Exterior view of the sarcophagus built on the reactor at the Chernobyl nuclear plant. Description:Igor Kostin/Sygma via Getty

Decades after the world’s worst nuclear accident, experts still can’t agree how many people it killed.

Two people died immediately as a result of the blast at the Chernobyl nuclear plant in Ukraine – then part of the Soviet Union – on 26 April 1986. Another 29 died in hospital during the next few days. The longer-term impact of the radiation, however, has proved harder to quantify.

Two decades ago, John Gittus of the Royal Academy of Engineering told the UK government there could eventually be around 10,000 fatalities. Today, some – notably environmental groups – put the death toll well into six figures.


But that’s the extreme end of the estimates. “The only deaths that have been firmly established, either individually or statistically, are the 28 victims of acute radiation syndrome and 15 cases of fatal child thyroid cancer,” says Wade Allison of the University of Oxford.

2065 toll

The mainstream view puts the toll in five figures. Environmental physicist Jim Smith of the University of Portsmouth, UK, prefers to cite a 2006 study by Elisabeth Cardis of the International Agency for Research on Cancer in Lyon, France. This predicted that by 2065 Chernobyl will have caused about 16,000 cases of thyroid cancer and 25,000 cases of other cancers, compared with several hundred million cancer cases from other causes.

Agreement is unlikely any time soon. “Confusion has arisen over the populations considered in the various calculations – former Soviet Union, Europe or the world,” says Richard Wakeford of the Dalton Nuclear Institute at the University of Manchester, UK.

The UN Scientific Committee on the Effects of Atomic Radiation has also examined this critical question but has not commented on the death toll. “I had expected them to do more about this,” says Wakeford. “There is still a surprising amount of uncertainty.”