What is the risk?
Radon, a radioactive, colourless and odourless gas, is now the number one cause of lung cancer among non-smokers and the second leading cause of lung cancer overall, according to the United States Environmental Protection Agency (EPA). Exposure to the agent accounts for about 21,000 lung cancer deaths annually.
In 2012, Health Canada published the results of a two-year study, Cross-Canada Survey of Radon Concentrations in Homes. According to the report, “6.9% of Canadian homes have radon levels above the current radon guideline of 200 Becquerel’s per cubic meter of air (Bq/m3.)”1 With a population of 35 million, and assuming a four person family per home, this means we have approximately 2.4 million Canadians who are currently overexposed to radon.
Radon is a naturally occurring by-product, created by the radioactive decay of uranium in Canada’s rock and soils. A process known as “stack effect” (the same force that draws hot smoke up a chimney) draws radon gas into buildings from rock and soils near building foundations. Once the radon has entered a building, it concentrates in the air and is inhaled deeply into the lungs. This internal dose of radiation increases the risk of lung cancer for building occupants.
How is radon tested?
The Radon Potential map of Canada can help identify high risk radon areas. A map, however, can only reveal so much. Expert studies demonstrate that it is inaccurate and unsafe to predict a building’s indoor radon concentration based purely on geographic location.
Radon concentrations can vary significantly as a result of a complex group of variables, such as source strength, building type, ventilation type, season, climate, and occupants’ lifestyles. Thus, the only way to know about a building’s radon concentrations is to perform direct tests. All buildings must be tested, since they contribute to Canadians’ overall exposure to radon.
Practitioners can test the air by deploying a small canister in the lowest lived-in level of the building (defined as an area occupied for 4 hours or more) for 24 hours to one year. Health Canada recommends sample durations of three to 12 months, and never less than one month. Long sample durations are necessary to compensate for fluctuations in radon concentrations and to provide an accurate assessment of exposure for building occupants. Health Canada concludes that tests of less than two days should not be used to determine mitigation requirements and should ultimately be followed up with a long-term test. Short-term tests are only appropriate when practitioners are trying to determine if mitigation measures have been successful.
If elevated concentrations of radon are present in the building, mitigation measures should be implemented within one to two years.
What can home and building owners do to reduce radon?
The most common method of mitigation is sub-slab depressurization. This involves coring holes through the basement floor slab, then installing piping and an air tight in-line fan. The small fan provides a slight negative air pressure under the floor slab, preventing the infiltration of radon and expelling any collected gas outdoors where it can dissipate. In an unfinished residential basement, these systems typically cost from $2,500 to $4,000 to install.
Ontario’s Tarion, a corporation that administers the Ontario New Homes Warranties Plan Act, has made radon mitigation a warrantable claim in new homes. This addresses the Ontario Building Code’s requirements for radon resistant construction and mitigation. Both Health Canada and Tarion stipulate that radon measurement specialists must perform long-term testing. Measurement providers and mitigation contractors must meet an acceptable level of expertise. Professionals can prove that they possess the requisite skills and knowledge for radon testing, assessment and mitigation with the National Radon Safety Board / Canadian National Environmental Health Association NRSB / C-NRPP designation.
Bruce Decker EP, C.E.T., ROHT, BSSO is a C-NRPP certified measurement provider and senior project manager and technical advisor at Safetech Environmental Ltd.