The IAEA (International Atomic Energy Agency) has conducted four reviews of planned and executed measures geared to the decommissioning of Fukushima Daiichi Nuclear Power Station and it compiled its final report in November 2018. In this, it stated the following: "The IAEA Mission recognizes that important progress has been achieved in ensuring the transition of Fukushima Daiichi Nuclear Power Station from an emergency to a stable condition."
Moreover, the WHO (World Health Organization) has issued the following assessment: "There is little possibility that radiation from the accident will cause higher incidence of diseases."
Also, UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) has made the following assessment: "Lifetime exposure doses for Japanese people due to the accident are small, and there is little possibility of health impacts arising due to radiation from now on."
IAEA: Preliminary Summary Report IAEA INTERNATIONAL PEER REVIEW MISSION ON MID-AND-LONG-TERM ROADMAP TOWARDS THE DECOMMISSIONING OF TEPCO'S FUKUSHIMA DAIICHI NUCLEAR POWER STATION UNITS 1-4 (Fourth Mission)
WHO: Preliminary dose estimation from the nuclear accident after the 2011 Great East Japan Earthquake and Tsunami (2012)
UNSCEAR: 2013 Report
Ministry of the Environment Government of Japan: BOOKLET to Provide Basic Information Regarding Health Effects of Radiation WHO Reports and UNSCEAR 2013 Reports
Publication of UNSCEAR 2020 Report, Annex B (Advance copy)