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By Martin Mittelstaedt
Environmental Reporter

Canada needs to tighten its radon exposure guidelines dramatically and should cut by 75 per cent the amount of the deadly radioactive gas considered safe in homes and schools, says an advisory panel of health experts drawn mainly from Health Canada and the provinces.  Canada has one of the most permissive radon exposure standards in the world, higher even than those of some developing countries.  The panel is proposing a lower limit to reduce the incidence of lung cancer, the primary health threat from the gas.

In its report to the federal and provincial governments, the panel estimates that radon exposure causes about 10 per cent of all lung cancers.  Based upon 2005 figures, that would mean about 1,900 deaths.  This makes radon the second largest contributor to the deadly disease after exposure to tobacco smoke.  Radon is one of the reasons non-smokers are often stricken with a deadly disease usually associated with cigarette use.

“The number of radon-induced lung cancers is about one-half of the deaths due to automobile accidents, and is equal to the combined total of deaths due to accidental poisonings, homocides, drownings and fires,” the panel said in a report.  “In any other situation, this number of deaths would certainly justify a major public health initiative.”

Radon is a colourless, odourless gas released by the decay of uranium in the ground, and is found in almost every region of the country.  Radioactivity emanating from the soil can slip into the basements of homes through foundation cracks and plumbing.  Among the areas with the highest levels are Sudbury, Halifax and Sherbrooke.  The panel estimates that about 2.5 per cent of homes, a total of 175,000, have radon levels above the proposal, and the owners would be advised to take actions to get their levels down.  About 450 schools and 20 hospitals across the country – in all provinces and territories – would need about $560 million in alterations to meet the new standard, according to the panel.

The Canadian standard is 800 becqueral per cubic metre of air.  A Becquerel is a measure of radioactive decay.  The panel recommends the figure be lowered to 200 Bq/cubic meter, the same as in Britain, Sweden and Norway, and new construction in China.  The current Canadian standard was set in 1988, and is considered dated because it was based on the amount of danger posed by radon exposures for uranium miners.  A new study conducted in 2004 in Europe and a second in 2005 based on North American research indicated that radon can be deadly at the lower amounts found in homes.  These studies prompted the governments to review the adequacy of Canada’s standard.

The panel’s proposal is open for public comment until June 22, after which the country’s health authorities will decide whether to adopt it.  Canada’s exposure limit is expected to change because it is more than five times higher than that of the United States, and four times higher than for a new home built in China.  Independent radation experts welcomed the proposal, saying it is overdue.  “We have been actually advocating this for years,” said Reza Moridi, chief scientist at the Radiation Safety Institute of Canada, a national body that promotes radiation safety.  He says the current standard is “far too high.”

In the United States, health authorities have taken aggressive action against radon, and even have a map showing the counties with the highest readings.  A total of 800,000 homes with elevated radon have taken mitigation steps since the mid-1980s in the U.S., at an average cost of about $1,200 (U.S.).  Some U.S. states require testing of private homes when they are sold, an approach the panel said should be considered, along with a requirement that new homes have equipment installed to reduce levels.

“A combination of radon-resistant requirements in new homes and mandatory testing of existing homes could lead to virtually complete compliance with the new Canadian radon guidelines within a decade,” the panel’s report said.

Canadian health authorities currently cannot tell residents where the threat posed by radon is most severe, and are working on a U.S.-style radon map – and outline of parts of the country with the highest risk – and expect to have available in one or two years.  But Mr. Moridi said radon is found everywhere, and the only way to determine for sure whether a building has the problem is through a test.  He said the institute conducted an extensive test of Toronto schools in the early 1990s, and found two were above the U.S. standards.  The institute used U.S. standards because Canadian guidelines were considered too lax to protect the city’s children.

Tests cost about $50 per home.  The most common way to reduce radon entering a home is to install venting pipes through basement floor slabs and seal gaps and cracks in basement walls.  Exposures to radon are worse in winter, when Canadian homes have the least ventilation. 

Although radon is a big danger to non-smokers, it also enhances lung cancer risk among those who smoke.  According to the report, the lifetime risk of lung cancer for a smoker who has only low, outdoor-level exposures to radon is 12 per cent.  That figure jumps to 30 per cent for smokers exposed to radon at the current standard.  The new proposal, however, would reduce the risk to 17 per cent.

© The Globe and Mail, June 14, 2006
Web site:  www.theglobeandmail.com
 

See also: Radon Gas:  A False Alarm?
Back to: Homes A-Z

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