Health consequences of the Chernobyl accident in the former Soviet Union

Rescue forces and liquidators

In the years 1986 and 1987, more than 240,000 individuals were deployed as rescue forces and clean-up workers (so-called liquidators) within the 30-kilometre exclusion zone. Further clean-up work was done until about 1990. The total number of liquidators registered for clean-up operations was approximately 600,000.

Evacuated population

In 1986, about 116,000 inhabitants were evacuated from the immediate vicinity of the damaged reactor. In the years after that, around 220,000 additional individuals followed. In 2006, some 5 million people still lived in the areas considered contaminated. For an estimated 100,000 of them, the additional effective dose due to the consequences of the accident is still more than 1 millisievert per year.

Report of the Chernobyl Forum

The Chernobyl Forum was a working group made up of several UN organisations and the governments of Russia, Belarus and Ukraine promoting the progress of the scientific evaluation of the consequences of the reactor accident for humans and the environment from 2003 to 2005. In addition to reports of the individual expert groups, the work within the Forum also resulted in a final report summarising the results of scientific investigations and giving recommendations for further research.

Acute radiation damage

Liquidators

According to the Report of the Chernobyl Forum from 2005, 134 plant workers and firefighters suffered acute radiation syndrome.

In the years following the accident (until 2004), 47 liquidators died:

• 28 individuals died within a few days or weeks after the accident. 13 individuals with acute radiation syndrome received a bone marrow transplant. Only two of the patients treated survived.
• Another 19 individuals died over the subsequent years (1987 - 2004). The causes of death, however, cannot be clearly attributed to the radiation exposure after the accident.

In addition, some individuals received high skin doses of up to 500 grays due to beta radiation. The doses caused severe burns and additionally made medical treatment more difficult.

Two individuals died immediately due to severe injuries and burns resulting from the explosion of the reactor.

Population

According to available reports, no acute radiation damage was observed in the population.

Delayed damage

Thyroid cancer

The number of thyroid cancer cases in the populations of Belarus, Ukraine and the four most affected regions of Russia increased significantly after 1986. From 1991 to 2005, about 6,900 thyroid cancer cases were diagnosed in individuals who were children or adolescents under 18 years of age at the time of the accident. This sharp increase in cancer cases is mainly attributed to the exposure to radioactive iodine within the first months after the accident. Radioactive iodine was mostly taken in through the consumption of cow's milk and through inhalation with air. After being taken up by the body, it accumulates in the thyroid. The thyroid doses of the evacuated population ranged from 0.05 gray to more than 5 grays.

Other tumours

To date, there is no reliable scientific evidence for tumours in other organs. There are studies on breast cancer in women in Ukraine and Russia indicating increased incidence rates but which are only of limited power because they do not consider other influencing factors besides radiation or do not determine any difference concerning the cancer rates in areas with different levels of radiation exposure.

Leukaemia

There are indications for an increased leukaemia incidence among the liquidators. The studies providing these indications, however, have weaknesses relating to their statistical power, dose estimation and possible confounding because of insufficient consideration of influencing factors.

Cardiovascular diseases and cataracts

A study determined an increase in cardiovascular diseases and resulting deaths for liquidators who had received radiation exposures of more than 150 milligrays. However, apart from ionising radiation, this study does not consider other influencing factors such as overweight, smoking or alcohol consumption. Furthermore, an association between the level of exposure and the risk of cataract (clouding of the eye lens) has been observed in the liquidators.

Other consequences

The most affected individuals among the population increasingly showed stress symptoms, depression, general anxiety states and physical disease symptoms which cannot be explained medically. These diseases are to be seen as indirect consequences of the reactor accident, but not as direct consequences of the radiation exposure. Insufficient information about the occurrences in and around Chernobyl, the way communication took place after the accident, the disintegration of the Soviet Union as well as the general deterioration of the social and economic situation may also have contributed to the psychological burden.