Radiat Environ Biophys (2002) 41:1–4 DOI 10.1007/s00411-002-0150-y

EDITORIAL

A. M. Kellerer

Beyond Chernobyl: the new Russian studies in perspective

Published online: 9 March 2002 © Springer-Verlag 2002

Ionizing radiation is not one of the major cancer risk factors nor a major cause of hereditary damage. Yet, it is the risk factor that has been most thoroughly studied, and arguably it is the one that has caused and continues to cause the deepest public concern. This situation may appear paradoxical, but it reflects the inseparable association of today’s perception with historical experience, including its tragedies and failures. When in 1895 a new kind of invisible radiation was discovered in a provincial German university, the news traversed the world within few days, an extraordinary process at the time. In the spirit of a century of technical and scientific progress, Röntgen’s discovery was taken as the promise of unlimited advancement and the culmination of classical physics. Both expectations were bound to fail. The political, economic and ecological catastrophes of the 20th century were to change technical optimism into skeptical dissent. The culmination of classical physics turned out to be its demise; an entirely new world of physics was about to be created. The uses of radiation, the science of radiation, and the perception of radiation evolved in a manner that mirrored the larger changes. In the decades after the discovery of x-rays and radioactivity the technical promises were taken to include all kinds of medical benefits. The new radiation was used without a suspicion of danger. Skin burns, the results of unprotected use of x-ray machines, were judged to be trivial results of gross negligence. In 1909 – a few years even before Friedrich and von Laue identified by their diffraction experiments the physical nature of x-rays – the first cluster of leukemia was reported. It had occurred among Berlin radiologists, and it was not taken as a warning.

Unheeded warnings Radiation that had unheard of diagnostic power was subsequently taken to be a vital stimulating agent in itself. It was believed to possess general healing forces, to be a magic cure for all. Against such wishful thinking it was difficult to beware of dangers. Tragedies caused by the unprotected use of radioactivity had to happen. In the United States and in other countries hundreds of young women painted watch and instrument dials with radium paint. Being paid by the piece they did their work in the most effective, and also the most detrimental way, they pointed the brushes with their lips. Many of them were to perish from bone cancer. Again the tragedy was noted, but it was not seen as an alert to the risk of low doses; as a matter of fact, the doses were large. Much later the fate of the dial painters became one of the somber sources of knowledge on radiation risk. Regrettably the US study of health effects among the dial painters has been discontinued, but the consequences of other, similar tragedies continue to be followed. Foremost among these are the study on patients, mostly soldiers, who received a radioactive contrast medium, thorotrast, and on other patients – many of them children and juveniles – who were injected with disastrously high doses of the short lived alpha-emitter 224Ra. None of the unprotected uses of radiation and radioactivity led to a change in the philosophy of radiation protection which was, at the time, based on the assumption that small doses were, if not beneficial, at least entirely safe, and that, consequently, protective measures would be adequate as long as they served to avoid unduly high exposures.

A.M. Kellerer (✉) Radiobiological Institute, University of Munich, Schillerstrasse 42, 80336 Munich, Germany e-mail: [email protected]

The great reversal and the new philosophy of radiation protection

A.M. Kellerer Institute of Radiobiology, GSF – National Research Center for Environment and Health, 85764 Neuherberg, Germany

Half a century after the discovery of x-rays, the perception of radiation was radically changed. Nuclear fear began to reign for the next 50 years. When Hiroshima and, a few

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days later, Nagasaki perished under the atomic bombs, radiation – the hallmark of progress and of healing power – was in the flash of the nuclear fire changed to the symbol of hell. Yet, in the aftermath of the nuclear explosions, the first steps were taken, first by Japanese physicists and physicians, then by US scientists together with Japanese investigators to secure the knowledge that would hope-fully never be offered by another tragedy of similar nature. Since that time, the observations on the atomic bomb survivors have developed into the largest epidemiological investigation ever undertaken. Thousands of dedicated scientist, primarily from Japan and the US, but also from many other countries have, over half a century, laid the groundwork for the current knowledge of the health effects of ionizing radiation and the risks of small doses. An increase of leukemia, especially among children, was noted first. It had been known earlier that ionizing radiation can produce mutations of germ cells and, thereby, cause hereditary damage. Now it was realized that it can equally produce mutations of somatic cells, and that such mutations could be the origin of a leukemia. Since individual charged particles can cause the mutations, it was concluded that radiation protection had to go beyond the avoidance of large doses. Even small doses were now assumed to induce, with correspondingly small probability, leukemia and possibly – as was then argued – other types of cancer. About 10 years after the nuclear explosions, the excess rates of leukemia were seen to decline, and to many of the scientists who were involved this seemed to imply that cancers other than leukemia are, in fact, not caused by ionizing radiation. It seemed that the essential observations had been made about the increase of leukemia, and little, if anything, was left to be learned from the follow-up of the A-bomb survivors. A momentous decision was then made by a small committee of scientists. With admirable scientific modesty and fully aware of their singular responsibility they recommended continuation of the large scale investigation. The subsequent history of the follow-up of the A-bomb survivors is written in a multitude of scientific reports of the Radiation Effects Research Foundation (RERF), Hiroshima, and its predecessor organization, the Atomic Bomb Casualty Commission (ABCC). The essential results are laid down also in a remarkable documentation of peaceful international cooperation of scientists, the regular public assessments of the United Nations Scientific Committee on the Effects of Atomic Radiations (UNSCEAR). Out of one of the awful tragedies in mankind’s history an effort has arisen that has contributed and will continue to contribute knowledge that is equally important for the protection from ionizing radiation and for its vital uses in medicine.

The stigma of ionizing radiation amplified by nuclear accidents The great study on the atomic bomb survivors has provided reliable information on radiation risks and this in-

formation has been corroborated by a variety of studies on persons exposed for medical reasons. At the same time, the public perception of radiation risk has drifted apart from the scientific consensus. It is not surprising that the stigma of ionizing radiation, its association with the atomic bombs, has become more engrained during the dark years of the Cold War and its nuclear threat. The world-wide contamination from atmospheric nuclear tests has been contained only after the people of the northern hemisphere had become increasingly concerned and when large scale protest had started. When the tests were ended, the concern continued and it did not remain focused on nuclear weapons alone. The peaceful uses of nuclear power and even the medical applications of radiation began to be increasingly at issue. When subsequently, in spite of the accustomed pronouncements of the minimal likelihood of major accidents, such accidents actually occurred, the worst apprehensions appeared to be confirmed. The accident at Three Mile Island was an unexpected and costly technical disaster. It was resolved without very large releases of radioactivity, but its impact on the official and public perception of nuclear safety was enormous. When 10 years later a nuclear excursion occurred in Block 4 of the Chernobyl power plant, and when in the reactor core 200 tons of graphite began to burn, enormous amounts of radioactivity were transported into high altitude and were from there carried not only to regions of Belarus, the Ukraine, and Russia, but also into Western Europe. The resulting dissent and confusion testified to the divergent perception of ionizing radiation and its potential health effects. It also elevated the apprehensions and anxieties to a new level. The psychological and political fallout was not less serious than the radioactivity itself, and its half-life may well exceed that of 137Cs. In the immediate aftermath of the Chernobyl catastrophe the expectation of health effects was frightening and uncertain. Experts did their best to quantify the risks in terms of the results that had been obtained in the followup of the A-bomb survivors and in the medical studies. They failed, not primarily because of uncertainty in the data, but because the gap between scientific insights and the public perception had never been closed. During the final years of the Soviet Union the problems were compounded by an official policy that blocked all information on potential health effects of the accident. When, 2 years after the accident, the veil of secrecy was lifted, information, misinformation, and doubt had become inseparable.

Expectations of new knowledge from the consequences of the Chernobyl accident Beyond the other Chernobyl catastrophe, i.e., the failure of risk communication and the loss of credibility, there did remain uncertainty in the scientific data themselves. One of the major issues was the potential difference between the effects of short term, high dose-rate exposures,

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as in Hiroshima and Nagasaki, and continued low dose rate exposures, as caused by the Chernobyl accident. It was felt that a thorough examination of health effects after Chernobyl might provide risk estimates that are more relevant to the long term exposures that are of major concern in radiation protection. The expectation of new and more quantitative risk estimates were not fulfilled, which – fortunately – meant that the worst expectations with regard to health effects have not become reality. The low dose rate exposures of the population due to the long lived radionuclides, predominantly 137Cs, have not led, up to now, to discernible increases of cancer rates, not even of leukaemia in children. Doubtlessly, it will be important to continue the assessment of cancer rates in the regions most highly affected by the Chernobyl accident. But there is little reason to expect that excess incidences will be seen that can provide improved risk estimates and can, thus, add to our knowledge of low dose radiation risk. In one important way Chernobyl has led to tragic and dramatic health effects among the population. The enormous releases of radio-iodine in the first days of the accident and the exposure in the subsequent days and weeks led to large thyroid doses. A very high excess of thyroid tumors, especially among children, began to be seen in Belarus and the Ukraine about 4 years after the accident. The relatively short latency times and the estimated dose dependencies are not inconsistent with the observations in Hiroshima and Nagasaki, but they add substantially to existing knowledge. The increased thyroid cancer rates are a grave public health problem, and due to this deplorable fact they are informative with regard to risk estimation. The reverse is true for the effects of the long lived radioisotopes, specifically 137Cs. Since the accident at Chernobyl has not caused observable increases of leukaemia or other cancers, apart from the thyroid tumors and, therefore, it fails to provide improved risk estimates for these endpoints. The issue is, thus, whether there are other sources of direct information on late effects produced in man by long term low dose rate exposures.

Other sources of information Direct information exists with regard to radon and lung cancer. It derives from the dismal fate of countless workers who have labored in underground mines, especially in uranium mines. A great number of lung cancer deaths has been caused among these workers who have become victims of the atomic bombs not because they were exposed to their effects, but because they had to mine uranium with little or no protection under the merciless pressure of the Cold War to produce ever more nuclear weapons. With regard to sparsely ionising radiation there have been no situations – so it seemed – that would relate to equally harmful working conditions. For the same reason there have been no studies that can provide improved

risk estimates. The studies of Western nuclear workers are necessary and valuable. They document general consistency with the estimates based on the observations on the A-bomb survivors, but by themselves they cannot provide or improve risk coefficients. Direct estimates do not exist for long term low dose rate exposures.

Beyond Chernobyl When the accident happened at the Chernobyl nuclear power station, little was known in the Western World about earlier accidents or about radiation-exposed cohorts in the Soviet Union. For years there had been rumors about a large scale nuclear accident in 1957 in the Southern Urals, but details were unknown or were kept classified. One knew that there had been extensive radioactive releases from military nuclear installations in the West, and that Western nuclear tests had led to accidental exposures. It was only too likely that analogous problems must have happened in the Soviet Union, but the issue remained shrouded in secrecy. Subsequently, when the Cold War came to an end, Russian scientists were able to share their knowledge, and a new horizon was opened far beyond Chernobyl, both in time and in geography. In the early years of the Cold War great efforts had been made by the Soviet Union in the nuclear arms race. Thousands of workers in the plutonium plants of Mayak in the Southern Urals performed their work under extraordinary pressures. They were subjected for years to external radiation and to the exposure from inhaled plutonium, both resulting in doses far above acceptable limits. Many of the workers – women as well as men – suffered from chronic radiation sickness, a syndrome never observed elsewhere and not known in the world, before secrecy was lifted from the closed cities of military research and weapons production. Russian scientists and physicians had made extraordinary efforts to manage a situation that was essentially out of control. They aided the nuclear workers to the best of their abilities, and they attempted likewise to document and explore the problems of the populations that were exposed along the river Techa from radioactivity released by the nuclear plants. In total secrecy they had battled for decades with health problems among the exposed workers of Mayak and among the Techa river populations. They were concerned with people subjected to doses far beyond those that resulted from Chernobyl. They had accumulated experience that Western scientists were fortunate enough never to have encountered. When these things became known, they sounded unlikely at first to many of the Western scientists. When they were confirmed and when foreign scientists were invited to share existing insights and ongoing investigations, it became clear that a vast new chapter of radiation epidemiology was about to be written, and a new base of knowledge was about to be created. In the sober tradition of radiation epidemiology, knowledge is gained from a

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dark source, but this time it is experience directly related to the long term protracted exposures that are most relevant to radiation protection. A first synopsis, preliminary in various ways, yet a careful account by the leading Russian scientists who had done the work, was published in 1994 (Radiation exposures in the Southern Urals. Special Issue of ‘The Science of the Total Environment’ 142: 1,2). Important international cooperations were then started, and essential links to the Russian institutions were built by the USDepartment of Energy, by the European Commission, and, last but not least, by the Radiation Effects Research Foundation, Hiroshima. While the cooperations originated at the Southern Urals Biophysics Institute (SUBI), Ozyorsk, and the Urals Research Center for Radiation Medicine (URCRM), Chelyabinsk, they have since been extended to include the institutions in the Altai region and in Kasakhstan that explore health consequences from nuclear weapons tests, namely the Institute of Regional Medico-Ecological problems (IRMEP), Barnaul, and the Kazakh Research Institute for Radiation Medi-

cine and Ecology (KRIRME), Semipalatinsk. A number of the joint research projects have led to publications in Western scientific journals. But, considerable difficulties remain, many of them aggravated by economic difficulties, by technical problems of funding, and always by the hardship that Russian scientists need to accept when they take it upon themselves to continue their work. One cannot fail to note that this is a critical junction for the new radiation studies in Russia and other countries of the former Soviet Union. It is not dissimilar to the situation when against serious odds the decision was made to continue and extend the follow-up of the A-bomb survivors. Much less would be known today about the risk of ionizing radiation, if the wrong decision had been made then. A similar statement will perhaps be made when future scientists look back at the Russian studies in the years to come. It is hoped that the present synopsis – an outcome of international coordination meetings at Schloss Elmau in 1998 and in 2000 – may facilitate the careful planning and the international cooperation that will be required to continue and extend the current efforts.