Chernobyl nuclear power plant accident

On 26 April 1986, a nuclear power plant accident occurred in Chernobyl, present Ukraine. Radioactive materials spread into many countries over many days. The accident contaminated large areas in Ukraine, Belarus and Russia.

The accident in the Chernobyl nuclear power plant caused direct health effects for a couple of hundred people. Millions of people are affected by the late effects of the accident.

Some of the employees working at the Chernobyl plant on the night of the accident suffered severe radiation injuries. Three people were killed in the plant area on the night of the accident. One of them died of burns, one was buried under falling structures and one suffered a heart attack. In the morning following the accident, 203 people were taken to hospital, suspected of having radiation sickness. Later on, 134 radiation sickness diagnoses were confirmed. In the following weeks, 28 of them died. Of the 106 surviving people, 19 died by 2006. Four of them died of a malignant bone marrow disease, probably caused by exposure to radiation. No one in the population exposed to the fallout is known to have suffered from radiation sickness or radiation burns.

More than 100,000 people were evacuated from nearby areas

Pripyat, the city located closest to the Chernobyl nuclear power plant with a population of 49,000, was evacuated within two days of the accident. An exclusion area was formed around the power plant and it was evacuated of people in the first week of May. Altogether 50,000 people were evacuated from this area reaching 30 kilometres from the site of the accident. In the following months, another 17,000 people were evacuated from the most contaminated villages outside the exclusion area. Altogether, 116,000 people were evacuated in 1986. In later years, tens of thousands of people were moved from villages in Belarus, Ukraine and Russia.

Thyroid cancer increased in the 1990s

People who were near the accident site got significant thyroid doses due to releases of radioactive iodine. Part of the thyroid dose was caused by iodine in the breathing air on the first days and part by iodine obtained later on via foodstuffs, especially milk. The iodine accumulates in the thyroid gland. Therefore, radiation dose to the thyroid gland of the people exposed to radioactive iodine is several times higher than the doses to  other organs.

Since 1990, there has been a strong increase in thyroid cancer in children and adolescents in the contaminated areas of Belarus, Ukraine and Russia. Of those exposed in childhood, more than 5,000 have developed thyroid cancer between 1991 and 2005. A significant number of these cases is undoubtedly due to radioactive iodine exposure. More than a thousand children have developed thyroid cancer while under 15 years of age. It is certain that almost all of these cancers were induced by radiation. They could have been avoided if the children had promptly received iodine tablets and the use of contaminated milk had been prohibited at the very beginning.

Children under five years of age at the time of exposure are at the highest risk of developing cancer. In older children and adolescents the risk is lower. Exposure in adult age has not been demonstrated to be clearly associated with thyroid cancer. The mortality rate for thyroid cancer has been very low (about 1%), but the patients will need hormonal medication for the rest of their life.

No other impacts of radiation were detected

Many reports have been published on the increase of various diseases as a result of the Chernobyl accident. In addition to thyroid cancer, no certain connection has been demonstrated between other health effects and radiation. For example, there were no changes in the number of children’s leukaemia cases in the ten years following the accident. No connection has been demonstrated between exposure to radiation and problems in pregnancy. No radiation exposure-related increase has been detected in malformations or other development disorders, chromosomal anomalies, such as Down syndrome, or the number of stillborn babies.

The accident caused many social, financial and psychological problems, both to the evacuated people and to those who continued living in the contaminated areas. Evacuations led to new problems, with people losing their familiar environment and social structures. The situation was further complicated by the financial and social changes experienced when the Soviet Union fell apart. The distress of parents certainly also affected children. All these factors have an effect on the population’s general health. These problems are discussed in more detail in the UN report published in 2002.

However, what has affected morbidity rates the most is the fact that the health of people living in and evacuated from the contaminated areas has been checked on a regular basis, and all abnormal findings have been included in statistics. Figures obtained in this way are not comparable with figures obtained from population that seek treatment on their own initiative.

Possible cancer cases are difficult to detect statistically

The population groups with the highest exposure are people who participated in the decontamination work in 1986–1987, those evacuated from nearby areas and those staying on in the contaminated areas; 600,000 people altogether. An international group of experts has estimated that cancer mortality may increase among them by a few per cent due to the exposure, which would mean approximately four thousand extra cancer deaths in the decades to come. The number of expected cancer deaths due to all other causes totals more than 100,000. In other population groups the radiation doses are low and it is very difficult to predict the number of cancer cases.

A minor increase in cancer morbidity rates is difficult to detect statistically. So far, in addition to thyroid cancer, no clear correlation has been demonstrated between the population’s radiation exposure and cancer morbidity.

In 2005, eight international organizations, under the name The Chernobyl Forum, published their joint opinion on the effects of the Chernobyl accident on health, the environment and society (pdf).

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  • Muikku Maarit
    Head of Laboratory / KET tel. +358975988509
  • Salminen Eeva
    Research Professor / RAT tel. +358975988752