By late 1986, however, Soviet officials revised this official tally upwards from two to a final toll of 31, reflecting the deaths of 29 additional plant workers and first responders in the months after the accident. In the decades since the accident, many former Soviet officials and some Western sources have stood by 31 as the accident's official death toll, making 31 the most oft-cited figure for the disaster's direct, short-term fatalities.
In 2006, responding to persistent allegations that the official figure of 31 direct deaths during and immediately following the disaster omits other confirmed trauma and ARS deaths from the same period, the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) revisited the issue. Citing additional deaths from trauma or ARS directly attributable to the disaster during 1986 and 1987—including those of a physician and a journalist who arrived at the plant shortly after the reactor explosion and a helicopter crew of Chernobyl liquidators who died in an aerial attempt to pour a decontaminating acetate mixture on a liquidator work area in October 1986—UNSCEAR revised the accident's immediate death toll to 54, acknowledging in the process that some groups assessing the same data place the number as low as 49 or as high as 59. Several United Nations agencies have since adopted UNSCEAR's 54 figure as the official tally of short-term deaths directly attributable to the Chernobyl disaster.
For their part, some surviving evacuees of regions now included in the Chernobyl Exclusion Zone and the Polesie State Radioecological Reserve argue that the official toll of the accident's direct casualties excludes trauma and ARS deaths that they themselves claim to have witnessed in the weeks and months after the reactor explosion. In response, constituent agencies of the United Nations—including the United Nations' International Atomic Energy Agency (IAEA) and the Chernobyl Forum—discount such evacuee claims as misinformation, 'urban legend,' or Radiophobia.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) produced a detailed report on the effects of Chernobyl for the General Assembly of the UN in 2011. This report concluded that 134 staff and emergency workers suffered acute radiation syndrome and of those 28 died of radiation exposure within three months. Many of the survivors suffered skin conditions and radiation induced cataracts, and 19 had since died, but from conditions not necessarily associated with radiation exposure. Of the several hundred thousand liquidators, apart from some emerging indications of increased leukaemia, there was no other evidence of health effects.
In the general public in the affected areas, the only effect with 'persuasive evidence' was a substantial fraction of the 6,000 cases of thyroid cancer in adolescents of whom by 2005 15 cases had proved fatal. There was no evidence of increased rates of solid cancers or leukaemia among the general population. However, there was a widespread psychological worry about the effects of radiation.
The total deaths reliably attributable by UNSCEAR to the radiation produced by the accident therefore was 62.