brechignac_f_desmet_g_eds_equidosimetry_ecological_standardi

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In the middle ages in Europe it could be talked of “horror sylvanum”, the forest being seen as dangerous, unknown and generally bad to Man. Think of the fairy tales involving frightening adventures in dark, hostiles forests.

The third technological revolution, the industrial one, is characterized by the addition in the biosphere of substances that are not naturally present or only in minute amounts, like mercury, for example, and the accumulation of not degradable wastes. But the most prominent feature of the industrial revolution is the massive consumption of energy mainly from fossil not renewable sources.

If we go back to our concept of equidosimetry, what can we find for the modification of the ecosystem? In a project like the European ELISA [6] project a whole series of indexes have been developed, such as Habitat coherence, Structural complexity, Habitat extent, Habitat connectivity, and for Species presence, trends, diversity, populations, Flagship species… In these indicators, we may find the number of species in a definite surface area, the number of endangered species, the number of protected species, or the area of protected natural parks, and so on.

However, all changes in the environment, even if they are losses, are not necessarily directly or immediately bad for man. Only a massive deforestation could ensure enough food production for an expanding population. After all, one can very well live without Blue Whales in the Ocean, or without Elephants in North Africa. Agricultural landscapes are often very suitable and pleasant, and conservation may sometimes appear as a romantic idea of a lost paradise.

Possible hazards which are not easily quantified, may be referred as the loss of possible resources, and the harm to the interdependence of all nature.

The loss of possible resources may the disappearance of a particular endangered species only capable of synthesizing a molecule which could prove useful drugs used in medical applications. The rarefaction of the global genetic patrimony could also impair future life development on the planet.

But the studying ecology teaches us that everything is interdependent. An old examples of this is the pollinisation of plants by insects, known since antiquity. The dependence of the predators on their preys is obvious. What may be less obvious, is that the well-being and health of the preys depends also on the predator. When great predators are absent, proliferation, aging and decay of herbivorous population may be sometimes observed. Phenomena like El Nino in the Pacific Ocean show how a single change in water temperature can modify deeply the vegetal and animal populations, and finally affect resources available to Man.

The virtual disappearance of untouched areas, the ever growing energy consumption, the modifications of natural cycles such as the one of carbon or sulfur, or even nitrogen, may be triggers that will bring majors unexpected changes. All this is yet to evaluate in a concept of equidosimetry.

7. Other hazards

If we leave the field of environment and come a little more on that of specifically human hazards, among them poor education, endemic diseases such as malaria, lack of adequate food, and so on. This is a vast subject, and since our starting point was radioactivity, we will take the example of iodine.

There have been some nuclear events [7] leading to a spreading of radio-

iodine:

The “bravo” test of a nuclear weapon in Bikini in 1954, where 250 atolls resident were exposed with an average global dose of 1,9 Gy. Thyroid deficiency and

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cancer of the thyroid occurred. The frequency of these diseases increased with the dose, 10 Gy leading to 50 % of thyroid deficiency. The occurrence decreased with age. On the Rongelap atoll 5 of the 6 children under 1 developed thyroid deficiency, 13 % for the children above 10.

The atmospheric tests in Nevada, Semi-Palatinsk, and the Windscale accident also led radio-iodine exposure but for these events, effect were either not observable, either there are no consolidated data.

The Tchernobyl accident led to the exposure of hundred thousand of people, with doses to the thyroid reaching or even exceeding 1 Gy for 1 y old children. More than 15000 children could have received more than 1 Gy, 5000 more than 2 Gy and 500 more than 10 Gy. Starting around the year 1990 a marked increased in the thyroid cancer among children below 15 at the time of the accident was observed. 1800 cases of cancer have been counted between 1986 and 1998, instead of a few tens expected.

All this is very serious, and of course, it deserves a close attention, not only to give adequate treatment to the sick, but also to have the means of deriving an adequate dosimetry, which we probably have, and most of all to avoid new episodes involving the release of radioactive pollutants.

But if we talk about equidosimetry, there is another plague involving iodine, it is the lack of this (stable) element. Iodine is an element present in small quantity (15 to 20 mg) in the human body, mainly in the thyroid, and it is necessary to the making of thyroid hormones which are essential to the metabolism and to the process of growth. The needs [8] for iodine are evaluated to be of 90 µg/day for the child between 0 and 6, 120 µg/day between 6 and 12, 150 µg/day for the teenagers, and 200 µg/day for the pregnant and nursing woman. At the level of a population, the lack of iodine leads to dysfunction of the thyroid, goiter, fertility trouble, increase in postnatal mortality, and mental retardation. It has been estimated that in 1990, about 1572 million people (28 % of the total world population) was exposed to a lack of iodine. 11,2 million people was affected by endemic cretinism, the extreme form of mental retardation due to the lack of iodine, and that 43 million people suffered from some kind of mental retardation. All this is potentially avoidable, provided that a source of iodine is made available to the concerned populations, generally under the form of iodine added to table salt, cattle feeding salt or alimentary industry salt. In 1990 only 5 % of the concerned populations had access to iodine complemented salt, and. about 68 % in 1990, thanks to the combined actions of concerned countries, and international organisms such as WHO, World Bank UNICEF…. Although this is a public health success a lot is left to do for some countries, and to avoid a new degradation of the situation resulting from international politics, conflicts…

There may be in the world over majors health problems, but the point here is to show that so far there is no kind of dosimetry to evaluate their consequences, and no tool like the calculation of radioactive doses, which lead to a satisfactory exposure – effect relationship.

8. Conclusion

Starting from the familiar background of radiotoxicity, this brief outlook showed us that there is not so far a common scale to evaluate and compare the potential adverse effects of pollutants, diseases or others to the environment and man.

We live in a paradox where, at least for a part of the world population, never in the past the conditions of life have been as favorable, with controlled environment, sufficient food of great quality, education, medical care and so on.

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But at the same time it is easy to see that this so-called western way of life leads to an over–consumption of natural resources that may be problematic to sustain in the future, and that for this reason is hardly extendable to mankind at large. In all cases, it is difficult to imagine that the world population will continue its growth without very serious difficulties in the future.

Therefore even if the tool for equidosimetry is not ready, at least it is time to lay flat all the environmental problems and to rank them by order of maximum threat to the future and try to treat them. But a country alone cannot do this, because it may involve a major strategic change, in a world where no one is isolated anymore.

Finally, we have not talked about a powerful engine for the development of protection tools like radioprotection, estimation of the consequences of pollutants, and others. Although it is wise when a danger occurs to seek the ways to evaluate it and learn how to protect ourselves from it, we have seen that there is no equivalence of evaluation between all the potential hazards.

Radioprotection seems to be a relatively accurate science, with adequate dosimetry, well known dose – effect relationships, eventually medical treatment, etc. This is no doubt due to the fact that the adverse effects of newly discovered radioactive products were identified in a developed and scientific world. It is also due to the fact that the effects of the atom bomb were so astonishingly devastating that it induced in the population a fright that pushed the politic and scientific community into precise evaluation of the consequences of nuclear industry. It was a good thing, and the thought process behind radioprotection could be usefully spread.

But fear, and its consequence, stress, is not always a good counselor. The huge cattle slaughters deriving from the mad cow disease may appear as an silly over reaction.

When the energy consumption is ever growing, the fear of radioactivity that leads countries to abandon clean nuclear power, thus dilapidating precious fossil fuel resources, aggravating greenhouse gases emission and disruption in great natural cycles, should be tamed.

Before trying to go further and extending the concept of dose, we should answer these questions:

Is it possible to consider the problems globally because we know it now, since we have seen the picture of the earth from the moon, we live in a finite world?

And

Is a controlled change still possible?

It is therefore more important to concentrate on what is dangerous, than on what is frightening.

9. References

[1]Henri Métivier; Les bases de la protection radiologique; cours de l’Institut National des Sciences et Techniques Nucléaires, 2002

[2]IRIS database. Internet http//www.epa.gov/iris/ ; accessed on April 12 2002

[3]Mission interministérielle de l’effet de serre. Site internet http//www.effet-de-serre.gouv.fr ; accessed on 19 March 2002.

[4]Internet site http//www.epa.gov accessed on 20 March 2002

[5]François Ramade; Eléments d’écologie appliquée ; McGraw Hill, 1978.

[6]Site internet http://www.ecnc.nl/doc/projects/elisa.html, accessed on 12 March 2002

[7]A. Flüry-Hérard et F. Ménétrier ; Conséquences sur la santé des iodes radioactifs libérés en cas d’accident nucléaire. Journée les iodes radioactifs ; l’iode stable, 15 février 2002, Institut Curie, Paris.

[8]François Delange; Nutrition iodée et développement du jeune enfant ; Journée les iodes radioactifs ; l’iode stable, 15 février 2002, Institut Curie, Paris

AN EQUI–DOSIMETRIC APPROACH TO THE COMPARISON OF RADIATION AND CHEMICAL EFFECTS ON NATURAL POPULATIONS OF AQUATIC ORGANISMS

V. TSYTSUGINA

The A.O. Kovalevsky Institute of Biology of the Southern Seas, NAS, Nakhimov Prospekt, 2, Sevastopol, 99011, UKRAINE

1.Introduction

Cytogenetic studies of natural populations of aquatic organisms show that chromosome damage is induced by radiation and chemical factors [1–3]. Therefore it is important to provide equi–dosimetric assessment of effects caused by ionising radiation and chemical pollutants [4-7].

We propose an approach which makes it possible to determine deleterious factors and to compare their efficiency. The approach is based on comparing cytogenetic effects in the mutagen equivalent doses. In this method several cytogenetic criteria (a % of cells with chromosome aberrations, a distribution of aberrations in the cells, a number of aberrations per aberrant cell) are used.

2.Distribution of chromosome aberrations in the cells

2.2. DISTRIBUTION OF CHROMOSOME ABERRATIONS IN CELLS IN THE EXPERIMENTAL MUTAGENESIS

On the basis of the experimental study of separate and combined effects of ionising radiation and chemical mutagens on the aquatic organisms (Table 1) a general conclusion was made concerning distribution of chromosome aberrations in the cells [3]:

where:

R is ionising radiation, C is chemical mutagen, R’ & C’ indicate the dominant impact in the combination, m is the mean number of chromosome aberrations per cell, n is the number of chromosome aberrations in a cell, q is the fraction of aberrant cells.

It is shown that the observed distribution of radiation – induced chromosome aberrations in the cells fits the Poisson distribution more closely than the geometric distribution. For the distribution of aberrations produced by chemical mutagens the reverse is true, i.e. the geometric distribution provides the best fit to the data. Under the impact of both factors, the observed distribution fits well the Poisson

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F. Brechignac and G. Desmet (eds.), Equidosimetry, 43–49.

© 2005 Springer. Printed in the Netherlands.

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Table 1. Distribution of chromosome aberrations in cells of crustacean and fish embryos (experimental mutagenesis) [1, 3]

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distribution if ionising radiation has greater influence. The observed distribution provides the best fit to the geometric distribution if both factors are comparable in effect or chemical mutagens have a greater influence.

2.3. DISTRIBUTION OF CHROMOSOME ABERRATIONS IN CELLS OF THE AQUATIC ORGANISMS FROM NATURAL POPULATIONS

A study was made of the distribution of chromosome aberrations in the cells of marine and freshwater organisms before and after the ChNPP accident [1-3] (Table 2). It can be seen that before the Chernobyl accident the distributions of chromosome aberrations in cells of the aquatic organisms (crustaceans and fishes) fit well the geometric distribution. It is probably, therefore, that chromosome damage in these aquatic organisms was induced by chemical pollutants.

After the Chernobyl accident the distributions of the chromosome aberrations in cells of the aquatic organisms fit the Poisson distribution only in water bodies with a higher level of radioactive pollution (the Chernobyl 10-km zone). In other water bodies in the Chernobyl zone as well as in the Dnieper River and the Black Sea the distributions of chromosome aberrations in the cells of worms, mollusks, crustaceans and fishes were closer to the geometric distribution. Therefore it may be concluded that in these cases chromosome aberrations were induced either by chemical pollution or by the combined (radioactive and chemical) pollution but the contribution of chemical pollution to the total damage of natural populations of the aquatic organisms was great.

3.Comparison of the effects in mutagen equivalent doses

In order to assess radiation influence in the cases when both factors (radiation and chemical) are comparable in the effect or chemical factor has a greater influence we propose to compare effects in mutagen equivalent doses [8, 9]. The mutagen equivalent dose is estimated as a % of cells with chromosome aberrations and an additional criterion is the number aberrations per aberrant cell.

Figure 1 presents data on the number of aberrations per aberrant cell under separate and combined influence of ionising radiation and chemical mutagens in the mutagen equivalent doses (% of cells with chromosome aberrations) on crustacean and fish embryos. Figure 1 shows that the number of aberrations per aberrant cell can be a good indicator of radiation influence in the cases of combined radiation and chemical effects.

3.1. EQUI-DOSIMETRIC DATA IN THE EXPERIMENTAL MUTAGENESIS

Comparison of the effects in the mutagen equivalent doses makes it possible to assess the equivalence of ionising radiation and chemical mutagens in the experimental mutagenesis. Equivalence means the ability of ionising radiation and chemical mutagens to induce an equal number of cells with chromosome aberrations.

Data on Figure 1 allow to assess the ecological Gy-equivalent of the effects of metals and chloroorganic compounds (Gy / Πmol .l-1) [6]

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Number of cells with aberrations, %

Fig.1. Number of aberrations per aberrant cell under separate and combined effects of ionizing radiation and chemical mutagens in mutagen equivalent doses on crustacean and fish embryos.

1 – Gammarus olivii, Pb(2+) (1.9 µmol.l-1); 2 – G. olivii, chlorphene (0.4 µmol.l-1); 3 – G. olivii, 137Cs (0.5 Gy); 4 – G. olivii, 137Cs (0.5 Gy) + chlorphene (0.4 µmol.l-1); 5 – G. olivii, external gamma (3 Gy); 6 – Scorpaena porcus, external gamma (1 Gy); 7 – G. olivii, external gamma (3Gy) + Pb2+(1.9 µmol.l-1); 8 – S. porcus, DDT (0.2 µmol.l-

137 Cs / Pb (2+) = 0.3

137 Cs / chlorphene = 1.3

External gamma / DDT = 5.0

These results are similar to those obtained in the aquatic microcosm test [10].

3.2. IDENTIFICATION AND EQUI-DOSIMETRIC ASSESSMENT OF RADIOACTIVE AND CHEMICAL POLLUTION

The method of comparing effects in mutagen equivalent doses was also used for the cytogenetic study of natural populations of oligochaeta Stylaria lacustris in the lake located in the nearest Chernobyl zone (village Kopachy) and in the lake in 30 km to the South of the Chernobyl NPP (village Strakholes’e). In cells of worms from both lakes the distributions of chromosome aberrations were closer to the geometric distribution (Table 2). In worms from these lakes the mean numbers of cells with chromosome aberrations were almost equal (about 8%) but the numbers of aberrations per aberrant cell were greatly different (Fig.2).

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Thus, cytogenetic data provide evidence for the combined effect of radioactive and chemical pollution on worm population in the lake from the nearest zone of the Chernobyl accident. Dosimetric and chemical analyses confirm cytogenetic data (Table 3). In the lake from the nearest Chernobyl zone natural irradiation level was elevated by 100 times while in the other lake dose rate was comparable to natural background level.

Table 3. Dose rates and concentration of heavy metals and organic pollutants in the bottom sediments in the two lakes

Number of cells with aberrations, %

Fig. 2. Number of aberrations per aberrant cell in worms Stylaria lacustris from two lakes 1 – Kopachy, 2 – Strakholes’e.

Therefore from the data obtained it may be concluded that the combined effect of chronic ionising irradiation (dose rate 0,24 mGy.d-1) and chemical pollution on oligochaeta Stylaria lacustris in the lake from the nearest Chernobyl zone (Kopachy) is equivalent to chemical effect on these worms in the other lake (Strakholes’e)

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4. Conclusion

Approaches to the identification and the equi-dosimetric assessment of radiation, chemical and combined effects on natural populations of the aquatic organisms are proposed. These approaches are based on generalization of our previous experimental data concerning separate and combined effects of ionising radiation and chemical mutagens (heavy metals and chlororganic compounds) on crustacean and fish embryos, as well as on the results of field studies carried out before and after the ChNPP accident. For the identification and the equi-dosimetric assessment of the damaged factors it is proposed to use the following criteria: the comparison of cytogenetic effects in mutagen equivalent doses, the distribution of chromosome aberrations in cells and the number of aberrations per aberrant cell.

5. References

1.V.Tsytsugina . Chromosome mutagenesis in population of aquatic biota in the Black Sea, Aegean Sea and Danube and Dnieper Rivers, 1986-1989 Proc. of Seminar on comparative assessment of the environmental impact of radionuclides released during three major nuclear accidents: Kyshtym, Windscale, Chernobyl. Luxemburg, 1-5 October 1990, V.II, pp. 895-904.

2.G.Polikarpov,, V.Tsytsugina. Radiation effects in the Chernobyl and Kyshtym aquatic ecosystems. Radioecology and the restoration of radioactive–contaminated sites (F.F.Luykx, M.J. Frissel, eds.). Kluwer Academic Publishers. Dordrecht /Boston/ London. 1996. pp. 269-277.

3.V.Tsytsugina. An indicator of radiation effects in natural populations of aquatic organisms. Radiation Protection Dosimetry, 1998. V.75, N 1-4, pp. 171-173.

4.G.Polikarpov. Biological aspects of radioecology: objective and perspective. Proc. of the international workshop on comparative evaluation of health effects of environmental toxicants derived from advanced technologies. 1998. Chiba, January 8 – 30. Tokyo: Kodansha Scientific Ltd., pp. 3 – 15.

5.G.Polikarpov. Effects of nuclear and non-nuclear pollutants on marine ecosystems. Marine pollution. Proceeding of a Symposium held in Monaco, 5-9 October 1998. IAEA – TEC DOC –1094. IAEA – SM

– 354/22. International Atomic Energy Agency. 1999, pp. 38-43.

6.G.Polikarpov, V.Tsytsugina. Comparison of cytogenetic and ecosystem efficiency of radioactive and chemical mutagens in the hydrobiosphere. Reports of National Academy of Science of Ukraine, 1999, ¹6, pp. 199-202 (in Russian).

7.G.Polikarpov. The future of radioecology: in partnership with chemo-ecology and eco-ethics. J. Environ. Radioactivity, V.53, ¹ 1, pp. 5-8.

8.Ch.Auerbach. Mutation research. Problems, results and perspectives. London-New York, 1976, P. 450.

9.L.J.Stadler, G.F.Sprague. Contrasts in the genetic effects of ultraviolet radiation and X-rays. Science, 1937, V.85, pp.57-58.

10.S. Fuma, K. Miyamoto, H. Takeda, K. Yanagisawa, Y. Inoue, N. Sato, M. Hirano & Z. Kawabata. Ecological effects of radiation and other environmental stress on aquatic microcosm. . Proc. of the international workshop on comparative evaluation of health effects of environmental toxicants derived from advanced technologies. 1998. Chiba, January 8 – 30. Tokyo: Kodansha Scientific Ltd, pp. 131 – 144.