Rotblat was appalled by the use of the atomic bomb on Hiroshima (of which he heard on the radio) and subsequently on Nagasaki. Partly in reaction to the horrors of the atomic bomb, he became more interested in the medical uses of nuclear radiation.

Martin Underwood, Joseph Rotblat: a man of conscience in the nuclear age, Brighton [England] ; Portland, Or, 2009, p. 35