Radon 101



Radon Measurements - General

Q. What is radon?

A. Radon is a source of radiation, being 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 soil, rock and groundwater that is under our buildings. Radon gas breaks down further to form radioactive particles called radon “daughters” or "progeny", that can also 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 is rapidly 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 reach high concentrations and become a health risk.

Radon concentrations inside buildings fluctuate seasonally, but are usually higher in winter than in summer. The primary driving force of radon entry into buildings is the pressure differential between the inside and outside of the building that results from the stack-effect, which is always strongest in winter months. In addition, the closing of doors and windows in winter reduces fresh air exchange and allows for radon concentrations to increase.

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

A. The Canadian guideline for radon in indoor air provides Canadians with guidance regarding testing and 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 announce a lowering of the guidelines for acceptable levels of radon in the house from 800 to 200 Bq/m³ in June 2007?

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 associated with levels of radon found in some homes and workplaces. 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.

Q. What is a Becquerel?

A. The becquerel is a metric unit, scientists use to measure the number of radioactive decays of radon atoms. One becquerel corresponds to one nuclear disintegration per second, thus a reading at the Canadian exposure limit of 200 Bq/m³ is 200 nuclear disintegrations per second per cubic meter of air. A higher becquerel value means greater radioactivity and the greater the risk to building occupants. Radon levels are measured in units of becquerels per cubic meter of air (Bq/m³).

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

A. Much information about radon comes from the United States of America (USA) where different radon measurement units are used. In Canada and other countries, the concentration of radon in the air is measured in units of becquerels per cubic meter of air (Bq/m³), whereas the USA uses picocuries per litre of air (pCi/L). Both these units are measurements of radioactive concentration (i.e. radon in air). One pCi/L is equivalent to 37 Bq/m³.

Q. What is Health Canada's reaction to the World Health Organization's (WHO) radon action level of 100 Bq/m³?

A. Health Canada’s response to this question is that Canada's radon guideline is well within the range recommended by the WHO. The WHO's recommended reference level is 100 Bq/m³, with an upper limit of 300 Bq/m³ that should not be exceeded.

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

Note that the WHO recommendation of 100 Bq/m³, as set forth within the “WHO Handbook on Indoor Radon, A Public Health Perspective” indicates a level above 100 Bq/m³ should only be set if the 100 Bq/m³ level “cannot be reached under the prevailing country-specific conditions”.

Since radon is a carcinogen (cancer causing agent) the principal of lowering concentrations to As Low As Reasonably Practicable (ALARA) applies. Individuals and companies are free to choose an action level that is less than Health Canada’s level of 200 Bq/m³.

Q. How can radon affect my health?

A. Radon causes lung cancer and is the leading cause of lung cancer in non-smokers. Estimates suggest 16% of lung cancer and 3,200 deaths in Canada are attributable to radon exposure.

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 higher the radon level the greater the risk of developing lung cancer. Radon gas and radon progeny in the air can be breathed into the lungs where nuclear decay continues to occur, further breaking these substances down into other radioactive elements, primarily forms (isotopes) of polonium, bismuth and lead, which are also referred to as radon progeny or radon daughters. Radon progeny are solid particles and can remain lodged in the lungs. Each time a substance is broken down to become another substance, radiation is released.

Radon and radon progeny emit radiation which damages nearby lung tissue and DNA. This damage can lead to the development of 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, considered cumulatively over that person’s lifetime.

Q. Is there any risk associated with exposure to radon at levels below the Health Canada guideline limit of 200Bq/m³?

A. While the risk of developing lung cancer decreases as the radon levels decrease, there is no level of radon (i.e. radiation) exposure that is considered 100% safe. Lower regulated and/or guideline limits have been set in other jurisdictions, with the US Environmental Protection Agency (EPA) indicating action must be taken at 148 Bq/m³, and the World Health Organization suggesting a lower limit of 100 Bq/m³ as an “acceptable” indoor radon level.

As radon is present in low concentrations in outdoor air, it is not possible to eliminate all human exposure to radon. However, a general principle for controlling exposure to any form of radiation, including radon, is to reduce the levels to which people are exposed to levels As Low As Reasonably Practicable (ALARA).

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 secondhand smoke) is greater than for a non-smoker.

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

A. Children have been reported to be at greater risk than adults for radon exposure. Since radiation damage from radon is cumulative, it is important to reduce radon exposure as soon as possible in one’s life to minimize lifetime risks.

Q. What about drinking water that contains radon?

A. Water from municipal distribution systems tends to have very low radon levels due to treatment processes and retention time. Elevated radon in water tends to be more prevalent in water sourced directly from groundwater wells. When water that contains radon is agitated during daily household usage (e.g. showers, dishwashing, etc.), radon gas escapes from the water and goes into the air. The primary health risk is from inhalation of radon with ingestion being of secondary concern. Therefore, radon exposure control begins with reducing radon in indoor air that comes from soils under a building, followed by reduction of radon in water if overall indoor radon levels have not been adequately reduced.

Q. Where in Canada are radon levels the highest?

A. Radon is found in almost every home and workplace, but concentrations will vary even if buildings are similar and located beside each other. 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. The only way to know the radon levels in a building is to test, and therefore all occupied buildings should be tested. This also supports the need for all new construction to incorporate radon control measures.

Radon Measurements – Commercial, Industrial and Public Buildings

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

A. As per a review of radon law and policy by the Canadian Environmental Law Association [CELA] and CAREX Canada, “General duty clauses in workplace safety legislation require employers to minimize hazards. These clauses are broad enough to include radon, and in no case is radon specifically exempted.” “As in all indoor environments, the only way for an employer to know if they are compliant is to test.” Failure to test and determine if radon levels are above the action level could put employers in a situation where they could be liable if elevated levels of radon are present within the workplace and could give rise to workplace compensation claims as a result of worker exposure to elevated levels of radon.

Federal employees and federally regulated workplaces are governed by the Canada Labour Code (CLC) and the Canadian Occupational Health and Safety Regulations. Part X Section 10.26(4) of the COHSR states “No employee, other than a nuclear energy worker as defined in Section 2 of the Nuclear Safety and Control Act, shall be exposed in the course of any year to a concentration of radon that on average, over the year, is higher than 800 Bq/m³.” It is expected that this regulation will harmonize with Health Canada’s 200 Bq/m³ during Fall 2020. In late 2007, Health Canada began testing radon levels in federal buildings. The purpose of this project was to identify federal workplaces with radon levels above the Canadian Radon Guideline of 200 Bq/m³.

For other workplaces in Ontario, the Ontario Ministry of Labour (MOL) Radon in the Workplace document provides guidance regarding an employer’s responsibility in Ontario related to radon exposure in the workplace. This document indicates the general duty clause of the OHSA (Section 25(2)(h)) is enforceable for the protection of workers “from the hazards associated with radon exposure” in the workplace. The general duty clause states that “an employer must take every precaution reasonable in the circumstances for the protection of a worker”. Determining whether the general duty clause is applicable is at the discretion of the MOL enforcement officer of record involved in any specific inspection/action. As per CAREX, “Workers compensation boards generally do not appear to have clear policies around radon. Ontario is an exception— it explicitly adopts NORM Guidelines and provides information as to employer responsibilities.” (4.3.7 Canadian Environmental Law Association [CELA] and CAREX Canada, Environmental Scan of Radon Law and Policy: Best Practices in Canada and the European Union. August, 2018.)

While there is no legal requirement specifically to test for radon, this implies that employers could still be found to violate the general duty clause if radon levels are found to be elevated within the workplace at any point. As the only way to determine elevated radon levels is to test, it is EACO’s opinion that employers take on significant potential liability if they do not test for radon. Health Canada’s Canadian Guidelines for the Management of Naturally Occurring Radioactive Materials (NORM Guidelines) are specifically considered by the MOL to be the “industry standard for NORM protection in workplaces, and these guidelines indicate that action must be taken when radon levels exceed 200 Bq/m³. The MOL indicates that the requirements of the NORM guidelines may be taken into consideration by MOL enforcement officers; employers are therefore best advised to ensure they are compliant to these requirements.

New Construction and Renovations & Radon

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

A. The 2015 National Building Code, Ontario Building Code and CGSB (CAN/CGSB-149.11-2019) include requirements for radon resistant construction in both residential and commercial buildings. It is recommended you retain a C-NRPP with a CRNCH certification (Controlling Radon in New Canadian Homes) to assist in the design and inspection of the radon control measures. The skill set obtained by a C-NRPP/CRNCH certified individual applies to commercial buildings as well and these individuals can consult with architects and engineers as applicable.

The building code requirements for residential dwellings is Ontario are covered under the Tarion home warranty program for a period of up to 7 years post construction.

Ontario Regulation 332/12 (Building Code), made under the Building Code Act, addresses radon 222 and radon daughter levels within specific geographic locations in section (at the time of publication, these locations are: the City of Elliott Lake, the Township of Faraday and the Township of Hyman).

At the time of this publication the following building authorities had developed specific requirements for radon control measures for new construction:

• Thunder Bay
• City of Guelph
• Central Elgin
• Perth
• City of Kingston
• Loyalist Township

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

A. Soil testing for radon is not recommended for determining whether a building should be built using radon-resistant construction methods. Although soil testing can be done, it cannot rule out the possibility that radon could be a problem in the completed building. A confident correlation between radon concentrations in soils and indoor radon has not been found and a standardized testing method has not been formalized.

It is estimated that costs to conduct the soil testing with any semblance of confidence would cost more than simply including the radon resistant and remediation ready construction methods. Furthermore, building code does not provide an “out” clause for radon resistant and remediation ready construction. Options to not implement radon resistant and remediation ready construction in Ontario building code contradicts current science.

Q. I had my new home tested and radon levels exceeded 200 Bq/m³. Do I have any recourse?

A. If you are the original buyer of a new home in Ontario, you are protected under the Tarion warranty program for a period of seven years beyond the date of construction. If elevated radon levels are detected in the home during this period and you submit a claim to Tarion before the end of the 7-year period, the builder is responsible to remediate the home at their cost (i.e. reduce radon levels below 200 Bq/m³). Note that the testing must be done using a C-NRPP certified radon measurement device, following correct Health Canada measurement protocols. It is strongly recommended to have a 3rd-party EACO member certified as a C-NRPP Radon Measurement Professional perform the testing and prepare a report to ensure the results are defensible and accepted by Tarion.

Radon Mitigation – Commercial, Industrial and Public Buildings

Q. How can I reduce the radon levels within my owned/managed property?

A. It is highly recommended to retain a contractor certified as a Radon Mitigation Professional under the Canadian National Radon Proficiency Program (C-NRPP) for mitigation projects conducted in commercial/industrial/public buildings. A list of appropriately-certified EACO member contractors is available here.

Many building owners/managers also choose to hire an experienced, 3rd-party environmental consultant certified as a C-NRPP Radon Mitigation Professional to assist in the mitigation of their sites. A list of C-NRPP certified EACO member consultants is available here. Certified consultants can assist with any aspect of a radon testing and/or mitigation project, including: development of system designs, arranging for initial “feasibility” or “communications” testing, providing 3rd-party inspection during and after installation of the mitigation system(s), and providing follow-up long-term post mitigation radon testing and reporting. Many such consultants can also assist with development of construction project specifications documents, project tendering, and contract administration and risk communication.

Residential Radon Measurements

Q. How can radon get into a home or workplace?

A. A home or workplace can act like a vacuum for underground gases. The air pressure inside the building is usually lower than in the soil surrounding the foundation. This difference in pressure is caused primarily by stack effect but also by ventilation systems, air exchangers, exhaust fans, appliances, etc. When air is pulled out of the buildings, outdoor air and soil gases (including radon) are pulled in to replace it. Radon can enter anywhere it finds an opening where the building contacts the soil. Examples include cracks in foundation walls and floor slabs, construction joints, gaps around service pipes and support posts, floor drains and sumps, cavities inside walls, and the groundwater supply.

The only way to know the radon levels in a building is to test and all occupied buildings should be tested.

Q. Should I be concerned about radon and radioactivity in granite countertops?

A. 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 home or workplace is from soil gas under the building. It is recommended that the first step be testing the air in the home or workplace to determine the radon level.

Q. How do I test my home or workplace for radon?

A. Radon testing can be done on a short-term or long-term basis, however only long-term measurements are acceptable to determine whether or not radon reduction efforts are required or warranted. Long-term measurements take place over a period of 3 to 12 months. Short-term detectors are typically used for a period of 2-7 days and are used for diagnostic purposes and to confirm that radon reduction measures have worked. Short-term tests must always be followed up by long-term tests.

Since the radon concentration inside a home or workplace varies over time, measurements gathered over a longer period of time will give a more representative indication of the average radon level in a building. Health Canada recommends that homes and workplaces be tested for a minimum of 3 months, ideally during the heating season (October to April) when windows and doors are typically kept closed and radon can accumulate to higher levels.

The most commonly used long-term radon detectors are:

• Alpha Track Detectors
• Electret Ion Chambers
• Continuous Radon Monitors (CRM)

There are two options to test a home or workplace for radon: one is to purchase a do-it-yourself radon test kit and the other is to hire a radon measurement professional.

To ensure testing is done correctly with proper quality control and quality assurance measures, workplaces are advised to retain a C-NRPP certified Radon Measurement Professional. This will ensure the results are defensible and accepted by the workplace health and safety representative or joint health and safety committee.

It is certainly possible to conduct an accurate home test using do-it-yourself radon test kits. To ensure testing is done correctly, thoroughly review the guidance materials available from Health Canada. You should always hire a C-NRPP certified Radon Measurement Professional if you are unsure or are conducting testing for a real-estate transaction or a Tarion home warranty claim.

Consider hiring an EACO member who is a C-NRPP certified Radon Measurement Professional to ensure radon detectors are properly placed, appropriately certified measurement devices are employed, quality assurance and quality control measures are followed, and results are interpreted correctly. Such professionals will be able to explain the meaning of the results on the laboratory report to you in plain English.

Many EACO C-NRPP certified Radon Measurement Professionals either are or have working relationships with EACO C-NRPP certified Radon Mitigation Professionals to be able to assist with mitigation work

A list of EACO members who are certified Radon Measurement Professionals is available here.

Q. How do I ensure I hire the right radon measurement service provider?

If you want to hire a radon measurement or mitigation professional, Health Canada recommends they be certified under the Canadian National Radon Proficiency Program (C-NRPP).

Look for a C-NRPP Measurement Professional to help you with measuring your home or building for radon.

Look for a C-NRPP Mitigation Professional to help you with fixing a home or building which has elevated levels of radon.

EACO members certified under C-NRPP are identified on the EACO website here. Their current certification status can be verified on the C-NRPP Find a Professional list.

Q. What questions should I consider asking a radon measurement service provider?

A. The following are all good questions to ask a radon measurement service provider:

  • What type of radon test device do you use (short-term or long-term)?
    • Health Canada recommends long-term measurements (minimum 91 days duration), or short- term measurements followed by long-term measurements.
    • Long-term measurement devices listed (i.e. certified) for accuracy by C-NRPP can be found at the C-NRPP website. C-NRPP certified Radon Measurement Professionals are required to use C-NRPP certified measurement devices.
  • Are you certified/trained to provide radon measurement services?
    • Health Canada recommends using service providers certified as Radon Measurement Professionals under the Canadian National Radon Proficiency Program (C-NRPP).
  • Are you familiar with and do you follow Health Canada’s measurement protocols?
    • This answer should always be “yes”. Health Canada’s protocols are the definitive protocols in use within Canada. US protocols should not be used for Canadian measurements.
  • What quality control/quality assurance measures do you employ to ensure accurate results?
    • A reputable measurement service provider will adhere to the following QA/QC procedures (all C-NRPP certified Radon Measurement Professionals are required to follow these procedures as a part of their professional certification):
      • Preparation of a radon measurement quality assurance plan
      • Collection of:
        • 1 duplicate sampling device should be deployed and analyzed for every 10 radon sampling devices deployed by the measurement service provider
        • 1 field blank sampling device should be deployed and analyzed for every 20 radon sampling devices deployed by the measurement service provider
  • What laboratory do you use for analysis of test devices (if applicable)?
    • While some devices (e.g. continuous radon monitors) do not require laboratory analysis, most other types of monitors do.
    • Reputable laboratories will perform performance testing of their analytical equipment using spiked radon samples, will analyze laboratory blanks, and will calibrate their analytical equipment regularly.
    • Reputable laboratories will have C-NRPP Certification.

Q. Where in a building should a radon tests be performed?

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

Q. Are there any grants or programs that cover the cost of radon testing or mitigation (repairs)?

A. At the time of publication of this FAQ, we are not aware of any grants to cover the cost of radon testing or mitigation.

If a residential dwelling is within 7 years of age radon mitigation is covered by the builder under the Tarion home warranty program.

Q. My home/workplace is new/old. Will it have high radon?

A. The age of a building is not a factor when it comes to whether high levels of radon are present or not. Older buildings can often have cracks or other penetrations in areas where the building or foundation meets the soil that can allow radon into the home. Conversely, newer buildings constructed using modern building techniques are very airtight which can cause radon concentrations to increase indoors.

Q. I am adding on to an existing building. Is there anything I can do to inhibit radon entry?

A. Yes, use the radon resistant new construction measures established in Canada’s 2015 National Building code, Ontario Building Code and the Canadian General Board Standard (Can/CGSB-149.11-2019). Consider retaining a C-NRPP with a CRNCH certification (Controlling Radon in New Canadian Homes) to assist in the design and inspection of the radon control measures. The skill set obtained by a C-NRPP and/or CRNCH certified individual applies to commercial buildings as well, and these individuals can consult with architects and engineers as applicable.

Q. I have tested my home/ workplace for radon and have received my report, but I’m not sure what to do next?

A. If you review your radon report from the laboratory, you should notice the radon level reported in Bq/m³. This is the average radon level of each test location in your building measured during the testing period. If radon levels are at or above 200 Bq/m³ measures should be taken to reduce radon. Health Canada provides recommendations regarding how soon mitigation should be completed based upon the measured radon level. An individual or company can always choose to use a lower action level or have mitigation performed more quickly, as higher radon concentration and longer periods of exposure elevate lung cancer risk. EACO members who are C-NRPP certified Radon Mitigation Professionals can provide appropriate recommendations regarding mitigation requirements. A list of certified EACO members is provided here.

Health Canada’s Recommended length to mitigate

Less than 200 Bq/m³ – No action required
200 – 600 Bq/m³ – Mitigate the building in less than two years
Above 600 Bq/m³ – Mitigate the building in less than one year

Radon Mitigation in Existing Homes and Workplaces

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

A. The cost for a radon mitigation system can vary significantly depending on building type and Client requirements. As such, contact a C-NRPP certified mitigator for information regarding costs associated with the design and installation of radon mitigation systems.

Q. What sort of reduction in radon levels can be expected as a result of installing a mitigation system?

A. According to a Health Canada Study of 52 homes that had active soil depressurization radon mitigation systems installed, the average reduction in radon levels was 90%. In many cases, even greater reductions are possible.

Consider retaining an EACO member who is a C-NRPP certified Radon Mitigation Professional to conduct an initial review of the building, which may include “feasibility” or “pressure field communication” testing, prior to committing to a full active depressurization radon mitigation system installation. Pressure field communications testing will establish the extent to which air can move through the soil under the building and determine the feasibility of installing an active soil depressurization (ASD) radon remediation system.

Mitigation relying on increased ventilation rates typically has a lower success rate and lower reduction rate. This method can be successful, but also usually carries significant ongoing energy and operational expenses, due to loss of conditioned air and increased wear and tear on ventilation equipment. These systems can also be easily defeated by poor maintenance or interference by occupants, maintenance staff, landlords or outside contractors.

Residential Tenancies & Radon

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 currently no legal requirement for a landlord to test a rental property; you will have to do it yourself unless your landlord agrees to test. It is recommended you work toward an agreement with your landlord if possible. You may need to involve your local property standards office to help resolve the issue.

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 currently no legal requirement for the landlord to remediate to lower the radon level. It is recommended you work toward an agreement with your landlord if possible. You may need to involve your local property standards office to help resolve the issue.


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