The association representing Canada's homebuilders is claiming that Ottawa's first-ever set of guidelines to reduce cancer-causing radon gas in basements is itself dangerous.

"This standard is being rushed to publication while there remain many unresolved issues which could result in severe and immediate health problems, and even death," Kevin Lee, president of the Canadian Home Builders' Association (CHBA), warned Canada's health minister last August.

"Moving forward with the publication of the standard in its present state – before necessary research has been completed, and without addressing serious technical issues – poses a significant risk to the health of Canadians and the integrity of their homes."

Kevin Lee, CEO of the Canadian Home Builders' Association, warned Canada's health minister last August about alleged problems with a new standard on mitigating radon gas levels in Canadian homes. (twitter.com)

Lee was writing to warn then-Health Minister Jane Philpott against the pending publication of a guidance document on how to mitigate radon gas content in low-rise residential buildings.

Radon is a naturally-occurring radioactive gas that can seep into basements and well-water. It has been blamed for 16 per cent of lung cancer deaths in Canada.

Since 2014, Health Canada has led a radon-mitigation committee of 26 regulators, health authorities and businesses – including the CHBA – in the work of drafting the first national standard for reducing the threat of radon gas in homes.

The standard was published late last year without any changes, despite the fierce objections of the homebuilders group.

'Immediate action'

"Your immediate action is required to ensure that Canadians are not positioned to rely on a flawed standard – a standard that could put their health, lives and homes at risk," Lee told Philpott.

CBC News obtained a copy of Lee's letter, and related documents, under the Access to Information Act. The letter was also copied to three other federal ministers.

A spokesman for the CHBA confirmed to CBC News that the association still objects to the new standards, arguing that the solutions themselves pose risks.

"CHBA remains concerned about the unresolved issues, such as the risks of back-drafting from combustion appliances (having toxic gases released into the home) and the freezing of foundations and radon stacks (pipes that vent soil gases out through the home's roof)," said David Foster, the group's director of communications.

None of the outstanding issues that you have raised poses significant risks to the health, well-being, or the property of Canadians. - Health Canada official responding to a homebuilder group's objections to new radon gas guidelines

Mitigation measures in the new standard include venting systems designed to remove radon gas from basements. The CHBA argues that those vents could become clogged in cold weather and that the venting itself could have unwanted effects — such as a dangerous buildup of furnace gases.

A briefing note for Philpott on the issue notes that the CHBA was the only member of the committee to object to the publication of the new standard. It calls the group's concerns "unfounded."

"None of the outstanding issues that you have raised poses significant risks to the health, well-being, or the property of Canadians," Tim Singer, a director-general at Health Canada, wrote to Lee on September.

Then-health minister Jane Philpott's officials pushed back against the homebuilders' objections and published the radon guidance document late last year. (Adrian Wyld/Canadian Press)

"Furthermore, delaying publication of this standard leaves Canadians in the precarious situation of having no standard for radon mitigation in existing buildings, or having to adopt a standard from another country, which would not adequately identify and address Canadian requirements."

A spokesman for Health Canada defended the public posting of the document.

"At no point would the committee have put forward guidance that would have put Canadians at risk," Eric Morrissette said in an email.

"We recognize that the guidance in the standard will need to evolve as the science does. This document will be updated to reflect new research currently being conducted … Before this standard was published in December 2017, there was no Canadian national standard for mitigating radon levels in homes and buildings."

The internal Health Canada documents also note that the new standard includes diagnostic tests to ensure venting systems are working as required, so that problems can be identified early.

Guidance only

Morrissette added that the document provides guidance only.

"It is not a stand-alone regulatory document and is not enforceable on its own unless it is embedded in the national or provincial Building Code, neither of which is under the authority of Health Canada."

Radon gas – odourless and colourless – is the second most frequent cause of lung cancer, after cigarette smoking. In 1985, it was found to be a health risk in homes, seeping through cracks in foundations and walls, or through gaps around pipes. Radon also can enter the water supply, especially well-water.

Modern airtight buildings that lack proper ventilation can allow radon to accumulate.

The CHBA says it represents 8,500 companies in Canada, including builders, renovators, trade contractors and product manufacturers.

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