Consequences of the accident on public health

Exposures Doses

200,000 people, of the total number of those who were involved in the response to the accident in 1986-1987, received average radiation doses of about 100 mSv. About 10% of them were exposed to about 250 mSv. Several percent of the responders suffered from radiation exceeding a level of 500 mSv; and there were, probably, some of the emergency workers, who participated in the immediate response to the accident, who got potentially lethal doses of several thousands mSv.

116,000 people evacuated from the Exclusion Zone in 1986, were also significantly affected by radiation. Less than 10% of them received doses exceeding 50 mSv, and less than 5% - more than 100 mSv.

The iodine radioactive isotopes contained in the releases caused exposures doses to the thyroid gland. Estimations of equivalent thyroid gland doses (calculated first of all on the basis of screening results done for 150,000 people in Ukraine, and also in Belarus and the Russian Federation) amounted to several Gy.

According to the estimations done within the framework of International Chernobyl Project, the highest expected doses during the period of 70 years (from 1986 till 2056) for the people, who live in the most contaminated territories, will be up to 160 mSv. Recent more detailed research gave similar results. During the period from 1996 to 2056, expected doses received by people, residing in areas with contamination density of 185-555 KBq-2, commonly, will be about 5-20 mSv. Nevertheless, in areas where the radionuclide transfer factors from soil to vegetation are particularly high, internal exposure alone can exceed 50 mSv during 70 years.

The studies showed that accumulated population exposure doses during 1986-1997 (excluding doses for thyroid gland) exceed 70 mSv (the limit of allowable population exposure during the life span, according to the Concept of Ukrainian population residence in the territories with increased contamination levels as a result of the Chornobyl catastrophe) at ten residential areas. By the end of 1997, at 1,316 populated localities the average annual exposure doses still exceed 1 mSv, the level of actions as to the radiation protection adopted by the respective standard setting documents of Ukraine.

During the whole postaccident period, about 80% of the life-span dose (during 70 years of living in the contaminated territories) is already realized. At present and during the following 10-20 years, the main dose forming radionuclide is and will be cesium-137 that conditions about 90% of the total exposure dose. The doses of internal exposure amount to 90-95% of the total dose practically all of which is formed by food products. Because of this, main directions of the countermeasures on decrease of the exposure doses will be directed to the production of clean food products during the following period.

 

 

 

Social, Psychological, and Economical Consequences

The accident has significantly changed the life of the millions of people. This mainly concerns the population of Ukraine, Belarus, and Russia that resides in the most contaminated territories. Regardless of how much their health has deteriorated by exposure to the Chornobyl radionuclides, the events linked to the accident, for instance, such as relocation, restrictions on agriculture production, other countermeasures, information on contradictory assessments of the possible consequences have drastically changed the habitual style of life of these people, disturbed the traditions that were formed during hundreds of years. This especially affected the rural population.

The lack of special knowledge in radiology did not allow the population to estimate on their own the truthfulness of the information supplied by mass media. As a result the subjective assessment of the possible consequences of the accident overestimated the reality.

During 1990 and the end of 1995 the authorities adopted the decisions on further relocation of the people from the areas of radioactive contamination (it was about 50,000 people in Ukraine). Evacuation and relocation created the whole number of serious social problems linked to difficulties and complications of adjusting to the new conditions of life.

Demographical indices in the contaminated areas deteriorated: the birth rate declined, and labor force migrated from the contaminated areas to the clean ones, creating lack of professional personnel. Besides, the attitude of the population to the products from the contaminated areas complicate its realization and export, this leads to the decrease of the local incomes. All these caused both the decrease of the productive activity of the population and the working places. As the result, the economy of the regions and families deteriorated. These consequences of the economical nature could not but affect the state of the population health through the deterioration of food consumption, conditions of work and recreation.

Restrictions on the nature of activity of the people that contradict to the established traditions create extreme difficulties in the everyday life. During the post accident years, the effective protective measures were carried out. Regardless of this, a part of the population has no trust in the information about the measures diminishing the accident consequences, current radiation situation, and radionuclides concentration in the foodstuff. All this caused the feeling of anxiety over the own health and the health of the closely related people, cases of not grounded self-restriction in consumption of some food products of local production, refusal from some kinds of activity or recreation and so on. Accounting for the fact that most of the territories, contaminated with the released radionuclides, had been and remain endemic as to the content of important microelements (iodine, selenium, cobalt, fluorine, etc.), self restriction in consumption of some kinds of foodstuff (for example, milk, berries) caused diet transformation, decrease of vitamins, microelements uptake below the physiological norms. This to certain extent was reflected in the peoples health.

Social and economical situation of the people that reside and work in the contaminated areas to the great extent depends on government subsidies. If the actual compensation system were revised, some part of the financial means could be redirected to the development and realization of the new industrial and agricultural projects.

The consequences of the Chernobyl NPP accident, aggravated by political, economical, and social changes during the last years, caused the deterioration of the life quality and health state of the population and negative consequences of the social activity.

 

 

Health consequences

Byelorussia data. Health status of main groups of affected people (Table 1) is evaluated by analysis of results of dispensary of 1.6 million people including 344 thousand children, as well as data coming to the National registry of people affected by n radiation as a result of the Chernobyl accident (180 thousand people), results of investigation carried out within frames of national and international programmes by scientific institutions of the Ministry of Health.

 

 

Table 2.5-1. Main groups of people affected by the Chernobyl accident.

 

Groups of affected:

participants of recovery operations in 1986-1987

participants of recovery operations in 1988-1990

Evacuees

Relocated

Residing in contaminated territories

Children of exposed parents

 

 

Complex of factors (radiation and non-radiation origin) effecting on health status of the population cause variation in morbidity (Table 2.5-2).

 

Table 2.5-2. Main factors of the Chernobyl catastrophe effect on health status.

 

Radiation

Non-radiation

Internal and external radiation:

Dose-forming radionuclides of iodine,
cesium, strontium, transurane elements

Social

Economical

Stress

Risk perception

 

 

Radioiodine (mainly iodine-131) was one of main sources of radiation exposed to the population, mainly to the thyroid, following the Chernobyl accident. Children and adolescents, particularly children under 7 years of age, were mostly affected people in Belarus. Results of direct measurements made in 1986 showed that about 30% children under 2 years of age had got thyroid dose over 1 Gy. Average thyroid dose in younger children resided in mostly contaminated rural settlements was 3 Gy and over. During iodine period collective thyroid dose in residents of Belorussia was more than 500 thousand person-Gy. In Table 3 collective thyroid doses in residents of different oblasts of Belorussia are shown.

 

 

Table 2.5-3. Distribution of collective thyroid doses in residents of oblasts of the Republic of Belarus.

 

Oblast

Collective thyroid dose, 103 person-Gy

0-6 years

7-17 years

>17 years

Total

Brest

35.0

19.2

46.5

100.7

Vitebsk

0.5

0.3

0.9

1.7

Gomel

96.6

53.7

151.0

301.3

Grodno

16.4

9.0

24.0

49.4

Minsk

23.0

12.6

32.7

68.3

Mogiliov

9.9

5.4

16.3

31.6

Over the Republic

181.4

100.2

271.4

553

 

The thyroid has been exposed to radiation after the iodine period as well, though doses due to external and internal radiation from radiocesium is significantly less. Collective thyroid dose from radiocesium was 21 thousand person-Gy in residents of the Republic.

At the early stage following the accident and due to insufficient effectiveness of protective measures growth of thyroid cancer incidence, particularly among children, was registered in Belarus beginning from 1990. The number of thyroid cancer cases after the Chernobyl accident increased to 33.6 times compared with pre-Chernobyl period, in groups of adults the increase was 2-7 times in relation to age (Table 2.5-4).

 

Table 2.5-4. Number of thyroid cancer cases in relation to age at the time of surgery.

 

Age groups, years

Calendar years

1972-1985

1986-2000

0-18

29

975

19-34

227

1158

35-49

341

2334

50-64

461

2002

65 and more

404

1035

TOTAL:

1472

7504

 

 

The greatest number of thyroid cancer cases is detected among residents of Gomel and Brest oblasts.

Unprecedented increase in thyroid cancer incidence required decisions towards improving organisation of health care to be delivered to this group of people. For these purposes Republican Scientific and Practical Centre of Thyroid Tumors, Division for Rehabilitation located at the Clinics of Research Clinical Institute of Radiation Medicine and Endocrinology, Division of Radioiodtherapy at the Gomel Oblast Cancer Dispensary was set up. Close collaboration with Wurzburg University (Germany) was established. Treatment of thyroid cancer patients includes surgery (total thyroectomy with neck dissection), radioiodtherapy for ablation of thyroid tissue and treatment of metastases, suppressive therapy with L-thyroxine and subsequent rehabilitation. Application of complex treatment allowed one to reduce lethality among thyroid cancer patients, children and adolescents, up to 0.3%.

Average annual indicators of leukaemia incidence among children of six oblasts of Belarus have been stable for the post-Chernobyl period. There is a trend to increase in leukaemia incidence among old people, however, it is impossible to find effect of radiation factor on the incidence.

Rates of morbidity among liquidators of 1986-1987 are higher compared to the population of similar age who were not examined by special mode. There is significant difference between incidence of endocrine disorders, diseases of the circulation, digestive system, ischemic heart disease, malignant neoplastic formations among liquidators compared with the population (Fig. 2.5-1). There is significant polymorbidity among this group of affected people. Available epidemiological and dosimetric information dose not allow us to estimate the contribution of radiation factor to different levels of morbidity.

 

 

Fig. 2.5-1. Ratio of growth of morbidity among liquidators of 1986-1987
compared with the population of
Belorussia not taken special examination.

 

 

The rate of primary disability among liquidators is 1.6 times higher compared with adult population of the Republic (114.3 and 71.6 per 10000 people respectively). Main causes of primary disability are diseases of the circulation system and neoplasms. Rate of mortality among liquidators is still less compared with that among adults.

It should be noted that that registered enhanced level of morbidity among the population and liquidators can be cause not only by radiation and non-radiation factors of the Chernobyl catastrophe but so called screening effect as well. To elucidate the contribution of radiation factor to changing of health status of affected people long-term radiation and epidemiological studies are necessary. Some of the studies are currently performed within frames of national and international programmes.

Reliable increase in the rate of some congenital defects of development compared with that before the accident was registered in the population of Belarus residing in territories with 137Cs contamination density over 555 kBq/m2 (Fig. 2.5-2).

Fig. 2.5-2. Rate of some congenital defects of development in the population
of
Belarus residing in territories with 137Cs contamination density
over 555 kBq/m2.

 

 

Observed increase in disorders of development in utero occurred among the population of Belarus must be considered as a result of complex of adverse effects on reproductive function. Among these factors the main contributors are physical mutagens (radionuclides), chemical embriotoxines and poor diet. Such conclusion must be confirmed by further large-scale studies. Current system for dynamic follow-up of people affected by the Chernobyl accident and annual medical examination allow one to detect diseases and undertake necessary therapeutic and rehabilitation measures in due time for improving health status of affected population.

 

 

Russian Federation data. To make prediction for delayed radiation effects the following must be known:

                        adequate model for prognosis at the range of low radiation doses which are characteristic of the Chernobyl accident;

                        individual dose estimates for people exposed to radiation.

Let us consider the problem for liquidators. Scientific literature and mass media discuss the problem many times, often estimates made are conflicting. UN Scientific Committee for Effects of Atomic Radiation comprehensively considered the matter at its Session in Vienna on May, 2000 the confirmed correctness of dosimetric data on liquidators collected at the Registry.

So, on the basis of linear non-threshold hypothesis of ICRP and doses from external radiation exposure to liquidators delayed radiation effects of induction of cancer diseases can be predicted.

At present time Russian National Medical and Dosimetric Registry has data on 570 thousand people including 180 thousand liquidators of the Chernobyl accident (Fig. 2.5-3).

 

Fig. 2.5-3. Distribution of registered individuals by groups of primary registration
(570 thousand people).

 

 

Let us consider prognostic estimates for liquidators of 1986 who got the highest doses from external exposure (average dose is 16 cGy) (Fig. 2.5-4).

 

 

Fig. 2.5-4. Distribution of liquidators by the year of their arrival at the zone
of the accident and received radiation doses.

 

So, in 2000 solid cancers (all types of malignant neoplasms excluding leukaemia) can be detected in 385 of 100000 liquidators of 1986 (Table 2.5-1). The main question is how many the cases are associated with radiation. On the basis of individual dosimetric data of the Registry and with the use of State of the Art models for prediction of radiation risks one can state that 18 of 385 cases (4.7%) only will be induced by radiation dose from external exposure got due to recovery operation.

 

Table 2.5-1. Prediction of effects of radiation on participants of Chernobyl recovery operations.

 

Year of arrival at the Chernobyl zone

Cancer diseases
per 100 thousand

Expected in 2000

Risk for a whole life

Overall

Radiation-associated

Overall

Radiation-associated

1986

Solid cancers

385

18 (4.7%)

21638

1089 (5.3%)

Leukaemias

11

4 (36.4%)

485

113 (23.1%)

1987

Solid cancers

366

10 (2.7%)

19922

581 (2.9%)

Leukaemias

9

2 (22.2%)

430

59 (13.7%)

1988-1990

Solid cancers

328

4 (1.2%)

19532

228 (1.2%)

Leukaemias

8

1 (12.5%)

392

22 (5.6%)

 

 

Let us consider leukaemias incidence among liquidators of 1986. It is expected that 11 leukaemia cases among 100000 liquidators will be detected in 2000. Four of eleven cases (36.4%) will be associated with radiation. If we compare two indicators percentage of radiation-induced solid cancers (4.7%) and leukaemias (36.4%) one can say that radiation risk for leukaemia exceeds the risk for solid cancer by more than 7.5 times. At the same time leukaemia incidence rate is 35 times lower than solid cancers incidence rate.

As it is mentioned above, the Registry consists individual medical and dosimetric data on 180000 Chernobyl emergency accident workers. It is expected that 37109 solid cancer cases will be detected for their life, 1340 (3.6%) of 37109 cases will be associated with radiation. In the above group of liquidators, 179923 people, 809 leukaemia cases are expected to be detected, 138 cases (17%) will be associated with radiation.

Let us consider results of prognostic estimates of radiation-induced cancer among residents of contaminated with radionuclides territories of Russia. The mostly affected people live in Bryansk, Kaluga, Tula and Oriol oblasts. Calculations resulted in the excess of radiation induced solid cancer prevalence among all residents of Bryansk oblast to be 0.3%, the prevalence of leukaemia to be 1.2%. The most favourable prediction is made for radiation induced thyroid cancer developed by those who were children at exposure.

Let us consider leukaemia incidence among liquidators. Researchers of Japan stated that the highest radiation risk is for leukaemia.

On the basis of the analysis of leukaemia incidence among liquidators occurred for the passed years the following conclusions can be drawn.

 

 

First, in 2.5-3 years after the accident leukemia incidence among liquidators did not differ from baseline. Annually 5-7 cases per 100000 people were registered. In statistical reports the same number of leukemia cases was registered among male population standardized by age.

Second, during 1992-1995 after ending the latent period for induction of radiation induced leukemia twofold increase in incidence rate among liquidators compared to the spontaneous level was registered. The peak of the incidence was in 1992-1995, the peak was independently registered by National Chernobyl registries of Ukraine and Belarus in the same period.

Third, in recent few years of follow-up (1996-2000) leukemia incidence rate has dropped and moves to the expected (spontaneous) level.

So, it is possible to say that prediction for the development of radiation-associated leukemia among liquidators is confirmed by actual data of the Registry; relationship between dose and the event within the range of low doses has been detected.

Recently drastic growth of disability rate among liquidators of 1986-1987 has been observed. At the same time we have not detected dose-effect relationship for the incidence rate (Fig. 2.5-5). Data of the Registry show that mortality rate among liquidators does not exceed the rate among males of Russia in whole (Fig. 2.5-6).

When prediction of delayed radiation effects on the population was made we had expected unfavorable situation concerning thyroid cancer particularly thyroid cancer in Bryansk children at exposure. What are actual data? Regretfully, expected situation has been confirmed completely. Among Bryansk children at exposure about 30% of all detected thyroid cancer cases were associated with radiation form incorporated 131I (Fig. 2.5-7, 2.5-8).

 

 

 

Fig. 2.5-5. Temporal variations of disability rates among liquidators.

 

 

 

Fig. 2.5-6. Temporal variations of mortality structure (for liquidators).

 

 

 

Fig. 2.5-7. Thyroid dose and radiation risks in children (Bryansk oblast).

 

Fig. 2.5-8. Thyroid dose and radiation risks in children (Oriol oblast).

 

 

 

Ukraine data. As of 01.01.97 status of liquidators was given to 363780 individuals, 253511 people are under dispensary follow-up, 205809 people have been registered at National Registry of Ukraine. Military medical registry of the Ministry of Internal Affairs and the Service for Security of Ukraine consists 36 thousand liquidators. More than half (53%) of liquidators took part in recovery operations in 1986, 24.4% - in 1987.

Stable negative changes of health status of liquidators were observed. From 1988 to 1998 the portion of healthy liquidators of 1986-1987 dropped in 7 times (from 67.6% to 9.6%), the portion of healthy liquidators of 1988-1989 dropped by a factor of 5 (from 58.7% to 12.4%). Growth of non-tumour chronic diseases was observed. These diseases are the main cause of disability and death among liquidators. Incidence and prevalence rates in the subjects under study exceeds the population level (Fig. 2.5-9).

 

 

Fig. 2.5-9. Temporal changes of incidence and prevalence of diseases
(per 1000 individuals) among liquidators and adults of
Ukraine.

 

 

The most pronounced increase of diseases of the endocrine, nervous, genitourinary, musculoskeletal systems, blood and hematopoietic organs, circulation, neurocirculatory asthenia occurs.

The relationship between growth of morbidity and the period of recovery operations was found. The magnitude and growth rate of morbidity was higher in the cohort of liquidators of 1986-1987 compared with that among liquidators of 1988-1989 (Fig. 2.5-10).

 

 

Fig. 2.5-10. Temporal changes of incidence and prevalence of diseases
(per 1000 individuals) among liquidators in relation to the year of recovery operations (materials of the National Registry of Ukraine).

 

High level and the rate of growth of disability occurs among liquidators. According to data of the National registry of Ukraine disability rate has been about 170 times more for the passed time. More significant disability growth rate is observed among liquidators of 1986-1987 and in those with radiation doses exceeding 250 mSv (Fig. 2.5-11). In about of 84-86% cases disability is caused by neurologic diseases, disorders of the circulation and digestion systems. In 1988 traumas and poisoning were the main causes of disability.

 

 

Fig. 2.5-11. Temporal variation of disability (per 1000 individuals) in liquidators of 1986-1987 in relation to external radiation dose (data of National Registry of Ukraine).

 

 

Annual growth of mortality among liquidators is close to that among the able-bodied population of Ukraine. Twofold increase in average annual rate of mortality caused by circulatory, respiratory, digestive diseases, disorders of the endocrine systems has been registered for the recent 6 years. At present time circulatory diseases are the main cause of death.

 

Health status of adults residing in territories of Ukraine contaminated with radionuclides

 

In 1999 the National registry of Ukraine of persons affected by the Chernobyl catastrophe consisted 249 thousand individuals (112.2 thousand men and 136.8 thousand women) resided in territories contaminated with radionuclides. Thyroid doses are known for 14506 people (5.8%), in 3705 individuals thyroid dose is less than 30 cGy, in 5746 - 31-75 cGy, in 4355 - 76-200 cGy, in 700 people - 201 cGy and higher.

Prevalence of diseases among the affected adults increases in 2.1 times, incidence - 1.6 times from 1988-1997. Diseases of blood and the circulatory system were 10.8-15.4 times more, the endocrine system - 4.1-8.1, the nervous system - 3.8-5.0 times, skin and subcutaneous cellular - 4.0-4.6 times. Twofold increase in morbidity of digestive diseases, disorders of the genitourinary, skeletal and muscle systems increases was registered. Because growth of morbidity rate has been more pronounced in radiocontaminated territories from 1993-1994 the level of morbidity there exceeds national baseline (Fig. 2.5-12).

 

 

Fig. 2.5-12. Trend to prevalence and primary morbidity among adults living in

radiocontaminated territories and adults of Ukraine within period between

1988 and 1997.

 

 

Sex-age features for morbidity were found. Morbidity rate for women is higher compared with men, particularly it relates to diseases of the endocrine system, circulatory system and musculoskeletal system. Morbidity rate increases with age. The most pronounced average annual growth rate from 1988-1997 ocurred in adolescents (80.5% men and 87.4% women), the less growth rate was registered in young adults of 18-29 years of age (22.0-23.0%).

Disability rate among adults residing in affected territories exceeds the national level characteristic of the adult population of Ukraine (10.8-20.5% against 3.7-5.0%). Disability rate among men is higher than among women (Fig. 2.5-13). Growth of disability rates is registered in all age groups, the more pronounced growth is in the groups of 30-39 and 40-49 years of age (more than 4-6 times). Disability is caused by diseases of the circulation, nervous, musculoskeletal, respiratory, digestive systems. In recent years contribution of cancer and endocrine diseases to the structure of disability causes increases.

 

Fig. 2.5-13. Temporal variations of disability in adults of radiocontaminated territories from 1988 to 1999 (data of the National Registry of Ukraine).

 

 

Temporal variations of mortality among adult population residing in radiocontaminated territories show significant annual fluctuations of rates, in some years rates exceed the national level in Ukraine (7.8-22.2% against 11.7-17.3%). At the same time calculation of time trends for 10-year period following the Chernobyl accident shows that growth rate of mortality of the population of Ukraine is higher than that of residents of the affected territories. Mortality rate in the population of the affected territories standardized by age is less than that characteristic of the population of Ukraine (Fig. 2.5-14). From the analysis of temporal variations of mortality for the period from 1988 to 1996 it follows that mortality rate grows in age groups of 15-17, 40-49, 50-59 years. Diseases of circulation, neoplasms, traumas and poisoning are main cause of death.

 

 

Fig. 2.5-14. Rates of general mortality among adults of radiocontaminated territories
and adults of
Ukraine from 1988 to 1996, standardized by age.

 

Malignant neoplasms incidence

Study of incidence rate of malignant neoplasms among three groups of affected people (liquidators, evacuees, residents of territories contaminated with radionuclides) allowed one to detect significant increase in thyroid cancer incidence, particularly among evacuees. The incidence in this group was 5.8 times higher compared with the population of Ukraine. Thyroid cancer incidence among liquidators differed from that among the population of Ukraine (5.5 times). Actual level of the incidence among the residents of the affected territories was 1.7 times higher than the expected level.

Attention should be paid to leukemia, which was developed by liquidators more frequently than by the population. Excess of leukamia incidence was observed in evacuees within the period between 1990 and 1994. Leukemia incidence rate in residents does not differ from the expected level.

 

References

 

 

1.     V.Poyarkov, V.Bar'yahtar, V.Kholosha, N.Steinberg, V.Kukhar', V.Shestopalov, I.Los', The Chernobyl Accident. Comprehensive Risk Assessment.; English edited by G.Vargo; Battelle Press, Columbus, Richland, USA, ISBN 1-57477-082-9

2.     V.Poiarkov, D.Robeau, Laccident de Tchernobyl, in book : Catastrophes et Accidents Nucleaires Dans Lex-Union Sovietique, EDP Sciences, 2001

3.     Proceeding of International Conference "Fifteen Years after the Chornobyl Accident. Lessons Learned", ISBN 966 7600-01-7, Kyiv, 2001

4.     Present and future environmental impact of the Chernobyl accident, IAEA-IPSN Study, 1AEA-TECDOC-1240, IAEA, Vienna, 2001.

 

5.     F. Bréchignac, L. Moberg, M. Suomela, Long-term environmental behaviour of radionuclides, CEC-IPSN Association final report, 2000.

 

6.     V.A. Shevchenko et al, Reconstruction of radiation doses in population and radiation workers applying cytogenetic techniques. Proceedings of the International Conference on Radioactivity of Nuclear Blasts and Accidents. Moscow, 24-26 April 2000.

 

7.     The Human Consequences of the Chernobyl Nuclear Accident A Strategy for Recovery. A Report Commissioned by UNDP and UNICEF with the support of UN-OCHA and WHO, 25 January 2002.

 

8.     French-German Initiative for Chernobyl, Project 2, Radiological Consequences, 2004

 

9.     V.Ivanov, A.Gorski, A.Tsyb Post Chernobyl leukemia and thyroid cancer. Voprosy onkologii( in Russian) 49(4)445, 2003