Permafrost thaw could expose Arctic population

University of Leeds


Thawing permafrost could expose Arctic populations to carcinogenic radon

Thawing permafrost due to climate change could expose people in the Arctic to much higher levels of radon, an invisible gas that causes lung cancer, a new study has found.

Professor Paul Glover from the University of Leeds and his co-author suggest that permafrost has always acted as a protective barrier, preventing radon from rising to the surface and entering buildings there.

Radon is a natural, invisible and odorless radioactive gas. It causes about one in 10 lung cancer deaths and affects smokers far more than non-smokers. It causes higher death rates in subarctic communities due to the prevalence of smoking.

Their study, published today in the AGU Review Earth’s future, modeled radon production, its flow through soil, permafrost, and model buildings – including those with underground and surface basements and those built, more traditionally, on piles.

They show that in buildings with basements, the presence of radon gas can increase to more than 100 times its initial value for up to seven years, depending on the depth of the permafrost and the rate at which the permafrost thaws.

This demonstrates the importance of not only keeping the permafrost layer intact in limiting global warming, but also has important implications for health services, building codes and ventilation guidance.

The presence of a layer of permafrost was found to act as a barrier against radon, reducing surface radiation to one-tenth the background level, but increasing the radon concentration behind the barrier by up to 12 times. This was the case for a wide range of depths down to the permafrost layer.

Professor Glover, of School of Earth and Environment in Leeds, said: “Radon is known to be the second leading cause of lung cancer after smoking. Smoking also exacerbates rates of radon-acquired lung cancer by approximately 26 times, and smoking is up to 4.4 times more prevalent in Arctic communities.

“As a result, an unexpected radon plume could pose a dangerous health hazard if not anticipated. Fortunately, simply installed ventilation is all that is often needed if the problem is recognized.

“If the permafrost was stable, there would be no need to worry. However, it is now widely recognized that climate change is causing significant permafrost thaw, with a projected loss of 42% permafrost in the Arctic Circumpolar Permafrost Region (ACPR) by 2050.

“The radon can then travel through the permafrost and lead to a plume of radioactive gas in buildings that takes several years to peak and many more to dissipate.”

The publication Earth’s Future suggests that the thawing of the permafrost barrier produces no increase in radon over the background level of traditionally constructed buildings in the Arctic community, which are built on piles.

For buildings with basements, thawing permafrost can cause the radon concentration to remain above the value of 200 becquerels per cubic meter (Bq/m3), which many countries use as an action threshold, until to seven years depending on permafrost depth and thaw rate.

Professor Glover added: “Our results clearly show that the accumulated reservoir of radon can be released in building basements over a long period of time and will remain above radiation action levels for four to seven years.

“As there has been no historical perceived radon problem in these communities and the gas itself is undetectable without specialized devices, we view this as a significant and completely preventable threat to the health of northern communities.”

Professor Glover points out that these are initial results that had to include many assumptions, not least because there is a significant lack of data on the petrophysical properties of Arctic soil and permafrost.

It is possible that radon finds efficient pathways to the surface by advection and diffusion and along areas of preferential thawing while most permafrost thaws more slowly.

Professor Glover is part of the internationally renowned Institute of Applied Geosciences and petrophysics and geomechanics group. Their work includes the theory, modeling, measurement and applications of earth materials and processes. He was the founder and first president of the Energy, resources and environmentdividing the European Geophysical Union.

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