasis on a scientific approach means that we have relied mainly on
scientific articles published in peer-reviewed journals. Mainly but not exclusively: we have
also referenced articles from non-published sources including the websites of a number of
international research institutes. Our main criteria for inclusion were whether the authors
had approached their subject critically and had been scientifically rigorous with their
14
evidence. Inevitably, there remains an element of subjectivity in our choice of references,
and there may well be articles which have escaped our attention.
6. In addition, our work has been inevitably limited by the difficulties in gaining access
to, and translating, many scientific reports written in Ukrainian and Russian. These
constraints inhibit a full understanding of the impacts of Chernobyl, and we draw attention
to this difficulty and to the need for it to be tackled at an official level. Our research has
also been limited by the failure to publish their findings on cancer incidences - for example,
the ECLIS programme on childhood leukaemias in European countries. Also, our report is
a ‘snapshot' of a moving scene: much Chernobyl-related research is still underway and
new findings may well change our understanding of radiation's effects, just as they have in
the past 20 years.
Radiation and Radioactivity
7. Radiation and radioactivity (including their risks, doses, biology and epidemiology)
are complex matters which are not easily understood. This brief report does not discuss
radiation and radioactivity in detail as this would require a book in itself. However we do
provide a note on radiation dose units (see Annex 4), a list of acronyms (see end of report)
and a reading list of the more critical articles and books for those interested in learning
more about radiation (see end of this chapter). Perhaps the most recent and accessible
introduction to radiation and radioactivity in English is the report of the UK Government's
Committee Examining the Radiation Risks of Internal Emitters (CERRIE, 2004) which can
be downloaded from www.cerrie.org. The CERRIE Committee contained independent
scientists and representatives of environmental organisations as well as scientists from
official agencies: its report therefore contains a spectrum of views.
8. Although we do not discuss radiation per se, we should mention some ancillary
matters to radiation, including uncertainty, the limitations of epidemiology and the wide
disparity of views on radiation risks.
Uncertainty
9. Many uncertainties surround risk estimates from radiation exposures. The most
fundamental is that we are unsure of the dose-response relationship at very low doses.
The current theory is that this relationship is linear without threshold down to zero dose
(Brenner et al, 2003). However it may be supralinear resulting in higher risks, or sublinear
resulting in lower risks. See discussion in Annex 6A. The result is that risk estimates from
exposures to radiation inevitably contain uncertainties. This does not prevent such
estimates being made, but they have to be treated with caution.
10. Another main source of uncertainty lies in our estimates of internal radiation doses,
that is, from nuclides which are inhaled or ingested. These are an important source of the
radiation impact resulting from Chernobyl fallout. This issue was comprehensively
examined in the 2004 CERRIE report which concluded that uncertainties in the internal
dose coefficients13 for some nuclides could be very large. The uncertainties in internal
radiation risks could also be large, varying in magnitude from factors of 2 (up and down
from the central estimate) in the most favourable cases, to 10 or more in the least
favourable cases. These uncertainties depended on factors such as the type of
radionuclide, its chemical form, the mode of exposure and the body organ under
13
a dose coefficient expresses the dose given by one decay of a radionuclide in Sv per Bq
15
consideration. Under some circumstances, equivalent doses could be substantially greater
or smaller than current best estimates; therefore great care has to be taken when judging
the risks of radioactive sources inside the body.
11. The CERRIE report also advised that a precautionary approach should be used. In
our view, this means that we should err on the side of caution - in other words, we should
be aware that doses and risks might be greater than those presently used.
Difficulties with Epidemiology Studies
12. For a number of reasons, epidemiology studies are a blunt tool for discovering
whether adverse effects result from particular exposures. One reason is that many
methodological difficulties can exist with epidemiology studies. For example, much
epidemiology data on Chernobyl is descriptive (or ecological) with poor case identification,
non-uniform registration, variable or uncertain diagnostic criteria and uncertainties in the
uniformity of data collation. Predicted excess deaths are often uncertain due to
confounding factors, competing causes of death and different risk projection models. For
example, one difficulty in interpreting Chernobyl mortality studies is the large recent
decrease in average lifespan in all three countries occurring in all areas not just the
contaminated ones.
13. Only very large, expensive and lengthy epidemiology studies are able to reveal
effects where the signal (added cancers) is weak, and the noise (large numbers of natural
cancers) is strong. Often, we see instead many small studies each showing perhaps a few
extra cases which prove little. Meta-studies which group together small studies in order to
strengthen their statistical significance are a solution, but few have been carried out so far.
In addition, various agents can produce significant bias in studies. For example, smoking
and alcohol cause major increases in overall mortality and morbidity, and in cancer and
cardiovascular disease. Another problem is establishing causality. This often requires
estimating doses in order to show a dose - effect relationship. However, as shown by the
CERRIE report, there are often large uncertainties in estimating doses - especially from
internal radiation sources which are important in Chernobyl exposures.
14. The conclusion is that there needs to be more awareness of the many factors that
have to be taken into account when considering epidemiology studies. In particular, the
results of epidemiology studies need to be interpreted with care.
Polarised Views on Radiation Risks
15. Widely different views exist on radiation risks between the authors of many official
publications and members of the public especially in Belarus, Ukraine and Russia. In
addition, the contents of many unofficial websites reveal a lack of knowledge about
radiation and its effects among many members of the public, often coupled with an
apparent fear of radiation. It's also apparent that a substantial number of people in
Belarus, Ukraine and Russia - as in most of the EU Member States - are suspicious of
Governments and official agencies with pro-nuclear policies, seeing them as having an
interest in minimising the effects of radiation and controlling public perceptions about the
risks. They are therefore often hostile towards official publications on radiation risks whose
findings, in their view, do not match their own experiences.
16. Many unofficial accounts have criticised official reports on the health effects from
Chernobyl, in particular for their reluctance to acknowledge the existence of increased
16
effects and their practice of denying links between such increases and radiation from the
accident. Notably, during the IAEA/WHO Conference on Chernobyl in Vienna in
September 2005, officials from health ministries and academic institutions in Belarus and
Ukraine spoke out against the refusals of their Governments and international agencies to
recognise what was, in their view, the true scale of Chernobyl's effects.
17. Outspoken criticisms have been made by Malko (1998b) who has accused the
international radiation protection community of being unable to objectively assess the
health consequences of the accident. He has stated that the international radiation
protection community had attempted to play down the consequences from the beginning.
He gave numerous examples of official refusals to accept the existence of data from their
own health ministries and of their far-fetched explanations for observed effects. Perhaps
the most disheartening example was the WHO's initial explanation in 1992 for the large
increases in childhood thyroid cancer in Belarus. These were allegedly due to (a) the
administration of prophylactic iodine to children after the accident and (b) nitrates in food
brought into the country from Asia (Nucleonics Week, 1992).
18. Some agencies have dramatically changed their views on radiation's effects,
without discussing the reasons for doing so. One example is the decision by UNSCEAR
after about 1998 not to discuss global collective doses from Chernobyl - see chapter 5. In
addition, some Governments and official agencies have refused to recognise the data and
reports by other official agencies. The Director General of the IAEA, Mr Elbaradei
highlighted this when he stated (IAEA/WHO, 2005b)
"...a lack of trust still prevails ... due in part to contradictory data and reports on the
precise environmental and health impacts of the accident, among national
authorities as well as among the relevant international organizations"
19. One should tread warily in this battleground of views and values. Nevertheless, it is
worth pointing out that, while many official reports contain equivocations, omissions,
misleading language and understatements, others are more forthright and transparent. In
our experience, a significant minority of scientists working in official international and
national agencies do not necessarily agree with the downplaying of radiation effects. In
other words, it would be unwise to reject all official reports, as they sometimes contain
valuable information and insights. What are needed instead are critical and discriminating
examinations of official reports. We have attempted to do this here, while avoiding both the
understatements in official reports and the discussions of effects clearly not due to
radiation in unofficial reports.
17
Recommended Reading List
Caufield C (1990) Multiple Exposures: Chronicles of the Radiation Age. Penguin Books.
London UK
CERRIE (2004) Committee Examining the Radiation Risks of Internal Emitters
www.cerrie.org
Gofman JW (1981) Radiation and Human Health. A Comprehensive Investigation of the
Evidence Relating Low-level Radiation to Cancer and Other Diseases. Sierra Club Books.
San Francisco
Greenberg M (1991) The Evolution of Attitudes to the Human Hazards of Ionising
Radiation and to its Investigators. Am J of Industrial Medicine Vol 20 pp 717-721
Greene G (1999) The Woman Who Knew Too Much. University of Michigan Press. Ann
Arbor, MI, US
Lambert B (1990) How Safe is Safe? Radiation Controversies Explained. Unwin. London
UK (Out of print but copies may be available in libraries. A good introduction but now out of
date.)
Proctor RN (1995) Cancer Wars: How Politics Shapes What We Know and Don't Know
about Radiation. Basic Books. New York, NY, US
Rose G (1991) Environmental Health: Problems and Prospects. J of Royal College of
Physicians of London Vol 25 No 1, pp 48-52
Stewart AM (1991) Evaluation of Delayed Effects of Ionising Radiation: an Historical
Perspective. Am J of Industrial Medicine Vol 20 pp 805-810
Sumner DS, Watson D and Wheldon T (1994) Radiation Risks. Tarragon Press. (Out of
print but copies may be available in libraries. A good introduction but now out of date.)
US EPA website contains a relatively unbiased but basic description of radiation and its
effects http://www.epa.gov/radiation/understand/index.html
18
Chapter 2. The Chernobyl Accident and Source Term
The Accident
1. In April 1986, the world's worst industrial accident occurred at the Chernobyl nuclear
power plant in Ukraine. The IAEA (1996) has described it as the "foremost nuclear
catastrophe in human history" which resulted in the "largest regional release of
radionuclides into the atmosphere." WHO (IPHECA, 1995) has estimated that, although
different radionuclides were released, the total radioactivity of the material from Chernobyl
was 200 times that of the combined releases from the atomic bombs dropped on
Hiroshima and Nagasaki. The disaster not only resulted in an unprecedented release of
radioactivity but also a series of unpredicted and serious consequences for the public and
the environment.
2. Early on April 26, an explosion occurred in Chernobyl reactor 4 followed moments later
by a second explosion. The explosions completely destroyed the reactor, sheared all
pressure tubes and water coolant channels, and dislodged the upper biological shield
weighing 1,400 tonnes. The resulting damage is shown in Figure 2.1. The explosions sent
a large cloud of radioactive fission products and debris from the core and reactor 7-9
kilometres into the atmosphere (UNSCEAR, 1988). About 30% of the reactor's fuel was
sprayed over the reactor building and surrounding areas and about 1-2% was ejected into
the atmosphere. Most of the reactor's inventory of radioactive gases was released at this
time.
Figure 2.1 Cross-section view of Chernobyl Unit 4 reactor
3. Worse was to follow. About a day later, combustible gases from the disrupted core
caught fire producing flames that reached 50 m (UNSCEAR, 2000) above the reactor. This
19
ignited the graphite moderator containing 1,700 tonnes (Hohenemser, 1988) of carbon
which subsequently burned for 8 days. As explained in the OECD/NEA (1995) account
(see Annex 2A), the long-lasting graphite fire was the main reason for the extreme severity
of the Chernobyl disaster. The graphite fire ceased when all the carbon had been burned.
Revealingly, the phrase "graphite fire" does not appear in the UNSCEAR (2000) and
IAEA/WHO (2005a and 2005b) reports.
4. Much of the heat generated by the graphite fire, by radioactive decay, and possibly by
continuing fission in the remaining fuel was retained by the graphite mass. As a result,
temperatures in the destroyed core rose to 2,500°C according to analyses of dispersed
fuel particles by Devell et al (1986)14. These temperatures led to the melting of the fuel
remaining in the stricken reactor (metallic uranium melts at 1130°C; zirconium at 1850°C),
the total release of gaseous nuclides and the vaporisation, to varying degrees, of volatile
and less volatile nuclides. After vaporisation, it is assumed that some plating out occurred
on cooler parts of the shattered reactor and its debris: much uncertainty surrounds the
fractions of nuclides which condensed in this way.
5. After about 9 days, the temperature of the molten fuel rose sufficiently high to melt the
reactor's lower biological shield allowing the remaining molten fuel to flow into
subterranean chambers beneath the reactor. Here the fuel cooled and solidified into lava-
like formations which remain today. Many reports state that this evacuation is the reason
for the significant reduction in radionuclide emissions after the tenth day.
6. Nuclide emissions continued sporadically for a further 20 to 30 days but on a much
reduced scale. At the end, the reactor core contained neither fuel nor graphite moderator.
During the fire, many tonnes of borated lead and other materials were dropped by
helicopter into the reactor in an attempt to extinguish the graphite fire but it appears little
reached its target: most fell to one side (Sich, 1996). See figure 2.1. Annex 2A contains a
technical description of the disaster by the OECD/NEA (1995) which reveals the serious
predicaments resulting from the catastrophic events of April/May 1986.
Source Term
7. Much debate has surrounded the magnitude of the Chernobyl "source term," that is, the
amount of radioactivity released from the Chernobyl disaster. Although many reports have
been written on Chernobyl's radioactive releases, unfortunately they often raise as many
questions as answers. The source term is important because it can be used to verify
nuclide depositions throughout Belarus, Ukraine, Russia, the rest of Europe15 and the
northern hemisphere. From these, collective doses and predicted excess deaths may be
estimated.
8. Source terms may be estimated in two main ways
(i) The first is to use computer programs which model the atmospheric dispersal of
pollutants. Fallouts are averaged over blocks of territory and are integrated over
space and time. Early efforts at assessing radioactivity source terms using these
models produced very low estimates. This was partly because the blocks used were
too large in space and time, and partly because rainfall was very localized, so
14
Devell et al collected and analysed radioactive fuel particles by electron microscopy. They concluded from
their form and composition that the temperature in at least part of the reactor core reached ~2,500°C.
15
"Europe" has a slightly elastic geographical extent. In this report, Europe extends eastwards to the Ural
mountains, that is, it includes some of Russia, all of Ukraine, and all of Belarus.
20
average deposition densities over large areas were inaccurate. Later, more
sophisticated attempts were made using extensive gamma measurements and
mapping techniques with satellite Geographic Information Systems (European
Commission, 1998).
(ii) The second is to estimate the amounts of fission and activation products in the
reactor before the accident by using computer programs (such as FISPIN,
ORIGEN2, etc) which calculate fuel isotope inventories in reactors. The source term
is the difference between the reactor fuel's isotope inventory and the estimated
amounts of nuclides in the fuel remaining beneath or nearby the reactor.
Both methods have their drawbacks, particularly their use of questionable assumptions,
and both produce estimates with significant uncertainties. The second method produces
more realistic estimates and is perhaps burdened with fewer uncertainties.
9. The source term was not used in estimating doses to the affected populations in the
three former Soviet republics of Belarus, Ukraine and Russia: these were derived from
measured nuclide concentrations and dose reconstructions. Here, measured
concentrations were used with external and internal dose factors16 to estimate doses over
various time periods. This method has been criticised because of the lack of data on the
habits and diets of local populations: these data are important in assessing internal doses
from ingestion and inhalation of nuclides which are responsible for about half of the
radiation dose to inhabitants of heavily contaminated areas.
10. In the early years after Chernobyl, large uncertainties existed in initial estimates of the
fuel inventory and the amounts which remained, due to the inaccuracy and inadequacy of
the Soviet data provided at the time. In subsequent years, later estimates were made
(reviewed by Khan, 1990) using the second of the above methods. Ten years later,
attempts were made to harmonise estimates and develop a consensus view on the source
term (see Devell et al, 1995), which were only partially successful. At the same time,
reports by Sich (1994, 1994a, 1996) and Borodin and Sich (1996) gave additional
information on the fate of the fuel in the stricken reactor.
11. In 2000, UNSCEAR estimated that the total radioactive material released from
Chernobyl was 12 x 1018 becquerels (Bq) 17 including 6.5 x 1018 Bq of noble gases, mainly
krypton and xenon (12 x 1018 means 12 followed by 18 zeroes). According to UNSCEAR
(2000), 100% of gases, and 20 - 60% of volatile radionuclides, were released into the
atmosphere and carried for large distances. In addition, ~30% of the reactor's fuel was
ejected to areas around the reactor during the initial explosions and ~1 - 2% of the fuel
was more widely dispersed.
12. UNSCEAR (2000) did not discuss a number of studies - see table 2.2 - which cited
larger releases of important nuclides. The UNSCEAR (2000) conclusions were
subsequently reiterated in the WHO/IAEA (2005a) report without qualification or
discussion. In our view, there is no up-to-date critical discussion of the Chernobyl source
term that takes these factors into account. The present report tries to fill this gap and, in
particular, attempts to estimate the amounts of Cs-137 and I-131 released from Chernobyl.
16
which relate the absorbed dose in Sv to the degree of land contamination
17
the amount of a radionuclide is expressed in terms of its 'activity', that is, the number of spontaneous
nuclear disintegrations per second releasing radiation. Its unit is the becquerel (Bq). 1 Bq = 1 disintegration
per second.
21
Reactor Inventory
13. The reactor contained about 190 tonnes of nuclear fuel, 1,700 tonnes of graphite
moderator, and a very large volume of cooling water. The fuel elements mainly consisted
of mainly (>95%) uranium oxide. The reactor had been operating since 1983 and its fuel
had an average burnup of 11 GWdays per tonne. Therefore it contained considerable
quantities of fission products (eg caesium-137) and activation products (eg plutonium 239).
The explosions ejected about a third of the fuel, mostly to nearby areas; the continuing
graphite fire resulted in much wider releases of fission and activation products.
14. The fission products iodine-131, caesium-134 and caesium-137 have the most
radiological significance. Iodine-131 with its short radioactive half-life of 8 days had the
greater radiological impact in the short term because of its doses to thyroid. Caesium-134
(half-life = 2 years) and caesium-137 (half-life = 30 years) have the greater radiological
impacts in the medium and long terms. Very small amounts of Cs-134 now remain but for
the first two decades after 1986, it was an important contributor to doses because of its
relatively high dose coefficient18. Although strontium-90 also has a relatively long half-life
of 29 years and a high dose coefficient, measurements indicate that relatively little (~5%)
was released as it is less volatile. Most was deposited within 100 km or so of the reactor.
Also relevant are tellerium-132 (half-life = 3.3 days) as the parent of I-132 (half-life = 2.3
hours), and Te-129m (half-life = 33.6 days) as the parent of I-129 (half-life = 16 million
years).
15. The latest official estimates (UNSCEAR, 2000; IAEA/WHO, 2005b) of initial nuclide
inventories and activities released for the most relevant nuclides are set out in table 2.1.
The percentages released were omitted in the official reports but they have been
calculated (by dividing each nuclide's release by its initial inventory) and are presented in
the final column. Note that many of the official figures are qualified by the tilde sign "~",
meaning "approximately". Percentage releases are discussed further in paragraphs 19 and
20 below.
16. Some tables in this report contain greyed columns or cells. These contain data or
estimates prepared by this report. Normal unshaded columns contain data or estimates
from other reports.
Table 2.1 Initial nuclide inventories and amounts released for key nuclides released
from Chernobyl PBq = 1015 Bq
Radio
nuclide Half-life Core Inventory on April 26
1986 - PBq Activity Released -PBq Estimated Percentage
Released
INERT GASES
Kr-85 10.72 a 33 33 100
Xe-133 5.25 d 6,500 6,500 100
VOLATILE ELEMENTS
Te-129m 33.6 d 1040 240 23
Te-132 3.26 d 4200 ~1,150 ~27
I-129 15,700,000
a 8.1 x 10
-5
~8 x 10-5 ~50
I-131 8.04 d 3180 ~1,760 ~56
I-133 20.8 h 6700 2,500 37
Cs-134 2.06 a 150 ~54 ~36
Cs-136 13.1 d 110 36 33
Cs-137 30.0 a 260 ~85 ~33
ELEMENTS WITH INTERMEDIATE VOLATILITY
Sr-89 50.5 d 3960 ~115 ~3
Sr-90 29.12 a 220 ~10 ~4.5
Ru-103 39.3 d 4810 >168 >3.5
Ru-106 368 d 850 >73 >8.6
Ba-140 12.7 d 4800 240 5
18
ie high values of Sv per Bq (delivering high radiation doses to persons who inhale or ingest the nuclide)
22
Radio
nuclide Half-life Core Inventory on April 26
1986 - PBq Activity Released -PBq Estimated Percentage
Released
REFRACTORY ELEMENTS (incl fuel fragments***)
Zr-95 64.0 d 4810 196 4
Mo-99 2.75 d 5550 > 168 >3
Ce-141 32.5 d 5550 196 3.5
Ce-144 284 d 3920 ~ 116 ~3
Np-239 2.35 d 58,100 945 1.6
Pu-238 87.74 a 0.93 0.035 3.7
Pu-239 24,065 a 0.96 0.03 3
Pu-240 6,537 a 1.5 0.042 3
Pu-241 14.4 a 190 ~6 ~3.2
Pu-242 376,000 a 0.0021 0.00009 4.3
Cm-242 18.1 a 31 ~0.9 ~3
sources: UNSCEAR (2000) and Dreicer et al (1996)
*** Based on fuel particle release of 1.5% (Kashparov et al, 2003)
Shaded column - derived in this report by dividing column 4 values by column 3 values
17. Most of the radionuclides in table 2.1 will have completely decayed by now. Over the
next few decades, interest will continue to focus on Cs-137, with secondary attention on
Sr-90 which is more important in areas near Chernobyl. Over the longer term (hundreds to
thousands of years), the radionuclides of continuing interest will be the activation products,
including the isotopes of plutonium, neptunium and curium. The only radionuclide
expected to increase in the coming years is americium-241 which arises from the decay of
plutonium-241; the amount of americium-241 will reach a maximum about 100 years after
1986. Doses from americium-241 are expected to be small in comparison with those from
Cs-137.
Release Estimates for Main Nuclides
18. Our focus is primarily on the main nuclides mentioned above: tables 2.2 and 2.3 set out
published estimates of the percentages released and source terms.
Table 2.2 Estimates of percentage of core inventory released
Study Cs-137 Cs-134 Sr-90 I-131 Te-132
US DoE
Anspaugh et al, 1988 40% - 60% 40% - 60% - 40% - 60% 40% - 60%
Gudikson et al, 1989 40% 40% - 60% -
Seo et al, 1989 57% - 9% 70% -
OECD, 1995 20%-40% 20%-40% 4%-6% 50%-60% 25-60%2
Sich, 1996 30% 33% - 41% 15%
Devell et al, 1996 33%+10%1 33%+10%1 4% -6% 50% - 60% 25-60%2
Borovoi et al, 2001 33%±10% 33%±10% - 50% - 60% -
UNSCEAR, 2000
IAEA/WHO, 2005b ~33% 36% ~4.5% ~56% ~27%
1 table data in Devell et al, 1996 states "+" without explanation
2 Devell et al (1996) report that Te-132 air samples above the reactor and in Nordic countries indicated a
release fraction 1 to 2 times that of caesium.
Table 2.3 Estimates of released nuclides from Chernobyl - PBq
Study Cs-137 Cs-134 Sr-90 I-131 Te-132
Sorenson,1987 100 - - - -
US DoE
(Anspaugh et al, 1988) 98 - - - -
Aarkrog, 1994 100 50 8 - -
OECD, 1995 ~85 ~54 ~10 ~1,760 ~1,150
UNSCEAR, 2000
IAEA/WHO, 2005b ~85 ~54 ~10 ~1,760 ~1,150
23
19. Tables 2.2 and 2.3 indicate that the percentage of the core inventory Cs-137 released
ranged between 20% - 60%, ie between 85 -100 PBq. For iodine, the percentages
released ranged between 40% and 70%, and the amount was ~1,760 PBq according to
UNSCEAR (2000).
20. Given the length and severity of the graphite fire during which temperatures rose to
2500°C, it may be expected that more than a third of the Cs inventory may have been
released. Caesium is volatile: metallic caesium melts at 28°C and boils at 671°C, although
a range of Cs compounds with higher melting points would have been present in the
molten fuel. Even more volatile is iodine which has an elemental melting point of 114ºC
and and a boiling point of 185ºC. In our view, therefore, the above IAEA/WHO percentage
release figures may be underestimates. Because of its importance, we investigate the
matter further.
Estimates for Cs-137 and I-131
21. Detailed analyses of the source terms for the main nuclides were carried out by Sich
(1994, 1996) and Borovoi and Sich (1996). Using photographic evidence and
measurements of heat flux and radiation intensities, Sich and Borovoi estimated that 135
tonnes of melted nuclear fuel, that is 71% of the initial inventory of 190 tonnes, remained
under the reactor. Other researchers have suggested different values. Purvis (1995)
estimated between 27-100 tonnes and Kisselev et al (1995, 1996) reported that only 24
tonnes could be identified visually. These differences clearly require further study and
explanation.
22. Sich estimated the nuclide concentrations remaining in two compartments (a) the fuel
remaining below the reactor, and (b) the fuel ejected by the explosions. The fuel in the first
compartment released its volatile nuclides during the 10 day period before the melting of
the lower biological shield and the subsequent draining of molten fuel into chambers below
the reactor. The fuel in the second compartment would have released its volatile nuclides
primarily during the two explosions.
23. In the first compartment, Sich's measurements indicated that 35%19 of the fuel's
original Cs-137 remained in the solidified fuel lava, ie 65% had been volatilised. Borovoi
and Gagarinski (2001) later estimated that 60% had been volatilised. In the second
compartment, ie the fuel ejected by the explosions and fires, Sich estimated that only 30%
of its caesium content was volatilised.
The Question of Plate-Out
24. Sich further assumed that, during the 10 day period of maximum releases, 50% of the
volatilised caesium and iodine would have "plated-out" on adjacent structures, ie
precipitated on cooler surfaces. As far as we are aware, this assumption does not appear
to be backed by evidence or arguments. Sich's assumption of 50% plate-out in the first
compartment is questionable for many reasons, including
19
Sich stated the 0.35 fraction was "surprising", in other words, it was an unexpectedly large amount, and he
surmised that the carbon moderator in the stricken reactor had acted to filter and retain Cs isotopes during
the 7 day fire. However this filtration did not occur with other nuclides: for example over 95% of (less volatile)
ruthenium isotopes were released, cf 65% of caesium isotopes.
24
• the 2500°C temperatures (Devell et al, 1986)20 attained in the reactor with similar
temperatures in the structures above it.
• the destroyed reactor - see Figure 2.1 - reveals few structures above the reactor
on which plate-out could occur.
• some plate-out may have occurred when temperatures were low. However, as
temperatures rose throughout the 10 days, earlier plated isotopes may have been
revaporised.
• UNSCEAR 2000 (Volume II, page 455, paragraph 15) states "The very high
temperatures in the core shaft would have suppressed plate-out of radionuclides
and maintained high release rates of penetrating gases and aerosols."
• Sich uses only 10%, not 50%, plate-out for his second compartment.
• Sich states his estimates of fractional releases are "probably quite low" and those
for plate-out are "probably high". See footnote (a) to his original table in Annex 2B.
• his release estimates are low compared with other estimates using the same
method.
25. Despite his unrealistic values for plate-out, Sich's overall methodology is useful.
Therefore we have used this to derive better estimates of the source terms for Cs-137 and
I-131 in Annex 2C. For Cs-137, our estimated range of the percentage released is 37% -
49% with a point estimate of 43%. This is the same as the higher value of the range 23%
to 43% cited by UNSCEAR (2000) and IAEA/WHO (2005b) - see table 2.2. It lies within
the 40-60% range estimated by Anspaugh et al (1988) for the US Department of Energy -
see table 2.3. In Bq terms, our estimate for Cs-137 lies in the range of 95 -128 PBq with a
point estimate of 110 PBq. This is about a third greater than the UNSCEAR (2000)
estimate and is closer to the 98 PBq estimate estimated by the US DoE (Anspaugh et al,
1988).
26. For I-131, our estimated range is 54% to 75% released with a point estimate of 65%.
This is slightly higher that the 56% release estimated by UNSCEAR (2000), but similar to
the estimates by Gudikson et al (1989) and Seo et al (1989). Because of the greater
uncertainties with iodine releases, only UNSCEAR has made an estimate of the Bq
amount released - 1,760 PBq - see table 2.3. Our estimated range for I-131 is 1,700 to
2,300 PBq with a point estimate of 2,000 PBq which is 14% higher than the UNSCEAR
(2000) estimate. These estimates will have uncertainties attached to them mainly from the
plate-out fractions
20
Devell et al (1986) collected and analysed radioactive fuel particles by electron microscopy. They
concluded from their form and composition that the temperature in at least part of the reactor core reached
2,500°C.
25
Annex 2A: Excerpt from OECD/NEA (1995)
"The Accident
The accident occurred at 01:23 on Saturday, 26 April 1986, when the two explosions destroyed the core of
Unit 4 and the roof of the reactor building. In the IAEA Post-Accident Assessment Meeting in August 1986
(IA86), much was made of the operators' responsibility for the accident, and not much emphasis was placed
on the design faults of the reactor. Later assessments suggest that the event was due to a combination of
the two, with a little more emphasis on the design deficiencies and a little less on the operator actions.
The two explosions sent a shower of hot and highly radioactive debris and graphite into the air and exposed
the destroyed core to the atmosphere. The plume of smoke, radioactive fission products and debris from the
core and the building rose up to about 1 km into the air. The heavier debris in the plume was deposited close
to the site, but lighter components, including fission products and virtually all of the noble gas inventory were
blown by the prevailing wind to the North-west of the plant. Fires started in what remained of the Unit 4
building, giving rise to clouds of steam and dust, and fires also broke out on the adjacent turbine hall roof
and in various stores of diesel fuel and inflammable materials. Over 100 fire-fighters from the site and called
in from Pripyat were needed, and it was this group that received the highest radiation exposures and
suffered the greatest losses in personnel. These fires were put out by 05:00 hr of the same day, but by then
the graphite fire had started. Many firemen added to their considerable doses by staying on call on site. The
intense graphite fire was responsible for the dispersion of radionuclides and fission fragments high into the
atmosphere. The emissions continued for about twenty days, but were much lower after the tenth day when
the graphite fire was finally extinguished.
The Graphite Fire
While the conventional fires at the site posed no special fire fighting problems, very high radiation doses
were incurred by the firemen. However, the graphite moderator fire was a special problem. Very little national
or international expertise on fighting graphite fires existed, and there was a very real fear that any attempt to
put it out might well result in further dispersion of radionuclides, perhaps by steam production, or it might
even provoke a criticality excursion in the nuclear fuel.
A decision was made to layer the graphite fire with large amounts of different materials, each one designed
to combat a different feature of the fire and the radioactive release. Boron carbide was dumped in large
quantities from helicopters to act as a neutron absorber and prevent any renewed chain reaction. Dolomite
was also added to act as heat sink and a source of carbon dioxide to smother the fire. Lead was included as
a radiation absorber, as well as sand and clay which it was hoped would prevent the release of particulates.
While it was later discovered that many of these compounds were not actually dropped on the target, they
may have acted as thermal insulators and precipitated an increase in the temperature of the damaged core
leading to a further release of radionuclides a week later.
By May 9, the graphite fire had been extinguished, and work began on a massive reinforced concrete slab
with a built-in cooling system beneath the reactor. This involved digging a tunnel from underneath Unit 3.
About four hundred people worked on this tunnel which was completed in 15 days, allowing the installation of
the concrete slab. This slab would not only be of use to cool the core if necessary, it would also act as a
barrier to prevent penetration of melted radioactive material into the groundwater.
In summary, the Chernobyl accident was the product of a lack of "safety culture". The reactor design was
poor from the point of view of safety and unforgiving for the operators, both of which provoked a dangerous
operating state. The operators were not informed of this and were not aware that the test performed could
have brought the reactor into explosive conditions. In addition, they did not comply with established
operational procedures. The combination of these factors provoked a nuclear accident of maximum severity
in which the reactor was totally destroyed within a few seconds."
26
Annex 2B. Original table reproduced from Sich (1996)
(NB. This original table contains a mathematical mistake. The fig for I-131 in the last
column should be 34.5 not 24.5 MCi.)
27
Annex 2C. Derivation of Cs-137 and I-131 source terms
(i) Tables 2C(i) and 2C(ii) set out our calculations for Cs-137 and I-131 releases using
Sich's methodology but with a range of reasonable parameter values. In particular, we
assume values of between 20% and 50% plate-out for the first compartment. In addition,
we use the later value of 60% estimated by Borovoi and Gagarinski (2001) as the Cs
release fraction for both compartments.
Table 2C(i) - Estimated Cs-137 releases using Sich's methodology and a range of
reasonable assumptions for plate-out fraction in the first compartment (in bold)
First Compartment Second Compartment
Author Initial
Activity
Fraction
Fuel
below
reactor
Fraction
Released
(1-
Plate
out)
Released Fraction
of Fuel
ejected
Fraction
Released (1-
Plate
out)
Released Total
Cs-137
release
% of core
inventory
released
This
report 260
PBq .71 .6
Borovoi .8
this
report
= 88 PBq .29 .6
Borovoi .9
Sich = 40 PBq 128
PBq 49%
This
report 260
PBq .71 .6
Borovoi .7
this
report
= 77 PBq .29 .6
Borovoi .9
Sich = 40 PBq 117
PBq 45%
This
report 260
PBq .71 .6
Borovoi .6
this
report
= 66 PBq .29 .6
Borovoi .9
Sich = 40 PBq 106
PBq 41%
This
report 260
PBq .71 .6
Borovoi .5
this
report
= 55 PBq .29 .6
Borovoi .9
Sich = 40 PBq 95 PBq 37%
Sich 260
PBq .71 .65
Sich .5
Sich = 60 PBq .29 .3
Sich .9
Sich = 20 PBq 80 PBq 31%
(ii) To help, we shall work through an example. Go to the first row starting with "This
report" on the extreme left. Moving to the right into the green section, we multiply the initial
260 PBq in the reactor x 0.71 x 0.6 x 0.8 to arrive at 88 PBq released from compartment 1.
In the yellow section, we multiply the initial 260 PBq x 0.29 x 0.6 x 0.9 to get 40 PBq
released from compartment 2. Adding the green and yellow PBq values, we arrive at the
total of 128 PBq in the penultimate column. This is 49% of the initial 260 PBq in the final
column.
(iii) For Cs-137, from table 2C(i), our estimated range of the percentage released is 37% -
49% with a point estimate of 43%. This is the same as the higher value of the range 23%
to 43% cited by UNSCEAR (2000) and IAEA/WHO (2005b). In Bq terms, our estimate for
Cs-137 lies in the range of 95 -128 PBq with a point estimate of 110 PBq. This is about a
third greater than the UNSCEAR (2000) estimate and is closer to the 98 PBq estimate
derived by Anspaugh et al (1988) for the US Department of Energy.
(iv) For I-131, in table 2C(ii) we use the later findings by Borovoi and Gagarinski (2001)
that no I-129 was found in the fuel below the reactor, indicating all the I-131 was released
from the first compartment. We also use their findings that 25% - 37% (average ~30%) of
the original I-131 remained in the ejected fuel indicating that an average of 70% of the I-
131 was released from the second compartment.
28
Table 2C(ii). Estimated I-131 releases using Sich methodology and a range of
reasonable assumptions for plate-out fraction in the first compartment (in bold)
First Compartment Second Compartment
Author Initial
Activity
Fraction
Fuel
below
reactor
Fraction
Released
(1-
Plate
out)
Released Fraction
of Fuel
ejected
Fraction
Released (1-
Plate
out)
Released Total
Cs-137
release
% of core
inventory
released
This
report 3080
PBq .71 1
Borovoi .8
this
report
=1750
PBq .29 .7
Borovoi .9
Sich =563
PBq 2313
PBq 75%
This
report 3080
PBq .71 1
Borovoi .7
this
report
=1530
PBq .29 .7
Borovoi .9
Sich =563
PBq 2093
PBq 68%
This
report 3080
PBq .71 1
Borovoi .6
this
report
=1294
PBq .29 .7
Borovoi .9
Sich =563
PBq 1857
PBq 60%
This
report 3080
PBq .71 1
Borovoi .5
this
report
=1093
PBq 29 .7
Borovoi .9
Sich =563
PBq 1656
PBq 54%
Sich
1996 3080
PBq .71 .8
.Sich .5
Sich =875
PBq .29 .5
Sich .9
Sich =402
PBq - 41%
(v) For I-131, from table 2C(ii), our estimated range is 54% to 75% released with a point
estimate of 65%. This is slightly higher that the 56% release estimated by UNSCEAR
(2000), but similar to the estimates by Gudikson et al (1989) and Seo et al (1989).
Because of the greater uncertainties with iodine releases, only UNSCEAR has made an
estimate of the Bq amount released - 1,760 PBq - see table 2.3. Our estimated range for I-
131 is 1,700 to 2,300 PBq with a point estimate of 2,000 PBq which is 14% higher than the
UNSCEAR (2000) estimate.
29
Chapter 3. Dispersion and Deposition of Chernobyl Fallout
Introduction
1. During the 10 day period of maximum releases from Chernobyl, volatile radionuclides
were continuously discharged into the atmosphere. During this period, the prevailing winds
changed direction frequently with the result that the radioactive plume was widely spread
and Chernobyl's nuclide emissions were dispersed across many parts of Europe, and later
across the entire northern hemisphere. For example, relatively high concentrations of
nuclides from the Chernobyl plume were measured at Hiroshima Japan, over 8,000 km
from Chernobyl (Kiyoshi, 1987). European dispersal is shown in the satellite pictures from
the Lawrence Livermore Research Laboratory in the US, reproduced from OECD/NEA
(2002) in Figure 3.3.
Figure 3.1 Areas covered by the main body of Chernobyl radioactive clouds on
successive days during the release
on April 26, 1986
on April 28, 1986
on April 30, 1986
on May 2, 1986
30
on May 4, 1986
on May 6, 1986
original source: ARAC, Lawrence Livermore Research Laboratory, California, US
reproduced from OECD (2002)
2. Initially, the dry deposition of volatile radionuclides from the Chernobyl plume across
Europe and the northern hemispheres was modelled by a number of authors (see
discussion in UNSCEAR, 1988 and Hohenemser, 1988). However, rainfall resulted in
markedly heterogeneous depositions of fallout throughout Europe and the northern
hemisphere. Most ejected fuel was deposited in areas near the reactor with wide variations
in deposition density, although some fuel hot particles were transported thousands of
kilometres. The heaviest concentrations of nuclides and fuel particles were deposited in
Belarus, Russia and Ukraine. More than half of the Cs-137 source term was deposited in
countries outside Belarus, Ukraine and Russia (see table 3.6 below): as an approximation,
it is assumed that all volatile radionuclides were similarly dispersed.
3. An important characteristic of fallout is solubility in water as this determines the initial
mobility and bioavailability of deposited radionuclides in soils and surface waters after
deposition. In fallout sampled at Chernobyl, water-soluble and exchangeable forms of Cs-
137 varied from 5% to >30% (Bobovnikova et al, 1991). Water-soluble and exchangeable
forms of Sr-90 deposited on 26 April accounted for only about 1%, but increased to 5% -
10% in subsequent days due to the smaller size of particles emitted by the graphite fire. At
further distances, the fraction of soluble condensed particles increased considerably
because of their smaller particle sizes: for example almost all Cs-137 deposited in 1986 in
the United Kingdom was water-soluble and exchangeable (Hilton et al, 1992).
4. Radiation exposures to humans from Chernobyl occurred via four main pathways
(i) External exposures by the Chernobyl plume as it passed overhead
(ii) Inhalation of nuclides in the plume
(iii) Continuing external radiation from nuclides deposited on the ground
(iv) Ingestion of contaminated food
At the time of the accident, pathways (i) and (ii) were very important, especially (ii) for
thyroid doses. Twenty years later, pathways (iii) and (iv) are the main contributors to dose.
Deposition Density Measurements
5. Between 1995 and 1998, the European Commission and Member States measured
Cs-137 contamination levels throughout Europe using extensive gamma measurements
from low altitude flights (EC, 1998). The quality of the EC mapping was determined largely
31
by the density of sampling and measurement points. Hundreds of thousands of
measurements were carried out in Ukraine, Belarus, Russia and Sweden by aero-gamma
surveys conducted on map scales of 1:200k and 1:1,000k at flight altitudes of 50 -150 m.
About 10,000 soil samples were taken in Central and Western European countries. The
territories of Norway, Finland, UK, Greece, Germany, the Netherlands, Austria, and
Switzerland were investigated most thoroughly. The EC's comprehensive contamination
data for Cs-137 concentrations above 4 kBq/m2 are reproduced in table 3.1 below.
6. The contamination data were mapped and Figure 3.2 reproduces plate 1 from EC,
1998. This indicates the very widespread nature of Cs-137 contamination throughout
Europe.
Figure 3.2 Caesium-137 contaminated areas in European countries
reproduced with permission from De Cort et al, 1998
7. In addition, particularly large areas of Belarus, Ukraine and Russia were contaminated
with high levels of radioactivity, as shown in figures 3.3, 3.4 and 3,5.
32
Figure 3.3 Caesium-137 contaminated areas in Belarus
reproduced with permission from De Cort et al, 1998
Figure 3.4 Caesium-137 contaminated areas in Ukraine
reproduced with permission from De Cort et al, 1998
33
Figure 3.5 Caesium-137 contaminated areas in former USSR
reproduced from IAEA/WHO (2005b)
34
Table 3.1 Areas contaminated by Caesium-137 in European countries
Areas (1,000 km2) contaminated above specified levels (kBq/m2)
Country
4-10
kBq/m2 10-20
kBq/m2 20-40
kBq/m2 40-100
kBq/m2 100-185
kBq/m2 185-555
kBq/m2 555-1480
kBq/m2 >1480
kBq/m2 Totals
Russia
(European part) 1110 250 180 44 7.2 5.9 2.2 0.46 1600
Ukraine 240 120 43 29 4.3 3.6 0.73 0.56 441
Romania 120 54 13 1.2 0 0 - - 188
Norway 89 44 23 7.1 0.08 0 0 163
Finland 50 32 59 19 0 0 - - 160
Germany 110 29 14 0.32 0 0 - - 153
Sweden 55 31 33 23 0.44 >0.01 - - 142
Belarus 50 22 16 21 8.7 9.4 4.4 2.6 134
Italy 37 37 15 7 1.3 0.05 - - 97
Poland 71 10 3.5 0.52 0 0 - - 85
United Kingdom 64 15 1.7 0.09 0.04 0.03 - - 81
Austria 17 28 25 11 0.08 - - - 81
Greece 37 21 8.3 1.2 0.04 - - - 68
Czech Rep 42 13 3.5 0.21 0.01 - - - 59
France 54 1.2 0 0 0 - - - 55
Lithuania 48 0.05 0 0 - - - - 48
Ireland 47 1.3 0.01 0 - - - - 48
Croatia 29 11 0.03 0 - - - - 40
Slovak Rep 32 6.8 0.61 0.02 - - - - 39
Switzerland 26 6.4 2.3 0.73 - - - - 35
Hungary 29 5.2 0.23 0 - - - - 35
Moldova 13 19 1.9 0 - - - - 34
Turkey
(European part) 23 0.04 0 0 - - - - 23
Latvia 21 0 0 0 - - - - 21
Slovenia 2.5 8.1 8.7 0.61 - - - - 20
Estonia 8.7 1.7 0.28 0 - - - - 11
Denmark 0.8 - - 0 - - - - 0.8
Netherlands 0.64 - - 0 - - - - 0.64
Luxembourg 0.12 - - 0 - - - - 0.12
Belgium 0.09 - - 0 - - - - 0.09
Totals 2427 767 452 166 22 19 7 3.62 3,864
source: EC (1998)
greyed column inserted by the authors of this report
8. The data in the final column in table 3.1 was calculated by adding the data in the
columns to the left. The final column indicates that the European area contaminated by
Chernobyl (above the 4 kBq/m2 Cs-137 level) is about 3,900,000 km2, which is about 40%
of the surface area of Europe (9,700,000 km2). This percentage is surprisingly large, yet it
was not reported in the 1998 EC report, and to our knowledge, it has not appeared in any
other official publications.
9. Of this total, 218,000 km2, or about 2.3% of Europe's surface area was contaminated to
levels greater than 40 kBq/m2. This is the area cited by the IAEA/WHO and UNSCEAR
reports. Therefore it is seen that IAEA/WHO and UNSCEAR have been economical with
their use of the available data, to say the least, as they have chosen to report upon only
highly contaminated areas.
10. A more detailed table showing the percentage areas of each country affected by
Chernobyl contamination is contained in Annex 3A. This indicates that Belarus and Austria
were the countries most affected by higher levels of contamination (>40 kBq/m2 Cs-137) in
terms of area. However, other countries were seriously affected; for example, more than
5% of Ukraine, Finland and Sweden were contaminated to high levels. Annex 3A also
reveals that > 80% of the surface areas of Moldova, Turkey (the European part), Slovenia,
35
Switzerland, Austria, and the Slovak Republic were contaminated to lower levels (>
4kBq/m2 Cs-137) and that 44% of Germany and 34% of the UK were similarly affected.
Official Reactions
11. When the accident occurred in 1986, many governments denied or minimised the
accident's effects (Medvedev, 1990). This was particularly true of the former Soviet Union,
but it was by no means the only country in denial. The UK Government, for example, was
accused of minimising Chernobyl's effects (Edwards, 1989) and misleading the public
(Weaver, 1986). In France, allegations were recently made in legal proceedings by
environmental groups21 that French official bodies had suppressed information about the
spread of radioactive fallout over France from the Chernobyl disaster. In December 2005,
the magistrate investigating the allegations, Maitresse Marie-Odile Bertella-Geffroy,
handed over a report she had commissioned from two independent scientists, Paul Genty
and Professor Gilbert Mouthon at Chimie et Physique Biologiques et Medicales, ENVA,
France. This stated that the French Government's Central Service for Protection against
Radiation (SCPRI) had known of high levels of contamination in Corsica and south-eastern
France but had kept the details under wraps. Instead it had issued imprecise maps that
concealed high levels of fallout in certain areas. The case is continuing (The Australian,
2005).
Cs-137 from Test Bomb Fallout
12. Considerable amounts of Cs-137 were deposited on Europe by fallout from the atomic
bomb tests in the 1950s and 1960s, and residual low levels of between 0 and 3.5 kBq per
m2 still existed in 1986, as shown in figure 3.6.
21
including CRIIRAD, AFMT and about 200 plaintiffs
36
Figure 3.6 Test bomb Cs-137 levels in Europe before Chernobyl
reproduced with permission from De Cort et al, 1998
13. These test bomb concentrations need to be considered when estimating Chernobyl
depositions. It is for this reason that table 3.1 above is restricted to data for concentrations
greater than 4 kBq/m2. In fact, the relevant table in the EC report cites concentrations for
below 4 kBq/m2 down to 0 - 1 kBq/m2. In our view, the interpretation of such low-level data
(0-4 kBq/m2) is difficult because of the possible presence of test bomb Cs-137: accordingly
they are not cited here. We acknowledge that this is a somewhat arbitrary decision, but in
our view a cut-off level has to be applied, otherwise one could be measuring mostly bomb
Cs-137 rather than Chernobyl-related Cs-137.
14. Nevertheless, in terms of actual amounts deposited, more Cs-137 from Chernobyl was
deposited (at concentrations lower than 4 kBq/m2) over Europe than is shown in table 2.1
above. In other words, the area values of Chernobyl contamination in table 2.1 should be
considered minimum values. Unfortunately, a further complication exists with the EC's
methodology for estimating Cs-137 levels: this is discussed in paragraphs 22-23.
37
Contamination Levels - What do they mean?
15. Table 3.2 sets out the definitions of the contamination zones in Belarus, Ukraine and
Russia.
Table 3.2 Zones of contamination in Belarus, Russia and Ukraine
Contamination density
Cs-137 (Ci/km2 ) Official designation of zones
Belarus* Russia** Ukraine***
1-5 Periodic radiation monitoring Privileged socio-
economic status Zone of enhanced
radiological control
5-15 Zone with the right to resettle Right to resettle (if
dose > 1 mSv/year) Zone of guaranteed
resettlement
15-40 Zone of secondary
resettlement
>40 Zone of priority resettlement
Mandatory
resettlement if 137Cs
>40 Ci/km2 or dose
>5 mSv/a. Voluntary
if below this
Zone of obligatory
resettlement
Territories adjacent to
Chernobyl (including 30-km
zone). Population
evacuated 1986 - 1987
Zone of evacuation
(exclusion zone) Resettlement zone
(exclusion zone) Exclusion zone
sources: * Goskomchernobyl, 2001 ** Russian Federation, 1992 *** Ukraine, 2001
16. After the Chernobyl accident, the then Soviet Union introduced various criteria for
managing contaminated areas. It established 1 curie (Ci) per km2 (equal to 40 kBq/m2) as
the lowest Cs-137 contamination level at which occasional controls were required:
voluntary resettlement was permitted above this level in practice. Stricter controls were
applied in more heavily contaminated areas. Subsequently, the 1 curie level was adopted
by Belarus, Ukraine and Russia. It is often viewed as a "safe" level by the media and
public, but in fact this is not the case. It is merely an administrative number, arbitrarily
chosen most probably for its convenience, being 1 curie per km2. The reality is that there is
no absolutely "safe" level of exposure to radioactivity. No matter how low the level, some
small risk will accrue. To determine how much and to establish whether this is acceptable,
it is necessary to estimate the radiation doses from external exposures to radioactive Cs-
137, which we do in the next paragraph.
17. In système internationale (SI) units, 1 curie per km2 is 40 kBq/m2 rounded to one
significant figure22. This concentration means that an area of one square meter would, on
average, emit the external beta and gamma radiation from 40,000 Cs-137 decays each
second. Determining the annual external radiation "dose" from external contamination is
not straightforward and depends on many factors, such as whether people live and work
outside, and whether they live in wooden or concrete homes, etc. Table 3.3 sets out official
estimates of external dose coefficients expressed in microsieverts (µSv) per kBq/m2 of Cs-
137 in the year 1996 from UNSCEAR (2000). This indicates an approximate average dose
of 10 µSv per kBq/m2 per year in 1996.
22
1.0 curie is equal to 3.7 x 109 becquerels. But since the administrative limit is expressed as a single digit,
ie 1 (and not 1.0), the equivalent is more correctly expressed as 4 x 109 Bq.
38
Table 3.3 Official estimates of absorbed dose rate in air / Cs-137 density
(Normalized absorbed dose rate in air in 1996)
[Columns 1 and 2 are the same annual dose rates expressed in different units. Column 1
is expressed in nGy per hour per kBq/m2. Column 2 is expressed in µGy per year per
kBq/m2.]
Column 1 Column 2
Country Dose rate
(nGy per hour per kBq/m2 Cs-137) Dose rate
(µGy per year per kBq/m2 Cs-137)
Belarus 1.0 8.7
Russia 0.85 7.4
Ukraine1 1.5 13
Ukraine2 1.1 9.6
average - 9.7
estimates from table 32 of UNSCEAR (2000)
estimates in greyed column estimated by the authors of this report
18. From table 3.3, we can derive an average dose conversion factor23 of about 10 µSv per
year per kBq/m2 of Cs-137. Although some uncertainty is inevitably associated with this
dose conversion factor, we derive an approximate dose estimate of 0.4 mSv per year from
external exposures to 40 kBq/m2 of Cs-137 for rural workers in Belarus, Ukraine and
Russia. This is about the same level as the annual dose constraint of 0.3 mSv used in the
UK for the regulation of radiological practices: doses to critical groups above this constraint
are not authorised. Other countries maintain more stringent limits. For example, guidance
from the US Environmental Protection Agency (US EPA, 1997) on minimum clean-up
levels for radioactively contaminated sites stipulates a maximum dose of 0.15 mSv per
year. This equates to a lifetime risk of fatal cancer of 3 x 10-4 (assuming a risk of 5% per
Sv over 40 years) and achieves an excess upper-bound lifetime cancer risk of 10-4 to 10-6
which is applied to all carcinogens in the US24.
19. Similarly, a contamination level of 4 kBq/m2 means that an area of one square meter
would, on average, emit the external radiation from 4,000 Cs-137 decays each second.
Using the above dose coefficient results in an external dose of about 0.04 mSv per annum.
This is a relatively "low" dose of radiation, about the same as the radiation dose from a
chest X-ray in a modern hospital25. Assuming a linear no-threshold dose-response
relationship, some health effects (ie a low number of additional cancers) would occur from
external exposures at these levels, although it would be almost impossible to ascertain
these small numbers of increased cases by means of epidemiology studies. To assess
health effects correctly in these situations of low radiation doses, we need to estimate
collective doses - see Chapter 5.
Cs-137 Contamination
20. The countries in table 3.1 are ranked by the size of their contaminated areas. This is
interesting, but it hides large variations in the amounts of Cs-137 (in Bq) deposited in each
country. These amounts are shown in tables 3.4 and 3.5 which rank countries by the Bq
amounts of Cs-137 contamination. These data are from two sources EC (1998) and US
23
in theory, this should be multiplied by ~0.9 to convert Gy to Sv, but we shall not introduce this factor here.
24
in 2005, the UK Government proposed new limits allowing permanent habitation on radioactively
contaminated land where annual doses did not exceed 10 mSv. However these have been objected to by
environmental groups, and they have not been implemented as of the date of drafting this report.
25
although this has a countervailing benefit for the individual who is X-rayed, and no benefit accrues to those
exposed by Chernobyl releases.
39
DoE (1987). Most data are from the EC Atlas but this does not cover Bulgaria, Albania and
most of former Yugoslavia which are covered in the US data. The EC data includes
amounts from areas with very low Cs-137 concentrations, ie 0 - 4 kBq per m2.
Table 3.4 Cs-137 deposition
ranked by country
Country PBq Country PBq Country PBq
Russia (Europe part) 29 Italy 0.93 Ireland 0.35
Belarus 15 France 0.93 Slovak Rep 0.32
Ukraine 13 United Kingdom 0.88 Latvia 0.25
Finland 3.8 Czech Rep 0.6 Estonia 0.18
Sweden 3.5 Lithuania 0.44 Turkey (Europe part) 0.16
Norway 2.5 Moldova 0.4 Denmark 0.087
Rumania 2.1 Slovenia 0.39 Netherlands 0.062
Germany 1.9 Spain 0.38 Belgium 0.053
Austria 1.8 Croatia 0.37 Luxembourg 0.008
Poland 1.2 Switzerland 0.36 Total 85
Greece 0.95 Hungary 0.35
data reproduced from table III.1 in EC, 1998
Table 3.5 Cs-137 deposition
ranked by country
Country PBq
Yugoslavia 5.4
Bulgaria 2.7
Albania 0.4
TOTAL 8.5
data reproduced from US DoE, 1987
[Yugoslavia reduced by 0.76 PBq to avoid double-counting Slovenia and Croatia in table 3.4]
21. These tables indicate that the three former Soviet Union republics received the highest
Bq amounts of Cs-137 fallout and that former Yugoslavia, Finland, Sweden, Bulgaria,
Norway, Rumania, Germany, Austria and Poland each received more than 1 PBq (1015
Bq) Cs-137, which is a large amount of radioactivity (cf the EU limit of 600 Bq per kg of Cs-
137 in dairy foods see table 4.2).
22. As shown in table 3.4, the total Cs-137 deposited on Europe was estimated by the EC
(1998) to be 85 PBq. An additional 8.5 PBq should be added to include Chernobyl fallout
on Yugoslavia, Bulgaria and Albania, giving a total of ~94 PBq in Europe. The EC report
stated that Cs-137 previously deposited on Europe from test bomb fallout in 1950s and
1960s should be deducted from these estimates. In 1996, about 20 PBq remained from
this fallout. However, a problem exists with the EC's methodology for arriving at the latter
estimate. The EC report stated that the average estimated contribution from weapons
fallout in each 1 x 1 km area cell was subtracted from the total caesium-137 estimated for
the same cell. Nevertheless, where the average fallout level exceeded the total deposition,
the contribution from Chernobyl was assumed to be zero. The report admitted that, as a
result,
"this approach has clear limitations and may result in large uncertainties in
estimates of the amount of Chernobyl caesium-137 deposited in some countries.
These uncertainties will be greatest for those countries with the lowest levels of
deposition. ....this aspect warrants further attention in future with a view to making
more rigorous estimates of Chernobyl deposition in the less affected countries."
23. So there are uncertainties in the EC's estimates of the amounts of caesium-137 from
residual test bomb fallout and of the Chernobyl caesium-137 amounts in some countries.
40
This means that the EC's deposition estimates are unsuitable for estimating the Chernobyl
source term, and in fact the EC report refrains from doing this.
Effects throughout Europe
24. The high levels of contamination from Chernobyl resulted in countermeasures and
restrictions on the use of contaminated foodstuffs being introduced in many areas of
Europe. Some of these restrictions are continuing to this day because unexpectedly high
levels of Cs-137 remain in the plants and soils of upland pastures. It was discovered that
acid soils promote the mobility and bioavailability of Cs and that many grass plants on
upland pastures accumulate it. These findings apply to varying extents to such countries
as the UK and Ireland. These findings are one of a number of surprising new findings
resulting from the Chernobyl accident.
25. In the United Kingdom, approximately 2,500 km from Chernobyl, fallout was deposited
on sheep-grazing upland areas in Wales, Cumbria and Scotland following heavy rainfall.
As a result, 8,900 farms were placed under restriction. In particular, the movement, sale
and slaughter of 4,225,000 sheep were restricted in order to stop contaminated animals
from entering the food chain. As of 2005, these restrictions remain on 375 farms and
215,000 sheep (RIFE, 2005).
26. Similar situations exist in parts of Sweden and Finland as regards stock animals,
including reindeer, in natural and near-natural environments. From a 2002 survey in EU
Member States, wild game (including boar and deer), wild mushrooms, berries and
carnivore fish from lakes in certain regions of Germany, Austria, Italy, Sweden, Finland,
Lithuania and Poland could occasionally reach caesium-137 contamination levels of
several thousand Bq/kg26.
27. In Germany, the Federal Office for Radiation Protection (BfS) stated in its 2004 annual
report27 that wild boar remained highly contaminated by Cs-137, especially in the south of
the country. According to studies carried out in 2004 in the Bavarian forest, soil
contamination levels were still as high as 100,000 Bq/kg. Cs-137 levels in wild boar
muscle were between 60 and 40,000 Bq/kg with an average of 6,800 Bq/kg. This average
is >10 times the 600 Bq/kg EU limit, see table 4.2. Only 15% of the boar samples were
within the EU limit, and 20% exceeded 10,000 Bq/kg. The EU limit was also exceeded in
less contaminated areas of Germany, the Pfaelzerwald for instance, which had soil Cs-137
contamination levels of up to several thousand Bq/m2. Recent data from the Rhineland-
Palatinate Research Institute for Forest Ecology and Forestry has revealed that more than
20% of wild boar samples had Cs-137 levels greater than 600 Bq/kg, with a peak value of
8,200 Bq/kg in 200428.
28. In 2005, the European Commissioner for Transport and Energy, Andris Piebalgs
explained29 that restrictions will need to be continued for many years.
"... one cannot count on notable changes in the radioactive caesium
contamination of certain products from natural ... environments. The
radioactive caesium contamination level of these products is
26
information contained in written answer to Question P-1234/05DE by MEP Rebecca Harms dated April 4,
2005
27
http://www.bfs.de/bfs/druck/jahresberichte/jb2004_kompl.pdf
28
information contained in written answer to Question P-1234/05DE by MEP Rebecca Harms dated April 4,
2005
29
written answer to Question P-1234/05DE by MEP Rebecca Harms dated April 4, 2005
41
essentially dependent on the half-life of this radionuclide....30 years.
The restrictions on certain foodstuffs from certain Member States
must therefore continue to be maintained for many years to come."
Continuing High Levels of Contamination
29. Over the next few hundred years, Cs-137 concentrations will gradually decline. This
decline will be due to a very small degree from environmental causes (ie Cs-137 entering
deeper levels of some soils), but will mostly will be a result of radioactive decay
(IAEA/WHO, 2005b). In practice, this means that Cs-137 contamination levels in wild foods
will remain high for a long time in the future. Indeed, in April 2005, the European Energy
Commissioner, Andris Piebalg admitted as much when he wrote that Cs contamination in
certain food products would not decline appreciably in the near future. He stated30
"Due to the experience gained since the Chernobyl accident, the Commission
believes that in the Member State regions significantly affected by the ....accident,
one cannot count on notable changes in the radioactive caesium contamination of
certain products from natural or near natural environments."
30. This was repeated in the IAEA/WHO (2005b) report which stated that Cs-137 and Sr-
90 concentrations and transfer coefficients31 had decreased only slowly in most plant and
animal foodstuffs during the last decade. This indicated that these radionuclides were
close to equilibrium in labile and non-labile pools of soil within agricultural ecosystems.
The IAEA/WHO concluded that as far as nuclide concentrations in plant and animal
foodstuffs were concerned:
"Given the slow current declines, and the difficulties in quantifying long-term
effective
half-lives for currently available data because of high uncertainties, it is not possible
to
conclude that there will be any further substantial decrease over the next decades,
except due to the radioactive decay of 137Cs and 90Sr with half-lives of about 30
years."
31. Annex 3B (table 3B(i)) sets out official estimates of residual amounts of radioactive
nuclides in the global environment from Chernobyl over the next 50 years until 2056 from
official data. However, 2056 is only 70 years after the Chernobyl accident and is an
arbitrary choice of date. Scientifically speaking, a more rigorous date would be 2286, ie
300 years after Chernobyl. The reason is that a convention exists among radiation
protection scientists that 10 half lives32 are necessary to ensure radioactivity levels decline
to an acceptably "safe" level. In the case of Cs-137, this would be about 300 years after
1986, or 2286. Indeed, for this reason, conventional proposals33 for dealing with
radioactive waste usually propose initial storage for 300 years to allow Cs-137 and Sr-90
decay sufficiently to enable its safe handling.
32. Due to the slow radioactive decay of Cs-137, radiation doses from external exposures
to Cs-137 will decline slowly over the next few hundred years. Table 3B(ii) in Annex 3B
30
written answer to a Question P-1234/05DE by MEP Rebecca Harms dated April 4, 2005
31
parameter describing the velocity of transport of a nuclide usually through soil
32
10 half lives will reduce the original activity by a factor of about 1000 (in fact by 1024)
33
see UK Committee on Radioactive Waste Management draft report (CoRWM, 2006)
42
contains estimated future external doses expressed per contamination level (kBq/m2) of
Cs-137. In addition, table 3B(iii) contains estimated future doses from both internal and
external radiation (1996-2056) to adults living in rural areas contaminated to 555 kBq/m2
(15 Ci/km2).
Restricted reporting by UNSCEAR (2000) and IAEA/WHO
(2005a, 2005b)
33. Unfortunately, the UNSCEAR (2000) and IAEA/WHO (2005a, 2005b) reports do not
discuss the comprehensive datasets on European contamination in EC (1998) and do not
cite EC (1998) among their references. No explanation is given for this omission.
Moreover, the UNSCEAR (2000) and IAEA/WHO (2005a. 2005b) reports do not discuss
deposition and radiation doses in any country apart from Belarus, Ukraine and Russia.
Indeed, UNSCEAR (2000) stated34
"Information on the contamination levels and radiation doses in other (ie other than
Belarus, Ukraine and Russia) countries will be presented only if it is related to
epidemiology studies conducted in those countries."
This restriction also apparently applies to the 2005 IAEA/WHO reports.
34. It appears that IAEA/WHO decided to focus in their reports only on countries with high-
density depositions of Cs-137 which meant Belarus, Ukraine and Russia. Although heavy
depositions certainly occurred there, the omission of any examination of Chernobyl fallout
in the rest of Europe and the northern hemisphere is questionable. Most of the Cs-137
source term from Chernobyl was deposited outside Belarus, Ukraine and Russia. This was
indicated by the US DoE (1987) and by UNSCEAR (1988) 35 which stated that less than
half of the Cs-137 source term was deposited in the then USSR (including Belarus,
Ukraine and Russia), with the majority deposited elsewhere, including the rest of Europe
(39%), Asia (8%), Africa (6%), and the Americas (0.6%) 36. UNSCEAR (2000) 37 also
stated that 40 PBq of Cs-137 was deposited in Belarus, Ukraine and Russia, ie less than
half its source term. These data are set out in table 3.6.
Table 3.6 Cs-137 depositions - PBq
Report Belarus,
Ukraine
and
Russia
Rest of
Europe Rest of World
(excl Europe
and Belarus,
Ukraine and
Russia)
Total
% in
Belarus,
Ukraine
and Russia
US DoE
(Goldman et al, 1987) ~33 ~33 ~32 ~98 ~33%
UNSCEAR, 1988 29 26 15 70 42%
EC, 1998 57 28 + 9* - - -
UNSCEAR, 2000 40 - - 85 47%
*for Yugoslavia, Bulgaria and Albania from US DoE data (1986)
shaded cells = estimated by this report
34
volume II, Annex J, page 453, paragraph 6
35
page 342, paragraph 201
36
table 24 of UNSCEAR, 1988
37
volume II, Annex J, page 462, paragraph 41
43
35. IAEA/WHO's decision to discount nuclide depositions and radiation exposures in
European countries and the northern hemisphere outside Belarus, Ukraine and Russia is
unfortunate. This restriction makes it difficult to estimate the collective dose impact of the
disaster as these depend on Cs-137 depositions, as we shall see in Chapter 5.
44
Annex 3A. Chernobyl contamination by area in each country
Table 3A(i) Cs-137 contamination >40 kBq/m2
Country
Total area
1,000 Km2 area contaminated >40
kBq/m2 Cs-137: 1,000 Km2 % OF COUNTRY
Belarus 210 46.1 22%
Austria 84 11 13
Ukraine 600 38 6.3
Finland 340 19 5.6
Sweden 450 23.4 5.2
Italy 280 8.35 3
Slovenia 20 0.61 3
Norway 320 7.2 2.3
Switzerland 41 0.73 1.8
Russia (Europe part) 3,800 60 1.6
Greece 130 1.26 1
Rumania 240 1.2 0.5
Czech Republic 79 0.22 0.28
Poland 310 0.52 0.16
Germany 350 0.32 0.09
United Kingdom 240 0.16 0.06
Slovak Republic 49 0.02 0.04
Totals 9,700* 218.95 2.3%
data from EC (1998) *includes areas of unlisted countries for which data is not available
Table 3A(ii) Cs-137 contamination 4 - 40 kBq/m2
Country
Total area area contaminated to 4 -
40 kBq/m2 Cs-137 % OF COUNTRY
Moldova 34 34 100%
Turkey (Europe part) 24 23 96
Slovenia 20 19.3 96
Switzerland 41 34.7 85
Austria 84 70 83
Slovak Republic 49 39 80
Rumania 240 187 78
Czech Republic 79 59 75
Lithuania 65 48 74
Croatia 56 40 71
Ireland 70 48 68
Ukraine 600 403 67
Greece 130 66.3 51
Norway 320 156 49
Germany 350 153 44
Belarus 210 88 42
Finland 340 141 41
Russia (Europe part) 3,800 1,530 40
Hungary 93 35 38
United Kingdom 240 81 34
Latvia 64 21 33
Poland 310 85 27
Sweden 450 119 26
Estonia 45 11 24
Italy 280 59 21
France 550 55 10
Luxembourg 2.6 0.12 5
Denmark 45 0.8 2
Netherlands 35 0.64 2
Belgium 31 0.09 0.2
Totals 9,700* 3,864 40%
data from EC (1998) *includes areas of unlisted countries for which data is not available
45
Annex 3B. Future Effects from Chernobyl
Table 3B(i) Residual radionuclides in the global environment from Chernobyl
Nuclide Half-life
years PBq
Released in
1986
PBq
Remaining in
1996
PBq
Remaining in
2006
PBq
Remaining in
2056
Sr-90 28.8 8 6 4.9 1.5
Cs-134 2.06 48 1.6 0.05 0
Cs-137 30.1 85 68 54 17
Pu-238 87.7 0.03 0.03 0.03 0.02
Pu-239 24,400 0.03 0.03 0.03 0.03
Pu-240 6,500 0.044 0.044 0.044 0.04
Pu-241 14.4 5.9 3.6 2.3 0.2
Am-241 432 0.005 0.08 0.12 0.2
source: Dreicer et al, 1996
Greyed column estimated by this report
Am-241 is the decay daughter of Pu-241, and therefore increases in magnitude. Am-241 doses are currently
not thought to exceed doses from other nuclides
Table 3B(ii). External effective doses per Cs- 137 density for residents of
contaminated areas, expressed over various time periods
Normalized effective dose (µSv per kBq/m2 Cs-137) for rural workers for time period
indicated
Country 1986 1986 - 1995 1996 - 2056 1986 - 2056
Former USSR 13-28 47- 62 48 95-110
Belarus 19 55 - -
Russia 15 37 28 65
Ukraine 24 60 28 88
source: table 31, UNSCEAR, 2000
Table 3B(iii). Estimated future doses (1996 - 2056) to adults living in rural areas
contaminated with 555 kBq/m2 Cs-137
Exposure Path Average Person
mSv Critical Group
mSv
External Radiation 20 27
Ingestion 10 33
Inhalation 0.1 0.3
TOTAL 30 60
source: table VII, Dreicer et al, 1996
46
Chapter 4. Health Effects Resulting from the Chernobyl Accident
Introduction
1. The immediate impacts of the Chernobyl accident on human health are now well
known. Acute radiation sickness was diagnosed initially in 237 emergency workers, of
whom 134 were treated clinically. 28 of them died in 1986 and a further 19 died between
1987 and 2004: more premature deaths may occur.
2. Less certain are the long term consequences of the accident. Exposure to ionising
radiation can induce cancer in almost every organ in the body. However, the latency
period38 between exposure to the radiation and appearance of the cancer can be many
years and even several decades. Clearly, therefore, it will be a long time before the full
effects of Chernobyl are known. Indeed, they may never be fully known, as cancer is a
common disease and it may be impossible to distinguish additional cancers from the large
number that would occur anyway.
3. Many publications list four categories of people affected by the Chernobyl accident.
(a) About 600 emergency workers, who were involved during the first day of the
accident. Of these, 22 workers received whole-body doses of external
radiation greater than 4 Gy and 21 received doses greater than 6 Gy.
(b) About 240,000 cleanup workers or liquidators who, from 1986 to 1989, were
sent in to the power station or the zone surrounding it for decontamination
work, sarcophagus construction, and other cleanup operations. Their
average dose was 100 mSv.
(c) About 100,000 persons who were evacuated within 2 weeks of the accident
and 16,000 more before the autumn of 1986. Their average dose was 33
mSv.
(d) The approximately 5 million residents of contaminated areas in Belarus,
Ukraine and Russia. Their average dose was 10 mSv. In addition, about
270,000 people were living in highly contaminated areas (more than 555
kBq/m2 Cs-137). Their average dose was 50 mSv.
4. In addition two other categories exist, which are often not discussed in official
reports and are conspicuously omitted from the IAEA/WHO (2005) reports:
(e) Approximately 600 million people who live in the rest of Europe.
(f) Approximately 4 billion people who live in the rest of the northern
hemisphere39
The effects in these last two categories are more diffuse and indeed have been difficult to
detect in epidemiology studies. Nevertheless, they can be estimated using collective
doses. These are considered in Chapter 5.
5. The health effects resulting from Chernobyl will be discussed under the following
headings:
(1) Thyroid cancer
(2) Leukaemia
38
the latency period is the time interval between the exposure to radiation and the appearance of cancer
39
little atmospheric mixing occurs between the northern and southern hemispheres
47
(3) Solid cancers
(4) Non-cancer effects
(5) Heritable effects
(6) Mental health and psychosocial effects.
6. There have been a large number of publications in all these categories, many of
which have been reviewed in the recent IAEA/WHO (2005a) report and the US BEIR VII
(2005) report. Papers continue to appear steadily, together with many anecdotal reports.
Because of the often long delay between exposure to radiation and the appearance of its
effects, lengthy follow up times are necessary before definite conclusions can be drawn.
For example, an important source of information about the induction of cancer by radiation
are the survivors of the Hiroshima and Nagasaki bombings, who have now been followed
up for more than 50 years; it is only relatively recently (Preston et al, 2003) that clear
evidence has emerged of non-cancer effects due to radiation, for example cardiovascular
disease. It is therefore likely that a clear picture of the effects of Chernobyl will not emerge
for many years.
7. In this report, we shall concentrate on more recent publications, using mainly those
published in peer-reviewed journals, always mindful of the many uncertainties involved in
trying to unravel the past and the even greater ones in predicting the future. In view of the
use of the words ‘grays' and ‘sieverts', a short note on radiation units is set out in Annex 4.
(1) Thyroid Cancer
8. The first reports of an increase in thyroid cancer in children in the early 1990s
(Prisyazhiuk et al, 1991; Kazakov et al, 1992; Baverstock et al, 1992) were greeted with
considerable scepticism, as it was thought that more cancers were being seen simply
because more were being looked for - a ‘screening effect'. Moreover, the cancers had
appeared only four years or so after the radiation exposure, whereas the latency period of
thyroid cancer was thought to be ten years or more (UNSCEAR, 1988). Another reason for
scepticism was the belief that internal radiation from iodine-131 was not as carcinogenic
as external radiation. For example, there was no evidence of an increased incidence of
thyroid cancer in patients treated with iodine-131 for overactive thyroid (Hennemann,
1986).
9. However, further work (Astakhova et al, 1998; Jacob et al, 2000; Heidenreich et al,
1999) confirmed that there was indeed a dramatic increase in childhood thyroid cancer,
and there is now overwhelming evidence that this is related to exposure to iodine-131 and
possibly to other isotopes of iodine with shorter half-lives. Between 1990 and 1997,
childhood thyroid cancer increased by a factor of about 30 in the most heavily
contaminated areas (Tawn, 2001). The short latency period, 3-4 years, may well have
been influenced by the promptness with which screening of school children occurred in
areas of high fallout (Astakhova, 1998).
10. Up to 2005, there have been about 4,000 cases of thyroid cancer in Belarus,
Ukraine and Russia (Cardis, 2005a) in those who were under 18 at the time of the
accident; 3,000 of these were under 15. Annual incidence rates up to 2002 in Belarus and
Ukraine are shown in figure 4.1.
48
Figure 4.1. Annual thyroid cancer incidence rates per 100,000 in those who were
children and adolescents in 1986
source: Jacob et al (2005)
Figure 4.2 Annual incidence of thyroid cancer in Belarus
Incidence per 100 000 in Belarus
2.3
2.9
3.4 3.5
4
3.8
3.1
0.3 0.3 0.2
3
4.2
1.4
2.1
3.4
4.9
5.7 5.7
1.2 2.6
2.5
1.7
0.7
0
3.2
1.4
6.6
9.5
2.9
3.8
9.7
0.8 1,0
5.6
11.3
2.6
0.1
1.9
6.9
0.4 0.8
0
2
4
6
8
10
12
1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
C
a
s
e
s
p
e
r
1
0
0
0
0
0
Children (0 -14)
Adolescents (15 - 18)
Adults (19 - 34)
Adolescents
Children
Young adults
source: reproduced from lecture presentation by E Cardis to IAEA/WHO Conference Chernobyl: Looking
Back to Go Forward. September 2005. Original data from Dr Yuri Demidchik.
49
11. As can be seen in figure 4.2 for Belarus, the peak incidence in the 0-14 age group
was in 1995, and for the 15-18 age group, the peak was in 2000. In addition, the incidence
of thyroid cancer among adults is rising. (Cardis, 2005a).
12. Several important points emerge from the many papers published on this topic:
(i) the younger the person exposed, the greater the subsequent risk of developing
thyroid cancer. For a given intake of radioiodine, children will receive the highest
thyroid dose, as their thyroid glands are smaller and still growing
(ii) there is no clear evidence that exposure to iodine-131 in utero has caused thyroid
cancer, but the relevant studies have limited statistical power40
(iii) the risk of thyroid cancer is greater when there is iodine deficiency
(iv) dietary iodine supplements can reduce the risk, even if administered some time after
the exposure to radiation
13. Before the Chernobyl accident, the principal source of information about radiation-
induced thyroid cancer in children was several studies in which children had been exposed
to external X-rays. A survey of these studies (Ron et al, 1995) showed that the thyroid
cancer risk was still increased more than 40 years after the initial exposure. For children
aged under 15 at the time of exposure there was a linear relationship between risk and
dose down to 100 mGy. The best estimate of the excess relative risk per gray (ERR/Gy)41
was 7.7 (95% confidence intervals 42 2.1 to 28.7). This is consistent with the estimate by
Cardis (2005b) in which the ERR/Gy varied between 4.5 to 7.4, depending on the model
used (95% confidence intervals 1.0 to 16.3). More recently, Jacob et al (2005, 2006) from
their study of thyroid cancer risk in Ukraine and Belarus, also estimated ERR/Gy values
close to those observed by Ron et al (1995).
How many more thyroid cancers can we expect?
14. Because we do not know at this stage how the risk will change in the future, there
are considerable uncertainties in estimating the total number of thyroid cancers that are
likely to result from Chernobyl. In the words of the IAEA/WHO report [ pp 39-40]:
‘although thyroid cancer risk is continuing at a high level, and there is no reason
to expect a decrease in the next 15 or more years, at the present time the
follow-up of Chernobyl-exposed children is too short to determine the long-term
risks'.
15. Some attempt at prediction can be made by assuming that the change in risk in the
future will be similar to that seen with external radiation. Jacob et al (2000) estimate that
for Belarus, starting in 1997, 15,000 thyroid cancers will occur with an uncertainty range of
5,000-45,000. The UNDP (2002) says that ‘according to conservative estimates, the
numbers of thyroid cancers are likely to rise to 8,000 to 10,000'. Cardis et al (1999) predict
40
The power of a study is the probability of detecting a given difference. Even if a difference is real, if it is
small and the size of the groups we are comparing is small, there will only be a very small probability of
detecting the difference.
41
Relative risk (or Odds Ratio) is the risk of contracting a particular disease for an exposed individual,
divided by the risk of contracting that disease in an unexposed individual. So if the relative risk (RR) of
thyroid cancer is 8.7 per gray (8.7/Gy), this means that a radiation dose of 1 gray (Gy) to the thyroid will
make that individual 8.7 times more likely to contract thyroid cancer. Excess relative risk (ERR) = relative risk
(RR) - 1; so a relative risk of 8.7 corresponds to an excess relative risk of 7.7.
42
If we were to carry out a large number of similar studies, the true value of the risk would lie within the 95%
confidence interval in 95% of the studies. So essentially the confidence interval gives a range of values with
which the data are compatible.
50
the lifetime number of thyroid cancers that would develop among children in Belarus aged
less than 5 years at the time of the accident. Depending on the risk projection used, their
estimates range between 18,000 and 66,000 excess thyroid cancers. The lower estimate
assumes a constant relative risk for 40 years after exposure; the higher assumes a
constant relative risk over the whole of life.
16. A very recent study (Imaizumi et al, 2006) of thyroid cancer incidence in the
survivors of the Japanese atomic bombs found that a significant dose-response
relationship still existed nearly 60 years after exposure, and that the effects were
significantly greater in those exposed at younger ages. This suggests that of the above
two risk projections, the latter may be more likely with a consequently larger number of
thyroid cancers.
Thyroid cancer in adults
17. Although there is now good evidence from a number of studies that the increased
incidence of thyroid cancer in children is related to Chernobyl, the association is less clear
in adults. Table 4.1 contains a review by Moysich et al (2002) of studies of adult thyroid
cancer incidences.
Table 4.1 Studies of adult thyroid cancer incidence
Reference Country Kind Period Comparison
Type Exposure
variables Findings
Mettler et al,
1992 Ukraine descriptive 1990 Prevalence of
thyroid nodules high and low
contam villages No differ in
prevalence of
thyroid
nodules
Prisyazhniuk
et al, 1995 Ukraine descriptive 1980-
1993 Incidence rates
over time - No sig
increase
Inskip et al,
1997 Estonia liquidator
cohort 1995 Prevalence of
thyroid nodules questionnaire;
measurements No differ in
prevalence of
thyroid
nodules
Ivanov et al
1997a,
1997b
Russia incidence,
mortality 1986-
1990 Incidence in
cohort vs
population
Assigned ext
doses during
clean-up
exposures
>incidence in
liquidators
SIR=670 95%
CI=420-1030
Ivanov et al
1997c Russia Descriptive
incidence 1981-
1995 Incidence rates
over time No sig
increase in
contam vs
non-contam
areas
Rahu et al,
1997 Estonia Liquidator
cohort 1986-
1993 Incidence in
cohort vs
population
questionnaire No excess
thyroid cancer
incidence
Ivanov et al,
1999 Russia descriptive
incidence 1982-
1995 Incidence rates
over time Contam vs non-
contam areas >nos of
thyroid
cancers in
contam areas
source: Moyisch et al, 2002
18. One study which has shown a significant effect examined data on 168,000 cleanup
workers from Russia (Ivanov et al, 1997d). The ERR/Gy for thyroid cancer was found to be
5.31 (95% CI: 0.04, 10.58) which is consistent with the value of 7.7 estimated by Cardis
(see paragraph 13 above).
51
Thyroid cancers outside Belarus, Ukraine and Russia
19. In total, about 2,000 PBq of iodine-131 was released in the Chernobyl accident, and
more than half of this was deposited outside Belarus, Ukraine and Russia. One might
therefore expect some thyroid cancers to occur elsewhere, at least in the more
contaminated countries. The 2005 IAEA/WHO reports did not consider this, except to refer
to the Sali review (Sali et al, 1996). Although this concluded that no increase in thyroid
cancer among children was observed, it also pointed out that "no study focussed
specifically on childhood thyroid cancer, since the disease is so rare and a small increase
could have gone undetected in these studies". (emphasis added)
20. Since 1996, there have in fact been a number of reports of possible increases in
thyroid cancer in other European countries. Murbeth et al (2004) reported an increase in
the Czech Republic. They found the incidence of thyroid cancer had increased by 2.6%
per year (95%-CI: 1.2 - 4.1, p=0.0003) in all age categories after 1990. The Czech
Republic received a moderate amount of radioactive fallout: as shown in Annex 3A, with
three quarters of its surface area slightly contaminated (ie to a level greater than 4
kBq/m2). The authors came to the reasonable conclusion that "one should look carefully at
collective dose and at the groups of persons low in individual organ dose but high in
number". This recommendation has not been followed up by the IAEA/WHO (2005) reports
which, as we stated earlier, fail to examine health effects in Europe outside Belarus,
Ukraine and Russia.
21. Cotterill et al (2001) reported an increasing incidence of thyroid cancer in the North
of England, particularly Cumbria one of the two areas in the UK receiving the heaviest
fallout. They pointed out that iodine-131 concentrations in rainwater were as high as 784
Bq/litre and in goat's milk as high as 1,040 Bq/litre. These concentrations are higher than
the EC's Community Food Intervention Levels shown in table 4.2.
Table 4.2 Community Food Intervention Levels (Bq/kg)
Baby Foods Dairy Produce Other Foods
Sr-90 75 125 750
I-131 150 500 2,000
Sum of
Cs-137 and Cs-134
370 370 600
Plutonium-239 1 20 80
source: European Council Regulations (Euratom) Nos 3955/87, 944/89, 2218/89, 4003/89, 737/90 and
1609/2000
22. Shortly after the accident, Baverstock (1986) estimated that young children might
receive thyroid doses between 10 and 20 mGy resulting in a 10-20% greater risk of thyroid
cancer. Thyroid doses of 20 mGy are not negligible; the study of childhood thyroid cancer
in Belarus and Russia by Jacob et al (1999) points out that the risk of thyroid cancer was
elevated even in the lowest dose group, which received an average dose of only 50 mGy
(range 25 to 98 mGy).
23. Although Cotterill et al state that factors such as earlier detection of tumours may
have contributed to the increasing incidence, their conclusion is that ‘further collaborative
international studies are needed to investigate changes in the incidence of thyroid cancer
in children and young adults'. To the best of our knowledge, this has not been done.
24. A contrary view was taken by Colonna et al (2002), who examined the incidence
data for thyroid cancer from eight French cancer registries over the period 1978-1997.
Their analysis showed an increase in thyroid cancer but not a recent one, which therefore
52
could not be due to Chernobyl (the authors suggest that it could be a screening effect).
Obviously there are many uncertainties here, and it is clear that further work is necessary
to establish the extent of thyroid cancer in all countries, not just Belarus, Ukraine and
Russia, which received significant depositions of iodine-131.
(2) Leukaemia
25. Leukaemia is a well-documented effect of ionising radiation, with a relatively short
latency period of between 2 and 5 years.
Leukaemia in cleanup workers
26. Fairly clear evidence indicates that leukaemia incidence increased in the clean-up
workers: there was a two-fold increase in the most highly exposed group, although dose
estimates are uncertain. More precise estimates are expected in the near future from on-
going studies (Cardis 2005a). Ivanov et al (1997d) in their study of Russian cleanup
workers suggest that one of every two leukaemias diagnosed in emergency workers today
could be radiation-induced. They also point out that the incidence of leukaemia in the
Russian cleanup workers is consistent with the incidence predicted from the atomic bomb
survivors - see figure 4.3.
Figure 4.3 Anticipated and Observed Standardised Incidence Ratios of Leukaemia in
Russian Clean-up Workers (bars give 95% confidence intervals)
source: reproduced from Ivanov et al (1997d)
Leukaemia in residents of contaminated areas
27. Noshchenko et al (2001) have suggested that there was an increased risk of
leukaemia and acute leukaemia among children who were born in 1986 and were resident
in radioactively contaminated territories. They suggested this increased risk may be
associated with exposure to radiation. A case-control study by Noshchenko et al (2002)
examined residents aged 0-20 at the time of the Chernobyl accident in the most
53
radioactively contaminated territories of the Ukraine. They estimated the risk of radiation-
induced acute leukaemia for the period 1987-1997. The mean value of the estimated
accumulated dose to the bone marrow was 4.5 mSv, and the maximum was 101 mSv. A
statistically significant increased risk of leukaemia was found among males whose
estimated radiation exposure was higher than 10 mSv. This association was statistically
significant for acute leukaemia cases that occurred in the period 1993-1997, particularly for
acute lymphoblastic leukaemia. A similar association was found for acute myeloid
leukaemia, diagnosed in the period 1987-1992.
Leukaemia in other European countries
28. A number of studies appear to show an increased rate of childhood leukaemia as a
result of the Chernobyl fallout in parts of Europe. These were recently reviewed by the UK
Government's Committee Examining Radiation Risks of Internal Emitters (CERRIE, 2004)
which reported increases in infant leukaemia in West Germany, Greece and Belarus. The
IAEA/WHO (2005a) report on health effects downplayed the importance of these studies,
mainly because in their view the studies did not show a clear link between the incidence of
leukaemia and the degree of contamination (ie with dose).
29. However, given the large uncertainties in estimating doses from the degree of
contamination, the absence of a strong association between leukaemia incidence and
contamination does not rule out a radiation effect. The IAEA/WHO report (2005a) itself lists
the gaps in our knowledge of doses, including:
• "There is a lack of information on intercomparison between the various dosimetric
methods, though studies are currently in progress.
• Doses to be received in the future can only be predicted.
• The reliability of interviews used to assess factors which affect an individual's dose
has not been definitively assessed.
• Internal doses resulting from intakes of Sr-90 and of Pu-239 have received limited
attention.
• Methods to estimate doses received by those exposed in utero need further work on
the dosimetric methodology and validity of such dose estimates.
• The conversion of effective doses into absorbed organ-specific doses such as bone
marrow dose needs to be delineated."
30. In 1988, the European Childhood Leukaemia-Lymphoma Incidence Study (ECLIS)
was set up by IARC to investigate possible changes in incidence rates of childhood
leukaemia and lymphoma in Europe following the Chernobyl accident (Parkin, 1993). Data
were drawn from 36 cancer registries in 23 European countries. The study's follow-up
report for the period 1980-1991 (Parkin, 1996) found a small increase in leukaemia
incidence in Europe as a whole (13 cases observed against 7.3 expected in the highest
dose category), but there did not appear to be any association between the overall risk of
leukaemia in the period 1987-91 and the estimated doses received. However, they added
"at this stage of follow-up, the study has low power to detect a trend in risk with dose."
31. Regarding the possible consequences of radiation doses received in utero, Parkin
et al (1996) stated that they found
'"no suggestion of an increase in risk of childhood leukaemia for children exposed in
utero, even among the 1987 birth cohort in Belarus, some of whom would have
received in utero exposures in excess of 1 mSv".
However, both BEIR VII (2005) and the IAEA/WHO(2005a) suggested that there may well
be an effect:
54
"Focusing on the risk of leukaemia by age of diagnosis (six months intervals)
in relation to the estimated dose from the Chernobyl fallout received in utero,
preliminary results suggest a small increase in risk in infant leukaemia and
leukaemia diagnosed between 24-29 months." (IAEA/WHO, 2005a)
This issue remains unresolved. We recommend in paragraph 33 below that funding be
made available to IARC to clarify this matter.
32. The 1996 ECLIS paper was re-evaluated by Hoffmann (2002) who stated that
leukaemia incidence in the birth cohort of 1987 was increased in the two highest exposure
categories. He concluded that Chernobyl fallout could well have caused a small, but
significant, excess of childhood leukaemia cases in Europe, possibly due to the induction
of chromosome aberrations in early pregnancy. He went on to say that "...if indeed
Chernobyl fallout has caused childhood leukaemia cases in Europe, we would also expect
an increased incidence for other childhood cancers and excess malignancies in adults as
well as non-malignant diseases of all ages. Neither of these endpoints has as yet been
systematically studied." [emphasis added]
33. Although most of the data from the ECLIS study has now been collected and
studied, the final results of the study have not been published. This is unfortunate: we
recommend that funds be made available to permit the IARC to finish and publish its
study, and, while doing so, to resolve the evidence on the possible consequences of
radiation doses received in utero.
(3) Other solid cancers
Cancers in cleanup workers
34. Using data for cleanup workers from the Belarus National Cancer Registry,
Okeanov et al (2004) compared baseline incidence rates for overall cancer and various
cancers between 1976-85 with those between 1990-2000. An average 40% increase in
cancer incidence was observed in all regions with the most pronounced increase in the
most contaminated region. The 56% increase between the two time periods was
statistically significant. In 1997-2000, male liquidators had statistically significantly raised
risk of cancers of all sites, colon, lung and bladder cancer compared with adults in the
least contaminated region - as shown in table 4.2. Based on the estimated collective dose
to all cleanup workers in Belarus, Ukraine and Russian (see table 5.1), we might expect
around 1,000 - 2,000 excess deaths from solid cancers due to Chernobyl-related radiation
exposures in this group.
Table 4.2 Relative risk (RR) in cancer incidence (truncated age-standardised rate for
ages 20-85 per 100,000 population) in Belarus liquidators 1997-2000, compared with
control adults in least contaminated area (Vitebsk)
Cancer Incidence in
controls Incidence in
liquidators RR 95% confidence
intervals
All sites 373.3 449.3 1.20* 1.14 - 1.27
Breast (female) 58.6 61.3 1.05 0.81 - 1.35
Lung 52.4 67.3 1.28* 1.13 - 1.46
Stomach 41.7 44.9 1.08 0.92 - 1.26
Colon 17.0 22.3 1.31* 1.03 - 1.67
Rectum 19.0 18.4 0.97 0.77 - 1.23
Kidney 14.8 17.9 1.21 0.97 - 1.50
Bladder 10.9 17.0 1.55* 1.21 - 1.99
source: Okeanov et al (2004)
*statistically significant differences
55
Breast cancer in Belarus, Ukraine and Russia
35. Breast cancer is particularly important, because the risk of breast cancer among
women exposed in childhood and adolescence is the next highest risk after leukaemia and
thyroid cancer risks, as regards radiation-induced cancer (IAEA/WHO, 1995). Moreover,
iodine (and therefore radioiodine) is concentrated in the breast and salivary glands in
addition to the thyroid.
36. The IAEA/WHO report (2005a) acknowledges preliminary evidence of an increase
in the incidence of pre-menopausal breast cancer among women exposed at ages lower
than 45 years. This has been confirmed in a soon-to-be published study by Pukkala et al
(in press) which describes trends in the incidence of breast cancer in Belarus and Ukraine.
Their results suggest that women who reside in the most contaminated districts have an
increased risk of breast cancer compared with women in less contaminated areas. Doses
were estimated using average whole body doses accumulated since the accident, both
from external exposure and the ingestion of long-lived radionuclides. Those living in the
most contaminated districts had an average cumulative dose of 40 mSv or more. In these
districts, a significant two-fold increase in risk was observed during the period 1997-2001
compared with the least contaminated districts (the RR in Belarus was 2.24, 95% CI 1.51-
3.32 and in Ukraine the RR was 1.78, 95% CI 1.08-2.93). The increase, though based on
a relatively small number of cases, appeared approximately 10 years after the accident; it
was highest among women who were younger at the time of exposure, and was observed
for both localised and metastasised cancers. The authors conclude that "it is unlikely that
this excess could be entirely due to increased diagnostic activity in these areas."
Bladder and Kidney Cancer
37. Romanenko et al (2003) have reported that the incidence of urinary bladder cancer
in the Ukraine has increased from 26.2 to 43.3 per 100,000 person-years between 1986
and 2001. Romanenko et al (2000) have also reported that the incidence of cancer of the
kidney has increased from 4.7 to 7.5 per 100,000 person years.
Cancer in other European countries
38. Sali et al (1996) did not show any significant increases in cancer incidence in other
European countries, but they pointed out the lack of statistical power and the fact that the
study only covered the first nine years after the accident. Apart from leukaemia and
perhaps thyroid cancer in children, there is evidence that the minimum latency period for
most solid cancers is at least 10 years, so positive results would not have been expected
in 1996. According to Tondel et al (2004), there has been an increase in the total incidence
of cancer in northern Sweden; they estimate the excess relative risk to be 0.11 per 100
kBq/m2 of Cs-137 (95% confidence intervals 0.03 to 0.20) corresponding to a relative risk
of 1.21 for the most contaminated areas.
(4) Non-cancer effects
39. Over the last twenty years, a large number of health effects have been attributed to
the Chernobyl accident, including reduced fertility, increased incidence of stillbirths, birth
defects, Down's syndrome and infant mortality. Evaluation of the many reports and claims
is extremely difficult, given the prevailing context of political changes, adverse economic
circumstances and the apparent deterioration of many health and well-being indices. The
following problems are associated with many of these reports of adverse health effects:
• diagnostic criteria often differ
• insufficient control groups exist
56
• the studies have low power, and
• confounding factors are present, notably smoking and alcohol
In response to this, the IAEA/WHO has stated "there remains an overall need to design
future studies with extreme care in order to be able to obtain useful, unbiased and non-
confusing information" (IAEA/WHO, 2005a).
40. Many commentators have highlighted the marked general deterioration in health
indicators in Belarus, Ukraine and Russia. To give a graphic illustration - over the last 15
years, the average lifespan for a male in Russia has decreased from over 70 to about 61
years and in the Ukraine from 67 to 61 years: in western Europe, the average male life
span is about 75. The reasons for the considerable declines in health indicators in Belarus,
Ukraine and Russia are complex and due to a number of interrelated factors as described
in the UNDP (2002) report. Without access to government data, it is very difficult to assess
whether continuing exposures to low residual levels of radioactivity is a factor in the
general deterioration in health in Belarus, Ukraine and Russia. However it is noted that the
declines have occurred in all areas of Belarus, Ukraine and Russia and not merely those
areas affected by radioactive fallout.
41. Two non-cancer effects that are now reasonably well-documented and for which
there is clear evidence of a Chernobyl connection are cataract induction and
cardiovascular disease.
(a) Cataract Induction
42. Cataract-opacity (cloudiness of the eye lens) is an effect of exposure to radiation.
The latency period seems to be inversely proportional to dose, so long follow-up times are
necessary for small exposures. As with childhood thyroid cancer, this is another area
where previous thinking on radiation's effects is being revised as a result of Chernobyl. In
1990, the ICRP had stated that the threshold for opacities sufficient to cause impairment of
vision was in the range 2 to 10 Gy (ICRP, 1991). In contrast, IAEA/WHO now states that "a
focus of the Chernobyl eye studies is a hypothesis that radiation cataract/opacifications
detectable by an experienced examiner may occur at doses lower than previously thought.
These studies do not appear to support the older classic literature on radiation cataracts,
which concluded that a relatively high threshold (e.g. 2 Gy) must be exceeded for
cataracts to appear after ionising radiation exposure." (IAEA/WHO, 2005a) Studies of the
cleanup workers suggest that cataracts might be caused by doses as low as 0.25 Gy.
Lens changes related to radiation have been observed in children and young people aged
between 5 and 17 living in the area around Chernobyl (Day et al, 1995).
(b) Cardiovascular diseases
43. Here again an ICRP pronouncement has been contradicted by new evidence. ICRP
Publication 60 had stated (para 62, page 16) "It seems that no stochastic effects in the
exposed individual other than cancer (and benign tumours in some organs) are induced by
radiation. In particular, any life-shortening found in exposed human populations and in
experimental animals after low doses has been shown to be due to excess radiation-
induced cancer mortality" (ICRP, 1991). But the most recent follow-up of the Hiroshima
and Nagasaki survivors shows clearly that there is a linear dose-response relationship for
myocardial infarction among survivors exposed at less than 40 years of age (Preston et al,
2003). In fact, statistically-significant radiation effects are seen for
• heart disease (ERR/Sv = 0.17, 95% CI 0.08 to 0.26)
• stroke (ERR/Sv = 0.12, 95% CI 0.02 to 0.22)
• respiratory disease (ERR/Sv = 0.18, 95% CI 0.06 to 0.32) and
57
• digestive disease (ERR/Sv = 0.15, 95% CI 0.00 to 0.32)
44. A large study of Chernobyl emergency workers (Ivanov et al, 2000) showed a
significantly increased risk of cardiovascular disease. The ERR/Sv was 0.54 (95% CI 0.18
- 0.91), three times higher than the value from the atomic bomb survivors, although the
95% confidence intervals overlap, meaning that the two ERR values could be consistent
with one another.
(5) Heritable effects
45. It is well known that radiation can damage genes and chromosomes. The
relationship between genetic changes and the development of future disease is complex
however and the relevance of such damage to future risk is often unclear. We might
expect that parental exposure to radiation would produce an increased incidence of
inherited disease in the children of exposed individuals. Nevertheless no evidence of
increased genetic damage has yet appeared in the children of the Hiroshima and
Nagasaki survivors. This could be because the samples are not large enough to show a
statistically significant effect - in other words, there is insufficient statistical power. As a
result, estimates of genetic risk in humans are usually based on data from animal
experiments.
46. On the other hand, a number of recent studies have examined genetic damage in
those exposed to radiation from the Chernobyl accident. Some have examined changes in
minisatellites, which are sequences of repeated DNA particularly prone to mutations.
These are often used as markers for measuring the effects of low doses of radiation,
although whether such mutations affect the future health of those exposed is unknown.
Potentially important are changes in the DNA of eggs and sperm (collectively referred to
as germline DNA) as this DNA becomes incorporated into every cell in the children of the
exposed individuals.
47. Studies of the population of Mogilev province in Belarus have suggested a twofold
increase in the germline minisatellite mutation rate (Dubrova et al, 1996; Dubrova et al,
1997). Analysis of another cohort of irradiated families from Ukraine confirmed these
findings and showed that in both groups the observed increase was attributed to mutation
induction in exposed fathers but not mothers (Dubrova et al, 2002). In contrast to the
Belarus study which used non-irradiated families from the United Kingdom as the control
group, the Ukraine study used fully-matched controls and exposed groups of families.
Conversely, Livshits et al (2001) and Kiuru et al (2003) found exposure to radiation had no
significant effect on minisatellite mutations in the children of Chernobyl cleanup workers
compared with the children of control families from the Ukraine. However, Livshits et al did
find that the subgroup of children conceived either while their fathers were working at
Chernobyl or up to two months later had a higher frequency of mutations than children
conceived at least four months after their fathers had stopped working at the site. Slebos
et al (2004) also examined DNA from lymphocytes in the children of cleanup workers and
found no significant difference in mutation frequency between children conceived before
their father's exposure and those conceived after. They pointed out, however, that their
sample size was small giving the study low the statistical power.
48. Clearly this is a matter requiring further studies over longer time periods. Future
studies may indicate that this could be another area where established views about
radiation's effects may need to be revised.
58
(6) Mental Health and Psychosocial effects
49. The Chernobyl accident has had profound and far-reaching psychosocial effects.
The origins of these effects are complex, and are related to several factors, including:
• Anxiety about the possible effects of radiation, often leading to extreme
pessimism, depression, apathy and fatalism
• Changes in lifestyle, particularly diet, alcohol and tobacco
• Feelings of being a victim, leading to a sense of social exclusion and an
expectation of external support, including financial help and special medical
treatment
• Stress associated with evacuation and resettlement (see UNDP, 2002)
50. In a short report such as this it is difficult, if not impossible, to do justice to the scale
of these problems. Chapter 15 of the IAEA/WHO report (2005a) which describes the
mental, psychological and central nervous system effects of Chernobyl states:
"The mental health impact of Chernobyl is the largest public health problem caused by the accident
to date. The magnitude and scope of the disaster, the size of the affected population, and the long-
term consequences make it, by far, the worst industrial disaster on record. Chernobyl unleashed a
complex web of events and long-term difficulties, such as massive relocation, loss of economic
stability, and long-term threats to health in current and, possibly, future generations, that resulted in
an increased sense of anomie and diminished sense of physical and emotional balance. It may
never be possible to disentangle the multiple Chernobyl stressors from those following in its wake,
including the dissolution of the Soviet Union. However, the high levels of anxiety and medically
unexplained physical symptoms continue to this day. The studies also reveal the importance of
understanding the role of perceived threat to health in epidemiology studies of health effects."
"What the Chernobyl disaster has clearly demonstrated is the central role of information and how it is
communicated in the aftermath of radiation or toxicological incidents. Nuclear activities in Western
countries have also tended to be shrouded in secrecy. The Chernobyl experience has raised the
awareness among disaster planners and health authorities that the dissemination of timely and
accurate information by trusted leaders is of the greatest importance."
59
Annex 4. Radiation Dose Units
A measure of the effect of radiation is the amount of energy it deposits in unit mass of
body tissue. This quantity is called the absorbed dose. The unit of absorbed dose is the
gray (Gy). One gray is equal to the energy deposition of 1 joule in 1 kilogram of tissue.
The biological effects of alpha particles and neutrons (high LET43 radiation) are in general
much greater than the effects of beta particles and gamma rays (low LET radiation) of the
same energy. The Radiation Weighting Factor wR is introduced to take account of the
different biological effectiveness of alpha and beta particles, neutrons, X and gamma rays.
The quantity equivalent dose is then defined as: equivalent dose = absorbed dose x wR
The unit of equivalent dose is the sievert (Sv).
In studies of low dose radiation, the sievert is too large a unit and doses are usually given
in millisieverts (mSv) where 1 Sv = 1,000 mSv (see below)
For low LET radiation, wR = 1, so grays and sieverts will be numerically equivalent.
However, for alpha particles wR = 20, so an absorbed dose of 1 mGy produced by alpha
particles will have an equivalent dose of 20 mSv.
Systeme Internationale Nomenclature (commonly used units)
E = exa = 1018
P = peta = 1015
T = tera = 1012
G = giga (one billion) = 109
M = mega (one million) = 106
K = kilo (one thousand) = 103
c = centi (one hundredth) = 10-2
m = milli (one thousandth) = 10-3
µ = micro (one millionth) = 10-6
n = nano (one billionth) = 10-9
p = pico (one trillionth) = 10-12
Examples are
mSv = millisievert (one thousandth of a sievert) = 10-3 Sv
µSv = microsievert (one millionth of a sievert) = 10-6 Sv
nSv = nanosievert (one billionth of a sievert) = 10-9 Sv
43
LET= linear energy transfer, ie the energy transferred per unit length of the radiation track
60
Chapter 5. Collective Doses
Introduction
1. Radiation exposures are mainly measured in two ways: individual doses and collective
doses. As their names suggest, individual doses are per person: collective doses are the
sum of individual doses to all exposed persons in a defined area, for example a workforce,
a country, a region, or indeed the world. This may appear straightforward, but within many
governments, the nuclear industry and, to a lesser extent, within radiation protection
circles, there is a noticeable reluctance to use and discuss collective doses. For example,
although legal limits exist in most countries for individual doses, to our knowledge none
exists for collective doses. This means that few, if any, legal or administrative sanctions
exist against high collective doses. Also, of the ICRP's three main principles of justification,
optimisation and limitation (of radiation exposures), only the first two refer to collective
dose44.
2. This reluctance is partly due to the uncertainties involved, and partly due to the fact that
from a given collective dose one can estimate the numbers of future cancer deaths, which
some radiation protection authorities do not wish to emphasise. Despite this reluctance,
scientifically speaking a good case exists for using collective doses. This arises from
linear-no-threshold (LNT) hypothesis for radiation's effects. This theory predicts that
radiation's effects continue to exist even at very low doses, declining linearly with dose
without a threshold. That is, there is no dose below which effects do not occur. A corollary
of the LNT is that it is scientifically correct to estimate collective doses even where
individual doses are very low, for example below background radiation doses. This is
discussed in more detail in Annex 6A. The recent reports by the IAEA/WHO (2005a,
2005b) and UNSCEAR (2000) give short shrift to collective doses particularly when
individual doses are low.
3. This chapter discusses collective dose estimates made by official studies for Belarus,
Ukraine and Russia; the rest of Europe; the rest of the world; and total global doses. We
shall also make an estimate for collective doses from very long-lived nuclides including C-
14 and I-129.
4. Collective doses are estimated by assessing the average doses to populations
exposed to radiation. Such dose assessments take into account
• deposition densities of Cs-137 and other nuclides
• population numbers in affected areas
• estimates of average external dose from deposited nuclides
• estimates of average internal dose from ingestion and inhalation of nuclides
• habits and diets of affected populations (in some reports), and
• conversion factors from Gy to Sv (from organ doses to whole body doses)
5. It is necessary to identify clearly the time periods over which a collective dose is
estimated. For example, the exposed populations in Belarus, Ukraine and Russia received
approximately one third of their collective dose in the first year after Chernobyl.
Approximately another third was received in the next nine years (ie 1987 to 1996), and
44
in the 1980s and 1990s, the ICRP (without informing the public) debated the issue of collective dose, but
was unable to agree on recommending a limit.
61
about another third will be received between 1997 and 2056, ie 70 years after Chernobyl.
Unfortunately, time periods are missing, glossed over or left to footnotes in some official
reports. In other reports, no consistency exists: one year, 10 years, 20 years and 70 years
are variously used. This is unscientific as it makes proper comparisons very difficult and is
indicative of the poor attitude towards collective dose in official reports.
6. No greater time periods than 70 years are used, to our knowledge. This limitation to 70
years (the so-called lifetime period) is illogical as collective doses will continue to arise
from Cs-137 exposures well into the next century and beyond. A 300 year period (ie 10
halflives of Cs-137) would be more relevant, but such a period does not appear in the
literature on Chernobyl we have examined.
A. Collective Dose Estimates for Belarus, Ukraine and Russia
7. The report prepared by Cardis et al (1996) for the IAEA/WHO Conference in 1996 on
the 10th anniversary of Chernobyl contained the following table reproduced below
Table 5.1 Estimates of Collective Effective Doses to 1996 in Belarus, Ukraine and
Russia by Cardis et al, 1996
Population Number Collective effective
dose(a) (person Sv)
Liquidators (1986-1987) 200,000 20,000
Evacuees 135,000 1,600
Persons living in contaminated areas
Cs-137 > 555 kBq/m2 270,000
10,000 - 20,000
Persons living in contaminated areas
Cs-137 > 37-555 kBq/m2 6,800,000
35,000 -100,000
Total 7,405,000 67,000 - 140,000
(a) These doses are for 1986-1995; over the longer term (1996-2056), the collective dose will
increase by approximately 50% (footnote in original)
In view of the Cardis et al' advice to increase the collective dose by 50%, we do this below
Total 7,405,000 100,000 - 210,000
source: Cardis et al (1996)
8. Table 5.2 compares estimates of collective doses in Belarus, Ukraine and Russia
reports by national and international agencies and others including Cardis et al (1996).
Table 5.2 Estimated Collective Doses in Belarus, Ukraine and Russia
Study Collective effective
dose - Person Sv Exposure period
US DoE (Anspaugh et al, 1988) 326,000* 50 years
UNSCEAR 1988 (Bennett 1995,1996) 216,000 to 2056
Cardis et al (1996) table 5.1 using footnote 100,000 - 210,000 to 2056
Malko (1998a) 165,000 lifetime
Ukraine Government (2001) 58,000 (Ukraine) 2056
IAEA/WHO (2005b) 55,000 2006
* (person Gy)
9. The IAEA/WHO's collective dose assessment of 55,000 person Sv is the lowest
estimate by some margin: it is considerably lower than the estimates by Cardis et al
presented to the IAEA/WHO 1996 conference and shown in table 5.1. It is lower than the
62
Ukrainian Government's estimate for Ukraine alone. Note that the IAEA/WHO estimate is
only to 2006 and they make no estimate for future doses, unlike the other studies. The
studies by Cardis et al (1996), Malko (1998) and Bennett (1995, 1996) were
comprehensive using the latest available data. It is difficult to understand the IAEA/WHO's
decision not to include these estimates in their report to the 2005 Conference. The studies
by Bennett in particular are relevant: his methodology is set out in Annex 5A.
B. Collective Doses in the Rest of Europe
10. Estimates for collective doses in the rest of Europe are set out in table 5.3. More
detailed country by country estimates are contained in Annex 5B.
Table 5.3 Collective dose estimates for Europe (excluding Belarus, Ukraine and
Russia)
Study Collective Dose
person Sv Period
US DoE (Anspaugh et al,
1988) 580,000 50 years
UNSCEAR, 1988
(Bennett 1995,1996) 318,000 to 2056
OECD/NEA, 1996 68,000 in first year
11. The OECD/NEA estimate is only for the first year (ie 1986 to 1987) in which only about
30% of the collective dose would have been received. To obtain a proper estimate to
2056, we need to increase this value by a factor of about 3.4:.
OECD/NEA, 1996 ~230,000
(ie 68,000 x 3.4) to 2056
12. The OECD/NEA estimate should be treated as a minimum as it excludes non-OECD
countries, including Bulgaria, Rumania and Yugoslavia that are known to have received
large depositions of Chernobyl fallout. It is not possible to make an estimate of the
collective doses in these countries, as information on the populations affected by the
Chernobyl depositions is not available. However, their collective doses may have been
relatively large.
C. Collective Doses in the Rest of the World (excluding the whole of Europe)
13. Bennett (1995) estimates a collective dose commitment of 66,000 person Sv and
Anspaugh et al (1988) 28,000 person Sv to all areas of the world outside Europe. In order
to check these estimates, we make an order-of-magnitude estimate from the following
assumptions
• population of the Northern Hemisphere
(less population in Belarus, Ukraine and Russia and rest of Europe) = 4 x 109
• Average Cs-137 deposition density throughout northern hemisphere
(from 4x 1016 Bq Cs-137/surface area of 2.45 x 1014 m2)
(Bennett (1996) cites range of 1,000 kBq/m2 to 0.01 kBq/m2) = 0.16 kBq/m2
• Average external dose from Cs-137 density of 1 kBq/m2 1986-2056
(from table 3A (ii), Annex 3A) = 90 µSv
63
• Therefore average external dose from Cs-137 density of 0.16 kBq/m2 =14µSv
• Add contribution from other nuclides (30% of Cs-137 dose) = 4 µSv
• Add contribution from internal doses
(50% of external dose - see Annex 3A, table 3A(iii)) = 7 µSv
___________________________________________________________________
Total average dose 1986-2056 per person = 25 µSv
Therefore the estimated collective dose = 4 x 109 x 25 Sv-6 person Sv which is ~100,000
Person Sv and which is not far from Bennett's estimate of 66,000 person Sv.
D. Global Collective Doses
14. Table 5.4 sums the contributions from sections A to C above.
Table 5.4 Total Collective Doses from Chernobyl Discharges- person Sv
Area US DoE
Anspaugh
et al
(1988)*
UNSCEAR
Bennett
(1995,
1996)
OECD/NEA
(1996) Cardis et
al (1996) Malko
(1998) IAEA/WHO
(2005b)
Belarus,
Ukraine
and Russia
326,000 216,000 - 100,000 -
210,000** 165,000 55,000
Rest of
Europe 580,000 318,000 230,000*** - - -
Rest of
World 28,000 66,000 - - - -
TOTAL 930,000 600,000 - - - -
* person Gy
** see table 5.1
*** see paragraph 11 of this chapter
15. The earlier study by Anspaugh et al estimated a collective dose of 930,000 person Gy
(approximately the same as 930,000 person Sv) on the basis of environmental data
available at the time and the use of early dose assessment and risk models. Bennett's
estimate of 600,000 person Sv is probably more reliable, as UNSCEAR had access to
more data and more recent data.
16. The collective dose estimates described above are not mentioned in the UNSCEAR
(2000) or the IAEA/WHO (2005b) reports. We consider that some explanation for this
omission should be given, particularly as Bennett himself was the Scientific Secretary of
UNSCEAR until the late 1990s, and was Chairman of the September 2005 IAEA/WHO
Conference. His estimates were regularly cited in official reports in the 1980s and 1990s
until about 1996. From this examination of collective dose estimates, it is clear that
Bennett's estimates are reliable and his studies still relevant.
Collective Doses From Long-Lived Nuclides
17. The worldwide distribution of some nuclides with long half-lives result in small
exposures to the population of the world (~6 billion people) for many years into the future.
This matter is not considered by any of the above studies therefore an estimate is made
below in table 5.5. Releases of Cl-36 and Tc-99, two other globally distributed nuclides
with very long half-lives, are unknown but should be added. Global dose coefficients
(person Sv/TBq) rounded to two significant figures were obtained from Simmonds et al
64
(1996) and Mayall et al (1993). Estimated nuclide releases are from Kirchner and Noack
(1988) and UNSCEAR (2000).
Table 5.5 Collective doses from long-lived nuclides
Nuclide Half-life
(years) Estimated
Release (TBq) Global Dose Coefficient
(Person Sv per TBq
released to air)
Collective
dose Person
Sv
C-14 5,740 100 110 11,000
I-129 15,700,000 0.08 9,500 760
Kr-85 10.7 33,000 0.004 130
H-3 12.3 1,400 0.002 2.8
Total 12,000
18. The result of 12,000 person Sv is relatively small in comparison with the above
collective dose estimates of 600,000 and 930,000 person Sv respectively by Bennett and
Anspaugh et al. But it should be kept in mind when considering predictions of excess
cancer deaths.
Comparison with other Releases
19. Bennett (1995) compared the collective dose from Chernobyl's fallout with the
collective doses from other man-made releases. These are set out in table 5.6. It can be
seen from this table that the Chernobyl accident certainly is the most serious nuclear
accident. Indeed the fallout from Chernobyl is second only to the fallout from the hundreds
of atomic test bombs detonated above ground in the 1950s and 1960s.
Table 5.6 Committed Collective Doses from Man-Made Radionuclide Releases
Release Collective Effective dose
person Sv
Atomic test bombs (in atmosphere) 1950s and
1960s 30,000,000
Chernobyl accident USSR 1986 600,000
Nuclear power production (to 1995) 400,000
Radioisotope production and use (to 1995) 80,000
Nuclear weapons fabrication (to 1995) 60,000
Kyshtym accident USSR 1957 2,500
Windscale accident UK 1957 2,000
source: Bennett (1996)
65
Annex 5A. Bennett's Study
(i) Bennett (1995, 1996) and UNSCEAR (1988, 1994) arrived at their estimates by
using a Cs-137 deposition vs distance relationship to make dose estimates for the
northern hemisphere of the world. Based on Cs-137 deposition estimates in all areas of
the northern hemisphere (derived from his deposition-distance relationship and transfer
factors relevant for the latitudinal area), he derived effective dose commitments for all
regions. These doses multiplied by the populations of the regions give the collective
effective dose commitments.
(ii) Bennett stated that a general decrease of radionuclide deposition with distance
from the release site could be expected, with variability due to wind and rainfall
differences. In the Chernobyl accident, the release continued for ten days and the wind
changed to all directions. Therefore some variability was averaged out and Bennett
observed a relatively uniform decrease in Cs-137 deposition with distance to the capital
cities or the approximate population centres of the relevant countries. A log-log plot of
average Cs-137deposition in countries outside the USSR was made of Cs-137
measurements with distances from the accident site. This allowed Bennett to determine an
approximate deposition-distance relationship ranging from about 10 kBq/m2 at 1,000 km to
~ 0.01 kBq/m2 at 10,000 km. With this relationship, Cs-137 deposition densities were
estimated in all regions of the northern hemisphere where measurements were
unavailable.
(iii) Bennett estimated that the total collective dose from the Chernobyl accident was
600,000 person Sv, distributed 53% to European countries, 36% to the former USSR, and
the remaining 11 % to the rest of the northern hemisphere. The calculations indicated that
70% of the collective dose was due to Cs-137, 20% to Cs-134, 6% to I-131 and the
remaining 4% to short-lived radionuclides deposited immediately after the accident. The
lifetime dose on average was approximately 60% from external irradiation and 40% from
ingestion. According to Bennett, approximately one third of the 600,000 man Sv total
effective dose committed by the accident was received during the first year following the
accident. The remainder would be delivered over "some tens of years", mainly determined
by the 30 year half-life of Cs-137.
66
Annex 5B. Collective Dose Estimates in European countries
(i) Table 5C(i) sets out collective dose estimates in European countries by the UK NRPB45,
the US DoE, and the OECD/NEA.
Table 5C(i) Collective Doses to European Countries. Person-Sv
Country Population
millions NRPB, 1987
(all time) DoE, 1987
(50 years) OECD/NEA, 1996
(first year)
Albania - - - -
Austria 7.4 - - 4,900
Belgium 10 940 880 400
Bulgaria - - - -
Czechoslovakia - - - -
Denmark 5.2 1,100 820 140
Finland 4.9 - - 2,500
France 55 5,600 12,000 1,300
East Germany - - - -
West Germany 61 30,000 58,000 18,000
Greece 9.8 8,500 4,700 3,600
Hungary - - - -
Ireland 3.5 950 1,800 370
Italy 56.6 27,000 52,000 28,000
Luxembourg 0.37 42 76 45
Netherlands 14.5 1,200 3,400 950
Norway 4.2 - - 700
Poland - - - -
Portugal 9.3 2.3 low 58
Rumania - - - -
Spain 37.7 57 low -
Sweden 8.3 - - 1,700
Switzerland 6.5 - - 1,400
Turkey 52 - - 830
UK 56.6 1,000 15,000 2,100
Yugoslavia - - - -
TOTAL 400 78,000 149,000 67,000
(ii) These estimates are difficult to compare as different studies exclude different countries
and apply to different time periods. The OECD study which was prepared by an NEA
committee of national experts is considered to be relatively reliable. Nevertheless, it only
presents an estimate for the first year after Chernobyl, during which only about 30% of the
collective dose occurs, Therefore it is necessary to increase the total 3.4 fold to extend the
doses until 2056. This would result in a European collective dose of about 230,000 person
Sv.
45
Formerly the UK National Radiological Protection Board, now subsumed within the UK Health Protection
Agency- Radiation Protection
67
Chapter 6. Predicted Excess Cancer Deaths
1. An estimate of the number of world-wide cancer deaths may be made from the
estimates of collective doses in the previous chapter. The scientific justification and the
method for this procedure are set out in Annex 6A.
Predictions for Belarus, Ukraine and Russia
2. IAEA/WHO (2005a) reported the following numbers of predicted excess cancer deaths
in table 16.4 of its report.
Table 6.1 Predicted Excess Cancer Deaths in Belarus, Ukraine and Russia (from
lifetime exposures of 95 years)
Population Number Average
dose Sv Cancer type Predicted excess
cancer deaths
solid cancers 2,000
Liquidators
(1986-87) 200,000 0.1 leukaemias 200
solid cancers 150
Evacuees from 30
km zone 135,000 0.01 leukaemias 10
solid cancers 1,500
Residents of SCZs 270,000 0.05
leukaemias 100
solid cancers 4,600
Residents of other
contamin areas 6,800,000 0.007 leukaemias 370
Totals 7,405,000 8,930
source: table 16.4 in IAEA/WHO (2005a)
3. This table gives fairly detailed estimates of expected cancer deaths in Belarus, Ukraine
and Russia expressed over a lifetime. These estimates were previously reported in 1996
(IAEA/WHO) but they were apparently not mentioned in the IAEA Press briefings and not
commented upon in the media at the time. In September 2005, some of these data were
mentioned in the IAEA Press Release (2005c) issued at the IAEA/WHO conference on
Chernobyl. The IAEA Press Release stated that 4,000 excess cancer deaths were
expected. It is considered that this statement was being "economical" with the data in table
6.1 above. It would appear that the IAEA decided to refer only to the expected deaths
among those who received higher doses, ie the liquidators and residents of Severely
Contaminated Zones (SCZs). The other lower dose categories were ignored. At the least,
this is a manipulative use of data. At worst, it is a misleading use of data, as the real figure
- as can be seen above - is nearly 9,000 excess cancer deaths.
Global Predictions of Excess Cancer Deaths
4. If we assume that the linear no-threshold hypothesis of radiation's effects is correct, we
may apply a risk factor46 to the collective doses cited in Chapter 5 to derive predictions of
the excess cancer deaths that will result from Chernobyl exposures. Table 6.2 sets out the
predictions by various international studies of the numbers of excess cancer deaths from
Chernobyl. Uncertainties inevitably surround these estimates, but they serve to indicate
the probable magnitude of the effects of the Chernobyl disaster. They are our best
46
expressed in cancer deaths per sievert. 5% per Sv means that if 100 people were each exposed to 1 Sv of
radiation, there would be 5 excess deaths from radiation-induced cancer
68
estimates given the currently available information, although few of these excess deaths
are likely to be discernible by epidemiology studies.
Table 6.2 Predicted Excess Cancer Deaths from Exposure to Chernobyl Discharges
Study Population Risk factor used
Per Sv Excess
cancer
deaths
IAEA/WHO Press
Release (2005c) Belarus, Ukraine
and Russia assumed to be 5% 4,000
Cardis et al, 1996 Belarus, Ukraine
and Russia 11% inferred from data ~9,000
Malko (1998) Belarus, Ukraine
and Russia 13% inferred from data 22,000
Rytomaa (1996) World 5% inferred from data 30,000
US DoE
(Goldman, 1987) World ~3% 28,000
US-NRC, 1987 World ~1.5% inferred from data 14,000
UNSCEAR 1988
(Bennett, 1996) World 5% 30,000
in greyed cells, prediction is calculated by this report (ie 5% of 600,000 person Sv)
5. The figure of 4,000 reported in the IAEA/WHO Press Release (2005c) at the
IAEA/WHO Conference on Chernobyl held in Vienna in September 2005 is the lowest
value of predicted excess fatal cancers in table 6.2. In terms of good scientific practice, it
would have been preferable for the IAEA/WHO report to place its estimate in the context of
other published predictions of excess cancer deaths.
Radiation Risk Estimates and DDREFs
6. Table 6.2 indicates that various authors use different radiation risk estimates to predict
the numbers of excess fatal cancers. The current ICRP recommendation (ICRP, 1991) is
to apply an average risk factor (over all populations, ages and sexes) of 5% per Sv for fatal
cancers. This risk figure comes from studies of the Japanese atomic bomb survivors.
However, the risk factor from Japan47 is halved because the ICRP takes the view that
radiation at low doses and low dose rates (like that from Chernobyl fallout) is less
dangerous than high dose, high dose rate radiation (like that from the atomic bomb blast).
In scientific jargon, this is known as applying a dose and dose-rate effectiveness factor
(DDREF) of 2.
7. The ICRP's rationale has been that animal and cell studies show low doses of radiation
at low dose rates to be less damaging than high doses at high rates. However, the BEIR
VII Committee of the US National Academy of Sciences on ionising radiation has taken a
different view of the evidence. Its recent report (BEIR, 2005) recommends that a median48
DDREF of 1.5 rather than 2 should be used for solid cancers. This in turn suggests that
the correct risk factor for most cancers should be increased from 5% to about 7% per Sv.
47
the most recent estimate from the atomic bomb survivors (Preston et al, 2003) is an average of 12% per
Sv
48
with a range of 1.1 to 2.3
69
8. As regards DDREFs, it is notable that the US EPA (1994) has not used a DDREF for
breast and thyroid cancers for many years. Also, an increasing number of scientists (for
example Cardis et al, 1996; Malko,1998) refrain from using a DDREF factor, partly49
because the supporting evidence for their use are animal and cell studies and not human
epidemiology studies. Indeed, two recent epidemiology studies (Cardis et al, 2005b;
Krestinina et al, 2005) indicate the opposite, ie that exposures to protracted radiation might
be more not less damaging (as regards cancer induction) than high dose-rate exposures
by as much as 2.5 times. This matter is the subject of continuing discussion in radiation
protection circles.
9. In view of these matters, we consider that the inappropriate use of DDREFs may well
lead to inaccurate estimates of future cancer deaths. For this reason, we set out in table
6.3 a range of estimated excess cancer deaths using reasonable risk factors derived from
different values for DDREF and from not using a DDREF.
Table 6.3 Predicted Excess Cancer Deaths from Exposure to Chernobyl Discharges
Study Population Risk factor used Excess
cancer
deaths
UNSCEAR 1988
(Bennett, 1996) World 10% per Sv
(using no DDREF) 60,000
UNSCEAR 1988
(Bennett, 1996) World 6.7% per Sv
(using BEIR DDREF of 1.5) 40,000
UNSCEAR 1988
(Bennett, 1996) World 5% per Sv
(using ICRP DDREF of 2) 30,000
greyed cells = calculated by this report from data in Bennett, 1996
10. In table 6.3, we derive three predictions of excess cancer deaths, and our best
estimate lies in the range 30,000 to 60,000. Although our predictions are higher than other
estimates of predicted excess cancer deaths by Goldman (1987) and Rytomaa (1996) -
see table 6.2, they have been derived using a simple scientific procedure. If future studies
were to confirm that a DDREF should not be applied (ie that the Japanese risk estimates
should not be divided by any figure), then the higher figure of our estimated range would
be applicable. If future epidemiology studies were to go further and indicate that protracted
radiation might be more rather than less damaging (as regards cancer induction) than high
dose-rate exposures, then the above estimates would need to be increased still further.
Inappropriate Comparisons with Background Radiation
11. Official reports (eg IAEA/WHO, 2005a) often compare the numbers of expected excess
cancer deaths with the much larger numbers of cancer deaths expected from background
radiation over the same time period. In our view, such comparisons are inappropriate, as
they conflate man-made radiation with naturally-occurring radiation. They may also be
misleading because they invite the uninformed public to infer that background radiation is
somehow "safe". In reality, background radiation is a killer. For example, the former UK
NRPB has calculated that an average background dose rate of 2.6 mSv/a in the UK
population results on average in about 6,000 to 7,000 future cancer deaths per year (Robb
1994). This matter is explored further in Annex 6B.
49
also because the use of DDREFs is inconsistent with the accepted practice of extrapolating risks linearly
from data at high doses to low doses
70
Annex 6A. Collective Dose and the Linear No-Threshold Theory
(i) Epidemiology evidence exists of an excess risk of radiation-induced cancer at doses at
least as low as 10-50 mSv and that this risk is directly proportional to dose. The latest
study of cancer in nuclear industry workers (Cardis, 2005c), in which the overall average
cumulative recorded dose was 19.4 mSv, suggest, according to the authors that ‘an
excess risk of cancer exists, albeit small, even at the low doses and dose rates typically
received by nuclear workers in this study'. The most recent follow-up of the Hiroshima and
Nagasaki survivors (Preston et al, 2003) shows that ‘the excess solid cancer risks appear
to be linear in dose even for doses in the 0-150 mSv range'. In the particular case of
thyroid cancer, there is evidence that the risk is directly proportional to dose, down to
doses as low as 10 mSv (Ron et al, 1995).
(ii) However, at doses of a few mSv or lower, risks have to be inferred by extrapolation
from higher doses, as epidemiology studies would require unfeasibly large numbers of
people to be studied to achieve adequate statistical power. Radiobiology can help here:
because the transformation of a cell to a pre-cancerous state may result from the lowest
possible dose of radiation - a single radiation track traversing a single cell nucleus - good
reasons exist for supposing that the risk is directly proportional to dose right down to zero,
i.e. there is no-threshold (NRPB, 1995; Stather, 1995).
(iii) The ICRP's view (2004) is that the LNT relationship should be used as it provided a
"conservative" estimate of risks. The word "conservative" has a special meaning in
radiation protection. It means that because, in the ICRP's view, the real risk is likely to be
lower, acting on the higher risk estimate gives an added safety margin. Recently, an
eminent group of the world's foremost radiobiologists re-affirmed the LNT and stated that it
provided a real estimate of radiation risks and not a "conservative" one (Brenner et al,
2003).
(iv) Assuming the risk of cancer is directly proportional to dose with no threshold, it follows
that the number of cancer deaths can be estimated as follows:
• number of cancer deaths = number of people exposed x average dose (Sv) x risk
factor (cancer deaths per Sv)
• the product (numbers exposed x average dose) is the collective dose, so
• predicted number of excess cancer deaths = collective dose x risk factor
(v) More detailed discussions of collective dose are contained in Fairlie and Sumner
(2000) and Sumner and Gilmour (1995), and of the biological justification for the LNT in
Brenner et al (2003).
71
Annex 6B. Inappropriate Comparisons with Background Radiation
(i) Offical reports often compare collective doses from man-made radiation with the much
larger collective doses received from background radiation, in attempts to put them "in
context". Such comparisons invite the public to conclude that, because doses from man-
made radiation are smaller than those from background radiation, they are therefore
acceptable. Many objections can be made against these assertions.
(ii) First, comparisons with natural background doses invite the inference that background
radiation is "safe". This is not the case, of course: background radiation is a killer. For
example, the former UK NRPB has calculated, using a 5% per Sv risk factor, that an
average UK background dose rate of 2.6 mSv per year in a population of 55 million will
result on average in about 6,000 to 7,000 future cancer deaths per year, about 4% to 5%
of the 160,000 cancer deaths occurring each year in the UK (Robb, 1994).
(iii) Second, comparisons with background radiation conflate different risks, ie naturally-
occurring and anthropogenic risks. Risks from anthropogenic releases are (or were in the
case of past exposures) subject to by social and political decisions. Risks from
background radiation are not.
(iv) Third, it is notable that comparisons with background are not used to justify the
acceptability of industrial discharges of chemical toxins that also occur naturally, such as
aflatoxin, ozone or dioxin.
(v) Finally, and notably, the current ICRP system of radiation protection of limitation,
optimisation and justification (ICRP, 1991) notably does not use comparisons with natural
background radiation as a criterion of radiological acceptance. This is a deliberate
omission, as the issue of using background radiation has often been discussed at ICRP
committee meetings. In recent years, the past chairman of the ICRP had attempted to
jettison the ICRP's principles and to introduce background radiation as a criterion of
acceptance. These attempts failed as they were not supported during the ICRP's
consultations on updating its 1991 recommendations which took place in 2004. Indeed, in
the past, many scientists have stated (NRPB, 1990), (Webb et al, 1983), (section 8.3.4 in
Bush et al, 1984) that comparisons of radiation exposures from anthropogenic releases
with natural background radiation are inappropriate.
72
Chapter 7. Conclusions
1. It is widely agreed that the Chernobyl disaster was unprecedented and unique in
the history of civil nuclear power. Its effects are clearly still occurring and the full
consequences may take centuries to unfold. Even then, it is likely that many details will
never be known.
2. The main conclusions of our report are
• about 30,000 to 60,000 excess cancer deaths are predicted, 7 to 15 times greater
than IAEA/WHO's published estimate of 4,000
• predictions of excess cancer deaths strongly depend on the risk factor used
• predicted excess cases of thyroid cancer range between18,000 and 66,000 in Belarus
alone depending on the risk projection model used
• other solid cancers with long latency periods are beginning to appear 20 years after
the accident
• Belarus, Ukraine and Russia were heavily contaminated, but more than half of
Chernobyl's fallout was deposited outside these countries
• fallout from Chernobyl contaminated about 40% of Europe's surface area
• collective dose is estimated to be about 600,000 person Sv, more than 10 times
greater than official estimates
• about 2/3rds of Chernobyl's collective dose was distributed to populations outside
Belarus, Ukraine and Russia, especially to western Europe
• Cs-137 released from Chernobyl is estimated to be about a third higher than official
estimates
Recent IAEA/WHO studies
3. Our verdict on the two recent IAEA/WHO (2005a, 2005b) studies on health and
environment respectively is mixed. On the one hand, we recognise that the reports
comprehensively examine Chernobyl's effects in Belarus, Ukraine and Russia. They
contain a great deal of important information which will repay future study. Clearly much
scientific effort was put into the reports by the respective scientific teams and their
chairpersons, and they are welcomed for this reason.
4. On the other hand, the reports contain some deficiencies, for example the lack of
discussion on Chernobyl's source term and the low estimates of collective dose in Belarus,
Ukraine and Russia. Significantly they are silent50 on Chernobyl's effects outside Belarus,
Ukraine and Russia. Most of Chernobyl's fallout was deposited outside these countries.
Countries in the rest of the world, especially in Europe, will suffer twice as many predicted
excess cancer deaths (and collective doses) as Belarus, Ukraine and Russia.
5. We recognise that the failure to examine Chernobyl's effects in all other countries
does not lie with the scientific teams but with higher echelons of the IAEA and the WHO.
We recommend that the WHO, independently of the IAEA, should now commission a
report to examine Chernobyl's effects in all other countries in order to rectify the omission.
50
except for one table on Cs-137 contaminatio n levels in a few Europeam countries
73
We also recommend that UNSCEAR, presently located within the IAEA's headquarters in
Vienna, should be relocated to a more neutral venue.
Uncertainties
6. As we have shown in this report, the reconstruction of the accident and the
prediction of its health consequences involve many uncertainties: in the size of the source
term, the distribution of fallout, the relationship of contamination to doses received, and the
estimation of health effects from radiation doses. To estimate the likely effects, value
judgements have to be made; values of various parameters have to be assumed when we
use models; and some assumptions may be arbitrary. This is particularly the case with
predictions of excess cancer deaths from Chernobyl's collective doses. These strongly
depend on the risk factor used, but divergent views exist on what is the correct factor. Up
to a few years ago, 5% per Sv was widely used: nowadays 10% per Sv or more is
increasingly used. This obviously results in increased numbers of predicted excess cancer
deaths, therefore close scrutiny of the risk factor used is needed.
7. As a result, many of the doses, predicted effects and risks we cite in this report will
be subject to considerable uncertainties. We draw attention to these uncertainties and
recommend that a precautionary approach be adopted when using them.
Scientific Lessons
8. Many lessons are still being learned from Chernobyl. Some of them should already
be part of the scientific approach, but at the risk of stating the obvious, we set them out
below
(i) We must not jump to conclusions, especially about the absence of radiation
effects with long latency periods. The studies published so far have follow-up
periods that are smaller than the typical latency periods for solid cancers
induced by radiation. Many studies are still in progress, and their results are
awaited. For example, the follow-up studies of the atomic bomb survivors, which
have now continued for more than 60 years, are still yielding new, and
sometimes surprising, information.
(ii) Many years ago, a British politician, Oliver Cromwell, stated: "Always think it
possible that thou art mistaken". It has now been shown that the initial
scepticism that greeted the first reports of childhood thyroid cancer from
Chernobyl was unjustified. This should make us more careful about deciding
what is and what is not a radiation effect. In other words, we need to keep a very
open mind on Chernobyl's effects.
(iii) "Absence of evidence is not evidence of absence" (Altman and Bland, 1995). A
real effect can elude detection because of low statistical power, often because
the samples are too small. The lack of statistical power is a recurrent theme in
many of the studies published so far.
The Future
9. As for the future, we recommend that follow-up studies are continued and
broadened, with satisfactory funding and the involvement of independent scientists. A
good model in this respect is the Radiation Effects Research Foundation (RERF) in Japan,
74
which continues to follow-up effects in the atomic bomb survivors and whose funding is
independently secured. In this connection, we note the apparent lack of independence in
the relations between the WHO and the IAEA as regards the WHO's studies on Chernobyl
effects. The WHO should be able to carry out health-related research and publish health
reports on radiation matters independently of the IAEA, just as other UN agencies publish
reports independently of each other. In our view, there is no reason why the WHO alone
should not investigate these matters and publish its results without the permission of the
IAEA.
10. Collaborative work is sometimes limited by the inability of Western scientists to gain
access to, and/or translate, many scientific reports written in Ukrainian and Russian.
These language constraints inhibit a full understanding of the impacts of Chernobyl; we
draw attention to this difficulty and to the need for it to be tackled at an official level. In the
past, laudable attempts have been made with this aim (Shershakov and Kelly, 1996) but
translations of more recent reports are needed.
11. Finally, there remains the question of the future of nuclear power. A number of
countries are currently considering the renewal and/or enlargement of their nuclear power
programmes. Chernobyl should give us all pause for thought before we embark on any
revival of nuclear power. Even though future reactors have been stated to be inherently
safer than the Chernobyl design, accidents can still occur and it is important that robust
plans are agreed internationally for dealing with any future accidents (see Williams, 2001).
We should keep in mind the view of the philosopher George Santayana that those who are
unable to learn from history are condemned to repeat it.
75
Afterword
THE CURRENT SITUATION IN UKRAINE: February 2006
Professor A. NYAGU
President of "Physicians of Chernobyl" Association
8, Chernovol str.
Kiev 01135
Ukraine
The radiation accident at Chernobyl in April 1986 is still affecting the lives of many people
in Ukraine and is still determining its national economic policy. There are many problems
in Ukraine resulting from radio-ecological Chernobyl catastrophe including:
• the remaining reactors at Chernobyl which are currently closed;
• the "Shelter" and its reconstruction;
• the exclusion zone and radioactive waste - there are more than 800 temporary
storage places for radioactive wastes containing about 300,000 Ci (Cs), 12,000 Ci
(Sr) and 300 Ci (Pu) and about 110,000 Ci (Cs), 44,000 Ci (Sr) and 110 Ci (Pu) in
permanent stores (7);
• the radioecological monitoring of 4.8% of the surface area of Ukraine (including
2,300 settlements);
• the radiological monitoring the Dneiper river water basin, which provides water for
32 million people and for the irrigation of 1.8 million hectares of land;
• the health monitoring of over 2,646,000 citizens, including 643,000 children, who
received acute radiation doses during the accident and are still exposed to low
doses of radiation in the contaminated territories;
• the social protection of these citizens and personnel of the Chernobyl nuclear
plant, including residents of Slavutich town.
As a result of the accident, 2,300 settlements in 12 Ukraine Oblasts were exposed to
radioactive contamination. This corresponds to 55,000 km2 including some 25,000 km2 of
forests. In addition, in 1986, 91,000 people were evacuated from the 30 km exclusion zone
around Chernobyl. Where Cs-137 contamination levels exceeded 555 kBq/m2, (ie II zone),
compulsory evacuation was required in Ukraine. These contamination levels were
estimated to result in an annual exposure of >5 mSv, five times greater than the legal limit.
The radiation dose criteria for the zone of guaranteed settlement (III zone) is 1 to 5 mSv
and for the zone of strengthened ecological control (IV zone) is 0.1 to 0.5 mSv. The lesser
contaminated zones III and IV are presently used for agricultural production. The
Chernobyl accident stopped traditional methods of forestry engineering. There is now a
need to introduce new technologies and new work equipment to be used in conditions of
radioactive contamination (2, 3, 7).
Ukrainian experts estimate the economic damage to Ukraine will be $200 billion up to
2015 (7, 9). In comparison, Ukraine's GDP in 2001 was $37 billion. In 1992, Ukraine spent
15% of its entire budget dealing with the effects of Chernobyl. In 1996, the figure was 6%,
and in recent years it has been 5% (4, 9).
The radiation exposures to the Chernobyl liquidators ranged between 50 mSv and 7 Sv.(1)
Evacuated people from the 30 km exclusion zone received exposures between 10mSv
and >700 mSv. People in contaminated areas in Ukraine, by conservative calculations,
76
received exposures between 2 to 74 mSv (1, 4). Their total accumulated collective dose
amounts to 46,000 man/Sv. The International Chernobyl project (1991) expected that the
average exposure to those in contaminated areas during 70 years (1986-2056) will amount
to 160 mSv. This means that the Ukraine population in contaminated areas will continue to
be exposed to radiation for many years. About 80-95% of radiation doses are from the
consumption of contaminated food (milk, meat, vegetables, forest products), and the
remainder is from external radiation - primarily surface Cs-137.
In accordance with the Law of Ukraine on "Status and Social Protection of Citizens
Affected by Chernobyl Catastrophe," about 7% of Ukraine's population was affected by
Chernobyl, not including the citizens of Kiev (although they were also irradiated). By 2005,
this amounted to 2, 646, 000 citizens, including (9):
• 165,000 residents of evacuated areas
• 253,000 liquidators
• 643,000 children born to the accident liquidators, and
• 1,563,000 people from 2, 293 settlements in contaminated areas
9, 500 people in 1,337 families still remain in zones of compulsory evacuation. For these
people, life is very difficult and amounts to a humanitarian catastrophe. They lack all
infrastructure, all services, the right for land use, and all medical care. They are subject to
very high exposures from radioactive contamination. Most young families abandoned
these lands independently without assistance and a dramatic ageing of the population took
place.
In 2004, more than 2,320,000 Chernobyl survivors continued to receive periodic medical
examinations. The Ukraine National Registry system has registered all Chernobyl
survivors and has commenced automatic long-term health monitoring. By January 2005,
the Registry had compiled information on 2,240,000 persons. The percentage of the adult
population diagnosed ill after medical examination, is constantly growing. At present, 94%
of accident liquidators, 89% of evacuees; 85% of residents of radioactively contaminated
territories, and 79% of children directly or indirectly affected by the accident are officially
considered ill under the Ukraine National Registry. These indices, although very large,
could in fact be worse if screening were carried out thoroughly. But there is neither the
finance nor political will for thorough screening in Ukraine.
According to the dose distribution in the Ukrainian population in 1986, thyroid exposures in
children were distributed as follows (7, 12):
• ~85% of all children < 3 years old and children irradiated in utero received
between 0.1 and 1 Gy;
• about 60% of children 4-15 year old and 50% of teenagers received between 50-
300 mGy;
• >15, 000 children born between 1979-1986 before the accident received more
than 2 Gy.
By January 2005, 3,270 patients had been operated on for thyroid cancer in Ukraine (9).
Children from 17,000 communities (ie 60% of all communities of Ukraine) received thyroid
doses greater than the limits in force. The total collective dose to the thyroid in Ukraine is
estimated to be 1,300,000 man/Gy, of which about half (607,000 man/Gy) is to 0-18 year
olds. Also the cumulative incidence of thyroid diseases is expected to increase in future.
(7, 12) Various experts estimate that the lifetime risk of thyroid cancer for children who
77
were 0-4 years old at the time of the accident will reach 30%. (12, 13). These estimates
cannot be treated as final (12) until the completion of cohort epidemiology studies (over
the next 20 years when all the radiation-induced thyroid cancers in the exposed
population will have arisen).
For cancers in the exposed adult population, there has been a 2-fold increase in breast
cancer, and a 2 to 7 fold increase in thyroid cancer. (7)
In the post-accident period, increases in cardiovascular, neurological, respiratory,
digestive, and bone-muscular diseases have been registered among the affected
populations. Over 105,000 disabled exposed people are registered in Ukraine, including
over 2,000 children. They are disabled from diseases related to a complex of factors from
the Chernobyl catastrophe and require annual therapy. The children are registered as
invalids due to cancers, congenital malformations, and diseases of endocrine, nervous,
respiratory and digestive systems. (8)
Genomic instability from long-term low-level radiation exposure is a newly discovered
effect which remains under investigation. Uptakes of low levels of caesium, strontium,
plutonium and other radionuclides by mothers and their fetuses may cause additional
cancers, leukaemias and congenital diseases in the first generation. This makes the
problem especially urgent. Unfortunately, there is little coordination between post-
Chernobyl researchers in Ukraine, as there has been no systematic collection,
standardisation and evaluation of findings as yet. This means that valuable findings are not
properly analyzed or compared with other findings. Data from the National Chernobyl
Registry are not properly assessed which makes it impossible to estimate the real levels of
radiation effects on the population from the accident at present. The main health effects
considered to be connected to Chernobyl exposures are cancers and diseases of the
cardiovascular, blood and nervous systems; and among children - cancers and congenital
malformations.(9).
During 2005, mortality indices increased slightly among the population affected by
Chernobyl and total mortality in Ukraine also increased. Mortality indices among liquidators
are constantly increasing. The highest mortality level is among the adult population
resident in radioactively-contaminated territories. At the same time, birth rates in all
observation groups are distinctly decreasing. Taking into account a decreased latency
period of oncological abnormalities, the survival of Chernobyl victims becomes even more
problematic. (9)
It is widely accepted that the Chernobyl accident has resulted in a complex of direct and
indirect factors which adversely affect the health of exposed people. These factors are
considered by the affected people themselves to be significant and dangerous. They
include the following:
• radioactive contamination of the environment by caesium, strontium, and
plutonium
• ingestion of contaminated food
• anxiety over higher illness rates among children.
On the 4th International Conference on «Chernobyl Children - Medical Consequences and
Socio-Psychological Rehabilitation», a persistent complex of post-accident pathogenic
factors was reported (11). This complex included radiation exposure, psychological stress,
78
evacuation and resettlement with subsequent socio-economic effects etc., all of which
adversely affected the somatic and psychological health of children.
Long-term monitoring in the three affected countries has made it possible to select cohorts
of children and teenagers exposed to radiation, with a view to
• continued observation of genetic and oncological diseases;
• epidemiology investigations on the health of survivors of different ages;
• studies on new approaches to the diagnosis, prophylaxis and treatment of low
dose radiation-related diseases (with special attention to molecular-genetic
studies and estimating the impact of genomic instability on morbidity of offspring);
• changing approaches to overcoming of psychosocial problems of affected
children.
The Conference also demonstrated that epidemiology research had been conducted on
thyroid cancer in children and teenagers at the time of the accident, when studies on
radiation-induced non-cancer diseases were lacking. (11)
Abnormal psychological development has been detected in 60-70% of children and
teenagers exposed to radiation. This is two times higher than among general population.
More than 60% of teenagers see their futures away from home because radiation
pollution; (7, 10) affected areas would suffer from depopulation and decline if this
occurred. Therefore, the coordination of efforts between governments, international
organizations and voluntary organizations and all people of goodwill towards the solution
of this complex of economic, ecological, medical and social problems of affected children
and youth is very important. (8, 10).
The report of the UNDP Chernobyl Program in Ukraine in 2003-2005 revealed that the
chronic crisis in the Chernobyl community resulted from its extremely low material status
which restricted its access to medical care.(6) All affected people point to the extremely
low level of medical care at the place of dwelling and the very high costs of better health
care at oblast centres and in Kiev. The international community has been informed about
the humanitarian needs of the affected people, and since 1986 has rendered the affected
people invaluable assistance (6, 7, 10).
The UN report Human Consequences of the Chernobyl Nuclear Accident: A Strategy for
Recovery outlined a ten-year strategy for tackling and reversing the downward spiral on
development. (5) It is clear that the environmental effects of Chernobyl cannot be
considered in isolation from its social, economic and institutional aspects within Ukraine.
The international and national communities are interested not only in the safety of the
reactor Sarcophagus but also in the knowledge to be gained about the long-term effects of
radioactive fallout on health, and disaster management and rehabilitation needed in post-
accident responses. However, scientific interest in the lessons of Chernobyl cannot be
satisfied in isolation from the well-being of those whose lives have been shattered by
Chernobyl (10, 11).
There is little doubt that the Ukraine will have to undergo a long-term period of
rehabilitation. In order to realize the program on the minimization of Chernobyl's social-
economic, health, and radio-ecological effects, it will be necessary to mobilize not only
national efforts but also the efforts of international communities. Chernobyl in Ukraine is
not only a painful memory of the past, but a major current problem and an even greater
future challenge (5).
79
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Acronyms and Abbreviations
(see Annex 4 for radiation dose units and SI nomenclature)
AFMT L'Association Française des Malades de la Thyroïde
ARAC Atmosphere Release Advisory Centre, Lawrence Livermore Research
Laboratory, US
BfS German Federal Office for Radiation Protection
Bq becquerel (unit of radioactivity)
CERRIE UK Committee Examining the Radiation Risks of Internal Emitters
Ci curie (unit of radioactivity)
CRIIRAD Commission de Recherche et d'Information Indépendantes sur la
Radioactivité
DDREF dose and dose rate effectiveness factor
DG TREN Directorate-General for Transport and Energy of the EC
DNA deoxyribose nucleic acid
DoE US Department of Energy
EC European Commission
ECLIS IARC European Childhood Leukaemia-Lymphoma Incidence Study
EPA US Environmental Protection Agency
ERR excess relative risk
EU European Union
Gy gray (unit of absorbed radiation dose)
IAEA International Atomic Energy Agency
IARC International Agency for Research on Cancer
ICP International Chernobyl Project
ICRP International Commission on Radiation Protection
IPHECA International Project on the Health Effects of the Chernobyl Accident
LET linear energy transfer
LNT linear no-threshold (theory of radiation's dose-effect relationship)
NEA Nuclear Energy Agency of the OECD
NCI US National Cancer Institute
NRC US Nuclear Regulatory Commission
NRPB former UK National Radiological Protection Board
OCHA UN Office for the Coordination of Humanitarian Affairs
OECD Organisation for Economic Cooperation and Development
RERF Radiation Effects Research Foundation
SCPRI French Government Central Service for Protection against Radiation
Sv sievert (unit of equivalent or effective radiation dose)
UNDP United Nations Development Programme
UNICEF United Nations Children's Fund
UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation
USSR former Union of Soviet Socialist Republics
WHO World Health Organisation