Monday, September 26, 2022

How climate change is putting millions of people at risk of radon exposure

This article originally appeared in Noble Magazine, an independent journalism effort of annual reviews.

Deep in the frozen plain of the north, a radioactive threat has been lurking for millennia. But UK scientist Paul Glover realized a few years ago that this will not always be the case: one day it may run out.

Glover attended a conference where a speaker described the low permeability of permafrost – ground that remains frozen for at least two years, or in some cases thousands. It’s an icy shield, a thick blanket that harbors contaminants, germs and molecules beneath the feet—and that includes the cancer-causing radioactive gas radon.

Read more: How melting permafrost is changing the Arctic

“It occurred to me immediately that, if radon is underground, it will be trapped there by a layer of permafrost,” recalls Glover, a petrophysicist at the University of Leeds in England. “What if that layer suddenly isn’t there anymore?” Since then, Glover has worked on ways to estimate how much radon—which is released as the decay of the element radium—might be free as permafrost melts due to climate change.

Permafrost occurs over significant areas of arctic and sub-Arctic land – but today it is melting, and the rate of that thaw is accelerating. In a report published in January, Glover and co-author Martin Blauin, now technical director of mapping software firm GeoStack, used modeling techniques to show that homes with basements built on areas of permafrost could be exposed to higher levels of radon gas in the future. can be brought in contact with. “As permafrost melts, this reservoir of active radon can flood the surface and seep into buildings — and getting into buildings, pose a health hazard,” Glover says.

No one knows how quickly radon spreads across an icy plain, but by using the rate of diffusion of carbon dioxide and adjusting the properties of radon, Glover came up with a shape he could use to model. Based on 40 percent permafrost thaw, calculations suggest that radon emissions can increase radioactivity levels by more than 200 becquerels per meter cubed (Bq/m3) in homes with basements at or below ground level. for a period exceeding four years. This is when 40 percent of the thaw occurs in 15 years or less.

According to the World Health Organization, the risk of lung cancer increases by about 16 percent with every 100 bq/m3 of prolonged exposure. Some countries, including the UK, have set a safe level of 200 bq/m3 of average exposure. But without testing for radon in areas where geology shows it is present, people would not know if they are at risk – because the gas is odorless, colorless and tasteless.

Glover stresses that the model in the paper is an early effort to understand how thawing permafrost might affect people’s exposure to the gas. For example, it does not account 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 more radon to the surface.

According to a 2021 study estimate, some 3.3 million people live on permafrost that will melt completely by 2050. Not all of these people live in areas prone to radon, but many do: for example, in Canada, Alaska, Greenland, and parts of Russia. And the link between radon exposure and lung cancer is well established, as is the fact that smoking further increases one’s risk, says Stacy Stanifer, an oncology clinical nurse specialist at the University of Kentucky College of Nursing. She points to studies showing that radon may be behind 1 in 10 lung cancer deaths, of which there are a total of 1 million worldwide each year.

“Breathing radon is dangerous for everyone, but it’s even more harmful when you inhale tobacco smoke,” says Stanifer. Smoking is prevalent in arctic and sub-arctic communities; For example, a 2012 study reported that nearly two-thirds of Canadian Inuit who are 15 years of age and older who live within an Inuit homeland said they lived daily, compared to 16 percent of Canadians overall. smoke cigarettes.

In arctic and sub-arctic regions, radon in the ground is blocked from entering homes by a layer of rock-hard permafrost. But when permafrost thaws – as is happening rapidly due to climate change – the level of risk in homes will be greatly influenced by the structure of the house. Modeling studies suggest that exposure can increase 100-fold over the years when homes are built with basements, either buried or above ground. Conversely, houses built on piles are protected, as radon escapes into the atmosphere.

Scientists don’t know exactly how much radon is actually being released from areas with melting permafrost today: “I’d call it an empty space,” says Nicholas Hassan, a geoscientist and PhD student at the University of Alaska Fairbanks. He notes that, in real life, permafrost layers are complex and irregular, and agrees with Glover that field measurements are necessary to validate the model. Instead of a uniform sheet of underground ice, imagine permafrost as a higgledy-piggledy Swiss cheese of ice, with some areas much thicker than others and places where groundwater courses through it to melt.

Haasan and his colleagues have studied places where permafrost is melting unusually rapidly and emitting methane, a greenhouse gas many times more potent than carbon dioxide. They suggest that similar “chimneys” may have spewed high amounts of radon gas in some places.

For human health, what really matters is the amount of radon that enters people’s homes. Scientists and even homeowners can use radioactivity detectors to assess this. A study published online in February 2022, which has yet to be peer-reviewed, measured radon levels over the course of a year in more than 250 homes in three Greenland cities. For example, 17 out of 59 NARSAC homes had radiation levels above 200 bq/m3.

Lead author Violet Hansen, a radioeconologist at Aarhus University in Denmark, stresses that these are early results based on a small number of houses. She will do more research before she can evaluate the health risks associated with radon in properties like these in Greenland. She is now leading an international project that will run field experiments and collect radon measurements from homes in various countries, including Canada and Greenland. “We need to get back to the public with low-cost and effective, validated mitigation measures,” Hansen says.

Without solid data and a solution at hand, it’s important to avoid scaring people off, says radiobiologist Aaron Gudarzi of the University of Calgary in Canada. The good news is that there are tried and tested ways to reduce radon levels indoors once the homeowner knows it is there. Gudarji, for example, points to a technique called sub slab depressurization, in which a sealed pipe is inserted under the house and connected to a fan. It expels any radon from under the building before blowing it into the atmosphere. “Just think of it like a bypass,” he says.

The type of building matters. Glover’s model found that houses built on piles or stilts, and thus separated from the ground, did not experience increased radon levels. Fortunately, many homes in the arctic and sub-arctic have been built in a similar way. But for those who are not, the cost of reducing radon can be prohibitive for low-income communities in these areas. “It is an equity issue that certainly has to be considered,” says Gudarji, who notes that in some areas it is up to social housing administrators to ensure that the housing they provide is healthy.

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

Many people don’t think about radon very much, given the fact that it is invisible. Glover says that getting information now before the permafrost starts to break down could save lives.

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

Known Magazine |  annual Review


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