Radon

Radon is a radioactive gas that occurs naturally in the environment. It comes from the natural breakdown of uranium in soils and rocks. In the open air, the amount of radon gas is very small and does not pose a health risk. However, in some confined spaces like basements and underground mines, radon can accumulate to relatively high levels and become a health hazard. The only known risk associated with radon is an increased possibility of developing lung cancer. The level of risk depends on the concentration of radon in the air you breathe and the length of time you are exposed to it. After smoking, radon is the next leading cause of lung cancer.

Radon gas can move through small spaces in the soil and rock upon which a house is built. It can seep into a home through dirt floors, cracks in concrete, sumps, joints, basement drains, under the furnace base and jack posts if the base is buried in the floor. Concrete-block walls are particularly porous to radon and radon trapped in water from wells can be released into the air when the water is used.

Health Canada, in partnership with the Provinces and Territories, has approved a revised guideline for radon gas levels in indoor air that is four times more stringent than the previous guideline for Canada. The guideline recommends that:

• Remedial measures be taken in a dwelling whenever the average annual radon concentration in the normal occupancy area exceeds 200 becquerels per cubic meter. 
• The higher the radon concentration, the sooner remedial measures should be taken. 
• When remedial action is taken, the radon level should be reduced to a value as low as practicable (i.e., reduced as much as possible using methods that are cost-effective).
• The construction of new dwellings should employ techniques that will minimize radon entry and will facilitate post-construction radon removal, should this subsequently prove necessary.

Because there is some risk at any level, homeowners may want to reduce their exposure to radon, regardless of levels tested. Some of the steps you can take to reduce radon levels in your home include:

• Renovating existing basement floors, particularly earth floors.
• Sealing cracks and openings in walls and floors, and around pipes and drains.
• Ventilating the sub-floor of basement floors.

This is a guideline. There are no legislated allowable limits for radon in dwellings. There are limits on radon in nuclear facilities, but these form part of the radiation protection regulations generally applicable for nuclear radiation workers.

To the best of current scientific knowledge, any level of radiation may cause cancer. In that sense there is no “safe” limit for radon. The guidelines for radon are, and have been, based on calculations of the risk presented by a given level of radon gas. Hence radon at the revised guideline (200 Bq/m3) presents one-quarter of the risk of exposure to radon at a concentration of 800 Bq/m3.

The lower guideline has been adopted because of new epidemiological studies indicating that the risk from radon exposures is greater than previously believed. Further, it will bring Canada into line with the guidelines generally adopted internationally.

Related Documents and Links

Canadian Radon Guideline

Health Canada Measurement Protocol

Providers of Radon Monitoring Services

Radon Q & A

CMHC - Radon - A Guide for Canadian Homeowners

Health Canada