What is Radon?
Radon is a radioactive gas that is colourless, odourless and tasteless. It is formed bythe breakdown of uranium, a natural radioactive material found in soil, rock and groundwater.
What is the Risk?
The only known health risk associated with exposure to radon is an increased risk of developing lung cancer. Radon gas and radon progeny in the air can be breathed into the lungs where they break down further and emit “alpha particles” (see figure 1). Alpha particles release small bursts of energy which are absorbed by nearby lung tissue. This results in lung cell death or damage. When lung cells are damaged, they have the potential to result in cancer when they reproduce. Cancers caused by radioactivity are started by chance and not everyone exposed to radon will develop lung cancer. The time between exposure and the onset of the disease is usually many years.
Your risk of developing lung cancer from radon depends on the concentration of radon in the air you breathe and the length of time you are exposed. Until very recently, the estimate of the risk from radon in homes was uncertain. However, two recent independent studies in North America and Europe have confirmed that the lung cancer risk extends downward to radon levels as low as 200 Bq/m 3. (See Glossary, page 47, for definition.)
Radon escapes from the ground into the outdoor air. It is diluted to low concentrations and is not a concern. However, radon that enters an enclosed space, such as a home, can sometimes accumulate to high levels. Radon breaks down to form additional radioactive particles called “progeny” that can contaminate the air you breathe.
Concern in Canada about indoor radon levels began in the mid-1970s. Some homes in communities where uranium ore was either mined or processed were found to have elevated radon concentrations. After this discovery, Health Canada surveyed the radon levels in 14,000 homes in 18 cities across Canada. Also, some smaller communities have been identified by provincial government agencies as having the potential for high radon levels in dwellings.
The majority of homes surveyed showed low concentrations of radon. However, a small but significant minority of homes in some locations were found to have high levels.
For the full guide, refer to the CMHC pdf – “Radon – A Guide for Canadian Homeowners”.