Should I have my home mitigated?
Any level above 100 Bq/m3 represents a statistically significant increase in the lifetime relative risk of lung cancer for those being exposed chronically to it. Indeed, the WHO deferred to the amount of radon where a statistically observable increase in lifetime risk of lung cancer is clear and significant – this is 100 Bq/m3. Health Canada set our “maximum exposure limit” reference level at twice this value, with the view that double where we start to see an increase in risk is truly unacceptable.
To ensure that you are protected to where there is no significant increase in risk (as science and medicine understand radon), aim to get your home, school and work environment below 100 Bq/m3. It is important to remember that the 200 Bq/m3 level is set by Health Canada as a maximum acceptable reference level. Health Canada’s advice is to aim for as low as reasonably achievable. Your body cannot distinguish between 199, 200 and 201 Bq/m3 of radon, and being slightly under or over that number is meaningless to your long term health. Our advice if your home is at or near 200 Bq/m3 is to evaluate your relative risk and exposure by asking yourself the following questions:
- Are there babies, kids or teens in the home? If yes, consider mitigating, as young people are at a much higher risk from the negative impact of radon compared to those of older ages (65+).
- Does anyone work from home or spend most of there days at home? If yes, then consider mitigating, as those individuals are breathing the home’s air for a lot longer than a person leaving for large parts of the day for school or work.
- Does anyone in the home have a family history of cancer? If yes, consider mitigating, as some families carry altered genes that make them more susceptible to cancer following exposure to radiation.
- Is anyone in the home a current or former smoker? If yes, consider mitigating. The risk of lung cancer from radon is ‘synergistic’ with the risk of smoking. For example, ‘1 unit’ of risk from smoking plus ‘1 unit’ of risk from radon does not equal 2, rather it is a case of 1+1=17. Smokers (current or former) are much more at risk from radon, and so should protect themselves from radon even if still actively smoking to reduce their chances of cancer in the future.
- Is anyone in the home exposed to other lung cancer risk factors? If yes, consider mitigating. In addition to smoking (described above), folks who work with or who are exposed often to metal dust (metallurgists, jewellers, machinists, black smithery, etc.), leather dust, gasoline or diesel fumes (mechanics, firefighters, etc.), asbestos and heavy air pollution should also aim to reduce their exposure to radon as much as possible.
Active Soil Depressurization
Sub-slab depressurization (also called active soil depressurization) is the most effective and reliable radon reduction technique. It is also the most common method used by C-NRPP certified professionals.
This method involves installing a pipe through the foundation floor slab and attaching a fan that runs continuously to draw the radon gas from below the home and release it into the outdoors where it is quickly diluted. This system also reverses the air pressure difference between the house and soil, reducing the amount of radon that is drawn into the home through the foundation. One, or sometimes multiple, suction points are inserted through the floor slab into the crushed rock or soil underneath to effectively reduce the radon level in the home.
The sub-slab depressurization pipe is vented at the ground level of the home. The fan can be placed in the basement or an area outside of the living space such as in a garage. If the fan is placed inside the living space of the home, it is usually vented sideways through the rim joist at ground level, with the fan close to the exhaust location. When the fan is placed outside of the living space (e.g. garage) then it is typically vented upwards above the roof. When any active depressurization system is installed, it is recommended to make sure that its operation does not cause back-drafting of combustion appliances such as a furnace, water heater, fireplace, or wood stove in the home. Backdrafting can happen when a room with a combustion appliance is depressurized so much that smoke and combustion gases spilling into the home instead of venting outdoors. Backdraft testing may be done by a trained radon-reduction specialist or a heating contractor.
For more information on mitigation, please visit: the Health Canada website