The International Atomic Energy Agency (IAEA) conducted four reviews of the plans and activities to decommission the Fukushima Daiichi Nuclear Power Station, and compiled the findings in a final report, in November 2018. The IAEA summarized its findings in the report, stating, "The IAEA Review Team considers that significant progress has already been accomplished to move Fukushima Daiichi from an emergency situation to a stabilized situation."
The World Health Organization (WHO) also made assessments, and their findings suggest that the radiation from the accident is unlikely to cause a discernible increase in the future incidence of health issues.
In reports published by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the committee concluded that risks over the lifetimes of the Japanese people were so low that no discernible increase in the future incidence of health effects due to radiation exposure were likely among the population.
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)