Chernobyl: Assessment of Radiological and Health Impact
2002 Update of Chernobyl: Ten Years On
Several years after the Three Mile Island accident in the United States, the Chernobyl accident in 1986 completely changed the public's perception of nuclear risk. While the first accident provided the impetus to develop new research programmes on nuclear safety, the second, with its human death toll and the dispersion of a large part of the reactor core into the environment, raised a large number of "management" problems, not only for the treatment of severely exposed persons, but also for the decisions that had to be taken in respect of the population. Clearly, not only the national authorities of the Soviet Union, but more broadly, authorities from many other affected countries were not ready to manage an accident whose consequences were not confined to their territory.
The way the accident was managed and the lack of information provoked a feeling of distrust in the minds of the public that was reinforced by the fact that radiation cannot be perceived by humans, although it can be easily identified with electronic detectors, even at a very low level. The prospect of contaminated food, aggravated by ambiguous, even contradictory recom-mendations by national authorities, gave rise to a variety of reactions, and sometimes overreactions, in the management of the accident consequences in several European countries. In the accident country itself, where political, social and economic conditions were worsening, the association of the Soviet regime with nuclear activities contributed to raise feelings of mistrust towards the public authorities.
More than sixteen years after the Chernobyl accident, public concern remains high in spite of the considerable amount of information disseminated by national authorities and large international organisations, the multitude of scientific papers in the specialised press, and the numerous symposia devoted to this accident. The same questions are still being asked and the general public, the media and sometimes the politicians concerned, still find it difficult to understand the information provided by the scientific community.
Public opinion in the former Soviet Union and in many other countries affected by the accident remains convinced that certain cancers, such as those of the thyroid, can only have resulted from the Chernobyl accident. This view is partly driven by statistics showing that in European countries the incidence of such cancers has increased. Although this cannot be attributed to the accident, because this increase has been ongoing and was recorded long before the accident occurred, it remains difficult for doctors to reassure patients in this regard. As the increase in childhood thyroid cancer, which occurred primarily in Belarus, emerged in the early 1990s, many experts were surprised by this "early" appearance of thyroid cancer and by its geographic distribution within the affected territories. This further aggravated public scepticism of the scientific community.
The media have at times published pictures of human and animal deformities without investigating their veritable connection with the accident, and the public, struck by such images, has been allowed, unchallenged, to lay the blame on Chernobyl. Here again, the accident has given rise to numerous studies showing that such deformities and diseases are not linked to radiation exposure. These conclusions, however, have not been effectively transmitted to decision makers or the public. On the other hand, many feared a catastrophic contamination of the River Dnieper, extending to the Mediterranean, which never materialised. Radionuclide retention in the soil has been high, and any remaining contamination is well below initial projections. So much the better.
In this context of public concern, the NEA has found that by far the most consulted document on its website is the one drafted in 1996 on the impact of the Chernobyl accident. That is why, with more recent information now available, in particular the new United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report published in 2000, it was timely to update the Chernobyl: Ten Years On report. Several figures have changed as a result of the numerous and increasingly detailed studies carried out over the last years. The list of bibliographical references has also been updated, with one quarter more bibliographical references than in the previous edition. Furthermore, the NEA wished to address the questions raised by numerous other reports that have been issued, either on the tenth anniversary of the accident or immediately afterwards. Among these reports were those prepared by UNSCEAR, and by the International Atomic Energy Agency (IAEA) on the state of the environment, which had, to a large extent, served as a model for the present report.
This report presents the knowledge gained since the accident, which has evolved gradually. Environmental contamination, which seemed to be decreasing fairly quickly, has reached an ecological equilibrium and, in certain limited sectors, has even increased due to a reconcentration of 137Cs, the only radionuclide remaining in the different soil compartments involved in food chain transfers. This process has gone as far as it can, and now, in places where contamination persists, only the radioactive decay of caesium will reduce the impact of the accident.
The huge effort by the international community to gain a better under-standing of the real impact of Chernobyl continues, and should, in the next ten years, clarify the main consequences of the accident. The main trends described in 1996 continue to be valid in 2002: thyroid cancer in children remains the only striking manifestation of the accident as far as the public is concerned. The significant increase in cases of leukaemia, which had been so greatly feared, has not, on the other hand, materialised.
Many improvements in radiation protection and emergency preparedness have been made possible by the Chernobyl experience and we are also able to develop a more accurate assessment of the impact of this accident. Under the auspices of the NEA Committee on Radiation Protection and Public Health (CRPPH), supported by other international bodies, the most outstanding progress since the Chernobyl accident has been in learning about inter-governmental communications and co-operation in the case of nuclear emergencies. The International Nuclear Emergency Exercises (INEX) bear witness to this. Governments, initially reluctant to publicly discuss nuclear accident preparedness and management issues, now ask for such exercises to be carried out, operators are no longer reluctant to offer their sites for this purpose, and local authorities are pleased to invite the participants involved to appear before the media. This shows the progress achieved in terms of communication and involvement of all social partners. More impressive still is the progress made concerning the distribution of stable iodine near nuclear power plants, a subject that was more or less taboo before the accident. The NEA organised an international colloquium on this topic, and this issue is today openly debated.
Here again, the CRPPH played an experimental and innovative role, stressing how very important it is to involve all social partners. This idea, which originated in the context of accident management, has been taken up by many other disciplines, including the management of nuclear waste. This fundamental point is also one of the positive lessons learnt from the accident.
The accident was followed by numerous assistance and research programmes supported by international organisations and bilateral agreements. All these organisations are or will be publishing their results. This report differs from the others in that it is a synthetic consensus view aimed at those persons who wish to know the salient points, without having to go into the technical details that can be found elsewhere.
We thank all those organisations (IAEA, UNSCEAR, FAO, WHO, EC and others) that have provided information so that this report could be as up to date as possible. The original report Chernobyl: Ten Years On was drafted by Dr. Peter Waight (Canada) under the direction of an editing committee chaired by Dr. Henri Métivier (France).
This edition was prepared by Dr. Henri Métivier on request of the CRPPH.