Radon Gas

Health Canada is poised to tighten up guidelines for radon gas levels in indoor air, to a level four times more stringent than current guidelines. It could mean that radon testing will become mandatory in future real estate transactions, and that building codes for new homes will be upgraded.

Critics say that Canada should have adopted the stricter guidelines in the 1980s, when the United States and other countries around the world set their radon guidelines. But Health Canada says that "until recently, there was no evidence providing a direct link between radon levels in the home and lung cancer." The ministry says that, "However, in 2005, two independent scientific studies performed in Europe and North America showed that lung cancer risks extend to levels of radon found in some homes depending on the length of time an individual is exposed to it."

Canada's current guideline of 800 becquerels per cubic metre is the second highest allowed in the world. The new proposal would set the level at 200 becquerels, which is the same as the United Kingdom, Australia, Norway, Spain and several other companies. The toughest guideline is in the United States, at 150 becquerels.

Fergal Nolan, president of the Radiation Safety Institute of Canada, told media outlets that he asked Health Canada to match the U.S. guidelines back in 1988, but that the ministry didn't take the threat seriously.

However, Health Canada says there was no conclusive evidence before 2004 that radon levels in buildings were directly linked to lung cancer. Now, it acknowledges that radon can pose a serious health risk.

Radon is an odourless radioactive gas that occurs naturally in the environment. It is caused by the natural breakdown of uranium in soils and rocks. In the open air it does not pose a health risk, but in an enclosed space such as a mine or a basement, breathing in radon decay products can lead to lung cancer.

The Health Canada report estimates that lung cancers from radon exposure account for about 10 per cent of all lung cancers, second only behind smoking. It says an estimated 1,600 lung cancer deaths in 2000 can be attributed to radon. "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, homicides, drownings and fires," says the Health Canada report. "In any other situation, this number of deaths would certainly justify a major public health initiative."

Radon can seep into a house through dirt floors, cracks in concrete walls and floors, sumps, basement drains, and through concrete block walls. Radon levels are higher in some geographic areas than others, and Health Canada is current working on a mapping system to identify the hottest radon zones.

However, predicting which houses have radon and which ones don't is difficult. "Factors such as the location of the house and its relation to the prevailing wind may be just an important as the source of the radon," says the Health Canada report. Radon levels can vary from season to season, with the highest levels usually recorded during winter.

One estimate says that about 175,000 Canadian homes, or almost three per cent of single-family homes, have radon levels above the proposed new guideline of 200 becquerels, and will need to be repaired to ensure the safety of its occupants.

In discussing the implementation of the proposed guidelines, the Health Canada report says several Canadian companies currently offer radon testing services, and the average cost is about $50 per test. It says that a national certification program should be considered to ensure that testing standards are determined and enforced.

For houses that require work, the average "mitigation" cost would be about $1,200 per house, says the report.

"Active soil depressurization has been found to be the most effective and reliable radon reduction technique in existing homes," says the report. "This method involves installing a vent pipe through the basement floor slab or connecting it to the foundation drain tiles through the sump. A fan which runs continuously is connected to the vent pipe. This reverses the air pressure difference between the house and the soil, so that air flows from the house into the soil, preventing soil gas entry, and reducing concentrations of soil gas, including radon, next to the foundation."

The report says open sumps should be fitted with airtight covers with special traps that allow water to drain, but prevent radon from entering the basement. Major gaps in the basement floor or in the top of foundation and interior load-bearing walls should be sealed, as should minor cracks in foundation walls and floors. Other gaps around utility penetrations should be sealed. Exposed soil in a crawlspace should be covered by a barrier with sealed edges and joints, says the report.

"What is required for testing services also applies in large measure to builders and contractors providing radon mitigation services. Standards and guidelines need to be developed and this includes revisions to national, provincial, and local building codes. These guidelines could be more rigorously enforced in radon-prone areas," says the report. "The approach here is not to over-regulate the building industry, but to provide it with the knowledge and tools needed to play an effective role in radon mitigation."

The report says that "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."

For more information about radon in the home, download Radon: A Guide for Canadian Homeowners, produced jointly by Canada Mortgage and Housing Corp. and Health Canada.

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