Health consequences of the Chornobyl accident in the former Soviet Union

Flowers at the monument to the Chornobyl firefighters

Numerous publications have investigated the health consequences of the Chernobyl reactor disaster. Key summaries of these findings are provided by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and the Chernobyl Forum, a working group of the International Atomic Energy Agency (IAEA), the World Health Organisation (WHO), several UN organisations, and the governments of Russia, Belarus, and Ukraine, which conducted investigations into the health and environmental impacts of the disaster from 2003 to 2005. The following groups are often distinguished during the investigation:

Emergency responders and liquidators

On 26 April 1986, around 600 emergency workers (e.g. plant personnel, fire-fighters, and emergency services) were present at the power plant. In 1986 and 1987, more than 240,000 people were employed as cleaning workers (liquidators) within a radius of 30 km around the power station. Further clean-up operations continued until about 1990. Approximately 600,000 liquidators were registered.

Population

In 1986, about 116,000 residents were evacuated from the immediate vicinity of the reactor (within a 30 km radius and areas with gamma dose rates above 0.2 millisieverts per hour). In the subsequent years, another 220,000 people were evacuated.

In 2006, about six million people still lived in the "contaminated areas". The areas of the former Soviet Union that had cesium-137 concentrations of more than 37,000 becquerels per square meter on the ground are considered to be "contaminated". The 98 million people living in Ukraine, Belarus, and the 19 affected oblasts (administrative districts) in Russia were also examined during the health investigation. The Russian oblasts with contaminated areas are considered "affected".

Acute radiation damage

Two plant employees died immediately from injuries caused by the reactor explosion.

A further 134 emergency responders suffered acute radiation syndrome. Of these, 28 died within four months of the disaster. Their deaths were caused by high radiation doses. Another 19 individuals with acute radiation syndrome died between 1987 and 2004. Their deaths may also be linked to the radiationdoses received following the disaster. For survivors of acute radiation syndrome, skin injuries and radiation-induced cataracts (clouding of the eye lens) were the most serious health effects.

The 134 individuals with acute radiation syndrome received whole-body doses of 0.8–16 Grays of external gamma radiation. Some also received skin doses of 400–500 Grays through beta radiation, which resulted in severe burns. Most of the deceased died from infections caused by the burns. Thirteen people with acute radiation syndrome were treated with a bone marrow transplant. Only one of those treated survived.

Reports indicate that no acute radiation damage was observed in liquidators or the general population.

Health consequences that occur later

As a result of the reactor disaster, liquidators and nearby residents received increased radiation doses, which may have caused – or may still cause – later radiation damage. Radiation doses varied considerably:

Liquidators

• received an average additional effective dose of 120 millisieverts from clean-up work between 1986 and 1990.
• Dose values ranged from less than 10 to more than 1,000 millisieverts.
• For 85% of them, doses ranged from 20 to 500 millisieverts.

Evacuated individuals

• received an average additional effective dose of 33 millisieverts.

Six million individuals in contaminated areas

• received an average effective dose of 9 millisieverts between 1986 and 2005.
• For 70% of these individuals, the additional effective dose was below 1 millisievert.
• For 20%, it ranged between 1 and 2 millisieverts.
• For 2.5%, it exceeded 50 millisieverts.

Ninety-eight million people in Ukraine and Belarus as well as the 19 affected oblasts in Russia

• received a comparatively low additional effective dose of 1.3 millisieverts between 1986 and 2005.

For comparison, background radiation in Ukraine, Belarus, and the 19 affected oblasts in Russia was estimated at 50 millisieverts over the same period. The additional effective doses determined thus represent a considerable increase compared with the background radiation.

The exact number of people who fell ill or died because of increased radiation doses from the reactor disaster remains uncertain. In 2005, the Chernobyl Forum estimated that about 4,000 deaths were caused by the additional doses of radiation.