Radon in the Indoor Environment

​Why is Radon a Health Issue?

Radon is a colorless and odourless radioactive gas that is a product of the radioactive decomposition of uranium. Radon is a naturally occurring substance, but when it is in an enclosed space, it can accumulate to concentrations that pose a health risk. Exposure to high concentrations of radon has been linked to an increased risk of developing lung cancer, and radon gas exposure is the second leading cause of lung cancer after smoking. A number of studies in recent years have shown that a significant number of Canadians are living in homes with radon levels above the current Canadian guidelines. In 2012, Health Canada released the Cross-Canada Survey of Radon Concentrations in Homes final report indicating that 6.9% of Canadians are living in homes with radon levels above the guidelines. Early results from a 2016 Calgary study being undertaken by researchers is suggesting that as many as one and five homes are over the maximum acceptable limit.

Radon Guidelines

Health Canada recommends that remedial measures be undertaken wherever the average radon concentration exceeds 200 Bq/m3 in the normal occupancy area. The World Health Organization (WHO) recommends a lower annual average concentration of 100 Bq/m3 as a threshold.

Measuring Radon Levels

Radon tends to be heavier than air and given that most of the radon in homes is from the soil upon which the building stands, Health Canada has recommended that radon testing be done below the third floor. The concentrations of radon in the indoor environment can vary significantly over time. For this reason, long-term measurements typically of 3-12 months are recommended. Testing for radon for less than three months is not recommended.  Long-term radon measurements can be done with an alpha track detector, an electret ion chamber, or a digital detector.

In an alpha track detector, the alpha particles from radon and its decay products strike a special plastic or film, creating damage tracks and at the end of the testing period, the film is analyzed by a laboratory. In an electret ion chamber, there is an electrostatically charged disk detector, which experiences a reduction in charge as a result of the ionization from the decay of radon. The electret can be read in the home using a special device or sent to a laboratory for analysis. A digital detector uses an ion chamber, and after an initial measurement period, the device will display the average radon concentration continuously.

Reducing Radon Concentrations

Radon levels in a building can be reduced by:

• Increasing under-floor ventilation
• Sealing floors and walls to prevent the passage of radon
• Improving the ventilation of the house
• Installing a radon sump system in the basement or under a floor

A certified radon mitigation contractor can be found through the Canadian National Radon Proficiency Program or the Canadian Association of Radon Scientists and Technologists. Further information on strategies for radon reduction can be found in the Health Canada Radon Reduction Guide for Canadians.