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All too often ignored, excessive radon exposure affects 1 in 10 homes in Quebec and leads to more than 3,000 deaths in Canada every year.


A researcher is warning about radon exposure in new structures. Aaron Goodarzi of the University of Calgary has found that the number of lung-cancer cases attributed to this colorless, odorless, and invisible gas could grow.


Radon is a radioactive gas and carcinogen that arises from the decay of uranium naturally present in the ground. It makes its way into a structure through all openings in contact with the ground, specifically through cracks in foundations and slabs, and spaces around pipes.


Radon exposure over a long period of time can cause lung cancer and is the chief cause of cancer amongst non-smokers.


There are some well-established myths about radon. It had long been thought that old houses were more prone to have high radon levels.


Now, with his study published in Scientific Reports, Aaron Goodarzi, a PhD in radiation biology, demonstrates that the opposite is true.


"One of our study's main findings was that the newer the house is, the more radon it contains. This means that our construction codes produce homes with higher radon levels" says Goodarzi.


It is thanks to his Evict Radon program that Aaron Goodarzi has compiled radon test characteristics and results for close to 12,000 households in Alberta and Saskatchewan. This is a gold mine of information that has allowed him to debunk this myth.


Health Canada has established a radon-exposure limit of 200 Bq/m3. The federal agency recommends that when radon levels exceed this limit, mitigation measures should be taken to decrease these levels as close to zero as possible. This is keeping in mind that there is no level of radon exposure that is completely safe for human health.


Goodarzi's research shows that 11% of homes built before 1974 exceeded this level of 200 Bq/m3. Now, radon levels exceed this limit in 21% of homes built between 2005 and 2018.


Holes in the Quebec construction code


The finding that new construction exposes residents to greater radon levels is troubling, since it is in Quebec that the construction code in force has significant holes regarding radon. It is all across Canada that the maximum radon-exposure level is 200 Bq/m3; however, this is not the case in Quebec, explains Marco Lasalle.


"The limit in Quebec is 800 Bq/m3. So, either we are making a mockery of this, or the average Quebecer has a stronger makeup than other Canadians and is able to withstand radiation better", Lasalle says. "It is very clear that we have not taken radon seriously. On the one hand, we did not understand it. On the other hand, we downplayed its importance".


Health Canada lowered the official limit from 800 to 200 Bq/m3 in 2007. Quebec's construction code, however, continues to apply the old limit.


"This was definitely an unpleasant surprise" says Mathieu Brossard, a radiation specialist at Health Canada. "We made recommendations to the Quebec Building Authority to make the proper updates... Everyone agrees that this is the number one cause of lung cancer amongst non-smokers and that this must be foreseen in construction".


Mathieu Brossard believes that if it is only a home's energy performance that is worked on and that gas infiltrating from the ground is not taken into consideration, then this is a recipe for disaster. "7% of homes on the Island of Montreal have a radon problem. 1 in 10 homes in Quebec have a radon problem. This is a problem all across Canada. This is a global problem".


Another gaping hole in the Quebec building code, according to Marco Lasalle, is that it does not require automatically installing a depressurization system under the slab in all new construction, which is what the national building code does. Once built with a ventilation system and exterior removal, this system allows to discharge radon to the outdoors.


The Quebec code is limited to "at-risk" zones despite that it is now established that one can no longer talk about such zones, since radon is everywhere.


When questioned about the holes in the Quebec building code, Andrée Laforest, the Minister of Municipal Affairs and Housing and Head of the Quebec Building Authority (QBA), declared in an email that "radon is a public health challenge of concern for her government. The Minister adds that the QBA will have to evaluate "the possibility of updating regulations to make sure that the standards in Quebec effectively protect the public". She has also mandated the QBA to launch a cross-industry committee on radon to put together recommendations for housing.


The risk is everywhere


A lot has been mentioned over the years about radon in certain regions and cities in Quebec, such as in Saint-Hilaire and Oka. So, we should no longer talk about at-risk zones.


This notion is simply out of date, says Mathieu Brossard. "When our directive was 800 Bq/m3, there were very few zones that exceeded this level. Now, since the level was lowered in 2007 to 200 Bq/m3, it is exceeded everywhere", explains the radiation specialist at Health Canada.


"Trying to predict radon levels with mapping doesn't work well", he says. It is therefore impossible to identify only certain sectors or certain types of soil, Brossard notes.


A risk all year long


The data collected by Evict Radon also made it possible to debunk another myth that went that radon is a problem mostly in the winter. Aaron Goodarzi found that radon levels just as elevated can be found in the winter and summer. "This is surprising! This completely upends everything that we had thought to know about radon in the 20th century", he says.


This is explained by significant changes in how we live in our homes: summers are hotter, air conditioners are spreading in usage more and more, and windows are shut in both summer and winter, thus trapping radon indoors.


The only thing to do is to test!


Even though only 7% of homes in Canada have been tested for radon, Health Canada's message is clear: test your home to find out your radon levels. "Whether you have a new or old home, whether you have an air conditioner or not, or whether you live next to a mountain or not, these are not criteria", says Mathieu Brossard.

Radon: An Invisible Threat No Matter Where You Live