Transition and current status of air dose rates in Fukushima Prefecture

Air radiation dose rate map based on Fukushima Prefecture's environmental radiation monitoring・mesh survey results

• Radiation dose in the air refers to the quantity (intensity) of radiation in a given space, typically including gamma rays in the atmosphere, from the earth and cosmic rays. Radiation dose rate in the air is the dose measured per unit time in a specific size of space.
• Figure (1) illustrates data taken approximately one month after the disaster. Figure (2) represents data from FY2023. In the Nakadori (Central Region) and Hamadori (Coastal Region) areas, the effects of natural decay of radioactive materials and decontamination are evident. Moreover, the Aizu region has returned to air dose rate levels comparable to those before the nuclear accident.

*Created using the Geospatial Information Authority of Japan's "Digital Elevation Model of Fundamental Geospatial Data" and the Ministry of Land, Infrastructure, Transport and Tourism's "Digital National Land Information (Administrative District Boundaries, Roads)."

Figure (1): Data approximately one month after the earthquake disaster.

April 12-16, 2011

Figure (2): Data from FY2023.

April 10, 2023 to May 9, 2023

About air dose rates

• Compared to the radiation levels immediately after the earthquake, the current levels have significantly decreased due to natural decay and decontamination efforts. They have been reduced to a level comparable to the world's major cities and most of the cities in the country.

Comparison of air dose rate, Fukushima, domestic and internatinal locations

Transition of air dose rate in Fukushima City

• The graph below illustrates the changes in the air dose rate in Fukushima City. Immediately after the earthquake, it measured at 1.91 μ㏜/h, but the dose rate has gradually decreased over the years through natural decay and decontamination efforts. By FY2023, it had reached 0.11 μ㏜/h (approximately 1/17th of the value immediately after the earthquake).

Reference information

• In Fukushima Prefecture, air dose rate measurements and analysis of radioactive materials in the environment (air, water, soil, etc.) are conducted to ensure safety and security. The measurement results are publicly disclosed. Furthermore, Fukushima Prefecture's environmental radiation monitoring newsletter "Fukumoni" is published  to provide updates on the current radiation status in the prefecture. For more information, please visit the following website.

Fukushima Prefecture Radiation Monitoring Unit website[Japanese only]

Fukushima Prefecture's environmental radiation monitoring newsletter "Fukumoni" （March 2023） [PDF／8.99MB]