At 8.15 am on 6 August 1945, an atomic bomb detonated over Hiroshima. Tens of thousands died within the day; by the end of 1945, local governments estimated the toll at roughly 140,000. What followed was not just devastation, but eight decades of medical research built almost entirely on the bodies and lives of those who survived.
That research now underpins how doctors read a CT scan, how nuclear accidents are managed, and how pregnant women are counselled before an X-ray. The Radiation Effects Research Foundation (RERF), successor to the Atomic Bomb Casualty Commission, set up in 1947, has followed more than 100,000 survivors and their children in what remains the longest-running epidemiological study of its kind. On this Hiroshima Day, here are five medical discoveries that trace directly back to that tragedy.
The Blueprint for Every Radiation Safety Limit
Before Hiroshima, no one had reliable human data on how radiation dose related to cancer risk. RERF's Life Span Study changed that, tracking cancer rates against carefully reconstructed individual doses for decades. Richard Wakeford, a radiation epidemiologist at the University of Manchester, has said the work continues to make major contributions to our understanding of radiation effects. That dose-response curve now sits behind the safety limits set for nuclear workers, airline crews, and every patient sent for an X-ray or CT scan.