Tomonaga Masao

Masao Tomonaga, born in Nagasaki, Japan, in 1943, is a hibakusha, a survivor of the atomic bombing. At the age of two, he survived the second atomic bomb that struck Nagasaki on August 9, 1945. Growing up in good health, Tomonaga pursued a medical career, specializing in healthcare for atomic bomb–related illnesses, as well as internal medicine and hematology, at Nagasaki University Medical School.

He has devoted his life to studying the effects of radiation exposure in causing leukemia and other cancers. His research led to a study based on 76 years of data, documenting how radiation exposure experienced by hibakusha has lifelong consequences, damaging DNA. Tomonaga served as Emeritus and Honorary Director of the Japanese Red Cross Nagasaki Atomic Bomb Hospital and currently manages a retirement home for elderly hibakusha. He is also President of the Nagasaki Global Citizens Assembly for the Elimination of Nuclear Weapons and in 2024 participated in the Nobel Peace Prize ceremony for Nihon Hidankyo, an association that has campaigned for the abolition of nuclear weapons since 1956.

Masao Tomonaga is the son of Msanobu Tomonaga, a doctor who cared for Takashi Paolo Nagai, the Christian physician of Nagasaki who survived the bomb and died in 1951 in fame of sanctity, and who was close to him at the time of his death.