Radon Gas Exposure
It has been estimated that 1,900 deaths per year in Canada are attributable to radon. Estimates of 21,000 people in the US die each year from excessive exposure to a naturally occurring radioactive gas called radon (US Environmental Protection Agency). Radon is the leading cause of lung cancer amongst non-smokers. Only tobacco smoke provides a quicker route to lung cancer.
What is Radon? -- Radon is a tasteless, odourless and colourless radionuclear gas found in rock, soil and groundwater due to the natural breakdown or radioactive decay of, a natural element, uranium. Radon has been generated and released from uranium since the earth was formed. Radon gas is present to some extent everywhere. Each radioactive element decays at a characteristic rate known as a half-life. As the material gives off radiation it is transformed into a different element. Since the half-life of uranium-238 is about 4 and a half billion years it, and, its decay products, will linger forever as far as we are concerned.
CMHC (Canada Mortgage & Housing Corporation) states that concerns 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.
How does it enter a home? -- Radon readily seeps from the earth and rock beneath a home through tiny cracks and openings in the floors, foundation and basement walls. The concentration in a home depends on source strength, soil characteristics, mechanical systems in the house, occupants’ habits, the weather, and, many other factors. A low radon gas level in one home does not necessarily mean that homes nearby are okay. In addition, radon varies significantly day-to-day and over the course of months. Significant concentrations can also be released into the home by way of well water. This can occur during activities such as showers or dish washing. To a lesser extent it can also be present in building materials and in fossil fuels that may be burned in the house. 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.
How serious can radon be? -- The health risks associated with exposures to high concentrations of radon gas were first revealed with the experiences of uranium miners over the past few decades. A number of epidemiological studies of miners in the US, Canada, Germany, Czechoslovakia and elsewhere found a correlation between long term exposure to high levels of radon and radon daughters, and the incidence of lung cancer (Health Physics -- 11/85). Long-term exposure to radon increases the risk of developing lung cancer. Radon gas is the number two cause of lung cancer resulting in as many as 30,000 deaths per year (US National Cancer Institute). The health risks to humans show no immediate symptoms however about 10% of all lung cancer deaths are estimated to be radon related. Smokers are at higher risk of developing radon-induced lung cancer. Accumulation of radon in an enclosed area, such as a home, can be very hazardous to your health.
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 level to see if it exceeds Canada’s guideline for exposure to radon in indoor air. The guideline, which was updated in 2007, 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; and, ventilating the sub-floor of basement floors.
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. Health Canada’s guideline for exposure to radon has always been based on the best available scientific evidence of health risk. In 1988, a guideline of 800 becquerels per cubic metre was established in Canada. After considering new evidence about radon and the risk of lung cancer, Health Canada worked in partnership with the provinces and territories to develop a proposed new guideline of 200 becquerels per cubic metre, which is four times more stringent than the previous one. Following a series of consultations with interested stakeholders and the general public, the new guideline was finalized in June 2007.
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