More than twice as many Manitoba homes would test over the recommended limit for radon gas in homes than they do now, if Canada had adopted World Health Organization recommendations.
Radon levels across Canada
Want to know the radon test results in your neighbourhood? Search our interactive map. CBC News has plotted the radon results in Manitoba and across the country from Health Canada's survey.
Radon is a radioactive gas that seeps into homes from decaying uranium found in rocks and soil beneath foundations.
According to almost 14,000 never-before-released radon test results, obtained from Health Canada by CBC News, 280 homes in Manitoba recently tested over the agency's suggested guideline of 200 becquerels.
The Health Canada survey found that Manitoba has the second-highest percentage, at 23.7 per cent, of homes in the country with radon concentrations over 200 becquerels.
But that number of homes would more than double if Canada adopted the World Health Organization's limit of 100 becquerels.
According to WHO, the risk of lung cancer increases by 16 per cent with every 100 becquerel of radon.
- Interactive Map | Radon gas levels across Canada
- High radon levels found in Health Canada tests across country
Radon expert Anne-Marie Nicol, an assistant professor in health sciences at Simon Fraser University in Burnaby, B.C., says she would like to see Canada strengthen its radon exposure guidelines.
"Small amounts have negligible risk, but that's not zero risk," she said.
Kelley Bush, Health Canada's head of radon education and awareness, said the Health Canada's guideline is voluntary and there are no plans to lower the national guideline to 100 becquerels.
"Its a lengthy process to lower a guideline," she said. "It would put on hold everything that we're currently doing under our National Radon Program."
Bush said Health Canada will continue to review the limit.
'No one could figure it out'
Radon is also the second leading cause of lung cancer deaths, killing almost 3,000 Canadians annually.
That's a statistic that Winnipegger Ed Shinewald knows all too well.
His late wife, Sharon, fell in love with their River Heights home 13 years ago and they bought it on the spot.
"It's a beautiful house," said Shinewald. "We both liked it quite a bit."
Five years ago, Sharon died of lung cancer at the age of 64 — a tragedy that her husband says didn't make sense to him since she had quit smoking years earlier.
"It's always been a mystery," he said. "No one could figure it out."
After Sharon's death, Shinewald began to wonder if elevated radon levels had played a role in the disease that killed her.
Shinewald bought a kit and, to his shock, the levels were three times higher than the recommended limit.
"We were way up," he said. "It was imperative that I do something about it."
He hired a Winnipeg company to remediate the radon and put in a capture system that brought his home's radon levels down to zero.
Nicol said each individual home may require different means to get rid of radon, but the first thing to do is test for the problem.
Testing should be mandatory through legislation, she said.
"I'd like people to be required to test," she said. "It's serious enough,"
But Bush rejects the call for mandatory testing.
"I think Canadians need to know about it," she said. "But ultimately the decision to reduce those risks and to take action needs to be the individuals."
Shinewald said he can't be sure how his home's high radon affected his wife, but he has a message for all other homeowners.
"Test, test, test," he said.
"If we can't have a law that says no radon, then I guess the next best thing is to somehow make it clear to people that this could be playing with fire."