Thousands of Canadians are at risk because Health Canada has been slow to change guidelines on a radioactive gas that causes lung cancer, the head of the Radiation Safety Institute of Canada says.

"Those deaths are entirely preventable," said Fergal Nolan. The cause is radon gas, which seeps into houses  through cracks in foundations. It's the second-leading cause of lung cancer, after smoking, killing nearly 1,600 Canadians in 1997, a government report said.

But Health Canada rejects the charge. In an e-mail to CBC News Online, spokeswoman Renée-France Bergeron
said there was no statistically valid research that linked radon and lung cancer until studies in 2004-05.

"Upon publication of these combined studies, Health Canada acted quickly to recommend a lowering of the Canadian radon guideline," she said. That is expected this fall. 

There had been studies suggesting a link between radon and lung cancer in the 1990s, but "none of the studies had sufficient statistical power to conclusively establish the link."

Health Canada is planning to change the permitted level this year, which is currently four times the level in many other Western countries.

"We're in the backwoods here in radon in homes. We're at least 20 years behind the United States and the European Union," said Nolan. "Even China is ahead of us now on guidelines and standards for homes related to radon."

$125 million a year to fix

Radon is easy to deal with, Nolan said. "You can seal the cracks and protect your family."

But again, the government is figuring out how to implement its new standard, Bergeron said. There is a cost to changing the rules, and the government is considering responces to its proposed change.

With about 2.7 per cent of Canadian homes potentially over the new standard, it will cost about $125 million a year to radon-proof homes, schools, and hospitals in the first 10 years, according to a recent report by the federal-provincial-territorial radon protection committee. Homes account for more than $122 million of the total.

Uranium creates radon

Radon gas is formed as uranium in the ground disintegrates. It can invade homes by leaking through cracks in the foundation. The gas and its byproducts occur naturally everywhere, in soil, water and air, but usually in concentrations too low to pose a threat.

But it can accumulate in confined spaces such as basements and crawl spaces in homes. If the levels are high enough, it can be a health hazard.

The current Canadian limit of 800 becquerels per cubic metre of air, is too high. (A becquerel is a measure of radioactive decay.)

A panel reporting to Health Canada in March recommended using the limit set in Britain, Sweden and Norway: 200 becquerels per cubic metre.

It also recommended taking remedial measures for homes with levels above 800 becquerels per cubic metre within a year.

Bergeron was unaware of government reaction to the recommendation to fix older homes.