As the Fukushima nuclear catastrophe unfolded in March 2011, experts began applying lessons (some poorly learned or incomplete) from other nuclear disasters, primarily Chernobyl. After Chernobyl, it took nearly a decade for official experts to admit what data were revealing: exposure to radioiodine, one of the nuclides released from nuclear power disasters, increases thyroid cancer. Those who were children at the time of their exposure were particularly vulnerable. As radioactive clouds blanketed the areas surrounding the melting Fukushima reactors, officials were conflicted about the application of stable potassium iodide (KI) to keep radioiodine from penetrating the thyroids of members of the public.
Shunichi Yamashita, a doctor who had studied thyroid cancers in the Chernobyl-contaminated areas, expected no impact from radioiodine exposure. Reports differ, however, with some saying that Yamashita was publicly claiming no danger, while secretly telling experts he had serious concern about child thyroid cancer. He encouraged those who may have been exposed to protect themselves against radiation by being in a good mood and laughing. FMU had taken the precautionary measure of distributing KI to its staff members and their children. FMU claimed this was to cajole nervous hospital staff into staying during the initial disaster, rather than to protect their health. The staff, however, was sworn to secrecy regarding this decision. Fukushima Prefecture failed to tell FMU to administer KI to the public. FMU waited for Yamashita to inform the issue and he said taking KI was unnecessary, so many in the public were left unprotected. “Yamashita admitted that he had given incorrect information shortly after the disaster when he advised FMU not to dispense potassium iodide tablets to children.” After he had made his decision, he reportedly looked at the fallout maps and said “Oops”