I saw a #YT video where a guy took a radiation meter all over Hiroshima -- even to structures that predated the atomic bombing -- to see if there was any residual radiation. He found nothing over background, even standing directly at ground zero of the air burst (there's a plaque at that location). The remains of the famous "atomic bomb dome" actually read a bit below background elsewhere. As he moved out into the surrounding area outside of central Hiroshima itself (e.g. more suburban) the background count got noticeably higher, but still considered to be effectively "normal". One assumes that cleanup efforts were concentrated on the more central areas, for obvious reasons.