What is radon?
Radon is a colourless, odourless gas that is widely present in the earth's surface as a radioactive breakdown of uranium. Uranium occurs naturally and can be found in small amounts in soil, water and air. Once formed, radon gas moves up through the surrounding soil under homes and buildings, seeping in through cracks in floors, walls, joints, foundations, as well as, through sumps pumps, basement drains and other openings.

Radon is not usually a problem outdoors as the air rapidly dilutes it to lower levels; however, inside radon can become trapped in the home or building, where it can build up. As a result, unsafe levels of radon could accumulate in poorly ventilated homes and buildings.

What are the health effects from exposure to radon?
Health Canada published a report which stated that exposure to elevated levels of radon has contributed to the burden of disease, namely, the incidence of lung cancer in Canada. Between 2009 and 2010, Health Canada conducted a cross-country survey which tested radon levels in the home. The study determined that approximately 7% of Canadians are living in homes with radon levels above the guideline.

Radon gas breaks down quickly, releasing tiny radioactive particles (radon "daughters") which, once breathed in can become trapped in the lungs. Once in the lungs, radon breaks down further, releasing energy which damages lung tissue. Over an extended period of time, exposure to radon can cause lung damage, leading to an increased risk of lung cancer.

How much radon is too much?
The benchmark for adverse health effects from exposure to radon was 800 Bq/m3. (Bq or becquerels are used to measure radioactive concentration.) In 2007, this benchmark was lowered by Health Canada from 800 Bq/m3 to 200 Bq/m3 to be more health protective of long term exposure to radon gas.

Who is at risk?
Uranium occurs naturally in the environment. As a result, radon levels vary across the country but elevated levels can occur anywhere. These levels also fluctuate. Depending on the weather, humidity, the structure, or the time of year, radon levels will either be higher or lower in a home or building.

Although there are hot spots (certain geographical areas where radon is more likely to be found), it is possible for one home or building to contain a buildup of radon, without radon gas affecting the neighbouring property. Radon can enter both old and new homes and buildings, those that are well-sealed or drafty, and those with and without basements.

Radon gas is known to increase the risk of lung cancer. Current research states that there are no safe levels of accumulated radon in a home or building. As the adverse health effect of radon exposure adds up over time, the disease may take many years to appear.

Compared to the rest of the population, smokers are at an even greater increased risk of developing lung cancer, if exposed to elevated levels of radon.

Managing the health hazard
The first step to managing the risk of radon gas begins with testing the home or building.
A long-term test (from 3 to 12 months) is the only method that will determine a precise average radon level in the home or building. Long-term tests are recommended by Health Canada, and the adverse level for mitigation measures is based on this method. (Short-term tests are available [2 to 7 days], if the results approaches or exceeds the level of 200 Bq/m3, the recommendation is to follow-up with a long- term test.)

If there is a risk of radon gas accumulation, there are mitigation measures that can be put in place to reduce the buildup. In order to stop radon from entering your home or building, mitigation measures must involve more than just sealing joints and cracks. Radon could enter from a floor drain or through some other unknown/unseen opening.

Health Canada recommends using only a qualified radon mitigation contractor to help prevent radon from entering your home, and also recommends asking for accreditation references. A qualified radon professional is accredited by the National Radon Proficiency Program (NRRP) or the National Radon Safety Board (NRSB).

For further information, please see the website links below. For further clarification of this fact sheet, please contact the Environmental Response Team, Healthy Environments at 416-392-7685.

Website links
Health Canada
National Radon Proficiency Program (NRRP) 
National Radon Safety Board (NRSB) 
The Lung Association


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