More than 53,000 Fukushima-1 workers received over 5 millisieverts in a year
More than 53,000 workers at Japan’s accident-hit Fukushima-1 nuclear power plant received annual radiation doses exceeding 5 millisieverts over 15 years. In Japan, this level is the threshold for determining the eligibility of nuclear plant workers who develop leukemia for compensation related to a work injury or illness, The Japan Times reports.
Data over 15 years
As of the end of March 2026, the cumulative number of workers who received more than 5 millisieverts during a given year reached 53,145. The data are based on an analysis of annual radiation monitoring reports by Tokyo Electric Power Company Holdings, submitted to Japan’s Nuclear Regulation Authority after the accident at the plant in March 2011.
In fiscal 2010, 403 workers received doses exceeding 50 millisieverts; in 2011, 205 did; and in 2012, one did. No such cases have been recorded since fiscal 2013.
The average radiation dose per worker declined from 21.6 millisieverts in fiscal 2010 to 4.3 millisieverts in 2015, 2.6 millisieverts in 2020, and 1.7 millisieverts in 2025.
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Occupational diseases and comparison
As of the end of March, Japan’s Health Ministry had recognized 17 cases of illnesses, including leukemia and solid cancers, as being related to radiation exposure during work connected to the accident. Eight cases involved leukemia; two cases each of throat, thyroid, lung and colon cancer were also recognized.
A cumulative radiation dose criterion of at least 100 millisieverts is used to recognize solid cancer as an occupational disease. At least two of the 17 workers whose illnesses were recognized as related to work at the plant have died.
In fiscal 2025, the total dose received by Fukushima-1 personnel was 20.97 sieverts. The figure was 2.22 sieverts at Takahama nuclear power plant, 0.99 sieverts at Sendai nuclear power plant, 0.80 sieverts at Genkai nuclear power plant, and 0.75 sieverts at Tokai-2 nuclear power plant.
More than 1,500 Fukushima-1 workers received more than 5 millisieverts during the year. By comparison, there were 66 such workers at Takahama nuclear power plant, 18 at Sendai nuclear power plant, and 11 at Tokai-2 nuclear power plant. The plant’s decommissioning is planned to be completed in 2041–2051.
