Radon in buildings is a significant health concern recognized by Health Canada and the World Health Organization. According to Health Canada, approximately 16 per cent of all lung cancer deaths are caused by radon; this results in the loss of about 3,200 Canadian lives per year. Next to smoking, radon is the leading cause of lung cancer and the number one cause of lung cancer for non-smokers.
What is Radon Gas?
Radon is a naturally occurring radioactive gas, which can readily enter buildings through foundations with direct soil and rock contact. Radon is present in virtually all of the air we breathe but the problem occurs when too much accumulates inside a building. One common question that invariably comes up is, are there any maps or studies that will tell me what the radon concentration of my building is? Unfortunately, the short answer to that question is no, but, there are resources available that can identify general ‘hot spots’ for radon. However, even within any given ‘hot spot’, you will still find buildings that can have either high and low levels of radon right next door to each other. In areas where the radon potential is very low, you will still find buildings with high radon levels. The only way to know if a building has an elevated radon concentration is to test it.
Testing is a simple process involving the installation of small radon detectors at prescribed locations in a building. A typical residential home would require only a single detector, whereas a large commercial building could require dozens of detectors, depending on the layout and the occupancy patterns within the building. Health Canada recommends that testing only be conducted in areas occupied by an individual for a minimum period of four hours per day. Radon concentrations can vary significantly from day to day and even more so from season to season. Radon testing is most representative of building conditions when conducted over a minimum period of 91 days up to 1 year. The best time of year to test a building is in the fall and winter months when windows are most often closed and radon concentrations tend to be the highest.
Health Canada has set an action level of 200 Becquerels per cubic meter (Bq/m3) in their guidelines for residential and public buildings. This refers to the amount of radiation associated with radon in a building. It is recommended that buildings exceeding this action level have a radon mitigation system installed.
How to fix a radon problem?
There are several ways to mitigate elevated radon levels within buildings which depend on a number of factors. In buildings with robust HVAC systems, mitigation can often be accomplished by ensuring the building is adequately pressurized and ventilated in order to keep radon levels low. In the absence of such a system, installation of a sub-slab depressurization (SSD) system is effective. SSD systems work by exhausting the radon gas from beneath a building to the outdoors before it can enter the building. This is accomplished by inserting PVC piping through the foundation floor slab and connecting it to a fan that is vented outdoors where the radon gas dilutes to low levels very quickly. Soil crawlspaces can be mitigated just as effectively using a well sealed polyethylene membrane over the crawlspace floor, and similar suction system.
Building radon out
Recent changes to the National Building Code and BC Building code prescribe measures to inhibit radon entry and to facilitate potential future mitigation of radon levels in new buildings. These techniques are collectively referred to as Readily Remediated New Construction (RRNC). One aspect of RRNC includes the installation of rough-ins of mitigation systems prior to the slabs of buildings being poured (Photo 1). If post-occupancy radon concentrations are above Health Canada’s guideline of 200 Bq/m³, the complexity of installing an active mitigation system is reduced by the RRNC measures. Building owners are advised to test their new building, and based on the test results either do nothing if results are below 200 Bq/m3, or convert the rough-in to an active mode by installing fans and venting radon gas to the exterior of the building if the results are above 200 Bq/m3.
In Canada there is a growing network of radon professionals to assist with measurement and mitigation of buildings. The Canadian National Radon Proficiency Program (C-NRPP) certifies radon professionals through detailed training courses and testing, and requires frequent professional development to maintain certification. Another source for guidance of radon issues includes the Canadian Association of Radon Scientists and Technologists (CARST). CARST supports research initiatives and technical innovation, develops technical standards, performs government liaison, and serves as a forum for discussion of current radon issues at annual conferences.
Beyond technical innovations, development of standards of practice and improved building codes, the largest challenge with respect to radon continues to be public awareness. It has proven difficult to communicate the risk radon poses to occupant health, in a manner that hits home with Canadians. In an era where we are bombarded by information about emerging health risks by the media, the signal is easily lost. Through the dedicated efforts of the Canadian Cancer Agency, Health Canada, Alberta and BC Lung Association, and public health professionals across Canada, headway is being made. This is an important health issue, and the signal must not get lost. The research linking the radiation associated with radon exposure to lung cancer is undeniable. The process of testing a building is simple. Radon professionals skilled at conducting measurement and mitigation of buildings are eager to support in reducing the risk from radon. Building code professionals are laying the groundwork to eliminate this issue from all new buildings.
David Shearer, B.Sc., LEED AP, is senior project manager at Pinchin West Ltd. in Kelowna, B.C.