The Frozen North is not so frozen after decades of global warming, and thawing permafrost is among the serious contributors to climate change, yet still one of the least well-known because it happens in sparsely populated regions of the Arctic.

“Permafrost covers 24 percent of the surface of land masses in the northern hemisphere and accounts for nearly half of all organic carbon stored within the planet’s soil,” notes an online report by the Arctic Institute. As permafrost thaws, “microbes will begin to eat the material, causing it to decay and releasing carbon dioxide and methane into the atmosphere. Even if a small fraction of these greenhouse gases are released, it will have major consequences on not only the Arctic, but Earth’s entire climate system, as they intensify global climate change.”

Thawing permafrost has already started to damage homes and infrastructure. It has destroyed a road at Delali National Park in Alaska, and is limiting access to large areas of the park. Researchers now are learning about yet another and still more hidden hazard of permafrost thaw: more radon released into homes and buildings. Radon is a naturally occurring gas that dissipates outdoors but can build up inside homes, increasing the risk of lung cancer and other health problems. After tobacco, radon is the second-leading cause of lung cancer in the United States.

Permafrost, a layer of ground frozen for at least two years, serves as a barrier to contain the radioactive gasses beneath it, explained researchers Paul Glover, from the University of Leeds, and Martin Blouin, co-founder of geoscience startup geoLEARN, who recently published a paper in Earth’s Future. They studied how radon – a naturally occurring colorless, odorless radioactive gas – can move through thawing permafrost and seep into homes.

While frozen, permafrost reduces radon levels by 90%

Their modeling study found that frozen permafrost can reduce radon levels to a tenth of what they would otherwise be. When permafrost thaws, the reservoir of radon is released. Indoor radon levels will not increase if homes are built on stilts or piles and therefore above ground level. In homes on slabs or having basements, radiation levels can increase a hundredfold, with higher levels for up to seven years, depending on factors such as how quickly the permafrost thaws.

The Arctic Circumpolar Permafrost Region has approximately 5 million inhabitants. Scientists estimate that by 2050, the permafrost in 42% of this area – where 3.3 million people live – may become degraded or may vanish. That possibility is concerning because the geology of the area increases the radon risk. The authors wrote that the northern polar regions “contain raised levels of U238 (radioactive uranium) and its decay products (Scheib et al., 2009), exacerbating the risk.”

According to the U.S. Environmental Protection Agency, radon-related lung cancer kills around 21,000 people each year, making it the second most common cause of the disease. Those who smoke are at even more heightened risk when exposed to radon. The authors note many Arctic communities have high levels of smoking, amplifying the risk.

“Even if it’s the second cause of lung cancer, people are not aware of this silent and invisible killer,” Blouin says. “It’s always a chance to raise awareness and maybe also realize the effect that climate change has on all areas.”

Structures built above ground level show no increased radon

Jennifer Athey, a geologist for Alaska’s Division of Geological and Geophysical Surveys, manages Alaska’s radon program. One challenge she faces when assessing radon risk in communities involves having only limited data.

“Alaska is sparsely populated and so the information that we have from test kits really comes from peoples’ homes and those are located in population centers, so the information that we have doesn’t really cover the whole state,” Athey says. “We have created some models where we think there might be radon based on other parameters like uranium in soils and sediments and things like that.”

She says that along with the data from population centers, the state is still trying to reach out to smaller communities and villages to gain more understanding of radon levels in other parts of Alaska.

For buildings constructed on top of piles or stilts, allowing air movement underneath, there are no reported increases in radon levels. Homes with basements below ground face higher risks. In northern areas underlain with permafrost, building on stilts or pilings is common, allowing for variations in the permafrost.

Much of northern Alaska is underlain with “continuous permafrost,” in a solid layer, but many lower regions have “discontinuous,” “sporadic,” or “isolated” sections of permafrost. Athey says that as the atmosphere warms, continuous and discontinuous permafrost lines will move northward.

“Places that used to be discontinuous permafrost or even continuous permafrost down the road are going to be available for people to build on,” she says, “ and that’s going to open up new land for people so they might be building with more traditional techniques with cross bases and basements.” These techniques, popular in the Lower 48, can increase radon levels indoors.

Avoid putting out a ‘welcome mat’ for increased indoor radon

An additional hazard in bitterly cold climates is that a home’s heating system can pull radon out of the ground and into the home. As hot air rises, heaters can create negative pressure, drawing gases up from the ground.

“In Alaska in the winter time, particularly when people are running their heaters, the stack effect happens, where air in the house that is hot goes up and out of the house, and that actually creates a negative pressure environment in the house and draws in ground gases.” The result “creates an environment that really invites radon into the home.”

She pointed out that running things like stove and bathroom fans and heaters will pull out hot air and exhaust. “The air has to be made up from somewhere, and if your house is built very tightly because you want to keep your house warm, but the foundation has cracks, that air makeup is going to come from the ground, and that’s where the radon is,” Athey says.

When homes or buildings test high for radon, a variety of methods can help mitigate the radon level. Sometimes, sealing basement cracks, joints, and seals around pipes will help reduce radon levels, but at other times a mitigation system involving ventilation or pressurization may be necessary.

However, building houses to be radon-resistant from the start is the most effective and least expensive way to control for radon, according to Athey.

“Radon-resistant home construction is very important, and that’s something that we try to highlight in Alaska, and it’s a lot cheaper to install radon mitigation from the get-go when you’re building your house than to try and retrofit and mitigate a problem that’s already there,” Athey says

The study authors note this paper is an initial study, and they say more studies are needed to model variations in radon, building ventilation, speed of thaw, soil compaction, and other factors.

However, their work serves as a warning that thawing permafrost may have a wide range of impacts on people’s health and well-being, bringing more awareness to this little-known issue.

“Education and outreach is very important because a lot of people in Alaska don’t know about radon,” Athey says.

Kristen Pope

Kristen Pope is a freelance writer and editor who frequently writes about climate change, ecology, wildlife, conservation, and many other topics for a wide variety of publications. She has a masters degree...