Radon: Frequently Asked Questions

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Protecting your family's health from the risk of radon exposure starts with learning more.

Q. What is radon?

A. Radon is a radioactive gas that is formed naturally by the breakdown of uranium in soil, rock and water. As a gas, radon is slowly released from the ground, water, and some building materials that contain very small amounts of uranium, such as concrete, bricks, tiles and gyproc. Radon gas breaks down further to form additional radioactive particles called radon daughters, or "progeny" that can be breathed into the lungs.

Radon cannot be detected by the senses, i.e., it is colourless, odourless and tasteless; however, it can be detected with special instruments. When radon is released from the ground outside it mixes with fresh air and gets diluted resulting in concentrations too low to be of concern. However, when radon enters an enclosed space, such as a house or basement, it can accumulate to high concentrations and become a health risk.

Radon concentrations fluctuate seasonally, but are usually higher in winter than in summer, and are usually higher at night than during the day. This is because the sealing of buildings (to conserve energy) and the closing of doors and windows (at bedtime), reduce the intake of outdoor air and allow the build-up of radon.

Q. What is the Canadian guideline for radon in indoor air?

A. The Canadian guideline for radon in indoor air provides Canadians with guidance on when remedial action should be taken to reduce radon levels. The Canadian Guideline is as follows:

"Remedial measures should be undertaken in a dwelling whenever the average annual radon concentration exceeds 200 becquerels per cubic metre (200 Bq/m³) in the normal occupancy area. The higher the radon concentration, the sooner remedial measures should be undertaken. When remedial action is taken, the radon levels should be reduced to a value as low as practicable. 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."

Q. Why did Health Canada announced in June 2007 a lowering of the guidelines for acceptable levels of radon in the house from 800 to 200 Bq/m³?

A. Health Canada's previous guideline had been in place since 1988. The original guideline was based on estimates of lung cancer risk from studies of underground uranium miners exposed to very high levels of radon. Uncertainty existed with the projection of lung cancer risk from occupational radon exposure to the public for residential exposures.

Recent scientific studies have conclusively linked the risk of developing lung cancer to levels of radon found in some houses. These studies prompted the federal government to collaborate with provincial and territorial governments to review the federal radon guidelines in 2005. Following a risk assessment and a public consultation, the revised guideline was approved by the Federal Provincial Territorial Radiation Protection Committee in October 2006. Our new guideline of 200 Bq/m³ makes Canada's guidelines lower than or equal to most every other major industrialized country.

Q. What is a bequerel?

The becquerel is the unit scientists use to measure the number of radioactive decays of radon atoms. One becquerel corresponds to one disintegration per second. Higher numbers of becquerels means higher levels of radon gas in the air.

Q. What is the difference between becquerels per cubic meter (Bq/m³) and picocuries per litre (pCi/L)?

A. The concentration of radon in the air is measured in units of becquerels per cubic meter (Bq/m³) or picocuries per litre (pCi/L). Both these units are measurements of radioactive concentration. The international community uses the becquerel per cubic meter of air (Bq/³), while the USA uses the picocurie per litre to measure radon. One pCi/L is equivalent to 37 Bq/m³.

Q. What is Health Canada's reaction to the World Health Organization's (WHO) proposal for radon reference levels to be set at 100 Bq/m³?

A. Canada's radon guideline is well within the range recommended by the WHO. The WHO's new annual recommended reference level is 100 Bq/m³, with an upper limit that should not exceed 300 Bq/ m³. Health Canada, in consultation with the Federal Provincial Territorial Radiation Protection Committee (FPTRPC) set a guideline (also known as a reference level) of 200 Bq/m³ for annual radon concentrations.

Health Canada and the FPTRPC have reviewed and discussed the WHO's recommendations and at this time have decided not to lower the Canadian radon guideline as it falls within the recommended range of 100 to 300 Bq/ m³.

Q. Should Canadians be concerned about the WHO proposal?

A. The Government of Canada is keenly aware of the important link between health and the environment, and through initiatives such as the Clean Air Agenda, is developing and implementing an effective radon program. This program is designed to make tangible improvements in the health of Canadians by reducing the incidence of lung cancer. Health Canada encourages Canadians to test their houses for radon and to take steps to reduce the radon levels if they are above the Canadian guideline of 200 Bq/m³.

Q. What are the reference levels used by the United States and European Union?

A. The reference level in the USA is 150 Bq/m³. Reference levels for individual countries in the EU range from 200 to 400 Bq/m³.

Q. How can radon affect my health?

A. Radon gas and radon progeny in the air can be breathed into the lungs where they breakdown further and emit "alpha particles". 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.

The only known health risk associated with exposure to high levels of radon in indoor air is an increased lifetime risk of developing lung cancer. The risk from radon exposure is long term and depends on the level of radon, how long a person is exposed and their smoking habits. If you are a smoker and are exposed to elevated levels of radon your risk of developing lung cancer increases significantly.

On average, 16% of lung cancer deaths are attributable to radon exposure in Canada. In 2006, an estimated 1,900 lung cancer deaths in Canada were due to radon exposure. Radon is the 2nd leading cause of lung cancer, after smoking.

Other than lung cancer, there is no evidence that radon exposure causes other harmful health effects such as any other form of cancer, respiratory diseases such as asthma, or symptoms such as persistent coughing or headaches.

Q. I am a smoker. Does radon affect me more than a non-smoker?

A. Yes. The risk from radon exposure for a smoker (including those exposed to second hand smoke) is much greater than for a non-smoker. For example, if you are a lifelong smoker but are not exposed to radon, your risk of getting lung cancer is one in ten. If you add exposure to a high level of radon, your risk becomes one in three. On the other hand, if you are a non-smoker, your lifetime lung cancer risk at the same high radon level is only one in twenty.

Q. Are children more at risk from radon than adults?

A. Children have been reported to be at greater risk than adults for certain types of radiation exposure, but there is currently no conclusive data on whether children are at greater risk than adults from radon.

Q. What about drinking water that contains radon?

A. Research has shown that drinking water that contains radon is far less harmful than breathing radon. When the ground produces radon, it can dissolve and accumulate in water from underground sources, such as wells. When water that contains radon is agitated when used for daily household requirements radon gas escapes from the water and goes into the air. The health risk is not from ingestion but from radon inhalation.

Q. Where in Canada are radon levels the highest?

A. Radon concentrations differ greatly throughout Canada but are usually higher in areas where there is a high concentration of uranium in underlying rock and soil. Radon is found in almost every house, but concentration levels will vary from one house to another, even if they are similar and next door to each other.

Q. How can radon get into my house?

A. A house can act like a vaccum for underground gases. The air pressure inside your house is usually lower than in the soil surrounding the foundation. This difference in pressure is caused by things like the use of air exchangers, exhaust fans and clothes dryers. When air is pushed out of the house, outside air is pulled back in to replace it - much of the replacement air comes from the ground surrounding the house and brings gases such as radon with it.

Radon can enter a house any place it finds an opening where the house contacts the soil: cracks in foundation walls and in floor slabs, construction joints, gaps around service pipes and support posts, floor drains and sumps, cavities inside walls, and the water supply.

The only way to find out if your house has a radon problem is to measure the radon concentration inside it.

Q. What about radon and radioactivity in granite countertops?

Radon is produced from the natural decay of uranium found in rock. Granite used to produce commercial products, such as countertops, can contain varying amounts of uranium. Some granites could contain more natural uranium than others, and thus possibly show higher than expected radiation or radon levels, however, in the vast majority of cases, these levels are not expected to be significant. Health Canada completed a study in February 2010 of 33 types of granite commonly purchased in Canada and none were found to have significant levels of radon.

At this time, Health Canada expects that the main source of radon in a house will be soil gas (containing radon formed by the decay of uranium found in rock under the house) which is drawn inside naturally by differences in pressure between the indoor environment and the outside. Our recommendation is that you reduce your radon risk by first testing the air in your house to determine the radon level.

Q. How do I test my house for radon?

A. The two most common types of radon detectors used for testing houses are short term and long term detectors. The short term detectors are used for a period of 2-7 days, the long term detectors can be used for a period of 1 to 12 months. Since the radon concentration inside a house varies over time, measurements gathered over a longer period of time will give a more accurate indication of the radon level in a house. Health Canada recommends that houses be tested for a minimum of 3 months, ideally between September and April when windows and doors are typically kept closed.

Long-term radon detectors commonly used are:

  • Alpha Track Detection
  • Electret Ion Chamber

There are two options for testing a house for radon: one is to purchase a do-it-yourself radon test kit and the other is to hire a radon measurement professional. If you choose to perform the test yourself radon detectors can be purchased over the phone, from the internet or from some home improvement retailers. The radon test kits will include instructions on how to set up the test and send it back to a lab for analysis once the testing period is over. In some cases the lab analysis fees and postage are additional.

If you choose to hire a service provider to perform the radon test in your house we suggest you ask the following questions:
Questions to consider asking the service provider
Health Canada Recommendations
What type of radon test device do you provide (short term or long term)? Long Term (min. 3 months)
Are you certified/trained to provide radon measurement services? Certified under the Canadian National Radon Proficiency Program (C-NRPP)
Are you familiar with Health Canada's measurement protocolsTable 1 footnote *? Yes

Table 1 footnotes

Table 1 footnote 1

A Guide for Radon Measurements in Residential Dwellings (Homes) is available should you require guidance regarding types of measurement devices, device placement, measurement duration, and the interpretation of measurement results in homes. A separate guide is also available for assessing radon in residential public buildings, such as hospitals, schools and long-term care facilities.

Return to table 1 footnote * referrer

Q. Where in the house or building should I perform the test?

A. To provide a realistic estimate of the radon exposure of the occupants, all measurements should be made in the normal occupancy area of the lowest lived-in level of the house. The normal occupancy area is defined as any area occupied by an individual for more than 4 hours per day.

Potential measurement locations include family rooms, living rooms, dens, playrooms and bedrooms. A lower level bedroom is preferred because people generally spend more time in their bedrooms than in any other room in the house. Similarly, if there are children in the house, lowest level bedrooms or other areas such as a playroom are preferred.

Q. How can I reduce the amount of radon in my house?

A. The most common and effective radon reduction method is Active Soil Depressurisation (ASD); a method where a hole is drilled in your basement floor and a pipe is installed with a fan that draws the radon gas from under your house and pushes it outside. ASD is typically performed by a contractor. If you want to hire a contractor, Health Canada recommends that the contractor be certified from an accredited organization. Health Canada recognizes the Canadian certification program,  Canadian National Radon Proficiency Program (C-NRPP) 1-855-722-6777.

Q. How much will it cost to mitigate my house?

A. The cost of reducing radon in your house depends on how your home was built and the extent of the radon problem. The average radon remediation process, typically done using a contractor, will cost between $1500 - $3000. The cost is much less if a passive system was installed during construction.

Q. Where can I find a contractor for radon mitigation?

A. If you want to hire a contractor, Health Canada recommends that the contractor be certified under the Canadian National Radon Proficiency Program (C-NRPP).

Q. I am building a new house, are there any building codes for radon protection?

The 2010 National Building Code includes requirements that address basic protection from radon exposure such as soil gas barriers and more specific protection from radon a rough-in requirement for a future exhaust system (sub-slab depressurization) should it become necessary, in addition to gravel aggregate and a soil gas barrier under the foundation slab.

Q. I am building a new house, can I have the site tested for radon?

A. Soil testing for radon is not recommended for determining whether a house should be built radon-resistant. Although soil testing can be done, it cannot rule out the possibility that radon could be a problem in the house you build. The 2010 National Building Code revisions included changes to improve protection against radon entry into the house such as a vapor barrier under the foundation slab, and a rough-in requirement for a future radon removal system. These revisions will improve overall indoor air quality and provide a less expensive radon reduction solution should the house have elevated levels of radon.

Q. I don't have a basement. Do I still need to test my house for radon?

A. Radon can get into a house from anywhere that the house is in contact with the ground, regardless or whether your house has a basement, a crawl space or is built slab-on grade.

Q. My house is new/old so it shouldn't have a problem, right?

A. The age of a house is not factor when it comes to whether high levels of radon are present in the dwelling.

Q. I am extending my house. Is there anything I can do to prevent radon entry into the extension?

A. Yes, using the new radon protection codes under the 2010 National Building codes and the advice for found in the publication Reducing Radon Levels in Existing Homes: A Canadian Guide for Professional Contractors.

Q. I am renting a house (apartment) and am concerned about radon. Is my landlord required to test for radon if I ask him to do so?

A. No, there is no legal requirement for a landlord to test a rental property, thus you will have to do it yourself unless your landlord agrees.

Q. I tested my rental house (apartment) and the radon reading was high, is my landlord required to fix this problem?

A. No, the Canadian guideline for radon in indoor air is voluntary, there is no legal requirement for the landlord to remediate to lower the radon level.

Q. As an employer, do I need to test for radon in the workplace?

A. Federal employees are governed by the Canada Labour Code (CLC) which requires the Government of Canada to ensure that its workers are not exposed to high levels of radon. Other workplaces are governed by the Naturally Occurring Radioactive Material Guidelines. There is no legal requirement for employers to test, however, the only way for an employer to know if they are compliant with the CLC or the NORM Guidelines is to test.

Q. Are the radon detectors themselves dangerous or do they contain toxic substances?

A. No. Radon detectors do not pose a health risk.

Q. Where can I learn more?

A. More information on radon can be found on the Web:

Or by contacting Health Canada - Radon or via email at radon@hc-sc.gc.ca

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