The Chernobyl nuclear accident in 1986 will lead to far fewer deaths than originally thought, according to a report from the United Nations.

Some 4,000 people — including emergency workers and residents of the most contaminated areas — could eventually die of factors linked to radiation exposure, the report says. Earlier estimates had ranged widely but regularly suggested that there could be many tens of thousands of deaths (see Nature 351, 4; 199110.1038/351004b0).

“The effects on public health were not nearly as substantial as had at first been feared,” says Michael Repacholi, head of the radiation programme at the World Health Organization in Geneva.

Repacholi was among more than 100 scientists, economists and health experts who worked on the 600-page document, which aimed to summarize the available scientific data on the accident and the countries most affected by it: the Ukraine, Belarus and Russia. The report was due to be released by the Chernobyl Forum at a meeting in Vienna this week.

On 26 April 1986, one of four reactors at the Chernobyl nuclear power plant in the Ukraine suffered a series of explosions and a meltdown — the worst nuclear accident in history. Radioactive fallout contaminated more than 200,000 square kilometres of Europe, leading to the eventual relocation of more than 350,000 people.

So far, the report says, fewer than 50 deaths have been directly attributed to radiation exposure — most of them rescue workers who died of acute radiation syndrome shortly after the disaster. The authors estimate that the incidence of radiation-induced cancer rose by only about 3% in the affected areas.

They add that the thousands of children who contracted thyroid cancer after the accident are likely to have a 99% survival rate, higher than the 80–85% previously thought.

Poverty and mental-health problems, such as stress, depression and anxiety, pose a much greater threat to the local communities than radiation, the report concludes. It argues that future aid should focus on improving the healthcare system and promoting local economic development.