Consequences
of the accident on public health
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
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·ì-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
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
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
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 people’s 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.
Table
2.5-1. Main groups of people
affected by the
|
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
|
Radiation |
Non-radiation |
|
Internal
and external radiation: Dose-forming
radionuclides of iodine, |
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
Table 2.5-3. Distribution of
collective thyroid doses in residents of oblasts of the
Oblast
|
Collective thyroid dose, 103 person-Gy |
|||
|
0-6
years |
7-17
years |
>17 years
|
Total |
|
|
|
35.0 |
19.2 |
46.5 |
100.7 |
|
|
0.5 |
0.3 |
0.9 |
1.7 |
|
|
96.6 |
53.7 |
151.0 |
301.3 |
|
|
16.4 |
9.0 |
24.0 |
49.4 |
|
|
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
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
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
Average annual
indicators of leukaemia incidence among children of
six oblasts of
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
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
Fig. 2.5-2. Rate of some congenital
defects of development in the population
of
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.
·
adequate model for prognosis
at the range of low radiation doses which are characteristic of the
·
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
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
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
|
Year of arrival at the |
Cancer diseases |
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
Let
us consider results of prognostic estimates of radiation-induced cancer among
residents of contaminated with radionuclides
territories of
Let us consider leukaemia incidence among
liquidators. Researchers of
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
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
When prediction of delayed radiation effects on the population was made
we had expected unfavorable situation concerning thyroid cancer particularly
thyroid cancer in