Zbigniew Jaworowski’s research while affiliated with Central Laboratory for Radiological Protection and other places

Personal reflections on radiation hormesis for the past 50 years are presented. The causes of ignoring and rejections of this phenomenon by international and national bodies and by radiation protection establishment are analyzed. The opposition against nuclear weapons and preparations for nuclear war was probably the main factor in inducing the concern for adverse effects of low doses of ionizing radiation, a byproduct of activism against the nuclear weapon tests. UNSCEAR was deeply involved in preparation of the scientific basis for cessation of nuclear test, and contributed to elaboration of the LNT assumption, which is in contradiction with the hormetic phenomenon. However, this authoritative body recognized also the existence of radiation hormesis, termed as 'adaptive response.' The political and vested interests behind exclusion of hormesis from the current risk assessment methodology are discussed.

The Chernobyl accident was probably the worst possible catastrophe of a nuclear power station. It was the only such catastrophe since the advent of nuclear power 55 years ago. It resulted in a total meltdown of the reactor core, a vast emission of radionuclides, and early deaths of only 31 persons. Its enormous political, economic, social and psychological impact was mainly due to deeply rooted fear of radiation induced by the linear non-threshold hypothesis (LNT) assumption. It was a historic event that provided invaluable lessons for nuclear industry and risk philosophy. One of them is demonstration that counted per electricity units produced, early Chernobyl fatalities amounted to 0.86 death/GWe-year), and they were 47 times lower than from hydroelectric stations ( approximately 40 deaths/GWe-year). The accident demonstrated that using the LNT assumption as a basis for protection measures and radiation dose limitations was counterproductive, and lead to sufferings and pauperization of millions of inhabitants of contaminated areas. The projections of thousands of late cancer deaths based on LNT, are in conflict with observations that in comparison with general population of Russia, a 15% to 30% deficit of solid cancer mortality was found among the Russian emergency workers, and a 5% deficit solid cancer incidence among the population of most contaminated areas.

About 2.3 billion years ago, the advent of an oxidative atmosphere, which was lethal for anaerobic biota, stimulated the surviving organisms to develop efficient defences against the enormous flux of Reactive Oxygen Species (ROS) produced by metabolic processes. Even earlier, similar defences were developed against the thermal instability of molecules and other events that damaged DNA. These powerful ancient defence mechanisms also protect the extant oxygen-loving organisms against the DNA damage caused by low levels of ionising radiation, which is one of the smallest risks in the environment, and contributes just a tiny fraction to the spontaneous rate of the DNA-damaging events. In this perspective, the Linear No Threshold (LNT) model of the radiation effects appears inappropriate for the current needs. Because of statistical reasons, it cannot be falsified. On the other hand, the hormetic model has the capacity to be tested in the observable zone. The precautionary principle, an offspring of LNT, leads to unacceptable societal penalties, as demonstrated in the aftermath of the Chernobyl catastrophe. Biographical notes: Zbigniew Jaworowski, MD, PhD, DSc, is a Professor Emeritus of the Central Laboratory for Radiological Protection in Warsaw, Poland, a member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and its former Chairman. He is the President of the Association of Environmentalists for Nuclear Energy (EFN), Poland. His research fields are radiotoxicology, radiobiology, nuclear emergencies, the historical monitoring of radionuclides and heavy metals in humans in the past 5000 years, the temporal and geographical distribution of pollutants in the global troposphere and stratosphere and the validity of the ice core records for the reconstruction of the past chemical composition of the atmosphere and climate. He has published more than 300 scientific papers, four books and one patent.

Many biological subdisciplines that regularly assess dose-response relationships have identified an evolutionarily conserved process in which a low dose of a stressful stimulus activates an adaptive response that increases the resistance of the cell or organism to a moderate to severe level of stress. Due to a lack of frequent interaction among scientists in these many areas, there has emerged a broad range of terms that describe such dose-response relationships. This situation has become problematic because the different terms describe a family of similar biological responses (e.g., adaptive response, preconditioning, hormesis), adversely affecting interdisciplinary communication, and possibly even obscuring generalizable features and central biological concepts. With support from scientists in a broad range of disciplines, this article offers a set of recommendations we believe can achieve greater conceptual harmony in dose-response terminology, as well as better understanding and communication across the broad spectrum of biological disciplines.

The quality of polar ice cores as a material for reconstruction of the past atmospheric composition is questionable, because the ice cores do not fulfill the absolutely essential closed system criterion. This is due to several physical and chemical processes in snow and ice which may entail changes in composition of air trapped in polar ice. Interpretation of the greenhouse gases data from the ice cores, suggesting that during the past 400 thousands years concentrations of CO2 in the atmosphere were always much lower than currently, are based on rejection of inconvenient analytical results, assumptions disregarding gas fractionation processes, and arbitrary estimations of the age of ice. With the current methodology the glaciological studies are not able to provide a reliable reconstruction of the CO2 levels in the pre-industrial and ancient atmosphere.

The existence of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) is in danger. Dramatic decreases in funding have virtually paralyzed its activities: This year the Committee was unable to convene to continue its scientific work. Established in 1955, UNSCEAR

Ionizing radiation and radioactivity have been subjected to very different evaluations since their discovery in the late 19(th) century. This is due to their potential effects, which are beneficial in medical diagnosis and treatment as well as in technical applications, and cause damage at high doses. In the light of the early finding that high doses are harmful, some first concepts limiting the exposure to manmade radiation were elaborated in the twenties of the last century. They were based on effects detectable at an early stage, and were lowered step by step as far as dose limits were concerned. The question about possible genetic effects, which was still open in the fifties, and the definition of the linear dose - effect hypothesis, resulted in further decreases of limits. It is doubtful to what extent current levels can be justified and are able to protect the health and lives of people. given the limited financial resources available to protect the public. In connection with the debate about the peaceful uses of nuclear Power and the necessary final storage of radioactive waste, possibly in repositories in deep underground geologic formations, attention should be drawn to two natural facts: Natural sources annually release 2 to 3 orders of magnitude more radioactive,substances into the atmosphere than all manmade sources taken top-ether. The cumulated activities released by all nuclear power plants worldwide today roughly correspond to the natural activities of approx. 3 km(3) of terrestrial rock in some 500 years. Accordingly, the human contribution to the natural flow of radioactivity is rather minimal, especially as it can be controlled and limited.