The Chernobyl and (to a lesser extent) Fukushima nuclear accidents contaminated large areas of land with low-level radioactivity. After both accidents, huge efforts were taken to decontaminate the affected areas. But a recent study at Fukushima raises doubts about whether these decontamination efforts were worthwhile.
Less than one-third of the population has returned to the evacuated zones and extensive areas of forest in the region remain contaminated.
Following the accident at Fukushima Daiichi in 2011, approximately 1,100 square kilometres were evacuated, resulting in the relocation of more than 100,000 people from their homes. A contaminated area about eight times larger remained inhabited, albeit subject to continuous radiation monitoring.
The dominant source of radiation exposure for people stemmed from gamma rays emitted by contaminated soils, pavements, roads and buildings. The objective of the decontamination operation was to ensure that the general public received an annual dose from Fukushima’s radioactivity of less than 1,000 microsieverts (µSv) above the natural background level. The average natural radiation dose in Japan stands at 2,200 µSv per year.
Costs and benefits
Decontaminating the land in Fukushima has cost tens of billions of dollars. The process has, unfortunately, also caused substantial radiation exposure for the workers involved, and has generated huge amounts of radioactive soil waste. But the question of whether to decontaminate land is complex and only partially related to scientific evidence.
Accidental rewilding
In the evacuated zone where dose rates were around ten times higher, it’s less clear that decontamination was beneficial. Only 30% of people have returned to their homes in the decontaminated part of this area and much of the land in the most contaminated so-called “difficult to return zone” remains abandoned. A better option may have been to declare most of this zone a nature reserve and allow managed rewilding of the area. Rewilding is happening to a large extent anyway, as it has at Chernobyl. It would also have avoided decontamination workers being exposed to radiation and allowed more financial support to help people relocate.
Fukushima’s contaminated forests
The land in and around the region’s towns and villages has generally been decontaminated effectively. However, much of the Fukushima Prefecture (71%) is covered by forest. Most of this forest remains contaminated. The persistence of radiocaesium in ecosystems, particularly in forests, has been known for many decades.
