Changes in Average Dose Rates in Areas where the National Government Directly Conducted Decontamination Work (Residential Areas and Agricultural Land)

This figure shows radiation dose attenuation of accident-derived radioactive materials as estimated based on approx. 340,000 data from the results of the monitoring conducted prior to decontamination work from November 2011 to October 2016 and the results of the monitoring conducted after decontamination work from December 2011 to June 2017.

The blue line on the graph shows radiation dose rates estimated based on the values of August 2011 taking into account only the effects of natural attenuation and weathering (natural factors such as wind and rain). The red line on the graph shows radiation dose rates estimated including the effects of decontamination. Comparing both air dose rates in March 2018 shows that decontamination has reduced the average air dose rate by about 59%. This means that the reduction of radiation dose rates was accelerated by approx. 18 years through decontamination work.

Thus, through further decontamination combined with natural attenuation of radioactive materials and other factors, radiation doses could be reduced at an earlier stage.
(Related to p.11 of Vol. 1, “Half-lives and Radioactive Decay”)

• Included in this reference material on March 31, 2014
• Updated on March 31, 2024