In the early morning of April 26, 1986, an explosion at the Soviet Union's Chernobyl nuclear power plant tore through one of the facility's reactors, blowing off the roof, and allowing a 3000-foot-high plume of radioactive gas to spew into the dark Ukrainian sky.
Nearly three decades later, the area is long devoid of permanent residents. But as much as nine percent of the radioactive cesium released into the air following the explosion remains in the soils and vegetation surrounding the decommissioned plant. Forest fires frequently break out and climate change could mean they become more frequent and more intense.
Those fires could release radioactive material into the atmosphere, which could pose health risks to humans living far beyond the contaminated zone, according to a new study published in the journal Ecological Monographs.
"In places like Chernobyl and now in Fukushima, we need to prepare for the possibility of these catastrophic fires," Tim Mousseau, a biologist at the University of South Carolina, Columbia and co-author on the study, told VICE News. "And we need to invest in proper management of these areas so they don't go up in smoke."
Nearly 1,000 wildfires burned within the evacuated area around Chernobyl between 1993 and 2010, due in part to seasonal droughts and forest die-offs because of pests and disease. Mousseau and a team of researchers used data from three fires in 2002, 2008, and 2010, along with information about how radioactive material spread during the original disaster, to develop a computer model that could predict the impact of a future fire and the distribution of radiation.
The original disaster released radioactive cesium, which the researchers used because it's easy to measure, along with other radioactive elements including strontium and plutonium. Though much of the material has disappeared due to radioactive decay, what remains is dispersed in the soil and water, which is sucked up by growing trees and distributed throughout their leaf systems.
Dead, fallen leaves on the ground are a prime fuel for forest fires. In previous papers, the researchers discovered that leaves contaminated with radiation did not decompose as quickly as uncontaminated leaves, leading to greater buildup of leaf litter on the forest floor.
"The cesium gets brought up in the water as the tree grows and it gets concentrated," Mousseau told VICE News. "And so it's not disappearing nearly as quickly as one would have thought."
'Their simulation probably underestimates the real risk.'
A fire consuming the leaves vaporizes the radioactive material, and its heat causes the vapors to rise into the atmosphere. Once there, the vapors travel on the air until they fall or are brought to the ground with rain.
The study estimates that the amount of radioactive cesium redistributed by fires is about eight percent of the cesium originally released in the disaster.
"That's a big guess," Ian Fairlie, a former UK government consultant on radiation risks, told VICE News. "In their analysis their estimates all depend on that figure of eight percent, and it's not reliable."
The figure is based on an assumption that the particular variety of cesium being studied, cesium-137, has a half-life of 10 years, meaning it takes a decade for its radioactivity to diminish by half. Fairlie points to other research showing cesium's half-life to be longer.
"In other words, their simulation probably underestimates the real risk," Fairlie told VICE News.
And, because of climate change, that risk could be increasing. According to some climate models, average annual temperatures in Chernobyl and the surrounding area will reach about 57 degrees Fahrenheit by the end of the century — about 10 degrees higher than they were in 2000. Climate change may also bring increased rain to the area, which could help control wildfires but could also increase the vegetation that fuels them.
Limited financial resources and attention to firefighting has left Ukraine ill equipped to deal with such potentially hazardous fires, Mousseau said. A 2011 paper, presented at an international wildfire conference, found that Ukrainian government stifled outside attempts at addressing concerns over wildfire radiation, leaving international policymakers and nongovernmental organizations unable "to do [anything] other than sympathize with the issue."
"There have been local forest fires since the accident, and as the authors say, they haven't had a major effect," David Brenner, director of the Center for Radiological Research at Columbia University Medical Center, told VICE News. "But the authors' bottom line, that more resources should be put into local forest fire prevention, detection, and fighting, is clearly an important one."
The researchers say that leaf decomposition won't begin to decrease until after 2070, when much of it has been consumed by wildfires. The amount of radiation any one person encounters from wildfires alone would be below thresholds for harmful annual exposure, but, Mousseau said, any added amount of radiation poses an added risk.
"It may just be a very small amount, and so the likelihood of any individual suffering from that is very small," he told VICE News, "but when you spread this across the landscape and expose many people, some people are going to be affected."
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