Exposed to radiation right inside your own home? That is a scary prospect indeed. Canadian health authorities have estimated that over 500,000 Canadians could be constantly exposed to radiation from radon gas.
Radon is a naturally occurring radioactive substance and byproduct of the decay of uranium in soils and rocks. It is considered a leading cause of lung cancer after smoking.
Unfortunately it can also build up to dangerous levels inside homes. It is such fears that have prompted Health Canada to propose to significantly lower the threshold at which homeowners should take remedial action to reduce the risk.
"After careful study, considering all the options, we came to the conclusion that, yes, it is indeed time to lower the guideline," Bliss Tracy, head of radiological impact for Health Canada, said in an interview.
Radon hot spots include Winnipeg, Nova Scotia, and British Columbia's Interior, where an estimated 60,000 residents live in homes that pose an unacceptable risk of lung cancer.
The B.C. Centre for Disease Control confirms "there are thousands of British Columbians blissfully unaware that their homes could be slowly and quietly killing them."
Health Canada estimates radon gas kills 2,000 people annually in this country, more than fires, drownings, air crashes, and accidental poisonings combined, and one-tenth of the estimated 20,000 radon deaths in the U.S.
Radon gas is odourless, colourless and tasteless; like smoking, it can take many years of radon inhalation to damage lung tissue at the DNA level and result in cancer.
"Radon is not a drop-dead-tomorrow situation," said Brian Phillips, director of radiation protection services for the B.C. Centre for Disease Control. "It's a lifetime health risk."
Residents of radon hot spots should take the issue seriously, he said. "People need to be paying attention to this one. They must make an informed judgment."
Uranium mining, which occurs in Canada only in northern Saskatchewan, is not generally to blame for radon gas seeping into homes. An exception is Oka, Que., where radioactive tailings from an old niobium mine has been blamed on elevated readings in homes, said Tracy.
Dave Lefebure, chief geologist with the Ministry of Energy, Mines, and Petroleum Resources in Victoria, said low levels of uranium are found in granitic rocks throughout B.C. Only in certain areas are these background levels sufficient to cause radon gas problems in homes.
He said B.C. has never had a uranium mine, and not a lot of exploration activity.
Canada is poised to lower the guideline for radon gas in homes to 200 becquerels per cubic metre from 800 becquerels (a measurement of radioactivity), which means that thousands of homes that would have been considered safe are now viewed as a potential source of lung cancer.
For the relatively few Canadians who are aware of radon gas and have tested their homes for it, elevated readings can have a traumatic effect. "Oh God, now what?" is how Craig Besinque, a school bus driver from New Denver in B.C.'s West Kootenay region, responded. "We were pretty frightened."
He spent about $700 on supplies and did his own remedial work on his house, including sealing openings in the basement and installing a ventilation fan, and is now retesting with fingers crossed. "It's horrible to think your house has radon," added his wife, Lane Heywood, a retired teacher. "There are a lot of bad things to think about."
The World Health Organization estimates radon causes up to 15 per cent of lung cancers worldwide. An estimated 22,700 Canadians last year were diagnosed with lung cancer, one of the deadliest forms of cancer. The five-year survival rate for lung cancer is about 14 per cent, the B.C. Cancer Agency reports.
Health Canada has maintained the 800-becquerel guideline since 1988, but says new research showing a stronger link to lung cancer has prompted the change to 200, with support of the provinces and territories.
Officials estimate that people spending 75 per cent of a lifetime (of 70 years) inside a home with a main floor radon concentration of 800 becquerels have a one-in-10 chance of developing lung cancer from radon gas.
A comprehensive scientific study, published in Epidemiology in 2005 and entitled Residential Radon and Risk of Lung Cancer, found "direct evidence of an association between residential radon exposure and lung cancer."
The study examined radon studies in regions as widespread as North America, Europe and China, and incorporated the results of lab research, including experiments on animals, and studies of underground miners.
Individuals who test for radon and remediate their homes, however, can relatively easily reduce the risk to acceptable levels.
Canadians living in known radon hot spots, especially those with porous soils, are urged to test for radon gas and take remedial action on their homes as necessary to reduce the risk.
Radon test kits are available on the Internet for less than $50 and are completed over three to six months during winter, when doors and windows are closed and radon levels are highest.
Remediation options, costing from a few hundred to a few thousand dollars, include sealing cracks in concrete floor slabs, fitting airtight covers on sumps, installing special traps in basement drains, covering over exposed soils, and installing a ventilation system to move the radon outdoors.
A National Research Council report for the Environmental Protection Agency said that while eliminating all radon is not feasible, an estimated one-third of radon-induced lung cancers could be avoided if homes met the guideline of 150 becquerels.
Some suggest not nearly enough has been done in Canada to reduce the radon risk.
"When you compare us to the worldwide scale, it's pretty shocking how long we went with such high levels," said Erik Stout of Fernie-based Rocky Mountain Inspections, a company that specializes in testing radon in homes.
He called for greater public awareness about radon gas, noting "most people don't know what it is. Half the challenge is explaining it to people. They're not very responsive to it."