Radon levels in new Canadian homes now 467% higher than in homes in Sweden, U of C study finds

Forty years after Canadian and Swedish homes were found to have comparable levels of radon gas, a new University of Calgary study suggests radon levels in recent builds in Canada now far exceed their Swedish counterparts — by 467 per cent.

Inhalation of the radioactive gas is the leading cause of lung cancer in non-smokers, and about 3,200 Canadians die from exposure each year, according to Health Canada.

And without intervention, say the team of cancer researchers and Canadian architects behind the U of C study, the average radon level of a new Canadian home will increase another 25 per cent over current levels by 2050.

Those levels are already the third-highest in the world.

"In most regions, [Canadian radon] has gone up, while Swedish radon has systematically gone down," said Aaron Goodarzi, an associate professor at the University of Calgary's Cumming School of Medicine.

And now, the researchers are trying to find out why.

"It is probably a complicated mergence of just the way we as Canadians build our houses, the way we heat our houses — which is actually quite different from the way the Swedes do it — as well as the uniqueness about Canadian behaviour," Goodarzi said.

Goodarzi is also the scientific director of the Evict Radon National Study, a Canada-wide initiative that seeks, in part, to educate Canadians about the harmful effects of radon.

Odourless, tasteless and naturally occurring, radon gas is created from the decay of uranium in minerals found in rock, soil and water, according to Lung Cancer Canada.

It's also present in all indoor environments — but by how much is a key factor when evaluating its safety.

"One in five Canadian houses exceed 200 bq/m3," Goodarzi said. "Now, that's what Health Canada sets as the maximum tolerated radon exposure limit — you start to see a cancer risk at 100."

For their study, the U of C researchers said they chose to compare radon levels in Canada with those in Sweden because the Nordic country has similar climates, as well as data on the subject that goes back decades.

In the 1950s, Swedish properties actually exceeded Canada's houses in radon levels, Goodarzi said. This levelled off around in the 1980s, when the two countries were about the same.

For the more recent study, teams from across Canada analyzed long-term radon tests and buildings from more than 25,000 Canadian and 38,000 Swedish residential properties constructed since the Second World War.