A radioactive gas is lurking under the permafrost

This story was originally published by Known Magazine.

Deep in the frozen ground of the North, a radioactive hazard has been trapped for millennia. But British scientist Paul Glover realized a few years ago that it wouldn’t always be like this: one day it might come out.

Glover had attended a conference where a speaker described the low permeability of permafrost – soil that remains frozen for at least two years or, in some cases, thousands. It’s a shield of ice, a thick blanket that blocks out contaminants, microbes and molecules beneath the foot — and that includes the cancer-causing radioactive gas, radon.

“It immediately occurred to me that, well, if there’s radon underground, it’s trapped there by a layer of permafrost,” recalls Glover, a petrophysicist at the University of Leeds in England. “What happens if that layer is suddenly not there anymore?” Since then, Glover has been working on methods to estimate how much radon — which is released as the element radium decays — might be released as climate change causes the permafrost to thaw.

Significant areas of arctic and subarctic ground contain permafrost – but today it is melting and the rate of that thaw is accelerating. In a report published in January, Glover and his co-author, Martin Blouin, now technical director at mapping software company Geostack, used modeling techniques to show that homes with basements built in areas of permafrost could be exposed to high levels of radon gas. in the future. “As the permafrost thaws, this reservoir of active radon can flood the surface and enter buildings — and because it’s in buildings, it poses a health hazard,” Glover says.

No one knows exactly how quickly radon diffuses through icy ground, but by using the rate of diffusion of carbon dioxide and adjusting the properties of radon, Glover came up with a figure he could use in the model. Based on 40% permafrost thawing, calculations reveal that radon emissions can increase radioactivity levels to more than 200 becquerels per cubic meter over a period of more than four years in homes with basements at or below ground level. his. This happens when the 40% thaw occurs in 15 years or less.

According to the World Health Organization, the risk of lung cancer increases by about 16% for every 100 becquerels per cubic meter of long-term exposure. Some countries, including the UK, set the maximum safe level of average exposure at 200 becquerels per cubic meter. But without testing for radon in areas where geology suggests it’s present, people won’t know if they’re at risk — because the gas is odorless, colorless and tasteless.

Glover emphasizes that the paper’s model is an early attempt to understand how thawing permafrost might affect people’s exposure to the gas. It doesn’t account, for example, for seasonal variation in the rate of permafrost thaw or the effects of soil compaction when the ice within it melts, something that could pump even more radon to the surface.

About 3.3 million people live in permafrost that will have completely melted by 2050, according to estimates from a 2021 study. Not all of these people live in radon-prone areas, but many do: for example, in parts of Canada , Alaska, Greenland and Russia. And the link between radon exposure and lung cancer is well established, as is the fact that smoking further increases the risk, says Stacy Stanifer, a specialist in clinical oncology nursing at the University of Kentucky College of Nursing. She points to studies that suggest radon may be behind up to one in 10 lung cancer deaths, of which there are more than 1 million in total worldwide each year.

“Breathing in radon is dangerous for everyone, but it’s even more harmful when you also breathe in tobacco smoke,” says Stanifer. Smoking is prevalent in arctic and subarctic communities; for example, a 2012 study reported that more than half of Canadian Inuit aged 15 and older living in the Inuit homeland said they smoke cigarettes daily, compared with 16% of Canadians overall.

Scientists don’t know how much radon is actually emanating from areas of thawing permafrost today, says Nicholas Hasson, a geoscientist and Ph.D. University of Alaska Fairbanks student: “I would call that a point blank.” He notes that in real life permafrost layers are complex and irregular, and agrees with Glover that field measurements are essential to validate the model. Instead of a uniform layer of ice underground, imagine permafrost more like Swiss cheese ice, with some areas much thicker than others and places where groundwater runs through it, exacerbating thaw.

Hasson and his colleagues studied places where permafrost is melting unusually fast and emitting methane, a greenhouse gas many times more potent than carbon dioxide. Similar “chimneys” could be spewing high amounts of radon gas in some places, he suggests.

For human health, what really matters is the amount of radon that enters people’s homes. Scientists and even the owners themselves can use radioactivity detectors to assess this. A study published online in February 2022, which has not yet been peer-reviewed, measured radon levels over a year in more than 250 homes in three Greenland cities. Of the 59 homes in Narsaq, for example, 17 were found to have radiation levels above 200 becquerels per cubic meter.

The study’s lead author, Violeta Hansen, a radioecologist at Aarhus University in Denmark, emphasizes that these are the first results based on a small number of households. It would take a lot more research, she says, before she could assess the health risks associated with radon on properties like these in Greenland. She now leads an international project that will carry out field experiments and gather radon measurements from homes in several countries, including Canada and Greenland. “We need to get back to the public with validated, low-cost mitigation measures,” says Hansen.

It’s important to avoid panicking people without data and solid solutions at hand, says Aaron Goodarzi, a radiobiologist at the University of Calgary in Canada. The good news is that there are tried-and-true methods to reduce radon levels inside a home once the homeowner knows it’s there. Goodarzi points, for example, to a technique called “under-slab depressurization,” in which a sealed tube is inserted below the house and connected to a fan. This sucks up any radon from underneath the building before expelling it into the atmosphere. “Think of it simply as a detour,” he says.

The type of building matters. Glover’s model found that houses built on stilts or stilts, and therefore detached from the ground, did not experience an increase in radon levels. Fortunately, many homes in the Arctic and sub-Arctic are built this way. But for those that aren’t, the cost of mitigating radon can be prohibitive for low-income communities in these regions. “This is an equity issue that has to be considered, certainly,” says Goodarzi, who notes that the onus may fall on social housing administrators in some areas to ensure that the housing they provide is healthy.

A spokesperson for Health Canada says the government agency currently recommends that homeowners test their properties for radon levels and use certified vendors to install mitigation technologies if necessary.

Many people may not think much of radon, as it is invisible. Glover says that getting informed now, before the permafrost thaws worse, could save lives.

“We know people die from it,” he says. “But at the same time, there is a lot we can do to protect ourselves.”

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