Air radiation levels have fallen to around the national average in about 70% of Fukushima Prefecture, the Secretariat of the Nuclear Regulation Authority said Wednesday.
As of last December, air radiation levels in these Fukushima areas were 0.1 microsievert per hour or lower. Meanwhile, levels of 0.2 ¦ÌSv per hour or lower were recorded in 92% of the prefecture.
The data was released to mark 15 years since the March 2011 accident at Tokyo Electric Power Company Holdings¡¯ tsunami-stricken Fukushima No. 1 nuclear power plant.
In Fukushima, areas with radiation levels exceeding 3.8 ¦ÌSv per hour ¡ª the threshold for an evacuation order ¡ª totaled 608 square kilometers in 2011 but had shrunk to 7.4 square kilometers in 2025.
Air radiation levels tend to decline over time, according to the Nuclear Regulation Authority (NRA) secretariat.
Decreases have been notable at building lots and agricultural sites, but moderate in forests, where decontamination is difficult.
By 2041, the proportion of Fukushima areas with air radiation levels at 0.1 ¦ÌSv or lower is projected to increase to around 80%, and those with levels at 0.2 ¦ÌSv or lower is forecast to rise to around 95%.
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