Exposure to high levels of radon increases the risk of developing lung cancer. This relationship has prompted concern that radon levels in some Canadian homes may pose a health risk.
Radon is a colourless, odourless, radioactive gas that occurs naturally in the environment. It comes from the natural breakdown of uranium in soils and rocks.
The Health Effects of Radon
In the open air, the amount of radon gas is very small and it does not pose a health risk. However, in some confined spaces like basements and underground mines, radon gas can accumulate to relatively high levels and can become a health hazard. Exposure to high levels of radon has been associated with an increased risk of lung cancer, depending on the length of time you are exposed.
Because it is radioactive, radon decays. As it decays, it produces decay products, sometimes called "radon daughters" or "radon progeny." Two of these progeny, polonium-218 and polonium-214, decay rapidly themselves, and emit alpha particles. When alpha particles hit an object, the energy in them is absorbed by the surface of the object. Human skin is thick enough not to be affected, but if you breathe in alpha particles, they can damage bronchial and lung tissue, and can lead to lung cancer.
Studies of the incidence of lung cancer among uranium miners showed a correlation between radon exposure and deaths from lung cancer. Until recently, there was no evidence of a direct link between radon levels in the home and lung cancer. However, recently, two independent scientific studies in Europe and North America showed that the lung cancer risks extend to levels of radon found in some homes.
Radon in the Home
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 walls and floors, 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.
A survey conducted by Health Canada in the 1970s showed that radon levels in certain Canadian cities were higher than in others. However, these same studies showed that it is impossible to predict whether any one house will have a high level of radon. Factors such as the location of the house and its relation to the prevailing wind may be just as important as the source of the radon.
Measuring Radon Levels in the Home
Commercial services are available to homeowners who wish to measure radon levels in their homes. Radon is measured in units called "becquerels per cubic metre." The most popular radon detectors are the charcoal canister, the electrets and the alpha track detector. These devices are exposed to the air in a home for a specified period of time, and then sent to a laboratory for analysis. There are other techniques for testing radon levels, but they require a trained operator and are more expensive.
Minimizing Your Risk
Health Canada's studies show that high radon levels are not widespread in Canadian homes. However it is difficult to predict the level in any one home. If you are concerned about exposure to radon gas in your home, you might consider testing the levels, and/or taking the following steps to reduce it:
Seal cracks and openings in walls and floors, and around pipes and drains; and
Ventilate the sub-floor of basement floors.
Health Canada's Role
Health Canada has taken a number of steps to protect Canadians from the potential dangers of radon gas. These include evaluating measurement techniques, conducting research into effects of radon exposure and developing guidelines.
In 1988, Health Canada with the participation of provinces and territories developed a radon guideline which was approved by the federal and provincial ministers of health. This guideline recommends that remedial action be taken when the level of radon in a home is found to exceed 800 becquerels per cubic metre as the annual average concentration in a normal living area. Health Canada's guideline for radon has always been based on the best available scientific evidence of health risk. After considering the new evidence about radon and the risk of lung cancer, Health Canada is proposing a revised guideline for radon gas levels in indoor air. The proposed new guideline, which was developed in partnership with the Provinces and Territories, is 200 becquerels per cubic metre. This is four times more stringent than the current guideline of 800 becquerels per cubic metre.
Health Canada is collecting feedback on the proposed new guideline from interested stakeholders and the general public. Following the consultations a final guideline will be established. Health Canada also continues to work with the Provinces and Territories to help raise awareness among homeowners and assist them in finding solutions to lower the levels of radon in their homes. Because there is some risk at any level, homeowners may want to reduce their exposure to radon, regardless of levels tested.
Health Canada is collecting feedback on the proposed new guideline from interested stakeholders and the general public. A final report on the consultations and recommended guideline will follow.
Need More Info?
Contact: Radiation Protection Bureau, Health Canada 2nd Floor, Radiation Protection Building 775 Brookfield Road Ottawa, ON K1A 1C1
Health Canada and the Canada Mortgage and Housing Corporation have produced a booklet called Radon - A Guide for Canadian Homeowners. For a copy, visit the Canada Mortgage and Housing Corporation Web site and search for Radon, or call 1-800-668-2642.
For information about testing for radon levels, please check your local Yellow Pages for "Home Inspectors".
For more information on occupational concerns, go to The Canadian Centre for Occupational Health and Safety - What is Radon.