Reality, Illusions and Risks

Zbigniew Jaworowski

Central Laboratory for Radiological Protection

Ul. Konwaliowa 7,

03-194 Poland jaworo@clor.waw.pl

Note:

This is the text of the Prof. Jaworowski's Lecture at the "Discovery of Polonium and Radium; It's Scientific and Philosophical Consequences, Benefits and Treats for Mankind" International Conference (100th Anniversary of the Discovery of Polonium and Radium by Marie Sklodowska- Curie), held 17-20 September 1998

in Warsaw, Poland.

     We are all exposed to natural ionizing radiation, which penetrates all living organisms. Radiation comes from the cosmos and from radionuclides present in rocks, buildings, and air, and in our own body. Each flake of snow, grain of soil, drop of rain, a flower, and even each man in the street is a source of this radiation

The average individual dose of natural radiation received by the world population is now about 2.4 mSv per year. Every day, over a billion particles of natural radiation impact our bodies. However, in some regions, for example, in India and Iran, the natural radiation dose is up to hundred times higher. No adverse genetic, cancerogenic or other effects of these higher doses were observed among the people who have lived in these areas since time immemorial. In the 1990s, man-made radiation has increased the global average radiation dose by about 20 percent, mainly as a result of x-ray diagnostics in medicine. Other important man-made sources, like nuclear power, nuclear weapons tests, or the Chernobyl accident, contributed only a tiny fraction, <0.1 percent, of the total increase.

In those regions of the former Soviet Union that were highly contaminated by Chernobyl fallout, the additional dose to inhabitants is much less than the dose in areas of high natural radiation (Figure 1). The entire man-made contribution to radiation dose amounts to only about 0.2 percent of natural dose in areas of high natural radiation.

Three and half billion years ago, when life began, the natural level of ionizing radiation at the surface of the Earth was about three to five times higher than now (Karam and Leslie, 1996; Jaworowski, 1997). It seems that this radiation might be needed for initiation of life on Earth, and experiments with protozoa and bacteria suggest that it may be essential for the extant life forms (Planel et al., 1987). At the early stages of evolution organisms developed powerful defense mechanisms against such adverse radiation effects as mutation and malignant change. The sites of these effects are situated within the cell nucleus, and DNA is their primary target.

Most of other adverse effects, leading to acute radiation sickness and early lethality, are located in the cell, outside its nucleus. These other effects require large radiation doses, thousands of times higher than natural ones, such as those that might be encountered in a nuclear war, in a beam of cyclotron radiation, or at a defective medical or industrial radiation source. (An example of such a source is the burning Chernobyl reactor, which claimed 28 fatal radiation victims.)

The concern about such large doses is obviously justified. However, the fear of small doses, such as absorbed from Chernobyl fallout by inhabitants of Central or Western Europe, is about as justified as a fear that an atmospheric temperature of 20oC may be hazardous, because at 200oC one can easily get third-degree burns. According to recent studies, the vast majority of DNA damage in human beings is spontaneous, and is caused by thermodynamic decay processes, and by reactive free radicals formed by metabolism of oxygen, such as OH, peroxides, and reactive oxygen species. Each mammalian cell has about 70 million spontaneous DNA damaging events per year (Billen, 1994). No organism would survive such gigantic rate of drastic spontaneous DNA damages if not armed with a powerful defense system. This system consists of the DNA repair and other mechanisms of homeostasis - enzymatic reactions, apoptosis (that is, suicidal elimination of changed cells), cell cycle regulation, intercellular interactions, and so on - which, in the stream of physico-chemical changes, maintain the integrity of organisms during an individual life and over thousands of generations. The same types of damage are caused by ionizing radiation, but with much lower frequency. The present average natural radiation dose of 2.4 mSv per year causes only about 5 DNA damages in one cell. Man's lack of a specific sense organ for ionizing radiation is probably because the body's defense mechanisms already superfluously cover the whole range of natural radiation levels.

The present natural radiation dose in various parts of the world ranges from <1 to >280 mSv per year (Sohrabi, 1990); (UNSCEAR, 1993), (Kesevan, 1996). This range is much greater than the range of normal exposure to thermal energy, for example, which spans about 50oC. Increasing the water temperature in a bath tub by only 80oC, from a pleasant level of 293 kelvins to boiling at 373 kelvins (that is, by a factor of only 1.3), or decreasing it below the freezing point (that is, by a factor of 1.07), may cause death. Such lethal high or low temperatures are often found in the biosphere; therefore, the development of an organ that could sense heat and cold was vital for survival. Organs of smell and taste were even more vital as defense against dangerously toxic or infected food. But a lethal dose of ionizing radiation delivered in one hour - which for man is 3,000 to 5,000 mSv - is a factor of 10 million higher than the average natural radiation dose that one would received in that same time period (0,00027 mSv). This illustrates very weak noxiousness of ionizing radiation, as compared with other agents. Nature provided living organisms with an enormous safety margin for natural levels of ionizing radiation - and for man-made radiation from controlled, peacetime sources. Conditions with lethal levels of ionizing radiation do not occur normally in the biosphere, and, therefore, a sense organ for ionizing radiation was not needed.

Why radiophobia?

  If radiation and radioactivity, although ubiquitous, are so innocuous at normal levels, and one of the smallest risks, why are they an object of universal apprehension? What is the cause of radiophobia - the irrational fear that any level of ionizing radiation is dangerous, which is perhaps the most widely spread and influential superstition of the second half of the 20th century? Why have radiation protection authorities introduced a dose limit for the public of 1 mSv per year, which is less than 1% of the natural dose in many areas of the world? Why do the nations of the world spend hundreds of billion dollars a year (Hezir, 1995) to keep this standard? The answers can be traced to a number of causes and to one false assumption: 1) psychological aftermath of military use of nuclear weapons in Japan; 2) use of nuclear weapons in psychological warfare during the cold war; 3) efforts to stop hoarding the vast arsenals of nuclear weapons of mass destruction; 4) economical interests of fossil fuel lobbies; 5) group interests of radiation researchers fighting for authority and budget; 6) interests of politicians for whom radiophobia was a handy argument in power games (in the 1970s in the USA, in the 1980s and 1990s in Eastern Europe and the Soviet Union); 7) interests of news media, which are profiting from inducing fear; 8) assumption on linear, no-threshold relationship between radiation and biological effects. The nuclear weapons are regarded as a deterrent: Those who possess them wish to make radiation, one of their effects, look as dreadful as possible. Therefore, there is rarely any refutation of even the most obviously false and often voiced statements: "Radiation from nuclear war can annihilate all mankind, or even all life", or "200 grams of plutonium could kill every human being on Earth" (Koning, 1996).

Between 1945 and 1980 there were 541 nuclear atmospheric tests performed, with a total energy yield of 440 Mt. In these explosions, about 3 tones of plutonium (that is, almost 15,000 "deadly" 200 gram doses) were injected into the global atmosphere, and, behold, a miracle: we are still alive! The average individual radiation dose from all these nuclear explosions, accumulated between 1945 and 1998, is about 1 mSv, that is. less than 1% of natural dose (UNSCEAR, 1998). In the record years of 1961 and 1962, there were 176 atmospheric explosions, with a total yield of 84 Mt. The maximum deposition, on the surface of the Earth, of radionuclides from these explosions occurred in 1964. The average individual dose accumulated from this fallout, between 1961 and 1964, was about 0.35 mSv. The global nuclear arsenal being about 50,000 weapons, with a combined explosive power of about 13,000 Mt (Rotblat, 1981; Waldheim, 1991), is only 30 times higher than the megatonnage already released by all previous nuclear tests in the atmosphere.

If all the global nuclear arsenal were exploded, with a combat geographic distribution similar as in the past nuclear tests, the average individual would receive a long-term radiation dose of about 30 mSv, from the ensuing world-wide fallout. Using as a yardstick the years of 1961 and 1962, this dose would be about 55 mSv. Exploding all the nuclear weapons in few days instead of two years, would not much change this estimate, which is a far cry from the short-term lethal dose of 3000 mSv for man.

The bomb and the LNT Theory

    At Hiroshima and Nagasaki, short-term radiation doses of less than 200 mSv did not cause induction of cancers among the atomic bomb survivors (UNSCEAR, 1993). Among survivors exposed to much higher doses, no adverse genetic effects in their progeny have been detected during 50 years of study (Sankaranarayanan, 1997). Until recently, such information from the study of survivors has been ignored. Instead, the driving force of radiophobia has been the linear no-threshold theory, assumed for relationship between radiation and its effects on the living organism (essentially, the assumption that the detrimental effects of radiation are proportional to dose, and that there is no dose at which such effects are not detrimental). It is on this assumption, that the International Commission of Radiological Protection (ICRP) arbitrarily based its rules of radiation protection in 1959. This was an administrative decision, not an effect of scientific proof. It was based not on science, but on political considerations, which influenced the philosophy and practice of radiation protection (Taylor, 1980).

Over the years, the working assumption of ICRP, stating that even the smallest amounts of radiation - close to a zero dose - may cause harm, came to be regarded as a scientifically documented fact by mass media, public opinion, regulatory bodies, and even by many scientists. The linear no-threshold theory, however, is not a scientific principle; it belongs solely to the realm of administration. The absurdity of the no-threshold theory was brought to light after the Chernobyl accident in 1986, when minute doses - for example, reaching in the United States 0.004% of the average natural dose, or 0.3% at the rest of the Northern Hemisphere - were used to calculate 53,400 cancer deaths over the next 50 years (Goldman et al., 1987). Such frightening numbers were derived by simply multiplying trifling Chernobyl doses, and the vast numbers of people living in the Northern Hemisphere, by a cancer risk factor based on epidemiological studies of 75,000 atomic bomb survivors in Japan.

The bomb survivor data, however, are not relevant for such estimations, because of the difference in the dose rate. Bomb survivors were irradiated in a hundred-millionth fraction of a second with doses more than 50,000 times higher than those U.S. inhabitants will receive from Chernobyl fallout over 50 years. For a dose rate of, say, 1000 mSv per one-billionth of a second in Japanese bomb survivors, we have reliable epidemiological data. But there are no epidemiological data for a dose rate of 0.0046 mSv per 50 years in U.S. inhabitants. The dose rate in Japan was larger by 3.5 x 1022 than the Chernobyl dose rate in the United States. Extrapolating over such a difference is epistemologically not acceptable. Estimates of cancer death based on such extrapolations was defined by Dr. Lauriston S. Taylor, the former president of the U.S. National Council on Radiological Protection and Measurements, as "deeply immoral uses of our scientific heritage." Nevertheless, exactly such no-threshold extrapolations are the foundation of both the philosophy and practice of radiological protection during the second half of the 20th century, leading to the current excessive dose limit of 1 mSv per year, more than 200 times higher than natural doses in some regions. This limit is completely unrealistic in view of credible studies showing that there are no significant data confirming any adverse health effects below 200 to 300 mSv short-term doses, and below 1000 mSv of long-term fractionated radiation. To the contrary, there is a host of studies demonstrating beneficial effects of doses below 300 mSv (Muckerheide, 1998).

Enter hormesis

   Linear no-threshold theory is contradicted by the phenomenon of hormesis, that is, the stimulating and protective effects of small radiation doses. The first report on hormetic effects in algae appeared 100 years ago (Atkinson, 1898). One of the most recent hormetic effects can be seen in the lower-than-normal incidence of leukemia (Figure 2) and the greater longevity among atomic bomb survivors (Kondo, 1993).

Although more than 2,000 scientific papers were later published on radiation hormesis, after World War II, the phenomenon was forgotten and ignored by the radiation protection establishment. It was as late as in 1994, that the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the most distinguished scientific body on matters of radiation, recognized and rubber-stamped the very existence of radiation hormesis (UNSCEAR, 1994). This caused a "revolutionary ferment" among profession of radiologists, both ethical and technical.

Ethics

    Many radiologists realized that over the past decades they might have been unethically overgrasping, diverting resources to be consumed in the "avoidance" of theoretical (actually imaginary) health effects, thereby depriving society of funds that were desperately needed to deal with real health problems (Thomas, 1998). Applying the no-threshold principle for the alleged protection of public, imposed restrictive regulations on nuclear utilities, which virtually strangled development of environment and human friendly nuclear energy in the United States and in several other countries.

In my own country, after spending billions of dollars, the construction of the first nuclear power reactor was abandoned, as a result of politically motivated distortion of public opinion by the no-threshold principle. Each human life hypothetically saved by implementing these regulations costs about $2.5 billion. Such costs are absurd and immoral, especially when compared to the costs of saving lives by immunization against measles, diphtheria and pertussis, which in developing countries range between $50 and $99 per one human life saved (Cohen, 1992). Billions of dollars for such imaginary protection of human life are really spent year after year, while much smaller resources for real life-saving in developing nations are notoriously lacking. This is not what Maria Sklodowska-Curie was dreaming of when at the beginning of 20th century she harnessed radiation to benefit mankind.

An alternative based on reasons

   There is an emerging awareness that radiation protection should be based on the principle of a practical threshold, one below which induction of detectable radiogenic cancers or genetic effects is not expected. Below this threshold, radiation doses might be regarded as having no regulatory concern. Regulations are not needed for the situations such as experienced in Hiroshima and Nagasaki, with extremely high dose rates. Therefore, a practical threshold will be probably based on epidemiological data from exposures in medicine, nuclear industry and regions with high natural radiation. The current population dose limit of 1 mSv per year may then be changed into 10 mSv per year or more. This would be an important step on the way to rationality and to gaining again the public acceptance of radioactivity and radiation as a blessing for humankind.

References

Atkinson, G.F., 1898. Report upon some preliminary experiments with Roentgen rays in plants. Science, 7: 7.

Billen, D., 1994. Spontaneous DNA damage and its significance for the "negligible dose" controversy in radiation protection. BELLE Newsletter, 3(1): 8-11.

Cohen, B.L., 1992. Perspectives on the cost effectiveness of life saving. In: J.H. Lehr (Editor), Rational Readings on Environmental Concerns. Van Nostrand Reinhold, New York, pp. 461-473.

Goldman, M., Catlin, R.J. and Anspaugh, L., 1987. Health and environmental consequences of the Chernobyl Nuclear Power Plant accident. DOE/RR-0232, U.S. Department of Energy, Washington, D.C.

Hezir, J.S., 1995. Statement at EPA's Public Hearing on the Proposed Recommendations for Federal Radiation Protection Guidance for Exposure of the General Public. February 22-23, 1995, Washington, D.C.

Jaworowski, Z., 1997. Ionizing radiation when life began. 21st Century Science and Technology, 10(1): 4.

Karam, P.A. and Leslie, S.A.,1996. The evolution of Earth's background radiation field over geologic time, IRPA 9th Congress. IAEA, Vienna, Austria, p. P12-22.

Kesevan, P.C., 1996. Indian research on high levels of natural radiation: pertinent observations for further studies. In: L. Wei, T. Sugahara and Z. Tao (Editors), High Levels of Natural Radiation 1996. Elsevier, Amsterdam, Beijing, China, pp. 111-117.

Kondo, S., 1993. Health Effects of Low-level Radiation. Kinki University Press, Osaka, Japan, 213 pp.

Koning, H., 1996. Potentially lethal. International Herald Tribune(27 November, 1996).

Muckerheide, J. (Editor), 1998. Low Level Radiation Health Effects: Compiling the Data. Radiation, Science & Health, Inc., Needham, Massachusetts 02494.

Planel, H. et al., 1987. Influence on cell proliferation of background radiation or exposure to very low, chronic gamma radiation. Health Physics, 52(5): 571-578.

Rotblat, J., 1981. Nuclear Radiation Warfare. SIPRI - Stockholm International Peace Research Institute and Taylor & Francis Ltd, London, 1-149 pp.

Sankaranarayanan, K., 1997. Recent advances in genetic risk estimation. Lecture presented at 46th session of UNSCEAR, UNSCEAR document 46/10, 18 June, 1997.

Sohrabi, M., 1990. Recent radiological studies of high level natural radiation areas of Ramsar. In: J.U.A. M. Sohrabi, and S.A. Durrani (Editor), High Levels of Natural Radiation. IAEA, Ramsar, Iran, pp. 39-47.

Taylor, L.S., 1980. Some non-scientific influences on radiation protection standards and practice, 5th International Congress of the International Radiation Protection Association. The Israel Health Physics Society, Jerusalem, pp. 307-319.

Thomas, R.H., 1998. Ethic and Science: letter to the Editor. SSI News, 6(1): 7.

UNSCEAR, 1993. Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on the Effects of Atomic Radiation, New York.

UNSCEAR, 1994. Sources and Effects of Ionizing Radiation. United Nations Scientific Committee on the Effects of Atomic Radiation, New York, 1-922 pp.

UNSCEAR, 1998. Exposures from man-made radiation. General Assembly A/AC.82/R.579, United Nations Scientific Committee on the Effects of Atomic Radiation, Vienna.

Waldheim, K., 1991. Comprehensive Study on Nuclear Weapons, Report of the Secretary-General, United Nations, Department of the Political and Security Council Affairs, United Nations Centre for Disarmament, New York 19

Professor Jaworowski is a professor at the central laboratory for radiological protection in Warsaw.

As a multidisciplinary scientist, he has studied pollution with radionuclides and heavy metals. He has also served as the chairman of the United Nations Scientific Committee on the Effects of Atomic radiation (UNSCEAR).