The second leading cause of lung cancer in Canada, after cigarette smoking, is something most people have never heard of.
Radon gas, a naturally occurring substance which can be found everywhere, causes 3,000 lung cancer deaths per year in Canada.
"Most of our customers don't know much about radon," said Chuck Cullen, project manager with Team Construction Management Ltd in Kelowna, B.C. Cullen says radon is prevalent in British Columbia between the Coast Mountains and the Alberta border.
"The Kootenays (mountain range)] are part of a belt with a high radon concentration," he said. "It's killing people left, right and centre there."
Radon is not a problem outdoors, where it dissipates harmlessly in the air. But it can collect and concentrate indoors, and that's when radon can become dangerous, Cullen says.
Radon is an invisible and odourless gas that comes from the natural breakdown of uranium in the soil.
It can seep into buildings — both old and new — through foundation cracks and other openings, mostly through their basements, from where they spread to the rest of the structure.
Long-term exposure to the gas causes changes in the body's DNA, leading to cancer.
The connection between radon gas and lung cancer was made in the 1970s, after uranium miners in Elliot Lake, Ont. were found to have unusually high lung cancer rates.
In the 1970s and 1980s, researchers started to look at radon gas exposure in single- and multiple-family housing.
In the last 10 years the presence of radon in homes has been getting more attention. More Canadian homeowners are getting their homes tested now, says Aaron Goodarzi, assistant professor in the Arnie Charbonneau Cancer Institute at the University of Calgary.
"The science has advanced to the point where we know radon is a major public health issue, and one that is preventable," he said.
In addition to the interior of B.C., the incidence of radon in Canada is high across the Prairies, in southern Ontario and Quebec and also the Maritimes.
"The prevalence of radon depends on regional geology and the amounts of uranium, thorium or radium (whose breakdown leads to radon) that are present," Goodarzi said.
Compared to other regions of the world, Canada is a radon high-risk country, particularly in the winter.
"The greater the temperature differential between the cold outdoors and the warm indoors, the more radon gets sucked inside," Goodarzi said.
In addition, the houses that were built recently, because they are bigger and taller, and many of them have high ceilings, are better radon suction devices than older houses.
"They are also more tightly sealed, which concentrates the radon," Goodarzi said.
In addition, today's concrete makes it easier for radon to seep in.
"It shrinks more over time, which lets radon gas get in through the cracks that form," said Goodarzi.
The cost to a builder of including radon-resistant features in a new home during construction can vary widely, according to the U.S. Environmental Protection Agency (EPA).
The agency also notes that the cost of including these features is typically less than the cost to mitigate a home after construction.
According to the EPA, there are five basic features that builders should include to prevent radon from entering a building:
- Gravel: Use a four-inch layer of clean, coarse gravel below the foundation. The gravel allows radon and other soil gases to move freely underneath the structure.
- Plastic Sheeting or Vapour Retarder: Place heavy duty plastic sheeting or a vapour retarder on top of the gravel to prevent the soil gases from entering the house. The sheeting also keeps the concrete from clogging the gravel layer when the slab is poured.
- Vent Pipe: Run a three- or four-inch solid PVC Schedule 40 pipe, like the ones commonly used for plumbing, vertically from the gravel layer through the structure's conditioned space and roof to safely vent radon and other soil gases outside.
- Sealing and Caulking: Seal all openings, cracks, and crevices in the concrete foundation floor and walls with polyurethane caulk to prevent radon and other soil gases from entering the home.
- Junction Box: Install an electrical junction box for use with a vent fan, if, after testing for radon, a more robust system is found to be needed.
In Canada, Radon Environmental Management Corp. in Vancouver provides a number of products and services, including radon probability mapping, to identify and mitigate radon gas.
"Constructing a building with radon-ready features is certainly good for air quality," said David Innes, Radon's director of sales. "But it also lowers energy costs."