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People were exposed to radiation from the Chernobyl accident through two routes:
Human exposure to ionizing radiation such as alpha, beta, gamma and other kinds of radiation, can be expressed as
For gamma radiation, for instance, 1 Gy of absorbed dose is equal to 1 Sv of effective dose. More...
If the human body absorbs a dose of a few of grays external radiation, it may cause acute radiation syndrome (ARS). Workers who were near the reactor at the time of the accident and shortly afterwards received high doses from external gamma radiation (2 - 20 Gy), which were fatal to some of them.
The effective dose to which humans across the world are exposed as a result of natural background radiation typically ranges from 1 to 10 mSv per year. In addition humans may be exposed to radiation from man-made sources and the recommended dose limit for the general public is 1 mSv per year.
With the exception of the on-site reactor personnel and the emergency workers who were present near the destroyed reactor during the time of the accident and shortly afterwards, most recovery operation workers and people living in the contaminated territories received relatively low whole-body radiation doses, comparable to background radiation levels.
Evacuees from the Chernobyl accident were exposed to average doses of 33 mSv, and individual doses sometimes reached several hundred mSv. The majority of the five million people living in contaminated areas of Belarus, Russia and Ukraine currently receive an annual dose below the recommended limit for the general public. However, about 100 000 residents of the more contaminated areas are still exposed to doses higher than 1 mSv per year.
Through food containing radioactive iodine, some people received high internal doses of radiation, particularly in the thyroid gland. Indeed, the average effective dose of radiation observed in the thyroid of people living in contaminated areas ranged from 0.03 to 0.3 and reached up to 50 Gy in some individuals.
Children who had consumed milk from cows that had eate contaminated grass were particularly affected, and many of them went on to develop thyroid cancer. Some people, such as those living in Pripyat, very near the Chernobyl power plant, were given stable iodine tablets which substantially reduced the amount of radioactive iodine accumulated by their thyroid glands. More...
Table: Average accumulated doses among liquidators, evacuees and local residents
The number of deaths attributable to the Chernobyl accident has been of great interest to the public. Confusion about the impact of the accident has given rise to highly exaggerated claims that tens or even hundreds of thousands of persons have died as a result of the accident. In fact, since the accident, many emergency and recovery operation workers as well as people who lived in ‘contaminated’ territories have died of diverse natural causes that are not attributable to radiation.
In 1986, 134 emergency workers who received high doses of radiation were diagnosed with acute radiation syndrome (ARS) and 28 of them died from it during the first months after the accident. However, the general population exposed to the Chernobyl fallout did not suffer from ARS, as the radiation doses received were relatively low.
Regarding possible deaths from cancer, an international expert group predicts that among the 600 000 persons receiving more significant exposures (liquidators working in 1986–1987, evacuees, and residents of the most ‘ contaminated’ areas), the possible increase in cancer mortality due to this radiation exposure might be up to a few per cent, which might eventually represent up to four thousand fatal cancers. This estimate was made for public health planning purpose and mostly reflects the order of magnitude rather than a definite number.
Among the general population living in other ‘contaminated’ areas, the doses received were much lower and any increases in cancer mortality are expected to be much less than one per cent. Between 1992 and 2002, among those who were children or adolescents at the time of the accident, 15 people died from thyroid cancer.
It is difficult to tell precisely how many deaths have been caused by the Chernobyl accident in the past 20 years as people who were exposed to additional low levels of radiation from the accident have been dying from the same causes as unexposed people. It is even harder to predict the possible number of future deaths. Therefore the exact death toll of the accident is likely to remain unknown. More...
2.3.1 The thyroid gland naturally accumulates iodine from the blood stream, as a normal functioning mechanism, and is the organ most likely to develop cancer after exposure to iodine-131. Because large amounts of radioactive iodine were released as a result of the Chernobyl accident, the thyroid glands of local residents received considerable doses through breathing and through consuming contaminated foods, especially milk. Children are particularly vulnerable and there has been a substantial increase in thyroid cancer among people who were exposed as children.
More than 4000 cases of thyroid cancer were diagnosed in Belarus, Russia and Ukraine between 1992 and 2002 among those who were children and adolescents at the time of the accident. Most of these cancers can be attributed to radiation. The majority of those patients have been treated successfully. New cases are expected to be diagnosed for many more years. It should be noted that early mitigation measures (distribution of iodine tablets and evacuation) helped substantially to minimize the health consequences of the accident. More...
2.3.2 Ionizing radiation is an established cause of certain types of cancer , namely leukaemia (except Chronic Lymphocytic Leukaemia or CLL) and solid cancers. It may also increase the risk of cardiovascular diseases in population groups exposed to higher doses such as atomic bomb survivors or radiotherapy patients.
Between 1986 and 1996, the number of cases of non-CLL leukaemia doubled among Russian workers who had been exposed to external doses higher than 150 mGy. However, the risk of radiation-induced leukemia is likely to decrease in the future, because it usually takes up to 10 years from the moment of exposure to develop radiation-induced leukemia.
Russian emergency and recovery operation workers also seem to have more solid cancers and possibly more cardiovascular diseases than the general population. However, the higher levels of cardiovascular diseases could also be caused by other factors such as stress and unhealthy lifestyles. Nonetheless, highly-exposed Chernobyl workers should continue to receive medical care and annual examinations.
In contrast, in the general population of the contaminated regions, there has been, so far, no convincing evidence that Chernobyl has had any effect on the leukaemia or solid cancers risk, except for childhood thyroid cancer.
An absence of evidence of increased cancer risk does not mean that this increase has not occurred. An increase like this would be very difficult to detect without large scale epidemiological studies, and that given the large number of people exposed, small variations in statistical projections can greatly affect the number of expected cancer cases. More...
2.3.3 People who have been exposed to radiation doses higher than 0.25 Gy may develop cataracts. Continued follow-up studies of the Chernobyl populations will allow scientists to predict more accurately the risk of developing radiation-induced cataracts and any resulting vision problems. More...
There is no convincing evidence of any direct effects on fertility of exposure to radiation among the general population of Chernobyl-affected regions.
Because most people received relatively low doses of radiation, it is unlikely that any effects will be seen in future. Birth rates may be lower in contaminated areas because of concern about having children, the very high number of medical abortions, and the fact that many younger people have moved away.
The doses received are also unlikely to have any effect on the number of stillbirths, miscarriages, delivery complications, or the overall health of children of exposed parents. Since 1986, the number of reported cases of malformations in new-born babies in Belarus has increased in both contaminated and uncontaminated areas. This does not appear to be related to radiation and may be the result of people reporting these cases more readily. More...
The Chernobyl-exposed populations showed many of the symptoms that commonly appear following a traumatic accident or event: stress, depression, anxiety (including post-traumatic stress symptoms), medically unexplained physical symptoms, and subjective poor health.
Many people were traumatized by the rapid relocation and the breakdown in social contacts, and in the absence of reliable information have experienced fear and anxiety about what health effects might result.
In addition, individuals in the affected population have come to be known as "Chernobyl victims" rather than "survivors", which encouraged them to perceive themselves as helpless, weak and lacking control over their future, thus to take on the role of invalids. More...
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