Cancers caused by radiation from the atomic bombs dropped on Hiroshima and Nagasaki 80 years ago have killed or will kill under 1 per cent of those who initially survived the explosions and radiation exposure, according to a comprehensive new study.

About 140,000 people in Hiroshima and 74,000 in Nagasaki are believed to have died by the end of 1945 from the effects of blast, heat and acute radiation poisoning. At an 80th anniversary ceremony in Nagasaki on Saturday, Japanese Prime Minister Shigeru Ishiba said it was essential to pass down memories of the “brutal impact of the harm wrought by the atomic bombings”.

Exposure to high levels of radiation increases cancer risk. However, Philip Thomas, professor of risk management at Bristol university, said his study’s estimate that just 3,100 out of 324,000 survivors of the atomic bombings had died or would die of radiation-induced leukaemia or solid tumours would surprise many.

“This research shows that radiation, while dangerous, is a weaker cause of cancer than many people think,” said Thomas, whose earlier career was spent in the nuclear industry. His results are published in the Journal of Biological Physics and Chemistry.