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Ukrainian Wildfires May Bring Chernobyl’s Radiation Back to Life via New Scientist

The legacy of the world’s worst nuclear accident lives on—and it might be causing new problems, according to researchers from the Norwegian Institute for Air Research.

The 1986 nuclear plant explosion saw the 4800 square kilometres of land surrounding it evacuated and abandoned. The exclusion zone has been taken over by a dense boreal forest over the following decades—and now wildfires are spreading the radiation from the incident further than we’d hope.

The original disaster saw 85 petabecquerels of radioactive caesium released, and best estimates predict that between 2 and 8 petabecquerels still lie in the upper surface of soil around Chernobyl. It was hoped that it would gradually sink into the earth, but the thick, abandoned forest picks that up the radiation, dead leaves return it to the top surface of the soil, and so the cycle continues. Now, forest fires—more severe because of thick vegetation present—can release larger amounts of radiation to the surrounding than expected.

[…]

“The simulation probably underestimates the potential risks,” says Ian Fairlie, former head of the UK government’s radiation risk committee, who has studied the health impacts of Chernobyl. That’s because the estimate depends on the half-life the team assumed for Cs-137, he says, and some investigators believe it is longer.

The team’s calculated release would have given people in the nearby Ukrainian capital, Kiev, an average dose of 10 microsieverts of radiation – 1 per cent of the permitted yearly dose. “This is very small,” says Tim Mousseau of the University of South Carolina at Columbia , a co-author of the study. “But these fires serve as a warning of where these contaminants can go. Should there be a larger fire, quite a bit more could end up on populated areas.”

And the average dose isn’t the problem. Some people will get much more, as fires dump radioactive strontium, plutonium and americium as well as caesium unevenly, and as some foods concentrate these heavy metals, for example caesium in mushrooms. “The internal dose from ingestion can be significant,” says Mousseau. The resulting cancers might be hard to spot among many other less-exposed people. “But they will be very significant for those who experience them.”

Increased forest fires seem likely. The area is due to get drier, according to the Intergovernmental Panel on Climate Change. The team found that droughts are already worsening forest fires in both area and intensity, and those are predicted to worsen.

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This is clearly an important problem and one that applies also to Fukushima, where a significant amount of forest land has been contaminated,” says Keith Baverstock of the University of Eastern Finland in Kuopio, formerly head of radiation protection at the World Health Organization’s European office. “They have a very valid point. The lack of management of forests, the apparently slower decay of vegetation exposed to radiation, climate change leading to drought and the expansion of forested areas all contribute to increasing the risk of forest fire and therefore further dispersal of long-lived radioactive nuclides.”

The actual amount of radioactivity redistributed by the recent fires is about a tenth of what was deposited on Europe in 1986, and its health effects are still a matter of debate among epidemiologists. But long-lived emitters of radioactivity persist and accumulate, so any dose is bad news, says Mousseau. “A growing body of information supports the idea that there is no threshold below which they have no effect.”.

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