"Best Paper competition"
Igor.I. Suskov, M.D., Ph.D.*
N.I. Vavilov Institute of General Genetics, Russian Academy of Sciences, 119991, Moscow, Russia
Alexandr I. Glouchtchenko, Ph.D.
Department of Nuclear Engineering, Ben-Gurion University, POB 653, Beer-Sheva, 84105, Israel
Abstract
In the XXI th century the assessment of hazard to human heredity and health from the radionuclide and chemical environmental pollution becomes of prime social importance since it is related to the problems of utilization of great amounts of radioactive and chemical wastes, spent nuclear fuel, weapon plutonium, nuclear reactors and emergency discharges of izotops which in total is higher than 1 billion Ci. Long-term cytogenetic monitoring of nuclear and chemical plant workers, local human populations of radioactive waste areas and radionuclide polluted territories has revealed that the level and spectrum of induced chromosome aberrations in blood lymphocytes correlate with the type, dose and duration of exposure. There is very strong evidence that the yield of chromosome aberrations (Y) is related to the dose (D) by the equation: Y=A0+aD+bD2. Therefore the radiation/radionuclide risk (R(D)) will correspond to a absorbed dose and its aberrational/mutational consequences ("doubling dose" coefficient). Increased levels of chromosome aberrations in the human body very often precede the development of several syndromes: chronic fatigue, secondary immune deficiency, early aging, reprodactive disfunction, oncological diseases and etc. The increased levels of chromosome aberrations in blood lymphocytes can serve as objective bioindicators of radiation and chemical risk to human heredity and health. Thus, monitoring of chromosome and genome aberrations must be of strategical importance in the system of governmental service for minimization of radionuclide and chemical hazard for human heredity and health. The necessity of organization of such monitoring has already matured. The abovementioned confirms the necessity of founding a European network for ecological-genetic monitoring with "Internet" translation of information on the radionuclide composition and the chromosome aberration levels in people, inhabiting at the contaminated areas.
Key words: Risk analysis; Chromosome and genome aberrations; Radionuclides; Chemicals; Internet.
* Corresponding author: Tel.:+ 095 - 1357172, Fax: +095- 132-89-62; e-mail: suskov@vigg.ru
The manking enters into 3 rd millennium with a number of unsolved ecological problems. One of them is the lack of transparency in objective assessment of radiation /radionuclide risk for human health and ecosystems due to the accumulation in the 2nd half of the XX century of technogenic radioactive materials.
According to the UNSCEAR (1997) [1], the main sources of radioactive contamination of the environment are:
1) the nuclear tests in air, underground and in water carried out in USA, USSR, GB, France, China, India (541 explosions in total);
2) the production/reprocessing of nuclear fuel and weapon uranium and plutonium and a resulting accumulation of radioactive waste products (Fernald, Oak Ridge, Hanford etc. in the USA; Mayak-Chelyabinsk-40, SCK-Tomsk in the USSR and in GB, France, China);
3) the nuclear power plants (NPP, about 500 reactors in total),
4) the accidents on NPP and the ships with nuclear power plants
The pollutions in the environment , especially in the water basins, occurred in the recent past due by the use of imperfect technologies [2]. The regional problems of contamination by artificial radionuclides have grown into global ones that aggravated in 1986 as a result of the catastrophe at the Chernobyl nuclear power plant: enormous masses of radioactive substances (over 1 milliard Ci) were released in the environment and dissipated [3]. The radioactive cloud after Chernobyl disaster passed over Europe, the Northern hemisphere of the Earth and it was noted twice on the territory of the United States [4]. In the history of the mankind a unique situation occurred when very large contingents of the population found themselves facing the real danger of being affected by long-living radionuclides for an unlimited period of time. The neglect of ecological problems leads inevitably to the catastrophically consequences in society. Another striking demonstration of this thesis - the approaching regional/ global ecological disaster in Baltic Sea and the countries, contiguous to Baltic Sea. 300 thousands tons of the German chemical weapons were sunk by the allies (USA, GB and USSR) after World War II in 1947 in the Southern part of Baltic sea and its straits. Because of metal corrosion in sea-water, an intensive process of going-out of poison gases (yperite, leusite etc.) in the environment will begin in the next 7-9 years. This will entail a contamination of sea flora and fauna, a poisoning of European human population, first of all, in the countries of Northern and Central Europe [5,6].
In the recent 10 years, the natural gaseous radionuclide Rn-222 has increased because of the intensifications of are mining and the expansion of construction works in the countries Scandinavia, Western Europe, etc.
The main risk comes from radioactive nuclides released into groundwater and transferred to potable water sources, or end up in food [7].
The influence of low-intensive radiation from dissipated radionuclides on people and ecological health is becoming a world problem.
Considering the number and power of the nuclear explosions, the number and types of nuclear reactors, the amount of radioactive waste products and emergency discharges of radionuclides, methods and models have been developed to determine local, regional and global annual doses that are usually estimated by the density of scattering of long-lived radionuclides Sr-90 and Cs-137 and are calculated for the population as collective effective doses (man/SV). The contribution of short-lived (I-131 etc.) and other radionuclides (H-3, C-14, Pu-239, Am-241, "hot-particles" etc.) is usually not taken into account. Since in local, regional and global scales the impact of technogenic and natural radionuclides and medical isotopes is experienced by hundreds, thousands and millions of people, the assessment of radiation/radionuclide risk requires the constant monitoring of the most informative and significant radiobiological effects in both individuals and local populations.
The chromosome aberrations in blood lymphocytes are most accurately quantifiable from all radiobiological reaction of the human organizm [8]. Performing the immuno-protective functions, blood lymphocytes circulate over the whole body and are practically always exposed to ionizing radiation from radionuclides and chemical compounds penetrating inside the organism. Since 99,8% of T-lymphocytes are in the pre-DNA synthetic phase Go, the primary chromosome lesions are preserved in the lymphocytes for a long time (months, years) and can be detected as aberrations under stimulation by PHA-antigen in vitro.
The long-term cytogenetic monitoring of nuclear and chemical plant workers, local human populations of radioactive waste areas and radionuclide polluted territories has revealed that the level and spectrum of induced chromosome aberrations in blood lymphocytes correlate with the type, dose and duration of exposure [9].
The high level of aberrations in the chromosomal spectrum was observed in many people after single (accidental) and multiple ("cleanupers" following Chernobyl explosion) external exposure to g- or g- n -radiations [10].
The increased levels of aberrations in chromosomal spectrum and rare multiaberrant cells were observed after long-term/chronic mixed external/internal exposure to low doses of g/b/a-radiation by radionuclides at the inhabitans of Chernobyl polluted regions, Altai territories with the radioactive fallouts in result of the nuclear explosions on Semipalatinsk test-ground and radiactive waste areas near by Chelyabinsk and Tomsk atomic enterprises [11,12].
The increased levels of chromosome and genome aberrations were observed in the residents of Ust-Kamenogorsk exposed to the action of industrial radio-chemical wastes- heavy metal salts (lead, zink, uranium, beryllium and other transuranium elements) [9].
The increased level of aberrations in the chromatid spectrum was observed upon a long-term occupational contact with synthetic resins (polyvinylchloride, epoxy and phenolformaldehyde) and their monomers at workers of Vladimir resin plants [13].
Radiation genetics has strongly established that ionizing radiation have no minimal threshold doses: the hit of radiation quant into unique genetic structure (DNA, chromosome) can cause a break and as result of it chromosome aberrations/gene mutations (N.V.Timofeev-Resovsky). The RBE (relative biological efficiency) of highly density-ionizing a-particles is 10-20 times higher than that of low density-ionizing g-rays [14].
There is very strong evidence that the yield of chromosome aberrations (Y) is related to the dose (D) by the equation :
Y = Ao+aD+bD2
where Ao is spontaneous aberrations, a is the linear coefficient and b is squared coefficient of doses [15]. However taking into account that the dose rate of external and incorporated irradiation from rare radionuclides is not high the quadratic component may be ignored.
Then the radiation/radionuclide risk R(D) will correspond to:
1) absorbed dose D
and 2) as its aberrational/mutational consequences: R(D) = Y/Ao,
where R(D) is the coefficient of approximation of radionuclide radiation dose absorbed by the organism to a dose doubling the frequence of spontaneous aberrations/mutations.
The "doubling dose" is a basic criterion of the hazard to the human somatic/genomic health and to the population gene pool.
Quite satisfactory estimates have been obtained by the above described method for the absorbed doses both in the liquidators of the Chernobyl accident [16], and in the inhabitants of territories contaminated by radionuclides as a result of accidents at the Chernobyl NPP [17] and at the Siberian Chemical Plant in Tomsk [18] and as a rezult of nuclear explosions on the Semipalatinsk test-ground [11].
A result of prolonged influence of low-intensive radiation on the human body is the accumulation cells with chromosome/genome aberrations, that very often preceede the development of several syndromes: chronic fatigue, secondary immunodeficitncy, early aging, oncology, reproductive disfunction and etc. [19,20]. The study of the influence for one of most wide- spread in environment radionuclides cesium-137 on human organism has shown at multitude of the mutual-connected changes in the various organs. The small (on the level of energetic potential) quantities of the radiocesium become as very dangerous after the penetration in human organism and the internal organs, producing to death or to increasing of the existing illness. It’s necessary also to take into attention the organ-acceptance to this radionuclide in the process of its incorporation. The incorporation of the miocard by this radionuclide originates earlier than in other organs. It causes the serious structural-methabolic changes [21]. The works of Israeli and Russian genetics [22,23], which were published in last years, are important especially. As it has shown in the work [22], the exposure to low-dose radiation could cause heritable changes in germ cells and lead to increased load of de novo mutations in the progeny of the liquidators and other persons, which have suffered to this exposure. In the work [23] are examined the phenomenological aspects of the genomic instability induced in the descendants of the multi-divided cells having been exposed to the radiation. It is demonstrated that the regularity of the chromosome instability induction do not corresponds to the classical conception of the radiation genetics (hit principle and target theory). The medico-biological significance of this new genetic phenomenon in the child organism under conditions of low-intensive effect of small-dose radiation and its connection with the state of health are shown.
The spontaneous levels of aberrations of the chromatid, chromosome and especially genome spectra in the organisms of healthy people are extremely low: 10-2, 10-3, 10-5 per cell, respectively. Therefore, induced chromosome aberrations in blood lymphocytes may serve a measure of ionizing radiation absorbed by the organism and are objective bioindicators in assessment of the radiation/radionuclide risk for the people and ecological health.
Thus, monitoring of chromosome and genome aberrations must be of strategical importance in the system of governmental service for minimization of radionuclide and chemical hazard to human heredity and health the necessity of organization of which has already matured. The explosion at the Chernobyl nuclear power plant in April 1986 happened as a result of a whole complex of unforeseen circumstances, which led to enormous and tragic consequences. These consequences had not been predicted. This very large (planetary) disaster must serve as the basis for estimation of uncertainty of consequences of nuclear accidents in future.
The abovementioned confirms the necessity of founding a European network for ecological-genetic monitoring with "Internet" translation of information on radionuclide composition and chromosome/genome aberration levels in people, inhabiting polluted areas, with delivery of prognosis on national television [24]. Taking into attention that the main part of the territory of Western Europe is contaminated by the radionuclides of cesium-137, (T1/2 ~30 years), the actuality of problem of the creation of the all-European network of the ecological-genetic monitoring increases with the each year. On the authors''s opinion, this problem may be considered as one of the ways of practical realization of integrating precautionary principle (PP) in risk-based decision-making, which are important for the health of the population of Europe. Besides, possibility of radioactive terrorizm should be taken into consideration too.
We believe that it is necessary to take the process of development of the nuclear power industry in the XXI century under rigid public control. It is necessary, both for preservation of people’s genetic fund and for flora and fauna. The heredity and environment determine both the health of one person and of the society as whole. It is only sufficient attention to ecological problems, that can ensure the future development of democratic society.
The references see rtg-
