Health Effects of the Chernobyl Catastrophe
Goncharova R. I.
Institute of Genetics and Cytology, National Academy of Sciences
Akademichnaya St., 27, Minsk, 220072, REPUBLIC OF Belarus
My report is devoted to the memory of Solange Fernex (1934-2006), a prominent French pacifist activist and politician, the former member of the European Parliament,
for her stubborn struggle for the full information on the health and other effects of the Chernobyl catastrophe in all the affected countries, including France, and for development of the adequate health assistance to affected populations.
Doctor Rosalie Bertell and Solange Fernex were initiators of the organization of Permanent People’s Tribunal, Session on Chernobyl in Vienna in 1996.
Solange Fernex actively participated in the work of Permanent People’s Tribunal, Session on Chernobyl.
Solange Fernex was the final editor of the book: Chernobyl Environmental, Health and Human Rights Implications
Solange Fernex has made the report “Health effects of Chernobyl: a dogma or a quest of truth?” at 3td International Conference: “ Health Effects of the Chernobyl Accident, Results of the 15-years Follow-up Studies” in Kiev in 2001
The Chernobyl accident has caused the deposition of radioisotopes over very wide areas of the Northern Hemisphere, in particular in Europe (Atlas of Caesium Deposition on Europe after the Chernobyl Accident, 1998), followed by chronic exposure of many millions of people to a mixture of external and internal radiation. You can see the map of radioactive contamination of Europe after the Chernobyl accident.
However, the Republic of Belarus was affected by the accident more than any other country of the world. According to the Atlas practically the whole territory of Belarus was contaminated with different radioisotopes above the level of global fall-out. The ground deposition density equal to 37 kBq/m2 is accepted as a limited value for distinguishing the so-called “clean” regions from the contaminated ones making up 23% of the country area. So, 22 years after the world’s worst nuclear accident the entire population of Belarus is involuntary taking part in a decades-long experiment on how low doses of radiation affects human health.
Clear understanding of this fact is of great importance for interpreting the effects recorded.
Since 1986 we have been studying the biological effects of chronic low dose radiation in natural populations of wild small mammals named bank vole, in laboratory mice and evaluating remote consequences of the Chernobyl accident.
Here, on the map of Belarus, you can also see monitoring sites. These sites are located at different distances from the Chernobyl nuclear power plant and represent different levels of radioisotope contamination:
Priluksky reserve (near Minsk, 330 km north-west from the Chernobyl power station, 8 kBq/m2);
Berezinsky Biosphere reserve (Vitebsk region, 400 km NNW, 18 kBq/m2);
The vicinity of Majsk village (Bragin district of Gomel region, 60 km N, 220 kBq/m2);
The vicinity of Babchin village, exclusion zone (Khoiniki district of Gomel region, 40 km NNW, 1530 kBq/m2). Now it is Polessky Radiation reserve.
The vicinity of the Radin village, exclusion zone (Khoiniki district of Gomel region, about 18 km N, 8500 kBq/m2). Now it is Polessky Radiation reserve.
Bank voles are collected at 5 trapping sites different in radionuclide ground deposition. These data is given on this slide.
The data on 137Cs, 134Cs, 106Ru, 144Ce contamination were obtained in the year of accident (1986). The concentrations of 90Sr and transuranic elements in samples of soils were measured in 1996.
It is necessary to note that after the primary insult in the year of the accident, every successive generation of animals under investigation was exposed to permanently decreasing whole-body dose rates of ionizing radiation.
United Nations Chernobyl Forum under the aegis of WHO issued the massive report on the health and environmental consequences of the accident. The WHO report “Health Effects of the Chernobyl Accident and Special Health Care Programmes”(2006) confirmed radiation induced huge increase of the thyroid cancer in those exposed in childhood and adolescence and declared that there has been no significant increase so far in the incidence of other cancers and congenital malformations that can be attributed to radiation exposure. It is intriguing to note that prognosis estimate of future deaths due to the Chernobyl is much less in Joint News Release WHO/IAEA/UNDP “Chernobyl: the true scale of the accident; 20 years later a UN report provides definitive answers and ways to repair lives” and the report’s 50-page summary in Health effect of Chernobyl fallout that firmly established
The established health consequences of the Chernobyl
Reconstruction of iodine–131 fallout has shown that the whole territory of the Republic of Belarus was contaminated this isotope (National report, 2006).
On this slide you can see calculated collective thyroid doses for two age groups, namely for children and adolescents and for adult at the time of accident, for all regions of Belarus.
For the time being scientific society has accepted only significant increase of thyroid cancer incidence in children and adolescents. Growth of thyroid cancer in adult population has not been reported in official scientific conferences as a proved scientific fact.
As for concerning whole body absorbed doses, the data on collective effective dose you can see on this slide. According to the National report of Belarus, 2006, table 3.11) up to 90% of collective cumulative effective dose was formed in the first decade after the accident.
Annual collective dose to population residing on the territory of radioactive contamination is about 21 person-Sv, average individual dose is 0,15 mSv.
For all of exposed groups, estimates of numbers of fatal cancers can be derived from collective doses. Such estimates depend on the assumed risk coefficient
The incidence of thyroid cancer in those who were adults at the time of exposure is reported to have increased in the many exposed populations, including Poland (Mahoney, Ostapenko, 2004), although the relationship to radiation is not so clear. Time course of thyroid cancer incidence among childhood and adult populations of Belarus up to 2001 have been shown on this slide.
According National Report of Belarus, 2006 thyroid cancer incidence continues growing steadily among adult population of Belarus.
The concentration of effort on the major increase in those exposed as children has meant that the smaller risk to adults has not been adequately investigated.
As for concerning future estimates of thyroid cancer for Belarus it is necessary to note.
Currently, individuals exposed as children are now adolescents or young adults but continue to carry an increased risk of developing thyroid carcinoma during all lifespan.
For predicting, we have to know risk coefficients obtained on the basis of studying suffered populations. Depending of the calculated values of risk coefficient, the predicted values of the future incidence of thyroid cancer differ greatly. The latest estimate for the year 2056 ranges from 3,400 to 72,000 according Cardis et al., 2006 (Estimates of the cancer burden in Europe from radioactive fallout from the Chernobyl accident, Int J Cancer).
According estimates of Malko, in Belarus alone, approximately 31,400 additional thyroid cancers (15,400 to 47,400) are expected. For France this estimate is 678 –1,153 additional cases, for Germany –1,479-2,514, for Romania –2,239-3,976.
Slide 9 standardized incidence rate
It is very important to assess an incidence of other cancers. I already mention that the fact of additional increase of other tumors among the population and liquidators is considered as not being evident.
It is relevant to the current view of Chernobyl impact on human health to reflect on the understanding in 1965 of the health effects of radiation from the atomic bombs in Japan in 1945 year. The only significant consequences observed in survivors 20 years after the atoms bombs were increases in leukemia and thyroid cancer, and the general view of the future was reassuring. But in 1974, a significant increase in solid cancers was detected from survivors with dose estimates in excess of 1Gy. But they comprise less than 3% of the cohort. In the full LSS cohort of 120,321 individuals about 48% were still alive at the end of 1998.
The analyses of the mortality from cancer diseases in the atomic bomb survivors over the period of 1950–1990, i. e. over 40 years of follow up, has revealed the statistically significant radiation effects beginning from 0.2Sv (200 mSv or 20 rem) (Pierse et al., 1996).
In 2000, Pierce and Preston evaluated solid cancer incidence for the period of1958 through 1994 focusing on the subcohort of about 50,000 lSS survivors who had dose estimate of less than 0.5 Gy to clarify cancer risks at low doses. They concluded there was a statistically significant dose response in the range of 0–0.15 Gy. This conclusion was confirmed by new publication Preston et al., 2007 on solid cancer incidence in atomic bomb survivor: 1958–1998. The authors write “ there is a statistically significant dose response when analyses were limited to cohort members with doses of 0.15Gy or less”.
Today, leukemia and thyroid cancer form only a small fraction of the accepted total radiation related health detriment of atomic bombs.
That is why it is too early to assess the overall impact of Chernobyl fallout on human health and animal populations.
According prof. Alexej Okeanov, 2007 the data on Incidence of malignant tumors among different groups of Belarusian population are as follows;
Among population living on the territories with ground deposition of 37–555 kBq/m2, an increase of relative risk of colon cancer, breast and thyroid cancer was found. There is statistically significant increase of breast cancer incidence in women, the most intensive in the age of 20–40 years. Population of this territory presents the most numerous of all follow up groups and includes 1,245 individuals.
You can see data on a relative risk of malignant tumors incidence among the population living in regions with density contamination of 37-555 kBq/m2. Population of this territory presents the most numerous of all follow up groups and includes 1,245 individuals.
Relative risk (RR) was calculated as ratio of standardized rate (TASR) of incidence among different exposed groups to the incidence of the control group (non-exposed group). Vitebsk region was accepted as a control region as far as its population was exposed to Chernobyl fallout much less. Vitebsk region is considered as so-called clean region.
Comparative analysis of relative risk of cancer incidence showed the considerable growth in 1997-2003 as compared with the previous period 1993-1996.
The period 1997-2003 was characterized by significant increase of cancer incidence of all sites including colon, mammary gland, skin and thyroid.
For the period of 1990–2003 there is a statistically significant increase of breast cancer incidence among women of Gomel region in comparison with appropriate value among women living in the less contaminated areas. Particularly, dose dependent three fold increase of breast cancer incidence was shown from women of Gomel region (National report, 2006).
At the same time the report of the Chernobyl Forum in Vienna, 2005 stated that the group of international experts did not reveal any evidences of leukemia and cancer growth among the inhabitants of the affected regions that can be attributed to radiation exposure.
However, a large body of data amassed by the present makes it possible to draw other conclusions concerning the health effects of low doses of radiation.
There are some reasons for such disagreement.
First of all, it is evident that a few attentions have been paid to assessment of whole body absorbed doses in comparison with the reconstruction of thyroid doses.
Therefore, we should admit non-availability of reliable data of individual and group doses appropriate for long-term cohort studies of dose dependence of the cancer incidence (mortality). For the time being, such investigations were not conducted. Only a cohort study of thyroid cancer and other thyroid diseases after the Chernobyl accident is conducting in Belarus and Ukraine, that includes 25,161 subjects under the age of 18 years in 1986.
Second, an assessment of the remote consequences of the Chernobyl fallout was reduced to the estimation of the health effects of low doses of radiation delivering with low dose rates. One of the specific features of the Chernobyl accident is long term exposure of numerous groups of population to low dose radiation. In more details, relatively high dose rate exposure (days to weeks) was followed by prolong (some decades) exposure to a low dose rate.
Before the Chernobyl disaster a reality of genetic effects of very low doses of IR remained unclear.
Slide 11 Our data
A number of studies conducted during the past two decades give reliable data about serious biological and medical effects of the Chernobyl accident and about harmful impact of irradiation at low doses and low dose rates. Such results were established for cell, animals and human.
So, we established genetic effects of low doses (less than 100 mSv) in somatic and germ cells of a model mammalian species, the bank vole, which was chronically exposed to low doses of ionizing radiation over 22 animal generations within 10 years following the Chernobyl accident (Ryabokon, Goncharova, 2006).
For example on this slide you can see the dose response curve for total chromosome aberrations frequencies and those of the Robertsonean translocation in bone marrow of bank voles inhabiting fives sites with different ground deposition of radionuclides in 1996 year. The accumulated doses in five natural mammalian populations living in the contaminated areas range were 0.3, 0.7, 12 and 25 mGy.
The analysis of our and literature data shows that the doubling dose estimates for acute irradiation of somatic cells in bank vole and human lymphocytes as well as for germ cells in laboratory mice are close to each other (Goncharova, Smolich, 2002). Therefore, the choice of bank voles as a model species for assessing radiation genetic risk is justified.
Our data on statistically significant genetic effects of very low doses are in line with data about radiation-related cancer risks at low doses among atomic bomb survivors.
The recent general report on mortality in the cohort of atomic bomb survivors followed up by the Radiation Research Foundation give strong evidence that there is direct, statistically significant evidence of risk in the dose range of approximately 0-0.10 Sv. You can see the dose-effect curve on this slide. Pierce and Preston used Life Span Study (LSS) solid cancer incidence data for the period from 1958 through 1994 in an assessment of low-dose risks.
It is important to note that radiation-related cancer risks at low doses among atomic survivors are well established in 45 years after bombardment. It is known the lower radiation doses the longer latent periods are.
On the other hand, the recent general report on solid cancer incidence in atomic bomb survivors over 1958—1998 years (Preston et al., 2007) and publication (Pierce, Preston, 2000) have presented direct, statistically significant evidence of risk in the dose range of 0–0.15 Gy.
Whole body doses received by exposed populations of the three most affected countries Republic of Belarus, Ukraine are estimated to be in this range, i. e. within the range that led to a significant increase in cancer incidence after nuclear explosion.
Although the Radiation Research Foundation investigations are often considered the high-dose research, in reality, approximately 30% of the exposed individuals of the cohort received doses from 5 to 200 mGy (Preston et al., 2007).
Such doses of the whole body irradiation were delivered as a result of the Chernobyl accident to inhabitants of high-contaminated areas in Belarus, Ukraine and Russia too. This indicates the possibility of radiation-induced cancers caused by the Chernobyl accident.
According to the present knowledge (BEIR VII, 2006) there is no threshold for the carcinogenic effect of IR. Therefore any additional irradiation will induce additional cancers in exposed populations, not only in the three most contaminated countries but all around Europe, including France, Swiss, Germany and other countries.
It is important to note that radiation-related cancers at low doses among atomic survivors were established later than in the range of high doses. The longer latency period in case of low doses of irradiation is responsible for this effect. Thus, one needs to expect more pronounced manifestation of additional cancers from the Chernobyl accident in the future time. Particularly, dose dependent three fold increase of breast cancer incidence was recently shown for women of Gomel region (National report, 2006).
According to Malko’s estimates, in Belarus alone, approximately 28,300 solid cancers other than thyroid and non-melanoma skin cancers (11,800 to 44,800) are expected. It is nearly 6-times more (130,400 for all Europe) than predicted by Cardis et al., 2006 (22,800).
For France –1,220, for Germany – 9,280 cases.
Further, recent cellular and molecular studies have increased our understanding of low dose radiation effects, first of all induced genome instability and bystander effects.
Transgenerational accumulation of radiation damage over 22 animal generations was found by the levels of chromosome aberrations in bone marrow cells and embryonic lethality in bank vole populations chronically exposed to low doses delivered with very low dose-rates (Ryabokon, Goncharova, 2006).
Evidently, non-targeted effects of ionizing radiation such as genomic instability, bystander effects and other new phenomena have to contribute to short-term and long-term overall outcomes for human health after low dose ionizing radiation. In this connection we study a genomic instability of different risk groups in Belarusian population (Goncharova et al., 2008).
I suppose that increased thyroid cancer incidence of children from irradiated parents chronically exposed due to Chernobyl accident might be a manifestation of the induced genomic instability (Goncharova, 2005).
For the elucidation of the causal role of low dose radiation exposure due to Chernobyl fallout for the observed increases of many types of cancer and congenital malformations in Belarus (National report, 2006), long-term radiation-epidemiological studies with reconstruction of whole body absorbed doses must be carried out in the future. So far, all declaration on the absence of radiation-linked increases in the incidence of other types of cancer and congenital malformations simply means the absence of an adequate research.
There is a set of data on increased sensitivity of somatic and germ cells of animals and human to low radiation doses (Vilenchik, Knudson, 2000).
There is also similar data concerning cancer risks attributable to low doses. In this connection I would like to give you the data published by Radiation Effects Research Foundation on Excess Relative Risk for cancer mortality.
The estimated excess relative risk (ERR) per Sv for the selected dose ranges of Life Span Study cohort was the highest for the lowest dose category, namely from 0 to 20 mSv in comparison with dose range between 0 and 3 Sv.
Recently, the scientists of the RERF gave also reliable evidences of radiation effects on noncancer mortality. Statistically significant increases are seen for heart diseases, stroke, digestive, respiratory and other diseases (Preston et al., 2003).
Slide 15 conclusions
The whole body doses received by exposed populations of the Republic of Belarus, Ukraine and contaminated regions of the Russian Federation are estimated to be in the dose range of 0–0.15 Gy, i. e. within the range that led to a significant increase in cancer incidence in atomic bomb survivors.
Thyroid cancer incidence continues growing steadily among adult population of Belarus (National report, 2006)
For the period of 1990–2003 there is a statistically significant increase of breast cancer incidence among women of Gomel region in comparison with appropriate value among women living in the less contaminated areas. Dose dependence between accumulated radiation dose and realized relative risk of breast cancer was shown.
According A. Okeanow data among population living in the regions of 37–555 kBq/m2 considerable growth of relative risk of cancer incidence occurred in 1997-2003 in comparison with the previous period 1993-1996.
Summing up all these data allows us to conclude that the accident at the Chernobyl nuclear power plant will result in a number of unfavorable health consequences for both affected people and coming generations.
Particularly, an increased thyroid cancer incidence of children born from irradiated parents chronically exposed due to Chernobyl accident might be a manifestation of the induced genomic instability.
For the establishment of the causal role of low dose radiation exposure due to Chernobyl fallout for the observed increases of many types of cancer and congenital malformations in Belarus (National report, 2006), health radiation-epidemiological and cohort studies with reconstruction of whole body absorbed doses must be carried out in the future.
So far, all declarations on the absence of radiation-linked increases in the incidence of other types of cancer and congenital malformations simply mean the ignoring of data established in Belarus, Ukraine and the Russian Federation and absence of an adequate research.