Radon: What You Should Know About This Invisible Health Hazard

The following article is taken directly from BCREA (BC Real Estate Association) article #577 written by By Oana Hyatt, B.Sc.(Pharm), LL.B and was written to inform all BC Realtors. It is a great informative read, which is why we are including it here.

Do you live or work in a building with high radon gas levels? What risks might arise if you do? The following is a summary of what radon is and what you and your clients should consider in this respect. This article is only a starting point; you should also read the British Columbia Financial Services Authority’s (BCFSA) guide for buyers and sellers respecting radon1 and BCREA’s FAQ on radon (BCREA Access login required)2. You may also wish to take BCREA’s Radon for REALTORS® online course.

What Is Radon?

Radon is an odourless, invisible gas that seeps up through the ground and can enter a home through unsealed foundations, cracks in the foundation, gaps in construction materials, and plumbing system components, including sump pumps or drains. Radon gas is also a product of uranium decay. Like uranium, it is radioactive; unlike uranium, it can permeate through rocks or soil, escaping into the air or groundwater. All rocks or soil contain some uranium, but granite, shale, and sandy soils are higher in uranium or radon than clay, limestone, or very moist soil.

Why Is Radon Bad?

Concerns arise when radon gas accumulates in living spaces, as radon is highly carcinogenic. It is the second leading cause of lung cancer, behind smoking, causing over 3,000 deaths per year in Canada – almost eight times more than asbestos.

Where Is Radon Found?

The BC Centre for Disease Control provides a map of certain residential radon testing results across BC,3 but warns that radon gas levels can vary widely from house to house, even in the same neighbourhood.

Cracks in a home’s foundation or bare dirt floors in a crawlspace under the house can provide easy paths for radon to permeate from the soil into living spaces. Due to their improved insulation and airtightness, new homes can accumulate radon gas at even higher levels than older ones. While higher radon levels are found in a home's basement or lower levels, in apartment buildings or towers, radon gas levels can be higher on the top floors due to the “stack effect” or the rise of warmer air.

How Can You Test for Radon?

The radon level in a home can be measured using commercially available and relatively inexpensive radon test kits.4 A proper radon test takes at least 90 days to complete and is often recommended to carry out over the winter when homes are more likely to be sealed up. Opening windows and doors, as folks often do in the warmer months, can vent radon gas, yielding false low results. Shorter-term tests are available but are less accurate.5

How High Is Too High for Radon Gas Levels?

If radon gas is detected in a living space, remediation measures can be undertaken to lower its levels. The World Health Organization recommends a threshold level of 100 Bq/m3 (or about 3 pCi/L) for initiating remediation measures. In the US, threshold levels of 4 pCi/L (or 148 Bq/m3) require remediation. Health Canada recommends remediation within two years for any homes with radon gas levels exceeding 200 Bq/m3, and within one year for any homes with radon gas levels exceeding 600 Bq/m3.

New Construction Standards

As of March 2024, new homes built in BC are required6 to have a radon gas vent pipe installed to allow the venting of soil gases from the ground beneath the basement or crawlspace to the roof or exterior of the building. This pipe is called a passive sub-slab depressurization system. While often effective at reducing high radon concentrations, a passive sub-slab depressurization system may not bring those concentrations below the guideline levels. The British Columbia Building Code does not require builders to install a fan system in the pipe to turn this into an active sub-slab depressurization system. However, homeowners may wish to install a fan system to reach levels below the recommended threshold.

Retrofitting Older Homes

Older homes can be retrofitted with radon gas mitigation systems that can range from relatively passive methods, such as sealing porous concrete and repairing any cracks in basements or crawlspaces, to more active and costly methods, such as installing a heat recovery ventilation fan in the basement or the whole home or installing a passive or active sub-slab depressurization system like those required in new home construction.

Buying or Selling a Home and Disclosure of Radon Test Results

Property owners are not required to conduct radon testing of their properties. Still, sellers are encouraged to disclose in writing (for example, in the Property Disclosure Statement) whether they have carried out any radon testing and, if so, what the results were.

Since April 2020, Property Disclosure Statements have included the following questions for sellers:

V. To the best of your knowledge, have the Premises been tested for radon?
(i) If yes, when was the most recent test completed and what was the most recent level of radon detected:
Level:_____________ □bq/m3 □pCi/L on ______________________ Date of test (DD/MM/YYYY)

W. Is there a radon mitigation system on the Premises?
(i) If yes, are you aware of any problems or deficiencies with the radon mitigation system?

Under BCFSA guidance7 implemented in September 2019, sellers’ agents (or landlords’ agents) who learn that the home has been tested for radon and radon levels exceeded 200 Bq/m3 have a separate obligation from that of the sellers to disclose this to potential buyers or tenants as BCFSA considers such levels to constitute material latent defects.

If purchasing a property where a seller has disclosed prior radon testing results, buyers may consider whether those results are relatively recent or whether the seller has renovated the property since the testing was done, as such work may have impacted the radon gas levels in the home. If the seller has disclosed test results exceeding 200 Bq/m3, buyers may wish to consider options such as a price reduction, a holdback for remediation by a radon professional, and / or looking at other homes.

If purchasing a property where a seller has not disclosed prior radon testing results, most buyers will not be able to conduct adequate pre-purchase inspections for radon gas, given the typical subject removal period in a residential home purchase is much shorter than the 90+ days required for accurate radon testing. Buyers may wish to ask their home inspectors or other qualified professionals for their views on potential radon gas ingress routes into the home and the possibility and cost of installing remediation measures. Buyers may also wish to consider options such as a price reduction or a holdback for testing and possible remediation by a radon professional.

What You Should Know

Real estate professionals should be familiar with the basics of radon gas and their obligation to disclose any known test results exceeding 200 Bq/m3 and should not hesitate to refer their clients to the appropriate professionals for advice regarding radon gas remediation measures and the new construction standards in BC.